Clinical outcomes before and after prucalopride treatment: an observational study in patients with chronic idiopathic constipation in the USA

INTRODUCTION

This real-world US-based claims study compared constipation-related symptoms and complications 6 months before and after prucalopride initiation in adults with chronic idiopathic constipation (CIC).

METHODS

This observational, retrospective cohort analysis used the IBM MarketScan® Commercial Claims and Encounters and the Medicare Supplemental databases (January 2015-June 2020). Prucalopride-treated patients (≥18 years old) who had ≥1 constipation-related International Classification of Diseases, Tenth Revision, Clinical Modification (ICD-10-CM) diagnosis code during the baseline or study period were included. The proportions of patients with constipation-related symptoms (abdominal pain, abdominal distension [gaseous], incomplete defecation, and nausea) and constipation-related complications (anal fissure and fistula, intestinal obstruction, rectal prolapse, hemorrhoids, perianal venous thrombosis, peri-anal/peri-rectal abscess, and rectal bleeding) were examined. Constipation-related symptoms and complications were identified using ICD-10-CM, ICD-10-Procedure Coding System, or Current Procedural Terminology codes. Data were stratified by age (overall, 18-64 years, ≥65 years).

RESULTS

This study included 690 patients: mean (standard deviation) patient age was 48.0 (14.7) years and 87.5% were women. The proportions of patients overall with constipation-related symptoms decreased 6 months after prucalopride initiation (abdominal pain [50.4% vs 33.3%, P<0.001]; abdominal distension [gaseous] [23.9% vs 13.3%, P<0.001]; and nausea [22.6% vs 17.7%, P<0.01]; no improvements observed for incomplete defecation). Similarly, the proportions of patients overall with constipation-related complications decreased 6 months after prucalopride initiation (intestinal obstruction [4.9% vs 2.0%, P<0.001]; hemorrhoids [10.7% vs 7.0%, P<0.05]; and rectal bleeding [4.1% vs 1.7%, P<0.05]).

DISCUSSION

This study suggests that prucalopride may be associated with improved constipation-related symptoms and complications 6 months after treatment initiation.

Journey to anticoagulant access following payer rejection of apixaban

OBJECTIVES

To investigate the journey to oral anticoagulant (OAC) access following formulary-related rejection of apixaban (Eliquis) and evaluate characteristics associated with failure to achieve OAC access among patients with atrial fibrillation (AF).

STUDY DESIGN

Retrospective study using the Optum Market Clarity Data from January 2016 through February 2020.

METHODS

Patients had at least 1 claim rejection for apixaban due to prior authorization (PA), formulary exclusion (FE), or quantity limit (QL) and at least 1 AF diagnosis on or before the rejected claim. Descriptive statistics summarized transaction journeys by type of formulary restriction. Multivariable regression assessed patient characteristics associated with not receiving an OAC within 60 days after initial rejection.

RESULTS

Among 18,434 patients in the analytic sample, QL was the most common reason for rejection (68.7%), followed by PA (21.2%) and FE (10.2%). Most patients received a paid OAC claim within 60 days after rejection (82.2%-85.5% across restriction types). Mean time from rejection to paid claim ranged from 5.2 to 10.7 days among patients with a paid OAC claim and 12.4 to 17.6 days among those with multiple attempts before OAC receipt. Characteristics associated with higher odds of not receiving OAC treatment included being male, beingAfrican American, having Medicaid coverage, possessing a high stroke risk score, exhibiting no evidence of prior apixaban treatment, and being prescribed a low dose of apixaban on the initial rejected claim.

CONCLUSIONS

Most patients with a claim rejection for apixaban received approval for apixaban within 60 days, suggesting that initial rejection merely created a delay in treatment. Vulnerable populations were at greater risk of not receiving a paid OAC claim.

Payer formulary tier increases of apixaban: how patients respond and potential implications

OBJECTIVE

To assess potential impacts of formulary tier increases of apixaban-an efficacious oral anticoagulant (OAC) for preventing stroke in patients with atrial fibrillation (AF)-on patients' prescription drug plan (PDP) switching and OAC treatment patterns.

METHODS

Nationwide claims data for Medicare beneficiaries with Parts A, B, and D (100% sample) were used to assess apixaban-treated AF patients who faced a formulary tier increase for apixaban in 2017 by their Part D PDP. Patients' out-of-pocket (OOP) costs for apixaban were described, along with PDP switching and OAC treatment patterns.

RESULTS

Among 1845 included patients, 97.7% had apixaban on tier 3 of their plan's formulary in 2016 and faced its increase to tier 4 for 2017. Approximately 4% (N = 81) of patients pre-emptively switched to a different PDP for 2017 with almost all switching to plans with apixaban on a lower formulary tier and 85.2% continuing apixaban treatment. Among the 96% (N = 1764) of patients who remained on the same PDP for 2017, over half (57.5%) continued apixaban treatment, despite increased OOP costs ($54 vs. $135 for a 30-day supply in 2016 vs. 2017). Only 12.4% of those who remained on the same plan for 2017 switched to another OAC, while as much as 30.1% discontinued OACs. These discontinuers exhibited higher comorbidity burdens than patients continuing on any OAC.

CONCLUSION

The majority of patients continued on apixaban despite higher OOP cost, suggesting patients' reluctance to change treatment for non-medical reasons; however, 30% of patients discontinued OAC treatment after higher apixaban tier placement.

Safety differences across androgen receptor inhibitors in nonmetastatic castration-resistant prostate cancer

Approval of apalutamide, enzalutamide and darolutamide has transformed the treatment landscape and guideline recommendations for patients with nonmetastatic castration-resistant prostate cancer but now raises the issue of decision-making regarding treatment selection. In this commentary, we discuss the efficacy and safety of these second-generation androgen receptor inhibitors and propose that for patients with nonmetastatic castration-resistant prostate cancer, safety considerations for these treatments are especially important. We examine these considerations in the context of patient and caregiver preferences as well as patient clinical characteristics. We further posit that consideration of treatments' safety profiles should include not only the initial direct impacts from potential treatment-emergent adverse events and drug-drug interaction events, but also the full cascade of potentially avoidable healthcare complications.

Payer formulary exclusions of apixaban: how patients respond and potential implications

In recent years, US payers have increased usage of formulary exclusions as a means to help manage costs. Earlier this year, one of the largest pharmacy benefit managers in the country added Eliquis (apixaban), the most widely used anticoagulant, to its list of excluded medicines from its formulary, raising concerns by physicians and patients. In this commentary, we examine the potential impacts of formulary exclusion of a drug like apixaban-a treatment for patients with atrial fibrillation and venous thromboembolism to help prevent stroke and clotting events and which has been demonstrated to have a strong efficacy and safety profile. We discuss the effect of formulary exclusions on patients' ability to access the most clinically appropriate treatment for their health needs, along with possible effects on their health and well-being. We also report descriptive results on apixaban-treated patients with traditional Medicare coverage who faced a formulary exclusion of apixaban in 2017, and these patients' observed behaviors. We found that the majority of these patients remained on apixaban either through pre-emptively switching to a different Part D drug plan with apixaban coverage or applying for formulary exception. Our findings suggest that formulary exclusion did not help to achieve the goal of switching patients to less costly medications but created additional hurdles for patients to access their preferred treatment and increased patient burden. Alternative ways to manage payer costs may be needed to help avoid poor outcomes and reduce the burden placed on patients in their efforts to access life-saving medications.

Patterns of Daily Motor-Symptom Control with Carbidopa/Levodopa Enteral Suspension Versus Oral Carbidopa/Levodopa Therapy in Advanced Parkinson's Disease: Clinical Trial Post Hoc Analyses

Introduction

A clinical trial in advanced Parkinson’s disease (APD) has established the superiority of carbidopa/levodopa enteral suspension (CLES) in reducing total patient “off” time (OFF) and increasing total “on” time without troublesome dyskinesia (ON-woTD) over orally administered immediate-release carbidopa/levodopa tablets (IR–CL). However, temporal patterns of these improvements throughout the waking day have not been examined. In this analysis, time to ON-woTD after waking and patterns of motor-symptom control throughout the waking day were compared between CLES and IR–CL.

Methods

Post hoc analyses of APD patient-diary data from the phase 3 randomized controlled trial were used to compare changes in time to ON-woTD after waking, motor-symptom control throughout the waking day, occurrence of extreme fluctuations between OFF and “on” with troublesome dyskinesia, and motor-state transitions with CLES versus IR–CL from baseline to week 12.

Results

The sample included 33 CLES-treated and 30 IR–CL-treated patients. Among the CLES group, the percentage of patient days achieving ON-woTD within 30 min of waking was three times higher at week 12 versus baseline (33% vs. 11%, p = 0.0043); no significant change occurred with IR–CL. When the waking day was divided into four 4-h periods, CLES versus IR–CL treatment produced significantly greater reductions in OFF during three periods, and two periods had increased ON-woTD. Fewer CLES-treated patients had extreme fluctuations at week 12 (3% vs. 23%, p = 0.0224) compared to IR–CL-treated patients. From baseline to week 12, CLES-treated patients had greater reductions in the average number of motor-state transitions compared to IR–CL-treated patients (− 1.6, p = 0.0295).

Conclusion

CLES-treated patients experienced a more rapid onset of ON-woTD after waking and greater consistency of ON-woTD throughout their waking day than IR–CL-treated patients.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40120-022-00332-0.

In advanced Parkinson’s disease, patients’ motor-symptom states (such as “on” time without troublesome dyskinesia [good “on” time] and “off” time), and the timing at which they occur, can impact patients’ quality of life and ability to complete activities of daily living. Carbidopa/levodopa enteral suspension is administered continuously into the jejunum, potentially reducing some of the motor-state variation that is common with orally administered carbidopa/levodopa, including delayed “on” time after waking and transitions between “off” and “on” throughout the day. In post hoc analyses of clinical trial data, patterns of motor-states across the waking day were compared between carbidopa/levodopa enteral suspension and orally administered immediate-release carbidopa/levodopa at week 12. Outcomes included time to good “on” after waking; occurrence of extreme fluctuations between “off” time and “on” time with troublesome dyskinesia; time in each motor-state during 4-h intervals across the day; and frequency of motor-state transitions. Three times as many carbidopa/levodopa enteral suspension-treated patients achieved good “on” within 30 min of waking after 12 weeks versus baseline, whereas no significant change was observed for the orally administered immediate-release carbidopa/levodopa group. Compared to orally administered immediate-release carbidopa/levodopa-treated patients, fewer carbidopa/levodopa enteral suspension-treated patients experienced extreme fluctuations, had greater reductions in motor-state transitions, and greater reductions in duration of “off” during three of the four intervals in the day. These findings provide a first look at the impact of carbidopa/levodopa enteral suspension on motor-state patterns throughout the day, and suggest that carbidopa/levodopa enteral suspension provides more consistent motor-symptom control and predictable benefit throughout the day than orally administered carbidopa/levodopa.

The Hospitalization-Related Costs of Adverse Events for Novel Androgen Receptor Inhibitors in Non-Metastatic Castration-Resistant Prostate Cancer: An Indirect Comparison

INTRODUCTION

Three novel androgen receptor inhibitors are approved in the USA for the treatment of non-metastatic castration-resistant prostate cancer (nmCRPC): apalutamide, enzalutamide, and darolutamide. All three therapies have demonstrated prolonged metastasis-free survival in their respective phase III trials, with differing safety profiles. The objective of this study was to compare the mean per-patient costs of all-cause adverse events (AEs) requiring hospitalization between darolutamide versus apalutamide and enzalutamide for nmCRPC in the USA.

METHODS

All-cause grade ≥ 3 AEs with corresponding any-grade AEs reported among at least 10% of patients in any arm of the ARAMIS (darolutamide), SPARTAN (apalutamide), and PROSPER (enzalutamide) trials were selected for inclusion in the primary analyses. After matching-adjusted indirect comparison, AE costs were calculated by multiplying the AE rates from the trials by their respective unit costs of hospitalization taken from the US Healthcare Cost and Utilization Project (HCUP) database. Sensitivity analyses which further included any-grade AEs reported among at least 5% of patients were also performed.

RESULTS

After reweighting and adjusting for the trials' placebo arms, the mean per-patient AE costs were $1021 and $387 lower for darolutamide than for apalutamide and enzalutamide, respectively, over the trials' duration (SPARTAN and PROSPER, 43 months; ARAMIS, 48 months). For darolutamide vs. apalutamide, the largest drivers of the per-patient cost differences were fracture (adjusted difference $416), hypertension ($143), and rash ($219); for darolutamide vs. enzalutamide, they were fatigue not including asthenia ($290) and hypertension including increased blood pressure (i.e., any AE of hypertension or with elevated blood pressure not yet classified as hypertension) ($60). The results of the sensitivity analyses were consistent with the primary results.

CONCLUSIONS

Patients with nmCRPC treated with darolutamide in ARAMIS incurred lower AE-related costs (USD), as determined using HCUP costing data, compared with patients treated with either apalutamide (in SPARTAN) or enzalutamide (in PROSPER).

Safety outcomes of darolutamide versus apalutamide and enzalutamide in nonmetastatic castration-resistant prostate cancer (nmCRPC): Matching-adjusted indirect comparisons

5561

Background: Randomized nmCRPC trials comparing darolutamide (D), apalutamide (A) and enzalutamide (E) have not been reported. Safety of these therapeutics has important implications in assessing patient risk-benefit concerns. Matching-adjusted indirect comparison (MAIC) is a method to perform indirect treatment comparisons adjusting for cross-trial heterogeneity. Objective: To compare the safety outcomes of D vs. A or E using MAIC. Methods: Data from the ARAMIS (D vs. placebo [PBO]), SPARTAN (A vs. PBO) and PROSPER (E vs. PBO) trials were used. Key safety outcomes including adverse events (AEs) that have central nervous system relevance were compared using anchored MAIC. Individual patient level data (IPD) from ARAMIS were selected and re-weighted to match the inclusion criteria and baseline characteristics published in SPARTAN and PROSPER (no access to their IPD). The Benjamini-Hochberg approach was applied to adjust for multiplicity. The D vs A MAIC matched on 7 covariates: age, prostate-specific antigen (PSA) level and doubling time, Eastern Cooperative Oncology Group (ECOG), Gleason score, bone-sparing agent use and prior surgery. Sensitivity analyses were conducted matching on different sets of covariates. D vs. E were matched on age, region, PSA level and doubling time, ECOG, Gleason score and bone-sparing agent use. Risk difference (RD) ([DARO – PBOARAMIS] – [ENZA – PBOPROSPER]) and odds ratio (OR) (ORARAMIS/ORPROSPER) were calculated. RD<0 or OR<1 indicate lower AE risk for D. Results: For D vs. A, the effective sample sizes (ESS) of D and its placebo (PBO) arm were 604 and 391 after matching. Fall, fracture, and rash were statistically significantly lower for D vs. A (Table). For D vs. E, the ESS of D and PBO arm were 580 and 395, respectively. Fall, dizziness, mental impairment, hypertension, fatigue and severe fatigue were statistically significantly lower for D vs. E. Conclusions: After adjusting for trial differences, D showed favorable safety profile in fall, dizziness, mental-impairment, hypertension, rash, fatigue, and fracture. [Table: see text]

Dupilumab Versus Cyclosporine for the Treatment of Moderate-to-Severe Atopic Dermatitis in Adults: Indirect Comparison Using the Eczema Area and Severity Index

Dupilumab is approved for uncontrolled moderate-to-severe atopic dermatitis (AD); cyclosporine is approved for severe AD for ≤ 1 year. The efficacy/effectiveness of these treat-ments was compared indirectly. Regression models used pooled patient-level data to estimate response (Eczema Area and Severity Index (EASI) EASI-50/EASI-75 at weeks 12-16 and 24-30) to dupilumab 300 mg every 2 weeks (CHRONOS [NCT02260986]) or cyclosporine (University Medical Center). Models were adjusted for sex, baseline EASI, and thymus and activation-regulated chemokine level. A total of 106 patients received dupilumab (+ topical cortico-steroids; + TCS), and 57 received cyclosporine (+ TCS). Among University Medical Center patients, estimated EASI-50 responders were, dupilumab vs. cyclosporine, 91% vs. 77% (p = 0.038; weeks 12-16), and 96% vs. 67% (p < 0.0001; weeks 24-30); EASI-75 responders were 78% vs. 56% (p = 0.016; weeks 12-16) and 80% vs. 47% (p <0.001; weeks 24-30). Among CHRONOS patients, estimated EASI-50 responders were 90% vs. 74% (p <0.038; weeks 12-16) and 92% vs. 53% (p < 0.0001; weeks 24-30); EASI-75 responders were 75% vs. 52% (p = 0.016; weeks 12-16) and 74% vs. 40% (p <0.001; weeks 24-30), respectively. These results suggest a higher relative efficacy of dupilumab vs. cyclosporine.

The burden of tardive dyskinesia secondary to antipsychotic medication use among patients with mental disorders

Objective: To assess the impact of developing tardive dyskinesia (TD), both with and without other pre-existing extrapyramidal symptoms (EPS), on healthcare resource utilization (HRU) among patients with mental disorders receiving antipsychotic medications. Methods: Data on patients receiving antipsychotics who had schizophrenia, major depressive disorder or bipolar disorder were extracted from a Medicaid claims database. Separate cohorts of TD patients with and without other EPS ("TD + EPS" and "TD non-EPS") were constructed and matched to patients in a non-TD/EPS control cohort at a ∼1:5 ratio. HRU outcomes were assessed using descriptive statistics and difference-in-differences techniques over baseline and follow-up periods defined as the 6 months before and after TD development, respectively. Results: The TD + EPS (n = 289) and TD non-EPS (n = 394) cohorts were matched with 1398 and 1922 control patients, respectively. The percentage of patients with all-cause and mental-disorder-related inpatient admissions increased from baseline to follow-up in the TD + EPS (12.8% and 12.5%, respectively) and TD non-EPS (16.0% and 13.5%) cohorts; by contrast, slight decreases (∼3%) in these outcomes were observed in the matched controls. Difference-in-differences analyses demonstrated that development of TD was associated with a statistically significant increase of ∼15-19% in the percentage of patients with all-cause and mental-disorder-related inpatient admissions/visits. The within-cohort change from baseline to follow-up in the use of potential drugs for TD or EPS was similar between the TD cohorts and their matched controls. Conclusions: This study demonstrates a significant economic burden associated with developing TD, as captured by increased HRU including inpatient admissions and ER visits.

Drivers of treatment patterns in patients with chronic lymphocytic leukemia stopping ibrutinib or idelalisib therapies

Novel therapies including kinase inhibitors (KI) have led to high and durable response in patients with chronic lymphocytic leukemia (CLL), however, some patients stop therapy. This study evaluates reasons for treatment changes among CLL patients who stopped KI in real-world practice. Sixty-nine US oncologists/hematologists provided patient-level data abstracted from charts of CLL adult patients who initiated a KI and later (1) switched to another anti-neoplastic regimen (Switched cohort), (2) discontinued the KI and remained untreated (Discontinued cohort), or (3) restarted the same KI after an interruption of ≥60 days (Restarted cohort). Demographics, clinical/treatment characteristics, and reasons for stopping, restarting, and switching the KI therapy were described. In the Switched cohort, reasons for stopping included disease progression (72.5%), low/no disease activity (3.9%), adverse event [AE]/ intolerance/comorbidity (15.7%), and planned cellular therapies (7.9%). In the Discontinued cohort, approximately half (46.0%) of patients stopped KI therapy because they were terminally ill/died, or were moved to best supportive care - these patients were older, had more severe disease, and high comorbidity burden. The other half (54.0% of patients) stopped due to low/no disease activity (24.0%), AEs/toxicity (12.0%), or patient-requested drug holiday (18.0%). In the Restarted cohort, the most common reasons for stopping KIs were patient request (37.3%), AEs/intolerance (31.4%), and economic reasons (10%). Patients restarted when disease progressed (60.8%) or when they recovered from the AE (33%). Reasons for KI stop and subsequent treatment patterns were varied and multifactorial, suggesting heterogeneous disease management and a need for more evidence around supporting strategies and physician education.

Inpatient Admissions and Costs Associated with Persistent Use of Dalfampridine Extended-Release in Multiple Sclerosis: A Claims Database Analysis

BACKGROUND

While the clinical benefits of dalfampridine extended-release (D-ER) have been established in patients with multiple sclerosis (MS) through multiple clinical trials, there is limited real-world data on D-ER use, in particular the persistent use of D-ER, and associated acute care resource utilization and costs.

OBJECTIVE

To examine the real-world association of D-ER use and inpatient admissions and costs among patients with MS.

METHODS

This study was a retrospective observational claims analysis of the MarketScan database (April 2009-March 2014). Eligible patients consisted of adult enrollees aged 18-64 years who had (a) 12 months of continuous private plan enrollment preceding (baseline) and following (follow-up) the first D-ER claim; (b) ≥ 2 MS diagnosis codes with ≥ 1 during the baseline period; (c) ≥ 2 consecutive D-ER claims; and (d) no alternate gait-impairing etiologies during the baseline and follow-up periods. Patients were separated into 2 D-ER cohorts in the main analysis: persistent (≥ 360 days of D-ER supply) and nonpersistent (< 360 days of supply) users. Sensitivity analyses were conducted, examining additional breakdowns of days of supply within the nonpersistent cohort. Inpatient admissions (all-cause and MS-related) and health care expenditures were calculated and compared between the cohorts during follow-up using Wilcoxon rank-sum and chi-square tests. Regression models were conducted, controlling for age, sex, MS relapses, comorbidities, disease-modifying therapy use, and other baseline factors, including inpatient admissions and costs.

RESULTS

Of 1,598 eligible patients, 719 (45.0%) were persistent D-ER users, and 879 (55.0%) were nonpersistent D-ER users. The 2 cohorts had similar demographic and clinical characteristics, with mean (SD) ages of 51.0 (8.4) and 50.6 (8.6) years and were 71.3% and 66.6% female, respectively. Compared with nonpersistent D-ER use, persistent D-ER use was associated with lower odds of all-cause inpatient admissions (OR = 0.58, P = 0.010) and MS-related inpatient admissions (OR = 0.50, P = 0.004). Persistent use was also associated with lower inpatient expenditures for all-cause admissions ($669 vs. $1,515, P = 0.002) and MS-related admissions ($388 vs. $891, P = 0.008).

CONCLUSIONS

Persistent D-ER use was associated with significantly lower rates of all-cause and MS-related inpatient admissions and costs.

DISCLOSURES

Funding for this research and medical writing assistance was provided by Acorda Therapeutics. The study sponsor was involved in all stages of the study research and manuscript preparation. Guo and Niyazov were employees of Acorda Therapeutics at the time of this study and may own stock/stock options. Wu, Macaulay, Terasawa, and Schmerold are employees of Analysis Group, which received consultancy fees from Acorda Therapeutics for this project. Krieger was a consultant for Acorda Therapeutics for this project and has the following additional financial interests to report: consulting/advisory board work with Bayer, Biogen, EMD Serono, Novartis, Genentech, Genzyme, and Teva. Study concept and design were contributed by Guo, Niyazov, Macaulay, and Wu. Macaulay, Terasawa, Schmerold, and Wu helped prepare the data, and data interpretation was performed by Krieger, Guo, Niyazov, and Macaulay, along with Terasawa and Wu. The manuscript was written by Terasawa and Schmerold, along with Macaulay, and revised by all the authors. A portion of the current research was presented in poster format at the 2106 American Academy of Neurology Annual Meeting, which took place in Vancouver, BC, Canada, on April 15-21, 2016.

Ovarian regulation of kisspeptin neurones in the arcuate nucleus of the rhesus monkey (macaca mulatta)

Tonic gonadotrophin secretion throughout the menstrual cycle is regulated by the negative-feedback actions of ovarian oestradiol (E₂) and progesterone. Although kisspeptin neurones in the arcuate nucleus (ARC) of the hypothalamus appear to play a major role in mediating these feedback actions of the steroids in nonprimate species, this issue has been less well studied in the monkey. In the present study, we used immunohistochemistry and in situ hybridisation to examine kisspeptin and KISS1 expression, respectively, in the mediobasal hypothalamus (MBH) of adult ovariectomised (OVX) rhesus monkeys. We also examined kisspeptin expression in the MBH of ovarian intact females, and the effect of E₂, progesterone and E₂ + progesterone replacement on KISS1 expression in OVX animals. Kisspeptin or KISS1 expressing neurones and pronounced kisspeptin fibres were readily identified throughout the ARC of ovariectomised monkeys but, on the other hand, in intact animals, kisspeptin cell bodies were small in size and number and only fine fibres were observed. Replacement of OVX monkeys with physiological levels of E₂, either alone or with luteal phase levels of progesterone, abolished KISS1 expression in the ARC. Interestingly, progesterone replacement alone for 14 days also resulted in a significant down-regulation of KISS1 expression. These findings support the view that, in primates, as in rodents and sheep, kisspeptin signalling in ARC neurones appears to play an important role in mediating the negative-feedback action of E₂ on gonadotrophin secretion, and also indicate the need to study further their regulation by progesterone.

Rapid direct action of estradiol in GnRH neurons: findings and implications

Estradiol plays a pivotal role in the control of gonadotropin-releasing hormone (GnRH) neuronal function and female reproduction. While positive and negative feedback actions of estradiol that enhance and suppress release of GnRH and LH are primarily mediated through estrogen receptor alpha located in interneurons, a series of recent studies in our laboratory indicate that rapid excitatory actions of estradiol also directly modify GnRH neuronal activity. We observed this phenomenon in cultured primate GnRH neurons, but similar rapid direct actions of estradiol are also described in cultured GnRH neurons and green fluorescent protein-labeled GnRH neurons of mice. Importantly, rapid direct action of estradiol in GnRH neurons is mediated through membrane or membrane associated receptors, such as GPR30, STX-sensitive receptors, and ERβ. In this review, possible implications of this rapid estradiol action in GnRH neurons are discussed.

STX, a novel nonsteroidal estrogenic compound, induces rapid action in primate GnRH neuronal calcium dynamics and peptide release

Previously, we reported that 1 nM 17ß-estradiol (E(2)) induces a rapid action, which is, in part, mediated through the G protein-coupled receptor GPR30 in primate GnRH neurons. Because it has been reported that the diphenylacrylamide compound, STX, causes estrogenic action in the mouse and guinea pig hypothalamus, the present study examined effects of STX in primate GnRH neurons and whether there is an action independent of GPR30. Results are summarized as follows. STX (10 nM) exposure increased 1) the oscillation frequency of intracellular calcium concentration ([Ca(2+)](i)), 2) the percentage of cells stimulated, and 3) the synchronization frequency of [Ca(2+)](i) oscillations. STX (10-100 nM) also stimulated GnRH release. The effects of STX on both [Ca(2+)](i) oscillations and GnRH release were similar to those caused by E(2) (1 nM), although with less magnitude. STX (10 nM)-induced changes in [Ca(2+)](i) oscillations were not altered by GPR30 small interfering RNA transfection, indicating that STX-sensitive receptors differ from GPR30. Finally, a higher dose of E(2) (10 nM) induced a larger change in [Ca(2+)](i) oscillations than that with a smaller dose of E(2) (1 nM), and the effects of 10 nM E(2) were reduced but not completely blocked by GPR30 small interfering RNA transfection, indicating that the effects of 10 nM E(2) in primate GnRH neurons are mediated by multiple membrane receptors, including GPR30 and STX-sensitive receptors. Collectively, the rapid action of E(2) mediated through GPR30 differs from that mediated through STX-sensitive receptors. The molecular structure of the STX-sensitive receptor remains to be identified.

Rapid action of estradiol in primate GnRH neurons: the role of estrogen receptor alpha and estrogen receptor beta

Estrogens play a pivotal role in the control of female reproductive function. Recent studies using primate GnRH neurons derived from embryonic nasal placode indicate that 17β-estradiol (E(2)) causes a rapid stimulatory action. E(2) (1nM) stimulates firing activity and intracellular calcium ([Ca(2+)](i)) oscillations of primate GnRH neurons within a few min. E(2) also stimulates GnRH release within 10min. However, the classical estrogen receptors, ERα and ERβ, do not appear to play a role in E(2)-induced [Ca(2+)](i) oscillations or GnRH release, as the estrogen receptor antagonist, ICI 182,780, failed to block these responses. Rather, this rapid E(2) action is, at least in part, mediated by a G-protein coupled receptor GPR30. In the present study we further investigate the role of ERα and ERβ in the rapid action of E(2) by knocking down cellular ERα and ERβ by transfection of GnRH neurons with specific siRNA for rhesus monkey ERα and ERβ. Results indicate that cellular knockdown of ERα and ERβ failed to block the E(2)-induced changes in [Ca(2+)](i) oscillations. It is concluded that neither ERα nor ERβ is required for the rapid action of E(2) in primate GnRH neurons.

Recent discoveries on the control of gonadotrophin-releasing hormone neurones in nonhuman primates

Since Ernst Knobil proposed the concept of the gonadotrophin-releasing hormone (GnRH) pulse-generator in the monkey hypothalamus three decades ago, we have made significant progress in this research area with cellular and molecular approaches. First, an increase in pulsatile GnRH release triggers the onset of puberty. However, the question of what triggers the pubertal increase in GnRH is still unclear. GnRH neurones are already mature before puberty but GnRH release is suppressed by a tonic GABA inhibition. Our recent work indicates that blocking endogenous GABA inhibition with the GABA(A) receptor blocker, bicuculline, dramatically increases kisspeptin release, which plays an important role in the pubertal increase in GnRH release. Thus, an interplay between the GABA, kisspeptin, and GnRH neuronal systems appears to trigger puberty. Second, cultured GnRH neurones derived from the olfactory placode of monkey embryos exhibit synchronised intracellular calcium, [Ca(2+)](i), oscillations and release GnRH in pulses at approximately 60-min intervals after 14 days in vitro (div). During the first 14 div, GnRH neurones undergo maturational changes from no [Ca(2+)](i) oscillations and little GnRH release to the fully functional state. Recent work also shows GnRH mRNA expression increases during in vitro maturation. This mRNA increase coincides with significant demethylation of a CpG island in the GnRH 5'-promoter region. This suggests that epigenetic differentiation occurs during GnRH neuronal maturation. Third, oestradiol causes rapid, direct, excitatory action in GnRH neurones and this action of oestradiol appears to be mediated through a membrane receptor, such as G-protein coupled receptor 30.

Rapid action of oestrogen in luteinising hormone-releasing hormone neurones: the role of GPR30

Previously, we have shown that 17beta-oestradiol (E(2)) induces an increase in firing activity and modifies the pattern of intracellular calcium ([Ca(2+)](i)) oscillations with a latency < 1 min in primate luteinising hormone-releasing hormone (LHRH) neurones. A recent study also indicates that E(2), the nuclear membrane impermeable oestrogen, oestrogen-dendrimer conjugate, and the plasma membrane impermeable oestrogen, E(2)-BSA conjugate, all similarly stimulated LHRH release within 10 min of exposure in primate LHRH neurones, indicating that the rapid action of E(2) is caused by membrane signalling. The results from a series of studies further suggest that the rapid action of E(2) in primate LHRH neurones appears to be mediated by GPR30. Although the oestrogen receptor antagonist, ICI 182, 780, neither blocked the E(2)-induced LHRH release nor the E(2)-induced changes in [Ca(2+)](i) oscillations, E(2) application to cells treated with pertussis toxin failed to result in these changes in primate LHRH neurones. Moreover, knockdown of GPR30 in primate LHRH neurones by transfection with human small interference RNA for GPR30 completely abrogated the E(2)-induced changes in [Ca(2+)](i) oscillations, whereas transfection with control siRNA did not. Finally, the GPR30 agonist, G1, resulted in changes in [Ca(2+)](i) oscillations similar to those observed with E(2). In this review, we discuss the possible role of G-protein coupled receptors in the rapid action of oestrogen in neuronal cells.

Estrogen receptor-alpha immunoreactive neurons in the brainstem and spinal cord of the female rhesus monkey: species-specific characteristics

The distribution pattern of estrogen receptors in the rodent CNS has been reported extensively, but mapping of estrogen receptors in primates is incomplete. In this study we describe the distribution of estrogen receptor alpha immunoreactive (ER-alpha IR) neurons in the brainstem and spinal cord of the rhesus monkey. In the midbrain, ER-alpha IR neurons were located in the periaqueductal gray, especially the caudal ventrolateral part, the adjacent tegmentum, peripeduncular nucleus, and pretectal nucleus. A few ER-alpha IR neurons were found in the lateral parabrachial nucleus, lateral pontine tegmentum, and pontine gray medial to the locus coeruleus. At caudal medullary levels, ER-alpha IR neurons were present in the commissural nucleus of the solitary complex and the caudal spinal trigeminal nucleus. The remaining regions of the brainstem were devoid of ER-alpha IR neurons. Spinal ER-alpha IR neurons were found in laminae I-V, and area X, and were most numerous in lower lumbar and sacral segments. The lateral collateral pathway and dorsal commissural nuclei of the sacral cord and the thoracic intermediolateral cell column also contained ER-alpha IR neurons. Estrogen treatment did not result in any differences in the distribution pattern of ER-alpha IR neurons. The results indicate that ER-alpha IR neurons in the primate brainstem and spinal cord are concentrated mainly in regions involved in sensory and autonomic processing. Compared with rodent species, the regional distribution of ER-alpha IR neurons is less widespread, and ER-alpha IR neurons in regions such as the spinal dorsal horn and caudal spinal trigeminal nucleus appear to be less abundant. These distinctions suggest a modest role of ER-alpha in estrogen-mediated actions on primate brainstem and spinal systems. These differences may contribute to variations in behavioral effects of estrogen between primate and rodent species.

Gonadotrophin-releasing hormone (GnRH) release in marmosets I: in vivo measurement in ovary-intact and ovariectomised females

In vivo hypothalamic gonadotrophin-releasing hormone (GnRH) release was characterised for the first time in a New World primate. A nonterminal and repeatable push-pull perfusion (PPP) technique reliably measured GnRH in conscious common marmoset monkeys. Nineteen adult females (n = 8 ovary-intact in the mid-follicular phase; n = 11 ovariectomised) were fitted with long-term cranial pedestals, and a push-pull cannula was temporarily placed in unique locations within the pituitary stalk-median eminence (S-ME) 2 days prior to each PPP session. Marmosets underwent 1-3 PPPs (32 PPPs in total) lasting up to 12 h. Plasma cortisol levels were not elevated in these habituated marmosets during PPP, and PPP did not disrupt ovulatory cyclicity or subsequent fertility in ovary-intact females. GnRH displayed an organised pattern of release, with pulses occurring every 50.0 +/- 2.6 min and lasting 25.4 +/- 1.3 min. GnRH pulse frequency was consistent within individual marmosets across multiple PPPs. GnRH mean concentration, baseline concentration and pulse amplitude varied predictably with anatomical location of the cannula tip within the S-ME. GnRH release increased characteristically in response to a norepinephrine infusion and decreased abruptly during the evening transition to lights off. Ovary-intact (mid-follicular phase) and ovariectomised marmosets did not differ significantly on any parameter of GnRH release. Overall, these results indicate that PPP can be used to reliably assess in vivo GnRH release in marmosets and will be a useful tool for future studies of reproductive neuroendocrinology in this small primate.

Search for neural substrates mediating inhibitory effects of oestrogen on pulsatile luteinising hormone-releasing hormone release in vivo in ovariectomized female rhesus monkeys (Macaca mulatta)

Neural substrates mediating the negative feedback effects of oestrogen on luteinising hormone-releasing hormone (LHRH) release were studied using the in vivo push-pull perfusion method in female rhesus monkeys. Twelve long-term ovariectomized female monkeys were implanted with Silastic capsules containing 17beta-oestradiol 2 weeks before the experiments and, on the day of the experiment, oestradiol benzoate (EB, 50 microg/kg) or oil was subcutaneously injected. Push-pull perfusate samples from the stalk-median eminence were collected in 10-min fractions from 4 h before to 18-20 h after EB or oil injection. LHRH and neuropeptide Y (NPY) levels in the same perfusates were measured by radioimmunoassay, and glutamate and GABA in the same perfusates were assessed by high-performance liquid chromatography (HPLC). The results indicate that EB significantly suppressed LHRH release (P < 0.005) starting within 2 h after EB, and continued for 18 h or until the experiment was terminated. Pulse analysis suggested that oestrogen suppressed the pulse amplitude, but not pulse frequency, of LHRH release. By contrast, EB did not alter any parameters (mean release, pulse amplitude or frequency) of pulsatile NPY release throughout the experiment. HPLC analysis further suggested that neither glutamate nor GABA levels in the stalk-median eminence were changed with oestrogen-induced LHRH suppression. Oil treatment did not alter LHRH, NPY, GABA and glutamate levels. It is concluded that oestrogen induces suppression of pulsatile LHRH release within 2 h, but the inhibitory effect of oestrogen on LHRH release does not appear to be mediated by NPY, GABAergic, or glutamatergic neurones.

Projections from estrogen receptor-alpha immunoreactive neurons in the periaqueductal gray to the lateral medulla oblongata in the rhesus monkey

The periaqueductal gray (PAG) contains numerous estrogen receptor-alpha immunoreactive (ER-alpha IR) neurons that are distributed in a species-specific way. These neurons might modulate different types of behavior that are mediated by the PAG such as active and passive coping responses, analgesia, and reproductive behavior. In primates, it is not known whether ER-alpha IR PAG neurons represent local interneurons and/or neurons that project to brainstem areas that control these behaviors. In this double labeling study, we asked whether ER-alpha IR neurons in the PAG of the rhesus monkey project to the nucleus retroambiguus (NRA), an area in the ventrolateral caudal medulla oblongata that is involved in expiration, vocalization, and reproductive behavior. Tracer was injected into the caudal lateral medulla oblongata to retrogradely label PAG neurons, and ER-alpha was visualized immunohistochemically. Although ER-alpha IR neurons and NRA-projection neurons were present at similar levels of the PAG, their distributions hardly overlapped. ER-alpha IR PAG neurons that project to the lateral caudal medulla represented less than 2% of ER-alpha IR PAG neurons. These double-labeled neurons were mainly located in the ipsilateral caudal PAG. The cluster of neurons in the medial part of the lateral PAG that projects specifically to the NRA-region did not contain double-labeled cells. The results indicate that only a few ER-alpha IR PAG neurons project to the NRA-region. This might be related to the modest effects of estrogen on mating-related behavior in primates compared most other mammalian species. Remaining ER-alpha IR PAG neurons might act locally on other PAG neurons, or they might represent neurons that project to other areas. Furthermore, the finding that the distributions of ER-alpha IR neurons and neurons that project to premotor neurons in the NRA-region scarcely overlap illustrates that the PAG in primates is very highly organized into anatomically distinct regions compared with other species.

Effect of dietary sulfur amino acids on the taurine content of rat tissues

The effect of dietary sulfur amino acids on the taurine content of rat blood and tissues was investigated. Three types of diet were prepared for this study: a low-taurine diet (LTD), normal taurine diet (NTD; LTD + 0.5% Met), and high-taurine diet (HTD; LTD + 0.5% Met + 3% taurine). These diets had no differing effect on the growth of the rats. The concentration of taurine in the blood from the HTD- and NTD-fed rats was respectively 1200% and 200% more than that from LTD-. In such rat tissues as the liver, the taurine content was significantly affected by dietary sulfur amino acids, resulting in a higher content with HTD and lower content with LTD. However, little or no effect on taurine content was apparent in the heart or eye. The activity for taurine uptake by the small intestine was not affected by dietary sulfur amino acids. The expression level of taurine transporter mRNA was altered only in the kidney under these dietary conditions: a higher expression level with LTD and lower expression level with HTD.

Synchronization of Ca(2+) oscillations among primate LHRH neurons and nonneuronal cells in vitro

Periodic release of luteinizing hormone-releasing hormone (LHRH) from the hypothalamus is essential for normal reproductive function. Pulsatile LHRH release appears to result from the synchronous activity of LHRH neurons. However, how the activity of these neurons is synchronized to release LHRH peptide in a pulsatile manner is unclear. Because there is little evidence of physical coupling among LHRH neurons in the hypothalamus, we hypothesized that the activity of LHRH neurons might be coordinated by indirect intercellular communication via intermediary (nonneural) cells rather than direct interneural coupling. In this study, we used an in vitro preparation of LHRH neurons derived from the olfactory placode of monkey embryos to assess whether nonneuronal cells, play a role in coordinating LHRH neuronal activity. We found that cultured LHRH neurons and nonneuronal cells both exhibit spontaneous oscillations in the concentration of intracellular Ca(2+) ([Ca(2+)](i)) at similar frequencies. Moreover, [Ca(2+)](i) oscillations in both types of cell were periodically synchronized. Synchronized [Ca(2+)](i) oscillations spread as intercellular Ca(2+) waves across fields of cells that included LHRH neurons and nonneuronal cells, although waves spread at a higher velocity among LHRH neurons. These results suggest that LHRH neurons and nonneuronal cells are functionally integrated and that nonneuronal cells could be involved in synchronizing the activity of the LHRH neurosecretory network.

Monosynaptic projections from the nucleus retroambiguus region to laryngeal motoneurons in the rhesus monkey

Vocalization and straining-related activities require the activation of laryngeal muscles. The control of laryngeal muscles during these activities is thought to be mediated by a pathway from the periaqueductal gray via premotor neurons in the nucleus retroambiguus to laryngeal motoneurons in the nucleus ambiguus. However, direct contacts between the nucleus retroambiguus and laryngeal motoneurons have never been demonstrated anatomically. Moreover, data in primates about the nucleus retroambiguus-nucleus ambiguus pathway are lacking. Therefore, the present study examines the projection from the nucleus retroambiguus region to laryngeal motoneurons in the rhesus monkey at the light and electron microscopic levels. Injections with wheat germ agglutinin-horseradish peroxidase were made into the nucleus retroambiguus in five rhesus monkeys to anterogradely label fibers in the nucleus ambiguus. In two of these animals, the cricothyroid muscle was injected with cholera toxin subunit b to identify the motoneurons that supply it. The results show that the nucleus retroambiguus region most densely projects to the compact formation of the nucleus ambiguus, whereas cricothyroid motoneurons, which surround the compact formation, receive a moderate projection. The projections are bilateral, with a contralateral predominance. Ultrastructurally, anterogradely labeled terminal profiles from the nucleus retroambiguus contact cholera toxin subunit b-labeled dendrites of cricothyroid motoneurons. The terminal profiles contain primarily spherical vesicles and form asymmetrical contacts with cricothyroid motoneurons. This study demonstrates that the nucleus retroambiguus region projects to the nucleus ambiguus in the primate. Some of these projections include monosynaptic connections to laryngeal motoneurons. This pathway is important for the control of the vocal folds during vocalization and straining-related activities.

Presence of luteinizing hormone-releasing hormone fragments in the rhesus monkey forebrain

Previously, we have shown that two types of luteinizing hormone-releasing hormone (LHRH) -like neurons, "early" and "late" cells, were discernible in the forebrain of rhesus monkey fetuses by using antiserum GF-6, which cross-reacts with several forms of LHRH. The "late" cells that arose from the olfactory placode of monkey fetuses at embryonic days (E) 32-E36, are bona fide LHRH neurons. The "early" cells were found in the forebrain at E32-E34 and settled in the extrahypothalamic area. The molecular form of LHRH in "early" cells differs from "late" cells, because "early" cells were not immunopositive with any specific antisera against known forms of LHRH. In this study, we investigated the molecular form of LHRH in the "early" cells in the nasal regions and brains of 13 monkey fetuses at E35 to E78. In situ hybridization studies suggested that both "early" and "late" LHRH cells expressed mammalian LHRH mRNA. Furthermore, "early" cells predominantly contain LHRH1-5-like peptide and its cleavage enzyme, metalloendopeptidase E.C.3.4.24.15 (EP24.15), which cleaves LHRH at the Tyr5-Gly6 position. This conclusion was based on immunocytochemical labeling with various antisera, including those against LHRH1-5, LHRH4-10, or EP24.15, and on preabsorption tests. Therefore, in primates, a group of neurons containing mammalian LHRH mRNA arises at an early embryonic stage before the migration of bona fide LHRH neurons, and is ultimately distributed in the extrahypothalamic region. These extrahypothalamic neurons contain LHRH fragments, rather than fully mature mammalian LHRH. The origin and function of these neurons remain to be determined.

Neural mechanisms underlying the pubertal increase in LHRH release in the rhesus monkey

Puberty is triggered by an increase in pulsatile release of luteinizing hormone-releasing hormone (LHRH) from the hypothalamus. Although the LHRH neurosecretory system is mature well before the onset of puberty, a central inhibitory mechanism restrains LHRH release in juvenile primates. Recent studies suggest that this central inhibition is primarily because of GABAergic neurotransmission. A reduction of GABAergic restraint appears to be essential for the initiation of puberty, but the mechanism that underlies the disinhibition process remains to be elucidated. Future research into the regulation of central inhibition should provide more effective treatments for the prevention of disease associated with abnormal pubertal development.

A novel mammalian receptor for the evolutionarily conserved type II GnRH

Mammalian gonadotropin-releasing hormone (GnRH I: pGlu-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-Gly-NH2) stimulates pituitary gonadotropin secretion, which in turn stimulates the gonads. Whereas a hypothalamic form of GnRH of variable structure (designated type I) had been shown to regulate reproduction through a cognate type I receptor, it has recently become evident that most vertebrates have one or two other forms of GnRH. One of these, designated type II GnRH (GnRH II: pGlu-His-Ser-His-Gly-Trp-Tyr-Pro-Gly-NH2), is conserved from fish to man and is widely distributed in the brain, suggesting important neuromodulatory functions such as regulating K+ channels and stimulating sexual arousal. We now report the cloning of a type II GnRH receptor from marmoset cDNA. The receptor has only 41% identity with the type I receptor and, unlike the type I receptor, has a carboxyl-terminal tail. The receptor is highly selective for GnRH II. As with the type I receptor, it couples to G(alpha)q/11 and also activates extracellular signal-regulated kinase (ERK1/2) but differs in activating p38 mitogen activated protein (MAP) kinase. The type II receptor is more widely distributed than the type I receptor and is expressed throughout the brain, including areas associated with sexual arousal, and in diverse non-neural and reproductive tissues, suggesting a variety of functions. Surprisingly, the type II receptor is expressed in the majority of gonadotropes. The presence of two GnRH receptors in gonadotropes, together with the differences in their signaling, suggests different roles in gonadotrope functioning.

Neural circuits regulating pulsatile luteinizing hormone release in the female guinea-pig: opioid, adrenergic and serotonergic interactions

We studied three neurotransmitters involved in the regulation of pulsatile luteinizing hormone (LH) release: opioid peptides, serotonin and norepinephrine, using the ovariectomized guinea-pig. This is an attractive animal model due to the regularity of its LH pulses, enabling any disruptions to be clearly ascertained. In all experiments, a specific agonist or antagonist was administered, either alone or serially to enable detection of interactions, and effects on mean LH concentrations, pulse amplitude and interpulse interval were determined by PULSAR analysis. In the ovariectomized guinea-pig, catecholamines are stimulatory (acting through the alpha1 and alpha2 but not beta receptors, unlike other species), opioids inhibitory and serotonin permissively stimulatory to pulsatile LH release. Stimulatory effects of the opiate antagonist were not blocked by pretreatment with an alpha1- or alpha2-adrenergic antagonist. Similarly, pretreatment with the opiate antagonist did not prevent the suppression of LH release by alpha1 and alpha2 antagonists. This suggests that, in the guinea-pig, effects of opiates and catecholamines on LH release are exerted by independent pathways to luteinizing hormone releasing hormone (LHRH) neurones. For the opiate-serotonin interactions, pretreatment with the serotonergic antagonist did not block the stimulatory effect of the opiate antagonist on LH release. However, pretreatment with the opiate agonist could not be overcome by the serotonergic agonist. This suggests that the effects of the serotonin system on LHRH release may be indirectly mediated by opioid neurones. Taken together, these studies demonstrate that the three neurotransmitter systems studied are critically involved in normal pulsatile LH release in the female guinea-pig, and demonstrate novel functional relationships between the opioid and the adrenergic and serotonergic systems.

Neurobiological mechanisms of the onset of puberty in primates

An increase in pulsatile release of LHRH is essential for the onset of puberty. However, the mechanism controlling the pubertal increase in LHRH release is still unclear. In primates the LHRH neurosecretory system is already active during the neonatal period but subsequently enters a dormant state in the juvenile/prepubertal period. Neither gonadal steroid hormones nor the absence of facilitatory neuronal inputs to LHRH neurons is responsible for the low levels of LHRH release before the onset of puberty in primates. Recent studies suggest that during the prepubertal period an inhibitory neuronal system suppresses LHRH release and that during the subsequent maturation of the hypothalamus this prepubertal inhibition is removed, allowing the adult pattern of pulsatile LHRH release. In fact, y-aminobutyric acid (GABA) appears to be an inhibitory neurotransmitter responsible for restricting LHRH release before the onset of puberty in female rhesus monkeys. In addition, it appears that the reduction in tonic GABA inhibition allows an increase in the release of glutamate as well as other neurotransmitters, which contributes to the increase in pubertal LHRH release. In this review, developmental changes in several neurotransmitter systems controlling pulsatile LHRH release are extensively reviewed.

Luteinizing hormone-releasing hormone (LHRH) neurons: mechanism of pulsatile LHRH release

Many types of neurons and glia exhibit oscillatory changes in membrane potentials and cytoplasmic Ca2+ concentrations. In neurons and neuroendocrine cells an elevation of intracellular Ca2+ concentration is associated with neurosecretion. Since both oscillatory membrane potentials and intracellular Ca2+ oscillations have been described in primary LHRH neurons and in GT1 cells, it is evident that an endogenous pulse-generator/oscillator is present in the LHRH neuron in vitro. The hourly rhythms of LHRH neurosecretion appear to be the synchronization of a population of LHRH neurons. How a network of LHRH neurons synchronizes their activity, i.e., whether by the result of synaptic mechanisms or electrical coupling through gap junctions or through a diffusible substance(s), remains to be clarified. Even though LHRH neurons themselves possess an endogenous pulse-generating mechanism, they may be controlled by other neuronal and nonneuronal elements in vivo. NE, NPY, glutamate, and GABA are neurotransmitters possibly controlling pulsatile LHRH release, and NO, cAMP, and ATP may be diffusible substances involved in pulsatile LHRH release without synaptic input. Although synaptic inputs to the perikarya of LHRH neurons could control the activity of LHRH neurons, a line of evidence suggests that direct neuronal and nonneuronal inputs, especially those from astrocytes to LHRH neuroterminals, appear to be more important for pusatile LHRH release.

Monosynaptic projections from the nucleus retroambiguus to motoneurons supplying the abdominal wall, axial, hindlimb, and pelvic floor muscles in the female rhesus monkey

The nucleus retroambiguus (NRA) consists of premotor neurons in the caudal medulla. It is involved in expiration, vomiting, vocalization, and probably reproductive behavior by means of projections to distinct motoneuronal cell groups. Because no information is available about the NRA and its efferent pathways in primates, the present study examines NRA projections to the lumbosacral spinal cord in female rhesus monkeys. To identify the NRA, wheat germ agglutinin-horseradish peroxidase (WGA-HRP) was injected into the lumbosacral cord in three monkeys. To study the distribution of NRA axons in the lumbosacral cord, WGA-HRP injections were made into the NRA in seven monkeys. To identify motoneuronal cell groups receiving input from the NRA, the same seven monkeys also received cholera toxin subunit b (CTb) injections into different hindlimb, axial, and pelvic floor muscles. The results show that NRA neurons projecting to the lumbosacral cord are mainly located between 1 to 4 mm caudal to the obex. They send numerous axons to external oblique and pelvic floor motoneurons, whereas projections to iliopsoas and axial motoneurons are less numerous. The projections are bilateral, but show a clear contralateral predominance in the iliopsoas, axial, and pelvic floor motoneuronal cell groups. At the ultrastructural level, NRA-terminal profiles make asymmetrical contacts with labeled and unlabeled dendrites in these motoneuronal cell groups and contain large amounts of spherical and a few dense core vesicles. It is concluded that the NRA is well developed in the monkey and that there exists a direct pathway from the NRA to lumbosacral motoneurons in this species. The finding that the NRA projects to a somewhat different set of motoneuronal cell groups compared with other species fits the concept that it is not only involved in expiration-related activities but also in species specific receptive and submissive behavior.

Monosynaptic projections from the lateral periaqueductal gray to the nucleus retroambiguus in the rhesus monkey: implications for vocalization and reproductive behavior

The periaqueductal gray (PAG) is known to be essential for vocalization and reproductive behavior. The PAG controls components of these behaviors by means of projections to the nucleus retroambiguus (NRA), a group of premotor neurons in the caudal medulla oblongata. In the accompanying study (VanderHorst et al., 2000 [accompanying study]), the NRA and its lumbosacral projections have been identified in the rhesus monkey. The present light and electron microscopical tracing study describes the PAG-NRA pathway in primates. To locate midbrain neurons projecting to the NRA, wheat germ agglutinin horseradish peroxidase (WGA-HRP) was injected into the NRA in six monkeys. To determine the distribution pattern of PAG axons in the medulla oblongata, WGA-HRP was injected into the PAG and adjacent tegmentum in three additional monkeys. In one of these three monkeys, biotinylated dextran amine and cholera toxin subunit b were injected into the lumbosacral cord to retrogradely identify NRA neurons. The results show that a compact group of neurons in the medial part of the lateral PAG at the intercollicular level sends a dense projection to the NRA. The projection is bilateral with a clear ipsilateral predominance. At the ultrastructural level, there are monosynaptic contacts between PAG fibers and NRA neurons, including NRA neurons that project to the lumbosacral cord. The synaptic contacts were primarily asymmetrical and the labeled terminal profiles contained spherical and dense core vesicles. It is concluded that there exists a strong and direct PAG-NRA pathway in the rhesus monkey. Because NRA neurons projecting to the lower lumbar cord are included, the PAG-NRA projection is likely to be involved not only in vocalization but also in other behaviors, such as receptive posture.

The role of neuropeptide Y in the progesterone-induced luteinizing hormone-releasing hormone surge in vivo in ovariectomized female rhesus monkeys

Progesterone induces a LHRH surge in estrogen-primed ovariectomized rhesus monkeys, with a concomitant increase in the pulse frequency of neuropeptide Y (NPY) release. However, the role for NPY in the positive feedback action of progesterone on LHRH release in primates is unknown. The present study examines the effect of an antisense oligodeoxynucleotide for NPY messenger RNA (AS NPY) on the progesterone-induced LHRH surge in vivo using push-pull perfusion. The AS NPY was directly infused into the stalk-median eminence (S-ME), whereas perfusates were collected for assessment of LHRH release. For a control, a scrambled oligodeoxynucleotide was infused. The results indicate that 1) the scrambled oligodeoxynucleotide did not interfere with the progesterone-induced LHRH surge, 2) whereas AS NPY blocked the progesterone-induced increase in LHRH release, and 3) no LHRH surges were induced by oil as a control for progesterone, but the AS NPY also reduced LHRH release in oil controls. These data suggest that 1) AS NPY infusion into the S-ME results in reduction in LHRH release; and 2) NPY release in the S-ME is important for the positive feedback effects of progesterone on LHRH release in estrogen-primed ovariectomized monkeys.

N-methyl D,L-aspartate induces the release of luteinizing hormone-releasing hormone in the prepubertal and pubertal female rhesus monkey as measured by in vivo push-pull perfusion in the stalk-median eminence

The role of the excitatory amino acid glutamate, N-methyl D-aspartate (NMDA) receptor agonist, in stimulating in vivo luteinizing hormone-releasing hormone (LHRH) release in the stalk-median eminence of conscious prepubertal and pubertal female rhesus monkeys was evaluated using push-pull perfusion. In Exp 1, the effects of i.v. bolus injection of N-methyl D,L-aspartate (NMA) on LHRH release were examined. Injection of NMA induced an increase in LHRH release in all maturational stages of monkeys. Although the LHRH response to NMA tended to be larger in the older groups, only the duration of the LHRH response in the midpubertal group was significantly longer than that in the prepubertal group. In Exp 2, the effects of direct infusion of NMA (0.1, 1, and 100 microM) into the stalk-median eminence on LHRH release were similarly examined. NMA infusion stimulated LHRH release in pubertal monkeys, whereas it did not induce any consistent changes in LHRH release in prepubertal monkeys except for the highest dose. These data suggest that: 1) the systemic injection of NMA is more effective than direct infusion of NMA; and 2) the prepubertal LHRH neurosecretory system is capable of responding to NMDA, although the responsiveness may undergo developmental changes. Therefore, stimulation of NMDA receptors may contribute to the pubertal changes in the LHRH neurosecretory activity.

Effects of pulsatile infusion of the GABA(A) receptor blocker bicuculline on the onset of puberty in female rhesus monkeys

In order to test the hypothesis that GABA is an inhibitory neurotransmitter restricting the release of LHRH before puberty, we examined the effects of pulsatile infusion of the GABA(A) receptor blocker, bicuculline, on the timing of puberty. Eleven female monkeys at 14-15 months of age were implanted with a stainless steel cannula into the base of the third ventricle above the median eminence. Five monkeys received bicuculline infusion every 2 h at a dose of 1 microM with a gradual increase to 100 microM in 10 microl using a portable infusion pump. The remaining 6 monkeys received similar infusions of saline. An additional 11 colony monkeys without cannula implantation were used for controls. Results indicate that bicuculline infusion advances the timing of puberty. The age of menarche (17.8+/-0.5 months) in the bicuculline infusion animals was significantly earlier than that in the saline controls (28.2+/-2.3, P < 0.001) as well as in colony controls (30.6+/-0.9, P < 0.001). The age of first ovulation (30.5+/-3.3 months) in bicuculline-treated animals was much younger (P < 0.001) than that in both controls (44.8+/-1.8 and 44.7+/-1.2, respectively). Bicuculline also accelerated the growth curve. These results suggest that the reduction of tonic GABA inhibition of LHRH neurons advances the onset of puberty.

Intracellular Ca(2+) oscillations in luteinizing hormone-releasing hormone neurons derived from the embryonic olfactory placode of the rhesus monkey

To understand the mechanism of pulsatile luteinizing hormone-releasing hormone (LHRH) release, we examined whether cultured LHRH neurons exhibit spontaneous intracellular Ca(2+) ([Ca(2+)](i)) signaling. The olfactory placode and the ventral migratory pathway of LHRH neurons from rhesus monkey embryos at embryonic ages 35-37 were dissected out and cultured on glass coverslips. Two to five weeks later, cultured cells were labeled with fura-2 and examined for [Ca(2+)](i) signaling by recording changes in [Ca(2+)](i) every 10 sec for 30-175 min. Cells were fixed and immunostained for LHRH and neuron-specific enolase. In 20 cultures, 572 LHRH-positive cells exhibited [Ca(2+)](i) oscillations at an interpulse interval (IPI) of 8.2 +/- 0.7 min and a duration of 88.8 +/- 2.9 sec. LHRH-negative neurons in culture exhibited only occasional [Ca(2+)](i) oscillations. In 17 of 20 cultures with LHRH-positive cells, [Ca(2+)](i) oscillations occurred synchronously in 50-100% of the individual cells, whereas [Ca(2+)](i) oscillations in cells in the remaining three cultures did not synchronize. Strikingly, in 12 of 17 cultures the synchronization of [Ca(2+)](i) oscillations repeatedly occurred in complete unison at 52.8 +/- 3.0 min intervals, which is similar to the period observed for LHRH release, whereas in 5 of 17 cultures the less tight synchronization of [Ca(2+)](i) oscillations repeatedly occurred at 23.4 +/- 4.6 min intervals. IPI of [Ca(2+)](i) oscillations in cells with tight synchronization and less tight synchronization did not differ from IPI in cells without synchronization. The results indicate that LHRH neurons derived from the monkey olfactory placode possess an endogenous mechanism for synchronization of [Ca(2+)](i) oscillations. Whether synchronization of [Ca(2+)](i) oscillations relates to neurosecretion remains to be investigated.

An increase in glutamate release follows a decrease in gamma aminobutyric acid and the pubertal increase in luteinizing hormone releasing hormone release in the female rhesus monkeys

Previously we have shown that release of gamma-aminobutyric acid (GABA) in the stalk-median eminence (S-ME) is high in prepubertal monkeys and that a decrease in GABA release triggers the onset of puberty. However, it is still unclear how disinhibition of the luteinizing hormone releasing hormone (LHRH) neuronal system from GABA input is followed (or accompanied) by an increase in stimulatory signals, such as glutamatergic input to LHRH neurons. To clarify the temporal relationship between the reduction of the GABAergic inhibitory signal and the enhancement of the glutamatergic stimulatory signal in the control of LHRH release at the onset of puberty, we conducted two experiments using a push-pull perfusion method. In the first experiment, we measured developmental changes in release of LHRH, GABA, and glutamate in the S-ME. LHRH levels were very low in prepubertal monkeys, increased to higher levels in early pubertal monkeys, with the highest LHRH levels occurring in mid-pubertal monkeys. As we previously observed, GABA levels were high in prepubertal monkeys and then decreased in early- and mid-pubertal monkeys. In contrast, glutamate levels were very low in prepubertal monkeys, increased dramatically in early pubertal monkeys, and then slightly decreased in mid-pubertal monkeys, although mid-pubertal levels remained much higher than prepubertal levels. In the second experiment, we measured GABA, glutamate and LHRH in the same samples obtained from prepubertal monkeys which were infused with an antisense oligodeoxynucleotide (AS) for glutamic acid decarboxylase (GAD) 67 mRNA into the S-ME. GAD67 is a catalytic enzyme for GABA synthesis from glutamate, and AS GAD67 mRNA interferes with GAD67 synthesis. Infusion of the AS GAD67 induced a decrease in GABA release, which subsequently resulted in an increase in LHRH release. Surprisingly, glutamate release also increased several hours after the decrease in GABA release, and the increased LHRH release continued. These data are interpreted to mean that a decrease in GABA synthesis by interference with GAD67 synthesis and the reduction of GABA release in the S-ME trigger an increase in LHRH release, but that a subsequent increase in glutamate release in the S-ME further contributes to the pubertal increase in LHRH release at the onset of puberty. The data further support our hypothesis that GAD plays an important role in the mechanism of the onset of puberty.

Pulsatile release of luteinizing hormone-releasing hormone (LHRH) in cultured LHRH neurons derived from the embryonic olfactory placode of the rhesus monkey

To study the mechanism of LH-releasing hormone (LHRH) pulse generation, the olfactory pit/placode and the migratory pathway of LHRH neurons from monkey embryos at embryonic age 35-37 were dissected out, under the microscope, and cultured on plastic coverslips coated with collagen in a defined medium for 2-5 weeks. First, we examined whether cultured neurons release the decapeptide into media. It was found that LHRH cells release LHRH in a pulsatile manner at approximately 50-min intervals. Further, LHRH release was stimulated by depolarization with high K+ and the Na+ channel opener, veratridine. However, whereas the Na+ channel blocker, tetrodotoxin suppressed the effects of veratridine, tetrodotoxin did not alter the effects of high K+. Subsequently, the role of extracellular and intracellular Ca2+ in LHRH release was examined. The results are summarized as follows: 1) exposing the cells to a low Ca2+ (20 nM) buffer solution suppressed LHRH release, whereas exposure to a normal Ca2+ solution (1.25 mM) maintained pulsatile LHRH release; 2) LHRH release from cultured LHRH cells was stimulated by the voltage-sensitive L-type Ca2+ channel agonist, Bay K 8644 (10 microM), whereas it was suppressed by the L-type Ca2+ channel blocker, nifedipine (1 microM), but not by the N-type channel blocker, omega-conotoxin GVIA (1 microM); 3) the intracellular Ca2+ stimulant, ryanodine (1 microM), stimulated LHRH release, whereas the intracellular Ca2+ transporting adenosine triphosphatase antagonist, thapsigargin (1 and 10 microM), did not yield consistent results; and 4) carbonyl cyanide p-trifluoromethoxyphenyl-hydrazone (1 microM), a mitochondrial Ca2+ mobilizer, stimulated LHRH release, whereas ruthenium red, a mitochondrial Ca2+ uptake inhibitor, did not induce consistent results. These results indicate that: 1) the presence of extracellular Ca2+ is essential for LHRH neurosecretion; 2) Ca2+ enters the cell via L-type channels but not N-type channels; and 3) mobilization of intracellular Ca2+ from inositol 1,4,5-triphosphate-sensitive stores, as well as mitochondrial stores, seem to contribute to LHRH release in these cells.

A role of gamma-amino butyric acid (GABA) and glutamate in control of puberty in female rhesus monkeys: effect of an antisense oligodeoxynucleotide for GAD67 messenger ribonucleic acid and MK801 on luteinizing hormone-releasing hormone release

Previously we have shown that gamma-aminobutyric acid (GABA) is an inhibitory neurotransmitter restricting the pubertal increase in LHRH release in juvenile monkeys, and that interfering with GABA synthesis with an antisense oligodeoxynucleotide (AS) for glutamic acid decarboxylase (GAD67) mRNA results in an increase in LHRH release in prepubertal monkeys. GAD67 is a catalytic enzyme that synthesizes GABA from glutamate. To further clarify the role of GABA in puberty, we examined whether the inhibition of LHRH release by GABA continues after the onset of puberty and whether input from glutamatergic neurons plays any role in the onset of puberty when GABA inhibition declines, using a push-pull perfusion method. In Study I, the effects of the AS GAD67 mRNA on LHRH release in pubertal monkeys (34.3 +/- 1.5 months of age, n = 8) were examined, and the results were compared with those in prepubertal monkeys (18.5 +/- 0.4 months, n = 12). Direct infusion of AS GAD67 (1 microM) into the stalk-median eminence (S-ME) for 5 h stimulated LHRH release in both prepubertal and pubertal monkeys. However, the increase in LHRH release in pubertal monkeys was significantly (P < 0.01) smaller than that in prepubertal monkeys. Infusion of a scrambled oligo as a control was without effect in either group. In Study II, to examine the possibility that an increase in glutamate tone after the reduction of an inhibitory GABA tone contributes to the AS GAD67-induced LHRH increase, the effects of the NMDA receptor blocker MK801 (5 microM) on LHRH release were tested in monkeys treated with AS GAD67. MK801 infusion into the S-ME during the treatment of AS GAD67 (1 microM) suppressed the AS GAD67-induced LHRH release in both age groups. MK801 alone did not cause any significant effect in either group. The data are interpreted to mean that GABA continues to suppress LHRH release after the onset of puberty, although the degree of suppression is weakened considerably after the onset of puberty, and that the increased LHRH release after AS GAD67 treatment may be partly due to an increase in glutamate tone mediated by NMDA receptors, as well as due to the decrease in GABA release following the decrease in GAD synthesis. Taken together, the present results suggest that GAD may play an important role in the onset and progress of puberty in nonhuman primates.

Cellular mechanism of pulsatile LHRH release

One of the most intriguing characteristics of the luteinizing hormone-releasing hormone (LHRH) neuronal system in mammalian species is the pulsatile release pattern of the peptide from the hypothalamus into the portal circulation, which is essential for the maintenance of normal reproductive function. In this review article the new concept that LHRH neurons possess an endogenous pulse-generating mechanism, but this is modified by other neuronal and nonneuronal inputs is discussed.

Effects of an antisense oligodeoxynucleotide for neuropeptide Y mRNA on in vivo luteinizing hormone-releasing hormone release in ovariectomized female rhesus monkeys

The present study examines the effects of an antisense oligodeoxynucleotide (AS) for human neuropeptide Y (NPY) mRNA on in vivo LHRH release using the push-pull perfusion method in female ovariectomized monkeys. After 6 h of control perfusion, 10 microM of the AS NPY was infused for 8 h, which was followed by an additional 4 h of control perfusion. As a control for AS, an oligodeoxynucleotide containing the same bases in a scrambled sequence (SC) was similarly examined. LHRH and NPY levels in perfusate samples, collected in 10-min fractions, were measured by RIA. AS NPY infusion resulted in a significant decrease in mean NPY release starting 2 h after the initiation of infusion, and continuing until shortly after the end of AS infusion (P < 0.05, n = 7). AS NPY also suppressed mean LHRH release significantly (P < 0.05, n = 7): the AS NPY-induced LHRH suppression started 2 h after the initiation of AS infusion, and continued throughout AS infusion, lasting for the entire period of the experiment. In contrast, SC NPY resulted in neither significant changes in NPY release nor LHRH release. These data suggest that NPY release in the stalk-median eminence plays an important role in the control of pulsatile release of LHRH in vivo in the rhesus monkey.

A second form of gonadotropin-releasing hormone (GnRH) with characteristics of chicken GnRH-II is present in the primate brain

The primate brain was thought to contain only the GnRH known as mammalian GnRH (mGnRH). This study investigates whether a second form of GnRH exists within the primate brain. We found that brain extracts from adult stumptail and rhesus monkeys contained two forms of GnRH that were similar to mGnRH and chicken GnRH-II (cGnRH-II) based on the elution position of the peptides from HPLC and on cross-reactivity with antisera that are specific to mammalian or chicken GnRH-II in RIAs. The fetal brain of rhesus monkeys also contained mGnRH and a cGnRH-II-like peptide by the same criteria. Immunocytochemistry with a cGnRH-II-specific antiserum in adult and fetal rhesus monkeys showed immunopositive neurons generally scattered in the periaqueductal region of the midbrain, with a few positive cells in the posterior basal hypothalamus. Neurons immunopositive for cGnRH-II were fewer in number and smaller in size, with less defined nuclei and thinner neurites compared with those for mGnRH. Administration of synthetic cGnRH-II to adult rhesus monkeys resulted in a significant increase in the plasma LH concentration during the luteal phase of the menstrual cycle, but not during the midfollicular phase. We conclude that the primate brain contains mGnRH and a cGnRH-II-like molecule, although the function of the latter is unknown.

[A new handpiece attachment for Nd:YAG laser ablation of emphysematous bullae]

Recently, attention has been drawn to lung volume reduction for bullous emphysema by wedge excision or laser ablation. We used a neodymium: yttrium-aluminum garnet (Nd:YAG) laser with a free-beam mode to ablate peripheral emphysematous areas of lung tissue. To aid us in this procedure, we developed an attachment consisting of a stainless steel rod 3 cm in effective length, with a 1.8-cm diameter ring attached to its tip, and installed it on the tip of the laser handpiece used for free-beam laser ablation. This device has the following distinct advantages: 1) the distance between the tip of the laser and the pleura can easily be held constant, 2) the angle of irradiation can easily be maintained at 90 degrees. These result in 3) a constant area of irradiation (one square centimeter), and 4) an irradiated area that is clearly distinguished by the ring. In addition, the attachment is 5) simple and easy to construct. Three patients with bullous emphysema underwent unilateral laser ablation of the visceral pleura with the new device. All patients recovered completely. We found this rod-and-ring attachment to be useful for free-beam laser ablation.

Two populations of luteinizing hormone-releasing hormone neurons in the forebrain of the rhesus macaque during embryonic development

To investigate the possibility that a second luteinizing hormone-releasing hormone (LHRH) population appears during development in primates, embryos and fetal brains of rhesus monkeys were immunostained with antisera specific to different LHRH forms. Two LHRH cell populations were discernible by immunoreactivity to antisera LR-1 and GF-6. Because one LHRH cell type migrated out from the olfactory placode several days earlier than the other, they were referred to as "early" and "late" LHRH cells, respectively. Although late LHRH neurons were immunoreactive to all anti-mammalian LHRH antisera tested, early LHRH neurons were only detected by antiserum GF-6. Early LHRH neurons (approximately 10 x 7 microm) were smaller than late LHRH neurons (approximately 18 x 7 microm). Early LHRH neurons were first found around the olfactory placode, in the nasal mesenchyme, and in the rostroventral forebrain on embryonic day 30 (E30), whereas late LHRH neurons were first seen in the olfactory pit on E32. Early LHRH cells were located throughout the basal forebrain on E32-E42, whereas late LHRH cells were found in the olfactory pit and along the terminal nerve on E34-E36 and were not seen in the forebrain until E38. By E51-E62, late LHRH neurons reached into the basal hypothalamus in a distribution resembling that in the older brain, while early LHRH neurons were found in the septum, preoptic region, stria terminalis, medial amygdala, claustrum, internal capsule, and globus pallidus. Based on the distribution pattern of immunopositive cells with antiserum LR-1, late LHRH cells are bona fide LHRH neurons that regulate the pituitary-gonadal axis. In contrast, the molecular form of early LHRH cells is unclear, although it is plausible that early LHRH cells may contain the molecule in which the C-terminal epitope of LHRH is modified or absent. It is concluded that in primates there is a second population of LHRH neurons that originates from the embryonic olfactory placode before the origin of mammalian LHRH-like neurons, and that these two populations of LHRH-immunopositive neurons have different morphologic features and different final distributions in the brain.

Effects of adrenal medulla transplantation into the third ventricle on the onset of puberty in female rhesus monkeys

To test the hypothesis that prepubertal exposure of LHRH neurons to a source of catecholamines and neuropeptides accelerates the onset of puberty, we examined the effects of autologous adrenal transplantation into the base of the third ventricle of the brain in juvenile female rhesus monkeys at 11-13 months of age. The adrenal medulla, which contains catecholamines and neuropeptide Y (NPY), was cut into small pieces and mixed with gelfoam in artificial CSF and injected into the third ventricle, adjacent to LHRH neurons and their neuroterminals. Sham control monkeys received artificial CSF with gelfoam alone. Animals were monitored for signs of pubertal development. While menarche was not altered by adrenal transplantation, the timing of first and second ovulations occurred significantly (P < 0.05) earlier in adrenal-transplanted monkeys. Histological examination indicated that the grafts survived in all transplanted monkeys. The presence of catecholamines and NPY in graft tissue was confirmed by tyrosine-hydroxylase-positive, dopamine beta-hydroxylase-positive, and NPY-positive cells. Endogenous LHRH fibers were observed innervating the graft tissue. We conclude that: (1) adrenal medulla transplantation into the third ventricle accelerates the age of first ovulation; (2) this is likely due to neuroactive substances (e.g., catecholamines and NPY) from the graft tissue; and (3) grafted adrenal medulla tissue can survive for at least 30-40 months. However, the age of menarche was not accelerated by this grafting, suggesting that an additional mechanism (e.g., removal of tonic inhibition) may be necessary for the onset of puberty.

Role of glutamic acid decarboxylase in the prepubertal inhibition of the luteinizing hormone releasing hormone release in female rhesus monkeys

To investigate further the role of GABA in the onset of puberty, this study examines whether glutamic acid decarboxylase (GAD), the catalytic enzyme for GABA synthesis, is involved in the suppression of luteinizing hormone releasing hormone (LHRH) before puberty in rhesus monkeys. First, both GAD67 and GAD65 mRNAs were detectable by reverse transcription-PCR analysis in the preoptic area, medio-basal hypothalamus, posterior hypothalamic area, and hippocampus of the monkey brain. Second, effects of antisense oligodeoxynucleotides (D-oligos) for GAD67 and GAD65 mRNAs on LHRH release were examined in conscious female rhesus monkeys at the prepubertal stage using a push-pull perfusion method. The GAD67 or GAD65 antisense D-oligos or scrambled D-oligos were infused directly into the stalk-median eminence. Both the GAD67 and the GAD65 antisense D-oligos induced a large and prompt increase in LHRH release, whereas the scrambled D-oligos did not induce any significant effect. The results suggest that the removal of GABA inhibition by interfering with GAD synthesis is effective in increasing LHRH release in prepubertal monkeys. Third, the specificity of the antisense D-oligos on GAD levels was examined by incubating basal hypothalami with D-oligos in vitro and subsequent Western blot analysis. The antisense D-oligos consistently decreased the proteins GAD67 and GAD65 compared with respective control D-oligos. We conclude that the decrease of tonic GABAergic inhibition and maturational changes in GAD synthesis may be critical factors for the onset of puberty in nonhuman primates.