The effect of level of injury on diabetes incidence and mortality after spinal cord injury - a longitudinal cohort study

STUDY DESIGN

Retrospective longitudinal cohort study of veterans with SCI.

OBJECTIVES

Spinal cord injury (SCI) is associated with an increased risk of developing diabetes mellitus (DM), likely due to body composition alterations and autonomic nervous system dysfunction. These factors are more pronounced in persons with tetraplegia (TP) versus paraplegia (PP). However, the effect of level of injury (LOI) on DM incidence is largely unknown. Therefore, the objective is to examine the effect of LOI on DM incidence in persons with SCI.

SETTING

South Texas Veterans Health Care System.

METHODS

We obtained electronic record data on age, sex, race/ethnicity, LOI and HbA1c concentration from January 1st 2001 through December 31st 2021. Cox proportional hazard regression analyses were used to assess the association between LOI, DM and all-cause mortality.

RESULTS

Among 728 non-diabetic veterans with SCI (350 TP/ 378 PP, 52 ± 15 years, 690 male/38 female) 243 developed DM, of which 116 with TP and 127 with PP. Despite chronological variations between TP and PP, DM risk over the entire follow-up did not differ between the groups (hazard ratio (HR): 1.06, 95% CI: 0.82-1.38). Mortality was higher in TP versus PP (HR: 1.40, 95% CI: 1.09-1.78). However, developing DM did not increase the risk of death, regardless of LOI (HR: 1.07, 95% CI: 0.83-1.37).

CONCLUSION

Despite chronological variations between both groups, the level of injury had minimal effect on long-term DM development in this cohort of veterans with SCI. Sponsorship NIH (DK105379; MS), RR&D SPiRE (I21RX003724-01A1; MT and SH).

Meta-analysis on the Effectiveness of ECG Screening for Conditions Related to Sudden Cardiac Death in Young Athletes

Controversy exists over the use of electrocardiograms (ECGs) in sports pre-participation screening. We performed a meta-analysis comparing the effectiveness of history and physical examination (H&P) with ECG at detecting both cardiac disease and sudden cardiac death-associated conditions (SCD-AC). Pre-participation studies published from 2015 to 2020 with athletes 10 to 35 years old were included. This yielded 28 011 athletes screened and 124 cardiac diagnoses, 103 of which were SCD-AC. A meta-analysis of log odds ratios (ORs) was conducted using a random-effects model. The ORs for the association between H&P and detecting both cardiac disease and SCD-AC were not statistically significant (OR = 3.4, P = .076; OR = 2.9, P = .078). The ORs for the association between ECG and detecting both cardiac disease and SCD-AC were statistically significant (60, P < .001; 148, P < .0001). In conclusion, the odds of detecting both cardiac disease and conditions related to SCD with ECG are greater than with H&P during sports pre-participation screening.

Ethanol inhibits dopamine uptake via organic cation transporter 3: Implications for ethanol and cocaine co-abuse

Concurrent cocaine and alcohol use is among the most frequent drug combination, and among the most dangerous in terms of deleterious outcomes. Cocaine increases extracellular monoamines by blocking dopamine (DA), norepinephrine (NE) and serotonin (5-HT) transporters (DAT, NET and SERT, respectively). Likewise, ethanol also increases extracellular monoamines, however evidence suggests that ethanol does so independently of DAT, NET and SERT. Organic cation transporter 3 (OCT3) is an emergent key player in the regulation of monoamine signaling. Using a battery of in vitro, in vivo electrochemical, and behavioral approaches, as well as wild-type and constitutive OCT3 knockout mice, we show that ethanol's actions to inhibit monoamine uptake are dependent on OCT3. These findings provide a novel mechanistic basis whereby ethanol enhances the neurochemical and behavioral effects of cocaine and encourage further research into OCT3 as a target for therapeutic intervention in the treatment of ethanol and ethanol/cocaine use disorders.

Capsaicin 8% Patch for Spinal Cord Injury Focal Neuropathic Pain, a Randomized Controlled Trial

BACKGROUND

Neuropathic pain (NP) after spinal cord injury (SCI) exacerbates disability, decreases quality of life (QOL), and is often refractory to available therapies. Patients report willingness to trade potential recovery of strength, bowel, bladder, or sexual function for pain relief. One proposed mechanism causing NP is up-regulation of transient receptor potential vanilloid 1 (TRPV 1) proteins in uninjured C fibers and dorsal root ganglia causing neuronal excitability. Recent studies have found up-regulation of TRPV 1 proteins after SCI.

OBJECTIVE

We hypothesize the application of capsaicin 8% patch (C8P), FDA approved for NP in diabetic peripheral neuropathy and post-herpetic neuralgia, will improve pain, function and QOL in persons with SCI.

METHODS

Randomized single-blind crossover design in which 11 persons with SCI and NP refractory to two oral pain medications received C8P or a control low dose Capsaicin 0.025% patch (CON) over two 12-week periods. Pain (VAS, MPI-SCI), quality of life (WHO-QOL), and functional status (SCIM) were measured at 2-4-week intervals.

RESULTS

There was a main treatment effect of C8P over CON on VAS and MPI-SCI outcomes with pain reduction of 35% and 29% at weeks 2 and 4, respectively. C8P also demonstrated a main treatment effect over CON on the SCIM mobility subscale. WHO-QOL scores did not improve with C8P.

CONCLUSIONS

C8P improves pain and mobility for patients with SCI and refractory NP. Larger studies should be performed to evaluate impact of repeat applications and QOL outcomes.

Ambulatory blood pressure monitoring in children: A retrospective single-center study

OBJECTIVES

(1) Compare 24-hour ambulatory blood pressure monitoring (ABPM) diagnoses in a pediatric population with the new 2022 guidelines to the original diagnoses with the 2014 guidelines. (2) Determine whether findings of hypertension from ABPM could be predicted from prior patient data. (3) Determine whether ABPM readings could predict left ventricular mass index (LVMI) in patients who obtained an echocardiogram (ECHO).

STUDY DESIGN

Single-center retrospective study on patients referred to Pediatric Nephrology Clinic for evaluation of elevated blood pressure who underwent ABPM from 2015 to 2018. Predictions of hypertension were obtained using a logistic regression model, and predictions of LVMI were performed using regression models including (a) the wake systolic and diastolic BP indices, or (b) additionally including the standard deviation (SD) of wake SBP and DBP.

RESULTS

With the change in 2022 to new ABPM guidelines from the AHA, comparing the old and new guidelines led to 70% of previous pre-hypertensive diagnoses now meeting criteria for diagnosis of hypertension, and a rise from 21% of the ABPMs meeting criteria for hypertension to 51% now meeting criteria. In a logistic regression model, prior patient data were not predictive of a diagnosis of hypertension from ABPM (Nagelkerke's R ² = 0.04). Among the individual variables studied, none were statistically significant. For prediction of LVMI, the SD of wake SBP and DBP were significantly associated with increased LVMI, but the wake SBP and DBP indices were not.

CONCLUSIONS

In our patient population, the new ABPM guidelines led to a significant increase in diagnoses of hypertension. Prior patient data was not sufficient to predict a diagnosis of hypertension by ABPM, supporting the need for evaluation by ABPM as the gold standard. Our analysis of the relationship between ABPM readings and LVMI supports the hypothesis that BP variability contributes to increased LVMI. These data are consistent with growing evidence in the adult literature that BP variability detected by ABPM is associated with left-ventricular hypertrophy.

The discriminative stimulus effects of baclofen and gamma hydroxybutyrate in C57BL/6J mice

Baclofen and γ-hydroxybutyrate (GHB) exert γ-aminobutyric acid (GABA)B receptor agonism and have therapeutic utility but possess different pharmacological activities. We examined whether separate groups of mice could be trained to discriminate either baclofen or GHB, and the contribution of GABAB receptors to discriminative stimulus effects. Male C57BL/6J mice were trained to discriminate either baclofen (3.2 mg/kg, intraperitoneal) or GHB (178 mg/kg, intraperitoneal) from saline under a fixed-ratio 10 schedule. The GABAB antagonist 3-aminopropyl(diethoxymethyl)phosphinic acid (CGP 35348) was used to pharmacologically assess GABAB receptor involvement. The selectivity of the resulting discriminations was assessed with the opioid agonist morphine and the benzodiazepine midazolam. In baclofen-trained mice, both baclofen and GHB were readily discriminated. Baclofen produced a maximum of 86% baclofen-appropriate responding. CGP 35348 (320 mg/kg, i.p.) produced a 4.7-fold rightward shift in the dose-effect function. GHB produced a maximum of 85.8% baclofen-appropriate responding. In GHB-trained mice, both GHB and baclofen were readily discriminated. In GHB-trained mice, GHB produced a maximum of 85.3% drug-appropriate responding; CGP 35348 (320 mg/kg, i.p.) produced a 1.8-fold rightward shift in the GHB discrimination dose-effect function. Baclofen produced up to 70.0% GHB-appropriate responding. CGP 35348 (320 mg/kg, i.p.) significantly antagonized baclofen discrimination and baclofen produced up to 37% GHB-appropriate responding up to doses that disrupted operant responding. Morphine did not produce substitution for either baclofen or GHB. Midazolam produced partial substitution for both. GHB and baclofen discrimination assays in mice provide a useful approach for examining different receptor types mediating the effects of these two drugs.

Thyroid nodules of indeterminate cytology in Hispanic/Latinx patients

BACKGROUND

Behavior of differentiated thyroid cancer (DTC) varies among ethnic groups. Recommended management of thyroid nodules with indeterminate cytology (TN-IC) is based on molecular analysis from predominantly non-Hispanic white patients. We hypothesized that TN-IC in Hispanic/Latinx patients would have different features, management, and outcomes and that molecular testing might perform differently in Hispanic/Latinx patients.

METHODS

Retrospective chart review was performed on 127 TN-IC analyzed with Afirma. Patient characteristics were compared using linear model ANOVA and Fisher's exact test.

RESULTS

Out of 127 TN-IC, 71 (56%) were Hispanic/Latinx. Hispanic/Latinx had a greater prevalence of diabetes, but Afirma results (benign or suspicious) were similar between ethnic groups. Fourteen patients had malignant pathology. Their management and outcomes were similar across groups. The negative predictive value for our cohort (97.9%) was similar to published data.

CONCLUSIONS

Data from our predominantly-Hispanic/Latinx cohort suggest that Afirma performs similarly in Hispanic/Latinx and non-Hispanic white patients with TN-IC.

Impact of tetraplegia vs. paraplegia on venoarteriolar, myogenic and maximal cutaneous vasodilation responses of the microvasculature: Implications for cardiovascular disease

Objective: Cardiovascular disease (CVD) is a leading cause of mortality in persons with SCI. While macrovascular remodeling and function after SCI is well documented, changes in the microvascular structure and function are comparably understudied, but importantly predict CVD risk. Specifically, the integrity of venoarteriolar (VAR), myogenic (MYO) and maximal vasodilation responses are largely unknown after SCI, especially in persons with tetraplegia (TP) at highest risk of CVD. This is the first to examine the differences in VAR (cuff inflation), MYO (limb dependency) and maximal vasodilation responses of the microvasculature between able bodied (AB) versus those with TP and paraplegia (PP).Design: Observational.Setting: Laboratory.Participants: Eight AB, 6 TP, and 8 PP persons.Interventions: One forearm and calf were treated topically with lidocaine 2.5%/prilocaine 2.5% while contralateral limb served as a control. Laser doppler flowmeters were applied over treated and control sites during limb dependency, cuff inflation and local skin heating (Tloc) up to 42°C.Outcome measures: Skin vascular resistance (SkVR) change with cuff inflation and limb dependency and maximal cutaneous vascular conductance (CVC) during local heating.Results: Change in SkVR was not significantly different between groups or extremity (upper vs. lower) during cuff inflation or limb dependency. However, CVC at Tloc 42°C was significantly different in the lower extremity (LE) of TP and PP (P = 0.007, 0.35) compared to AB.Conclusion: Increases in SkVR during cuff inflation (VAR) and limb dependency (VAR and MYO) are unaltered after SCI, however maximal vasodilation in the LE post-SCI is higher than AB persons.

Role of Organic Cation Transporter 3 and Plasma Membrane Monoamine Transporter in the Rewarding Properties and Locomotor Sensitizing Effects of Amphetamine in Male andFemale Mice

A lack of effective treatment and sex-based disparities in psychostimulant addiction and overdose warrant further investigation into mechanisms underlying the abuse-related effects of amphetamine-like stimulants. Uptake-2 transporters such as organic cation transporter 3 (OCT3) and plasma membrane monoamine transporter (PMAT), lesser studied potential targets for the actions of stimulant drugs, are known to play a role in monoaminergic neurotransmission. Our goal was to examine the roles of OCT3 and PMAT in mediating amphetamine (1 mg/kg)-induced conditioned place preference (CPP) and sensitization to its locomotor stimulant effects, in males and females, using pharmacological, decynium-22 (D22; 0.1 mg/kg, a blocker of OCT3 and PMAT) and genetic (constitutive OCT3 and PMAT knockout (−/−) mice) approaches. Our results show that OCT3 is necessary for the development of CPP to amphetamine in males, whereas in females, PMAT is necessary for the ability of D22 to prevent the development of CPP to amphetamine. Both OCT3 and PMAT appear to be important for development of sensitization to the locomotor stimulant effect of amphetamine in females, and PMAT in males. Taken together, these findings support an important, sex-dependent role of OCT3 and PMAT in the rewarding and locomotor stimulant effects of amphetamine.

Correlation of neurological level and sweating level of injury in persons with spinal cord injury

Objective: Thermoregulatory dysfunction after spinal cord injury (SCI) impairs quality of life and predisposes persons to life-threatening sequela of heat-related illness (HRI) in conditions of high ambient temperature. SCI clinicians currently have no objective way to predict which persons are at greatest risk of HRI. Evaporative cooling via sweating is the body's most efficient mechanism of heat dissipation. The relationship between the neurological level of injury (NLOI) and the degree of sudomotor dysfunction is not well defined. This study examines the relationship between the NLOI and sweating level of injury (SwLOI). This information can assist SCI clinicians in identifying individuals with SCI who have most impaired sudomotor function and thus highest risk of HRI.Design: Observational.Setting: Human physiology laboratory.Participants: 10 persons with tetraplegia (TP), 14 with paraplegia (PP) and 10 able-bodied (AB).Intervention: Passive heat stress (1°C rise in core temperature) with sweat responses (SR) quantified with the starch iodine test.Outcome measures: The most caudal dermatomal level in which sweating was visualized was recorded as the SwLOI, which was compared to the NLOI. Minimum, maximum and median differences between NLOI and SwLOI were calculated.Results: Persons with tetraplegia demonstrated no SR. Persons with paraplegia demonstrated SR at a median of 1 level below NLOI. Able-bodied controls demonstrated sweating on all skin surface areas.Conclusions: Persons with motor complete tetraplegia lack evaporative cooling capacity through SR during passive heat stress predisposing them to HRI. Meanwhile, persons with paraplegia sweat on average 1 dermatomal level below their NLOI.

A Meta-analysis of the Utility of Red Cell Distribution Width as a Biomarker to Predict Outcomes in Pediatric Illness (PROSPERO CRD42020208777)

Red cell distribution width (RDW) is an average of the variation in red blood cell (RBC) sizes reported on a complete blood count. An elevated RDW indicates a pathological process that is affecting erythropoiesis. Studies showed that as the severity of disease process increases, the RDW often increases as well. Particularly in resource-limited countries, RDW has been studied as an outcome predictor for conditions in a variety of disciplines and is offered as an adjunct monitoring tool that is cost effective, readily available, and indicative of pathological processes amenable to intervention. Particularly in pediatric critical care settings, RDW has been shown to be a reliable tool for surveillance of disease states such as sepsis. Despite the increased attention of RDW as a marker for disease outcome, collective evaluation on the utility of RDW as a marker for outcome in pediatric critical care settings is lacking. We offer a systematic review and meta-analysis of published studies to assess the ability of RDW to predict illness severity and mortality among pediatric critical care patients. Among eight studies of over 4,800 patients, we found over a two-fold increase in odds for mortality in critically ill children whose RDW was above 15.7%. This is the first systematic review of RDW being used to predict mortality in critically ill children and findings of this study may prompt early intervention in the pediatric critical care setting.

Phosphatidylethanol in whole blood of rhesus monkeys correlates with ethanol consumption

BACKGROUND

Phosphatidylethanol (PEth) homologs are ethanol metabolites used to identify and monitor alcohol drinking in humans. In this study, we measured levels of the 2 most abundant homologs, PEth 16:0/18:1 and PEth 16:0/18:2, in whole blood samples from rhesus macaque monkeys that drank ethanol daily ad libitum to assess the relationship between PEth levels and recent ethanol exposure in this animal model.

METHODS

Blood samples were obtained from The Monkey Alcohol Tissue Research Resource. The monkeys were first induced to consume 4% (w/v) ethanol in water from a panel attached to their home cage. Then, monkeys were allowed to drink ethanol and water ad libitum 22 h daily for 12 months and the daily amount of ethanol each monkey consumed was measured. Whole, uncoagulated blood was collected from each animal at the end of the entire experimental procedure. PEth 16:0/18:1 and PEth 16:0/18:2 levels were analyzed by HPLC with tandem mass spectrometry, and the ethanol consumed during the preceding 14 days was measured. Combined PEth was the sum of the concentrations of both homologs.

RESULTS

Our results show that (1) PEth accumulates in the blood of rhesus monkeys after ethanol consumption; (2) PEth homolog levels were correlated with the daily average ethanol intake during the 14-day period immediately preceding blood collection; (3) the application of established human PEth 16:0/18:1 cutoff concentrations indicative of light social or no ethanol consumption (<20 ng/ml), moderate ethanol consumption (≥ 20 and < 200 ng/ml) and heavy ethanol consumption (≥ 200 ng/ml) predicted significantly different ethanol intake in these animals. PEth homologs were not detected in ethanol-naïve controls.

CONCLUSIONS

This study confirms that PEth is a sensitive biomarker for ethanol consumption in rhesus macaque monkeys. This nonhuman primate model may prove useful in evaluating sources of variability previously shown to exist between ethanol consumption and PEth homolog levels among humans.

Serotonin Transporter and Plasma Membrane Monoamine Transporter Are Necessary for the Antidepressant-Like Effects of Ketamine in Mice

Major depressive disorder is typically treated with selective serotonin reuptake inhibitors (SSRIs), however, SSRIs take approximately six weeks to produce therapeutic effects, if any. Not surprisingly, there has been great interest in findings that low doses of ketamine, a non-competitive N-methyl-D-aspartate (NMDA) receptor antagonist, produce rapid and long-lasting antidepressant effects. Preclinical studies show that the antidepressant-like effects of ketamine are dependent upon availability of serotonin, and that ketamine increases extracellular serotonin, yet the mechanism by which this occurs is unknown. Here we examined the role of the high-affinity, low-capacity serotonin transporter (SERT), and the plasma membrane monoamine transporter (PMAT), a low-affinity, high-capacity transporter for serotonin, as mechanisms contributing to ketamine’s ability to increase extracellular serotonin and produce antidepressant-like effects. Using high-speed chronoamperometry to measure real-time clearance of serotonin from CA3 region of hippocampus in vivo, we found ketamine robustly inhibited serotonin clearance in wild-type mice, an effect that was lost in mice constitutively lacking SERT or PMAT. As expected, in wild-type mice, ketamine produced antidepressant-like effects in the forced swim test. Mapping onto our neurochemical findings, the antidepressant-like effects of ketamine were lost in mice lacking SERT or PMAT. Future research is needed to understand how constitutive loss of either SERT or PMAT, and compensation that occurs in other systems, is sufficient to void ketamine of its ability to inhibit serotonin clearance and produce antidepressant-like effects. Taken together with existing literature, a critical role for serotonin, and its inhibition of uptake via SERT and PMAT, cannot be ruled out as important contributing factors to ketamine’s antidepressant mechanism of action. Combined with what is already known about ketamine’s action at NMDA receptors, these studies help lead the way to the development of drugs that lack ketamine’s abuse potential but have superior efficacy in treating depression.

Effect of concurrent organic cation transporter blockade on norepinephrine clearance inhibiting- and antidepressant-like actions of desipramine and venlafaxine

Depression is a major health problem for which most patients are not effectively treated. This underscores a need to identify new targets for the development of antidepressants with improved efficacy. Studies have shown that blockade of low-affinity/high-capacity transporters, such as organic cation transporters (OCTs) and the plasma membrane monoamine transporter (PMAT), with decynium-22 can produce antidepressant-like effects and inhibit serotonin clearance in brain when the serotonin transporter is pharmacologically or genetically compromised. In vitro studies show that OCTs/PMAT are also capable of norepinephrine transport, raising the possibility that decynium-22 might enhance the antidepressant-like effects of norepinephrine transporter inhibitors. Using in vivo electrochemistry, we show that local administration of decynium-22 into dentate gyrus of hippocampus enhanced the ability of the norepinephrine transporter blocker, desipramine, but not the dual norepinephrine/serotonin transporter blocker venlafaxine, to inhibit norepinephrine clearance. In parallel, systemic administration of decynium-22 (0.32 mg/kg) enhanced the antidepressant-like effects of desipramine (32 mg/kg), but not those of venlafaxine, in the tail suspension test, underscoring the heterogeneous response of mice to antidepressants, including those that share similar mechanisms of action. Systemic administration of normetanephrine, a potent blocker of OCT3, failed to potentiate the antidepressant-like effects of desipramine, suggesting that the actions of decynium-22 to augment the antidepressant-like effects of desipramine are likely mediated by another OCT isoform and/or PMAT. Taken together with existing literature, concurrent blockade of OCTs and/or PMAT merits further investigation as an adjunctive therapeutic for desipramine-like antidepressant drugs.

Correlation of Medical College Admission Test Scores and Self-assessment Materials with the United States Medical Licensing Examination Step 1 Performance

Purpose

Candidates' performance on the United States Medical Licensing Examination (USMLE) Step 1 examination had been correlated with the Medical College Admission Test (MCAT). However, in 2015, a new MCAT format was released and its correlation with Step 1 remains to be fully analyzed. Preparation for Step 1 typically involves purchasing and perusing practice tests from the National Board of Medical Examiners (NBME) and UWorld; however, their predictive value to performance on Step 1 remains to be ascertained, especially with the release of five new NBME practice tests. Additionally, there is a need for accurately predicting Step 1 scores to self-evaluate study progress and reduce student anxiety.

Rationale

Program directors rank USMLE Step 1 scores as the number one criterion in selecting interviewees for residency. Step 1 scores are more important than Step 2 scores, Dean’s letter, or other letters of recommendation in determining the overall ranking of a candidate after interviews.

Hypotheses

The authors hypothesized that the new MCAT scores correlated positively with Step 1 scores and that the new NBME practice tests were more predictive of performance on Step 1 as compared to old NBME tests. 

Methods

Linear regression analysis followed by either analysis of variance (ANOVA) or Student's t-tests were used to analyze 399 responses. Data obtained was used to update an existing Step 1 score predictor, which was then validated.

Results

A positive correlation between the MCAT (average score: 510.1 ± 6.3) and Step 1 scores (average score: 246.1 ± 14.2) was observed. While new NBME practice tests were more predictive of Step 1 scores than old NBME tests, UWorld test scores were the most predictive. Students who practiced with the new NBME practice tests scored significantly higher than students who did not use them. However, students using any of the UWorld practice tests did significantly better than students who practiced using only NBME practice tests but not UWorld practice tests. Ironically, NBME16,the second-most correlativetest to Step 1 performance, is no longer available for purchase. Overall, taking six or more practice tests significantly enhanced Step 1 scores; the optimal number of tests was found to be between six and nine. The predicted score by an updated Step 1 score predictor was within 3.8 points or 1.6% of the actual Step 1 score.

Conclusions

We believe this study will aid in the selection and purchase of appropriate self-assessment tests as preparatory material for the USMLE Step 1 examination. It will also introduce them to an existing Step 1 score predictor that will help determine their readiness for Step 1.

Factors that prevent, prompt, and delay disclosures in female victims of child sexual abuse

BACKGROUND

Several studies conducted in clinical and non-clinical settings have described why and when children disclose sexual abuse. Yet, there is incomplete understanding of how adolescents and young children may differ in factors that delay, prompt and deter disclosure that could inform strategies for clinical practice and prevention.

OBJECTIVE

The aim of this study was to identify factors that prevent, prompt, and delay disclosure among pediatric patients presenting for acute and non-acute medical evaluations of sexual abuse or assault, and to examine any differences in disclosure tendencies among female adolescents and pre-adolescents.

PARTICIPANTS AND SETTING

A chart review of a consecutive sample of pediatric patients presenting to the emergency department or outpatient clinic identified 601 patients who were diagnosed with sexual abuse and were willing to answer examiner questions about their disclosure.

METHODS

Data collection included attainment of patient narratives which were utilized to gather information about abuse disclosures. Recursive abstraction was applied to categorize patient statements for further analysis, while Pearson chi square and logistic regression were utilized for quantitative data.

RESULTS

Young age (<11 years) at abuse onset was the strongest predictor of, and fear of consequences to self was the most common reason for, disclosure delay in both adolescent and pre-adolescent females. Severity of abuse, adult perpetrator, and self-blame predicted delays only in pre-adolescent females.

CONCLUSIONS

Social and moral development during middle childhood likely has a strong influence on disclosure tendency. Strategies to promote disclosure should consider reducing fear of consequences associated with the adult-child paradigm.

Prolactin receptor expression in mouse dorsal root ganglia neuronal subtypes is sex-dependent

Sensory neurones exhibit sex-dependent responsiveness to prolactin (PRL). This could contribute to sexual dimorphism in pathological pain conditions. The present study aimed to determine the mechanisms underlying sex-dependent PRL sensitivity in sensory neurones. A quantitative reverse transcriptase-polymerase chain reaction shows that prolactin receptor (Prlr) long and short isoform mRNAs are expressed at comparable levels in female and male mouse dorsal root ganglia (DRG). In Prlr^cre/+ ;Rosa26^{LSL-tDTomato/+} reporter mice, percentages of Prlr⁺ sensory neurones in female and male DRG are also similar. Characterisation of Prlr⁺ DRG neurones using immunohistochemistry and electrophysiology revealed that Prlr⁺ DRG neurones are mainly peptidergic nociceptors in females and males. However, sensory neurone type-dependent expression of Prlr is sex dimorphic. Thus, Prlr⁺ populations fell into three small- and two medium-large-sized sensory neuronal groups. Prlr⁺ DRG neurones are predominantly medium-large sized in males and are proportionally more comprised of small-sized sensory neurones in females. Specifically, Prlr⁺ /IB4⁺ /CGRP⁺ neurones are four- to five-fold higher in numbers in female DRG. By contrast, Prlr⁺ /IB4^- /CGRP⁺ /5HT3a⁺ /NPYR2^- are predominant in male DRG. Prlr⁺ /IB4^- /CGRP^- , Prlr⁺ /IB4^- /CGRP⁺ and Prlr⁺ /IB4^- /CGRP⁺ /NPYR2⁺ neurones are evenly encountered in female and male DRG. These differences were confirmed using an independently generated single-cell sequencing dataset. Overall, we propose a novel mechanism by which sensory neurone type-dependent expression of Prlr could explain the unique sex dimorphism in responsiveness of nociceptors to PRL.

Efficacy of water spray for evaporative cooling in athletes with spinal cord injury

Study design

Interventional crossover study.

Objective

Spinal cord injury (SCI) disrupts afferent input to the hypothalamus and impairs efferent vaso- and sudomotor output, especially in lesions above the sympathetic chain (T1-L2). In consequence, persons with SCI under heat stress experience impairment in the ability to dissipate heat proportional to the lesion level. Thermoregulatory dysfunction places an individual at high risk of hyperthermia, which can be life threatening, especially for athletes with SCI during exercise. Current evidence on therapeutic cooling techniques in athletes with SCI is limited, but basic physiologic and research data suggest water spray (WS) might be efficacious, particularly in athletes with tetraplegia (TP), who are most impaired in thermoregulation. The aim of this study was to evaluate the effect of WS on core temperature (Tc) during exercise in athletes with SCI.

Setting

Texas, USA.

Methods

Eleven individuals with SCI: seven with TP, four with paraplegia (PP); and sixteen able-bodied (AB) controls underwent a wheelchair intermittent sprint exercise for 90 min under two conditions: (1) WS application every 15 min and (2) control (C), without WS. Tc was measured every 15 min and was analyzed for the effect of group (TP, PP, and AB) and time. Change in Tc (ΔTc) was also compared between groups.

Results

ΔTc was significantly higher in TP vs. PP (p < 0.0001) and TP vs. AB (p < 0.0001) groups under C treatment. WS significantly attenuated ΔTc in TP (p = 0.001), but did not change ΔTc in PP or AB.

Conclusion

WS effectively attenuated Tc elevation during exercise in athletes with TP.

Sponsorship

Texas chapter of the Paralyzed Veterans of America.

An unsuspected role for organic cation transporter 3 in the actions of amphetamine

Amphetamine abuse is a major public health concern for which there is currently no effective treatment. To develop effective treatments, the mechanisms by which amphetamine produces its abuse-related effects need to be fully understood. It is well known that amphetamine exerts its actions by targeting high-affinity transporters for monoamines, in particular the cocaine-sensitive dopamine transporter. Organic cation transporter 3 (OCT3) has recently been found to play an important role in regulating monoamine signaling. However, whether OCT3 contributes to the actions of amphetamine is unclear. We found that OCT3 is expressed in dopamine neurons. Then, applying a combination of in vivo, ex vivo, and in vitro approaches, we revealed that a substantial component of amphetamine's actions is OCT3-dependent and cocaine insensitive. Our findings support OCT3 as a new player in the actions of amphetamine and encourage investigation of this transporter as a potential new target for the treatment of psychostimulant abuse.

Comparative analysis of novel decynium-22 analogs to inhibit transport by the low-affinity, high-capacity monoamine transporters, organic cation transporters 2 and 3, and plasma membrane monoamine transporter

Growing evidence supports involvement of low-affinity/high-capacity organic cation transporters (OCTs) and plasma membrane monoamine transporter (PMAT) in regulating clearance of monoamines. Currently decynium-22 (D22) is the best pharmacological tool to study these transporters, however it does not readily discriminate among them, underscoring a need to develop compounds with greater selectivity for each of these transporters. We developed seven D22 analogs, and previously reported that some have lower affinity for α1-adrenoceptors than D22 and showed antidepressant-like activity in mice. Here, we extend these findings to determine the affinity of these analogs for OCT2, OCT3 and PMAT, as well as serotonin, norepinephrine and dopamine transporters (SERT, NET and DAT) using a combination of uptake competition with [³H]methyl-4-phenylpyridinium acetate in overexpressed HEK cells and [³H]citalopram, [³H]nisoxetine and [³H]WIN 35428 displacement binding in mouse hippocampal and striatal preparations. Like D22, all analogs showed greater binding affinities for OCT3 than OCT2 and PMAT. However, unlike D22, some analogs also showed modest affinity for SERT and DAT. Dual OCT3/SERT and/or OCT3/DAT actions of certain analogs may help explain their ability to produce antidepressant-like effects in mice and help account for our previous findings that D22 lacks antidepressant-like effects unless SERT function is either genetically or pharmacologically compromised. Though these analogs are not superior than D22 in discriminating among OCTs/PMAT, our findings point to development of compounds with combined ability to inhibit both low-affinity/high-capacity transporters, such as OCT3, and high-affinity/low-capacity transporters, such as SERT, as therapeutics with potentially improved efficacy for treatment of psychiatric disorders.

Pharmacokinetics of Phosphatidylethanol 16:0/20:4 in Human Blood After Alcohol Intake

BACKGROUND

The purpose of this study was to characterize the pharmacokinetics of the phosphatidylethanol (PEth) 16:0/20:4 homolog in uncoagulated human blood samples taken from 18 participants in a clinical laboratory setting after consumption of 2 standard doses of ethanol (EtOH).

METHODS

Male and female participants received either 0.4 or 0.8 g/kg oral doses of EtOH during a 15-minute period. Blood samples were collected before and throughout 6 hours immediately after alcohol administration and then again at days 2, 4, 7, 11, and 14 of the follow-up period. PEth 16:0/20:4 levels were quantified by high-performance liquid chromatography with tandem mass spectrometry detection.

RESULTS

(i) The increase in PEth 16:0/20:4 from baseline to maximum concentration was less than that of PEth 16:0/18:1 or PEth 16:0/18:2 homologs during the 6-hour period after EtOH administration; (ii) the mean half-life of PEth 16:0/20:4 was 2.1 ± 3 (SD) days, which was shorter than the mean half-life of either PEth 16:0/18:1 or PEth 16:0/18:2, 7.6 ± 3 (SD) or 6.8 ± 4 (SD) days, respectively.

CONCLUSIONS

The pharmacokinetics of PEth 16:0/20:4 in whole blood samples is detectable after alcohol consumption and differs in amount synthesized and rate of elimination versus PEth 16:0/18:1 and 16:0/18:2. Measuring the concentrations of these 3 homologs has the potential to provide more information about the amount and time frame of alcohol consumption than any one alone.

Constitutive plasma membrane monoamine transporter (PMAT, Slc29a4) deficiency subtly affects anxiety-like and coping behaviours

Originally, uptake-mediated termination of monoamine (e.g., serotonin and dopamine) signalling was believed to only occur via high-affinity, low-capacity transporters ("uptake1 ") such as the serotonin or dopamine transporters, respectively. Now, the important contribution of a second low-affinity, high-capacity class of biogenic amine transporters has been recognised, particularly in circumstances when uptake1 transporter function is reduced (e.g., antidepressant treatment). Pharmacologic or genetic reductions in uptake1 function can change locomotor, anxiety-like or stress-coping behaviours. Comparable behavioural investigations into reduced low-affinity, high-capacity transporter function are lacking, in part, due to a current dearth of drugs that selectively target particular low-affinity, high-capacity transporters, such as the plasma membrane monoamine transporter. Therefore, the most direct approach involves constitutive genetic knockout of these transporters. Other groups have reported that knockout of the low-affinity, high-capacity organic cation transporters 2 or 3 alters anxiety-like and stress-coping behaviours, but none have assessed behaviours in plasma membrane monoamine transporter knockout mice. Here, we evaluated adult male and female plasma membrane monoamine transporter wild-type, heterozygous and knockout mice in locomotor, anxiety-like and stress-coping behavioural tests. A mild enhancement of anxiety-related behaviour was noted in heterozygous mice. Active-coping behaviour was modestly and selectively increased in female knockout mice. These subtle behavioural changes support a supplemental role of plasma membrane monoamine transporter in serotonin and dopamine uptake, and suggest sex differences in transporter function should be examined more closely in future investigations.

A randomized control trial to establish the feasibility and safety of rapamycin treatment in an older human cohort: Immunological, physical performance, and cognitive effects

Inhibition of the mechanistic target of rapamycin (mTOR) pathway by rapamycin (RAPA), an FDA-approved immunosuppressive drug used as a clinical therapy to prevent solid organ allograft rejection, enhances longevity in mice. Importantly, RAPA was efficacious even when initiated in relatively old animals, suggesting that mTOR inhibition could potentially slow the progression of aging-associated pathologies in older humans (Harrison et al., 2009; Miller et al., 2011). However, the safety and tolerability of RAPA in older human subjects have not yet been demonstrated. Towards this end, we undertook a placebo-controlled pilot study in 25 generally healthy older adults (aged 70-95 years); subjects were randomized to receive either 1 mg RAPA or placebo daily. Although three subjects withdrew, 11 RAPA and 14 controls completed at least 8 weeks of treatment and were included in the analysis. We monitored for changes that would indicate detrimental effects of RAPA treatment on metabolism, including both standard clinical laboratory assays (CBC, CMP, HbA1c) and oral glucose tolerance tests (OGTTs). We also monitored parameters typically associated with aging that could potentially be modified by RAPA; these included cognitive function which was assessed by three different tools: Executive Interview-25 (EXIT25); Saint Louis University Mental Status Exam (SLUMS); and Texas Assessment of Processing Speed (TAPS). In addition, physical performance was measured by handgrip strength and 40-foot timed walks. Lastly, changes in general parameters of healthy immune aging, including serum pro-inflammatory cytokine levels and blood cell subsets, were assessed. Five subjects reported potential adverse side effects; in the RAPA group, these were limited to facial rash (1 subject), stomatitis (1 subject) and gastrointestinal issues (2 subjects) whereas placebo treated subjects only reported stomatitis (1 subject). Although no other adverse events were reported, statistically significant decrements in several erythrocyte parameters including hemoglobin (HgB) and hematocrit (Hct) as well as in red blood cell count (RBC), red blood cell distribution width (RDW), mean corpuscular volume (MCV), and mean corpuscular hemoglobin (MCH) were observed in the RAPA-treatment group. None of these changes manifested clinically significant effects during the short duration of this study. Similarly, no changes were noted in any other clinical laboratory, cognitive, physical performance, or self-perceived health status measure over the study period. Immune parameters were largely unchanged as well, possibly due to the advanced ages of the cohort (70-93 years; mean age 80.5). RAPA-associated increases in a myeloid cell subset and in T_REGS were detected, but changes in most other PBMC cell subsets were not statistically significant. Importantly, the OGTTs revealed no RAPA-induced change in blood glucose concentration, insulin secretion, and insulin sensitivity. Thus, based on the results of our pilot study, it appears that short-term RAPA treatment can be used safely in older persons who are otherwise healthy; a trial with a larger sample size and longer treatment duration is warranted.

Evaluation of the antidepressant therapeutic potential of isocyanine and pseudoisocyanine analogues of the organic cation decynium-22

Herein we describe the synthesis and evaluation of antidepressant properties of seven analogues (1-7) of the low affinity/high capacity transporter blocker decynium-22 (D-22). All analogues (1-7) were synthesized via base promoted coupling reactions between N-alkylated-2-methylquinolinium iodides or N-alkylated-4-methylquinolinium iodides and electrophilic N-alkylated-2-iodoquinolinium iodides. All final compounds were purified by re-crystallization or preparative HPLC and initial evaluation studies included; 1) screening for in vitro α1-adrenoceptor activity (a property that can lead to unwanted side-effects), 2) measuring antidepressant-like activity in a mouse tail suspension test (TST), and 3) measuring effects upon mouse locomotion. The results showed some analogues have lower affinities at α1-adrenoceptors compared to D-22 and showed antidepressant-like activity without the need for co-administration of SSRIs. Additionally, many analogues did not affect mouse locomotion to the same extent as D-22. Plans for additional evaluations of these promising analogues, including measurement of antidepressant-like activity with co-administration of selective serotonin re-uptake inhibitors (SSRIs), are outlined.

Effects of local and spinal administrations of mu-opioids on postoperative pain in aged versus adult mice

Introduction

Suboptimal management of postoperative pain leads to increased risk of chronic opioid therapy, especially in elderly patients.

Objectives

Although this age-dependent phenomenon has been observed clinically, basic mechanisms including baseline nociception, postoperative hypersensitivity, and mu-opioid efficiency in aged animals have never been evaluated.

Methods

We tested these criteria using incision model on adult (3–6 months) and aged (24 months) mice to assess translatability of postoperative animal studies to clinical observations.

Results

Thermal and mechanical testing revealed lower baseline nociception in aged vs adult mice, while behavioral assays after hind paw plantar incision showed similar hypersensitivity levels for both age groups. Efficiency of local and spinal mu-opioid injections on postoperative pain was assessed next. DAMGO, a pure mu-opioid, was effective in reducing postoperative hypersensitivity in aged and adult mice, although adult mice displayed increased sensitivity to higher doses (50 μg local; 1–15 μg spinal). Buprenorphine, a mixed mu-opioid agonist, produced dose-dependent antihypersensitivity with adult mice more sensitive to lower doses (0.1 μg local; 0.02 μg spinal), and aged mice more sensitive to higher doses (1, 10 μg local; 0.1, 1 μg spinal). Finally, exploratory locomotor activity was used to evaluate the suppression of incision-induced spontaneous pain by DAMGO. Spinal and systemic (intraperitoneal) DAMGO inhibited ongoing pain more in adults compared with aged mice.

Conclusion

As in humans, baseline nociception was lower in aged vs adult mice, while postoperative hypersensitivity magnitudes were comparable between groups. Unlike in humans, adult mice were more sensitive to mu-opioids, although higher doses of mixed mu-opioids were more effective for postoperative antihypersensitivity in aged mice.

Ontogeny of Norepinephrine Transporter Expression and Antidepressant-Like Response to Desipramine in Wild-Type and Serotonin Transporter Mutant Mice

Depression is a major public health concern with symptoms that are often poorly controlled by treatment with common antidepressants. This problem is compounded in juveniles and adolescents, because therapeutic options are limited to selective serotonin reuptake inhibitors (SSRIs). Moreover, therapeutic benefits of SSRIs are often especially limited in certain subpopulations of depressed patients, including children and carriers of low-expressing serotonin transporter (SERT) gene variants. Tricyclic antidepressants (TCAs) offer an alternative to SSRIs; however, how age and SERT expression influence antidepressant response to TCAs is not understood. We investigated the relation between antidepressant-like response to the TCA desipramine using the tail suspension test and saturation binding of [³H]nisoxetine to the norepinephrine transporter (NET), the primary target of desipramine, in juvenile (21 days postnatal [P21]), adolescent (P28), and adult (P90) wild-type (SERT+/+) mice. To model carriers of low-expressing SERT gene variants, we used mice with reduced SERT expression (SERT+/-) or lacking SERT (SERT-/-). The potency and maximal antidepressant-like effect of desipramine was greater in P21 mice than in P90 mice and was SERT genotype independent. NET expression decreased with age in the locus coeruleus and increased with age in several terminal regions (e.g., the cornu ammonis CA1 and CA3 regions of the hippocampus). Binding affinity of [³H]nisoxetine did not vary as a function of age or SERT genotype. These data show age-dependent shifts for desipramine to produce antidepressant-like effects that correlate with NET expression in the locus coeruleus and suggest that drugs with NET-blocking activity may be an effective alternative to SSRIs in juveniles.

Ontogeny of SERT Expression and Antidepressant-like Response to Escitalopram in Wild-Type and SERT Mutant Mice

Depression is a disabling affective disorder for which the majority of patients are not effectively treated. This problem is exacerbated in children and adolescents for whom only two antidepressants are approved, both of which are selective serotonin reuptake inhibitor (SSRIs). Unfortunately SSRIs are often less effective in juveniles than in adults; however, the mechanism(s) underlying age-dependent responses to SSRIs is unknown. To this end, we compared the antidepressant-like response to the SSRI escitalopram using the tail suspension test and saturation binding of [(3)H]citalopram to the serotonin transporter (SERT), the primary target of SSRIs, in juvenile [postnatal day (P)21], adolescent (P28), and adult (P90) wild-type (SERT+/+) mice. In addition, to model individuals carrying low-expressing SERT variants, we studied mice with reduced SERT expression (SERT+/-) or lacking SERT (SERT-/-). Maximal antidepressant-like effects were less in P21 mice relative to P90 mice. This was especially apparent in SERT+/- mice. However, the potency for escitalopram to produce antidepressant-like effects in SERT+/+ and SERT+/- mice was greater in P21 and P28 mice than in adults. SERT expression increased with age in terminal regions and decreased with age in cell body regions. Binding affinity values did not change as a function of age or genotype. As expected, in SERT-/- mice escitalopram produced no behavioral effects, and there was no specific [(3)H]citalopram binding. These data reveal age- and genotype-dependent shifts in the dose-response for escitalopram to produce antidepressant-like effects, which vary with SERT expression, and may contribute to the limited therapeutic response to SSRIs in juveniles and adolescents.

Antidepressant-like effects and basal immobility depend on age and serotonin transporter genotype

Monoamine uptake inhibitors are common treatments for depression; however, the therapeutic efficacy of these drugs varies widely. Two factors that are commonly linked to clinical outcome are age and serotonin transporter (SERT) genotype. Mouse models provide powerful tools to study consequences of age and genotype on antidepressant-like efficacy; however, to date, systematic studies of this nature are lacking. Here, we used the tail suspension test (TST), a preclinical assay for antidepressant efficacy, to gain insight into age and SERT genotype dependency of immobility time in the TST under control conditions (saline injection) and in response to the tricyclic antidepressant, desipramine (DMI). Immobility after saline injection in juvenile, adolescent, adult, mature adult and middle-aged mice (postnatal days 21, 28, 90, 210 and 300, respectively) significantly increased with age; however, the rate of increase was slower for SERT null (-/-) mice than for wild-type (+/+) or heterozygote (+/-) mice. Desipramine reduced immobility across ages and SERT genotypes. Middle-aged, but not adult, SERT(-/-) mice were significantly more sensitive to DMI than age-matched SERT(+/+) or SERT(+/-) mice. Desipramine was less potent in middle-aged SERT(+/+) and SERT(+/-) mice than in adult SERT(+/+) or SERT(+/-) mice. Regardless of age, DMI's maximal effects were greater in SERT(-/-) mice than in SERT(+/+) or SERT(+/-) mice. These results show that immobility time in the TST varies as a function of age and SERT genotype, underscoring the utility of the TST as a potential model to examine age- and SERT genotype-dependent influences on antidepressant response.

Effects of nicotine in combination with drugs described as positive allosteric nicotinic acetylcholine receptor modulators in vitro: discriminative stimulus and hypothermic effects in mice

Some drugs that are positive allosteric nAChR modulators in vitro, desformylflustrabromine (dFBr), PNU-120596 and LY 2087101, have not been fully characterized in vivo. These drugs were examined for their capacity to share or modify the hypothermic and discriminative stimulus effects of nicotine (1mg/kg s.c.) in male C57Bl/6J mice. Nicotine, dFBr, and PNU-120596 produced significant hypothermia, whereas LY 2087101 (up to 100mg/kg) did not. Nicotine dose-dependently increased nicotine-appropriate responding and decreased response rate; the respective ED50 values were 0.56mg/kg and 0.91mg/kg. The modulators produced no more than 38% nicotine-appropriate responding up to doses that disrupted operant responding. Rank order potency was the same for hypothermia and rate-decreasing effects: nicotine>dFBr>PNU-120596=LY 2087101. Mecamylamine and the α4β2 nAChR antagonist dihydro-β-erythroidine, but not the α7 antagonist methyllycaconitine, antagonized the hypothermic effects of nicotine. In contrast, mecamylamine did not antagonize the hypothermic effects of the modulators. The combined discriminative stimulus effects of DFBr and nicotine were synergistic, whereas the combined hypothermic effects of nicotine with either dFBr or PNU-120596 were infra-additive. PNU-120596 did not modify the nicotine discriminative stimulus, and LY 2087101 did not significantly modify either effect of nicotine. Positive modulation of nicotine at nAChRs by PNU-120596 and LY 2087101 in vitro does not appear to confer enhancement of the nAChR-mediated hypothermic or discriminative stimulus effects of nicotine. However, dFBr appears to be a positive allosteric modulator of some behavioral effects of nicotine at doses of dFBr smaller than the doses producing unwanted effects (e.g. hypothermia) through non-nAChR mechanisms.

Cross-tolerance to cannabinoids in morphine-tolerant rhesus monkeys

RATIONALE

Opioids remain the drugs of choice for treating moderate to severe pain, although adverse effects limit their use. Therapeutic utility might be improved by combining opioids with other drugs to enhance analgesic effects, but only if adverse effects are not similarly changed.

OBJECTIVE

Cannabinoids have been shown to enhance the antinociceptive potency of opioids without increasing other effects; this study examined whether the effectiveness of cannabinoids is altered in morphine-dependent monkeys.

METHODS

Four monkeys received up to 10 mg/kg morphine twice daily. Changes in the antinociceptive effects of opioid receptor agonists (morphine, U50,488) and cannabinoid receptor agonists (WIN 55,212, CP 55,940, and Δ(9)-tetrahydrocannabinol [THC]) were determined by measuring the latency for monkeys to remove their tails from 40, 50, 54, and 58 °C water.

RESULTS

Before treatment, all drugs increased tail withdrawal latency from warm (54 °C) water. Chronic morphine treatment decreased the potency of each drug; the magnitude of rightward shift in dose-effect curves was greatest for morphine, WIN 55,212 and CP 55,940 with at least sixfold shifts for each drug during treatment. Discontinuation of morphine treatment resulted in signs that are indicative of withdrawal, including increased heart rate, decreased daytime activity, and tongue movement.

CONCLUSION

Tolerance developed to the antinociceptive effects of morphine and cross-tolerance developed to cannabinoids under conditions that produced modest physical dependence. Compared with the doses examined in this study, much smaller doses of opioids have antinociceptive effects when given with cannabinoids; it is possible that tolerance will not develop to chronic treatment with opioid/cannabinoid mixtures.

Effects of consuming a diet high in fat and/or sugar on the locomotor effects of acute and repeated cocaine in male and female C57BL/6J mice

Drug abuse and obesity are serious public health problems. Dopamine plays a central role in mediating the reinforcing effects of drugs and food. Prolonged use of drugs is known to alter the function and/or sensitivity of many neurotransmitter systems, including dopamine; however, the impact of consuming foods high in fat and/or sugar is less clear. These studies characterized the locomotor effects of acute and repeated cocaine in male and female C57BL/6J mice consuming 1 of 4 diets: (a) standard chow + water; (b) standard chow + 10% sucrose solution; (c) high-fat chow + water; or (d) high-fat chow + 10% sucrose solution. The acute locomotor effects of cocaine (3.2-32.0 mg/kg) were evaluated 4 weeks after initiating dietary conditions; the effects of repeated cocaine administration were evaluated after 5, 6, 7, and 12 weeks. During acute tests, mice consuming a diet high in fat and/or sucrose exhibited greater locomotor responses to cocaine than mice consuming standard chow and water, regardless of sex. Although diet-induced enhancements persisted across repeated cocaine testing, locomotor sensitization developed more rapidly in females drinking sucrose (and consuming either standard or high-fat chow) than in females consuming standard chow and water. In addition to providing evidence that consuming a diet high in fat and/or sugar enhances abuse-related effects of cocaine in ways that might increase vulnerability to abuse cocaine, these studies identified a potentially important sex-related difference in the interaction between nutrition and cocaine effects, with the impacts of sucrose consumption being greater in females than in males.

Drinking sucrose or saccharin enhances sensitivity of rats to quinpirole-induced yawning

Diet can impact sensitivity of rats to some of the behavioral effects of drugs acting on dopamine systems. The current study tested whether continuous access to sucrose is necessary to increase yawning induced by the dopamine receptor agonist quinpirole, or if intermittent access is sufficient. These studies also tested whether sensitivity to quinpirole-induced yawning increases in rats drinking the non-caloric sweetener saccharin. Dose-response curves (0.0032-0.32 mg/kg) for quinpirole-induced yawning were determined once weekly in rats with free access to standard chow and either continuous access to water, 10% sucrose solution, or 0.1% saccharin solution, or intermittent access to sucrose or saccharin (i.e., 2 days per week with access to water on other days). Cumulative doses of quinpirole increased then decreased yawning, resulting in an inverted U-shaped dose-response curve. Continuous or intermittent access to sucrose enhanced sensitivity to quinpirole-induced yawning. Continuous, but not intermittent, access to saccharin also enhanced sensitivity to quinpirole-induced yawning. In all groups, pretreatment with the selective D3 receptor antagonist PG01037 shifted the ascending limb of the quinpirole dose-response curve to the right, while pretreatment with the selective D2 receptor antagonist L-741,626 shifted the descending limb to the right. These results suggest that even intermittent consumption of diets containing highly palatable substances (e.g. sucrose) alters sensitivity to drugs acting on dopamine systems in a manner that could be important in vulnerability to abuse drugs.

Physiological and behavioral effects of amphetamine in BACE1(-/-) mice

β-Site APP-cleaving Enzyme 1 (BACE1) is a protease that has been linked to schizophrenia, a severe mental illness that is potentially characterized by enhanced dopamine (DA) release in the striatum. Here, we used acute amphetamine administration to stimulate neuronal activity and investigated the neurophysiological and locomotor-activity response in BACE1-deficient (BACE1(-/-) ) mice. We measured locomotor activity at baseline and after treatment with amphetamine (3.2 and 10 mg/kg). While baseline locomotor activity did not vary between groups, BACE1(-/-) mice exhibited reduced sensitivity to the locomotor-enhancing effects of amphetamine. Using high-performance liquid chromatography (HPLC) to measure DA and DA metabolites in the striatum, we found no significant differences in BACE1(-/-) compared with wild-type mice. To determine if DA neuron excitability is altered in BACE1(-/-) mice, we performed patch-clamp electrophysiology in putative DA neurons from brain slices that contained the substantia nigra. Pacemaker firing rate was slightly increased in slices from BACE1(-/-) mice. We next measured G protein-coupled potassium currents produced by activation of D2 autoreceptors, which strongly inhibit firing of these neurons. The maximal amplitude and decay times of D2 autoreceptor currents were not altered in BACE1(-/-) mice, indicating no change in D2 autoreceptor-sensitivity and DA transporter-mediated reuptake. However, amphetamine (30 µm)-induced potassium currents produced by efflux of DA were enhanced in BACE1(-/-) mice, perhaps indicating increased vesicular DA content in the midbrain. This suggests a plausible mechanism to explain the decreased sensitivity to amphetamine-induced locomotion, and provides evidence that decreased availability of BACE1 can produce persistent adaptations in the dopaminergic system.

Antidepressant-like drug effects in juvenile and adolescent mice in the tail suspension test: Relationship with hippocampal serotonin and norepinephrine transporter expression and function

Depression is a major health problem for which most patients are not effectively treated. This problem is further compounded in children and adolescents where only two antidepressants [both selective serotonin reuptake inhibitors (SSRIs)] are currently approved for clinical use. Mouse models provide tools to identify mechanisms that might account for poor treatment response to antidepressants. However, there are few studies in adolescent mice and none in juvenile mice. The tail suspension test (TST) is commonly used to assay for antidepressant-like effects of drugs in adult mice. Here we show that the TST can also be used to assay antidepressant-like effects of drugs in C57Bl/6 mice aged 21 (juvenile) and 28 (adolescent) days post-partum (P). We found that the magnitude of antidepressant-like response to the SSRI escitalopram was less in P21 mice than in P28 or adult mice. The smaller antidepressant response of juveniles was not related to either maximal binding (B_max) or affinity (K_d) for [³H]citalopram binding to the serotonin transporter (SERT) in hippocampus, which did not vary significantly among ages. Magnitude of antidepressant-like response to the tricyclic desipramine was similar among ages, as were B_max and K_d values for [³H]nisoxetine binding to the norepinephrine transporter in hippocampus. Together, these findings suggest that juvenile mice are less responsive to the antidepressant-like effects of escitalopram than adults, but that this effect is not due to delayed maturation of SERT in hippocampus. Showing that the TST is a relevant behavioral assay of antidepressant-like activity in juvenile and adolescent mice sets the stage for future studies of the mechanisms underlying the antidepressant response in these young populations.