Sphenopalatine Ganglion Stimulation to Augment Cerebral Blood Flow

Background and Purpose—

Many patients with acute ischemic stroke are not eligible for thrombolysis or mechanical reperfusion therapies due to contraindications, inaccessible vascular occlusions, late presentation, or large infarct core. Sphenopalatine ganglion (SPG) stimulation to enhance collateral flow and stabilize the blood-brain barrier offers an alternative, potentially more widely deliverable, therapy.

Methods—

In a randomized, sham-controlled, double-masked trial at 41 centers in 7 countries, patients with anterior circulation ischemic stroke not treated with reperfusion therapies within 24 hours of onset were randomly allocated to active SPG stimulation or sham control. The primary efficacy outcome was improvement beyond expectations on the modified Rankin Scale of global disability at 90 days (sliding dichotomy), assessed in the modified intention-to-treat population. The initial planned sample size was 660 patients, but the trial was stopped early when technical improvements in device placement occurred, so that analysis of accumulated experience could be conducted to inform a successor trial.

Results—

Among 303 enrolled patients, 253 received at least one active SPG or sham stimulation, constituting the modified intention-to-treat population (153 SPG stimulation and 100 sham control). Age was median 73 years (interquartile range, 64–79), 52.6% were female, deficit severity on the National Institutes of Health Stroke Scale was median 11 (interquartile range, 9–15), and time from last known well median 18.6 hours (interquartile range, 14.5–22.5). For the primary outcome, improved 3-month disability beyond expectations, rates in the SPG versus sham treatment groups were 49.7% versus 40.0%; odds ratio, 1.48 (95% CI, 0.89–2.47); P =0.13. A significant treatment interaction with stroke location (cortical versus noncortical) was noted, P =0.04. In the 87 patients with confirmed cortical involvement, rates of improvement beyond expectations were 50.0% versus 27.0%; odds ratio, 2.70 (95% CI, 1.08–6.73); P =0.03. Similar response patterns were observed for all prespecified secondary efficacy outcomes. No differences in mortality or serious adverse event safety end points were observed.

Conclusions—

SPG stimulation within 24 hours of onset is safe in acute ischemic stroke. SPG stimulation was not shown to statistically significantly improve 3-month disability above expectations, though favorable outcomes were nominally higher with SPG stimulation. Beneficial effects may distinctively be conferred in patients with confirmed cortical involvement. The results of this study need to be confirmed in a larger pivotal study.

Clinical Trial Registration—

URL: https://www.clinicaltrials.gov . Unique identifier: NCT03767192.

Emergent Cranial Computed Tomography in the Evaluation of Adult Non-Trauma Patients in the Emergency Department

Objectives

To study the utilisation pattern of head computed tomography (CT) for non-trauma adult cases in an urban emergency department (ED) and the rate of clinically significant CT abnormalities. We also tried to identify any useful clinical indicators that could be used to predict abnormal scans.

Methodology

A one-year case series of adult non-trauma cranial CT scans ordered in an urban ED was studied. Patients less than 16 years old, with CT head done prior to presentation and/or attendance precipitated by trauma were excluded. Logistic regression was used to identify significant predictors for abnormal scans. Clinical indicators that were studied included age, altered mental status (AMS), headache and vomiting, elevated blood pressure, previous history of hypertension, Glasgow Coma Scale (GCS) and presence of focal neurological sign (FNS).

Results

183 adult non-trauma cranial CT scans were included in the study, and 109 (59.6%) CT scans revealed clinically significant abnormalities. Only AMS and FNS were found to be statistically significant in predicting abnormal scans. Patients with AMS had a 2.5 times (95% CI: 1.1 to 5.8) higher odds for an abnormal scan compared to those without AMS, adjusting for FNS. Patients with FNS had adjusted odds of 8.9 (95% CI: 4.2 to 18.8).

Conclusion

This study reports a high (59.6%) rate of abnormal adult non-trauma cranial CT compared with previous studies. Altered mental status and the presence of focal neurological sign are significant predictors for an abnormal scan. They should serve as useful criteria when devising utilisation strategies for emergency non-trauma cranial CT in future studies.

Cross-bridged macrocyclic chelators for stable complexation of copper radionuclides for PET imaging

Copper-64 (t(1/2)=12.7 h; beta+: 17.4%; E(beta+max)=656 keV; beta-: 39%; E(beta-max)=573 keV) has emerged as an important non-standard positron-emitting radionuclide for positron emission tomography imaging of diseased tissues. A significant challenge of working with copper radionuclides is that they must be delivered to the living system as a stable complex that is attached to a biological targeting molecule for effective imaging and therapy. Significant research has been devoted to the development of ligands that can stably chelate (64)Cu, in particular, the cross-bridged (CB) macrocyclic chelators. This review describes the coordination chemistry and biological behavior of (64)Cu-labeled CB complexes.

Copper chelation chemistry and its role in copper radiopharmaceuticals

Molecular imaging is an important scientific discipline that plays a major role in clinical medicine and pharmaceutical development. While several imaging modalities including X-ray computed tomography (CT) and magnetic resonance imaging (MRI) generate high-resolution anatomical images, positron emission tomography (PET) and single photon emission computed tomography (SPECT) offer insight into the physiological processes that occur within a living organism. Of these two nuclear medicine imaging techniques, PET has advantages with respect to sensitivity and resolution, and this has led to the production and development of many positron emitting radionuclides that include non-traditional radionuclides of the transition metals. Copper-64 (t(1/2) = 12.7 h, beta(+): 17.4%, E(beta+max) = 656 keV; beta(-): 39%, E(beta-max) = 573 keV) has emerged as an important positron emitting radionuclide that has the potential for use in diagnostic imaging and radiotherapy. However, (64)Cu must be delivered to the living system as a stable complex that is attached to a biological targeting molecule for effective imaging and therapy. Therefore, significant research has been devoted to the development of ligands that can stably chelate (64)Cu. This review discusses the necessary characteristics of an effective (64)Cu chelator, while highlighting the development and evaluation of (64)Cu-complexes attached to biologically-targeted ligands.

Predictors of serious bacterial infection in children aged 3 to 36 months with fever without source

INTRODUCTION

Children commonly present with fever without source yet there is no reliable and consistent method of identifying those at risk of serious bacterial infection. In this study, we sought to identify predictors of serious bacterial infection in children aged between three to 36 months with fever without source.

METHODS

Inpatient records of all children aged three to 36 months admitted from the Emergency Department of Singapore's main paediatric hospital between October 2001 to February 2002 with International Classification of Diseases (ninth revision) diagnosis codes 038 (septicaemia), 079 (viral fever), or 780 (pyrexia of unknown origin), were retrieved and reviewed. Patients identified as having fever without source were enrolled.

RESULTS

Of 86 enrolled children, 17 (19.8 percent) had serious bacterial infection. Duration of fever and white blood cell count were found to be significant predictors. Children with white blood cell count equal to or greater than 16,000/cubic mm had 6.9 times (95 percent confidence interval [CI] is 1.7 to 28.4) increased risk of serious bacterial infection, while children with fever of duration exceeding three days before presentation had 3.8 times (95 percent CI is 1.1 to 13.1) increased risk of serious bacterial infection. A combination of white blood cell count less than 16,000/cubic mm and duration of fever three days or less had a negative predictive value of 1.0 (95 percent CI is 0.88 to 1.0) and a sensitivity of 1.0 (95 percent CI is 0.82 to 1.0).

CONCLUSION

The two identified predictors offer an estimate of the risk of serious bacterial infection in children aged three to 36 months with fever without source.

Faecal prevalence of extended-spectrum Beta-lactamase (ESBL)-producing coliforms in a geriatric population and among haematology patients

Antimicrobial resistance to the extended-spectrum cephalosporins is increasingly reported worldwide. In the local setting, nosocomial infections with multi-resistant Gram-negative bacilli are not uncommon and are a growing concern. However, there is limited data on the carriage rates of such organisms in the local setting. In May 2001, a prospective study was carried out to determine the enteric carriage rates of ceftazidime-resistant Gram negative bacilli (CAZ-R GNB) among residents of nursing homes and from in-patients of the geriatric and adult haematology wards of University Malaya Medical Centre. Ceftazidime-resistant Gram-negative bacilli (CAZ-R GNB) were detected in 25 samples (30%), out of which 6 were from nursing home residents, 5 from geriatric in-patients and 14 from the haematology unit. A total of 28 CAZ-R GNB were isolated and Escherichia coli (10) and Klebsiella pneumoniae (7) were the predominant organisms. Resistance to ceftazidime in E. coli and Klebsiella was mediated by extended-spectrum beta-lactamases (ESBLs). Although the majority of the CAZ-R GNB were from patients in the haematology ward, the six nursing home residents with CAZ-R GNB were enteric carriers of ESBL-producing coliforms. Prior exposure to antibiotics was associated with carriage of ESBL organisms and to a lesser extent, the presence of urinary catheters.

Adjuvant sequential chemotherapy and radiotherapy in uterine papillary serous carcinoma

PURPOSE

To evaluate the efficacy and toxicity of adjuvant combination of sequential chemotherapy followed by radiotherapy in uterine papillary serous carcinoma (UPSC).

METHODS AND MATERIALS

From April 1994 to June 2003, 26 patients (median age 61.7 years, range 46.9-78.4) with UPSC were treated with a platinum-based chemoradiation protocol after definitive surgery. 9 patients were assigned as stage I (35%), 4 were stage II (15%), 11 were stage III (42%), and 2 were stage IV (8%) according to the FIGO staging for gynecological cancers. All patients underwent total hysterectomy, salpingo-oophorectomy, pelvic +/- perioartic lymph nodes dissection/sampling, omentectomy, and peritoneal washing. The adjuvant chemoradiation protocol consists of 4 cycles of platinum-based chemotherapy followed by pelvic irradiation and vaginal vault brachytherapy. In selected stage I patients with no or minimal myometrial invasion, only vault brachytherapy was given after adjuvant chemotherapy.

RESULTS

After a median follow-up of 28 months (range 9-113 months), 14 (54%) patients were alive and free of disease. 12 out of these 14 patients were FIGO stage I/II. 9 patients (35%) had died (8 from distant metastases). The Kaplan-Meier 2-year and 5-year survival estimates were 69.5% and 57%, respectively. Only 4 (15%) patients had pelvic recurrence. None of the patients developed local vault recurrence. The treatment was well tolerated, only 1 patient developed congestive cardiac failure from the chemotherapy and 6 patients had grade 2 peripheral neuropathy on follow-up.

CONCLUSION

In our series of UPSC patients treated with adjuvant chemotherapy followed by radiotherapy, local control can be achieved in a majority of patients. Distant failure remains the major cause of mortality. Further investigations into finding a more effective systemic therapy are required if improvement in outcome for this form of uterine cancer is to be achieved.

Breath-hold fast recovery fast spin echo versus conventional non-breath-hold fast spin echo T2-weighted MR imaging of focal liver lesions

INTRODUCTION

We compare the breath-hold fast recovery fast spin echo (BHFRFSE) T2-weighted and non-breath-hold fast spin echo (NBHFSE) T2-weighted sequences in image quality and lesion characterisation of focal liver lesions.

MATERIALS AND METHODS

Fat-suppressed T2-weighted magnetic resonance (MR) images obtained with the 2 sequences (BHFRFSE and NBHFSE) in 79 patients with 113 liver lesions were analysed retrospectively. The image quality and nature of the lesions were evaluated by 2 experienced radiologists.

RESULTS

Based on receiver operating characteristic curve analysis, lesion characterisation was comparable for both sequences. The image quality of BHFRFSE was significantly better than that of NBHFSE. The NBHFSE missed 4 malignant lesions while BHFRFSE missed 2 malignant lesions.

CONCLUSION

BHFRFSE performs similarly to NBHFSE in image quality and liver lesion characterisation.

Heterocyclic excitatory amino acids. Synthesis and biological activity of novel analogs of AMPA

The novel acidic amino acids 6a-c, 7, and 8 have been synthesized via 1,3-dipolar cycloadditions, using nitrile oxides and alkynes. The prepared compounds are heterocyclic analogues of glutamic acid with differing chain lengths. One of these compounds, (RS)-2-amino-3-(3-carboxy-5-methyl-4- isoxazolyl)propionic acid (ACPA, 8), was shown in [3H]AMPA binding studies to be more active than AMPA itself (IC50 = 20 nM compared to IC50 = 79 nM for AMPA). No affinity for NMDA receptors (NMDA-sensitive [3H]glutamic acid binding) was found, and only weak affinity in [3H]kainic acid binding (IC50 = 6.3 microM) was detected. The excitatory activity in rat cortical wedge also showed that ACPA was more potent than AMPA (EC50 = 1.0 microM compared to EC50 = 3.5 microM for AMPA). The depolarizing effect of ACPA could be fully antagonized by the selective non-NMDA antagonist 6-cyano-7-nitro-quinoxazoline-2,3-dione (CNQX), but was unaffected by the selective NMDA antagonist D-2-amino-5-phosphonovaleric acid (AP5).

Intrinsic motivation among regular, special, and alternative education high school students

This study examined motivationally related variables among three types of high school students. In particular, students' perceptions of competence, control, parental autonomy support, teacher autonomy support, peer autonomy support, and academic coping were investigated. Two hundred fifty-one juniors and seniors (104 regular education, 93 alternative education, and 54 special education) from a large Southern California school district participated. Significant group differences were found on measures of perceived competence, academic coping, and parental autonomy support. Specifically, regular education students had a higher level of self-reported academic competence than did special education students. Further, regular education and special education students reported that their parents were more involved in their lives as compared with alternative education students. Finally, regular education students reported a higher level of academic anxiety than did special education and alternative education students; however, regular education students had the highest level of positive coping. The implications of these findings are discussed.

Deep cerebral infarcts extending to the subinsular region

BACKGROUND AND PURPOSE

We sought to determine the clinical and radiological features and pathogenesis of deep cerebral infarcts extending to the subinsular region (DCIs).

METHODS

- We defined DCIs as subcortical infarcts extending between the lateral ventricle and the subinsular region with a paraventricular extent >1.5 cm and a subinsular extent of at least one third of the anteroposterior extent of the insula. We identified patients by review of imaging records and noted the clinical information, risk factors, and investigations. We compared risk factors and clinical features between DCIs and "internal border zone" infarcts restricted to the paraventricular region.

RESULTS

- Eight patients were studied. The typical clinical features of DCIs were hemiparesis, aphasia, dysarthria, and dysphagia. Aphasia was seen in 3 of 5 patients with left-sided infarcts. Six of 8 patients (75%) had hypoperfusion as a possible pathogenetic factor (carotid occlusion in 4, surgical clipping of MCA in 1, low ejection fraction in 1), and 3 patients (38%) had cardioembolism as a possible pathogenetic factor (atrial fibrillation in 2, low ejection fraction in 1). One patient (12%) had no cause for stroke. Clinical features were similar to those for paraventricular infarcts. Carotid occlusion was more frequent (P=0.04), and there was a trend toward a higher frequency of hypertension (P<0.1) and smoking with DCIs than with paraventricular infarcts. DCIs were located in a deep vascular border zone.

CONCLUSIONS

- The clinical features and pathogenesis of DCIs overlap with those of internal border zone paraventricular infarcts. Hypoperfusion may give rise to DCIs since large-artery occlusion is their main risk factor. The larger size of DCIs compared with paraventricular infarcts may relate to a poorer collateral blood supply.

Is second-order spatial loss in amblyopia explained by the loss of first-order spatial input?

The purpose of the study was to determine whether amblyopes show detection loss for second-order spatial information, and if present, whether the loss is explained by the loss of first-order spatial input. We psychophysically determined detection thresholds for the amblyopic and non-amblyopic eyes of five adult amblyopes and the dominant eyes of three control observers. We found that four amblyopic eyes and two non-amblyopic eyes showed second-order loss relative to the control eyes. The second-order loss was greater than the first-order loss at the carrier spatial frequency (first-order input). The extra second-order loss indicates an early amplification of cortical neural loss that we speculate is due to deficient binocular input to second-order neurons.

Common discriminative stimulus properties in rats of muscarinic antagonists, clozapine and the D3 preferring antagonist PNU-99194a: an analysis of possible mechanisms

Dopamine D3 receptors have been implicated in the aetiology of schizophrenia and the actions of antipsychotic drugs. The initial studies reported here assessed the involvement of such receptors in the in vivo actions of the atypical antipsychotic clozapine and the putative D3-preferring antagonist PNU-99194A in drug discrimination assays. Rats trained to discriminate clozapine consistently generalized to PNU-99194A in two separate studies. However, four other putative D3-preferring antagonists (PD 152255, (+)-S14297, nafadotride and (+)-AJ 76) did not induce generalization to clozapine. In rats trained to discriminate PNU-99194A, which has been suggested to induce a stimulus mediated specifically by D3 antagonism, the D3-preferring antagonist (+)-UH 232 and clozapine both induced full generalization. However, the PNU-99194A-trained animals also generalized fully to the muscarinic antagonists scopolamine and trihexyphenidyl. A possible explanation for the symmetrical generalization observed between clozapine and PNU-99194A is that these drugs have common muscarinic antagonist actions, since muscarinic antagonists have been reported to substitute for clozapine in numerous prior studies. However, in vitro receptor binding studies with M1-M5 receptors indicated that (with the possible exception of the M4 receptor), no muscarinic receptor subtype had high affinity for both clozapine, PNU-99194A and scopolamine. In addition, other binding studies indicated that whereas clozapine and PNU-99194A had high affinity for the D3 receptor, scopolamine did not. It is therefore concluded that: (1) The generalization seen between clozapine, PNU-99194A and muscarinic antagonists may be mediated by common effects 'downstream' from either muscarinic or D3 receptors; (2) D3 antagonism does not play a critical role in the clozapine stimulus (since D3-preferring antagonists did not consistently induce generalization to clozapine); (3) although D3 antagonism plays a role in the PNU-91994A stimulus (since the D3-preferring antagonist (+)-UH 232 induced full generalization, in accord with results from prior studies with other D3-preferring antagonists, the PNU-99194A stimulus also has commonalities with that induced by muscarinic antagonists and clozapine. The in vivo differences observed between PNU-99194A and other D3-preferring antagonists should be borne in mind when this agent is used as a tool to study D3 receptor functioning in vivo. The similarities between the PNU-99194A and clozapine stimuli suggest tentatively that compounds with a profile like PNU-99194A may have antipsychotic actions similar to clozapine. Some preclinical data are suggestive of such effects of PNU-99194A.

Rational design and assembly of M(2)M'(3)L(6) supramolecular clusters with C(3h) symmetry by exploiting incommensurate symmetry numbers

A rational approach to heterometallic cluster formation is described that uses incommensurate symmetry requirements at two different metals to control the stoichiometry of the assembly. Critical to this strategy is the proper design and synthesis of hybrid ligands with coordination sites selective toward each metal. The phosphino-catechol ligand 4-(diphenylphosphino)benzene-1,2-diol (H(2)L) possesses both hard catecholate and soft phosphine donor sites and serves such a role, using soft (C(2)-symmetric) and hard (C(3)-symmetric) metal centers. The ML(3) catecholate complexes (M = Fe(III), Ga(III), Ti(IV), Sn(IV)) have been prepared and characterized as C(3)-symmetry precursors for the stepwise assembly (aufbau) of heterometallic clusters. While the single-crystal X-ray structure of the Cs(2)[TiL(3)] salt shows a C(1) mer-configuration in the solid -state, room-temperature solution NMR data of this and related complexes are consistent with either exclusive formation of the C(3)-fac-isomer with all PPh(2) donor sites syn to each other or facile fac/mer isomerization. Coordination of these [ML(3)](2)(-) (M = Ti(IV), Sn(IV)) metallaligands via their soft P donor sites to C(2)-symmetric PdBr(2) units gives exclusively pentametallic [M(2)Pd(3)Br(6)L(6)](4)(-) (M = Ti, Sn) clusters. These clusters have been fully characterized by spectral and X-ray structural data as C(3h) mesocates with Cs(+) or protonated 1,4-diazabicyclo[2.2.2]octane (DABCO.H(+)) cations incorporated into deep molecular clefts. Exclusive formation of this type of supramolecular species is sensitive to the nature of the counterions. Alkali cations such as K(+), Rb(+), and Cs(+) give high-yield formation of the respective clusters while NEt(3)H(+) and NMe(4)(+) yield none of the desired products. Extension of the aufbau assembly to produce related [M(2)Pd(3)Cl(6)L(6)](4)(-), [M(2)Pd(3)I(6)L(6)](4)(-), and [M(2)Cr(3)(CO)(12)L(6)](4)(-) (M = Ti, Sn) clusters has also been realized. In addition to this aufbau approach, self-assembly of several of these [M(2)Pd(3)Br(6)L(6)](4)(-) clusters from all eleven components (two M(IV), three PdBr(2), six H(2)L) was also accomplished under appropriate reaction conditions.

Testing the disinhibition hypothesis of epileptogenesis in vivo and during spontaneous seizures

The "disinhibition" hypothesis contends that (1) seizures begin when granule cells in the dentate gyrus of the dorsal hippocampus are disinhibited and (2) disinhibition occurs because GABAergic interneurons are excessively inhibited by other GABAergic interneurons. We tested the disinhibition hypothesis using the experimental model that inspired it-naturally epileptic Mongolian gerbils. To determine whether there is an excess of GABAergic interneurons in the dentate gyrus of epileptic gerbils, as had been reported previously, GABA immunocytochemistry, in situ hybridization of GAD67 mRNA, and the optical fractionator method were used. There were no significant differences in the numbers of GABAergic interneurons. To determine whether granule cells in epileptic gerbils were disinhibited during the interictal period, IPSPs were recorded in vivo with hippocampal circuits intact in urethane-anesthetized gerbils. The reversal potentials and conductances of IPSPs in granule cells in epileptic versus control gerbils were similar. To determine whether the level of inhibitory control in the dentate gyrus transiently decreases before seizure onset, field potential responses to paired-pulse perforant path stimulation were obtained from the dorsal hippocampus while epileptic gerbils experienced spontaneous seizures. Evidence of reduced inhibition was found after, but not before, seizure onset, indicating that seizures are not triggered by disinhibition in this region. However, seizure-induced depression of inhibition may amplify and promote the spread of seizure activity to other brain regions. These findings do not support the disinhibition hypothesis and suggest that in this model of epilepsy seizures initiate by another mechanism or at a different site.

ATP-sensitive potassium channels in freshly dissociated adult rat striatal neurons: activation by metabolic inhibitors and the dopaminergic receptor agonist quinpirole

The characteristics of adenosine 5'-triphosphate (ATP)-sensitive K+ channels in acutely isolated striatal neurons from adult rats were examined. Neurons had a resting membrane potential of -53.9+/-1.2 mV (n=66), with evoked or spontaneous action potentials firing at 10+/-0.7 Hz, and large inwards and outwards whole-cell currents. In cell-attached patches with a high [K+] in the pipette, a voltage-independent, ATP-insensitive 16.5+/-1.5 pS channel was observed in 375 out of 452 cells. Bath application of Na+-azide (0.5-2 mM) to 108 neurons revealed another 145.7+/-3.5 pS (LKATP) channel in 65 neurons; this channel was blocked by tolbutamide. The LKATP channel exhibited a high open probability (Po, 0.8+/-0.05) at 0 mV pipette potential. Varying the pipette [K+] shifted the reversal potential of LKATP, showing the channel's K+ selectivity. Cytoplasmic ATP (ATPi) reversibly inhibited LKATP, with an inhibitory constant (Ki) of 0.12 mM. LKATP was sensitive to intracellular Ca2+ but insensitive to iberiotoxin. In 25% of cell-attached patches, the presence of quinpirole in the pipette opened a third type of channel (90.6+/-1.7 pS, termed D2KATP). Sulpiride, a dopamine D2-receptor antagonist, inhibited D2KATP. ATPi reversibly inhibited D2KATP, with a Ki of 0.212 mM. The Na+-azide- or quinpirole-induced current caused a tolbutamide-sensitive membrane hyperpolarization and a marked reduction in action potential frequency. We propose that ATP-sensitive K+ channels play a metabolism-dependent role in striatal neurons.

Tonic downward and inward ocular deviation ipsilateral to pontine tegmental hemorrhage

A 61-year-old man presented with coma and left hemiparesis. He was found to have tonic downward and inward deviation of the right eye, and a right lateral gaze palsy. He also had occasional downward bobbing movements of the right eye, and a partial bilateral upgaze paresis. CT showed a right pontine tegmental hemorrhage extending to the ipsilateral midbrain. Tonic ocular downward and inward deviation associated with pontine tegmental hemorrhage may be due to irritation of mesencephalic downgaze and convergence centers by rostral extension of the hematoma. Although 'eyes seeming to peer at the tip of the nose' is characteristic of thalamic hemorrhage, it may also be seen secondary to pontine tegmental hemorrhage.

Reboxetine: a pharmacologically potent, selective, and specific norepinephrine reuptake inhibitor

BACKGROUND

Reboxetine is a potent antidepressant, with efficacy comparable to that of imipramine, desipramine, and fluoxetine, and has improved side-effect profile. The basis of its efficacy and improved tolerability is sought through studies of reboxetine in a number of pharmacological models of depression.

METHODS

Pharmacological selectivity for uptake systems was defined by uptake and binding assays for the three monoamine uptake sites. Specificity was determined in 39 different receptor and 6 enzyme assays. In vivo selectivity was defined by measurement of neuronal firing rates in the locus coeruleus, dorsal raphe, and substantia nigra. Reserpine-induced blepharospasm and hypothermia, clonidine-induced hypothermia, defined reboxetine's in vivo pharmacology. Reboxetine's antidepressant potential was evaluated behaviorally by the tail-suspension test, forced swimming, and the DRL72 operant responding test.

RESULTS

Reboxetine is a potent, selective, and specific norepinephrine reuptake inhibitor (selective NRI) as determined by both in vitro and in vivo measurements. Unlike desipramine or imipramine, reboxetine has weak affinity (Ki > 1,000 nmol/L)for muscarinic, histaminergic H1, adrenergic alpha1, and dopaminergic D2 receptors. In vivo action of reboxetine is entirely consistent with the pharmacological action of an antidepressant with preferential action at the norepinephrine reuptake site. Reboxetine showed an antidepressant profile in all tests of antidepressant activity used. Significant decreases in immobility were observed in the tail suspension test and behavioral despair test. Increased efficiency in responding was observed in the DRL72 test.

CONCLUSIONS

Reboxetine is a potent, selective, and specific noradrenergic reuptake inhibitor. It has a superior pharmacological selectivity to existing tricyclic antidepressants and selective serotonin reuptake inhibitors when tested in a large number of in vitro and in vivo systems. Given the pharmacological profile, reboxetine is expected to be a selective and potent tool for psychopharmacological research. The use of reboxetine in the clinic will also help clarify the role norepinephrine plays in depression.

Nicergoline stimulates protein kinase C mediated alpha-secretase processing of the amyloid precursor protein in cultured human neuroblastoma SH-SY5Y cells

We investigated the ability of the antidementia agents, nicergoline, aniracetam and hydergine to stimulate PKC mediated alpha-secretase amyloid precursor protein (APP) processing in cultured human neuroblastoma SH-SY5Y cells. Western immunoblotting of cell conditioned media using the Mabs 22C11 and 6E10 revealed the presence of 2 bands with molecular mass of 90 and 120 kDa, corresponding to possible alternatively glycosylated forms of secreted APP (APPs). Short-term (30 min and 2 h) treatment of cells with nicergoline gave an increased intensity of both bands, compared to non-treated cells. Maximal nicergoline effects, of the order of 150-200% over basal APPs release, were seen at concentrations between 1 and 10 microM. Under the same condition, 1 microM PdBu, used as a positive control, gave 500-1000% increases of basal APPs release. In contrast, aniracetam and hydergine, did not show any effect on APPs secretion. 2 h treatment with nicergoline had no effect on cellular full-length APP levels, as determined by immunoblotting of cell extracts with 22C11 and CT15 antibodies. Immunoblotting with PKC isoform specific antibodies of soluble and membrane fractions prepared from 2 h treated cells, showed that nicergoline (50 microM) and PdBu (1 microM) both induced translocation of PKC alpha, gamma and epsilon, but not PKC beta. The involvement of PKC in mediating nicergoline stimulated APPs release was also studied using specific inhibitors. 1 microM calphostin C, a broad range PKC inhibitor, significantly reduced both PdBu (1 microM) and nicergoline (10 microM) induced APPs release. In contrast, Go6976 (1 microM), a selective PKC alpha and beta1 inhibitor, as well as the cAMP-dependent protein kinase inhibitor, H89 (1 microM) were without effect. These results indicate that nicergoline can modulate alpha-secretase APP processing by a PKC dependent mechanism that is likely to involve the gamma and epsilon isoforms of this enzyme.

Predictors of global self-worth and academic performance among regular education, learning disabled, and continuation high school students

While academic performance and achievement motivation among elementary school students have received considerable attention, far less is known with respect to adolescents. The primary purpose of this project was to examine the ability of measures of perceived competence, control, and autonomy support to predict self-worth and academic performance with a group of regular education, learning disabled, and continuation high school students. Stepwise regression analyses indicated that indices of perceived competence, control, and autonomy support were significant predictors of self-worth and grade point average. Additionally, school status (i.e., regular education and continuation) and a depression variable were significant predictors in the regression model for academic performance. The results highlight the need for continued empirical investigation into issues surrounding the academic performance and achievement motivation of adolescents.

Enhanced delayed matching performance in younger and older macaques administered the 5-HT4 receptor agonist, RS 17017

Recent evidence indicates that the 5-HT4 subtype of serotonin receptor may modulate central cholinergic activity in regions of the mammalian CNS important to memory such as the frontal cortex, hippocampus and amygdala. These receptors could represent targets for drugs designed for the symptomatic therapy of Alzheimer's disease (AD) and other disorders of memory. In the present study, the binding activity of RS 17017 (previously described as a selective 5-HT4 agonist) was assessed across a number of neurotransmitter receptors and binding sites, pharmacokinetic data were obtained, and the compound was evaluated in macaques for mnemonic effects via a computer-assisted delayed matching-to-sample task (DMTS). Binding data confirmed the 5-HT4 selectivity of the compound, while pharmacokinetic results revealed low oral bioavailability, but a large volume of distribution of the compound. Significant and reproducible improvements in DMTS accuracy were observed after oral administration of the compound across a dose-effect series in both younger and older monkeys. The results suggest that RS 17017 offers a potential for memory enhancement in disorders involving cognitive decline, and are consistent with a role for central 5-HT4 receptors in memory. Improvements in DMTS performance in aged monkeys may have particular implications for neurodegenerative conditions such as AD, whereas positive results in the younger monkeys indicate that RS 17017 (or similar compounds) may have additional potential in the therapeutics of memory disorders not necessarily associated with advanced age.

[3H]RS 57639, a high affinity, selective 5-HT4 receptor partial agonist, specifically labels guinea-pig striatal and rat cloned (5-HT4S and 5-HT4L) receptors

RS 57639, by being a partial agonist in rat esophagus but a competitive antagonist in guinea-pig ileum, is one of several ligands which operationally discriminate among 5-HT4 receptors in different tissues. The discovery of splice variants of the 5-HT4 receptor, 5-HT4S and 5-HT4L, raises the possibility that this functional heterogeneity among 5-HT4 receptors may be due to differences in the interaction of ligands with different isoforms of the receptor. To test this idea, the functional and binding interactions of RS 57639 with rat 5-HT4S and 5-HT4L receptors were characterized. RS 57639 stimulated adenylate cyclase in cells expressing 5-HT4S or 5-HT4L receptors with similar potency (pEC50 = 7.9 +/- 0.1 and 7.6 +/- 0.1) and efficacy (71 +/- 3 and 59 +/- 4% of 5-HT). [3H]RS 57639 also bound to 5-HT4S and 5-HT4L receptors with similar affinity (Kd = 0.09 +/- 0.01 and 0.11 +/- 0.01 nM) and specificity (SB204070 > GR113808 > SDZ 205557 > cisapride > renzapride > alpha me-5-HT > 5-CT). Therefore, the operational differences among 5-HT4 receptors, detected with RS 57639, are not explained by differences in the interaction of the ligand with 5-HT4S and 5-HT4L receptors. [3H]RS 57639 binding to guinea-pig striatal membranes was also characterized. [3H]RS 57639 bound with high affinity (Kd = 0.25 +/- 0.07 nM) and a specificity similar to that of the 5-HT4 receptor antagonist, [3H]GR113808. Therefore, while the mechanism by which RS 57639 operationally distinguishes among 5-HT4 receptors was not determined, [3H]RS 57639 was shown to specifically label native and cloned 5-HT4 receptors. As the first selective agonist radioligand to be described for this receptor, [3H]RS 57639 may prove useful in further studies of receptor coupling and ligand interactions.

The effects of novel, selective 5-hydroxytryptamine (5-HT)4 receptor ligands in rat spatial navigation

Activation of central 5-hydroxytryptamine (5-HT4) receptors may enhance cognitive performance. In the present study, the effects of two novel, potent and selective 5-HT4 receptor agonists, RS 67333 (1-(4-amino-5-chloro-2-methoxyphenyl)-3-(1-n-burtl-4-piperidinyl)- 1-propanone) and RS 67506 (1-(4-amino- 5-chloro-2-methoxyphenyl)-3-[1-[2-[(methylsulfonyl)amino]ethyl]-4- piperidinyl]-1-propanone), were studied in a rat model of spatial learning and memory; the Morris water maze. RS 67333 (0.1, 10 and 1000 micrograms/kg, intraperitoneally (i.p.)), a highly potent, selective and hydrophobic 5-HT4 receptor agonist, reversed the decrements in cognitive performance induced by atropine (30 mg/kg, i.p.). By contrast, no effect was seen to RS 67506 (0.1, 10 and 1000 micrograms/kg, i.p.), a hydrophilic 5-HT4 receptor agonist, of equivalent potency and selectivity to RS 67333. This differential effect may reflect the enhanced ability of RS 67333 to enter the CNS, with respect to RS 67506. The ameliorative actions of RS 67333 on cognitive dysfunction were abolished by prior treatment with a selective 5-HT4 receptor antagonist, RS 67532 [1-(4-amino-5-chloro-2-(3, 5-dimethoxy benzyloxyphenyl)-5-(1-piperidinyl)-1-pentanone; 1 mg/kg, i.p.]. When given alone, or in naive rats, RS 67532 (0.1, 10 and 1000 micrograms/kg, i.p.), was without effect. None of the compounds tested affected the swim speed at any of the doses used. In separate locomotor studies, RS 67532 reduced activity at 1 and 10 mg/kg, i.p., although no effect was seen with RS 67333 or RS 67506 (0.01-10 mg/kg, i.p.). These data suggest that RS 67333 reversed the cognitive deficit induced by atropine and support a role of 5-HT4 receptors in rat spatial learning and memory.

The 5-HT3 receptor antagonist, RS-56812, enhances delayed matching performance in monkeys

Substantial evidence indicates that serotonin receptors are involved in the regulation of acetylcholine release in CNS regions important to mnemonic processes, and may thus be exploited pharmacologically as targets for memory improvement. In the present study, the (R) and (S) isomers of a potent serotonin (5-HT3) receptor ligand, RS-56812 were evaluated for potential memory effects in five macaques trained to perform a delayed matching-to-sample (DMTS) task. While both isomers enhanced certain aspects of task performance, the (R) isomer produced more systematic improvements. This differential sensitivity to the isomers in regard to DMTS performance appears to parallel the higher 5-HT3 receptor affinity of the R enanantiomer. The results are consistent with a potential therapeutic role for RS-56812 in disorders involving cognitive decline.

Comparison of 5-HT4 receptors in guinea-pig colon and rat oesophagus: effects of novel agonists and antagonists

5-HT4 receptors in isolated distal colon myenteric plexus of guinea-pig, mediating contraction of longitudinal smooth muscle, have been further characterized by selective agonists and antagonists. The indole agonists, 5-HT and 5-methoxytryptamine (5-MeOT), were full agonists (relative to 5-HT) with potency values (pEC50) of 8.0 +/- 0.1 (n = 50) and 7.8 +/- 0.1 (n = 12), respectively. 5-HT4 receptor agonists of other structural classes, including benzimidazolones (BIMU 1 and BIMU 8), and benzamides ((S)-zacopride, (R)-zacopride, renzapride, SC 49518) were partial agonists with intrinsic activities less than that of 5-HT. In general, the potencies for these compounds at 5-HT4 receptors in guinea-pig colon were similar to the potencies seen in the rat isolated oesophagus, where 5-HT4 receptors mediate relaxation. GR 113808 ¿[1-[2-[(methylsulfonyl)amino]ethyl]-4-piperidinyl] methyl1-methyl-1H-indole-3-carboxylate¿, RS 39604 ¿1-[4-amino-5-chloro-2-(3, 5-dimethoxybenzyloxy)phenyl]-3[1-[2-[(methylsulfonyl)amino] ethyl]-4-piperidinyl]-1-propanone hydrochloride and SB 204070 ¿(1-n-butyl-4-piperidinyl)methyl 8-amino-7-chloro-1, 4-benzodioxane-5-carboxylate¿ antagonized 5-HT responses with pA2 values of 9.1 +/- 0.1, 9.0 +/- 0.2 and 11.0 +/- 0.1, respectively. These affinity values were similar to those obtained at 5-HT4 receptors in isolated rat oesophagus (9.0+/- 0.4, 9.3 +/- 0.1 and 10.6 +/- 0.1 respectively). Despite these operational similarities between 5-HT4 receptors in guinea-pig colon and rat oesophagus, several novel compounds have revealed important differences between 5-HT4 receptors in the two tissues. For example, the substituted benzoate, RS 23597 ¿3-(piperidine-1-yl) propyl-4-amino-5-chloro-2-methoxybenzoate hydrochloride, acted as a partial agonist (intrinsic activity 0.5) in guinea-pig colon with a potency of 7.6 +/-0.1 (n = 16). In isolated rat oesophagus, however, this compound was a surmountable antagonist (pA2 = 7.8 +/- 0.1) with no intrinsic activity. In contrast, the substituted naphthalimide (S)RS 56532 ¿(S)-6-amino-5-chloro-2-(1-azabicyclo[2, 2, 2]octan-3-yl) 2,3-dihydro-1H-benz[de] isoquinoline-1,3-dione hydrochloride¿, was a potent (pEC50 = 7.9 +/- 0.1), efficacious partial agonist (intrinsic activity = 0.8) in the rat oesophagus. However, in guinea-pig colon, it was a surmountable antagonist with an affinity (pKB) of 9.4 +/- 0.1. Furthermore, several novel, selective, 5-HT4 compounds also showed opposing patterns of intrinsic activities similar to those described for RS 23597 and (S)RS 56532. It is concluded that these differences are inconsistent with differences in 5-HT4 receptor reserves, and may suggest that 5-HT4 receptors in the guinea-pig colon and the rat oesophagus can be operationally distinguished.

Stereoselective effects of (R)- and (S)-zacopride on cognitive performance in a spatial navigation task in rats

In the present studies we investigated the actions of (R)- and (S)-zacopride, potent 5-HT3 receptor antagonists with 5-HT4 receptor agonists properties, on performance in a spatial learning and memory task in rats, the Morris water maze. A significant cognitive/performance deficit, as indicated by the increased escape latency across several trials, was produced by systemic administration of the muscarinic receptor antagonist atropine (30 mg/kg, IP). (R)-zacopride (0.001-1 microgram/kg, but not 10 or 100 micrograms/kg) significantly reduced escape latency in atropine-treated animals. (S)-Zacopride was inactive over the entire dose range examined (0.001-100 micrograms/kg, i.p.). Moreover, pretreatment with (S)-zacopride (1 or 100 micrograms/kg) did not alter the procognitive effects of (R)-zacopride (1 microgram/kg). These data demonstrate that the cognition enhancing properties of zacopride in this model of cholinergic hypofunction are exclusive to its (R)-enantiomer and imply that this action is unrelated to 5-HT, receptor antagonism or 5-HT4 receptor agonism. The possibility that the procognitive effects of (R)-zacopride may be related to actions at the novel "(R)-zacopride site" is discussed.

Characterization of [3H]GR 113808 binding to 5-HT4 receptors in brain tissues from patients with neurodegenerative disorders

[3H]GR 113808 binding studies in guinea-pig brain tissue revealed a temperature dependency and pharmacological specificity consistent with labelling of a 5-HT4 receptor. Detailed comparison of competition data between brain regions from human and guinea-pig suggest minor differences in the rank order of affinity. Studies in brain tissue from patients with Alzheimer's Huntington's and Parkinson's disease have revealed specific deficits in 5-HT4 receptor densities.

Central 5-HT4 receptors

Activation of the 5-HT4 receptor mediates widespread effects in central and peripheral nervous systems. Recent developments, such as the identification of novel, selective agonists and antagonists, as well the cloning of the receptor, have provided insights into the physiological role of the receptor. In this article, Richard Eglen and colleagues assess the emerging evidence relating to the function of the 5-HT4 receptor in the brain. The cerebral distribution of the receptor, along with neurochemical and electrophysiological data, suggests a role in cognition. The role of the receptor in modulation of dopamine transmission and anxiolysis is also addressed.

Herpes zoster meningoencephalitis without rash: varicella zoster virus DNA in CSF

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Ondansetron improves cognitive performance in the Morris water maze spatial navigation task

In the present studies we investigated the actions of ondansetron, a prototypic 5-hydroxytryptamine3 (5-HT3) receptor antagonist, on performance in a complex spatial navigation/memory task in rats. Specifically, we compared the activity of ondansetron to that of the cholinesterase inhibitor physostigmine in attenuating two distinct cognitive deficits in the Morris water maze. In the first model, rats treated with the muscarinic receptor antagonist atropine (30 mg/kg) had significantly longer latencies to find the submerged platform across two days of testing. Physostigmine (0.03, 0.1 and 0.3 mg/kg) and ondansetron (0.03-1 mg/kg) significantly reduced the latencies to find the submerged platform in atropine-treated animals, suggesting an increase in cognitive performance. There was little evidence of a dose-response relationship for either compound, and a loss of efficacy for ondansetron was seen at 3 mg/kg. In the second model, pre-screened, aged (23 months), cognition-impaired and nonimpaired rats were tested. Ondansetron (0.1 mg/kg), but not physostigmine (0.1 mg/kg), decreased the latencies to find the submerged platform in the aged-impaired rats, while neither compound improved performance of aged-nonimpaired rats. These data suggest that ondansetron may have cognition enhancing properties in animal models of aging and cholinergic hypofunction.

Enhancement of adenosine A1 receptor functions by benzoylthiophenes in guinea pig tissues in vitro

Previous reports on a series of benzoylthiophenes, including PD 81,723 [2-amino-4,5-dimethyl-3-(3-trifluoromethyl-benzoyl) thiophene], have shown specific enhancement of agonist binding at the adenosine A1 receptor. We have studied the effects of two substituted benzoylthiophenes, PD 78,416 (thieno[2,3-c]pyridine-6(5H)-carboxylic acid, 2-amino-3-benzoyl-4,7-dihydro-ethyl ester) and RS-74513-000 [2-amino-4-ethyl-5-methyl-3-(3-trifluoro-methyl-benzoyl) thiophene] on response elicited by adenosine A1 receptors in isolated guinea pig left atrium and ileum. In the electrically paced left atrium, PD 78,416 antagonized negative inotropic effect elicited by the agonist CPA [N6-cyclopentyladenosine] with a pKB value of 6.2 +/- 0.2 (n = 4). At a low concentration which had no antagonistic effect (0.1 microM), PD 78,416 enhanced the effect of CPA. The concentration-response curve to CPA was shifted leftward by 5.1 fold (95% confidence limits 2.4-11.2). In field stimulated isolated ileum, PD 78,416 (0.1, 0.3, 1 microM) did not enhance or antagonize effects of CPA. At concentrations above 1 microM, PD 78,416 decreased electrically induced contraction. This effect was not sensitive to adenosine deaminase and was not antagonized by the A1 antagonist CPX [8-cyclopentyl-1,3-dipropyl-xanthine] (1 microM). Unlike PD 78,416, RS-74513-000 (0.01, 0.1, 1, 3, 10 microM) did not antagonize or enhance effects of CPA in the left atrium. However, effects of CPA in ileum were enhanced by RS-74513-000 (1 and 3 microM).(ABSTRACT TRUNCATED AT 250 WORDS)

Allosteric interactions among agonists and antagonists at 5-hydroxytryptamine3 receptors

Cooperation in the action of agonists suggests that there are multiple binding sites on 5-hydroxytryptamine3 (5-HT3) receptors. The purpose of this study was to characterize these binding sites and their interactions on both native and cloned 5-HT3 receptors. The affinities of competitive 5-HT3 receptor antagonists were similar regardless of whether the receptors were labeled with [3H]RS-42358, [3H]granisetron, or 1-(m-[3H]chlorophenyl)biguanide ([3H]mCPG). By contrast, the affinities of the agonists 5-HT, mCPG, and phenylbiguanide were approximately 10-fold higher when the receptors were labeled with [3H]mCPG. The dissociation of [3H]mCPG, [3H]RS-42358, and [3H]RS-25259, but not [3H]granisetron, from both cloned and native 5-HT3 receptors was markedly slower in the presence of 5-HT or 2-methyl-5-HT than in the presence of antagonists such as RS-42358. This suggests that the binding of these agonists to unoccupied sites on the receptor can increase the receptor's affinity for prebound ligands and thereby slow their dissociation. These data support previous indications of positive cooperation among multiple binding sites on both native and cloned 5-HT3 receptors, and they extend this idea by demonstrating that agonists can modify the interaction of some, but not all, antagonists with the receptor.

Rat fibroblast cells overexpressing kinase-inactive human insulin receptors are insulin responsive: influence of growth conditions

The effects of insulin to stimulate metabolic and mitogenic responses were examined in Rat 1 fibroblast cells that overexpressed either normal (HIRc) or kinase-deficient human insulin receptors. When studied at the optimal growth stage for each cell line, insulin-stimulated responses measured in cells containing kinase-defective receptors with a Lys1018-Ala1018 substitution in the ATP-binding site of the kinase domain (A/K1018). Maximal insulin responsiveness for all these effects, measured as fold-increase over basal, was comparable in parental and HIRc cells (1.8- to 2.4-fold increases). Relative insulin responsiveness for all effects was greatest in A/K 1018 cells. One clone (AK-I) expressing a similar number of kinase-inactive receptors as in the HIRc cells displayed maximal responsiveness of 3.6- to 5.5-fold increases. A second A/K cell line containing 1/10 the number of kinase-inactive receptors displayed responsiveness intermediate between AK-I and parental or HIRc cells (1.5- to 4.8-fold increases). Both clones of kinase-deficient A/K1018 cells displayed impaired insulin sensitivity compared with HIRc cells. These findings suggest that expression of insulin receptor kinase activity is a determinant of insulin sensitivity but not necessarily of the final biological responsiveness of cells to insulin.

Characterization of the electrophysiological, biochemical and behavioral actions of epibatidine

Epibatidine has been reported to be a potent, nonopioid analgesic. In this study we further characterized its receptor interactions and its analgesic properties. Radioligand binding assays demonstrated that epibatidine has high affinity for nicotinic receptors (Ki = 0.12 nM) but low affinity for opioid and other receptors (Ki > 3.0 microM). In vitro functional assays demonstrated that the compound is a potent agonist at both neuronal and neuromuscular nicotinic receptors. Epibatidine depolarized rat isolated vagus nerve with an EC50 of 33.1 nM and contracted guinea pig ileum with an EC50 of 6.1 nM. Epibatidine contracted frog rectus abdominis muscle with an EC50 of 18.2 nM. In vivo, epibatidine demonstrated short-lived analgesic actions. Epibatidine (10 and 30 micrograms/kg), at 5 but not 20 min after dosing, increased the threshold for vocalization evoked by foot shock. Epibatidine, at 5 and 20 but not 60 min after dosing, also increased the latency to a nociceptive response in a hot-plate assay. Both (+)- and (-)-enantiomers of epibatidine were active in these assays. The action of epibatidine in the hot-plate test was reversed by the nicotinic receptor antagonist mecamylamine but not by the opioid receptor antagonist naloxone. In contrast to morphine, epibatidine failed to increase locomotor activity. These findings demonstrate that epibatidine is a potent agonist at both neuronal and neuromuscular nicotinic receptors. These findings also demonstrate a short-lived, naloxone-insensitive, analgesic action for both the (+)- and (-)-enantiomers of epibatidine.(ABSTRACT TRUNCATED AT 250 WORDS)

5-Hydroxytryptamine (5-HT)4 receptors in post mortem human brain tissue: distribution, pharmacology and effects of neurodegenerative diseases

1. The distribution, pharmacology and effects of neurodegenerative diseases on 5-HT4 receptors in human brain have been characterized in vitro. 2. The 5-HT4 receptor in post mortem human brain tissue was specifically labelled with [3H]-GR 113808. In human putamen, this ligand labelled a homogeneous population of sites, with an apparent affinity (-log Kd) of 10.1 and a density (Bmax) of 5.73 fmol mg-1 tissue. The pharmacology of this site was characterized by use of a series of displacing ligands, and the following rank order of apparent affinities (with mean +/- s.d. -log Ki values in parentheses) was generated: GR113808 (10.05 +/- 0.04) > SDZ 205,557 (8.65 +/- 0.08) > DAU 6285 (7.95 +/- 0.04) > BIMU-1 (7.81 +/- 0.06) > DAU 6215 (7.42 +/- 0.23) > tropisetron (7.39 +/- 0.23) > 5-HT (7.32 +/- 1.00) > BIMU-8 (7.25 +/- 0.04) > (R)-zacopride (5.82 +/- 0.04). The Hill coefficients were not significantly different from unity, consistent with an interaction at a single site. A comparison of the affinities of these compounds with those obtained from guinea-pig striatum indicated no evidence of species differences. 3. The regional distribution of 5-HT4 receptors was assessed by determining the density of binding sites for [3H]-GR 113808. The distribution were as follows (with mean +/- s.d. Bmax values, fmol mg-1 tissue, in parentheses): caudate nucleus (8.7 +/- 1.5), lateral pallidum (8.6 +/- 5.5), putamen (5.7 +/- 3.0), medial pallidum (3.8 +/- 0.9), temporal cortex (2.6 +/- 0.6), hippocampus (2.4 +/- 0.8), amygdala (2.3 +/-1.1), frontal cortex (1.7 +/- 0.5), cerebellar cortex (<1.0). In these studies, the affinities of GR 113808 were not significantly different.4. The density of 5-HT4 receptors selected from regions of post mortem brains of patients with Parkinson's disease, Huntington's disease and Alzheimer's disease were compared to age-matched controls. In Parkinson's disease, there was no significant difference between control or patient values(mean +/- s.d. Bmax values, fmol mg-1 tissue; putamen, control 4.74 +/- 0.07, patient 5.86 +/- 1.48; substantia nigra, control 4.21 +/- 2.56, patient 5.57 +/- 0.10). In Huntington's disease, there was a significant decrease in putamen (control 5.33 +/- 1.08, patient 2.68 +/- 1.08), while in Alzheimer's disease, there was a marked loss of receptors in hippocampus (control 2.34 +/- 0.62, patient 0.78 +/- 0.61), in frontal cortex (control,1.76 +/- 0.19, patient 1.30 +/- 0.22). Receptor density in temporal cortex showed a decrease, but did not achieve statistical significance (control 2.06 +/- 0.21, patient 1.44 +/- 0.64).5. These data suggest a heterogeneous distribution of 5-HT4 receptors in human brain, with high to moderate densities in basal ganglia and limbic structures. These receptors may not be principally co-localized on dopaminergic cell bodies or terminals, given the lack of change observed in Parkinson's disease. The loss of 5-HT4 receptors in the putamen in Huntington's disease raises the possibility of their presence on intrinsic striatal GABAergic or cholinergic neurones. The marked loss of receptors in hippocampal and cortical regions in the brains from patients with Alzheimer's disease is consistent with a role for the 5-HT4 receptor in cognitive processing.

The interaction of RS 25259-197, a potent and selective antagonist, with 5-HT3 receptors, in vitro

1. A series of isoquinolines have been identified as 5-HT3 receptor antagonists. One of these, RS 25259-197 [(3aS)-2-[(S)-1-azabicyclo[2.2.2]oct-3-yl]-2,3,3a,4,5,6-hexahydro- 1- oxo-1H-benzo[de]isoquinoline-hydrochloride], has two chiral centres. The remaining three enantiomers are denoted as RS 25259-198 (R,R), RS 25233-197 (S,R) and RS 25233-198 (R,S). 2. At 5-HT3 receptors mediating contraction of guinea-pig isolated ileum, RS 25259-197 antagonized contractile responses to 5-HT in an unsurmountable fashion and the apparent affinity (pKB), estimated at 10 nM, was 8.8 +/- 0.2. In this tissue, the -log KB values for the other three enantiomers were 6.7 +/- 0.3 (R,R), 6.7 +/- 0.1 (S,R) and 7.4 +/- 0.1 (R,S), respectively. The apparent affinities of RS 25259-197 and RS 25259-198, RS 25233-197 and RS 25233-198 at 5-HT3 receptors in membranes from NG-108-15 cells were evaluated by a [3H]-quipazine binding assay. The -log Ki values were 10.5 +/- 0.2, 8.4 +/- 0.1, 8.6 +/- 0.1 and 9.5 +/- 0.1, respectively, with Hill coefficients not significantly different from unity. Thus, at these 5-HT3 receptors, the rank order of apparent affinities was (S,S) > (R,S) > (S,R) = (R,R). 3. RS 25259-197 displaced the binding of the selective 5-HT3 receptor ligand, [3H]-RS 42358-197, in membranes from NG-108-15 cells, rat cerebral cortex, rabbit ileal myenteric plexus and guinea-pig ileal myenteric plexus, with affinity (pKi) values of 10.1 +/- 0.1, 10.2 +/- 0.1, 10.1 +/- 0.1 and 8.3 +/- 0.2, respectively. In contrast, it exhibited low affinity (pKi <6.0) at 28 other receptors in binding assays, including adrenoceptors (alpha1A, alpha 1B, alpha2A, alpha 2B ,beta1, beta2), muscarinic (M1-M4), dopamine (D1, D2), opioid and other 5-HT(5-HTlA, 5-HTlD, 5-HT2C, 5-HT4) receptors.4. RS 25259-197 was tritium labelled (specific activity: 70 Ci mmol-1) and evaluated in pharmacological studies. Saturation studies with [3H]-RS 25259-197 in membranes from NG-108-15 and cloned homomeric a subunits of the 5-HT3 receptor from N1E-1 15 cells expressed in human kidney 293E1 cells,revealed an equilibrium dissociation constant (Kd) of 0.05 +/- 0.02 and 0.07 +/- 0.01 nM, and Bmax of610 +/- 60 and 1068 +/- 88 fmol mg-1, respectively. Competition studies in NG-108-15 cells indicated a pharmacological specificity entirely consistent with labelling a 5-HT3 receptor, i.e. RS 25259-197> granisetron> (S)-zacopride> tropisetron> (R)-zacopride> ondansetron> MDL 72222.5. In contrast to the majority of radioligands available to label 5-HT3 receptors, [3H]-RS 25259-197 labelled a high affinity site in hippocampus from human post-mortem tissue with an equilibrium dissociation constant (Kd) of 0.15 +/- 0.07 nM and density (BmaX) of 6.8 +/- 2.4 fmol mg-1 protein. Competition studies in this tissue indicated a pharmacological specificity consistent with labelling of a 5-HT3receptor.6. Quantitative autoradiographic studies in rat brain indicated a differential distribution of 5-HT3receptor sites by [3H]-RS 25259-197. High densities of sites were seen in nuclear tractus solitaris and area postrema, a medium density in spinal trigeminal tract, ventral dentate gyrus and basal medial amygdala,and a low density of sites in hippocampal CAl, parietal cortex, medium raphe and cerebellum.7 In conclusion, the functional, binding and distribution studies undertaken with the radiolabelled and non-radiolabelled RS 25259-197 (S,S enantiomer) established the profile of a highly potent and selective5-HT3 receptor antagonist.

Cholinergic agents and delay-dependent performance in the rat

We tested cholinergic agents in delayed matching and nonmatching to position. Each task had a delay between the presentation of information and the chance to act on it later. We used a titrating procedure, new to experiments with rats, to determine the delay. Linopirdine (0.1 mg/kg), which releases acetylcholine, and physostigmine (0.1 mg/kg), a cholinesterase inhibitor, ameliorated the impairment of accuracy produced by scopolamine hydrobromide (0.1 mg/kg). In some cases, scopolamine hydrobromide decreased the number of trials, but physostigmine and linopirdine did not ameliorate that impairment. Both the muscarinic receptor antagonist, scopolamine hydrobromide (0.1 and 0.3 mg/kg), and its peripherally acting analog, scopolamine methylbromide (0.1 and 0.3 mg/kg), decreased accuracy. The impairment produced by scopolamine methylbromide suggests that the deficit produced by muscarinic receptor antagonism may have both a central and peripheral component. At the highest dose, scopolamine hydrobromide decreased the number of trials completed. Thus, some of the effects of scopolamine hydrobromide involve nonmnemonic performance factors. The performance deficits produced by scopolamine hydrobromide suggest that it may be necessary to qualify drug effects in terms of their action on both memorial and nonmemorial aspects of performance.

[3H]RS-23597-190, a potent 5-hydroxytryptamine4 antagonist labels sigma-1 but not sigma-2 binding sites in guinea pig brain

Recent findings have suggested a relationship between 5-hydroxytryptamine (5-HT)4 receptors and sigma binding sites. To test this idea, the affinity of 5-HT4 receptor ligands for sigma binding sites was examined. In contrast to the 5-HT4 receptor ligands BIMU-1 [endo-N-(8-methyl-8-azabicyclo[3.2.1]oct-3-yl)-2,3- dihydro-3-ethyl-2-oxo-1H-benzimidazole-1-carboxamide hydrochloride] and BIMU-8 [endo-N-(8-methyl-8-azabicyclo[3.2.1]oct-3- yl)-2,3-dihydro-(1-methyl)ethyl-2-oxo-1H-benzamidazole-1-carbox ami de hydrochloride], DAU 6215 ]N-(endo-8-methyl-8-azabicyclo[3.2.1.]oct-3-yl)-2,3-dihydro-2-oxo-1H- benzimidazole-1-carboxamide hydrochloride], 5-HT and 5-methoxytryptamine had low affinity for sigma binding sites (pKi < 6). Conversely, the sigma ligands haloperidol and pentazocine had low affinity for 5-HT4 receptors. Thus, no relationship was found between the affinity of ligands at 5-HT4 receptors and sigma binding sites. However, one potent 5-HT4 receptor antagonist, RS-23597-190 [3-(piperidine-1-yl)propyl-4-amino-5-chloro-2-methoxybenzoate hydrochloride], had high affinity for sigma-1 (pKi = 8.4) but not sigma-2 (pKi = 6.2) binding sites. [3H]RS-23597-190 bound to a saturable site with the pharmacology of a sigma-1 binding site: (pIC50) haloperidol (9.0) > (+)-pentazocine (8.8) > (+)-3-(hydroxyphenyl)-N-(1-propyl)piperidine (8.2) > 1,3-di-o-tolyl-guanidine (8.0) > (-)-pentazocine (7.8) = (+)-SKF 10,047 [N-allylnormetazocine] > (-)-SKF 10,047 (6.2) > BIMU-1 (5.3) > 5-HT and 5-methoxytryptamine. The distribution of [3H]RS-23597-190 binding sites was similar to that described for other sigma radioligands, with the greatest binding densities in cranial nerve nuclei, the tegmental nucleus and in the mamillary nucleus. In contrast to (+)-3-(hydroxyphenyl)-N-(1-propyl)piperidine, [3H]RS-23597-190 binding was not allosterically modulated by phenytoin. These studies do not support the notion of an obvious relationship between sigma and 5-HT4 receptors, but they provide additional insight into the structure/affinity relationship of ligands at specific sigma binding sites, and they uncover a novel sigma-1 receptor ligand whose binding is insensitive to the action of phenytoin.

Quantitative autoradiography of 5-HT4 receptors in brains of three species using two structurally distinct radioligands, [3H]GR113808 and [3H]BIMU-1

Recent radioligand binding studies have demonstrated the presence of 5-HT4 receptors throughout the nigrostriatal and mesolimbic systems of mammalian brain. In many regions, the binding has not yet been correlated with functional responses. The present study was carried out to fully characterize the regional distribution of 5-HT4 receptors in brain sections from three species using two structurally distinct radioligands, [3H]GR113808, and [3H]BIMU-1. The highest density of 5-HT4 receptors labeled with [3H]GR113808 was found in the olfactory tubercle, substantia nigra, ventral pallium and striatum of rat and guinea pig, and similar regions of pig-tail macaque monkey. A similar distribution of 5-HT4 receptors was observed in guinea pig brain using [3H]BIMU-1. With either ligand, the binding was saturable and of high affinity (Kd = 0.08-0.53 nM for [3H]GR113808; 1.4-3.0 nM for [3H]BIMU-1). These results extend previous distribution studies, confirm the heterogenous distribution of 5-HT4 receptors throughout the nigrostriatal and mesolimbic systems of three species, and demonstrate a similar distribution using two structurally distinct 5-HT4 radioligands.

Characterization of 5-hydroxytryptamine-induced depolarizations in rat isolated vagus nerve

An additional component of the depolarization induced by 5-hydroxytryptamine (5-HT) in the rat isolated vagus nerve has recently been attributed to activation of 5-HT4 receptors. To confirm and extend this finding, extracellular recordings of D.C. potentials were made using the 'grease-gap' technique during continuous superfusion of the isolated nerve. Beginning at 1 nM, 5-HT induced small depolarizations that displayed a slow onset. At concentrations > or = 1 microM, large depolarizations with rapid onset were elicited. In the presence of the 5-HT3 receptor antagonists, granisetron or ondansetron, 5-HT responses were diminished and exhibited an increased latency to peak. These small, slow depolarization were not reduced by 5-HT1 or 5-HT2 receptor antagonists, but were potently inhibited by the 5-HT4 receptor antagonist GR 113808 (pA2 = 9.3), and mimicked by 5-methoxytryptamine (pEC50 = 5.3). 5-HT4-mediated responses were larger at 37 degrees C than at 31 degrees C, but also showed marked diminution with repeated 5-HT applications at concentrations greater than 1 microM. Conversely, 5-HT3 receptor responses were potentiated at lower temperatures (< or = 31 degrees C). Consistent with the reported positive coupling of 5-HT4 receptors to adenylyl cyclase, forskolin and 8-Br-cAMP produced slowly developing depolarizations which were qualitatively similar to 5-HT4 receptor activation. Pre-depolarization of nerves with 10 microM forskolin or 300 microM 8-Br-cAMP diminished the effect of 5-HT4 receptors. This study has confirmed the presence of 5-HT4 receptors on the vagus nerve of the rat and defined some conditions that optimize their pharmacological isolation.(ABSTRACT TRUNCATED AT 250 WORDS)

Age-related differences in inter- and intrapersonal variables related to motivation in a group sport setting

Age-related differences in perceived competence, perceived control, and anxiety among 10- to 11-year-old boys and 12- to 13-year-old boys who participated in an American Youth Soccer Organization league were examined. Coaching behaviors thought to be related to these intrapersonal variables were also assessed, and the differences between the coaches in the two divisions were evaluated. There were no age-related differences in perceived competence. The children in the younger division endorsed both external perceptions of control and internal attributions for success more strongly than the older children did. The younger children in each division exhibited significantly more anxiety than their older teammates did, although there were no significant across-division effects. All the coaches exhibited more instructive behaviors than encouragement, and more individual-directed behaviors than team-direction behaviors, but the proportions of both instruction and individual-directed behaviors were relatively higher for the coaches in the older division than they were for the coaches in the younger division.

(R) and (S) RS 56532: mixed 5-HT3 and 5-HT4 receptor ligands with opposing enantiomeric selectivity

The pharmacological properties of the (R) and (S) enantiomers of RS 56532 have been studied in vitro and in vivo. In radioligand binding studies at 5-HT4 receptors in guinea-pig striatum, (S) RS 56532 exhibited a higher affinity than (R) RS 56532 (-log Ki = 7.6 and 6.5, respectively). (S) RS 56532 acted as a potent agonist at 5-HT4 receptors mediating relaxation of rat oesophageal muscularis mucosae (-log EC50 = 7.9) while (R) RS 56532 acted as a weaker agonist at this receptor (-log EC50 < 6.0). These data suggest that at 5-HT4 receptors, the enantiomeric selectivity of RS 56532 was (S) > (R). In binding studies at 5-HT3 receptors in rat cortex, (R) RS 56532, conversely, exhibited a higher affinity than (R) RS 56532 (-log Ki = 9.1 and 8.0, respectively). At 5-HT3 receptors in guinea-pig isolated ileum, (R) RS 56532 exhibited an affinity (-log KB) of 7.9, whereas (S) RS 56532 (1 nM-1 microM) was inactive. No agonism was observed at ileal 5-HT3 receptors with either enantiomers. These data suggest that at 5-HT3 receptors in rat and guinea-pig, both enantiomers acted as antagonists, with (R) > (S) RS 56532. At the non-5-HT3, high affinity '(R) zacopride' site, (R) RS 56532 exhibited a higher affinity than (S) RS 56532 (-log Ki = 6.1 and 4.9). This site was insensitive to potent 5-HT3 antagonists such as (R) YM 060 or ondansetron. However, it was recognized with relatively high affinity (-log Ki = 7.5) by the (R), but not (S) enantiomer, of RS 42358 (-log Ki = 4.7). Since (S) RS 42358 is a high affinity 5-HT3 receptor antagonist, these data further highlight the dissimilarity between the 5-HT3 receptor and the '(R) zacopride' site. The '(R) zacopride' site also appeared to be pharmacologically distinct from the 5-HT4 receptor, since 5-HT4 ligands such as renzapride, SDZ 205,557 or RS 23597-190 exhibited low affinities. The enantiomeric selectivity of (R) and (S) RS 56532 in vivo was consistent with findings in vitro. At 5-HT4 receptors mediating tachycardia in the pig, 5-HT induced a dose-dependent tachycardia (ED50 = 3 micrograms kg-1, i.v.; maximum response = 90-100 beats min-1). (S) RS 56532 increased heart rate by 88 min-1 with a potency of (ED50) of 3 micrograms kg-1, i.v.(ABSTRACT TRUNCATED AT 400 WORDS)