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Biomedical subjects

W Z Potter

Publications and source records attributed to W Z Potter.

At least 73 records · Page 4Linked to original sources
PubMed1993

Clinical investigation of monoamine neurotransmitter interactions.

Monoamine neurotransmitter systems are widely thought to be involved in the pathophysiology of affective disorders and schizophrenia and the mechanism of action of antidepressant and antipsychotic drugs. Previous clinical studies have focused on individual monoamine function in isolation, even though a large number of preclinical studies have demonstrated that monoamine neurotransmitter systems interact with one another. In the present paper, preclinical data on monoamine neurotransmitter interactions are reviewed, and two methods for examining monoamine neurotransmitter system interactions in clinical data are presented. One of the best replicated findings in biological psychiatry is that monoamine metabolites in CSF correlate with one another. The degree of correlation may be in part a measure of the degree of interaction between the parent monoamine neurotransmitter systems. Another approach to studying interactions is the use of HVA/5HIAA and HVA/MHPG ratios as an index of interactions between 5HT-DA and NE-DA. When these methods are applied in schizophrenia, patients are found to have decreased monoamine metabolite correlations compared to normal controls. Metabolite correlations increase significantly after antipsychotic treatment, and the HVA/5HIAA and HVA/MPHG ratios also increase, suggesting that neuroleptics may act in part by strengthening interactions between monoamines. BPRS ratings are negatively correlated with HVA/5HIAA and HVA/MHPG so that patients with higher ratios have fewer symptoms, particularly after treatment. These results provide direct experimental support for hypotheses suggesting that interactions between monoamine neurotransmitters are important in schizophrenia. Some of the effects of the atypical neuroleptic, clozapine, on metabolite correlations and ratios are also discussed.

Animals↗
PubMed1993

Idazoxan, an alpha 2 antagonist, augments fluphenazine in schizophrenic patients: a pilot study.

Idazoxan, a selective alpha 2-adrenergic antagonist, was added to stable doses of fluphenazine treatment in six patients with schizophrenia who participated in a double-blind, placebo-controlled pharmacologic study. Compared with fluphenazine alone, combining idazoxan (mean dose, 120 mg/day) with fluphenazine (mean dose, 28 mg/day) resulted in a significant decrease in Brief Psychiatric Rating Scale total symptoms (p < 0.05). Symptom ratings returned to baseline upon idazoxan discontinuation. No significant effects of idazoxan were observed on fluphenazine levels in plasma or on extrapyramidal symptoms. These pilot data are compatible with the notion that increased noradrenergic neurotransmission may enhance the therapeutic effects of typical neuroleptics in schizophrenia.

Adrenergic alpha-Antagonists↗
PubMed1993

Psychotherapeutic Medications Development Program (PMDP).

The Psychotherapeutic Medications Development Program (PMDP) of the National Institute of Mental Health was established in 1990. The purpose of the PMDP is to improve, enhance, and speed the development of new medications and improve the therapeutic usefulness of existing medications for the treatment of mental illness. The PMDP will fulfill this mission by implementing four initiatives. In the drug discovery and development initiative, the PMDP will aid in the development of promising new drugs. This initiative will also include improving the therapeutic usefulness of existing medications. In the technology transfer initiative, PMDP will improve the technology transfer from academic and government researchers to the pharmaceutical industry; improve the dissemination of information concerning technology transfer opportunities as it pertains to psychotherapeutic medications; and enhance technology transfer by acting as a broker to bring interested parties together. For the third initiative, the PMDP will develop and maintain a capability to clinically evaluate psychotherapeutic medications. The PMDP will also act to facilitate the development and testing of new concepts and models of mental illness. There is a detailed description of the steps that are involved in developing a new chemical entity (NCE) from the conceptual stage to a medication that is approved for the treatment of a particular illness. The pharmaceutical industry estimates that this medication development process costs $238 million.

Humans↗
PubMed1993

Pharmacological issues in the treatment of bipolar disorder: focus on mood-stabilizing compounds.

The acute and chronic pharmacotherapy of bipolar disorder requires an understanding of the pharmacology of very dissimilar compounds--the mood stabilizers (lithium, carbamazepine and valproate) and several classes of antidepressants. No definitive data are available on the primary mode of action of mood stabilizers, and those used show no single pharmacological property. On the other hand, the pharmacokinetics and dynamics of these compounds are well studied.

Anticonvulsants↗
PubMed1992

Idazoxan down-regulates beta-adrenoceptors on C6 glioma cells in vitro.

Incubation of the C6 cells with 10 microM idazoxan (an alpha 2-adrenoceptor antagonist and putative antidepressant) for 5 days in vitro resulted in a 23% reduction of beta-adrenoceptor number and a 37% decrease in isoproterenol-induced cyclic AMP accumulation. In contrast, post-receptor stimulated cyclic AMP accumulation (by the use of forskolin or cholera toxin) was unaffected. The desensitization of the beta-adrenoceptor was accompanied by an increase in the KL/KH ratio for this receptor. Chronic in vitro treatment of C6 glioma cells with idazoxan did not significantly affect cholera or pertussis toxin catalyzed ribosylation of Gs and Gi/Go in these cells. Similarly, idazoxan did not alter either the basal levels of protein kinase C (PKC) alpha, or its cytoplasm to membrane translocation. These results suggest that idazoxan may have direct postsynaptic effects, the site of which may be at the level of receptor/G protein interaction.

Adrenergic alpha-Antagonists↗
PubMed1992

Cerebrospinal fluid neurochemistry in children and adolescents with obsessive-compulsive disorder.

Cerebrospinal fluid hormones, monoaminergic metabolites, and dynorphin A (1-8 sequence) were examined in 43 children with severe, primary obsessive-compulsive disorder. Cerebrospinal fluid levels of 5-hydroxyindoleacetic acid were positively correlated with one of eight obsessive-compulsive disorder severity ratings and three of seven measures of improvement following 5 weeks of treatment with clomipramine hydrochloride. Arginine vasopressin concentration was significantly and negatively correlated with several ratings of obsessive-compulsive disorder symptom severity, while oxytocin concentration was positively correlated with depressive symptoms. The ratio of arginine vasopressin to oxytocin was also negatively correlated with obsessive-compulsive disorder and depressive symptoms. Comorbid affective disorder was associated with decreased arginine vasopressin concentrations, while concomitant anxiety disorder was associated with increased oxytocin. Dynorphin A (1-8 sequence), homovanillic acid, corticotropin, 3-methoxy-4-hydroxyphenylglycol, and corticotropin releasing hormone were not significantly related to obsessive-compulsive disorder symptoms. These results seem to indicate that arginine vasopressin may be related to obsessive-compulsive disorder symptom severity, while 5-hydroxyindoleacetic acid might be associated with drug response.

Adolescent↗
PubMed1992

Lithium administration modulates platelet Gi in humans.

Platelet G proteins were assessed in 7 normal volunteers before and after 14 days of lithium administration at therapeutic plasma levels. Cholera and pertussis toxin catalyzed ADP-ribosylation of platelet membrane proteins were measured by SDS-PAGE. Immunoblotting with specific antibodies was used to measure platelet membrane alpha i content. There was a statistically significant 37% increase in pertussis toxin mediated ADP-ribosylation of a 40,000 Mr protein in platelet membranes after lithium administration, but cholera toxin mediated ADP-ribosylation of a 45,000 Mr protein and alpha i immunoblotting were unchanged by lithium. Increased pertussis toxin stimulated ADP-ribosylation in the absence of changes in alpha i content could be explained by a shift in platelet Gi in favor of its undissociated, inactive form. This would be consistent with increased platelet adenylyl cyclase activity found in these same subjects after lithium.

Adenosine Diphosphate Ribose↗
PubMed1992

In vivo evidence that lithium inactivates Gi modulation of adenylate cyclase in brain.

In vivo microdialysis of cyclic AMP from prefrontal cortex complemented by ex vivo measures was used to investigate the possibility that lithium produces functional changes in G proteins that could account for its effects on adenylate cyclase activity. Four weeks of lithium administration (serum lithium concentration of 0.85 +/- 0.05 mM; n = 11) significantly increased the basal cyclic AMP content in dialysate from prefrontal cortex of anesthetized rats. Forskolin infused through the probe increased dialysate cyclic AMP, but the magnitude of this increase was unaffected by chronic lithium administration. Inactivation of the inhibitory guanine nucleotide binding protein Gi with pertussis toxin increased dialysate cyclic AMP in control rats, as did stimulation with cholera toxin (which activates the stimulatory guanine nucleotide binding protein Gs). The effect of pertussis toxin was abolished following chronic lithium, whereas the increase in cyclic AMP after cholera toxin was enhanced. In vitro pertussis toxin-catalyzed ADP ribosylation of alpha i (and alpha o) was increased by 20% in prefrontal cortex from lithium-treated rats, but the alpha i and alpha s contents (as determined by immunoblot) as well as the cholera toxin-catalyzed ADP ribosylation of alpha s were unchanged. Taken together, these results suggest that chronic lithium administration may interfere with the dissociation of Gi into its active components and thereby remove a tonic inhibitory influence on adenylate cyclase, with resultant enhanced basal and cholera toxin-stimulated adenylate cyclase activity.

Adenylate Cyclase Toxin↗
PubMed1991

Chronic exposure of C6 glioma cells to desipramine desensitizes beta-adrenoceptors, but increases KL/KH ratio.

Incubation of rat glioma C6 cells with 10 microM desipramine for five days in vitro resulted in a 31% reduction of beta-adrenoceptors and a 38% reduction in isoproterenol-stimulated cyclic AMP accumulation. In contrast, forskolin or cholera toxin-stimulated cyclic AMP was unaffected by desipramine. Surprisingly, the beta-adrenoceptor desensitization was accompanied by an increase in the ratio of dissociation constants (KL/KH) for the low and high affinity states of the beta-adrenoceptor respectively and supports the concept of a complex interaction between the receptor and Gs protein.

Animals↗
PubMed1991

Hypothalamic--pituitary--adrenal axis and monoamine transmitter activity in depression: a pilot study of central and peripheral effects of electroconvulsive therapy.

Central and peripheral measures of hypothalamic--pituitary--adrenal (HPA) axis and monoamine neurotransmitter activity were assessed in 8 depressed patients during a medication-free period and again after completion of a course of electroconvulsive therapy (ECT). Seven patients responded fully to ECT. At baseline there was corresponding activation of the HPA and noradrenergic systems, with apparent elevation in cerebrospinal fluid (CSF) concentrations of corticotropin-releasing hormone (CRH) in some patients. Neither CRH nor adrenocorticotropin (ACTH) in CSF changed significantly after ECT, with a mean 10% decline in CSF CRH. Urinary free cortisol (UFC) excretion was high both before and after treatment. Although peripheral noradrenergic hyperreactivity at baseline appeared to normalize with ECT, CSF concentrations of the principal norepinephrine metabolite, 3-methoxy-4-hydroxyphenyl-glycol (MHPG) were unaffected and remained correlated with CSF CRH. In contrast, there were increases in the CSF levels of the main metabolite of serotonin in half the patients.

Adult↗