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Biomedical subjects

W Z Potter

Publications and source records attributed to W Z Potter.

At least 127 records · Page 7Linked to original sources
PubMed1989

Lack of seasonal variation in pediatric lumbar cerebrospinal fluid neurotransmitter metabolite concentrations.

Seasonal variation of cerebrospinal fluid (CSF) monoamines, particularly 5-hydroxyindoleacetic acid (5-HIAA) and homovanillic acid (HVA) has been reported for psychiatrically ill and normal adults. Circannual variability was examined for a group of 72 children (mean age = 159.4 +/- 40.3 (SD), range 77-238 months), with a primary diagnosis of obsessive-compulsive disorder (OCD) or disruptive behavior disorder (DBD) (attention deficit disorder, oppositional disorder and/or conduct disorder), from whom CSF had been obtained systematically. There were no seasonal differences in mean concentrations of 3-methoxy-4-hydroxyphenylglycol (MHPG), HVA, or 5-HIAA, either for the group as a whole, for the separate diagnostic (OCD vs DBD) categories or for the pre-pubertal subgroup. Log-corrected HVA concentrations for the Tanner IV and V subgroup differed by season with summer concentrations less than those of fall (P = 0.06) and winter (P = 0.005). The results suggest that pubertal changes may play a role in any expression of circannual variability.

Adolescent↗
PubMed1989

The effects of intravenous clomipramine on neurohormones in normal subjects.

The neuroendocrine effects of iv administration of clomipramine (CMI), a serotonin reuptake inhibitor, were studied in normal subjects. Under double blind, placebo-controlled conditions, single 10- and 20-mg doses of CMI were administered. Ten milligrams of CMI led to significant increases in plasma PRL and cortisol concentrations; plasma ACTH increased slightly but not significantly. In contrast, plasma GH, melatonin, and norepinephrine concentrations did not increase. Plasma PRL, ACTH, and cortisol levels increased significantly after 20 mg CMI; again, there were no significant changes in plasma GH, melatonin, or norepinephrine concentrations. All subjects tolerated the 10-mg dose well, but the 20-mg dose caused nausea in three of six subjects. Desmethylclomipramine, a metabolite that inhibits reuptake of norepinephrine, was not detectable in plasma after either CMI dose. These results support the hypothesis that serotonin is involved in the regulation of PRL, cortisol, and ACTH in humans.

Adrenocorticotropic Hormone↗
PubMed1989

Antidepressants. A comparative review of the clinical pharmacology and therapeutic use of the 'newer' versus the 'older' drugs.

Supplementing but not supplanting the original series of tricyclic and monoamine oxidase (MAO) inhibitor compounds, a new generation of antidepressant medications has been developed and marketed throughout the past decade. Constituting a more diverse group of drugs than the standard agents, the newer drugs in general have more selective acute biochemical actions (reuptake blockade of a single neurotransmitter, inhibition of 1 subtype of MAO), enabling more precise targeting of symptoms and avoiding common antidepressant-associated side effects, especially anticholinergic and cardiovascular effects. Moreover, a number of recent additions to this group, such as bupropion and ademetionine (S-adenosyl-methionine), incorporate novel mechanisms of action, challenging previous concepts of how antidepressants work, and offering opportunities for research into the pathophysiology of mood disorders. Caution in prescribing the newer antidepressants must be applied, however, as recent experience, e.g. with nomifensine, suggests that unforeseen toxicities may not appear until a medication has been in use for several years.

Animals↗
PubMed1988

Quantitative autoradiography of beta-adrenoceptors in the cardiac vagus ganglia of the rat.

We studied beta-adrenoceptors by quantitative autoradiography in the cardiac vagus ganglia of the rat, after incubation of tissue sections with [125I]iodocyanopindolol. The cardiac vagus ganglia presented a high concentration of a single population of high affinity binding sites (Bmax 109 +/- 10 fmol/mg protein; Kd 64 +/- 5 pM). Displacement studies with the beta 1-selective adrenoceptor antagonist CGP 20712 A and the beta 2-selective adrenoceptor antagonist ICI 118,551 indicated that most (80 to 90%) of the binding sites are of the beta 2-type.

Animals↗
PubMed1988

Axonal transport of angiotensin-converting enzyme in the rat striatonigral pathway.

We analyzed the transport of angiotensin-converting enzyme (kininase II, EC 3.4.15.1) in the striatonigral pathway by quantitative autoradiography using the specific converting enzyme inhibitor, 125I-351A. 125I-351A binding was studied at different time intervals after knife cut lesions of the striatonigral pathway. Twenty-four h after the lesion, accumulations of 125I-351A binding sites were observed both rostral and caudal to the lesioned site. No change in 125I-351A binding was observed at this time in the caudate putamen and substantia nigra. Ten days after the lesion, a significant decrease (58%) in 125I-351A binding was found in the pars reticulata of the ipsilateral substantia nigra. These results suggest that the angiotensin-converting enzyme is transported axonally in the rat striatonigral pathway.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1988

Bupropion in depression. I. Biochemical effects and clinical response.

We studied the biochemical effects of bupropion hydrochloride, a unicyclic antidepressant, in 11 depressed patients. Plasma homovanillic acid level increased significantly in patients who had poor responses to treatment but not in patients who obtained good clinical responses. Although bupropion is characterized preclinically as a weak dopamine reuptake inhibitor without appreciable effects on norepinephrine (NE) reuptake, it reduced whole-body NE turnover without altering plasma NE levels at rest and following orthostatic challenge. There was a trend toward a reduction in cerebrospinal fluid 3-methoxy-4-hydroxyphenylglycol and homovanillic acid concentrations following bupropion treatment, although these changes did not achieve statistical significance. Reduction in whole-body NE turnover has now been described for six disparate antidepressant treatments. Poor clinical outcome following treatment with bupropion may be related to perturbations in dopaminergic systems.

Adult↗
PubMed1988

Bupropion in depression. II. The role of metabolites in clinical outcome.

We studied the steady-state pharmacokinetics of bupropion hydrochloride, a unicyclic aminoketone antidepressant, in depressed patients. The metabolites hydroxybupropion (HB), threohydrobupropion, and erythrohydrobupropion predominated over the parent compound in plasma and cerebrospinal fluid at steady state. Plasma concentrations of each metabolite correlated with cerebrospinal fluid concentrations. Higher plasma metabolite concentrations were associated with poor clinical outcome. This relationship was most striking with HB; plasma HB levels were greater than 1250 ng/mL in all five nonresponders and less than 1200 ng/mL in all seven responders. Plasma HB levels correlated with postreatment plasma homovanillic acid levels. High levels of bupropion metabolites may be associated with poor clinical outcome due to toxic effects involving dopaminergic systems. Alternatively, a curvilinear dose-response relationship may exist for bupropion metabolites. Future studies should explore the clinical utility of plasma metabolite measurements in enhancing the efficacy of treatment with bupropion.

Adult↗
PubMed1988

Antidepressants reduce whole-body norepinephrine turnover while enhancing 6-hydroxymelatonin output.

The effects of antidepressant treatment on noradrenergic function were studied in 27 patients with a major affective disorder. Twenty-four-hour urinary excretion of 6-hydroxymelatonin and "whole-body norepinephrine (NE) turnover," ie, 24-hour urinary output of NE and its major metabolites 3-methoxy-4-hydroxyphenylglycol, vanillylmandelic acid, and normetanephrine, were measured before and after treatment with the tricyclic desipramine hydrochloride, the aminoketone bupropion hydrochloride, the nonselective monoamine oxidase (MAO) inhibitor tranylcypromine sulfate, and the specific MAO type A inhibitor clorgiline. 6-Hydroxymelatonin excretion increased following antidepressant treatment, while at the same time whole-body NE turnover was reduced. These findings support the hypothesis that antidepressant therapy increases noradrenergic "efficiency," in that functional output, as measured by 6-hydroxymelatonin, is maintained while total NE production is decreased.

Adult↗
PubMed1988

Lymphocyte beta-adrenergic receptor modification in bulimia.

beta-Adrenergic receptor binding on circulating lymphocytes was evaluated in young female bulimic patients (n = 12) and age- and sex-matched normal control volunteers (n = 10). Using iodine 125-labeled cyanopindolol, antagonist binding was evaluated (number of receptors [Bmax] and dissociation constant [KD]), and using isoproterenol competition of cyanopindolol binding, the concentration required to inhibit binding by 50% (IC50) for isoproterenol and the agonist affinity measure of KL/KH (ratio of dissociation constants for the low- and high-affinity states of the receptor) were determined. Plasma norepinephrine (NE) level was also measured. There was a trend toward lower plasma NE levels in the bulimic patients. The KL/KH ratio in bulimic patients was significantly greater than that for the normal volunteers, indicating increased receptor coupling. The KL/KH ratio was not significantly correlated with plasma NE level. Neither Bmax nor KD was different between the two groups. These findings suggest that beta-adrenergic receptors in bulimic patients may be more responsive than in normal subjects, without alteration of the traditional measures of receptor responses, a difference that cannot be explained on the basis of plasma NE. These findings provide another line of evidence for altered regulation of the noradrenergic system in bulimic patients during a controlled phase of their illness.

Adult↗
PubMed1988

High correlations of norepinephrine, dopamine, and epinephrine and their major metabolite excretion rates.

We have previously reported high correlations between norepinephrine and its metabolite outputs in depressed patients. In this article, we expand this finding to healthy volunteers and alcoholic patients. Furthermore, we find similar high correlations between urinary outputs of dopamine, norepinephrine, and their major metabolites. The same is true, to a lesser degree, for epinephrine and metanephrine outputs. There are implications of these findings for psychobiological research on the monoamine systems.

Adult↗
PubMed1988

Concentration gradient of CSF monoamine metabolites in children and adolescents.

Whether the lumbar cerebrospinal fluid (CSF) concentration gradient of monoamine metabolites found in adults is influenced by age or pubertal status was studied in 26 children ranging from 6.5 to 17.3 years of age. Homovanillic acid (HVA), 5-hydroxyindoleacetic acid (5-HIAA), and 3-methoxy-4-hydroxyphenylglycol (MHPG) were assayed by high-power liquid chromatography (HPLC) with electrochemical detection. Eight patients were prepubertal (Tanner stage I). The slopes in units of picomoles/milliliter/milliliter for regression lines for CSF monoamine metabolite concentrations versus milliliter of CSF collected were 5.07 +/- 0.65, 10.13 +/- 2.0, and 0.67 +/- 0.22 for 5-HIAA, HVA, and MHPG, respectively, for the group as a whole. Significant correlations with age, height, weight, or Tanner stage were not found for the HVA or MHPG concentration gradients. Tanner stage and 5-HIAA slope were significantly correlated. Three of eight prepubertal patients had nonsignificant 5-HIAA gradients. CSF studies in pediatric populations must control for aliquot collected, as the size of the gradient could produce differences sufficient to mimic a "positive" clinical study if the aliquots collected are not the same.

Adolescent↗
PubMed1988

Dissociation of norepinephrine turnover from alpha-2 responses after clorgiline.

Responses to intravenous clonidine, a possible central noradrenergic probe, were examined in patients with depression before and after treatment with clorgiline, a selective monoamine oxidase type A inhibitor. Pulse rate, mean arterial blood pressure, plasma norepinephrine, 3-methoxy-4-hydroxyphenylglycol, and growth hormone were measured. Clorgiline treatment (2.5 to 10 mg/day) produced a variable reduction in the hypotensive response to clonidine but did not influence heart rate or plasma norepinephrine responses. Clorgiline markedly reduced the urinary output of norepinephrine and metabolites, indicating a reduced turnover of norepinephrine. None of the measured parameters corresponded with clinical effect. These data suggest that any clorgiline-induced alterations in alpha 2-receptor function as measured by responses to clonidine are modest and highly variable. Furthermore, since the variable and inconsistent changes in alpha 2-receptor function are dissociated from the massive changes in norepinephrine metabolism, regulation of presynaptic alpha 2-receptors appears unlikely to mediate the effects of clorgiline in patients with depression.

Bipolar Disorder↗
PubMed1988

Characterization of beta 1- and beta 2-adrenoceptor subtypes in the rat atrioventricular node by quantitative autoradiography.

We characterized beta-adrenoceptor subtypes in the atrioventricular node of the rat heart by quantitative autoradiography. Consecutive 16-microns-thick sections from single rat hearts containing the atrioventricular node were incubated with increasing concentrations of [125I]iodocyanopindolol. After exposure to [3H]Ultrofilm, optical densities corresponding to the atrioventricular node were determined by computerized densitometry after comparison with [125I]standards. The computer program LIGAND was used for analysis of receptor subtypes. Delineation of beta-adrenoceptor subtypes was achieved by incubating consecutive tissue sections with 50 pM [125I]iodocyanopindolol in the presence of increasing concentrations of the beta 1-selective antagonist atenolol or the beta 2-selective antagonist ICI 118,551. The atrioventricular node contains a higher concentration of beta-adrenoceptors than the adjacent interventricular septum. We estimated that the proportions of beta 1- and beta 2-adrenoceptors in the atrioventricular node were about 56% and 44% of the total binding capacity respectively.

Animals↗
PubMed1987

Axonal transport of dopamine D1 receptors in the rat brain.

Binding of a specific dopamine D1 receptor antagonist, 125I-SCH 23982, was measured in rat brain sections by quantitative autoradiography at various time intervals, following a knife cut through the striatonigral pathway. Twenty-four hours after lesioning, accumulations of D1 receptor binding sites were found in sagittal sections both rostral and caudal to the lesion site. No other regions studied (caudate-putamen, nucleus accumbens, olfactory tubercle, and substantia nigra pars reticulata) showed any change in D1 receptor binding 24 h after the lesion. In brain sections obtained 10 days after lesioning, only the substantia nigra pars reticulata had a significant decrease in D1 receptors ipsilateral to the lesion. These findings suggest the possibility of a presence of bidirectional axonal transport of D1 receptors in rat striatonigral pathway.

Animals↗