Biomedical subjects
D L Murphy
Publications and source records attributed to D L Murphy.
Serotonin (5-HT) receptor, 5-HT transporter and G protein-effector expression: implications for depression.
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Functional subsensitivity of 5-hydroxytryptamine1C or alpha 2 adrenergic heteroreceptors mediating clonidine-induced growth hormone release in the Fawn-Hooded rat strain relative to the Wistar rat strain.
Administration of various doses of clonidine increased plasma growth hormone levels. Pretreatment with the alpha 2 adrenergic antagonists, yohimbine and 1-(2-pyrimidyl)piperazine, completely blocked clonidine's effect on growth hormone levels. Pretreatment with the 5-hydroxytryptamine3 (5-HT3) receptor antagonist, MDL-72222, the 5-HT1A/5-HT2 antagonist, spiperone, and the mixed beta adrenergic/5-HT1B antagonists, l-propranolol and CGP361A, did not attenuate clonidine-induced increases in growth hormone levels. In contrast, pretreatment with the non-selective 5-HT1/2 antagonist, metergoline, and the 5-HT1C/5-HT2-selective antagonist, mesulergine, reduced clonidine-induced increases in growth hormone levels 81 to 87% without affecting clonidine-induced decreases in locomotor activity. Two other 5-HT1C/5-HT2 antagonists, ritanserin and mianserin, also attenuated (47%) clonidine-induced increases in growth hormone levels. Pretreatment with the noradrenergic neurotoxin, DSP4, did not block clonidine's effect on growth hormone levels. Clonidine administration decreased locomotor activity in both the Fawn-Hooded and the Wistar rat strains to the same extent. On the other hand, clonidine administration failed to increase growth hormone levels in the Fawn-Hooded rat strain. These findings suggest that clonidine stimulates growth hormone secretion by activation of alpha 2 adrenergic heteroreceptors present on 5-HT nerve terminals which, in turn, enhance 5-HT activity via stimulation of postsynaptic 5-HT1C receptors to promote growth hormone releasing factor. Furthermore, either 5-HT1C receptors or alpha 2 adrenergic heteroreceptors or both are functionally sub-sensitive in the Fawn-Hooded rat strain relative to the Wistar rat strain.
Effects of various serotonin receptor subtype-selective antagonists alone and on m-chlorophenylpiperazine-induced neuroendocrine changes in rats.
Administration of m-chlorophenylpiperazine [m-CPP, a serotonin (5-HT) agonist] to rats increases plasma concentrations of prolactin and corticosterone. Pretreatment with various doses of ritanserin (5-HT1C/5-HT2 antagonist), ICS 205-930 and MDL-72222 (5-HT3 antagonists), iodocyanopindolol or CG361A (beta adrenoceptor antagonists) and spiperone (5-HT1A/5-HT2 antagonist) did not attenuate m-CPP-induced increases in plasma concentrations of prolactin. In contrast, pretreatment with various doses of metergoline (5-HT1/5-HT2 antagonist), propranolol (beta adrenoceptor antagonist that also has binding affinity for 5-HT1A, 5-HT1B and 5-HT1C sites), mesulergine and mianserin (5-HT1C/5-HT2 antagonists) attenuated m-CPP-induced increases in plasma prolactin. On the other hand, m-CPP-induced increases in corticosterone concentrations were attenuated only by pretreatment with a low dose of mianserin and a high dose of spiperone. When administered without m-CPP, metergoline, mesulergine, ritanserin, ICS 205-930 and high doses of mianserin, spiperone and propranolol increased plasma corticosterone secretion. On the other hand, none of the antagonists used in the present study, except spiperone, had any significant effect on plasma prolactin secretion. These findings suggest that m-CPP-induced prolactin secretion is mediated by stimulation of 5-HT1C receptors while corticosterone secretion may be mediated either by an antagonistic effect at 5-HT3 receptor subtype or by nonserotonergic mechanisms. Alternatively, enhancement of corticosterone secretion by the 5-HT antagonists when administered alone may be responsible for their failure to block m-CPP-induced corticosterone secretion.(ABSTRACT TRUNCATED AT 250 WORDS)
A preliminary investigation of the lifetime prevalence of anorexia and bulimia nervosa in patients with obsessive compulsive disorder.
BACKGROUND: Obsessive compulsive disorder (OCD) is currently classified as an anxiety disorder although it possesses many characteristics that distinguish it from other anxiety disorders. Clinically and neurobiologically, OCD appears to overlap somewhat with the eating disorders. METHOD: To assess in a controlled fashion the lifetime prevalence of the eating disorders in patients with OCD, we administered portions of the Structured Clinical Interview for DSM-III-R, Patient Version (SCID-P), to 62 patients (31 men, 31 women) with a primary DSM-III-R diagnosis of OCD. RESULTS: Among the OCD patients, the lifetime prevalence of anorexia nervosa and/or bulimia nervosa was 12.9% (N = 8), and an additional 17.7% (N = 11) met subthreshold criteria for either anorexia or bulimia nervosa. Interestingly, unlike multiple epidemiologic studies that have reported a substantial female preponderance among patients diagnosed with anorexia or bulimia nervosa, there was no significant gender difference in the lifetime prevalence of eating disorders among the patients with OCD. Almost 13% (N = 4) of the men and 6.5% (N = 2) of the women with OCD met criteria for a lifetime diagnosis of anorexia nervosa and 3.2% (N = 1) of the men and 6.5% (N = 2) of the women with OCD met criteria at some time in their lives for bulimia nervosa. In addition, subthreshold criteria for anorexia nervosa or bulimia nervosa were met by an additional 12.9% (N = 4) of the men and 22.6% (N = 7) of the women. CONCLUSION: These data suggest that OCD patients, regardless of gender, have a substantial lifetime prevalence of anorexia and/or bulimia nervosa.
Seizure associated with fluoxetine and adjuvant buspirone therapy.
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A double-blind, placebo controlled study of trazodone in patients with obsessive-compulsive disorder.
Patients with obsessive-compulsive disorder (OCD) have been shown to be preferentially responsive to serotonin (5-HT) uptake-inhibiting antidepressants including clomipramine, fluoxetine, fluvoxamine, and sertraline. The nontricyclic antidepressant, trazodone, also possesses serotonin reuptake inhibiting properties and has been reported to be efficacious in OCD in several case reports and open trials. In order to investigate trazodone's potential antiobsessive efficacy in a controlled fashion, 21 patients with OCD were entered into a double-blind, parallel design comparison of trazodone and placebo. There were no significant differences in baseline rating scores of OCD or depressive symptoms between those who entered the trazodone phase (N = 13) versus those who entered the placebo phase (N = 8). As measured by standardized OCD and depression rating scales, there was no significant difference in OCD or depressive symptoms in the 17 patients who completed 10 weeks of trazodone (N = 11, mean daily dose, 235 +/- 10 mg) versus 10 weeks of placebo (N = 6) administration. In comparison to clomipramine and fluoxetine treatment which we have found to be associated with greater than 95% reduction in platelet 5-HT concentration, there was only a 26% mean reduction in platelet 5-HT concentration after 10 weeks of trazodone administration. These results indicate that trazodone lacks substantial antiobsessive effects and is associated with only modest reductions in platelet 5-HT concentrations.
Anxiogenic effects of m-CPP in patients with panic disorder: comparison to caffeine's anxiogenic effects.
The behavioral and neuroendocrine effects of meta-chlorophenylpiperazine (m-CPP), a serotonergic agonist, were compared with the effects of caffeine, an adenosine antagonist, in panic disorder patients. Patients with panic disorder were given single oral doses of 0.5 mg/kg m-CPP, 480 mg caffeine, and placebo on separate days under double-blind conditions. Both m-CPP and caffeine had significantly greater anxiogenic and panic-inducing effects than placebo, although caffeine produced nonsignificantly greater increases on all anxiety rating scales than m-CPP. Both m-CPP and caffeine produced significant equivalent increases in plasma cortisol concentrations, but only m-CPP produced plasma prolactin increases. These findings provide further evidence implicating both the serotonergic and adenosinergic receptor systems in the neurobiology of panic disorder.
Differential effects of long-term lithium and carbamazepine administration on Gs alpha and Gi alpha protein in rat brain.
The G protein subunits, Gs alpha, Gi alpha, and Go alpha, have been quantitated in various rat brain regions using enzyme-linked immunosorbent assay (ELISA) techniques. Chronic (3-week) treatment with carbamazepine decreased Gs alpha in several brain regions reaching significance in the neostriatum, while chronic lithium treatment had no unequivocal effect. Lithium significantly increased Gi alpha in the hypothalamus and hippocampus, whereas carbamazepine decreased Gi alpha in the frontal cortex. Both treatments had no consistent effects on Go alpha. We conclude that long-term treatment with lithium and carbamazepine exerts differential effects on G protein alpha subunits, and that this modification of signal transduction represents a potential mechanism of antibipolar drug-induced neural plasticity.
Regulation of G proteins by chronic antidepressant drug treatment in rat brain: tricyclics but not clorgyline increase Go alpha subunits.
The effect of long-term (3-week) administration of various antidepressant drugs on the steady-state concentrations of G protein alpha subunits, Gs alpha, Gi alpha, and Go alpha, has been investigated in rat brain using an enzyme-linked immunosorbent assay. Tricyclic antidepressants and clorgyline decreased Gs alpha and, to a lesser extent, Gi alpha in several brain regions, while Go alpha was increased by tricyclics but not clorgyline. We conclude that long-term treatment with antidepressant drugs exerts differential effects on G protein alpha subunits, and that antidepressant efficacy may potentially be based on functional modifications of signal transduction.
A pilot placebo-controlled study of chronic m-CPP administration in Alzheimer's disease.
Meta-Chlorophenylpiperazine (m-CPP), a serotonin agonist and metabolite of the anti-depressant trazodone, was administered chronically to eight moderate to severely affected Alzheimer patients to determine whether it would produce improvement in behavioral symptoms complicating this illness. In doses up to 80 mg/day for 16 days, m-CPP was well tolerated and resulted in small but significant increases in anergy and depression-related symptoms compared with placebo. The effects of chronic m-CPP in this study contrast with the reported beneficial effects of the parent compound trazodone and selective 5-HT reuptake inhibitors in treating behavioral symptoms in Alzheimer patients.
Metergoline blocks the behavioral and neuroendocrine effects of orally administered m-chlorophenylpiperazine in patients with obsessive-compulsive disorder.
The pharmacological probe, meta-chlorophenylpiperazine (m-CPP), administered orally to patients with obsessive-compulsive disorder (OCD) has been shown to induce an acute exacerbation in OCD symptoms as well as an exaggerated anxiogenic response in comparison with controls. The mechanism of m-CPP's behavioral effects in humans remains controversial. To further study m-CPP's actions in OCD patients, we completed a series of double-blind pharmacological challenges in 12 OCD patients. Six OCD patients received four separate challenges: placebo, metergoline, m-CPP, and metergoline plus m-CPP; the second group (n = 6) received metergoline and metergoline plus m-CPP in separate challenges. OCD patients receiving placebo or metergoline alone failed to show evidence of significant changes on any of the behavioral rating scales, in contrast to the patients who received m-CPP alone who exhibited significant increases in anxiety and OCD symptoms. However, the 12 OCD patients who received pretreatment with metergoline before m-CPP experienced no significant changes from baseline OCD symptoms or other behavioral changes. m-CPP's ability to elicit elevations in plasma prolactin was blocked by metergoline pretreatment. Metergoline's ability to block m-CPP's effects on behavior and plasma prolactin lends further support to a serotonergic mediation of m-CPP's effects, including its elicitation of OCD symptoms.
A preliminary study of the effects of nighttime administration of the serotonin agonist, m-CPP, on sleep architecture and behavior in healthy volunteers.
The effects of m-chlorophenylpiperazine (m-CPP) (0.5 mg/kg) on sleep architecture and behavior were examined in six healthy volunteers following a single oral dose of the drug in a randomized, double-blind, placebo-controlled study. m-CPP reduced total sleep time (TST) and sleep efficiency in all subjects. Slow-wave sleep (SWS) and rapid-eye-movement (REM) sleep were decreased and stage 1 sleep was prolonged in a majority of subjects. Prominent behavioral and psychological effects were reported in five out of six subjects following m-CPP (but not following placebo) that interfered with sleep. The sleep disruption and behavioral activation following nighttime administration of m-CPP contrasts with the sedative properties of its parent compound, trazodone, suggesting that the hypnotic effect of trazodone is not related to the agonist profile of its metabolite, m-CPP.
Magnesium reversal of lithium inhibition of beta-adrenergic and muscarinic receptor coupling to G proteins.
Recently, lithium was found to inhibit the coupling of both muscarinic cholinergic and beta-adrenergic receptors to pertussis toxin-sensitive and cholera toxin-sensitive G proteins respectively. These findings suggest that G proteins are the common site for both the antimanic and antidepressant therapeutic effects of lithium. Magnesium ions are crucial to the function of G proteins and interact with them at multiple sites. In the present study using rat cerebral cortex, we determined that magnesium can reverse the ability of lithium to inhibit isoprenaline- and carbamylcholine-induced increases in guanosine triphosphate (GTP) binding to G proteins. Lithium concentrations effective in attenuating G protein function were found to be hyperbolically dependent on free Mg2+ concentrations, suggesting multiple sites of competition between lithium and magnesium on G proteins. Free intracellular Mg2+ concentrations in rat cerebral cortex in vivo are known to be less than 1 mM. At such Mg2+ concentrations, therapeutically efficacious lithium concentrations (1 to 1.5 mM) were still able to alter G protein function, which supports the physiological and clinical relevance of lithium action on G proteins.
Modulation of vocal and nonvocal behavior in adult squirrel monkeys by selective MAO-A and MAO-B inhibition.
The acute effects of monoamine oxidase inhibitors L-deprenyl (0.5-5.0 mg/kg), clorgyline (1.0-10.0 mg/kg), and milacemide (100-400 mg/kg) on the behavior of adult male squirrel monkeys were examined during brief social separations beginning 60 min after subcutaneous drug administration. All three drugs selectively reduced the rate of calling during social separation at doses which did not affect time spent in locomotion, nor the frequency of vigilance-checking. Deprenyl and milacemide, but not clorgyline, produced concurrent decreases in locomotion at the higher doses tested. At threshold doses, clorgyline, but not deprenyl or milacemide, increased call duration and decreased call peak frequency compared to vehicle control values. Plasma levels of MHPG were decreased by an optimal dose of clorgyline but not by deprenyl or milacemide, indicating that substrate specificity was maintained at the drug doses employed. We conclude that different MAO substrates mediate different aspects of vocal and nonvocal behavior in adult male squirrel monkeys.
Neurologic soft signs in obsessive-compulsive disorder.
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Ethanollike properties of the serotonergic partial agonist m-chlorophenylpiperazine in chronic alcoholic patients.
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Plasma amine oxidase activities in Norrie disease patients with an X-chromosomal deletion affecting monoamine oxidase.
Two individuals with an X-chromosomal deletion were recently found to lack the genes encoding monoamine oxidase type A (MAO-A) and MAO-B. This abnormality was associated with almost total (90%) reductions in the oxidatively deaminated urinary metabolites of the MAO-A substrate, norepinephrine, and with marked (100-fold) increases in an MAO-B substrate, phenylethylamine, confirming systemic functional consequences of the genetic enzyme deficiency. However, urinary concentrations of the deaminated metabolites of dopamine and serotonin (5-HT) were essentially normal. To investigate other deaminating systems besides MAO-A and MAO-B that might produce these metabolites of dopamine and 5-HT, we examined plasma amine oxidase (AO) activity in these two patients and two additional patients with the same X-chromosomal deletion. Normal plasma AO activity was found in all four Norrie disease-deletion patients, in four patients with classic Norrie disease without a chromosomal deletion, and in family members of patients from both groups. Marked plasma amine metabolite abnormalities and essentially absent platelet MAO-B activity were found in all four Norrie disease-deletion patients, but in none of the other subjects in the two comparison groups. These results indicate that plasma AO is encoded by gene(s) independent of those for MAO-A and MAO-B, and raise the possibility that plasma AO, and perhaps the closely related tissue AO, benzylamine oxidase, as well as other atypical AOs or MAOs encoded independently from MAO-A and MAO-B may contribute to the oxidative deamination of dopamine and 5-HT in humans.