Search PubMed⌕ Search

Biomedical subjects

R H Belmaker

Publications and source records attributed to R H Belmaker.

At least 19 recordsLinked to original sources
PubMed1992

Failure of addition of lithium to imipramine to enhance activity in rats or mood in normal volunteers.

Lithium powerfully augments the effects of imipramine in resistant depression. We treated four groups of rats for five weeks with (1) saline alone, (2) saline followed by lithium, (3) imipramine alone, and (4) imipramine followed by lithium. There was no augmentation of activity by lithium. Normal human volunteers took imipramine 75 mg daily for three weeks, followed by imipramine 75 mg daily together with lithium 900 mg daily for another ten days. There was no elevation of mood after the addition of lithium. Lithium augmentation of antidepressants apparently requires a pre-existing neurochemical-behavioral disturbance.

Affect↗
PubMed1991

Hyperfunctional G proteins in mononuclear leukocytes of patients with mania.

In a recent study, we found that lithium inhibits the function of guanine nucleotide-binding proteins, implicating G proteins as the common site for both the antimanic and antidepressant therapeutic effects of lithium. These findings may also suggest that an altered G protein function is of pathophysiological importance in bipolar affective disorder. In the present study, the coupling of both muscarinic-cholinergic receptors and beta-adrenergic receptors to pertussis toxin-sensitive G proteins or cholera toxin-sensitive G proteins was compared among untreated manic patients, lithium-treated euthymic bipolar patients, and healthy volunteers using mononuclear leukocyte (MNL) membrane preparations. Hyperactive function of G proteins was detected in untreated manic patients. Both isoproterenol-induced and carbamylcholine-induced increases in Gpp(NH)p binding capacity were twofold to threefold higher than the increases observed in healthy volunteers. On the other hand, lithium-treated euthymic bipolar patients showed G protein responses to agonist activation that were no different from the healthy volunteers. Altered G protein function may be of pathophysiological importance in bipolar affective disorder.

Adenosine Diphosphate↗
PubMed1991

Myo-inositol attenuates two specific behavioral effects of acute lithium in rats.

Acute and chronic lithium treatment reduces levels of brain myo-inositol in rats. Several biological effects of lithium can be reversed in vitro by addition of myo-inositol. The ability of myo-inositol to reverse behavioral effects of lithium was tested using chronic inositol administration or acute intracerebroventricular (i.c.v.) injections. Chronic myoinositol elevated activity during the first 10 min in an open field, but did not reverse lithium-induced hypokinesia. Myo-inositol (i.c.v.) reversed the suppression of rearing behavior 24 hrs after an acute dose of lithium (5 mEq/kg) but did not attenuate hypokinesia 24 hrs after a high dose of lithium (10 mEq/kg). Myo-inositol, but not the inactive isomer chiro-inositol (i.c.v.), also significantly prolonged the latency to clonus in the lithium pilocarpine seizure model. These studies suggest that reduction of brain myo-inositol may be a critical mechanism for the behavioral effects of lithium.

Animals↗
PubMed1990

Intracerebroventricular myo-inositol antagonizes lithium-induced suppression of rearing behaviour in rats.

Several biological effects of lithium have been reversed by in vitro myo-inositol. To determine if intracerebroventricular myo-inositol would reverse behavioural effects of lithium, rats were injected with 5 meq/kg lithium chloride or sodium chloride and injected intracranially with myo-inositol (10 mg) or artificial CSF 24 h and 15 min prior to measurement of activity in an automated activity monitor. Myo-inositol alone had no significant effect on behaviour, but significantly reversed suppression of rearing activity by lithium.

Analysis of Variance↗
PubMed1990

Inhibition by antibiotic tetracyclines of rat cortical noradrenergic adenylate cyclase and amphetamine-induced hyperactivity.

Two antibiotic tetracyclines, demeclocycline (DMC) and minocycline, share several biochemical and behavioral properties with lithium (Li). DMC inhibited both noradrenaline- and chloradenosine-sensitive cyclic AMP accumulation in rat cerebral cortical slices both in vitro and ex vivo following two weeks of chronic dietary treatment. Minocycline, a lipophilic tetracycline, produced similar results in vitro. Both DMC and minocycline reduced open-field activity levels in rats following acute treatment, four hours prior to testing. Moreover, both drugs inhibited amphetamine-induced hyperactivity in the open field. Chronic treatment with 0.4% and 0.8% dietary DMC for two weeks attenuated amphetamine hyperactivity without affecting baseline activity levels in the open field. Neither DMC nor minocycline attenuated apomorphine-induced stereotypy at doses that attenuated amphetamine hyperactivity, a profile which is similar to that of lithium. Unlike lithium, however, DMC did not reverse reserpine-induced hypoactivity.

2-Chloroadenosine↗
PubMed1990

The impact of phenotypic variation on genetic analysis: application to X-linkage in manic-depressive illness.

Genetic linkage studies have opened new vistas for behavioral and psychiatric genetics. However, phenotypic diversity and diagnostic uncertainties can lead to spurious linkage findings. A method of analysis is proposed that takes these factors into account. When applied to manic-depressive disease, the results indicate that previous evidence for a major gene localized on the distal long arm of the X-chromosome cannot be ascribed to phenotypic uncertainties and misclassifications, i.e., a type I error. Although the lod score (the logarithm of odds) favoring linkage is reduced with the more restrictive clinical definitions of the phenotype, it remains significant nonetheless. Thus, the linkage finding is robust over a range of phenotypic patterns and presumed phenocopy frequencies. The results also suggest that the X-linked phenotype is a particularly severe form of manic depression characterized by early onset, high familial prevalence of the bipolar form, and high recurrence rate of major depression. These findings may have important implications for the design and interpretation of genetic linkage studies and for refining diagnostic techniques in mental disorders.

Adolescent↗
PubMed1990

Role of inositol-1-phosphatase inhibition in the mechanism of action of lithium.

Li inhibition of noradrenergic adenylate cyclase may be due to inhibition by Li of agonist-induced increases in GTP binding to G-protein. Such inhibition by Li of G-protein function could have effects on phosphatidyl-inositol-mediated second messenger systems as well as on cyclic AMP-mediated systems. However, Sherman, Berridge and others have proposed that Li affects phosphatidylinositol metabolism by inhibiting inositol-1-phosphatase. We recently have been able to measure inositol-1-phosphatase in human red blood cells. Preliminary data on patients treated with Li compared with controls suggests that the enzyme is indeed inhibited in vivo in patients undergoing Li treatment. However, a series of experiments in rats on addition of inositol to Li treatment did not find that inositol could reverse Li effects. Chronic oral high dose inositol does not reverse Li-induced polyuria (measured by polydipsia), Li-induced weight loss or Li-induced depression of exploratory behavior. These results suggest that Li inhibition of inositol-1-phosphatase indeed occurs in vivo. However, the physiological significance of inositol-1-phosphatase inhibition is not yet established.

Animals↗
PubMed1989

In search of psychological markers of bipolar manic-depressive illness (BMDI): commonalities in psychological functioning between adult euthymic BMDI patients and offspring of BMDI-affected parents.

Detection of probable psychological trait markers of Bipolar Manic Depressive Illness (BMDI) was attempted by conducting two investigations: in the first, Rorschach behavior of adult euthymic BMDI patients was compared with normal control subjects; in the second, Rorschach behavior of nonclinical children of BMDI patients was compared with matched normal controls. Comparison of investigation results revealed psychological characteristics shared by both adult euthymic BMDI patients and clinically-tested children of BMDI-affected parents, including: 1) impaired synthetic functioning; 2) complexity avoidance; 3) experiential and ideational constriction; 4) impaired perceptual accuracy and thought disorder: 5) low conventionalism; and 6) impaired object relatedness.

Adult↗
PubMed1988

Lithium inhibits adrenergic and cholinergic increases in GTP binding in rat cortex.

Lithium is a unique drug with therapeutic as well as prophylactic value for both manic and depressive phases of manic-depressive illness. The precise mechanisms of its clinical efficacy remain unknown, but there are two main theories of its biochemical action. One proposes that lithium inhibits adrenergically activated adenylate cyclase function whereas the other suggests that it inhibits phosphatidyl inositol turnover, which is known to be activated by cholinergic agonists. Neither mechanism alone, however, can explain both the antimanic and antidepressant effects of lithium. Because of the pivotal role of G proteins in post-receptor information transduction, we have investigated the interaction of lithium with G protein function. Lithium at therapeutically efficacious concentrations completely blocked both adrenergic and cholinergic agonist-induced increases in [3H]GTP binding to membranes from rat cerebral cortex, in both in vitro and ex vivo experiments. The same lithium treatments also abolished guanine nucleotide modulation of agonist binding. Our findings suggest G proteins (Gs and Gi or Go) as the molecular site of action for both the antimanic and antidepressant effects of lithium.

Animals↗