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The binding of [3H]WIN 35,428 was studied in post-mortem human brain, including extrastriatal regions. In the putamen, dopamine almost completely inhibited the [3H]WIN 35,428 binding. Paroxetine inhibited the binding with similar affinity as cocaine, in the range 200-300 nM. In the frontal cortex, [3H]WIN 35,428 labelled cocaine- and alaproclate sensitive binding sites, of which a major fraction was of protein nature. The elucidation of the cocaine sensitive sites in the frontal cortex should be the subject of further research.

Basal and stimulated adenylyl cyclase activities and Gs and Gi protein alpha-subunit levels (Gs alpha and Gi alpha) were compared in postmortem frontal cortex from 18 suicide cases and 22 matched controls. Basal, guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S) stimulated and forskolin stimulated enzyme activities were significantly lower in the suicide cases, compared to controls. These effects were most apparent in those suicides that had died from violent means or that had had a history of depression and appeared to reflect the lowered basal activity rather than a reduced ability of either GTP gamma S or forskolin to activate the enzyme. No significant correlations were found between adenylyl cyclase activity and either subject age or postmortem delay. Western blotting revealed no significant differences in Gs alpha and Gi alpha levels between control and suicide cases. However, levels of the smaller Gs alpha isoform (Gs alpha-S) showed a tendency to be increased in the violent death suicide and depressed suicide subgroups, compared to controls. Levels of the larger Gs alpha isoform (Gs alpha-L) showed a significant positive correlation with subject age. Gi alpha levels showed a significant negative correlation with subject age and a positive correlation with postmortem delay. These results support the hypothesis that suicidal behaviour and depressive illness may be associated with an altered regulation of adenylyl cyclase.

Recently, a high-affinity [3H]imipramine binding site of protein nature that appeared related to the 5-hydroxytryptamine (5-HT, serotonin) uptake mechanism was demonstrated in the rat brain. In a preceding paper a similar [3H]imipramine binding site of protein nature and displaceable by 5-HT was demonstrated in the human brain. Most previous [3H]imipramine binding studies of the human brain have used desipramine-sensitive binding, which appears to contain a significant amount of additional binding not related to 5-HT neurons. Therefore this study of the human brain in the normal aging, in Alzheimer's disease/senile dementia of Alzheimer type (AD/SDAT) and in multiinfarction dementia (MID) presents data on 5-HT-sensitive [3H]imipramine binding. The influence of normal aging (17-100 years) was studied in the frontal and cingulate cortices, in the putamen, caudate nucleus, amygdala and in the hippocampus. An age-related change in 5-HT-sensitive [3H]imipramine binding was only noted in the cingulate cortex with a 50% loss in Bmax over the adult age range. In contrast, desipramine-sensitive [3H]imipramine binding studied in the frontal cortex and in the putamen showed marked increases in Bmax with age which correlated with increases in Kd. It is suggested that these increases are related to an increased binding to lipophilic membrane components not related to 5-HT neurons. The 5-HT-sensitive [3H]imipramine binding (Bmax) was reduced to 60% of control in the cingulate cortex and to 50% in the putamen in AD/SDAT. In MID there was a 50% loss of [3H]imipramine binding sites (Bmax) in the putamen, but a 30% loss in the cingulate cortex did not reach statistical significance.(ABSTRACT TRUNCATED AT 250 WORDS)

Serotonin (S-2) binding sites were characterized in human frontal cortex and hippocampus throughout the lifespan. We found that the S-2 binding sites (labeled by [3H]spiperone and displaced by ketanserin) consisted of two subtypes (S-2A and S-2B) which are discriminated by competition with methysergide. The total S-2 sites in frontal cortex had a Bmax of 360 fmol/mg protein, which is approximately twice that of the hippocampus (160 fmol/mg protein). The density of total S-2 sites decreased with age in the frontal cortex of normal adults (17-100 years, n = 24). The receptor loss was primarily in the S-2A subclass. This loss of S-2A sites occurred primarily after 60 years and decreased to 50% of young adult values by the 10th decade. In the hippocampus, S-2A binding sites decreased with age, but no effects on total S-2 or S-2B sites were detected. A study of infant brains suggested the S-2A subtype in frontal cortex increases postnatally. However, in the infant hippocampus the S-2 binding approximated adult levels.

[3H]Imipramine binding sites were characterized in the human brain by investigating the sensitivity to protease treatment, dependency on NaCl and the effects of drug inhibition. The binding was found to consist of a protease sensitive and a protease resistant fraction. These two fractions could be discriminated by 5-hydroxytryptamine (5-HT) but not desipramine. The [3H]imipramine binding discriminated by 5-HT was found to be sodium dependent. The 5-HT-sensitive [3H]imipramine binding displayed a regional variability with Bmax values ranging from 50 to 100 fmol/mg protein in neocortical areas to 400-500 fmol/mg protein in the substantia nigra and hypothalamus. The Kd values for 5-HT-sensitive [3H]imipramine binding were 1-2 nM throughout the brain. Additional [3H]imipramine binding insensitive to 5-HT, but displaceable by desipramine showed little regional variation, with the binding capacity in the hypothalamus approximating that found in cortical areas. This binding fraction was of low affinity, was not dependent on the presence of NaCl and was insensitive to protease treatment. Drug inhibition studies revealed that the addition of low concentrations of 5-HT or norzimeldine to 5-HT-sensitive [3H]imipramine binding sites produced changes in affinity, consistent with a competitive interaction. It is suggested that the 5-HT-sensitive [3H]imipramine binding may represent the substrate recognition site for 5-HT uptake in the human brain.