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The alcohol-preferring AA rats have higher concentration of 5-hydroxytryptamine (5-HT) in the brain than the alcohol-avoiding ANA rats. In the present study, the 5-HT1, 5-HT2, and 5-HT3 receptors were studied with [3H]5-HT, [3H]ketanserin, and [3H]LY278584, respectively, in membrane homogenates from different brain regions of both rat lines using in vitro binding assays. No differences in the 5-HT1 and 5-HT2 receptor binding in the brainstem, hippocampus, frontal cortex, and hypothalamus or in the 5-HT3 receptor binding in the nucleus accumbens, amygdala, hippocampus, and frontal cortex were observed between the ethanol-naive animals of the rat lines. In rats given the opportunity to voluntarily consume alcohol, there was a tendency to increase 5-HT1 binding in the ANA rats, which tendency was, however, also found in their ethanol-naive controls subjected to the same handling and behavioral tests as the ethanol-experienced animals. The results do not, however, indicate that any genetic modifications of the 5-HT receptor-binding sites have occurred in the process of the selective breeding of AA and ANA rats for alcohol preference and avoidance, respectively.

A decreased secretion of arginine vasopressin (AVP) has been implicated in depression. In order to further investigate this hypothesis, we studied the plasma level of the specific peptidergic carrier of AVP, vasopressin neurophysin (hNpI), in 26 depressed inpatients and 16 matched normal controls. On the other hand, AVP has also been involved in the pathophysiology of the cortisol postdexamethasone nonsuppression frequently observed in depression. Therefore, we investigated concomitantly hNpI and cortisol during a dexamethasone (DXM) suppression test. hNpI and cortisol were assessed by radioimmunoassay at 8 AM and 8 PM during 4 consecutive days. From days 2 to 3, 4 mg (DXM) was given orally. hNpI values were not affected by DXM administration. Compared with controls, patients showed higher pre- and post-DXM cortisol values and lower hNpI values. No difference in hNpI values was observed between DXM escapers or nonescapers. Our results are consistent with an impaired AVP secretion in depression and fail to support a role of AVP in the early cortisol escape.