GREATER ABUNDANCE OF SEROTONIN(1A) RECEPTOR IN SOME BRAIN-AREAS OF ALCOHOL-PREFERRING (P) RATS COMPARED TO NONPREFERRING (NP) RATS

Saturable [H-3]8-OHDPAT binding to recognition sites of 5-HT1A receptors was shown to be higher in cortical membranes of alcohol-preferring (P) than in membranes of alcohol-nonpreferring (NP) rats. Neither the P nor the NP lines had been previously exposed to ethanol. The increase in binding was mainly due to 40-56% higher density or maximum of binding sites (B(max)) without significant change in affinity or dissociation constant (K(d)) for the radioligand. Although B(max) values were also consistently higher in membranes isolated from other brain areas of P rats, including hypothalamus, striatum, and hippocampus, the differences did not reach statistical significance. Similar to the previously reported lack of difference in [H-3]ketanserin binding to 5-HT2 receptors in cortical membranes from P and NP rats, there were also no significant differences in saturable binding of [H-3]mesulergine and [H-3]LY278584 to recognition sites of 5-HT1C and 5-HT3 receptors, respectively. Thus, an upregulation of 5-HT1A receptors in cerebral cortex and possibly in other brain areas of ethanol-naive P rats appears to have occurred as a consequence of the lower 5-HT innervation in this selected line of rats (13,15,27,28).