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 recepto rs 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 increas e in binding was mainly due to 40-56% higher density or maximum of bin ding sites (B(max)) without significant change in affinity or dissocia tion 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 diff erences did not reach statistical significance. Similar to the previou sly reported lack of difference in [H-3]ketanserin binding to 5-HT2 re ceptors in cortical membranes from P and NP rats, there were also no s ignificant differences in saturable binding of [H-3]mesulergine and [H -3]LY278584 to recognition sites of 5-HT1C and 5-HT3 receptors, respec tively. Thus, an upregulation of 5-HT1A receptors in cerebral cortex a nd possibly in other brain areas of ethanol-naive P rats appears to ha ve occurred as a consequence of the lower 5-HT innervation in this sel ected line of rats (13,15,27,28).