FUNCTIONAL-INTEGRATION AMONG 5-HYDROXYTRYPTAMINE RECEPTOR FAMILIES INTHE CONTROL OF FEMALE RAT SEXUAL-BEHAVIOR

Serotonin (5-HT) receptor interaction in the control. of female rat lo rdosis behavior was examined. Ovariectomized rats, with bilateral impl ants in the ventromedial nucleus of the hypothalamus (VMN), were hormo nally primed with 25 mu g estradiol benzoate and 500 mu g progesterone . Rats were infused with the 5-HT3 receptor antagonist, 3-tropanyl-ind ole-3 carbonylate (tropisetron; 500 ng), or were coinfused with the 5- HT3 receptor antagonist and the 5-HT2A/2C receptor agonist, 1-(2,5-dim ethoxy-4-iodophenyl)-2-aminopropane (DOI; 500, 1500, or 2000 ng). Addi tional ovariectomized, hormone-primed rats received bilateral VMN infu sions with the 5-MT,, receptor agonist, 8-hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT; 200 ng), or were coinfused with the 5-MT,, recep tor agonist and the 5-HT3 receptor agonist, m-chlorophenyl-biguanide ( mCPBG; 250, 500, or 1000 ng). Lordosis behavior was observed prior to VMN infusion, during the infusion and for 30 consecutive minutes there after. Tropisetron reduced the lordosis to mount (L/M) ratio in every animal investigated but the decline was attenuated by coinfusion with DOI. Similarly, the L/M ratio declined following infusion with 8-OH-DP AT and the decline was dose-dependently reduced by coinfusion with mCP BG. Only the 5-MT, receptor agonist altered the quality of the lordosi s reflex. These studies provide evidence that the effects of 5-HT on f emale rat lordosis behavior involve the integrated activity of at leas t 3 different 5-HT receptor families. (C) 1998 Elsevier Science B.V. A ll rights reserved.