Ibotenic acid-induced lesions of the medial preoptic area/anterior hypothalamus enhance the display of progesterone-facilitated lordosis in male rats.
Electrical lesions of the medial preoptic area/anterior hypothalamus (MPOA/AH) have been reported to enhance the display of steroid-induced lordosis in castrated male rats. This study employed the cell body-specific neurotoxin, ibotenic acid, to ascertain whether neurons originating in this region (as opposed to axons of passage) tonically inhibit steroid-induced lordosis in adult male rats. Castrated, adult Long-Evans males received bilateral electrical lesions or injections of ibotenic acid or vehicle aimed at the MPOA/AH. Following administration of estradiol benzoate (EB) and progesterone, lordosis quotients (LQs) and lordosis ratings (LRs) were significantly higher in groups of rats with electrical lesions (LQ = 62.2 +/- 15.1; LR = 1.22 +/- 0.34) and ibotenic acid-induced lesions (LQ = 58.1 +/- 12.2; LR = 0.99 +/- 0.24) than in the control group (LQ = 12.8 +/- 7.3; LR = 0.22 +/- 0.13). To determine whether this enhancement of receptive behavior in MPOA/AH-lesioned males was an effect on estradiol-induced, as compared to progesterone-facilitated lordosis, groups of castrated rats in a second experiment received bilateral injections of ibotenic acid or vehicle aimed at the MPOA/AH and were tested for lordosis after administration of EB alone and again after injection of progesterone. Following treatment with EB alone, rats with ibotenic acid-induced MPOA/AH lesions tended to be slightly less receptive than control animals. However, following injections of progesterone, LQs and LRs were higher in the MPOA/AH-lesioned group than in the control animals, as had been observed in the first experiment.(ABSTRACT TRUNCATED AT 250 WORDS)
Olster
D H
DH
Psychology Department, University of California, Santa Barbara 93106.
D000818:Animals; D004558:Electric Stimulation; D004958:Estradiol / Q000494:pharmacology*; D007051:Ibotenic Acid; D008297:Male; D011187:Posture; D011301:Preoptic Area / Q000502:physiology*; D011374:Progesterone / Q000494:pharmacology*; D051381:Rats; D012733:Sex Differentiation / Q000187:drug effects; D012726:Sexual Behavior, Animal / Q000187:drug effects*
D007051:Ibotenic Acid; D011374:Progesterone; D004958:Estradiol