title: Possible role of inhibitory glycinergic neurons in the regulation of lordosis behavior in the rat.
abstract: Strychnine sulfate (3.9 or 27 micrograms in 0.5 microliter saline) was bilaterally infused into the ventromedial hypothalamic nucleus (VMH) of ovariectomized sexually inexperienced rats primed 40 hr earlier with 4 micrograms of estradiol benzoate (EB). This dose of EB induced only weak lordosis behavior in 25% of the subjects (Ss). Strychnine at the 3 and 9 micrograms dosages, but not at 27 micrograms, induced intense lordosis behavior, but no proceptivity, in most estrogen-primed Ss (69% in 3 micrograms, 94% in 9 micrograms). Ovariectomized adrenalectomized EB-primed Ss also displayed significant lordosis behavior (59%) following infusion of 9 micrograms of strychnine into the VMH. Strychnine (9 micrograms) failed to stimulate lordosis in ovariectomized Ss that were not estrogen-primed. Administration of 5 micrograms EB followed 40 hr later by 2 mg of progesterone (P) elicited intense lordosis behavior in most Ss. Bilateral injections into the VMH of glycine (100 micrograms), beta-alanine (100 micrograms) or taurine (50 micrograms) to rats that were already displaying estrous behavior (greater than 80 LQ) in response to the sequential administration of EB and P failed to depress lordosis when tested between 5 min and 60 min postinjection. Similarly, glycine (20 or 100 micrograms) injected into the VMH of estrogen-primed, ovariectomized rats within 15 minutes of a 2 mg SC injection of P failed to interfere with the subsequent response to this steroid when tested 2 and 4 hr after P. The results suggest that strychnine injected into the VMH facilitates lordosis behavior in estrogen-primed rats by removing a tonic inhibitor effect exerted by glycinergic neurons on VMH neurons.(ABSTRACT TRUNCATED AT 250 WORDS)
authors: Centro de Investigacion en Reproduccion Animal, CINVESTAV-UAT, Tlaxcala, Mexico.
authors: Y
authors: Y
authors: Sandoval
authors: B
authors: B
authors: Komisaruk
authors: C
authors: C
authors: Beyer
mesh_terms: D000818:Animals; D004958:Estradiol / Q000494:pharmacology; D005260:Female; D005998:Glycine / Q000494:pharmacology / Q000502:physiology*; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D010053:Ovary / Q000502:physiology; D011187:Posture; D051381:Rats; D011919:Rats, Inbred Strains; D012726:Sexual Behavior, Animal / Q000187:drug effects / Q000502:physiology*; D013331:Strychnine / Q000494:pharmacology; D014697:Ventromedial Hypothalamic Nucleus / Q000187:drug effects / Q000502:physiology
chemical_list: D004958:Estradiol; D013331:Strychnine; D005998:Glycine