The participation of the muscarinic receptors in the preoptic-anterior hypothalamic areas in the regulation of ovulation depends on the ovary.
BACKGROUND
Muscarinic receptors (mAChRs) of the preoptic and anterior hypothalamus areas (POA-AHA) regulate ovulation in an asymmetric manner during the estrous cycle. The aims of the present study were to analyze the effects of a temporal blockade of mAChRs on either side of the POA-AHA performed in diestrus-2 rats on ovulation, the levels of estradiol, follicle stimulating hormone (FSH) and luteinizing hormone (LH) and the mechanisms involved in changes in ovulation.


METHODS
Cyclic rats on diestrus-2 day were anesthetized and randomly assigned to the following groups: 1) microinjection of 1 μl of saline or atropine solution (62.5 ng) in the left or right POA-AHA; 2) removal (unilateral ovariectomty, ULO) of the left (L-ULO) or right (R-ULO) ovary, and 3) rats microinjected with atropine into the left or right POA-AHA plus L-ULO or R-ULO. The ovulation rate and the number of ova shed were measured during the predicted estrus, as well as the levels of estradiol, FSH and LH during the predicted proestrus and the effects of injecting synthetic LH-releasing hormone (LHRH) or estradiol benzoate (EB).


RESULTS
Atropine in the left POA-AHA decreased both the ovulation rate and estradiol and LH levels on the afternoon of proestrus, also LHRH or EB injection restored ovulation. L- or R-ULO resulted in a lower ovulation rate and smaller number of ova shed, and only injection of LHRH restored ovulation. EB injection at diestrus-2 restored ovulation in animals with L-ULO only. The levels of estradiol, FSH and LH in rats with L-ULO were higher than in animals with unilateral laparotomy. In the group microinjected with atropine in the left POA-AHA, ovulation was similar to that in ULO rats. In contrast, atropine in the right POA-AHA of ULO rats blocked ovulation, an action that was restored by either LHRH or EB injection.


CONCLUSIONS
These results indicated that the removal of a single ovary at noon on diestrus-2 day perturbed the neuronal pathways regulating LH secretion, which was mediated by the muscarinic system connecting the right POA-AHA and the ovaries.
Biology of Reproduction Research Unit, Laboratory of Neuroendocrinology, Facultad de Estudios Superiores Zaragoza, UNAM, AP 9-020, CP 15000, Mexico City, Mexico.
Adriana
A
Espinosa-Valdez
Biology of Reproduction Research Unit, Laboratory of Neuroendocrinology, Facultad de Estudios Superiores Zaragoza, UNAM, AP 9-020, CP 15000, Mexico City, Mexico.
Angélica
A
Flores
Department of Basic Research, National Institute of Geriatrics, México City, Mexico.
Isabel
I
Arrieta-Cruz
Instituto Nacional de Ciencias Médicas y Nutrición "Salvador Zubirán", México City, Mexico.
Mario
M
Cárdenas
Instituto Nacional de Ciencias Médicas y Nutrición "Salvador Zubirán", México City, Mexico.
Roberto
R
Chavira
Biology of Reproduction Research Unit, Laboratory of Neuroendocrinology, Facultad de Estudios Superiores Zaragoza, UNAM, AP 9-020, CP 15000, Mexico City, Mexico.
Roberto
R
Domínguez
Biology of Reproduction Research Unit, Laboratory of Neuroendocrinology, Facultad de Estudios Superiores Zaragoza, UNAM, AP 9-020, CP 15000, Mexico City, Mexico. mecbloy@yahoo.com.mx.
María Esther
ME
Cruz
D000818:Animals; D007025:Anterior Hypothalamic Nucleus / Q000187:drug effects / Q000378:metabolism*; D001285:Atropine / Q000494:pharmacology; D003270:Contraceptive Agents / Q000494:pharmacology; D004031:Diestrus / Q000187:drug effects / Q000378:metabolism*; D004958:Estradiol / Q000031:analogs & derivatives / Q000378:metabolism* / Q000494:pharmacology; D005260:Female; D005640:Follicle Stimulating Hormone / Q000378:metabolism*; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology; D007986:Luteinizing Hormone / Q000187:drug effects / Q000378:metabolism*; D018727:Muscarinic Antagonists / Q000494:pharmacology; D010052:Ovariectomy; D010053:Ovary / Q000187:drug effects; D010060:Ovulation / Q000187:drug effects / Q000378:metabolism*; D011301:Preoptic Area / Q000187:drug effects / Q000378:metabolism*; D011359:Proestrus / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D011976:Receptors, Muscarinic / Q000187:drug effects / Q000378:metabolism*
D003270:Contraceptive Agents; D018727:Muscarinic Antagonists; D011976:Receptors, Muscarinic; C074283:estradiol 3-benzoate; D007987:Gonadotropin-Releasing Hormone; D004958:Estradiol; D001285:Atropine; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone
Atropine; Diestrus-2; Estradiol; Gonadotropins; Muscarinic receptors; Ovulation; POA-AHA; Unilateral ovariectomy