Neuroendocrine regulation of estrous behavior in the rabbit: similarities and differences with the rat.
In this review, we compare the neuroendocrine control of estrous behavior in the rabbit, a reflex ovulator, and the rat, a more commonly studied spontaneous ovulator. Although the hormonal control of estrous behavior in both species is similar, notable differences include the absence of a stimulatory effect of progesterone (P) on sexual behavior in the rabbit and the retention of sexual behavior in a substantial proportion of female rabbits after ovariectomy. The ventrolateral component of the ventromedial hypothalamus (VMH) and an adjacent region caudal to it appear to be critical estrogen (E)-responsive regions for lordosis in the rat and rabbit, respectively. In both species the effects of E and P are largely mediated by the genomic action of their receptors (ER and PR), and in both species E similarly regulates the expression of these receptors. The prolonged, E-stimulated estrous of the rabbit is terminated after mating by unknown mechanisms, while the brief estrous of the rat is triggered by the proestrous peak of P and terminated by both the decline in P and the downregulation of hypothalamic PR. In both species, P most likely inhibits estrous behavior during pregnancy, and postpartum estrous may be triggered by a stimulatory effect of E coinciding with the withdrawal of P-mediated inhibition. Estrous behavior is inhibited in both species during lactation, most likely by the suckling-induced inhibition of gonadotropin secretion. This comparative approach can reveal neuroendocrine mechanisms underlying estrous behavior that are common to all mammals, while highlighting evolutionary adaptations unique to each species.
Beyer
Carlos
C
Centro de Investigación en Reproducción Animal, CINVESTAV-Universidad Autónoma de Tlaxcala, Apartado Postal 62, Tlaxcala, Tlax. 90000, Mexico. cbeyer34@yahoo.com.mx
Hoffman
Kurt L
KL
González-Flores
Oscar
O
D000818:Animals; D030762:Estrous Cycle / Q000502:physiology*; D005260:Female; D012739:Gonadal Steroid Hormones / Q000494:pharmacology; D007774:Lactation / Q000523:psychology; D008297:Male; D009490:Neurosecretory Systems / Q000502:physiology*; D049590:Postpartum Period / Q000523:psychology; D011817:Rabbits / Q000502:physiology / Q000523:psychology*; D051381:Rats / Q000502:physiology / Q000523:psychology*; D012726:Sexual Behavior, Animal / Q000502:physiology*
D012739:Gonadal Steroid Hormones