Abstract
An attempt was made to elucidate the role of an area located in the medial basal prechiasmatic area (PVA), which includes the organum vasculosum laminae terminalis of the circumventricular organ, in the regulation of gonadotropins and prolactin. Experimental animals were Wistar female rats maintained under controlled lighting. LH, FSH and prolactin in serum and pituitary were determined by means of double antibody radioimmunoassay. The results were as follows: 1) Electrical stimulation (100Hz, 0.1ms and 100μA) of the PVA through chronically implanted electrode at 12:00 on the day of proestrus increased the serum concentrations of LH and prolactin, but not FSH. 2) Rats with neural isolations of the PVA by a small J-shaped knife resumed their 4-day cycles within 5 to 7 weeks, but some of rats had abnormal uterine balooning on the day of estrus. 3) In such rats with the isolations, serum and pituitary concentrations of FSH on the day of proestrus were significantly higher than those of control rats, while on the day of estrus they were not different. 4) In these rats, the increase of LHconcentration in serum 2 weeks after bilateral ovariectomy was significantly lower than that in the ovariectomized intact rats. 5) Implantation of minute amounts of estradiol into the PVA prevented an elevation of serum concentration of LH and FSH, which occurred after bilateral ovariectomy.
From these results, it may be concluded that the PVA is involved in the mechanism to cause LH and prolactin release. Regarding FSH release, the role of the PVA was not clear in this experiment. These aspects and an electrical phenomenon, that multiple unit activity of this area showed a marked similarity to that of the arcuate nucleus during the critical period of proestrus, and that there exists a monosynaptic connection between the PVA and the arcuate nucleus, may provide an evidence that the PVA has some similarity to the arcuate nucleus in the function controlling gonadotropin and prolactin release, and furthermore that the PVA exerts its activity to release gonadotropin through the median eminence-arcuate region.
