Release of LH in the Female Rat by Olfactory Stimuli

Abstract

The release of LH in ovariectomized, estrogen-primed rats exposed to male or female rats was studied. The concentration of LH in the serum was measured in blood samples obtained by an indwelling jugular cannula. A blood sample was taken at 12.00 h and then every hour up to 18.00 h following exposure to another rat on the opposite side of a double wire mesh screen. LH in the serum of control non-exposed rats showed a small rise between 16.00 and 18.00 h as compared to earlier values. Rats exposed to intact or castrated male rats exhibited an enhanced release. Exposure to ovariectomized rats failed to induce any change in the release of LH but exposure to ovariectomized, estrogen-primed rats produced a significant increase. No effect on LH release was seen in animals exposed to a female diestrous rat or to a pregnant rat. Rats exposed to an empty cage which had been soiled by housing a male rat for 3 days, showed an enhanced release of LH similar to those exposed to a cage containing the male rat, indicating the importance of olfactory stimuli in the response. Ovariectomized rats whose vomeronasal organs had been removed or whose accessory olfactory bulbs were lesioned, failed to show any effect on the release of LH when exposed to a male rat. It is concluded that olfactory stimuli arising from male or female rats are capable of modulating the release of LH in female rats and that perception of these stimuli involves the vomeronasal organ-accessory olfactory bulb system.

Role of the Vomeronasal Organ in the Male-Induced Enhancement of Sexual Receptivity in Female Rats

“…Perception of conspecific male odor by the VNO induces LH release and ovulation in light-induced persistent estrous rats [4] and in ovariectomized EB-primed rats [19], In the present experiment, pairing with males induced LH release in the sham-operated controls; however, LH release was almost totally suppressed in the VNOremoved females. This finding suggests that in ovariectomized estrogen-primed rats, sensory stimulation of the VNO causes release of LHRH from LHRH-containing neurones in the brain.…”

Estrous Cycle Variations in Levels of Cholecystokinin Immunoreactivity within Cells of Three Interconnected Sexually Dimorphic Forebrain Nuclei

“…25, 58, 68]. Consistent with this hypothesis is the fin ding that ablation of the vomeronasal organ or the acces sory olfactory bulb blocks the (male) pheromone-induced stimulation of luteinizing hormone release normally seen in intact female rats [6]. Similarly, ablation of the vomeronasal organ results in reduced lordosis responding [49], although lesions involving the entire olfactory bulb appear to en hance the expression of female copulatory behavior [14,34,37,42], perhaps by altering estrogen receptor binding in the amygdala [36].…”

Removal of the Vomeronasal Organ Impairs Lordosis in Female Hamsters: Effect Is Reversed by Luteinising Hormone-Releasing Hormone

“…Additionally, LHRH immunoreactive fibers project to the interpeduncu lar nucleus and dorsal midbrain, regions which contain neurons strongly responsive to lordosis trigger stimuli, and where lesions impair lordosis in hamsters [29,30]. We can not say whether vomeronasal signals normally lead to the release of LHRH, or whether LHRH influences lordosis in dependently: however, there is evidence which implicates the accessory olfactory system in LHRH release [2][3][4]10] and in raised serum luteinising hormone, an effect that can be prevented by vomeronasal organ removal [5].…”