Chemosensory Stimulation of Luteinizing Hormone (LH)

22 Male Siberian hamsters (Phodopus sungorus) housed in long days (LD), but not short 23 days (SD) release luteinizing hormone (LH) when exposed to females. This study examined 24 whether this response is specific to a female and identifies the source of a stimulus that induces 25 LH release. Serum concentrations of LH, testosterone (T), follicle stimulating hormone (FSH), 26 and cortisol were examined in all experiments. T concentrations mirrored the LH response; FSH 27 and cortisol were unchanged in response to all stimuli. Exposure to an LD female, irrespective 28 of her reproductive status, but not an SD female, elicited LH release. Exposure to another male 29 did not trigger LH release. Males released LH when allowed physical contact with an 30 anesthetized female, but not when separated from a normally active female, suggesting that 31 tactile or nonvolatile chemosensory stimuli elicit LH release. Urine and secretions collected 32 from the vagina as well as oral, midventral, perineal, and rectal glands, elicited marked 33 behavioral responses in male P. sungorus. Despite these behavioral responses, only feces from 34 females elicited LH release in males. Males released LH in response to feces extracted from the 35 rectum and to cotton swabs that had been rubbed against the rectal mucosa, suggesting that a 36 component of rectal secretions may trigger LH release in male Siberian hamsters. Taken 37 together these data and previous data from our laboratory indicate that both the production of and 38 the response to a pheromone that triggers the selective release of LH is regulated by day length. 39