Primer pheromones in the levant vole (microtus guentheri): activation of reproduction in the female by male-related stimuli

Abstract

Virgin females of the Levant vole (Microtus guentheri), 2–4 months old and raised from weaning in an all-female group, responded to nonvisual male stimuli by an open vagina; the response fluctuated between 5–15% and 30–60%, depending on the stimulation. The priming effect of male-related stimuli on the activation of the female reproductive system was examined using uterine weight as a parameter. In unstimulated virgin females 55–75 days of age raised in an all-female group, the uterine weight showed a temporary spontaneous increase in weight of approximately 45%. Induced increase in uterine weight in such females following stimulation by licking a drop of urine from an intact experienced male was also the strongest at this age. This showed a special sensitivity of the female reproductive system to male stimulation soon after sexual maturation, occurring at the age of about 50 days. Females 55–75 days of age responded with a significant increase in uterine weight already after 1.5 min with an intact experienced male in a cage. The increase in uterine weight was similar whether it was caused by smelling an experienced male’s urine, by chewing a dry filter paper previously impregnated with the urine, or by licking a drop of it. Licking a mixture of fresh male feces in water had no effect. The involvement of the vomeronasal organ in the pheromonal perception was discussed.