Ventromedial hypothalamic nucleus lesions disrupt olfactory mate recognition and receptivity in female ferrets

Abstract

Previous research showed that ferrets of both sexes rely on the perception of conspecifics' body odors to identify and motivate approach towards opposite-sex mating partners, and exposure to male body odors stimulated Fos expression in an olfactory projection circuit of female, but not male, ferrets that terminates in the ventromedial hypothalamic nucleus (VMH). We asked whether the female-typical preference of ferrets to approach male as opposed to female body odors in Y-maze tests would be disrupted by VMH lesions. Sexually experienced female ferrets were ovo-hysterectomized prior to receiving bilateral electrolytic lesions of the VMH, the preoptic area/anterior hypothalamus (POA/ AH) or a sham operation. Subsequently, while receiving estradiol benzoate, females that received either complete or partial bilateral lesions of the VMH approached volatile odors from an anesthetized male on significantly fewer trials than females given POA/AH lesions or a sham operation. Both groups of ferrets with VMH lesion damage reliably discriminated between volatile anal scents as well as urinary odors from the 2 sexes in home cage habituation/dishabituation tests, suggesting that their odor-based sex discrimination remained intact. Females with complete bilateral VMH lesions showed significantly lower acceptance of neck gripping from a stimulus male (receptivity) and more aggression towards the male than all other groups of female subjects. Estrogen-sensitive neurons in the VMH appear to play a central role in female-typical neural processing of odor inputs leading to a preference to seek out a male sex partner, in addition to facilitating females' sexual receptivity.

Bilateral damage to the sexually dimorphic medial preoptic area/anterior hypothalamus of male ferrets causes a female-typical preference for and a hypothalamic Fos response to male body odors

“…In a recent study [24] bilateral electrolytic lesions of the VMH eliminated the preference of ovariectomized, estradiol-treated female ferrets to approach an anesthetized male as opposed to a female ferret in Y-maze tests identical to those run in the present experiment. In contrast to the effects of bilateral MN-POA/AH damage in male ferrets (present study), placement of VMH lesions in females eliminated their preference to approach male odors but did not motivate them to seek out same-sex (female) odors.…”

Roles of sex and gonadal steroids in mammalian pheromonal communication

“…Two additional studies examined the effects of lesioning different hypothalamic regions on the preference of female and male ferrets to seek out same-vs. opposite-sex pheromones in operant tests. Thus, bilateral lesions of the VMH (but not of the mPOA) in female ferrets blocked their preference to seek out male vs. female volatile pheromones, without disrupting subjects' ability to discriminate between these same odors when they were presented sequentially in habituation/dishabituation tests (Robarts and Baum, 2007). By contrast, bilateral lesions of the sexually dimorphic male nucleus of the POA/AH (Kindon et al, 1996;Paredes and Baum, 1995) actually reversed the normal heterosexual odor preference of male ferrets so that after receiving this lesion they preferred to approach volatile odors from other males (homosexual preference).…”

The Vertebrate mesolimbic reward system and social behavior network: A comparative synthesis

“…The best understood function of the VMH in social behavior is its central role in regulating female receptivity. Lesions will decrease receptivity in females (Malbury et al, 1977;Mathews and Edwards, 1977;Pfaff and Sukuma, 1979;Leedy and Hart, 1985;Robarts and Baum, 2007), while stimulation will facilitate lordosis (Pfaff and Sakuma, 1979). The VMH also regulates nonsexual behavior, as lesions will increase aggressive behavior and feeding (Panksepp et al, 1970;Malsbury et al, 1977).…”