The medial preoptic area is necessary for sexual odor preference, but not sexual solicitation, in female Syrian hamsters

Abstract

Precopulatory behaviors that are preferentially directed towards opposite-sex conspecifics are critical for successful reproduction, particularly in species wherein the sexes live in isolation, such as Syrian hamsters (Mesocricetus auratus). In females, these behaviors include sexual odor preference and vaginal scent marking. The neural regulation of precopulatory behaviors is thought to involve a network of forebrain areas that includes the medial amygdala (MA), the bed nucleus of the stria terminalis (BNST), and the medial preoptic area (MPOA). Although MA and BNST are necessary for sexual odor preference and preferential vaginal marking to male odors, respectively, the role of MPOA in odor-guided female precopulatory behaviors is not well understood. To address this issue, female Syrian hamsters with bilateral, excitotoxic lesions of MPOA (MPOA-X) or sham lesions (SHAM) were tested for sexual odor investigation, scent marking, and lordosis. MPOA-X females did not investigate male odors more than female odors in an odor preference test, indicating that MPOA may be necessary for normal sexual odor preference in female hamsters. This loss of preference cannot be attributed to a sensory deficit, since MPOA-X females successfully discriminated male odors from female odors during an odor discrimination test. Surprisingly, no deficits in vaginal scent marking were observed in MPOA-X females, although these females did exhibit decreased overall levels of flank marking compared to SHAM females. Finally, all MPOA-X females exhibited lordosis appropriately. These results suggest that MPOA plays a critical role in the neural regulation of certain aspects of odor-guided precopulatory behaviors in female Syrian hamsters.

Endogenous oxytocin is necessary for preferential Fos expression to male odors in the bed nucleus of the stria terminalis in female Syrian hamsters

“…We have found that injections of OTA into either MPOA-AH or BNST decreased vaginal marking to male, but not female odors (Martinez et al, 2010). Furthermore, in hamsters binding sites for oxytocin are present in BNST, but not MPOA-AH, (Dubois-Dauphin et al, 1992), and as mentioned above, lesions of BNST, but not MPOA, disrupt vaginal marking responses to sexual odors (Martinez and Petrulis, 2011, 2013). Considered together, it seems likely that oxytocin acts within BNST to regulate vaginal marking responses to male odors; however, the underlying mechanisms underlying this effect are not known.…”

“…Lesions centered on MA decrease overall levels of vaginal marking (Petrulis and Johnston, 1999), whereas lesions of BNST specifically decrease vaginal marking in response to male, but not female odors (Martinez and Petrulis, 2011). In contrast, lesions of MPOA do not affect the expression of vaginal marking, although this area is important for other forms of proceptive behaviors in female hamsters (Floody, 1989; Martinez and Petrulis, 2013). …”

“…Once the day of behavioral estrus was identified, the two cycle days prior to estrus were defined as diestrous day 2 and proestrus, respectively (Johnston, 1977). It has been our experience that this technique for determining estrous cycle stage correctly predicts the day of behavioral receptivity with perfect accuracy (Martinez and Petrulis, 2011, 2013). …”

“…Proestrus was chosen for stimulus exposures because females exhibit the highest overall levels of vaginal marking on this cycle day (Johnston, 1977; Martinez and Petrulis, 2011, 2013). Subjects were handled for at least eight consecutive days prior to exposure.…”

Pharmacology of serotonin and female sexual behavior

“…In the medial preoptic area (mPOA), a brain area that several authors have argued contributes significantly to sexual motivation (Guarraci and Clark, 2006; Kato and Sakuma, 2000; Martinez and Petrulis, 2013), infusion of 8-OH-DPAT (at relatively high concentrations) reduced lordosis behavior but less efficiently than following MBH infusions (Uphouse and Caldarola-Pastuszka, 1993). Proceptivity, however, was reduced and the female’s resistance to the male’s attempt to mount was increased.…”