Microinjection of arginine-vasopressin into the periaqueductal gray stimulates flank marking in Syrian hamsters (Mesocricetus auratus).

Syrian hamsters can communicate using a distinctive form of scent marking called flank marking. Vasopressin-sensitive neurons within the medial preoptic-anterior hypothalamic continuum (MPOA-AH) play a critical role in the control of this form of olfactory communication. Extrahypothalamic regions may also mediate hamster flank marking. Since the MPOA-AH and the periaqueductal gray (PAG) are reciprocally connected, the present study investigated whether PAG neurons are involved in the control of flank marking. The first study found that microinjection of vasopressin, but not oxytocin or saline, into the PAG induced high levels of flank marking in male (n = 8) and female (n = 5) hamsters (P less than 0.01). The second study demonstrated that microinjection of vasopressin into the PAG stimulated flank marking in a dose-dependent manner in both male (n = 7) and female (n = 11) hamsters (P less than 0.01). These data suggest that vasopressin-responsive neurons within the periaqueductal gray participate in the control of hamster flank marking.