Glutamate and vasopressin interact to control scent marking in Syrian hamsters (Mesocricetus auratus)

In Syrian hamsters, vasopressin (AVP) in the medial preoptic-anterior hypothalamus (MPOA-AH) controls a form of scent marking called flank marking. Another neurochemical signal that may interact with AVP to control flank marking is glutamate. We tested the hypothesis that glutamate interacts with AVP in the MPOA-AH to regulate flank marking. On day 1, AVP was microinjected into the MPOA-AH. On day 2, AVP was microinjected as a cocktail combining either AP-5, a NMDA antagonist, or GAMS, a non-NMDA antagonist or propranolol, a beta norepinephrine antagonist. On day 3, AVP alone was microinjected. Hamsters engaged in high levels of marking in response to AVP alone or to a combination of AVP and propranolol. In contrast, the frequency of marking was significantly reduced in response to a combination of either AVP and AP-5 or AVP and GAMS. These data support the hypothesis that stimulation of flank marking by AVP within the MPOA-AH requires the activity of glutamate.