Characterisation of vasopressin V1a binding sites in the ovine olfactory bulb.

In the ewe, [Arg8]vasopressin (AVP) release into the olfactory bulb (OB) modulates transmitter release necessary for the induction of olfactory memory. [3H]AVP binding to a microsomal preparation of ovine OB revealed saturable binding to a single class of high affinity sites (Kd = 2.03 +/- 0.18 nM). The density of binding sites was significantly greater in the lamb than ewe, but did not vary across the adult oestrous cycle. Displacement using AVP analogues showed that their relative affinities for the ovine V1a receptor were identical to the rat hepatic V1a receptor. These data demonstrate a single class of AVP binding sites in the ovine OB and the first pharmacological characterisation of the ovine V1a receptor.