Distribution of messenger RNA for the vasopressin V1a receptor in the CNS of male and female rats.

The distribution of cells expressing mRNA encoding a vasopressin V1a receptor (V1aR) was examined in Long-Evans male and female rats by in situ hybridization using a [35S]cRNA probe. Specific hybridization to the vasopressin V1aR mRNA was evident in cells of the frontal cortex, piriform cortex, internal granular layer and the medial, dorsal, ventral and lateral portion of the anterior olfactory nucleus, zona limitans of the islands of Calleja, suprachiasmatic nucleus, CA1, CA2, CA3 and dentate gyrus of the hippocampus, paraventricular hypothalamic nucleus, ventromedial hypothalamic nucleus, arcuate nucleus, lateral habenular nucleus, and the molecular and granular cell layers of the cerebellum. The cerebellum, olfactory nucleus and the dentate gyrus appeared to be the most intensely labeled areas, while all other areas exhibited a lower level of expression. The anatomical distribution and the amount (as measured by optical density) of V1aR mRNA labeling was identical between male and female rats. This indicates that unlike the vasopressin gene itself, the expression of the vasopressin V1aR mRNA does not exhibit sexual dimorphism. These data demonstrate a wide spread distribution in the expression of the vasopressin V1aR mRNA in the CNS of male and female rats. This information on the anatomical distribution of the V1aR mRNA when combined with data concerning the anatomical distribution of the V1a binding sites, provides new information on the possible pre- and post-synaptic location of these neuropeptide receptors.