The immunological impairment of vasopressin (AVP) neurons into paraventricular nuclei modifies AVP expression in suprachiasmatic nuclei

A monoclonal antibody (MAb) to vasopressin (AVP) inhibits the synthesis and the release of AVP when injected near the AVP-producing neurons. In the present experiments, the AVP-MAb was microinjected near the paraventricular (PVN) or the supraoptic (SON) neurons of the rat hypothalamus and the AVP expression was measured in the suprachiasmatic nuclei (SCN). When microinjected near PVN, the AVP-MAb modified the AVP mRNA studied by in situ hybridization, and the AVP immunoreactive content of SCN, whereas it failed to show some effect when injected near SON. This confirms the privileged relationships between AVP-producing neurons in SCN and PVN.