Differential involvement of noradrenaline and nitric oxide in the regulation of vasopressin and oxytocin expression in rat supraoptic nucleus.

The hydroosmotic balance of the body is controlled by supraoptic nuclei and paraventricular nuclei of the hypothalamo-posthypophyseal complex. In response to a physiological stimulation such as an osmotic stress, the supraoptic nuclei (SON) and the paraventricular nuclei undergo remarkable neurochemical and morphological changes. Therefore, the neuroendocrine hypothalamus is a particularly relevant model for studying the molecular and cellular mechanisms that govern these plasticity phenomena. Slices of rat hypothalamus maintained ex vivo by perfusion were used to study the short-term involvement of noradrenaline (NA) and nitric oxide (NO) in the mechanisms of chemical plasticity of the SON. NA is involved early in the regulation of the expression of neuropeptides, including vasopressin (AVP) and oxytocin (OT). NO appears to be a key molecule in noradrenergic control of the chemical plasticity of the endocrine neurons: in the SON, NO is involved in the signaling pathway regulating the expression of AVP but not that of OT.