Salusin-β stimulate the neurohypophyseal hormone release from the rat neurohypophysis

Abstract

Salusin-α, and -β were newly discovered as bioactive endogenous peptides (Shichiri et al., 2003). Salusin-β stimulates the secretion of arginine vasopressin (AVP) from perifused rat hypophysis, and coexists with AVP in the rat hypothalamic magnocellular supraoptic (SON) and paraventricular nuclei. In the present study, we investigated the effects of osmotic stimuli on salusin-β-like immunoreactivity (LI) in the rat hypothalamo-neurohypophyseal system, and also examined the effects of salusin-β on the synaptic inputs to the rat magnocellular neurosecretory cells (MNCs) of the SON and the AVP / oxytocin (OXT) release from the rat freshly dissociated SON and neurohypophysis. We demonstrated that salusin-β-LI exhibited markedly increase in the hypothalamo-neurohypophyseal system after osmotic stimuli, and evoked AVP / OXT releases from the neurohypophysis, but not cause significant changes in the excitatory and inhibitory postsynaptic currents of the MNCs. These results suggest that salusin-β is increased by osmotic stimuli, secreted from nerve endings, acting as autocrine / paracrine modulator to stimulate the AVP / OXT release from the neurohypophysis and involved in the regulation of water balance. [J Physiol Sci. 2007;57 Suppl:S172]