Effect of brain-derived neurotrophic factor on inhibitory synaptic input into the magnocellular neurosecretory cells in the rat supraoptic nucleus

Abstract

The hypothalamic supraoptic nucleus (SON) is one of the major sites for synthesis of arginine vasopressin (AVP), and secretion of AVP is controlled by the electrical activities of magnocellular neurosecretory cells (MNCs), which in turn is regulated by neuronal excitatory and inhibitory synaptic inputs and humoral factors. Brain-derived neurotrophic factor (BDNF) mRNA was markedly increased by osmotic stress in the SON. In the present study, we examined the effect of hyper- and hypo-osmotic stimuli on spontaneous inhibitory postsynaptic currents (sIPSCs) recorded from the MNCs in the rat SON, using whole-cell patch-clamp techniques in in vitro brain slice preparation. We also examined the effect of BDNF on sIPSCs recorded from the MNCs in the rat SON. (1) The frequency of sIPSCs, but not amplitude, was significantly increased by hypo-osmotic stimuli (250 mOsm/kg) after hyper-osmotic incubation (350 mOsm/kg) for more than 2 hours. This response was inhibited partially by the application of ruthenium red (10 μM), an inhibitor of the transient receptor potential vanilloid (TRPV) cation channels. (2) The frequency of sIPSCs, but not amplitude, was significantly decreased by the application of BDNF (2 nM). These results suggest that osmotic stimuli regulate the inhibitory synaptic transmission to the MNCs in the SON and BDNF may have a role on this regulation. [J Physiol Sci. 2008;58 Suppl:S130]