Synaptic activation of rat supraoptic neurons by osmotic stimulation of the organum vasculosum lamina terminalis.

Intracellular recordings were obtained from neurons of the supraoptic nucleus in superfused explants of rat hypothalamus in vitro. Transient hyperosmotic stimulation of the organum vasculosum lamina terminalis (OVLT) area caused long-lasting increases in the frequency of excitatory post-synaptic potentials and an associated rise in the rate of action potential discharge. Such responses could be evoked by small (less than + 2%) increases in osmolality, but not by isotonic solutions. These results suggest that the OVLT plays a functional role in the osmoregulation of neurohypophyseal hormone release.