Axonal projections from the organum vasculosum lamina terminalis to the supraoptic nucleus: Functional analysis and presynaptic modulation

1. The rat organum vasculosum lamina terminalis (OVLT) contains GABA- and glutamate-releasing neurons that project directly to magnocellular neurosecretory cells (MNC) in the supraoptic nucleus. 2. Changes in osmolality over the OVLT in hypothalamic explants cause proportional changes in firing in MNC through corresponding changes in the frequency of spontaneous glutamatergic excitatory post-synaptic potentials without affecting GABAergic inhibitory post-synaptic potentials. 3. Exogenously applied atrial natriuretic peptide inhibits the osmotic control of MNC by causing a decrease in the amount of glutamate released provoked by action potentials originating from OVLT neurons.