CHANGES IN ARTERIAL BLOOD-PRESSURE ALTER ACTIVITY OF ELECTROPHYSIOLOGICALLY IDENTIFIED SINGLE UNITS OF THE BED NUCLEUS OF THE STRIA TERMINALIS

The bed nucleus of the stria terminalis may play a role in cardiovascu lar function by way of its connectivity to the diagonal band of Broca/ ventral septal area. The present study sought to determine whether cha nges in systemic blood pressure affect the electrical activity of sing le units within the bed nucleus of the stria terminalis. Extracellular voltage recordings from neurons in the bed nucleus were performed in urethane-anaesthetized rats catheterized for arterial blood pressure m easurements and for the intravenous administration of presser and depr essor drugs. Afferent or efferent connectivity of each recorded neuron was determined following electrical stimulation of nearby nuclei with and without known barosensitive regions. Of neurons demonstrating eff erent connectivity (antidromically evoked potentials) with the diagona l band of Broca/ventral septal area or habenular nuclei, 24 and 20%, r espectively, responded to changes in blood pressure with either increa ses or decreases in firing frequency. Paraventricular nucleus-projecti ng neurons were not affected by alterations in arterial blood pressure . Orthodromic potentials (inhibitory and/or excitatory) in the bed nuc leus were also observed following stimulation of these nearby nuclei. Of these orthodromically activated neurons, changes in arterial pressu re affected 31% of neurons receiving input from the diagonal band of B roca/ventral septal area, 33% of neurons with connectivity to the habe nular nuclei and 60% of neurons with connectivity to the paraventricul ar nucleus. These data show that the bed nucleus of the stria terminal is contains a sub-population of cells that are sensitive to deviations in resting arterial pressure and that these cells receive synaptic mo dulation from several limbic/forebrain sources. Furthermore, the resul ts are consistent with a role for the bed nucleus in the control of ca rdiovascular function and as a relay nucleus for modified baroreceptor input toward the diagonal band of Broca/ventral septal area.