Substance P effects on the dorsal motor nucleus of the vagus

Substance P (SP) was applied by superfusion (0.8 to 3.4 x 10(-6) M) to neurons of the dorsal motor nucleus of the vagus (DMV) in slice preparations of the rat medulla oblongata. Intracellular recordings showed that 18 of 43 (42%) neurons were depolarized and the depolarization was associated with an increase in membrane input resistance; five of 43 (12%) neurons were hyperpolarized and the hyperpolarization was associated with a decrease in membrane input resistance. Both effects were reversible and persisted after blockade of synaptic transmission by Ca2+ free/high Mg2+ solution. These data show that: 1) vagal neurons in the DMV have receptors for SP; 2) SP may modulate vagal output specially by increasing neuronal excitability; 3) although electrophysiological effects of SP have been studied in a variety of central and peripheral neurons, this is the first evidence of SP effects on DMV; 4) DMV is a particular brain target site in which SP may induce depo- or hyperpolarization.