Salivary secretion elicited by activation of the parabrachial nuclei in the cat

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The lateral pontine tegmentum contains the parabrachial nuclei (NPB) which have been identified as a relay nucleus for cardiovascular, respiratory and gustatory systems, but their role in the regulation of these systems is not well understood. We examined the effects of electrical and chemical stimulation of the NPB on blood pressure, phrenic and hypoglossal nerve activity and salivary secretion. These variables were measured in eight anesthetized (α-chloralose/urethane, 30/150 mg/kg, n = 5) or decerebrate ( n = 3) cats before, during, and after trains of electrical stimulation (1 ms pulse duration, 10 Hz 5 min train duration, currents as low as 10 μA) delivered unilaterally to NPB. Stimulation of the NPB elicited copious salivary secretion (1100 ± 270 mg, mean ± S.D.; P < 0.001). Secretion was blocked completely by prior administration of atropine. The effects of the stimulus train on the respiratory and cardiovascular systems were variable and inconsistent even though short-latency responses of phrenic and hypoglossal nerve activities to single pulses were consistent. The short-latency response of phrenic nerve activity was biphasic, a decrease followed by an increase in activity; the response of hypoglossal nerve activity was monophasic, a transient increase in activity. Effects of electrical stimulation were replicated by the injection of an excitatory amino acid agonist (kainic acid) into the dorsolateral pons. Injection of 50 nl of 10 mM kainic acid into the NPB evoked salivary secretion, indicating that this response was elicited by stimulation of cell bodies in the region. In addition, chemical excitation increased breathing frequency, peak phrenic nerve activity, and blood pressure. Electrical and chemical stimulation sites were confirmed by histologic analysis and were located in the Kölliker-Fuse subnucleus of the NPB. These results suggest that the NPB can influence salivary secretion through a cholinergic pathway, with or without changes in blood pressure or breathing pattern.