Electrophysiological and Anatomical Studies of the Second Order Neurons in the Reflex Pathway from Pulmonary Rapidly Adapting Receptors in the Cat
Pulmonary rapidly adapting receptors (RARs)7, also known as lung irritant receptors, elicit various respiratory reflexes including increase of inspiratory activity and shortening of expiration, increase of respiratory frequency (tachypnea), augmented breaths (sighs), coughing, mucus secretion and bronchoconstriction2, 10, 11. Despite the large number of reports on the properties of RARs, there have been relatively few studies on the central pathways through which the respiratory reflexes evoked by the activation of these receptors are mediated. The projections and central terminations of afferent fibers originating from RARs have been traced to the nucleus of the solitary tract (NTS) with antidromic mapping4, spike-triggered averaging of field potentials8, and intraaxonal labeling with HRP. The presence of second order neurons was suggested in the medial and caudal portion of the NTS, especially in the commissural subnucleus (COM) caudal to the obex in both the cat8 and the rat1.
KeywordsCaudal Portion Dorsal Motor Nucleus Efferent Projection Order Neuron Phrenic Nerve Activity
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