おう吐における吸気筋群活動の神経支配

Abstract

Vomiting is a nonrespiratory behavior during which the major respiratory muscles contract in a characteristic pattern which generates changes in the intrathoracic and intra abdominal pressures that lead to expulsion of gastric content. During vomiting, the major inspiratory muscles (the diaphragm and the external intercostal) co-contract with the expiratory abdominal muscles in a series of activity bursts.The question arises whether brain stem respiratory neurons are involved in the control of these muscles during vomiting. In the present study, we undertook to determine whether bulbospinal inspiratory neurons in the dorsal respiratory group (DRG) and in the para-ambiguus region of the ventral respiratory group (VRG), together with the upper cervical inspiratory propriospinal neurons, are important for activation of the diaphragm and external intercostal muscles during vomiting. To analyze the behavior of these neurons, we elicited “fictive vomiting” using either emetic agents or electrical stimulation of the supradiaphragmatic vagal nerve afferents in decerebrate paralyzed cats. This fictive vomiting was identified by a characteristic series of bursts from coactivation of the phrenic nerve and some other nerves innervating abdominal muscles, which would be expected to produce an expulsion of gastric contents in nonparalyzed animals.Only a few (<10%) bulbospinal DRG and VRG inspiratory neurons were found to have a response capable of initiating a discharge of the phrenic and external intercostal motoneurons during fictive vomiting. In contrast to the behavior of the bulbospinal inspiratory neurons, more than one-half of the upper cervical inspiratory propriospinal neurons were active in phase with the phrenic discharge during fictive vomiting. These results indicate that the DRG and VRG bulbospinal inspiratory neurons do not make a major contribution to the activation of the major inspiratory muscles, and that the upper cervical inspiratory neurons may be one candidate for the activation of these inspiratory muscles during fictive vomiting.