The innervation of tracheal smooth muscle in the ferret.
The innervation of tracheal smooth muscle in the ferret has been studied by monitoring pressure changes in a fluid-filled segment of trachea in pentobarbitone anaesthetized animals. Stimulation of the peripheral cut end of the vago-sympathetic trunk elicited increases in trachea segment pressure only when activity was evoked in non-myelinated efferent axons, myelinated axons were without effect. Such excitatory responses were blocked by atropine. After atropine and elevation of trachealis muscle tone with 5-hydroxytryptamine, stimulation of the vago-sympathetic trunk produced a fall in tracheal segment pressure. These inhibitory responses were completely blocked by bretylium tosylate in six animals and markedly reduced in a seventh. It is concluded that contraction of tracheal smooth muscle in the ferret is cholinergically mediated and solely dependent on activity in non-myelinated vagal efferent axons and that inhibition is mediated by noradrenaline released from sympathetic nerve endings. A non-adrenergic inhibitory system would not appear to be present in the ferret.
McWilliam
P N
PN
Department of Cardiovascular Studies, University of Leeds, UK.
Gray
S J
SJ
D000818:Animals; D001369:Axons / Q000502:physiology; D004558:Electric Stimulation; D005260:Female; D005289:Ferrets / Q000033:anatomy & histology*; D008297:Male; D009130:Muscle, Smooth / Q000294:innervation*; D009431:Neural Conduction; D009476:Neurons, Efferent / Q000502:physiology; D013268:Stimulation, Chemical; D013564:Sympathetic Nervous System / Q000502:physiology; D014132:Trachea / Q000294:innervation*; D014630:Vagus Nerve / Q000502:physiology / Q000648:ultrastructure