Laryngeal water receptors initiating apnea in the lamb

Abstract

Water stimulation of receptors in the larynx of the lamb can produce apnea lasting as long as the water remains. The effect is mediated through the superior laryngeal nerve. The discharge of 50 units recorded from the superior laryngeal nerve of 12 lambs was altered by water stimulation of the larynx. Thirty-two units discharged to nonflowing water (water units). The discharge of another seven units was enhanced by flow (water + flow units). Seven units were excited by flowing water as well as other test solutions or gases (flow units). Four units resembling lingual gustatory units were suppressed by water (“taste” units). Mechanoreceptors not affected by water were ignored. Mechanical stimulation, however, excited some, but not all, water sensitive units. Two-thirds of the water sensitive units were slowly or nonadapting: their receptors appear to initiate the sustained apnea on water stimulation of the larynx of the lamb. Since the discharge characteristics of these receptors are dissimilar to taste units they are unlikely to be taste buds.