REFLEX CARDIAC ACCELERATION AND LIBERATION OF SYMPATHOMIMETIC SUBSTANCES IN UNANESTHETIZED DOGS DURING ACETYLCHOLINE HYPOTENSION

Abstract

Dogs were prepared so that effect of acetylcholine could be detd. on blood pressure, rate of the innervated heart, rate of the denervated heart, and motility of the innervated and denervated intestine before and after adrenal demedullation. Intravenous acetylcholine in doses of 0. 03 to 0. 30 mg. per kg activated the mechanisms that compensate for lowered arterial blood pressure. Reflex cardiac acceleration, reflex liberation of adrenaline, and reflex liberation of sympathin occurred. Although the adrenergic nerves activated were mainly of the excitatory type, the sympathin produced inhibited the intestine. The compensatory mechanisms activated by the acetylcholine hypotension restored the blood pressure to the normal level in the unanesthetized animal within 30 to 180 secs.