CHANGES IN THE SENSITIVITY OF THE SWEAT GLANDS OF THE CAT AFTER DENERVATION

¹ Department of Pharmacology, Harvard Medical School, Boston, Massachusetts

The sensitivity of the sweat glands of the hindpaws was determined in cats under chioralose anesthesia by determining threshold rates of intraaortic infusion for acetylcholine and for pilocarpine. After denervation, changes in sensitivity occurred in two phases. During the first 2 postoperative days, subsensitivity was noted when a) the glands still responded to electrical stimulation of the peripheral nerve stump, b) the acetyicholine content of the hairless footpads declined to about 50% of normal and c) choline acetylase activity was nearly normal. From the 4th postoperative day onward, pronounced supersensitivity was observed when a) peripheral transmission had failed, b) the acetyicholine content fell below 20% of normal and c) choline acetylase activity was clearly reduced. Since denervation supersensitivity was equally pronounced for acetylcholine and pilocarpine, it appears unlikely that a decline in cholinesterase activity was responsible for the supersensitivity. Daily pretreatment with pilocarpine prevented the development of denervation supersensitivity. On the other hand, daily pretreatment of unoperated cats with chlorisondamine for 4 days caused supersensitivity. It is concluded that an increased activity of the sweat glands reduces sensitivity, while inactivity (present after full degeneration of the nerve terminals or after the administration of chlorisondamine) increases the sensitivity of the glands. The cholinergically innervated sweat glands do not appear to develop a type of supersensitivity that is comparable to the "presynaptic" type of supersensitivity observed in adrenergically innervated organs.