THE SENSITIZATION OF THE DENERVATED HEART TO ADRENALINE

Abstract

The heart-rate response of 5 cats to graded doses of adrenaline (0.05-10.0 7) was observed 1 day after denervation and every 7 days thereafter for 29 days. Sensitization could not be reliably demonstrated with small (0.05 7) and large (3.33 to 10.0 7) doses of adrenaline. The larger doses frequently induced arrhythmias by the 15th day. Definite sensitization always developed within 8 days after denervation. A slight and progressive increase in sensitization usually occurred, the small doses of adrenaline, from the 8th to the 29th day following denervation, and there was no indication that sensitization was complete at 29 days. After the 15th day of denervation it was necessary to use doses of less than 1 [gamma] to detect further development of sensitization; doses near the minimal effective dose revealed it more clearly. The response of the denervated heart to adrenaline was prolonged as denervation developed. The latency of the adrenaline effect on the 8th and subsequent days was increased over that on the 1st day. The response of the denervated heart to adrenaline should not be used as an indicator in chronic expts. without first recognizing the existence of sensitization due to the denervation.