The effect of cooling on the responses of splenic capsular and vascular smooth muscle to nerve stimulation in the dog.

Field stimulation of strips of canine splenic capsule and splenic artery suspended in an organ bath causes in both a contraction that is enhanced by cooling from 37 degrees C to 27 degrees C. This finding contrasts with that from the isolated perfused canine spleen in which cooling to 27 degrees C enhanced the vascular response to splenic nerve stimulation but depressed the capsular response. The results of experiments to resolve the apparent discrepancy in the capsular smooth muscle response to stimulation indicate that the reduced response in the perfused spleen probably results from the capsular smooth muscle fibres being less optimally placed on their length: tension curve at 27 degrees C when spleen volume is less. There is thus no need to postulate any fundamental difference in properties between the smooth muscles from the two intrasplenic distributions.