Helium depression of cholinergic sensitivity in the cat superior cervical ganglion tissue

Abstract

The sensitivity of the superior cervical ganglion (SCG) tissue in the cat to activation by infusion of its normal cholinergic agonist acetylcholine (ACh +) has been compared for animal preparations breathing normal air and those breathing helium-oxygen ( 80% 20% ) at 1 atm. The ganglionic response to infusion of a 1.0 × 10 −3 m bolus of ACh + solution delivered intra-arterially to SCG tissue is approximately 15% less in HeO 2 breathing atmospheres than in N 2O 2. The response decay curves with increasing exposure time for the cat preparation in either breathing atmosphere are linear, and yield net decreases of 10–15% of control amplitudes over the course of 2 hr. The observed effect of 0.80 atm of He, relative to N 2, in partial desensitization of cholinergic response at the SCG, is discussed in terms of possible mechanisms of interaction of He with tissue receptor components.