Effects of cooling on the levels of acetylcholine, cholinesterase, choline acetyltransferase and the intramural electrical stimulation on the guinea pig ileum.

The effects of hypothermia (4 degrees C) on the components of the cholinergic system of the ileal longitudinal muscle and the adherent Auerbach's plexus of the guinea pig ileum have been investigated. Acetylcholine (ACh) content of the muscle was determined by pyrolysis-gas chromatography. It decreased from 119 to a fairly steady level of 16 nmol/g of wet tissue during the first 72 h of cold storage at 4 degrees C under anoxic conditions. Concomitantly, responsiveness to intramural electrical stimulation decreased by 72%. Cholinesterase (ChE) and choline acetyltransferase (ChA) activities each dropped by 40% during this period. However, the de novo synthesis of ACh over the period of study did not change significantly. The response of the preparation to the exogenously applied ACh remained fairly constant suggesting that the changes in the cholinergic receptor are not accountable for the decrease in responsiveness to intramural stimulation. From the results of this study, it has been concluded that cold storage for 5 days leads to: (1) a significant decline in ACh content within 72 h of storage; (2) a decrease in ChE and ChA activities; (3) no significant effect on the cholinergic receptor; and (4) a decrease in responsiveness to intramural electrical stimulation which is probably due to a malfunction of the ACh-releasing mechanism.