Adrenal choline acetyltransferase activity: Sustained effects of chronic intermittent psychological and psychosocial stimulation

A brief period of fighting daily can cause the preganglionic splanchnic innervation of the adrenal medulla to undergo sustained, probably reversible, changes in the ability to synthesize acetylcholine. When mice that had been made aggressive by long-term individual caging were placed together and allowed to fight for 10 to 15 min daily for 10 consecutive days, choline acetyltransferase in the adrenal gland was increased. It increased to 8.4% and 37.1 % above undisturbed controls by 1 day and 3 days, respectively, after termination of fighting, and to a maximum of 45.4% above controls after 5 days; it had decreased to 20.3% above controls by 7 days after last fighting. A decrease in enzyme activity appears to precede this adaptive increase. Choline acetyltransferase activity was lowered 17.9% 18 to 20 hours after the last of 4 consecutive days of fighting. Merely transferring mice to an empty strange cage for 10 to 15 min and then returning them to their home cage, once daily for 5 days, decreased adrenal weight 20% and choline acetyltransferase 22% However, a single 1-hr session of acute stress (fighting or forcible restraint) did not alter adrenal choline acetyltransferase activity, a fact which suggests that splanchnic stimulation does not cause choline acetyltransferase to be released concomitant with acetylcholine.