The increases in rat cortical and midbrain tryptophan hydroxylase activity in response to acute or repeated sound stress are blocked by bilateral lesions to the central nucleus of the amygdala

Abstract Sound stress (SS) (120-dB pulses of 100 ms duration, every min for 1 h) produces an elevation of in vitro cortical or midbrain tryptophan hydroxylase activity from male Sprague-Dawley rats that is abolished, in vitro, by incubation of the enzyme preparation with alkaline phosphatase. SS, when repeated on 3 different occasions, the first 2 sessions 24 h apart and the 2nd and 3rd session separated by 48 h, produces a stable increase in the in vitro enzyme activity that is unaffected by alkaline phosphatase. Bilateral lesions to the central nucleus of the amygdala block both increases in enzyme activity obtained in response to acute and repeated SS, but leave enzyme activity from sham-stressed rats unaffected.