Stress induces rapid changes in serotonergic activity: restraint and exertion

Rapid activation of central serotonergic systems occurs in response to the social stress of aggression in dominant lizards. The most rapid expression of serotonergic activity occurs in nucleus accumbens, hippocampus and brain stem. To compare previously measured responses induced by social stressors with those provoked by physical stress, serotonergic activity was examined following restraint stress (handling) and forced physical exertion. After h andling, some male Anolis carolinensis were placed on a race track and eith er run until there was no movement following 1 min of prodding, or half tha t time. Controls were killed without treatment. Lizards stressed by handlin g showed rapid (25 s) increases in serotonergic activity (5-HIAA/5-HT) in s triatum, dorsal cortex, locus ceruleus, and nucleus accumbens. Other change s in serotonergic systems caused by stress occurred in raphe and hippocampu s. serotonergic changes induced by handling stress were reversed by exercis e (to 50% maximal exertion time) in subiculum, striatum and nucleus accumbe ns. The serotonergic profile of lizards run until they would no longer resp ond to prodding (maximal exertion time) was significantly different from th at for more acute exertion in hippocampus, subiculum, striatum, medial amyg dala, locus ceruleus, area postrema, and raphe. Physical stress (handling) mimicked social stress by producing rapid serotonergic changes in hippocamp us, subiculum, nucleus accumbens and locus ceruleus. In contrast, the media l amygdala, which has previously been demonstrated to respond serotonergica lly to social stress only after a temporal delay, did not show a rapid resp onse to restraint stress. (C) 2000 Elsevier Science B.V. All rights reserve d.