Brain and adrenal tyrosine hydroxylase activity after chronic footshock stress.

Rats subjected to 9 daily sessions of electric footshock stress showed marked increases in tyrosine hydroxylase activity in various brain regions and in the adrenal gland. The activity of the brain enzyme was elevated in the cerebral cortex, hypothalamus, locus coeruleus and the pons-medulla indicating a widespread effect of stress throughout the brain. Anatomical specificity of the response was indicated by a greater percent increase in the locus coeruleus, a nucleus containing noradrenergic cell bodies, than in the hypothalamus, cortex and pons-medulla, areas that contain noradrenergic terminals.