Changes in Adrenal Enzymes synthesizing Catecholamines in Attack Behaviour evoked by Hypothalamic Stimulation in the Cat

Abstract

IN the cat, electrical stimulation^1,2 or selective lesions of the brain³ can evoke an affected display of anger, called sham rage³. This emotional display is often coupled with directed prey killing or attack behaviour². Associated with this is a widespread activation of the sympathetic nervous system and a release of the catecholamines, noradrenaline and adrenaline, from the adrenal gland^4,5. It was recently demonstrated that, when prolonged, increased neural release of adrenal catecholamines is associated with increased activity of tyrosine hydroxylase^6,7, the enzyme of the rate-limiting step in catecholamine biosynthesis⁸. The increase in enzyme activity is presumably the result of production of new enzyme^6,9. We have sought to determine whether the induction of attack behaviour in the cat by electrical stimulation of the hypothalamus, if sustained over several days, can lead to similar changes in adrenal tyrosine hydroxylase and also the adrenal enzyme phenylethenol amine-N-methyl transferase (PNMT) which converts norepinephrine to epinephrine.