Strain differences in attack patterns elicited by electrical stimulation in the hypothalamus of male CPBWEzob and CPBWI rats

There are striking differences in the attack patterns induced by electrical stimulation in the same site in the hypothalamus in different strains of rats. The attack on the back of an opponent is the prevailing form in random‐bred CPBWI albino Wistar rats. In the inbred CPBWEzob strain, hypothalamic stimulation does elicit predominantly head attacks and never back attacks. Attack patterns and wound patterns observed in both strains during maternal aggression, territorial conflicts, and hypothalamic stimulation suggest that hypothalamic attack is a behavioural category in its own right. We suggest that hypothalamic stimulation activates one single, multifunctional mechanism involved in the immediate organisation of attack patterns in the rat. During hypothalamic stimulation, this attack‐releasing mechanism is activated artificially. Even at threshold intensity, electrical stimulation seems to override the brain mechanisms which in natural settings often keep the hypothalamic attack‐releasing mechanism from expressing itself. Brain mechanisms coordinating adequate fighting should have considerable survival value. Strain differences suggest that the hypothalamic attack‐releasing mechanism is somehow “hardwired” in the brain and may be subject to selection.