HYPER-REACTIVITY AS WELL AS MOUSE KILLING IS INDUCED BY ELECTRICAL-STIMULATION OF THE LATERAL HYPOTHALAMUS IN THE RAT

Attack or muricide in rats was elicited from 24 of 58 stimulation sites at intensities of 10 to 30 μA (60 Hz, sine wave). Most of the effective stimulation sites were adjacent to the fornix or in the lateral hypothalamus at the level of the anterior half of the ventromedial nucleus. The stimulation also induced attack on a rat and occasionally on an anesthetized mouse or a block of wood but did not induce eating of lab chow or drinking of water. Hyperreactivity was also induced with stimulation intensities of 10 to 30 μA (60 Hz, sine wave). The sites yielding the greatest increases in reactivity were in the same region as those which induced muricide although a number of sites in the posterolateral hypothalamus also induced increases in reactivity. However, the same electrodes did not consistently elicit both mouse killing and hyperreactivity. The hyperreactivity was not associated with increased locomotor activity, afterdischarge caused by the electrical stimulation or aversive stimulation sites. These results suggest that excitatory systems exist in the lateral hypothalamus for both attack and reactivity. It is suggested that the attack is a broad-spectrum attack while the hyperreactivity is a component of defensive behavior. © 1979 Academic Press, Inc.