Food hypermotivation syndromes in rabbits with hyperactivity of lateral hypothalamic structures

Abstract

A focus of hyperactivity in the initiating centers for food motivation was created in experiments on unrestrained rabbits by blocking inhibitory mechanisms in the lateral hypothalamus (LH) by injection of tetanus toxin (group 1) or by chronic electrical stimulation of the same region of the brain (group 2). The syndromes thus evoked differed in the intensity of food hypermotivation. The syndrome evoked by injection of tetanus toxin was characterized by very rapid development, clear symptoms of hyperphagia, and a severe course. Marked epileptiform activity was recorded in LH, evidence of the formation of a generator of pathologically enhanced excitation in the “pacemaker” of food motivation. Mechanisms of adequate correction of behavior depending on the result obtained were completely disturbed in the animals. The syndrome evoked by chronic electrical stimulation of LH was characterized by slower formation and a more favorable course. Relatively weak epileptiform activity was recorded in LH. Enhanced food-getting activity of the rabbits also was observed in the late periods after the beginning of electrical stimulation, but the animals' behavior did not lose its adaptive character in this case. The formation of the two syndromes of food hypermotivation described above was connected with the formation of two excitation generators, differing in the intensity of excitation produced by them.