Abstract
Through permanently implanted cannulas, the ventromedial (VMH) or lateral (LH) hypothalamus of the white albino rat was chemically blocked or stimulated in an effort both to manipulate eating behaviour, and to mimic hyperphagia and aphagia after lesions of VMH and LH. — Observation A (Table 1) showed that sodium pentobarbital (SPB) (100γ), injected into the LH at the onset of a meal delayed the continuation of that meal. The adrenergic stimulant l-nor-epinephrine (NE) (0.2γ), injected in similar circumstances, did not enhance eating. Observation B (Table 2) showed that LH-injection of SPB (doses 50γ and 100γ) yielded no differences as to meal size and intake, but that the 100γ dose lowered the mean length of eating bouts and destroyed the normal decrease of successive eating bouts in the course of a meal (Fig. 2). Observation C (Table 3) showed that SPB 60γ and ne 0.2γ, when injected into the VMH of satiated rats, elicited eating while the cholinergic stimulant acetylcholine chloride (5γ) yielded no effects. Eating seemed to become conditioned to the observation procedure (Table 4), but this could not be replicated. The SPB-results mimic the hyperphagia and aphagia, seen after destructive VMH- and LH-lesions. — Two findings are discussed. 1. Eating as elicited by injection of SPB and NE (unexpected) into the VMH reflects two local-VMH mechanisms to activate the feeding system. 2. LH-anaesthesia by SPB interferes with local-LH positive feedbacks on the eating tendency, not with the eating tendency itself.