The effects of medial hypothalamic stimulation on escape from footshock

In three experiments, electrodes were chronically implanted into the medial hypothalamic area of male rats. Escape latencies, motivated by electrical stimulation of the brain and footshock presented both separately and together in a shuttle box, were measured. In all cases where cessation of medial hypothalamic stimulation was contingent upon escape, the combination of footshock and intracranial stimulation decreased escape latencies to a level below that motivated by footshock alone. Increases in the current stimulating the medial hypothalamus generally caused more rapid escape, both when the intracranial stimulation was presented alone and when combined with footshock. In contrast, stimulation of sites within the medial forebrain bundle region, which supported self-stimulation, systematically increased latencies to escape from footshock. Facilitation of escape behavior was no longer observed when the presentation of medial hypothalamic stimulation was nonresponse contingent. These effects are interpreted as consistent with a predominantly aversive character attributable to electrical stimulation of the medial hypothalamus, but not with the view that this part of the brain mediates general behavioral suppression.