Lateral hypothalamic self-stimulation: Effect of excess body weight

Abstract

Self-stimulation in the lateral hypothalamus was measured in rats made obese by force-feeding a liquid diet. Mean self-stimulation rate at the obese weight was significantly less than the mean self-stimulation rate at normal weight levels. This result is consistent with the view that a factor correlated with obesity inhibits feeding by inhibiting lateral hypothalamic reward.Obesity inhibits feeding. Rats that have been forced to become obese, by force-feeding, insulin treatments, or lateral hypothalamic stimulation, will subsequently reduce their body weight by restricting their food intake (Cohn & Joseph, 1962;Hoebel & Teitelbaum, 1966; Steinbaum & Miller, 1965). Normal body weight is thereby regulated through changes in food intake.It is now known that an animal's state of hunger or satiety determines, in part, electrical self-stimulation in the lateral hypothalamus (LH). For instance, self-stimulation rate increases when an animal is deprived for 24 h (Margules & Olds, 1961), but decreases after intragastric or intravenous feeding, or when the stomach is distended with an intragastric balloon (Hoebel, 1968). Changes in self-stimulation rate also parallel changes in food intake when blood glucose is altered with injections of insulin or glucagon (Balagura & Hoebel, 1967). It was therefore predicted that self-stimulation in the LH would, like food intake, be depressed when an animal was overweight. To test this hypothesis, self-stimulation rate was measured daily in rats force-fed a liquid diet to increase their body weights above the normal level. METHOD SubjectsFive female albino rats, weighing between 250 and 320 g, were housed in individual cages and given free access to food (purina Laboratory Meal) and water. Ss were kept in a temperature-controlled room, where the lights were automatically programmed for a 12-h light-dark cycle. Each S was implanted with a prefabricated electrode assembly, as described by Hoebel (1964) . With this technique, 90% platinum-l0% iridium electrodes were chronically placed in the lateral hypothalamus of both sides of the brain. The coordinates with the top of the cortex level were: A, 6.0 mm; L, 2.0 mm; and D, 7.5 mm. A stainless steel wire was wrapped around the cranial screws and was left to protrude through the dental cement to serve as an indifferent electrode. ApparatusA Tektronix 161 pulse generator produced the electrical stimulation. The pulses were negative, 0.1 msec in duration, and occurred at a repetition rate of 100 pps. Stimulation was *This study is part of a PhD thesis submitted to the Department of Psycho!oiY. Princeton University. and was supported by PHS Grant MH08493 and NSF Grant GB8431 to Bartley G. Hoebel. 51 delivered to the rats through a constant current device and was continuously monitored with an oscilloscope.The experimental chamber (7 x 12 in.) consisted of four clear plastic walls, a response lever (Lehigh Valley No. 121-05), and a grid floor. An overhead mercury commutator prevented the stimulation leads to the rat from becoming entangled. A p...

Changes in self-stimulation at stimulation-bound eating and drinking sites in the lateral hypothalamus during food or water deprivation, glucoprivation, and intracellular or extracellular dehydration.

“…Olds, 1977; Rolls, 1975). These models are consistent with the following observations: (a) Many procedures that decrease food intake also decrease the rate of self-stimulation at lateral hypothalamic sites (Balagura, 1968; Balagura & Hoebel, 1967; Hoebel, 1968; Hoebel & Teitelbaum, 1962; Hoebel & Thompson, 1969; Huston, 1971; Kornblith & Hoebel, 1976; MacNeil, 1974; Mount & Hoebel, 1967). (b) Both species-typical eating and/or drinking (Cox & Valenstein, 1969; Roberts, 1980) and reinforcement effects (Goldstein, Hill, & Templer, 1970; Mogenson, 1969; J.…”

Food- and ICS-reinforced operant behavior following VMH lesions in conscious rats

“…Hoebel and Teitlebaum (1962) and Margules and Olds (1962) reported that electrodes placed in the LH that induced stimulus-bound feeding also supported high rates of responding for intracranial selfstimulation (ICS). Hypothalamic sites that regulate feeding thus seem to exert a corresponding control & Hoebel, 1967;Wilkinson & Peele, 1962), whereas decreases follow gastric distension (Hoebel, 1968;Hoebel & Thompson, 1969;MacNeil, 1974). Hoebel (1968) found these decreases in self-stimulation rates regardless of whether the distension was produced by intragastric feeding or by the inflation of a gastric balloon.…”