Growth and Obesity in Male Rats After Placement of Ventromedial Hypothalamic Lesions at Four Different Ages

Abstract

Ventromedial hypothalamic lesions in weanling female rats have been reported to result in a greater reduction of growth than placement of such lesions in older animals (Bernardis & Skelton, 1966). The present report deals with a parallel study in male rats of corresponding ages.Male Holtzman rats received bilateral electrolytic lesions at the age of 26 days (Group 1), 59 days (Group 3), 75 days (Group 5) and 140 days (Group 7). Nonlesioned rats of the same age served as controls (Groups 2, 4, 6 and 8). The methods used were identical with those in the study on female rats. Table 1 shows that, while the body weight of 26-day-old rats was unaffected when compared with controls of the same age, the rats lesioned at older ages (Groups 3, 5 and 7) weighed significantly more than their controls after 6 weeks. In contrast, linear growth (body length, tail length) was reduced most in Group 1, less in Groups 3 and 5, and was unaffected in Group 7. It was slightly less (10 %) in males than in females (15%, Bernardis & Skelton, 1966). It is possible that the greater effect of ventromedial lesions in weanling rats is attributable to a greater vulnerability of the smaller brains in these animals. In terms of Lee's (1929) index, all rats were equally obese when compared with their respective controls, although only the rats of Groups 5 and 7 showed significant hyperphagia. The obesity in the weanling rats is in accord¬ ance with carcass fat determinations made by Han, Lin, Chu, Mu & Liu (1965). Since it is known that growth hormone (GH) has a lipolytic effect (Knobil & Hotchkiss, 1964) it is conceivable that a deficiency of this hormone at an early age results in a greater accumulation of adipose tissue than in non-deficient rats. The reduction in the number of the pituitary acidophils which are known to elaborate GH was signifi¬ cant and similar in Groups 1, 3 and 5 but insignificant in Group 7 when compared with their respective controls. This reduction was less in the weanling male (36 %) than in the weanling female (48 %) animals. The greatest reduction in organ weight occurred in the rats of Group 1. It is noteworthy that the heart (Beznak, 1960) and kidney (Astarabadi, 1963) are sensitive to GH and that the adrenals are thought to

Origin of endocrine‐metabolic changes in the weanling rat ventromedial syndrome

“…Han et al (1965) and Bernardis and Skelton (1965) confirmed these findings and the latter authors observed, in addition, a decrease in the number of pituitary acidophils in spite of an intact median eminence. Similar findings were then reported for the male weanling rat (Bernardis and Skelton, 1967) and extended by the observation (Bernardis and Frohman, 1967;Frohman and Bernardis, 1968) that plasma and pituitary growth hormone (GH) levels were decreased as measured by radioimmunoassay in the weanling rat with VMN lesions. These changes were subsequently shown to correlate with the size of the lesion .…”

Effects of Monosodium Glutamate‐induced Obesity in Mice on Carbohydrate Metabolism in Insulin Secretion

“…The syndrome thus appears to have certain features in common with that resulting from bilateral destruction of the ventromedial nuclei in weanling rats (Han et al, 1965;Frohman & Bernardis, 1968;Bernardis & Skelton, 1965, 1967. Han et al (1965) and Bernardis & Skelton (1965, 1967 reported that extensive lesions in the ventromedial nuclei of weanling rats were associated with stunting and an increase in carcass fat without increased food intake. Excessive weight gain was not observed even when the rats were followed for several months.…”

Effects of monosodium glutamate administration in the neonatal period on the diabetic syndrome in KK mice

“…No estimate of energy expenditure was undertaken in the present study and further detailed examination of the pattern of food intake in treated animals and of energy expenditure appear indicated. Han et al [18] and Bernardis & Skelton [19,20] have shown that weanling rats with electrolytic lesions in the ventromedial hypothalamic nuclei became obese without excessive caloric intake. Frohman and Bemardis [6] concluded that at least one major factor contributing to excessive accumulation of adipose tissue in VMN lesioned weanling rats was growth hormone deficiency resulthag from the hypothalamic lesions.…”