Recovery of rats with dorsomedial hypothalamic nucleus lesions (DMNL rats) from body weight restriction: Effect of duration of postoperative prerestriction period

Abstract

The present study was performed to see whether somatic and underlying metabolic-adaptive responses of DMNL rats and sham-operated controls (CON) to body weight restriction and subsequent refeeding could be influenced by the duration of ad lib feeding between lesion production and start of restriction. In contrast to previous studies (42 and 55 days, respectively) this time was reduced to 25 days. Restriction was similar, i.e., 27 days. DMNL rats show the same adaptive capacity in most parameters as do restricted CON. However, this response was at a lower level of absolute body weight, appropriate, so it appears, for their DMNL-induced lower body weight. In some parameters different responses were noted, however, suggesting that the time of ad lib feeding following the DMNL does indeed affect adaptive responses. Notably, this is the case in both DMNL and CON commensurately. Linear growth was reduced by restriction in the present but not in the two previous studies. Food intake showed a pronounced “overshoot” on refeeding but did not previously. Efficiency of food utilization was normal in the present study but depressed previously. A rise in plasma free fatty acids was not evident but was so in previous experiments. We concluded that, although DMNL rats respond to food restriction and recovery like similarly-treated CON, the duration of the ad lib feeding before restriction and/or the absolute age of the animals at that time, do indeed affect some parameters. This may be related to the fact that different aspects of the DMNL syndrome declare themselves in a sequential rather than a simultaneous manner.