The lateral hypothalamic syndrome in the weanling rat: bone geometry and biomechanics

Male weanling Sprague-Dawley rats received bilateral electrolytic lesions in the lateral hypothalamic area (LHAL). One group of sham-operated controls was fed ad lib (CON-ADLIB), another was pair fed to the LHAL group (CON-PF). The experiment was terminated 1 month after surgery. At that time, LHAL rats were 49% and CON-PF rats were 41% lighter than CON-ADLIB. Carcass protein in LHAL rats was significantly reduced in LHAL: versus CON-ADLIB. Linear growth was significantly reduced by 18% in LHAL versus CON-ADLIB, as well as LHAL: versus CON-PF by 6%. Mean caloric intake was significantly reduced by 48% in LHAL versus CON-ADLIB, as was caloric efficiency (body weight gained per calories eaten) by 36%, as well as, in CON-PF versus CON-ADLIB by 20%. LHAL rats showed a significantly shorter (10%), narrower (15%) and thinner (25 %) cortex at midshaft of the femur. Resistance to torsional loads was reduced by 25% in both LHAL and CON-PF, but this did not reach statistical significance, in comparison to CON-ADLIB. There was no statistical significance among the groups in stiffness and maximal angular displacement. We conclude that the reduced bone geometrical and biomechanical properties in both LHAL rats and CON-PF versus CON-ADLIB are similar because both former groups of rats were greatly subcaloric. Thus, the changes here observed are not due to a specific neuroendocrine/autonomic lesion effect but may be attributable to the reduced food intake, i.e., nutritional factors.