Effects of a dry diet on the hypothalamic neurohypophyseal neurosecretory system in spiny mice as compared to the albino rat and mouse

Abstract

The present study reports on changes in the hypothalamic-neurohypophyseal neurosecretory system in four species of Murinae kept on a dry diet. Two xeric species were investigated— Acomys cahirinus and Acomys russatus, and two laboratory species— Mus musculus albino and Rattus norvegicus albino. The following parameters were investigated: changes in body weight; changes in volume of the pars nervosa; quantitative changes in the neurosecretory material in the pars nervosa—estimated photometrically after selective staining; cytological indications of activity in the supraoptic nucleus. Rattus norvegicus, the least resistant of all four species, lost 45% body weight during 14 days of water deprivation, and no rats survived beyond 17 days. Concomitant with loss in body weight there was progressive disappearance of neurosecretory material from the pars nervosa, verging on virtual depletion by day 14, and progressive hypertrophy of the pars nervosa. Hypertrophy of the supraoptic neurones indicated increased activity throughout the experiment. In both species of Acomys there was loss in body weight during the first fortnight, thereafter the rate of weight loss decreased in A. cahirinus, while A. russatus succeeded in stabilizing body weight below initial value. In Mus musculus there was steep weight loss during the first week, but recovery set in thereafter, and initial weight was regained by the end of the third week. In Mus musculus, Acomys cahirinus, and Acomys russatus—all three of whom are resistant to dehydration, although to different degrees—depletion of neurosecretory material from the neural lobe was followed by repletion, beginning about day 14 of dry diet. Concomitantly the initial hypertrophy of the neural lobe was suspended. In the supraoptic nucleus cytological evidence indicated heightened activity in all three species, most especially in Acomys russatus.