COMPARISON OF THE EFFECTS OF GONADECTOMY ON SPONTANEOUS ACTIVITY OF WILD AND DOMESTICATED NORWAY RATS1

Abstract

Gonadectomy greatly reduced the spontaneous running activity of domesticated Norway rats, but had little effect on the activity of wild Norways. After gonadectomy, the seminal vesicles and uteri atrophied in both the wild and domesticated rats. The adrenals, which normally are heavier in wild rats, became even heavier after gonadectomy in wild males and less so in wild females, but decreased in domesticated females and showed a small increase in domesticated males. Sudan IV stained frozen sections showed that the adrenals of wild Norways, both control and gonadectomized, contained more lipid than those of domesticated rats. In explanation of the differences of the effects of gonadectomy in the 2 strains, it was suggested that running activity of wild rats is maintained largely by adrenal secretions whereas the activity of domesticated rats is maintained largely by gonadal secretions. Results indicate that during the process of domestication of the Norway rat, the gonads may have assumed control of functions that are predominantly controlled by the adrenal in the wild state.