Morphological changes of somatostatin neurons in the suprachiasmatic nucleus by hypophysectomy of the rat.
After hypophysectomy, behavioral circadian rhythmicities in the rat became indistinct and phase shift was observed. Therefore, it was thought that the suprachiasmatic nucleus (SCN), which is the circadian oscillator in mammals, was affected by hypophysectomy. We investigated the effects of hypophysectomy on SCN neurons using immunohistochemical staining. Wistar-Imamichi strain male rats were hypophysectomized at 60 days old. Their brains were fixed by acrolein perfusion at 10, 30 and 60 days after the operation, and then vasopressin (AVP)-, vasoactive intestinal polypeptide (VIP)- and somatostatin (SRIH)- neurons in the SCN were stained immunohistochemically. Ten days after the operation, SRIH-neurons were not found in the SCN. At 30 and 60 days after the operation, a few SRIH-positive cell bodies were recognized. In contrast, AVP- and VIP- neurons did not change in morphology in comparison with normal rats. These results suggest that hypophysectomy produces an essential change in SRIH neurons in the SCN, and that such change is responsible for the abnormal behavioral rhythms.
Shinoda
M
M
Institute of Experimental Animal Research, Gunma University School of Medicine, Japan.
Ishikawa
K
K
Miura
T
T
D000818:Animals; D001522:Behavior, Animal; D002940:Circadian Rhythm; D007016:Hypophysectomy; D007150:Immunohistochemistry; D008297:Male; D009474:Neurons / Q000166:cytology / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D013004:Somatostatin / Q000378:metabolism*; D013493:Suprachiasmatic Nucleus / Q000166:cytology / Q000378:metabolism*
D013004:Somatostatin