Morphometric and immunohistochemical studies of the suprachiasmatic nucleus in the hereditary microphthalmic rat]

Morphometric and immunohistochemical analyses of the suprachiasmatic nucleus (SCN) were performed on hereditary microphthalmic rats. In normal rats, the number of cells and the volume of the SCN were 11, 631 and 6.7 x 10(-2) mm3 (an average taken from 12 SCNs). However, the neuronal population and volume of the SCN in hereditary microphthalmic rats were 7,450 and 4.5 x 10(-2) mm3 (an average taken from 14 SCNs), respectively. There were no significant differences in the size of neurons between normal and microphthalmic SCN neurons. Immunohistochemical studies showed that a considerable number of antivasopressin positive neurons were present in microphthalmic rats, despite their lack of the optic nerve. However, further detailed studies revealed that the number of antivasopressin positive neurons present in microphthalmic rats was only 68% of those found in normal rats. These findings suggest that the complete development of the SCN and vasopressin neurons depends on the visual input.