Mv. Ugrumov et al., DEVELOPMENT OF THE SUPRACHIASMATIC NUCLEUS IN RATS DURING ONTOGENY - TYROSINE-HYDROXYLASE IMMUNOPOSITIVE CELL-BODIES AND FIBERS, Neuroscience, 58(1), 1994, pp. 151-160
This study has evaluated differentiation of tyrosine hydroxylase-immun
opositive neurons in the suprachiasmatic nucleus as well as the innerv
ation of this nucleus by tyrosine hydroxylase-immunopositive axons in
rats during ontogenesis. Tyrosine hydroxylase-containing structures we
re detected with electronmicroscopic pre-embedding immunocytochemistry
at the 22nd fetal day as well as at the second, ninth and 21st postna
tal days. Rare uni- and bipolar small tyrosine-hydroxylase-immunoposit
ive neurons were observed in the suprachiasmatic nucleus both in fetus
es and postnatal rats. These neurons underwent differentiation over th
e perinatal period that was mainly manifested in the increase of their
size as well as in the development of the Golgi complex, granular end
oplasmic reticulum and the onset of the dense core vesicle production.
Concomitantly, tyrosine hydroxylase-immunopositive neurons, cell bodi
es and dendrites, became innervated by immunonegative axons first maki
ng presynapses, and, then, symmetric (Gray-type II) and asymmetric (Gr
ay-type I) synapses. In addition to cell bodies and dendrites, tyrosin
e hydroxylase-immunopositive axons were regularly observed in ventral,
ventrolateral and ventromedial regions of the suprachiasmatic nucleus
in fetuses and postnatal rats. Tyrosine hydroxylase-immunopositive ax
ons were observed either in simple appositions with the immunonegative
neurons or making presynapses in fetuses and symmetric and asymmetric
synapses in postnatal animals. The nature of the tyrosine hydroxylase
-immunopositive axons and the functional significance in the suprachia
smatic nucleus in ontogenesis are discussed.