Transient features of tachykinin peptide innervation of the dorsal lateral geniculate nucleus of the rabbit during postnatal development.
The tachykinin peptide innervation of the developing dorsal lateral geniculate nucleus of the rabbit was studied with immunocytochemical techniques at the light and electron microscopic levels by using an antibody directed to the C-terminal of the mammalian tachykinin peptides. At birth, the rabbit's lateral geniculate nucleus was densely innervated by a large number of labeled fibers. These relatively unbranched axons were dispersed throughout the nucleus but showed a higher density of fiber packing in the external layer of the alpha sector. Over the next three weeks this pattern of distribution changed dramatically. Immunoreactive fibers were gradually eliminated from most of the nucleus, and, by the end of the third postnatal week, they appeared as a narrow plexus deep to the optic tract. At the same time, these axons showed major morphological alterations as they gradually became thicker and developed terminal arborizations characterized by spherical or elongated enlargements. Overall, by the end of the third postnatal week, the pattern of distribution and appearance of tachykinin-labelled fibers in the dorsal lateral geniculate nucleus were similar to those described in the adult rabbit (Brecha et al., 1987). Ultrastructural analysis has shown that during the first week, tachykinin-immunoreactive profiles appeared as round or elongated varicosities making asymmetrical synapses with dendritic shafts throughout the lateral geniculate nucleus. Thereafter, as they were progressively restricted to the external layer of the alpha sector of the nucleus, they began to form multiple synaptic contacts with neuronal processes in complex glomerular neuropil. On the basis of the present and previous findings, we suggest that tachykinin peptides not only play a role as putative neurotransmitters in the retinogeniculate pathway, but they may also play a role in the development of the lateral geniculate nucleus and of the retinogeniculate projection system in the rabbit.
Parnavelas
J G
JG
Department of Anatomy and Developmental Biology, University College London, United Kingdom. j.parnavelas@ucl.ac.uk
Dinopoulos
A
A
Brecha
N C
NC
D000818:Animals; D000831:Animals, Newborn / Q000254:growth & development*; D005830:Geniculate Ganglion / Q000378:metabolism / Q000648:ultrastructure*; D007150:Immunohistochemistry; D008854:Microscopy, Electron; D011817:Rabbits; D015320:Tachykinins / Q000378:metabolism*
D015320:Tachykinins