Immunocytochemical study of the postnatal development of 5-HT-containing neurons and fibers in the cerebroid ganglia of Cryptomphalus aspersa.
In this work we have studied the organization of the serotonergic system in new-hatched snails and the developmental changes that occur postnatally. The serotonergic system of the new-hatched snail is not completely developed. Tracts previously described in the adult were already present at hatching; however immunoreactivity of these tracts was somewhat less intense than that in adults, but, their location was practically the same. At hatch the pro- and postcerebral serotonergic plexi were poorly developed, while the mesocerebral one was nearly absent. The procerebral plexus occupied only the caudal half of the procerebral neuropile. Growth cone profiles were found in all plexi. The paired giant dorsal serotonergic neurons were the only stained neurons constantly found at hatching; they were symmetrically located. The paired medium-sized neurons were not found in all brains examined. Sometimes only one of them was present at hatching; it was located either in the right or in the left ganglion. The small neurons were absent in most cases. They gradually appeared during the first three postnatal months. Following hatching the procerebral plexus had undergone an intense growth. By the third postnatal month it innervated completely the procerebral neuropile. At hatching the area innervated by the procerebral plexus was 4500 micron 2, by the third month this area was about 58,000 micron 2 and in the adult was 80,000 micron 2. The postnatal development of the procerebral serotonergic plexus proceeds through two different modalities of neuritic growth: expansive growth is mediated by centrifugal elongation of terminal branches while the increase in fiber density within the plexus results from lateral sprouting.(ABSTRACT TRUNCATED AT 250 WORDS)
Flores
V
V
Instituto de Biologia Celular, Facultad de Medicina, Universidad de Buenos Aires, Argentina.
Brusco
A
A
Saavedra
J P
JP
D000818:Animals; D007150:Immunohistochemistry; D009420:Nervous System / Q000254:growth & development / Q000378:metabolism*; D012701:Serotonin / Q000378:metabolism* / Q000502:physiology; D012908:Snails / Q000254:growth & development* / Q000378:metabolism
D012701:Serotonin