Development of serotoninergic (5HT) amacrine neurons in chick retina.

RIOS, H; BRUSCO, A; PECCI SAAVEDRA, J

INTERNATIONAL JOURNAL OF DEVELOPMENTAL NEUROSCIENCE

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 1997 vol. 15 p. 729 - 738

0736-5748

Numerous neurotransmitters have been studied in detail in the developing retina Almost all known neurotransmitters and neuromodulators were demonstrated in vertebrate retinas using formaldehyde induced fuorescence uptake autoradiography or immunohistochemistry procedures Serotoninergic "5HT" amacrine neurons were described in the inner nuclear layer "INL# of the retina with their dendrites spreading within the inner plexiform layer "IPL# The present work describes the morphological pattern of development of serotoninergic amacrine neurons with a strati_ed dendritic branching pattern in the chick retina from embryonic day 01 to postnatal day 6 Serotoninergic!bipolar neurons are also described 5HT!amacrine neurons have round or pear!shaped somata and primary dendritic trees oriented toward the IPL that runs through the INL showing several varicosities Secondary dendrites then go through the INL without any collateral branch At the outer and inner margin of the IPL the primary and secondary dendrites originate an outer and an inner serotoninergic network respectively When the primary dendritic tree reaches the IPL it detects laterally in sublayer 0*the outer serotoninergic network Tertiary branches then arise from the secondary dendrite and detect in the innermost sublayer of the IPL the inner serotoninergic network The postnal pattern of branching of 5HT amacrine cells was present at embryonic day 03 and was completely developed at hatching Serotoninergic "5HT? bipolar neurons were also present in the INL at hatching They are weakly immunoreactive and are probably a subset of bipolar cells that accumulate serotonin from the intersynaptic cleft and are not ´true´ 5HT neurons