Abstract
Liquor contacting peptidergic neurons (LCPNs) in the preoptic nucleus of the Japanese eel (Anguilla japonica), are investigated submacroscopically, light microscopically, electron microscopically (transmission and scanning) and histochemically.
LCPNs appear in 8-13per cent of all neurons constituting the preoptic nucleus and their cytoplasm contains many secretory granules stained by aldehyde-thionin or chrome hematoxylin. LCPNs have an epithelial cell-like polarity and their cytoplasmic organella shift to the supranuclear region. LCPNs are classified into three types (A, B, C) according to the liquor contacting portion of the cell:
Granular type A neuron (40-50×40-50μm2), the cell body of which is in contact with the cerebrospinal fluid (CSF), is the most common type and distributed in the ventral portion of the preoptic nucleus; this neuron is not connected with the neighboring ependymal cells by tight junctions. Bipolar type B neuron (60×30μm2), contacts the CSF with the tip of its cell process and is scattered throughout the preoptic nucleus; the cell is connected with the surrounding ependymal cells by tight junctions. Bipolar type C neuron (60×30μm2) possesses a cell process protruded into the third ventricle and is distributed in the dorsal portion of the preoptic nucleus; this also is connected with the adjacent ependymal cells by tight junctions.
Regardless of type, all LCPNs exhibit a positive acetylcholinesterase and a negative ATPase reaction. Numerous fluorescent varicosities of monoaminergic nerve terminals are closely associated with the cell bodies of the LCPN. LCPNs are likely regulated by monoaminergic fibers.
