Acetylcholinesterase activity at the synapses of presynaptic boutons with presumedα-motoneurons in chicken ventral horn

Abstract

Acetylcholinesterase (AChE) activity at the synapses of presynaptic boutons on presumed alpha-motoneurons in the chicken ventral horn was studied histochemically at the light- and electron-microscope levels. At the light-microscope level, many dot-like AChE-active sites were observed on the soma and dendrites of presumed alpha-motoneurons. On electron microscopy, reaction products for AChE activity were observed mainly in the synaptic clefts of the four kinds of presynaptic boutons: (1) S type boutons, (2) boutons containing small, spherical, dense cored vesicles (diameter range, 60-105 nm) and spherical, clear vesicles, (3) boutons containing medium-sized, spherical, dense cored vesicles (65-115 nm) and spherical, clear vesicles, and (4) boutons containing large, spherical, dense cored vesicles (80-130 nm) and spherical, clear vesicles. In the light of previous physiological and biochemical studies, the present results suggest the possibility that each of these presynaptic boutons which are AChE-active in their synaptic clefts may contain acetylcholine, substance P, or enkephalins which acts as a neurotransmitter or modulator.

C-terminals on motoneurons: Electron microscope localization of cholinergic markers in adult rats and antibody-induced depletion in neonates

“…40 We found by light microscopy double immunolabelling methods that subsurface cisterns co-localize with choline acetyltransferase (ChAT)-labelled boutons on motoneurons at most cranial and spinal levels, 24 which is consistent with electron microscopic observations that C-terminals on motoneurons in the hypoglossal nucleus are cholinergic, based on their immunolabelling for ChAT. 8 In agreement with electron microscopy histochemical results showing high concentrations of acetylcholinesterase (AChE) reaction product at motoneuronal C-terminal subsurface cistern complexes, 10,34 a high degree of co-localization was found between immunofluorescence labelling for subsurface cisterns and AChE. 24 These results, together with our observations that large ChAT-containing boutons on motoneurons correspond to those containing AChE, suggested that most, if not all, C-terminals are cholinergic.…”

Evidence for the cholinergic nature of C‐terminals associated with subsurface cisterns in α‐Motoneurons of rat

“…In histochemical investigations of AChE, enzyme reaction product, although widely distributed, was found predominantly at synaptic clefts formed by C-terminals on motoneurons in hypoglossal, facial, and cervical motor nuclei of rat (Davidoff and Irintchev, 1986). In a study of AChE in chicken ventral horn, enzyme reaction product was also localized to some C-terminals, as well as several other terminal types on motoneurons (Sakamoto et al, 1985).…”

“…Our results are consistent with these earlier descriptions and demonstrate somewhat more clearly the presence of ChAT-positive "terminals" on motoneuronal cell bodies, as well as their proximal dendritic segments. Similarly, although AChE has been investigated by histochemical methods in the spinal cord of several species (Butcher et al, 1977;Odutola, 1972;Satoh et al, 1983;Silver and Wolstencroft, 19711, reaction product of this enzyme is not readily visualized by LM in nerve endings associated with motoneurons, but as discussed below has been localized to discrete types of terminals on these neurons by EM (Lewis and Shute, 1966;Davidoff and Irintchev, 1986;Sakamoto et al, 1985). AChE in the CNS has also been examined by immunohistochemical techniques (Andra et al, 1988;Bean et al, 1991;Rakonczay and Brimijoin, 1986), but to our knowledge detailed analyses of AChE-IR elements in spinal cord have not been reported.…”

Swimming against the tide: investigations of the C-bouton synapse

“…Correlative light-electron microscopic analysis of ChAT-IR confirmed C-boutons are cholinergic (Houser et al, 1983; Connaughton et al, 1986; Li et al, 1995), a suggestion first made decades prior with ultrastructural acetylcholinesterase (AChE) histochemistry (Lewis and Shute, 1966), which alone is not sufficient for cholinergic classification (Fibiger, 1982; Satoh et al, 1983; Sakamoto et al, 1985; Davidoff and Irintchev, 1986; Nagy et al, 1993). In support, VAChT is highly associated with small clear synaptic vesicles in the C-bouton presynaptic terminal (Gilmor et al, 1996) and there is a strong association throughout the brainstem and spinal cord between large ChAT-IR synaptic boutons on α-MNs and SSCs immunolabeled for connexin32 (Nagy et al, 1993).…”