Acetylcholinesterase activity of synaptic structures in the spinal trigeminal nucleus

Abstract

The electron microscope has been used to study the localization of acetylcholinesterase (AChE) activity in the spinal trigeminal nucleus of normal cats with special emphasis on the distribution near synaptic structures. Reaction product is found around both round and flattened synaptic vesicle-containing axon terminals, particularly in synaptic clefts and often specifically associated with the presynaptic, or less frequently the postsynaptic membrane. The presence of reaction product at these specific sites suggests that these are areas of high AChE activity and that acetylcholine may be important in neurotransmission in these regions.

Ultrastructural changes in acetylcholinesterase activity in the deafferented spinal trigeminal nucleus

“…The medium consisted of 2 mM substrate (acetylthiocholine iodide, AThCh; National Biochemical Corporation), 5 mM sodium citrate, 0.3 mM cupric sulfate, and 0.5 mM potassium ferricyanide in 50 mM sodium hydrogen maleate buffer, pH 6.0 (Karnovsky and Roots, 1964). The inhibitors tetraisopropylpyrophosphoramide (iso-OMPA) and eserine (physostigmine) were used in control preparations i n addition to incubation in medium without substrate (Westrum and Broderson, 1976).…”

“…Tissue was osmicated in the same buffer for %-1 h and prepared for electron microscopy by the usual methods (Westrum and Black, 1971). For additional details, see Broderson et al (1974) and Westrum and Broderson (1976). Semithin (1 pm) sections were made for orientation purposes; then the blocks trimmed for the specific nuclei and sublayers.…”

“…In both the normal and control spinal trigeminal nucleus, AChE reaction product is consistently found in the extracellular space with a predilection for synaptic clefts of both major classes of terminals (Westrum and Broderson, 1976). The distribution of reaction product within synaptic clefts is variable.…”

“…Acetylcholinesterase (AChE), the glycoprotein enzyme that hydrolyses the neurotransmitter acetylcholine (ACh), has important functional implications in the nervous system and is particularly well known for its role in the termination of cholinergic transmission. The concentration and distribution of AChE in normal and injured nerves have been studied more or less along the entire neuronal axis, including peripheral endings, both sensory endings and motor end-plates (Gautron et al, 1983; McConnell and Simpson, 1976), pre-and postganglionic fibers (Malatova et al, 1985), cell bodies (Malatova et al, 1985; Pannese et al, 1974), and in terminal synaptic regions (Broderson et al, 1974; McDonald and Rasmussen, 1971; Westrum and Broderson, 1976).…”

“…The normal ultrastructural distribution of AChE activity in synaptic areas has been described in various sites in the CNS (Kasa, 1971; McDonald and Rasmussen, 1971), including the spinal trigeminal nucleus (Westrum and Broderson, 1976). Central synaptic regions show AChE activity predominantly localized to the immediate vicinity of or within synaptic clefts of axon terminals.…”