Ultrastructural changes in acetylcholinesterase activity in the deafferented spinal trigeminal nucleus

Abstract

Acetylcholinesterase (AChE) activity was investigated in synaptic areas of the cat spinal trigeminal nucleus (pars interpolaris and pars caudalis) ipsilateral and contralateral to complete retrogasserian rhizotomy. Vibratome sections of tissue taken from animals of 1, 3, 6, 14, and 21 days survival were examined by electron microscopy following a histochemical reaction for AChE activity employing a method based on the Karnovsky-Roots technique for demonstrating reaction product. As degeneration progressed with survival time, enzymatic activity was initially reduced in synaptic clefts of injured afferent terminals and subsequently was enhanced throughout the extracellular space, including within synaptic clefts of possibly reinnervated sites. These changes in enzymatic activity with primary deafferentation are discussed in relation to the process of reinnervation, the development of neuronal hyperactivity, and possible noncholinergic functions of AChE.

Experimental Trigeminal Nerve Injury

“…Some lesser degeneration is also evident in the contralateral nucleus caudalis , and ultrastructural evidence suggests that some of the degenerating terminals are those of primary afferents but that others may be derived from intrinsic interneurons affected transsynaptically. The degenerative/regenerative process in the nucleus following rhizotomy is also reflected in changes in the level and distribution of acetylcholinesterase activity (Wilson et al, 1988).…”