Degeneration and regeneration of autonomic nerve endings in the anterior part of rhesus monkey ciliary muscle

Abstract

The autonomic nerve plexus of the ciliary muscle was examined with the electron microscope in normal rhesus monkeys of different ages. In the anterior region of the muscle, at the boundary with the poorly innervated scleral spur and trabecular meshwork, 3.8-7.1% of the axons exhibit either degenerative or regenerative features. The cytoplasm of degenerating axons contains lamellated, dense and multivesicular bodies, vesicles, whorls of filaments, and membranous debris. The plasma membrane is often discontinuous and, on occasion, axonal debris and degenerative organelles are freely dispersed in the connective tissue spaces of the muscle. Degenerating axons contain a granular reaction product when stained for acid phosphatase activity. Regenerating axons are characterized by tightly packed mitochondria, glycogen particles, and aggregates of synaptic vesicles; they synapse with muscle cells and are negative to the acid phosphatase reaction. A quantitative analysis showed that in the anterior region of the ciliary muscle degenerating and regenerating axons increase in number with age, although the total number of axonal profiles remains constant. In the age groups examined, degenerating axons occurred with the same frequency as regenerating axons, thus, the age-dependent increase in axonal degeneration is accompanied by a parallel increase in axonal regeneration. We conclude that autonomic nerve endings in the anterior part of the ciliary muscle undergo a continuous process of renewal that is more prominent in old age.

Patterns of motor innervation in the pectoral muscle of adult Xenopus laevis: evidence for possible synaptic remodelling.

“…These findings, together with the observation of morphological signs of regression in some motor endings, support the view of Barker & Ip (1965), Tuffery (1971) and Ip (1974), that adult muscles are subjected to a continuous process of synaptic degeneration and regeneration (see also Cardasis & Padykula, 1979). In agreement with this interpretation, clear electron microscopic evidence of synaptic degeneration in normal adult animals has been obtained in the central nervous system of the rat (Sotelo & Palay, 1971) and in the ciliary muscle of the monkey (Townes-Anderson & Raviola, 1978).…”

Development and Aging of Cholinergic Synapses

“…Negative changes in ACh levels are seen earlier in the iris than in the ganglion. [21] have dem onstrated early degenerative changes in the endings of axons innervating adult mamma lian ciliary muscles, which could lend mor phological support to our biochemical data. Similar changes, however, have not been reported in the avian iris.…”

Naturally Occurring Degrading Events in Axon Terminals of the Dentate Gyrus and Stratum lucidum in the Spiny Mouse <i>(Acomys cahirinus)</i> during Maturation, Adulthood and Aging

“…Finally, nondamaging normal patterns of functional activity are also supposed to in duce structural modification, so that in the mature ner vous system synaptic plasticity seems an ongoing natural process [17,18]. In this concept, there is a continuous loss and reaquisition of synaptic contacts which result in structural remodelling of functional circuits in response to normal physiological interactions between organism and environment (19)(20)(21)(22)(23); for recent review see refs [24][25][26].…”