Effect of Ions on the Efflux of Acetylcholine from Peripheral Nerve

Abstract

The nerves from the walking leg of lobster released acetylcholine (ACh) even when the ends were tied off, although this release was significantly increased when the nerve endings were not tied. The resting nerves were kept in sea water containing physostigmine. In absence of physostigmine no ACh was found in the surrounding fluid. Removal of Ca from the sea water reduced the release of ACh, while increased concentrations of Ca had no significant effect. Removal of Mg++ or increased Mg++ concentrations in the presence of normal Ca + + concentrations increased the release of ACh. Increased K+ concentrations had a stimulating action on the efflux of ACh. Increased or reduced Na+ concentrations had only slight effects on the release of ACh in resting lobster nerve. During the 4 hr observation period the excised nerves were still able to synthesize ACh. The choline acetylase activity was stimulated by increased concentrations of Mg + + and K+. The effects of ions on the release of ACh are similar to those reported at the junction.

The Acetylcholine System in Peripheral Nerve*

“…Alteration of the Naf concentration in the sea water caused only small changes in the outflow. 40 Future experiments dealing with the effects of stimulation may clarify the role of Nat in this process.…”

Acetylcholine and lobster sensory neurones

“…More recently, Welsch & Dettbarn (1970) examined the subcellular distribution of ACh, ChAc, and acetylcholinesterase in extracts prepared from lobster walking leg nerve bundles. Dettbarn and his colleagues have been concerned with the possible involvement of the ACh system in axonal conduction (see Dettbarn, 1967) and have cited both a spontaneous release of ACh with changes in the ionic environment bathing nerve trunks (Dettbarn & Rosenberg, 1966) and the symmetrical distribution of the enzyme in E and I axons (Dettbarn, De Lorenzo & Brzin, 1971) (Hildebrand et al 1971 In general, our results demonstrate that the ability of an intact tissue to incorporate radioactive choline into ACh is roughly paralleled by the level of the enzyme ChAc in extracts of the tissue. The one exception was the degeneration experiment where first and second roots to abdominal ganglia were sectioned.…”

N- and L-Type Voltage-Gated Calcium Channels Mediate Fast Calcium Transients in Axonal Shafts of Mouse Peripheral Nerve

“…Notably, L- and N-type VGCCs expressed in peripheral nerve axons are the VGCCs subtypes which are involved in neurotransmitter release at Ribbon synapses and at conventional synapses between neurons, respectively (Catterall, 2011 ). Few older studies also show that axonal release in peripheral nerves resembles the axon terminal release in many respects, e.g., it depends on extracellular Ca 2+ and is stimulated by elevated extracellular K + (Dettbarn and Rosenberg, 1966 ; Vizi et al, 1983 ; Wieraszko and Ahmed, 2009 ). Yet, other investigators do not support these findings and suggest that the mechanism of axonal release in the peripheral nerves differs from release at synapses (Weinreich and Hammerschlag, 1975 ).…”