Synaptic repression at crayfish neuromuscular junctions. II. Evidence for calcium involvement
✍ Scribed by Gupta, Anuj ;Smith, Edward ;Vélez, Samuel J.
- Publisher
- John Wiley and Sons
- Year
- 1993
- Tongue
- English
- Weight
- 860 KB
- Volume
- 24
- Category
- Article
- ISSN
- 0022-3034
No coin nor oath required. For personal study only.
✦ Synopsis
Abstract
The inability of synaptic junctions to generate normalsized postsynaptic potentials under normal physiological conditions was studied at crayfish neuromuscular synapses. Synaptic repression in the superficial flexor muscle system of the crayfish was induced by surgery: the nerve was cut in the middle of the target field, and the lateral muscle fibers were removed. After this surgery, the remaining medial synapses were unable to generate normal‐sized junction potentials (jp) over the medial muscle population. In an attempt to study the mechanism underlying this response, we varied the extracellular calcium concentration of the Ringers solution bathing the preparation, in both repressed and control animals, while monitoring the size of the same junction potential. The junction potential generated by the spontaneous activity of the nerve increased in size with increasing calcium concentrations in control animals, but failed to do so in repressed animals, that is, changes in external calcium concentrations did not affect repressed synapses. However, in the presence of the calcium ionophore A23187, control and repressed synapses both show an increase in the junction potential sizes they generate. Our data suggest that calcium is involved in the mechanisms that underlie synaptic repression in this crustacean neuromuscular system. © 1993 John Wiley & Sons, Inc.