Author's present address
Calcitonin gene-related peptide acts presynaptically to increase quantal size and output at frog neuromuscular junctions
Article first published online: 22 SEP 2004
The Journal of Physiology
Volume 507, Issue 3, pages 689–695, March 1998
How to Cite
Van der Kloot, W., Benjamin, W. B. and Balezina, O. P. (1998), Calcitonin gene-related peptide acts presynaptically to increase quantal size and output at frog neuromuscular junctions. The Journal of Physiology, 507: 689–695. doi: 10.1111/j.1469-7793.1998.689bs.x
O. P. Balezina: Department of Human and Animal Physiology, Moscow State University, 119899 Moscow, Russia.
- Issue published online: 22 SEP 2004
- Article first published online: 22 SEP 2004
- (Received 19 September 1997; accepted after revision 26 November 1997)
- 1Calcitonin gene-related peptide (CGRP) is found in dense-cored vesicles in the motor nerve terminal.
- 2Exogenous CGRP increased the size of the quanta. The increase in size reached a maximum after about 40 min. The lowest effective concentration of human CGRP (hCGRP) was 0.8 nM. The action of hCGRP was antagonized by (−)-vesamicol, a drug that blocks active acetylcholine (ACh) uptake into synaptic vesicles, so it appears that hCGRP increases size by adding more ACh to the quanta. The action of hCGRP was antagonized by drugs that block the activation of protein kinase A (PKA). (In other preparations CGRP also activates PKA.)
- 3The hCGRP effect was not blocked by fragment 8–37, an antagonist of one class of CGRP receptor.
- 4hCGRP increases evoked quantal output and miniature endplate potential (MEPP) frequency, again by activating PKA.
- 5CGRP release was measured by radioimmunoassay. Release was increased by depolarization with elevated K+, but the amounts released appear to be below those needed to affect quantal size or output. Moreover, although elevated K+ can increase quantal size it acts by a pathway that does not involve PKA. We suggest that the most likely target of endogenously released CGRP is the regulation of circulation of the muscle.