QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

HOME  |   SEARCH  |   ARCHIVE  |   SUBSCRIBE  |   CONTACT  |   HELP

This Article Full Text (PDF) Submit an eLetter Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Haydon, P. G. Articles by Zoran, M. Search for Related Content PubMed PubMed Citation Articles by Haydon, P. G. Articles by Zoran, M.

 Previous Article  |  Next Article 

Journal of Neuroscience, Vol 11, 3851-3860, Copyright © 1991 by Society for Neuroscience

ARTICLE

FMRFamide modulation of secretory machinery underlying presynaptic inhibition of synaptic transmission requires a pertussis toxin- sensitive G-protein

PG Haydon, H Man-Son-Hing, RT Doyle and M Zoran
Department of Zoology and Genetics, Iowa State University, Ames 50011.

The neuropeptide FMRFamide modulates synaptic transmission between identified neurons of the pond snail Helisoma trivolvis. FMRFamide causes a presynaptic inhibition of transmitter release by actions on ion channels and secretory machinery (Man-Son-Hing et al., 1989). The actions of FMRFamide on secretory machinery were studied using giant synapses that form between somata in culture. Using the calcium cage DM- nitrophen, synchronized, calcium-clamped release of neurotransmitter was promoted by UV photolysis. A series of UV flashes (15 msec duration) repeatedly promoted the transient synchronized release of neurotransmitter. Addition of FMRFamide reduced the magnitude of these flash-evoked inhibitory postsynaptic currents. Under conditions of synchronized transmitter release, FMRFamide modulates the secretory responsiveness to internal calcium. The release of neurotransmitter at somasoma synapses was determined to be quantal in nature. To test for the involvement of G-proteins in mediating the effects of FMRFamide on secretory machinery, the modulation of the frequency of miniature inhibitory postsynaptic currents (MIPSCs) was examined. Addition of FMRFamide reduced the frequency of MIPSCs without affecting intracellular free calcium measured with fura-2. Injection of a nonhydrolyzable analog of GTP, GTP gamma S, mimicked the effect of FMRFamide and reduced MIPSC frequency. Preinjection of the presynaptic soma with the A-protomer of pertussis toxin (PTX) prevented FMRFamide from reducing MIPSC frequency. Thus, a PTX-sensitive G-protein mediates the action of FMRFamide on secretory machinery. Similarly, preinjection of the presynaptic soma with PTX prevented FMRFamide from reducing the magnitude of action potential-evoked IPSC. Dose-response curves for the actions of FMRFamide on secretory machinery and calcium current were constructed and demonstrated that secretory machinery can be modulated at concentrations of FMRFamide (less than or equal to 10(-7) M) that do not affect calcium current magnitude. At a concentration of 10(-7) M FMRFamide, action potential-evoked synaptic transmission was reduced. Thus, synaptic transmission can be regulated by the modulation of secretory machinery, without a requirement for the modulation of ion channels.

This article has been cited by other articles:

				E. M. Silinsky Adenosine decreases both presynaptic calcium currents and neurotransmitter release at the mouse neuromuscular junction J. Physiol., July 15, 2004; 558(2): 389 - 401. [Abstract] [Full Text] [PDF]

				P. Lovell, B. McMahon, and N. I. Syed Synaptic Precedence During Synapse Formation Between Reciprocally Connected Neurons Involves Transmitter-Receptor Interactions and AA Metabolites J Neurophysiol, September 1, 2002; 88(3): 1328 - 1338. [Abstract] [Full Text] [PDF]

				S. Hess, P. Doroshenko, and G. Augustine A functional role for GTP-binding proteins in synaptic vesicle cycling Science, February 19, 1993; 259(5098): 1169 - 1172. [Abstract] [PDF]

Home  |   Search  |   Archive  |   Subscribe  |   Contact  |   Help