Differential coupling of N- and P/Q-type calcium channels to glutamate exocytosis in the rat cerebral cortex.
In nerve terminals, the activation of Ca(2+) channels of either the P/Q or N type triggers glutamate release. In turn, presynaptic metabotropic glutamate receptors control this process through the modulation of these Ca(2+) channels. By measuring glutamate release from cerebrocortical nerve terminals we show that at physiological concentrations of extracellular Ca(2+), the agonist L(+)-2-amino-4-phosphonobutyrate only reduced the N-type channel coupled release. However, at lower concentrations of extracellular calcium the contribution of N-type channels was abolished and P/Q-type channels were entirely responsible for the remaining release of glutamate. Under these conditions, L(+)-2-amino-4-phosphonobutyrate was capable of reducing the P/Q-type channel mediated release. These results indicate that N-type Ca(2+) channels are less efficiently coupled to glutamate release than P/Q-type channels and that this differential coupling may have important implications for presynaptic modulation of synaptic transmission.
Millán
Carmelo
C
Departamento de BioquImica, Facultad de Veterinaria, Universidad Complutense, 28040 Madrid, Spain.
Sánchez-Prieto
José
J
D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology; D020864:Calcium Channels, N-Type / Q000378:metabolism*; D020865:Calcium Channels, P-Type / Q000378:metabolism*; D020907:Calcium Channels, Q-Type / Q000378:metabolism*; D002540:Cerebral Cortex / Q000187:drug effects / Q000378:metabolism*; D005089:Exocytosis / Q000187:drug effects / Q000502:physiology*; D018698:Glutamic Acid / Q000378:metabolism*; D051381:Rats; D013574:Synaptosomes / Q000187:drug effects / Q000378:metabolism
D020864:Calcium Channels, N-Type; D020865:Calcium Channels, P-Type; D020907:Calcium Channels, Q-Type; D018698:Glutamic Acid; D002118:Calcium