R-type Ca2+ currents evoke transmitter release at a rat central synapse.
Voltage-dependent Ca2+ currents evoke synaptic transmitter release. Of six types of Ca2+ channels, L-, N-, P-, Q-, R-, and T-type, only N- and P/Q-type channels have been pharmacologically identified to mediate action-potential-evoked transmitter release in the mammalian central nervous system. We tested whether Ca2+ channels other than N- and P/Q-type control transmitter release in a calyx-type synapse of the rat medial nucleus of the trapezoid body. Simultaneous recordings of presynaptic Ca2+ influx and the excitatory postsynaptic current evoked by a single action potential were made at single synapses. The R-type channel, a high-voltage-activated Ca2+ channel resistant to L-, N-, and P/Q-type channel blockers, contributed 26% of the total Ca2+ influx during a presynaptic action potential. This Ca2+ current evoked transmitter release sufficiently large to initiate an action potential in the postsynaptic neuron. The R-type current controlled release with a lower efficacy than other types of Ca2+ currents. Activation of metabotropic glutamate receptors and gamma-aminobutyric acid type B receptors inhibited the R-type current. Because a significant fraction of presynaptic Ca2+ channels remains unidentified in many other central synapses, the R-type current also could contribute to evoked transmitter release in these synapses.
Wu
L G
LG
Abteilung Zellphysiologie, Max-Planck-Institut für medizinische Forschung, Jahnstrasse 29, D-69120 Heidelberg, Germany. lgwu@sunny.mpimf-heidelberg.mpg.de
Borst
J G
JG
Sakmann
B
B
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000818:Animals; D001418:Baclofen / Q000494:pharmacology; D001933:Brain Stem / Q000187:drug effects / Q000502:physiology*; D019256:Cadmium Chloride / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology*; D004558:Electric Stimulation; D005071:Evoked Potentials / Q000187:drug effects; D066298:In Vitro Techniques; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D009532:Nickel / Q000494:pharmacology; D009543:Nifedipine / Q000494:pharmacology; D009553:Nimodipine / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D010455:Peptides / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D018080:Receptors, GABA-B / Q000502:physiology; D018094:Receptors, Metabotropic Glutamate / Q000502:physiology; D013111:Spider Venoms / Q000494:pharmacology*; D013569:Synapses / Q000187:drug effects / Q000502:physiology*; D020867:omega-Agatoxin IVA; D020960:omega-Conotoxins
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D010455:Peptides; D018080:Receptors, GABA-B; D018094:Receptors, Metabotropic Glutamate; D013111:Spider Venoms; D020867:omega-Agatoxin IVA; D020960:omega-Conotoxins; C075851:omega-conotoxin-MVIIC; D009553:Nimodipine; C022838:nickel chloride; D009532:Nickel; D001418:Baclofen; D009543:Nifedipine; D019256:Cadmium Chloride