title: Developmental changes in presynaptic calcium channels coupled to glutamate release in cultured rat hippocampal neurons.
abstract: Excitatory synaptic transmission in the hippocampus involves the participation of at least two types of presynaptic Ca2+ channels, N-type channels sensitive to omega-conotoxin GVIA (omega-CTx GVIA) and Q-type channels sensitive to omega-agatoxin IVA (omega-Aga IVA). Hippocampal pyramidal neurons in cell culture were used to examine the participation of these two classes of channels at different stages of synapse development. Specific Ca2+ channel toxins were used to block presynaptic Ca2+ channels while whole-cell voltage-clamp recordings were used to record evoked EPSCs in postsynaptic neurons. At immature synapses (cells in culture for 10-15 d), omega-CTx GVIA (1-5 microM) blocked transmission by more than 80% while omega-Aga IVA (1 microM) was less effective. In older cultures, however, omega-Aga IVA (1 microM) was more effective than omega-CTx GVIA (1-5 microM) in blocking synaptic transmission. The pharmacological properties of the omega-Aga IVA sensitive component of synaptic transmission were examined in more detail using omega-Aga IVA and omega-conotoxin MVIIC (omega-CTx MVIIC). The properties of this component of transmitter release indicated that a Q-type Ca2+ channel was involved in presynaptic Ca2+ entry. The results suggest that different classes of presynaptic Ca2+ channels begin to participate in transmitter release at different times during synapse development and maturation.
authors.affiliation: Department of Pharmacological and Physiological Sciences, University of Chicago, Illinois 60637, USA.
authors.forename: K P
authors.initials: KP
authors.lastname: Scholz
authors.forename: R J
authors.initials: RJ
authors.lastname: Miller
mesh_terms: D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology*; D002478:Cells, Cultured; D016922:Cellular Senescence; D005071:Evoked Potentials / Q000187:drug effects / Q000502:physiology; D006624:Hippocampus / Q000502:physiology*; D008978:Mollusk Venoms / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D010455:Peptides / Q000494:pharmacology*; D017966:Pyramidal Cells / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D013111:Spider Venoms / Q000494:pharmacology*; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology*; D013997:Time Factors; D020867:omega-Agatoxin IVA; D020866:omega-Conotoxin GVIA
chemical_list: D002121:Calcium Channel Blockers; D015220:Calcium Channels; D008978:Mollusk Venoms; D010455:Peptides; D013111:Spider Venoms; D020867:omega-Agatoxin IVA; D020866:omega-Conotoxin GVIA