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Pharmacological characterization of calcium currents and synaptic transmission between thalamic neurons in vitro

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Item Type:Article
Title:Pharmacological characterization of calcium currents and synaptic transmission between thalamic neurons in vitro
Creators Name:Pfrieger, F.W. and Veselovsky, N.S. and Gottmann, K. and Lux, H.D.
Abstract:We recorded from pairs of cultured, synaptically connected thalamic neurons. Evoked excitatory postsynaptic currents (EPSCs) reversed at +17 mV and were blocked reversibly by 1 mM kynurenic acid, a glutamate receptor antagonist. NMDA and non-NMDA receptors mediated excitatory post-synaptic responses, as shown by selective block of EPSC components with 50 microM (+/-)-2-amino-5-phosphonopentanoic acid and 10 microM 6,7-dinitroquinoxaline-2,3-dione, respectively. Inhibitory postsynaptic responses were evoked less frequently and were blocked by the GABAA receptor antagonist (-)-bicuculline methochloride. The pharmacological profiles of whole-cell calcium currents and evoked EPSCs were compared. With 50 microM cadmium chloride (Cd), whole-cell low voltage-activated (LVA) calcium currents were reduced in amplitude and high voltage-activated (HVA) calcium currents and excitatory synaptic transmission were completely blocked. This suggests that the residual calcium influx through LVA channels into the presynaptic terminal does not suffice to trigger transmitter release. A saturating concentration of omega-conotoxin GVIA (omega-CgTx) (2.5 microM) blocked one-third of whole-cell HVA calcium currents and evoked EPSCs. The dihydropyridine nifedipine (50 microM) reversibly reduced whole-cell HVA calcium currents in a voltage-dependent manner but not excitatory synaptic transmission. Cd and omega-CgTx did not alter amplitude distributions of miniature EPSCs, demonstrating that the inhibition of synaptic transmission was due to block of presynaptic calcium channels. We conclude that excitatory glutamatergic transmission in thalamic neurons in vitro was mediated mainly by HVA calcium currents, which were insensitive to omega-CgTx and nifedipine.
Keywords:Calcium, Calcium Channel Blockers, Cultured Cells, Electrophysiology, Neurons, Neurotransmitter Agents, Synapses, Synaptic Transmission, Thalamus, Animals, Rats
Source:Journal of Neuroscience
ISSN:0270-6474
Publisher:Society for Neuroscience (U.S.A.)
Volume:12
Number:11
Page Range:4347-4357
Date:November 1992
Additional Information:Copyright (c) 1992 by The Society for Neuroscience
Official Publication:http://www.jneurosci.org/cgi/content/abstract/12/11/4347
PubMed:View item in PubMed

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