A study of the mechanism of Ca2+ current inhibition produced by serotonin in rat dorsal raphe neurons
Calcium currents and their modulation by 5-HT were studied using both whole-cell and single-channel patch-clamp techniques in acutely isolated adult rat dorsal raphe neurons. Evidence for three types of Ca channels (T, N, L) was obtained in both whole-cell and single-channel experiments. Approximate...
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Published in | The Journal of neuroscience Vol. 11; no. 11; pp. 3594 - 3609 |
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Main Authors | , , |
Format | Journal Article |
Language | English |
Published |
Washington, DC
Soc Neuroscience
01.11.1991
Society for Neuroscience |
Subjects | |
Online Access | Get full text |
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Summary: | Calcium currents and their modulation by 5-HT were studied using both whole-cell and single-channel patch-clamp techniques in acutely isolated adult rat dorsal raphe neurons. Evidence for three types of Ca channels (T, N, L) was obtained in both whole-cell and single-channel experiments. Approximately 4% of the total high-threshold Ca current (L-type) was sensitive to dihydropyridines (DHPs) while approximately 40% of the Ca current (N-type) was sensitive to omega-conotoxin (omega-CgTx). About 56% of the whole-cell current was insensitive to either DHPs or omega-CgTx and may thus represent a different kind of Ca current. 5-HT reduced raphe neuron Ca currents by approximately 50%, while slowing activation. 5-HT inhibited both omega-CgTx-sensitive and -insensitive Ca current. Inhibition by 5-HT was voltage dependent; prepulses to +80 mV lasting for 20 msec almost completely abolished the 5-HT-mediated inhibition. The voltage dependence of the response to 5-HT suggested that trains of action potentials might overcome the inhibition due to 5-HT. Trains of brief depolarizations were used to simulate action potentials; only about 5% of the 5-HT-induced inhibition was relieved by the trains. These results suggest that while large depolarizations could restore the Ca current inhibited by 5-HT, physiological stimuli, such as trains of action potentials, could not. The action of 5-HT was made irreversible by inclusion of GTP-gamma-S in the patch pipette, suggesting a G-protein mediation of the response to 5-HT. |
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ISSN: | 0270-6474 1529-2401 |
DOI: | 10.1523/jneurosci.11-11-03594.1991 |