PT  - JOURNAL ARTICLE
AU  - NJ Penington
AU  - JS Kelly
AU  - AP Fox
TI  - A study of the mechanism of Ca2+ current inhibition produced by serotonin in rat dorsal raphe neurons
AID  - 10.1523/JNEUROSCI.11-11-03594.1991
DP  - 1991 Nov 01
TA  - The Journal of Neuroscience
PG  - 3594--3609
VI  - 11
IP  - 11
4099  - http://www.jneurosci.org/content/11/11/3594.short
4100  - http://www.jneurosci.org/content/11/11/3594.full
SO  - J. Neurosci.1991 Nov 01; 11
AB  - 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.(ABSTRACT TRUNCATED AT 250 WORDS)