GABAergic and serotonergic modulation of calcium currents in rat trigeminal motoneurons.
We investigated the effects of a GABA(B) agonist baclofen, and serotonin, on the high voltage-activated Ca channel (HVACC) currents in trigeminal motoneurons. Immunohistochemical and reverse transcription-polymerization chain reaction (RT-PCR) studies demonstrated the expression of alpha(1C), alpha(1B), alpha(1A), and alpha(1E) subunits in the trigeminal motoneurons, which form L-, N-, P/Q-, and R-type Ca channels, respectively. By use of specific Ca blockers, it was found that N-type (38%), P/Q-type (27%), L-type (16 %), and R-type Ca currents (19%) contribute to HVACC I(Ba). Baclofen inhibited HVACC I(Ba) in the majority of trigeminal motoneurons tested (n=15 out of 16), whereas serotonin only did in a small population (n=5 out of 18). The I(Ba) inhibition by baclofen and serotonin was associated with slowing of activation kinetics, relieved by strong prepulse, and prevented by N-ethylmaleimide (NEM), indicative of mediation of Gi/Go. These data provide evidence that GABAergic and serotonergic inputs to trigeminal motoneurons regulate neuronal activities through the inhibition of HVACC currents.
Oh
Seog Bae
SB
Department of Physiology, College of Dentistry and Dental Research Institute, Seoul National University, South Korea.
Piao
Zheng Gen
ZG
Shin
Sang Sup
SS
Ren
Dongjun
D
Park
Kyungpyo
K
Kim
Joong Soo
JS
D000818:Animals; D001418:Baclofen / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism; D004594:Electrophysiology; D005033:Ethylmaleimide / Q000494:pharmacology; D018682:GABA Agents / Q000494:pharmacology*; D007150:Immunohistochemistry; D007700:Kinetics; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012701:Serotonin / Q000494:pharmacology; D018490:Serotonin Agents / Q000494:pharmacology*; D013997:Time Factors; D014276:Trigeminal Nerve / Q000378:metabolism*
D015220:Calcium Channels; D018682:GABA Agents; D018490:Serotonin Agents; D012701:Serotonin; D001418:Baclofen; D005033:Ethylmaleimide; D002118:Calcium