Li, Yu-Wen, Patrice G. Guyenet, and Douglas A. Bayliss. "Voltage-dependent calcium currents in bulbospinal neurons of neonatal rat rostral ventrolateral medulla: modulation by α2-adrenergic receptors." Journal of neurophysiology79.2 (1998): 583-594.
Previous research has shown that both high voltage activated (HVA) and low voltage activated (LVA) calcium channels are present in the brain and may play different physiological roles. The HVA calcium channels consist mostly of N type, P/Q-type, and to a lesser extent L-type components which also contribute to different physiological processes such as neurotransmission, and calcium mediated gene expression. Until this study, little was known about calcium channel properties in the RVLM. However, it was known that C1 neurons in the RVLM expressed alpha 2A-adrenergic receptors that had been shown to inhibit calcium channels in other neurons via activation of an inwardly rectifying potassium conductance. Through the combination of using 2A-adrenergic receptor agonists and antagonists with electrophysiology, this study was able to characterize calcium channels and their regulation via norepinephrine for the first time. Results showed that the HVA current consisted mainly of N-type calcium channels, with a significant but lesser contribution from P/Q-type. They also found small, but present L-type calcium channel activity. As for LVA current, they found it was present in the RVLM and was activated with a much lower (~-50mV compared to ~0mv) as expected. Conclusively, the study revealed that norepinephrine mediated activation of alpha 2-adrenergic receptors is able to inhibit HVA currents, specifically N-type and P/Q-type, but not LVA currents. This study was relevant to MeMRI studies because manganese enters neurons through active L-type calcium channels. If little L-type calcium channel current is present, it would need to be addressed for future studies using MeMRI to examine neuroplasticity in the RVLM.
~JI
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