Serotonin modulates multiple calcium current subtypes in commissural interneurons of the neonatal mouse

Abbinanti MD, Harris-Warrick RM. Serotonin modulates multiple calcium current subtypes in commissural interneurons of the neonatal mouse. J Neurophysiol 107: 2212-2219, 2012. First published January 25, 2012; doi:10.1152/jn.00768.2011.-Calcium currents are critical to the intrinsic properties of neurons and the networks that contain them. These currents make attractive targets for neuro-modulation. Here, we examine the serotonergic modulation of specific calcium current subtypes in neonatal (P0-5) intersegmental commissural interneurons (CINs), members of the hindlimb locomotor central pattern generator in the mouse spinal cord. Previous work in our lab showed that serotonin (5-HT) excited CINs in part by reducing a calcium current and thus indirectly reducing the calcium-activated potassium current (Diaz-Rios et al. 2007). We have determined which calcium currents are targets of serotonin modulation. Utilizing whole cell voltage clamp and toxins to specific calcium current subtypes, we found that N-and P/Q-type currents comprise over 60% of the overall calcium current. Blockade of each of these subtypes alone with either omega-conotoxin GVIA or omega-agatoxin TK was unable to occlude 5-HT's reduction of the calcium current. However, coapplication of both blockers together fully occluded 5-HT's reduction of the calcium current. Thus, 5-HT decreases both N-and P/Q-type calcium current to excite neonatal CINs.