Figure 4.
Electrical coupling between V2a interneurons with similar membrane properties. A, Left, Responses of phasic V2a interneuron-1 (P1) to a series of current injections while the activity of the phasic P2 was monitored. Right, Responses of phasic P2 to a series of current injections while the activity of the phasic P1 was monitored. B, Left, When both neurons were depolarized above action potential threshold with bias current, they tended to fire action potentials synchronously. Right, Cross-correlogram of data taken from left trace. There was a positive peak at time 0. C, Left, Responses of tonic V2a interneuron T1 to a series of current injections while the activity of the tonic T2 was monitored. Right, Responses of T2 to a series of current injections while the activity of T1 was monitored. D, Left, When both neurons were depolarized above action potential threshold with bias current, they tended to fire action potentials synchronously. Right, Cross-correlogram of data taken from left trace. E, The electrical coupling between a different tonic pair was significantly reduced by 100 μm carbenoxolone. F, Left, Responses of tonic V2a interneuron1 to a series of current injections while the activity of the phasic interneuron-2 was monitored. Right, Responses of phasic V2a interneuron-2 to a series of current injections while the activity of the tonic interneuron-1 was monitored. No coupling was detected.