5-HT and dopamine modulates CaV1.3 calcium channels involved in postinhibitory rebound in the spinal network for locomotion in lamprey

Postinhibitory rebound (PIR) can play a significant role for producing stable rhythmic motor patterns, like locomotion, by contributing to burst initiation following the phase of inhibition, and PIR may also be a target for modulatory systems acting on the network. The current aim was to explore the PIR in one type of interneuron in the lamprey locomotor network and its dependence on low voltage-activated (LVA) calcium channels, as well as its modulation by 5-HT and dopamine. PIR responses in commissural interneurons, mediating reciprocal inhibition and left-right alternation in the network, were significantly larger than in motoneurons. The L-type calcium channel antagonist nimodipine reduced PIR amplitude by ∼50%, whereas the L-channel agonist BAY K 8644 enhanced PIR amplitude, suggesting that LVA calcium channels of the L-subtype (CaV1.3) participate in the PIR response. The remainder of the response was blocked by nickel, indicating that T-type (CaV3) LVA calcium channels also contribute. No evidence ...