A stimulation-induced pause and burst in striatal cholinergic interneurons

Unlike the cholinergic cells of the Basal Forebrain that supply acetylcholine to areas, such as, the frontal cortex and hippocampus, the striatal cholinergic interneuron is the only source of acetylcholine in the striatum. The striatal cholinergic interneuron is a spontaneously active cell that has a regular, irregular and bursting firing pattern caused by intrinsic activity of ion channels, without any synaptic input. Additionally, the striatal cholinergic interneuron switches between these three firing patterns spontaneously exhibiting pauses and bursts of activity. Behaviorally, the striatal cholinergic interneuron learns to associate a cue, such as a light or a tone, with a reward. The learned response is exhibited as a pause followed by a burst in the spontaneous firing pattern. Synaptic activation of intrinsic currents that cause pausing and bursting may underlie the behaviorally conditioned pause and burst. The experiments presented here use patch clamp and aim to determine if intrinsic cellular mechanisms can be synaptically induced to cause a pause and burst in the striatal cholinergic interneuron's single spike firing pattern through stimulation of synaptic inputs in rat brain slices. In conclusion of these experiments, it was determined that stimulation in slices can activate synaptic inputs that cause a pause and burst in the striatal cholinergic interneuron's spontaneous firing pattern; an intrinsic ionic mechanism, the calcium-activated, slow afterhyperpolarization (sAHP) channel, likely underlies the pause response and an unknown mixed-cation channel underlies the burst response; and though not exhaustively studied, candidate neurotransmitters did not when individually antagonized block the stimulus-induced pause and burst.