Excitatory projection from the interpeduncular nucleus to central superior raphe neurons.

The projection from the interpeduncular nucleus (IP) to the central superior raphe nucleus (CS) was studied using electrophysiologic methods. IP stimulation generates monosynaptic EPSPs in a large number of CS neurons studied with latency of 1-2 ms. Intracellular peroxidase injections into CS neurons responding to IP shock confirmed the location and somatic origin of intracellular potentials. These findings document the existence of a direct excitatory projection from IP onto CS neurons.