Depression by neuropeptide Y of noradrenergic inhibitory postsynaptic potentials of locus coeruleus neurones.

Intracellular recordings were performed in a pontine slice preparation of the rat brain containing the locus coeruleus (LC). The spontaneous firing of action potentials was prevented by passing continuous hyperpolarizing current via the recording electrode. Focal electrical stimulation evoked a synaptic depolarization (PSP) followed by a hyperpolarization (IPSP). Neuropeptide Y (NPY; 0.1 mumol/l) inhibited the IPSP only. Pressure ejection of noradrenaline produced hyperpolarization which was potentiated in the presence of NPY (0.1 mumol/l). Hence, NPY appears to inhibit the release of noradrenaline from dendrites or recurrent axon collaterals of LC neurones.