Microinjection of neuropeptide Y into the superficial dorsal horn reduces stimulus-evoked release of immunoreactive substance P in the anaesthetized cat.

In barbiturate anaesthetized spinal cats, antibody microprobes were used to measure release of immunoreactive substance P in the superficial dorsal horn following electrical stimulation of unmyelinated primary afferents of the ipsilateral tibial nerve. Prior microinjection of neuropeptide Y (0.2-0.6 microliters of 10(-5) mol/l solution) in the region of the substantia gelatinosa reduced the evoked release of immunoreactive substance P for up to 40 min. Microinjection of similar volumes of phosphate-buffered saline at similar sites was without effect. This action of neuropeptide Y could contribute to analgesia, particularly if this neuropeptide is co-released with noradrenaline from axon terminals in the superficial dorsal horn.