Effect of neuropeptide-Y on tectal field potentials in the toad.

Field potentials (FP) recorded from the surface of toad's optic tectum (OT) to electrical stimulation of the contralateral optic nerve (ON) show initial positive deflections P*, followed by negative wave N and positive wave P; the former result from axonal inputs, the latter two resemble excitatory and inhibitory postsynaptic processes, respectively. Electrostimulation of the pretectum ipsilaterally to the recorded OT--preceeding ON-stimulation--strongly attenuates the N wave, suggesting pretectotectal inhibitory influences. The N wave of the tectal FP evoked by ON-stimulation is reduced, too, after application of the neuropeptide-Y (NPY) to the tectal surface. Previous authors have shown that frog's pretectum contains NPY immunoreactive pretectotectal projecting cells.