[Effects of L-NNA on postsynaptically evoked potential of oculomotoneurons in cats]

The present study was performed to explore the effect of endogenous nitric oxide (NO) on synaptic transmission between neurons located in Forel's field H (FFH) and vertical oculomotoneurons (OMNs) innervating the inferior oblique (IO) muscle in cats. The amplitude of monosynaptic excitatory field potential in the IO OMNs pool induced by stimulating FFH began to decrease gradually 2-3 min after intracarotid administration of L-NNA, an NO synthase inhibitor, reached its minimum by 6-10 min, and was followed by a slow recovery. This effect of L-NNA could be prevented by pre-administration of NO precursor L-arginine, without changing the field potential by itself. The results suggest that there is an endogenous NO release in the oculomotor nuclear, which can potentiate synaptic transmission between FFH neurons and OMNs.