NO donor SIN-1 potentiates monosynaptic reflexes in the cat spinal cord

The effect produced by the nitric oxide donor SIN-1 on monosynaptic reflexe s was examined. Experiments were performed on anesthetized, paralyzed and s pinalized cats. Lumbar monosynaptic reflexes were produced by stimulation o f [a afferents. Lv. application of SIN-1 (500 mug/kg) produced a mean marke d potentiation of 704% of pre-drug control (100%) in the amplitude of monos ynaptic reflexes. In addition, in other experiments a concentration-depende nt effect on the amplitude of monosynaptic reflexes was observed after micr oinjections of SIN-1 into the ventral horn (1 mul; 10(-12)-10(-3) M), with a mean facilitatory effect of 355%. In both cases, the potentiation was rev ersible 45 min after i.v. or local application of SIN-1. These results prov ide the first evidence that monosynaptic reflexes can be potentiated by nit ric oxide. NeuroReport 12:2667-2671 (C) 2001 Lippincott Williams & Wilkins.