Voltammetric detection of nitric oxide (NO) in the rat brain: its variations throughout the sleep-wake cycle.

A sensor allowing the specific detection of nitric oxide (NO) is reported. Together with differential pulsed voltammetry, it allows the detection of a 650 mV signal either in NO solutions or in the rat frontal cortex. The intraperitoneal (i.p.) administration of a NO donor (S-nitrosoglutathione, 20 mg/kg i.p.) increases the signal height (+30%) while that of a nitric oxide synthase (NOS) inhibitor like L-nitro-arginine-p-nitro-anilide (100 mg/kg i.p.), produces its complete disappearance in the cortex of anesthetized rats. These results suggest that the 650 mV signal might be NO-dependent. Some other NOS inhibitors have been found either inefficient (L-nitro-arginine-methyl-ester) or partially efficient (7-nitro-indazole) on the signal height. In freely moving rats, also equipped with polygraphic electrodes, the signal measured in the frontal cortex exhibits the highest height during waking. It decreases during slow-wave sleep (-6%) and paradoxical sleep (-9%).