NITRIC-OXIDE INCREASES DOPAMINE AND SEROTONIN RELEASE IN THE MEDIAL PREOPTIC AREA

NITRIC oxide (NO) is becoming recognized as an important intercellular messenger in the brain. The present experiment used microdialysis to examine the potential role of NO in the regulation of dopamine (DA) an d serotonin (5-HT) release in the medial preoptic area (MPOA) of freel y moving male rats. The NO precursor L-arginine (L-Arg, 100 mu M), adm inistered into the MPOA via the dialysis probe, increased extracellula r levels of DA, 5-HT, and the major metabolites of DA. These increases were blocked by the coadministration of the NO synthase inhibitor N-m onomethyl L-arginine (NMMA, 400 mu M). The inactive isomer D-arginine (100 mu M) was ineffective, and NMMA by itself decreased DA below base line levels. Thus, NO may modulate the release of DA and 5-HT in the M POA.