PRESENCE OF CALMODULIN AND NADPH-DIAPHORASE ACTIVITY BUT NOT OF NEURONAL NITRIC-OXIDE SYNTHASE IN THE SUBCOMMISSURAL ORGAN OF THE MONGOLIANGERBIL

The subcommissural organ (SCO) and the ventricular ependyma of the thi rd ventricle of the Mongolian gerbil (Meriones unguiculatus) exhibit a highly positive histochemical reaction to NADPH-diaphorase and a cons iderable immunocytochemical expression of calmodulin. The SCO, however , does not display an immunocytochemical response to the neuronal isof orm of nitric oxide synthase (NOS) whereas it was demonstrated in the ventricular ependyma. Since the NADPH-diaphorase, which detects all is oforms of NOS, was clearly positive at the level of the SCO, the obtai ned results suggest that the SCO of the Mongolian gerbil produces nitr ic oxide but contains a NOS whose antigenic specificity differs from t hat of the neuronal isoform of this enzyme.