Nitric oxide synthase (NOS) in the brain of the cephalopod Sepia officinalis.

Nitric oxide synthase-like protein (NOS) is shown to be present in specific regions of the central nervous system (CNS) of the cephalopod mollusk S. officinalis (cuttlefish). NOS activity, which is Ca2+/calmodulin dependent, was detd. by measuring the conversion of L-[14C]arginine in L-[14C]citrulline. The partially purified NOS from brain and optic lobes exhibited on SDS-PAGE a band at 150 kDa that was immunolabeled by antibodies raised against the synthetic peptide corresponding to the amino acids 1414-1429 of the C-terminus of rat nNOS. This same antibody was then used for immunohistochem. staining of serial sections of the cuttlefish CNS to reveal localized specific staining of cell bodies and fibers in several lobes of the brain. Staining was found in many lower motor centers, including cells and fibers of the inferior and superior buccal lobes (feeding centers); in some higher motor centers (anterior basal and peduncle lobes); in learning centers (vertical, subvertical, and superior frontal lobes); and in the visual system [retina and deep retina (optic lobe)]. Immunopositivity was also found in the olfactory lobe and organ and in the sucker epithelium. These findings suggest that nitric oxide (NO) may be involved as a signaling mol. in feeding, motor, learning, visual, and olfactory systems in the cuttlefish brain. The presence of NOS in the cephalopod cerebellum and learning centers is discussed in the context of the vertebrate CNS.