Nitric oxide-containing neurons in the nervous ganglia of Helix aspersa during rest and activity: Immunocytochemical and enzyme histochemical detection

Nitric oxide synthase (NOS) immunoreactivity and staining for nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-diaphorase) activity are t wo cytochemical markers for nitric oxide (NO)-containing; neurons. The auth ors examined the changes in the distribution of NOS immunolabeling and NADP H-diaphorase reactivity in the cerebral and buccal ganglia of the terrestri al snail Helix aspersa during resting and active phases. During inactivity and after 1 day of activity, in the mesocerebrum and metacerebrum of the sn ails, there were several reactive neurons for both markers; after 7 days of activity, the number of reactive neurons was lower. Opposite results were obtained in the buccal ganglia, in which increased staining and numbers of reactive neurons were present in the active snails (after 1 day and 7 days of activity). Although the staining patterns for the two reactions were sim ilar, colocalization was not always observed. The comparison between inacti ve and active animals provided a more precise survey of NOS-containing neur ons in the snail cerebral ganglia than previously described. Moreover, it s uggested that not only is NO involved in distinct nervous circuits, but, as a ubiquitous molecule, it also plays a role in neuroprotection and neurope ptide release. (C) 1999 Wiley-Liss, Inc.