Gastrin-cholecystokinin immunoreactivity in the central nervous system of Helix aspersa during rest and activity

The immunostaining pattern for the peptide gastrin/cholecystokinin 8 (gastr in/CCK8) in the molluscan central nervous system has been considered. The c hanges in the distribution of gastrin/CCK8 immunoreactivity were analyzed i n the neurons of different areas of the cerebral ganglia (mesocerebrum and metacerebrum) and in the buccal ganglia of the terrestrial snail Helix aspe rsa, during rest and active phases. During the period of inactivity and aft er one day of activity, there were several immunoreactive neurons in the me socerebrum and metacerebrum of the snails and in the buccal ganglia, wherea s after 7 days of activity the number of labeled neurons decreased. Data su ggested a storage of gastrin/CCK8 in the neurons when behavioral activities in which the peptide is involved (such as feeding-related behavior) are su ppressed or reduced. The different percentage of gastrin/CCK8 immunoreactiv e neurons in the left and right mesocerebrum provides information about the activities controlled by these neurons, which could be related to the adap tive evolution and plasticity of the brain in terrestrial pulmonates. (C) 2 000 Wiley-Liss, Inc.