Localization of FMRFamide- and ACEP-1-like immunoreactivities in the nervous system and heart of a pulmonate mollusc, Achatina fulica.

Immunohistochemical localization of two neuropeptides possibly involved in the regulation of cardiac activity in a pulmonate mollusc, Achatina fulica Férussac, was studied. On the ventral surface of the right cerebral ganglion, more than 50 neurons with diameters of 30-50 microns showed immunoreactivity to the antiserum of the neuropeptide FMRFamide. Many were also immunoreactive to an antiserum raised against Achatina cardio-excitatory peptide-1 (ACEP-1). Although FMRFamide-like immunoreactive neurons occurred in all components of the subesophageal ganglia, identifiable ACEP-1-like immunoreactive neurons were located only in the visceral ganglion and the right parietal ganglion. In the heart, FMRFamide- and ACEP-1-like immunoreactive fibers were restricted to the atrium and the aortic end of the ventricle, consistent with morphological observations of cardiac innervation. The present results suggest that FMRFamide- and ACEP-1-like peptides are involved in regulating the heart beat of this snail.