COLOCALIZATION OF SEROTONIN AND FMRFAMIDE-LIKE IMMUNOREACTIVITIES IN THE CENTRAL-NERVOUS-SYSTEM OF THE EARTHWORM, EISENIA-FETIDA

In the present study co-localization of serotonin and FMRFamide-like i mmunoreactivities was studied in the central nervous system of the ear thworm, Eisenia fetida. Alternate serial sections were stained with an tisera raised against serotonin and FMRFamide, using the peroxidase-an tiperoxidase method. The immunostained consecutive sections were compa red by light-microscopy and on reconstructed images using NIH Image an d Neurolucida programs. Although there was a large number of serotonin and FMRFamide-like immunoreactive neurons in the central nervous syst em of Eisenia, co-localization of immunostaining was relatively rare. In the cerebral ganglion no cells were found that stained for both ant isera. In the subesophageal and ventral cord ganglia the neurons react ing for both antisera represented approximately 17-23% and 10-14% of t he serotonin- and 7-11% and 9-17% of the FMRFamide-like immunoreactive cells, respectively. It is suggested, that FMRFamide-related peptides act as neuromodulators and may also influence the activity of seroton ergic neurons.