Aims and objectives

This exercise is designed to investigate:

1. The distribution of the biogenic amine, 5-hydroxytryptamine (5-HT), in selected helminths.

2. The distribution of immunoreactivity to the neuropeptide, FMRFamide, in the nervous system of selected helminths.

Introduction

Immunocytochemistry is a method whereby antibodies, tagged with a visible fluorescent probe or fluorophore, are employed to detect antigens in tissue preparations using a specific antibody- antigen reaction. The most commonly employed immunocytochemical method is the indirect immunofluorescence technique (Coons et al., 1955) in which the primary antibody binds to the antigen in the tissue sample followed by a secondary antibody, labelled with a fluorescent tag, that binds to the primary antibody (Fig. 3.7.1A). The indirect technique allows for more than one secondary antibody to bind to the primary antibody, thereby ensuring amplification of the signal (stronger immunostaining).

The nervous system of helminth parasites is multifunctional and has been shown to be neurochemically complex (Halton & Gustafsson, 1996; Maule et al., 1996). 5-Hydroxytryptamine (5-HT) occurs extensively in the nervous systems of platyhelminth (flatworm) parasites and has been implicated as an excitatory neurotransmitter. FMRFamide is a tetrapeptide amide that was first isolated from the Venus clam, Macrocallista nimbosa, by Price & Greenberg (1977). It is now known that peptides with a similar structure to FMRFamide occur widely throughout invertebrate phyla and are commonly referred to as the FMRFamide-related peptides (FaRPs).