Immunohistochemical Localization of Adenosine Deaminase

Aim of Investigation: Four peptides, substance P (SP), somatostatin (SS), cholesystokinin (CCK) and vasoactive intestinal polypeptide (VIP) have been found to occur, and to some extent coexist, in small sensory gangion peurones in the cat. These cells have cutaneous (and other) receptors responding to noxious mechanical, heat, cold, and combinations of these modalities, and to non-noxious stimuli. This study examines the relationship between a neurone's peptide content and its receptor modality. Method: In Sl ganglion exposed to colchicine for 24 hours intracellular recordings were made from C and A6 cells. Once the cutaneous receptive modality had been established the cell was injected with lucifer yellow, the ganglia fixed, sectioned and the PAP technique used to identify the cell's peptide content. Results: SP and CCK have been located in both noxious and non-noxious receptivecells. SS has not been observed in non-noxious receptive cells and VIP has not been observed in noxious receptive cells. All peptides occurred in both cells with cutaneous and with non-cutaneous receptors but SP occurred with highest incidence in the latter. Conclusions: It is unlikely that any simple relation exists between peptide content and a cell's receptor modality.