Simultaneous immunohistochemistry and autoradiography of peptides and 5-hydroxytryptamine in bird retina

A method was developed for the simultaneous demonstration of two specific cellular constituents. Cryostat sections of formaldehyde fixed tissue from retinae treated with ((3)H)-5-hydroxytryptamine were subjected to immunohistochemistry and subsequent autoradiography. The method takes advantage of the very efficient and specific uptake mechanism that many types of neurons possess which makes it possible to label them with radioactivity. With this method a study was made on the possible co-occurrence in the avian retina of 5-hydroxytryptamine on one hand and somatostatin, glucagon and substance P on the other. Substance P and 5-hydroxytryptamine were investigated in pigeon retina whereas 5-hydroxytryptamine and somatostatin or glucagon were investigated in chicken retina. Though a large number of cell bodies were examined no co-occurrence of 5-hydroxytryptamine and any of the peptides was found. The sensitivity of the method allows an assertion that if present, double labelled neurons are likely to number less than 0.5-1% of the respective populations.