Case pg237, (n=3). Soma notes 6 HRP injs (which included virtually the entire extent of the stratum griseum superficiale, most of the intermediate collicular layer and the central portion of the deeper layers but did not encroach upon adjacent regions) in 3 different animals. Terminal notes labelled terminals, rercognized by their content of electron dense reaction prodduct, were found in OPN. They were scattered sparsely in within OPN and occcurred singly, rather than in clusters..