“…Since the demonstration that testosterone can be reduced to its metabolite 5a-dihydrotestosterone or aromatized to oestrogens at target tissues within the central nervous system (Kniewald, Massa & Martini, 1970;Weisz & Gibbs, 1974;Minguell & Sierralta, 1975), there has been much interest in the possible roles of androgens and their naturally occurring metabolites in mediating 'androgendependent' behaviour. It has been shown that, while 5a-dihydrotestosterone will maintain the integrity of the reproductive tract in castrated rats, it cannot maintain sexual behaviour (McDonald et al, 1970;Feder, 1971; Whalen & Luttge, 1971); normal mounting and ejaculatory responses are, however, achieved after the simultaneous administration of small amounts of oestradiol (Baum & Vreeburg, 1973;Larsson, Södersten & Beyer, 1973;Feder, Naftolin & Ryan, 1974).…”