Autoradiographic localization of dihydrotestosterone and testosterone concentrating neurons in the brain of the oyster toadfish

Abstract

Vertebrate species with male mating calls or songs tend to have sexually dimorphic sonic neurons that concentrate gonadal steroids. The distribution of [ 3H]dihydrotestosterone- and testosterone-concentrating neurons was examined in oyster toadfish ( Opsanus tau), males of which produce a courtship boatwhistle call. Labeled cells in the forebrain were found in the posterior nucleus of the dorsal telencephalon (Dp), a pallial structure, the supracommissural nucleus of the ventral telencephalon (Vs), nucleus preopticus parvocellularis anterior (PPa) and other preoptic nuclei, the ventral, dorsal and caudal hypothalamus. Positive brainstem areas included the optic tectum, torus semicircularis, nucleus lateralis valvula, a periventricular nucleus of the rostral medulla and the inferior reticular formation. Compared to estrogen, androgens labeled fewer sites in the forebrain and more in the brainstem. Two of the positive sites, Vs and PPa, have been implicated in boatwhistle production. Many sites that connect to these areas in teleosts likewise concentrate steroids. Unlike the situation in frogs, birds, and one other teleost, the toadfish sonic motor nucleus did not concentrate androgens. Androgen labeling in the posterior nucleus of the dorsal telencephalon represents the first autoradiographic demonstration of steroid concentration in the pallium of a teleost forebrain.