Sexually dimorphic concentrations of arginine vasotocin in sensory regions of the amphibian brain.

Arginine vasotocin (AVT) regulates reproductive behaviors in amphibians. We measured AVT in the brains of bullfrogs (Rana catesbeiana) and newts (Taricha granulosa) using radioimmunoassay. In bullfrogs, AVT concentrations were greater in males, compared to females, in the amygdala pars lateralis, optic tectum, and tegmentum. Concentrations in the dorsolateral nucleus were greater in females. In newts, AVT concentrations were also greater in the tectum and tegmentum of males. AVT may modulate dimorphic behaviors by acting at these sites.