ASAY, M.J.*; BOYD, S.K.: Distribution of arginine vasotocin in the brain of a non-vocalizing anuran (Ascaphus truei)

Tailed frogs (Ascaphus truei) are endemic to the Pacific Northwest and are considered the most primitive extant anuran. In addition, unlike most anurans, they do not vocalize. Arginine vasotocin (AVT) is a neuropeptide that modulates many amphibian reproductive behaviors, including mating calls. The distribution of AVT-immunoreactive (AVT-ir) cells in the brain of Ascaphus could provide insight into AVT control of behavior in amphibians. We used immunocytochemistry and a rabbit polyclonal antibody raised against vasopressin to detect putative AVT-ir cells and fibers in brains from adult male and female Ascaphus. The overall distribution of immunoreactivity was more restricted in Ascaphus than previously reported for other anurans. Significant populations of AVT-ir cells were found in the magnocellular preoptic nucleus and suprachiasmatic nucleus in the diencephalon. A much smaller population of cells was found spanning the dorsal and ventral striatum. AVT-ir fibers were found in some areas that control vocal behavior in other anurans. AVT may thus have alternative functions in these areas in Ascaphus. Supported by NSF IBN95-14305.