Modulation of the neural control of the clasp reflex in male Xenopus laevis by androgens: a multidisciplinary study.

The neural control of the clasp reflex in male Xenopus laevis has been studied by using anatomical, electrophysiological, and biochemical techniques. Neurons in spinal segment 2 of castrated males accumulate label after injection of [3H]-dihydrotestosterone; these neurons are distributed within the rostral portions of the motoneuronal pools of the sternoradialis and flexor carpi radialis muscles. In vitro recordings from the nerve to the sternoradialis muscle in the isolated spinal cord preparation from castrated male Xenopus showed increased activation to paired dorsal root stimulation after addition of dihydrotestosterone to the bath. This increase could be prevented by prior administration of cycloheximide. The reducing enzyme testosterone 5 alpha-reductase is present and is selectively distributed in male Xenopus spinal cord. It is speculated that the androgens may alter patterns of neuronal activity leading to the "clasp" muscles and thereby influence myosin types within these muscles.