Factors influencing the release of noradrenaline from hypothalamic slices of the possum, Trichosurus vulpecula.

Slices of hypothalamus of the possum, Trichosurus vulpecula, were incubated with 3H noradrenaline and the subsequent spontaneous and K+-induced effluxes of 3H measured. Unchanged 3H noradrenaline comprised virtually all the K+-induced efflux, indicating that there was little, if any, metabolism of the amine after its release. Receptor-modulation of the K+-induced efflux of 3H was shown by inhibition of this efflux by noradrenaline, clonidine, angiotensin II and leu-enkephalin, and by the increase in efflux produced by yohimbine and isoprenaline. It is concluded that, in the possum, the control of spontaneous and K+-induced release of noradrenaline in the hypothalamus is similar to that in eutherian mammalian brain.