Dextro-phenylalanine as inhibitor of the noradrenaline release from the isolated rat hypothalamus.

In slices of isolated rat hypothalamus, the dextrophenylalanine (d-Phe) 3x10(-3)M produced an inhibition of a 47% in the fractional release of 3H-NA to the preparations of Holtzman rats, and of 39% to the Wistar rats, when the concentration of d-Phe (in this last) was of 1x10(-2)M, pointing that the effectiveness of the d-Phe is variable with the employed rat root. The mentioned effect is calcium dependent, for it was antagonized when the Ca++ was incremented in the medium of 1,68mM (normal) to 2,6mM. Neither atropine, nor phenoxybenzamine interfer the effect to the d-Phe, showing that it will not be due to mechanisms of alpha-adrenergic or muscarinic cholinergic negative feedback. For the moment it cannot be interpretated that the d-Phe effect is performed through specific negative feed-back receivers, for the possible operability of other kind of receptors such as PGs angiotensin, morphinic, etc., has not been discarded yet.