Activation of presynaptic alpha-noradrenaline receptors in rat brain by the potent dopamine-mimetic N,N-dipropyl-5,6-ADTN.

Rat cerebral cortex slices labeled with 3H-noradrenaline (NA) were superfused and 3H-NA release was induced with 20 mM K+. The release of 3H-NA was not affected by DA (1 micro M), but was inhibited by the 2-aminotetralins, 5,6-ADTN and N,N-dipropyl-5,6-ADTN (at a concentration of 1 micro M) by about 27% and 65%, respectively. The inhibitory effect of N,N-dipropyl-5,6-ADTN was concentration-dependent (3 x 10(-8) to 3 x 10(-7) M) and was antagonized by phentolamine but not by fluphenazine. The data indicate that, in addition to activating dopamine receptors, N,N-dipropyl-5,6-ADTN stimulates presynaptic alpha-NA receptors.