Islet-activating protein (pertussis toxin) diminishes ?2-adrenoceptor mediated effects on noradrenaline release

Abstract

The effect of islet-activating protein (IAP) on α₂-adrenoceptor mediated modulation of noradrenaline release in the rabbit hippocampus was studied. Slices of the hippocampus were incubated for 6 h with IAP, subsequently loaded with³H-noradrenaline and superfused continuously. IAP-pretreatment significantly enhanced the electrically evoked transmitter release and diminished the facilitatory effect of the α₂-adrenoceptor antagonist yohimbine. In addition, the inhibitory effect of the α₂-adrenoceptor agonist clonidine was reduced. These results provide circumstantial evidence that an inhibitory guanine-nucleotide-binding protein, most probably N₁ of a presynaptically located adenylate cyclase, is involved in the α₂-autoreceptor mediated modulation of noradrenaline release.