Pertussis toxin blocks the effects of alpha 2-agonists and antagonists on locus coeruleus activity in vivo.

This study assessed the effects of pertussis toxin, which is known to inactivate G proteins and therefore to block receptors linked to G proteins, on electrophysiological activity of the locus coeruleus in vivo. Pertussis toxin was injected into the lateral cerebral ventricle of rats, and locus coeruleus activity was then recorded. Compared to vehicle-injected control animals, pretreatment with pertussis toxin markedly increased the spontaneous firing rate of locus coeruleus neurons. In addition, the alpha 2-antagonist idazoxan was no longer able to augment either spontaneous or evoked locus coeruleus activity after pretreatment with pertussis toxin. Finally, pretreatment with pertussis toxin made locus coeruleus neurons resistant to inhibition by the alpha 2-agonist clonidine. These results are consistent with the view that pertussis toxin blocks alpha 2-receptors, receptors linked to G proteins, in vivo.