Pertussis toxin blocks the inhibitory effect of adenosine on rat cerebral cortical neurons

Rat cerebral cortex was injected with 2 micrograms of purified pertussis toxin, which inactivates various guanine nucleotide-dependent regulatory proteins. The spontaneous firing of cortical neurons in toxin-treated animals was unresponsive to adenosine or adenosine 5'-N-ethylcarboxamide applied iontophoretically in comparison with the pronounced inhibitory effects of these purines observed on neurons in the contralateral, saline-injected, hemisphere. Excitatory effects of acetylcholine were also reduced in the toxin-treated cortex. These findings implicate guanine nucleotide-dependent regulatory proteins (G proteins) in the inhibitory actions of adenosine on transmitter release.