Specific and potent interactions of carbamazepine with brain adenosine receptors.

Carbamazepine, a drug effective in pain, seizure, and affective disorders, was screened for its ability to interact with a variety of neurotransmitter and neuromodulator binding sites on brain membranes. The most potent effect was observed on adenosine antagonist ( [3H]DPX) binding to the adenosine receptor (KI = 3.5 +/- 0.4 microM) followed by adenosine agonist ( [3H]CHA) binding (KI = 24.5 +/- 3.6 microM). Lower potency effects were observed on benzodiazepine receptors, and no inhibition was seen in a variety of other systems. The inhibition of adenosine receptor binding by carbamazepine was competitive. No correlation was observed between the potency of a series of carbamazepine analogs as inhibitors of either ( [3H]DPX, [3H]CHA or [3H]diazepam binding and their ability to inhibit electroshock-induced convulsions, suggesting that the anticonvulsant properties of these agents are not mediated by the adenosine receptor, but raising the possibility that other clinical effects of carbamazepine may relate to its ability to act at the adenosine receptor.