Brain acetylcholine, adenine nucleotides and their degradation products after intraperitoneal and intracerebral adenosine administration

The paper describes adenosine effects on the acetylcholine synthesis and the profiles of adenine nucleotides, adenosine, inosine, and hypoxanthine in the rat brain in vivo after intracerebral (intraventricular) and intraperitoneal administration of adenosine. Intracerebral as well as extracerebral adenosine injection caused a dose- and time-dependent increase of the cerebral acetylcholine level, which was not accompanied by an equal development of the contents of adenine compounds and their degradation products. However, a considerable turnover of adenosine was observed in the brain after both routes of administration concerning the nucleotide as well as the degradation pathway. The kinetics of the purified enzymes of choline acetyltransferase and acetylcholinesterase were not influenced by adenosine. By this, the adenosine-caused increase of the cerebral acetylcholine cannot be explained by a direct molecular attack of adenosine on the enzymes of the synthesis or degradation of acetylcholine. An indirect mechanism which includes cAMP was discussed as a possible interpretation at present.