In vivo release of adenosine from cat basal ganglia-studies with a push pull cannula

The release of newly synthesized [(3)H]adenosine has been studied in vivo in cat caudate nucleus and substantia nigra, using a push pull cannula. In the presence of [(3)H]adenosine as precursor, spontaneously released [(3)H]adenosine was easily detectable in superfusates of the push pull cannula. In the caudate nucleus, potassium and veratridine caused a marked and reversible increase in [(3)H]adenosine release. The effect of veratridine was completely blocked by tetrodotoxin (TTX) although TTX had no action by itself. Ouabain as well as glutamate, also markedly increased the release of [(3)H]adenosine. The specific 5? nucleotidase inhibitor ?,?-methylene ADP, did not alter the increase in the amount of [(3)H]adenosine obtained by veratridine, although it diminished the spontaneous release of [(3)H]adenosine by about 20%. Push pull cannulae were also implanted simultaneously into the caudate nucleus and substantia nigra. Potassium applied into the caudate nucleus increased the local release of adenosine but did not change that observed in the substantia nigra. When potassium was applied into the substantia nigra, it also increased the local release of adenosine but did not change that observed in the caudate nucleus. The results are discussed in term of the possible existence of "purinergic neurons" and of the relation between the adenosine release and central nervous activity.