Modulation of Purine Release from Electrically-Stimulated Cortical Slices of the Rat: Interaction with the Cholinergic System

Abstract

The activity and role of adenosine in the central nervous system have been extensively described in several recent reviews (Su et al. 1983; Dunviddie 1985; Snyder 1985) from which it appears that adenosine fulfills many of the criteria which define a neurotransmitter or neuromodulator. Adenosine is present in neuronal somata and axons of discrete brain areas including certain layers of the cerebral cortex (Braas et al. 1986). A release of adenosine from nervous tissue, evoked by electrical stimulation or by depolarizing agents, has been repeatedly demonstrated in both “in vivo” (Sulakhe and Phillis 1975; Lee et al. 1982) and “in vitro” studies (Pull and Mc Ilwain 1972; Hollins and Stone 1980; Mc Donald and White 1985). Adenosine reaches in the extracellular fluid of brain “in vivo” concentrations sufficient to exert physiological effects (Zetterstrom et al. 1982). Adenosine effects are exerted through specific receptors which can be distinguished by their actions on adenylate cyclase (Hamprecht and Van Calker 1980) or by the use of specific receptor agonists (Londos et al. 1977) into A₁ and A₂ subtypes.