Excitatory and inhibitory effects of adenosine on the neurotransmission in the hippocampal slices of guinea pig.

Postsynaptic potentials (PSPs) were recorded from the granular cell layer of guinea pig hippocampal slices. Application of adenosine at a concentration of more than 10 microM in the incubation medium depressed the amplitude of the PSP, but adenosine at a concentration of 10 nM to 1 microM enhanced the amplitude of the PSP. The dose-response curve of the effect of adenosine showed an excitatory and inhibitory biphasic pattern. Adenosine analogues such as adenosine triphosphate (ATP), adenosine diphosphate (ADP) and nicotinamide adenine dinucleotide (NAD) showed similar biphasic effects, however beta-gamma-methyleneadenosinetriphosphate (beta-gamma-ATP), 5'-N-ethylcarboxamidoadenosine (NECA). N6-cyclohexyladenosine (CHA) and N6-R-phenylisopropyladenosine (RPIA) revealed only inhibitory effects.