Adenosine-mediated synaptic inhibition: partial blockade by barium does not prevent anti-epileptiform activity.
Adenosine-induced inhibition of evoked postsynaptic potentials (PSPs) and epileptiform burst firing in the CA1 subfield of rat hippocampal slices was studied with intracellular recordings in vitro. Adenosine (50 microM) caused a membrane hyperpolarization which was abolished during superfusion with 2 mM Ba2+. The adenosine-induced inhibition of the PSPs was still evident, although the magnitude of the effect was significantly reduced. Adenosine also reduced Ba(2+)-induced burst firing, but less effectively than it did bursts evoked by TEA (5 mM). The results suggest that adenosine inhibits synaptic transmission and epileptiform activity by at least 2 mechanisms: a postsynaptic barium-sensitive increase in gK and a presynaptic effect independent of this adenosine-evoked outward potassium conductance.
Birnstiel
S
S
Harvard Medical School, Brockton, Massachusetts.
Gerber
U
U
Greene
R W
RW
D000200:Action Potentials / Q000187:drug effects; D000241:Adenosine / Q000037:antagonists & inhibitors / Q000502:physiology*; D000818:Animals; D001464:Barium / Q000494:pharmacology*; D004566:Electrodes; D004827:Epilepsy / Q000517:prevention & control*; D005071:Evoked Potentials / Q000187:drug effects; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D009474:Neurons / Q000187:drug effects; D015221:Potassium Channels / Q000187:drug effects; D051381:Rats; D013569:Synapses / Q000187:drug effects*; D009435:Synaptic Transmission / Q000187:drug effects
D015221:Potassium Channels; D001464:Barium; D000241:Adenosine