Adenosine enhances afterhyperpolarization and accommodation in hippocampal pyramidal cells.
Adenosine added to the perfusion fluid of rat hippocampal slices at 10 mumol X l-1 enhanced long lasting afterhyperpolarizations after single action potentials, bursts of action potentials or calcium spikes. Accommodation of firing during a depolarizing pulse was potentiated. An increase in calcium dependent potassium conductance is likely to mediate these effects. Adenosine at 50 mumol X l-1 induced a hyperpolarization accompanied by a reduction in input resistance. The hyperpolarization could be reversed at -85 mV. In TTX and TTX-barium treated slices the amplitude of the slow spike was decreased. This may result from a shunting of inward current in the dendrites due to an adenosine induced increase in potassium conductance. It is suggested that adenosine reduces pre- and postsynaptic excitatory signals principally by enhancing one or more potassium conductances. This effect is a powerful means for modulation of neuronal excitability and synaptic efficacy and can explain the antiepileptic activity of adenosine.
D000241:Adenosine / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000502:physiology; D046508:Culture Techniques; D003712:Dendrites / Q000187:drug effects; D004558:Electric Stimulation; D006624:Hippocampus / Q000187:drug effects*; D007473:Ion Channels / Q000187:drug effects; D008564:Membrane Potentials / Q000187:drug effects; D009474:Neurons / Q000187:drug effects; D051381:Rats; D011919:Rats, Inbred Strains; D013569:Synapses / Q000187:drug effects; D009435:Synaptic Transmission / Q000187:drug effects*; D013779:Tetrodotoxin / Q000494:pharmacology
D007473:Ion Channels; D013779:Tetrodotoxin; D000241:Adenosine; D002118:Calcium