Premium
Effect of adenosine on bicuculline‐resistant paired‐pulse inhibition in the rat hippocampal slice
Author(s) -
Higgins Michael J.,
Stone Trevor W.
Publication year - 1995
Publication title -
hippocampus
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.767
H-Index - 155
eISSN - 1098-1063
pISSN - 1050-9631
DOI - 10.1002/hipo.450050307
Subject(s) - adenosine , bicuculline , chemistry , excitatory postsynaptic potential , neuroscience , adenosine a1 receptor , adenosine receptor , cgs 21680 , hippocampal formation , pulse (music) , biophysics , antagonist , receptor , agonist , biochemistry , biology , physics , detector , optics
This study extends previous investigations into the effect of adenosine on bicuculline‐resistant paired‐pulse inhibition between field potentials evoked 300 ms apart in the CA1 area of the rat hippocampal slice. A direct assessment of the effect of adenosine on paired‐pulse inhibition is complicated by the facts that adenosine directly depresses evoked potentials and bicuculline‐resistant paired‐pulse inhibition is greather between pairs of small potentials than between pairs of larger potentials. Adenosine increased biculline‐resistant paired‐pulse inhibition when stimulus strength was constant between adenosine and control but paired‐pulse inhibition of responses in adenosine was markedly less than paired‐pulse inhibition of control responses of the same size. Futhermore, adenosine decreased the size of conditioned potentials to a significantly lesser extent than unparired potentials of the same initial size. Taken together the results indicate that adenosine can decrease bicuculline‐resistant paired‐pulse inhibition in the hippocampus. A possible mechanism for this effect is that adenosine is suppressing transmission at excitatory terminals onto interneurones which would suggest that these receptors are more sensitive to adenosine than those on the Schaffer collateral/CA1 pyramidal cell synapses. In this case adenosin should reduce paired‐pulse inhibition at lower concentrations than are required for depression of single evoked potentials. A comparison of the concentration‐response relationships for the effects of adenosine on paired‐pulse inhibition and on single evoked potentials ruled out greater sensitivity of adenosine receptors at excitatory terminals onto interneurones as an explanation for adenosine's action on bicuculline‐resistant paired‐pulse inhibition. Adenosine was less effective at reducing inhibition evoked by large supramaximal conditioning stimuli than by submaximal for evoked potential size, although control paired‐pulse inhibiton is larger in the later case. This finding is consistent with adenosine reducing bicuculline‐resistant paired‐pulse inhibition by causing an increase in simultaneous paired‐pulse facilitation. © 1995 Wiley‐Liss, Inc.