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Differential modulation of evoked and spontaneous glycine release from rat spinal cord glycinergic terminals by the cyclic AMP/protein kinase A transduction cascade
Author(s) -
Katsurabayashi Shutaro,
Kubota Hisahiko,
Moorhouse Andrew J.,
Akaike Norio
Publication year - 2004
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.2004.02741.x
Subject(s) - ibmx , inhibitory postsynaptic potential , protein kinase a , biophysics , chemistry , forskolin , patch clamp , glycine receptor , phosphodiesterase inhibitor , neurotransmission , glycine , neuroscience , biology , biochemistry , phosphorylation , receptor , amino acid
The mechanisms underlying cyclic AMP modulation of action potential‐dependent and ‐independent (spontaneous) release of glycine from terminals synapsing onto sacral dorsal commissural nucleus neurons of lamina X were studied in spinal cord slices using conventional patch‐clamp recordings. 3‐Isobutyl‐1‐methylxanthine (IBMX), a phosphodiesterase inhibitor, and forskolin increased the amplitude of evoked inhibitory postsynaptic currents (eIPSCs) in a sensitive manner to protein kinase A (PKA) inhibition (with KT‐5720). Direct activation (with adenosine 3′,5′‐cyclic‐monophosphothioate, Sp‐isomer) and inhibition (with adenosine 3′,5′‐cyclic‐monophosphothioate, Rp‐isomer) of PKA increased and decreased the eIPSC amplitude, respectively. Paired pulse experiments and direct injection of PKA inhibitor fragment 6–22 amide (PKI 6−22 ) into the recording neuron revealed that these effects on eIPSC amplitude occurred presynaptically, indicating that evoked glycine release is regulated by presynaptic cAMP via changes in PKA activity. Increasing cAMP also increased spontaneous release of glycine, causing an increased frequency of miniature IPSCs (mIPSCs). In contrast to the effects on evoked release, this response was not solely mediated via PKA, as it was not occluded by PKA inhibition, and both direct inhibition and direct activation of PKA actually enhanced mIPSC frequency. Direct inhibition of cAMP (with SQ 22536) did, however, reduce mIPSC frequency. These results suggest cAMP modulation of evoked and spontaneous release involves different presynaptic mechanisms and proteins.