Adenosine modulates the excitability of layer II stellate neurons in entorhinal cortex through A1 receptors.
Stellate neurons in layer II entorhinal cortex (EC) provide the main output from the EC to the hippocampus. It is believed that adenosine plays a crucial role in neuronal excitability and synaptic transmission in the CNS, however, the function of adenosine in the EC is still elusive. Here, the data reported showed that adenosine hyperpolarized stellate neurons in a concentration-dependent manner, accompanied by a decrease in firing frequency. This effect corresponded to the inhibition of the hyperpolarization-activated, cation nonselective (HCN) channels. Surprisingly, the adenosine-induced inhibition was blocked by 3 μM 8-cyclopentyl-1,3-dipropylxanthine (DPCPX), a selective A(1) receptor antagonists, but not by 10 μM 3,7-dimethyl-1-propargylxanthine (DMPX), a selective A(2) receptor antagonists, indicating that activation of adenosine A(1) receptors were responsible for the direct inhibition. In addition, adenosine reduced the frequency but not the amplitude of miniature EPSCs and IPSCs, suggesting that the global depression of glutamatergic and GABAergic transmission is mediated by a decrease in glutamate and GABA release, respectively. Again the presynaptic site of action was mediated by adenosine A(1) receptors. Furthermore, inhibition of spontaneous glutamate and GABA release by adenosine A(1) receptor activation was mediated by voltage-dependent Ca(2+) channels and extracellular Ca(2+) . Therefore, these findings revealed direct and indirect mechanisms by which activation of adenosine A(1) receptors on the cell bodies of stellate neurons and on the presynaptic terminals could regulate the excitability of these neurons.
Li
Yang
Y
Department of Physiology, Third Military Medical University, Chongqing, China.
Fan
Shuangyi
S
Yan
Jie
J
Li
Bo
B
Chen
Fang
F
Xia
Jianxia
J
Yu
Zhengping
Z
Hu
Zhian
Z
D000241:Adenosine / Q000378:metabolism / Q000494:pharmacology; D058916:Adenosine A1 Receptor Antagonists / Q000494:pharmacology; D058917:Adenosine A2 Receptor Antagonists / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000378:metabolism; D018728:Entorhinal Cortex / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D019706:Excitatory Postsynaptic Potentials / Q000502:physiology; D018698:Glutamic Acid / Q000378:metabolism; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D009924:Organ Culture Techniques; D018408:Patch-Clamp Techniques; D017729:Presynaptic Terminals / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D043682:Receptor, Adenosine A1 / Q000187:drug effects / Q000378:metabolism*; D043683:Receptors, Adenosine A2 / Q000187:drug effects / Q000378:metabolism; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology*; D013805:Theobromine / Q000031:analogs & derivatives / Q000494:pharmacology; D014970:Xanthines / Q000494:pharmacology; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
D058916:Adenosine A1 Receptor Antagonists; D058917:Adenosine A2 Receptor Antagonists; D015220:Calcium Channels; D043682:Receptor, Adenosine A1; D043683:Receptors, Adenosine A2; D014970:Xanthines; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid; C057837:3,7-dimethyl-1-propargylxanthine; C051360:1,3-dipropyl-8-cyclopentylxanthine; D000241:Adenosine; D013805:Theobromine; D002118:Calcium