Interactions between adenosine and K+ channel-related pathways in the coupling of somatosensory activation and pial arteriolar dilation.
Multiple, perhaps interactive, mechanisms participate in the linkage between increased neural activity and cerebral vasodilation. In the present study, we assessed whether neural activation-related pial arteriolar dilation (PAD) involved interactions among adenosine (Ado) A(2) receptors (A(2)Rs), large-conductance Ca(2+)-operated K(+) (BK(Ca)) channels, and inward rectifier K(+) (K(ir)) channels. In rats with closed cranial windows, we monitored sciatic nerve stimulation (SNS)-induced PAD in the absence or presence of pharmacological blockade of A(2)Rs (ZM-241385), ecto-5'-nucleotidase (α,β-methylene-adenosine diphosphate), BK(Ca) channels (paxilline), and K(ir) channels (BaCl(2)). Individually, these interventions led to 53-66% reductions in SNS-induced PADs. Combined applications of these blockers led to little or no further repression of SNS-induced PADs, suggesting interactions among A(2)Rs and K(+) channels. In the absence of SNS, BaCl(2) blockade of K(ir) channels produced 52-80% reductions in Ado and NS-1619 (BK(Ca) channel activator)-induced PADs. In contrast, paxilline blockade of BK(Ca) channels was without effect on dilations elicited by KCl (K(ir) channel activator) and Ado suffusions, indicating that Ado- and NS-1619-associated PADs involved K(ir) channels. In addition, targeted ablation of the superficial glia limitans was associated with a selective 60-80% loss of NS-1619 responses, suggesting that the BK(Ca) channel participation (and paxilline sensitivity) derived largely from channels within the glia limitans. Additionally, blockade of either PKA or adenylyl cyclase caused markedly attenuated pial arteriolar responses to SNS and, in the absence of SNS, responses to Ado, KCl, and NS-1619. These findings suggested a key, possibly permissive, role for A(2)R-linked cAMP generation and PKA-induced K(+) channel phosphorylation in somatosensory activation-evoked PAD.
Paisansathan
Chanannait
C
Neuroanesthesia Research Laboratory, University of Illinois at Chicago, Chicago, Illinois 60612, USA.
Xu
Haoliang
H
Vetri
Francesco
F
Hernandez
Moises
M
Pelligrino
Dale A
DA
D000241:Adenosine / Q000378:metabolism*; D000067956:Adenylyl Cyclase Inhibitors; D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D001160:Arterioles / Q000294:innervation / Q000378:metabolism; D001253:Astrocytes / Q000378:metabolism; D020013:Calcium Signaling; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D015640:Ion Channel Gating; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; D010766:Phosphorylation; D010841:Pia Mater / Q000098:blood supply*; D026902:Potassium Channel Blockers / Q000494:pharmacology; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism*; D024661:Potassium Channels, Inwardly Rectifying / Q000037:antagonists & inhibitors / Q000378:metabolism*; D058915:Purinergic P1 Receptor Antagonists / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D043683:Receptors, Adenosine A2 / Q000187:drug effects / Q000378:metabolism*; D012584:Sciatic Nerve / Q000502:physiology; D015290:Second Messenger Systems; D015398:Signal Transduction / Q000187:drug effects; D013003:Somatosensory Cortex / Q000502:physiology*; D009435:Synaptic Transmission; D014664:Vasodilation / Q000187:drug effects; D014665:Vasodilator Agents / Q000494:pharmacology
D000067956:Adenylyl Cyclase Inhibitors; D004791:Enzyme Inhibitors; C494842:Kcnma1 protein, rat; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D058915:Purinergic P1 Receptor Antagonists; D043683:Receptors, Adenosine A2; D014665:Vasodilator Agents; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D000262:Adenylyl Cyclases; D000241:Adenosine