Inhibition of spontaneous acetylcholine secretion by 2-chloroadenosine as revealed by a protein kinase inhibitor at the mouse neuromuscular junction.
1. Previous studies have reported discrepancies in the potencies of A(1) adenosine receptor agonists at mouse motor nerve terminals. In addition, conflicting results on the role of protein kinase A (PKA) in mediating the inhibitory effects of A(1) receptor agonists have been published. We thus decided to investigate the possibility of endogenous control of adenosine receptor sensitivity by protein kinases, using a variety of protein kinase inhibitors in conjunction with the adenosine receptor agonist 2-chloroadenosine (CADO). 2. CADO, at the concentration employed previously to study spontaneous ACh release in the mouse (1 microM), did not inhibit spontaneous ACh release in our experiments. However, a higher concentration of CADO (10 microM) produced highly statistically-significant reductions in spontaneous ACh release. 3. In the presence of the non-selective protein kinase inhibitor, H7 (50 microM), the potency of CADO was increased such that 1 microM CADO now reduced spontaneous quantal ACh release to approximately 63% of control. 4. Both H7, and the selective PKA inhibitor, KT5720 (500 nM) prevented increases in ACh release produced by CPT cyclic AMP (250 microM), suggesting these kinase inhibitors were blocking PKA. In contrast to H7, however, KT5720, did not reveal an inhibitory effect of 1 microM CADO. A number of other non-selective PKA inhibitors also failed to increase the potency of CADO. 5. The results suggest that an endogenous H7-sensitive process modulates the sensitivity of the mouse A(1) adenosine receptor and that the inhibitory effects of CADO are independent of cyclic AMP accumulation or PKA inhibition.
Hirsh
Jody K
JK
Molecular Pharmacology and Biological Chemistry S-215, Northwestern University Medical School, 303 E. Chicago Avenue, Chicago, Illinois 60611, USA.
Silinsky
Eugene M
EM
D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine / Q000494:pharmacology; D015762:2-Chloroadenosine / Q000494:pharmacology*; D000109:Acetylcholine / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D000818:Animals; D002227:Carbazoles; D002352:Carrier Proteins / Q000494:pharmacology*; D002463:Cell Membrane Permeability / Q000187:drug effects; D000242:Cyclic AMP / Q000031:analogs & derivatives* / Q000037:antagonists & inhibitors / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D007211:Indoles / Q000494:pharmacology; D047908:Intracellular Signaling Peptides and Proteins; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D009469:Neuromuscular Junction / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D058906:Purinergic P1 Receptor Agonists; D058915:Purinergic P1 Receptor Antagonists; D011758:Pyrroles / Q000494:pharmacology; D019311:Staurosporine / Q000494:pharmacology; D013873:Thionucleotides / Q000037:antagonists & inhibitors / Q000494:pharmacology
D002227:Carbazoles; D002352:Carrier Proteins; D004791:Enzyme Inhibitors; D007211:Indoles; D047908:Intracellular Signaling Peptides and Proteins; D058906:Purinergic P1 Receptor Agonists; D058915:Purinergic P1 Receptor Antagonists; D011758:Pyrroles; D013873:Thionucleotides; C015482:protein kinase modulator; D015762:2-Chloroadenosine; C015929:8-((4-chlorophenyl)thio)cyclic-3',5'-AMP; C057416:KT 5720; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D019311:Staurosporine; D000109:Acetylcholine