Excitation and inhibition via adenosine receptors of the twitch response to electrical stimulation in isolated guinea pig ileum.
The effects of adenosine and its related compounds on the cholinergic twitch response were examined in electrically stimulated guinea pig ileum. Adenosine (3 x 10(-7)-10(-5) M) and an adenosine A1-receptor agonist N6-cyclohexyladenosine (CHA, 10(-8)-10(-6) M) suppressed the twitch. Conversely, the A2a-receptor agonist 2-[p-(2-carboxyethyl)phenethylamino]-5'-N- ethylcarboxamidoadenosine (CGS 21680, 10(-9)-10(-7) M) potentiated the twitch in half the preparations examined. The A1-antagonist 1,3-dipropyl-8-cyclopentylxanthine (DPCPX), which per se did not affect the twitch, recovered the attenuated twitch caused by CHA (10(-7) M) or adenosine (10(-6) M) and converted it into a potentiated twitch. These results suggest the presence of adenosine A1- and A2a-receptors coupled negatively and positively, respectively, to acetylcholine release in the preparation.
Tomaru
A
A
Department of Pharmacology, Kyowa Hakko Kogyo Co., Ltd., Shizuoka, Japan.
Ina
Y
Y
Kishibayashi
N
N
Karasawa
A
A
D000241:Adenosine / Q000494:pharmacology*; D000818:Animals; D002799:Cholinergic Fibers / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D006168:Guinea Pigs; D007082:Ileum / Q000187:drug effects* / Q000502:physiology*; D008297:Male; D018047:Receptors, Purinergic P1 / Q000187:drug effects; D014970:Xanthines / Q000494:pharmacology
D018047:Receptors, Purinergic P1; D014970:Xanthines; D000241:Adenosine