6533b82efe1ef96bd12925ce

RESEARCH PRODUCT

Evidence that ATP or a related purine is an excitatory neurotransmitter in the longitudinal muscle of mouse distal colon

subject

description

Background and purpose: This study analysed the contribution of the purinergic system to enteric neurotransmission in the longitudinal muscle of mouse distal colon. Experimental approach: Motor responses to exogenous ATP and to nerve stimulation in vitro were assessed as changes in isometric tension. Key results: ATP induced a concentration-dependent contraction, reduced by 4-[[4-formyl-5-hydroxy-6-methyl-3-[(phosphonooxy)methyl]-2-pyridinyl]azo]-1,3-benzene disulphonic acid (PPADS), suramin, P2Y purinoreceptor desensitisation with adenosine 5’-O-2-thiodiphosphate (ADPβS), and atropine, but unaffected by P2X purinoceptor desensitisation with α,β-methylene ATP (α,β-meATP) and by 2,2-dimethyl-propionic acid 3-(2-chloro-6-methylaminopurin-9-yl)-2-(2,2-dimethyl-propionyloxymethyl)-propyl ester (MRS 2395), a P2Y12 selective antagonist. The response to ATP was increased by 2′-deoxy-N6-methyl adenosine 3′,5′-diphosphate (MRS 2179), a P2Y1 selective antagonist, tetrodotoxin (TTX) or Nω-nitro-L-arginine methyl ester (L-NAME). ADPβS, a P2Y-purinergic agonist, induced muscular contraction, with the same pharmacological profile as the ATP-induced contraction. ADP, a natural ligand for P2Y1 receptors, induced muscular relaxation, antagonized by MRS 2179 and by TTX or L-NAME. Nerve stimulation elicited a transient nitrergic relaxation, followed by contraction. Contractile responses was reduced by atropine, PPADS, suramin, P2Y purinoceptor desensitisation, but not by P2X purinoceptor desensitisation, MRS 2179 or MRS 2395. None of the purinergic antagonists modified the nerve-evoked relaxation. Conclusions and implications: In the longitudinal muscle of mouse distal colon, ATP, through ADPβS-sensitive P2Y purinoceptors, contributed to the excitatory neurotransmission acting directly on smooth muscle and indirectly via activation of cholinergic neurons. Moreover, P2Y1 purinoceptors appear to be located on nitrergic inhibitory neurons. This study provides new insights into the role of purines in the mechanism inducing intestinal transit in mouse colon. British Journal of Pharmacology (2007) 151, 152–160. doi:10.1038/sj.bjp.0707188