Muscle stretch increased interstitial ATP by 68% and norepinephrine by 45% (P<0.05), a response that was blunted by P2X receptor antagonism.
Does elevated interstitial ATP stimulate P2X receptors and increase interstitial norepinephrine concentrations in active skeletal muscle?
ATP released by skeletal muscle during stretch stimulates P2X receptors on sympathetic nerves, increasing interstitial norepinephrine concentrations.
p-value: p=<0.05
BACKGROUND: Sympathetic nervous system activity increases with exercise in normal subjects. Heightened peripheral sympathetic nervous activity and the resultant increased neurovascular levels of norepinephrine (NE) evoke vasoconstriction and serve to maintain blood pressure and perfusion to vital organs. Previous work demonstrated that the interstitial ATP concentrations (ATPi) rise in contracting skeletal muscle, and it is known that sympathetic nerves have purinergic P2X receptors. Thus, in this report we tested the hypothesis that elevated ATP would stimulate these receptors and increase interstitial NE concentrations (NEi). METHODS AND RESULTS: Muscle interstitial samples were collected from microdialysis probes inserted in the skeletal muscle of rats, and dialysate concentrations of ATP and NE were determined by the high-performance liquid chromatography method. Stretch (0.5 kg of tension) increased ATPi by 68% (P<0.05) and NEi by 45% (P<0.05) in active muscle. The rise in NEi was linearly linked to the elevated ATPi (r=0.878, P<0.001). NEi was also elevated by 76% (P<0.05) after ATP (3 micromol/L) was injected into the arterial blood supply of the hindlimb muscles. The NEi response to muscle stretch was blunted after the P2X receptor antagonist pyridoxal phosphate-6-azophenyl-2',4'-disulfonic acid (PPADS) was given. Finally, this response was potentiated by the nucleotidase inhibitor 6-N,N-diethyl-beta-gamma-dibromomethylene-D-adenosine-5'-triphosphate (ARL67156). CONCLUSIONS: ATPi released by skeletal muscle during stretch stimulates P2X receptors on the sympathetic nerves and increases the concentration of NEi in the muscle interstitium.
Li et al. (Tue,) reported a other. Muscle stretch and ATP injection vs. Baseline/resting state was evaluated on Interstitial norepinephrine concentration ([NE]i) (p=<0.05). Muscle stretch increased interstitial ATP by 68% and norepinephrine by 45% (P<0.05), a response that was blunted by P2X receptor antagonism.