Journal
SYNAPSE
Volume 65, Issue 12, Pages 1282-1288Publisher
WILEY
DOI: 10.1002/syn.20948
Keywords
DA release; NA; microdialysis; locomotor activity; spinal stereotaxic implantation
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Funding
- NIH [R01NS023868, 5R25GM059218-07, Pilot-5G11HD039879-06]
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Dopamine (DA) and noradrenaline (NA) modulate responses to nociceptive stimuli, within the dorsal horn of the spinal cord. Both neurotransmitters may play a role in supraspinal regulation in response to proprioceptive afferences to the dorsal horn. However, direct evidence of changes in neurotransmitter release within the dorsal horn due to non-noxious stimuli is lacking. The present study was designed to determine, whether non-nociceptive exercise produces changes in release of DA and NA within the dorsal horn, and whether these changes are associated with long-lasting inhibition after the exercise stops. Microdialysis probes, implanted in layers 2-5 of Rexed, in combination with high-performance liquid chromatography coupled to electrochemical detection (HPLC-EC) were used to measure concentrations of DA and NA metabolite (MHPG) in lumbar spinal cords of rats. Microdialysate was sampled before, during, and after a treadmill exercise of one hour. Results indicate that DA and NA releases are inhibited during non-nociceptive motor activity. At rest, DA concentration was 204 +/- 10.5 pg/10 mu l and was significantly decreased during exercise to -11.4% (P < 0.05). Greater decrease occurred after 30 min of exercise and was of -31.4% (P <= 0.05). Similarly, MHPG was significantly decreased of -18% during exercise (P <= 0.05). When exercise stopped, both systems showed long-lasting inhibition. Exercise post-release lasted 30 min for DA and 90 min for MHPG. MHPG greatest decrease of -47.8% occurred 30 min after stopping the exercise (P <= 0.001). Thus, DA and NA systems seem to respond to exercise-induced proprioceptive afferent stimuli to the dorsal horn. Synapse 65:1282-1288, 2011. (C) 2011 Wiley-Liss, Inc.
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