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KMID : 0360419940300010029
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Korean Journal of Pharmacology
1994 Volume.30 No. 1 p.29 ~ p.37
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Effects of Locus Coeruleus/Subcoeruleus Stimulation on the Tail Flick Reflex and Efflux of Noradrenaline into the Spinal Cord Superfusates
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Park Kyung-Pyo
Kim Jong-Sung
Suh Dae-Chul
Park Hyoung-Sup
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Abstract
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Inhibition of the nociceptive Tail Flick Reflex (TFR) was observed with electrical stimulation of the locus coeruleus/subcoeruleus (LC/SC) in the male Sprague - Dawley rats under light anesthesia, and the involved neurotransmitter (s) were characterized. Electrical stimulation of LC/SC induced the analgesia with the stimulation threshold (intensity of the current, given for 100 usec and in 100 Hz frequency, which caused the TF latency longer than 6.5 sec) around 55 uA. Intrathecal administrations of antagonist, yohimbine (30 ug) or opioid antagonist, naloxone (20 ug) increased the stimulation threshold by 147% and 123% respectively (from 55 uA to 135 uA,9 and from 54 uA to 123 uA;P0.01, n=5, each). The basal TF latency without stimulation (3.1 sec) was reduced by the antagonists (to 2.5 sec by yohimbine, p<0.05, n=5; to 2.6 sec by naloxone, p<0.1, n=5), vehicle only did not show any effect. Noradrenaline(NA) in the spinal cord superfusates measured with HPLC was increased by the LC/SC stimulation, from 4.18 ng/ml before to 7.74 ng/ml after stimulation (P<0.05, n=10). The result suggest that analgesia induced by LC/SC stimulation is mediated, at least in part, by the noradrenergic system in which receptor is involved, as well as the opioid system.
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KEYWORD
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Locus coeruleus/subcoeruleus, Electrical stimulation, Tail Flick Reflex, Noradrenaline
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