title: Adaptive changes in withdrawal reflexes after noxious stimulation at the heel and the toes in the decerebrated rabbit.
abstract: In decerebrated rabbits, reflexes evoked by electrical stimulation of the toes in the ankle flexor tibialis anterior were enhanced for > 30 min after application of 20% mustard oil to the base of the toes, whereas responses of the ankle extensor medial gastrocnemius to stimulation of the heel were depressed for > 20 min by the same stimulus. Applied to the heel, mustard oil had inconsistent effects on the flexor reflex but potentiated the extensor response for approximately 1 h. Intrathecal co-administration of naloxone (25 microg) with the selective alpha(2)-adrenoceptor antagonist RX 821002 (200 microg) enhanced both reflexes to more than twice pre-drug values and reduced or abolished all effects of mustard oil. These data confirm that the location of a noxious stimulus is an important determinant of the subsequent adaptive changes in reflexes, and indicate roles for endogenous opioids and noradrenaline in these processes.
authors.affiliation: Division of Animal Physiology, School of Biosciences, Sutton Bonington Campus, LE12 5RD, Loughborough, UK. robert.clarke@Nottingham.ac.uk
authors.forename: R W
authors.initials: RW
authors.lastname: Clarke
authors.forename: B E
authors.initials: BE
authors.lastname: Wych
authors.forename: J
authors.initials: J
authors.lastname: Harris
mesh_terms: D000222:Adaptation, Physiological / Q000187:drug effects* / Q000502:physiology; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology*; D000818:Animals; D003655:Decerebrate State; D004558:Electric Stimulation; D005260:Female; D006365:Heel / Q000502:physiology; D008297:Male; D009150:Mustard Compounds / Q000494:pharmacology*; D009270:Naloxone / Q000494:pharmacology*; D009292:Narcotic Antagonists / Q000494:pharmacology*; D011817:Rabbits; D012021:Reflex, Abnormal / Q000187:drug effects* / Q000502:physiology; D013268:Stimulation, Chemical; D014034:Toes / Q000502:physiology
chemical_list: D000317:Adrenergic alpha-Antagonists; D009150:Mustard Compounds; D009292:Narcotic Antagonists; D009270:Naloxone