Hyperalgesia during sedation: effects of barbiturates and propofol in the rat

Ewen, Alastair; Archer, David P.; Samanani, Naaznin; Roth, Sheldon H.

doi:10.1007/bf03011694

Cited by 54 publications

(31 citation statements)

References 19 publications

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“…13 Our findings do not explain the conflicting results obtained in human studies of the effects of subhypnotic effects of thiopental on the response to painful stimulation. 2,17 The present results differ from our findings concerning the facilitation of synaptic transmission in the hippocampus by pentobarbital.…”

Section: Discussioncontrasting

confidence: 84%

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Pentobarbital induces nocifensive hyperrflexia, not hyperalgesia in rats

Archer

Samanani

Roth

2000

Can J Anesth/J Can Anesth

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Purpose: To seek behavioural, reflexive and histochemical evidence of long-lasting changes in nociceptive stimulus transmission induced by exposure to doses of pentobarbital that induce nocifensive hyperreflexia.Methods: Nocifensive hyperreflexia was induced in 12 rats with 30 mg·kg -1 pentobarbital ip. Reflex latency times for withdrawal of the hind paw from noxious radiant heat were measured with an automated electronic timer. Subjective responses to noxious stimulation (licking or biting of the stimulated hindpaw) and the level of sedation were recorded. Histological sections of lumbar spinal cord were stained for immunoreactivity of the immediateearly-gene (IEG), c-fos, in three rats that received repeated threshold noxious radiant heat stimulation during the period of nocifensive hyperreflexia induced by 30 mg·kg -1 pentobarbital ip.Results: Reflex withdrawal latency decreased by 32 ± 8% of control values (P < 0.001) following pentobarbital injection and returned to control values 120 min after drug injection. Once fully alert, pentobarbital-treated animals did not show any increase in nociceptive behaviour relative to saline-injected controls (P = 0.41). Sustained noxious stimulation to the hindpaw in halothane-anesthetized animals was associated with an increase in c-fos immunoreactivity in the dorsal horn of the lumbar spinal cord ipsilateral to the stimulation (P < 0.001). Threshold stimulation in the pentobarbital-treated animals was not associated with any increase in c-fos expression.Conclusions: During pentobarbital-induced hyperreflexia, rats did not show any reflexive, behavioural, or histochemical evidence of long-lasting enhancement of nocifensive signal transmission. The results are consistent with previous observations that, in the absence of tissue injury, nocifensive hyperreflexia induced by barbiturates is a short-lived pharmacological effect.Objectif : Découvrir les manifestations comportementales, réflexes et histochimiques de modifications persistantes de la transmission d'un stimulus nociceptif induit par l'exposition à des doses de pentobarbital qui provoquent une surréflectivité défensive.Méthode : La surréflectivité défensive a été induite chez 12 rats avec 30 mg·kg -1 de pentobarbital ip. Les temps de latence réflexe nécessaire au retrait de la patte arrière d'une source de chaleur radiante ont été mesurés avec un chronomètre électronique automatisé. Les réponses subjectives à la stimulation désagréable (lécher ou mordre la patte stimulée) et le niveau de sédation ont été enregistrés. Des sections histologiques de la moelle épinière lombaire ont été colorées pour vérifier l'immunoréactivité du gène précoce immédiat (GPI), c-fos, chez trois rats qui ont reçu une stimulation liminale nocive répétée de chaleur radiante pendant la période de surréflectivité défensive induite par les 30 mg·kg -1 de pentobarbital ip.Résultats : Le temps de latence réflexe a baissé de 32 ± 8 % par rapport aux valeurs témoins (P < 0,001) après l'injection de pentobarbital et est revenu aux valeurs témoins 1...

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Section: Discussioncontrasting

confidence: 84%

“…13 Power analysis predicted that such differences could reliably be detected with groups of 3-5 animals. We were concerned that behavioural measures would show a greater variability and therefore increased the group size to 12 in anticipation of this potential problem.…”

Section: Sample Size and Data Analysismentioning

confidence: 99%

Pentobarbital induces nocifensive hyperrflexia, not hyperalgesia in rats

Archer

Samanani

Roth

2000

Can J Anesth/J Can Anesth

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“…Thus, questions arise as to whether the processing of sensory inputs in the SC is also under the control of the hypothesized excitation/inhibition balance and whether facilitation can result from altering such balance with anesthetics. Low levels of volatile and intravenous anesthetics facilitate synaptic transmission (Archer et al, 2001) and responses to somatic pain (Dundee, 1960;Arora et al, 1972;Briggs et al, 1982;Ewen et al, 1995;Zhang et al, 2000).…”

Section: Introductionmentioning

confidence: 99%

Anesthetics Change the Excitation/Inhibition Balance That Governs Sensory Processing in the Cat Superior Colliculus

Populin

2005

J. Neurosci.

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The superior colliculus (SC) is a midbrain structure that plays a central role in the integration of information from different sensory modalities and the generation of orienting responses. Its normal function is thought to be governed by a strictly held balance between excitation and inhibition. This hypothesis was tested by recording from the same single units in the SC of cats before the injection of anesthetics, while anesthetics took effect, and after the injections during recovery. Sodium pentobarbital and ketamine, two agents commonly used in sensory physiology, were used. The results show a plethora of dose-dependent and nonlinear effects: the magnitude of evoked responses, receptive field properties, first spike latency, and bimodal integration were affected by both anesthetics in all units tested. Notably, prominent facilitation was observed at low levels of anesthesia, and inhibitory responses were changed into excitatory. Overall, the results challenge a fundamental tenet of sensory physiology: anesthesia, while decreasing single-unit responsiveness, leaves unaltered basic physiological properties.

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“…From animal studies, we know that hyperreflexia occurs at subanesthetic concentrations of both fixed agents, such as barbiturates, 6,7 and volatile agents such as halothane. 8 It is believed that selective inhibition of descending inhibitory pathways by low concentrations of anesthetic agents raises the excitability of the motor neuron pool.…”

Section: Méthode : Dans Une éTude Clinique Randomisée Prospective Avmentioning

confidence: 99%

The ankle clonus test is not a clinically useful measure of spinal cord integrity in children

Ewen

Cox

Davies

et al. 2005

Can J Anesth/J Can Anesth

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P Pu ur rp po os se e: : Bilateral flexion-induced ankle clonus has been proposed as a test of spinal cord integrity during anesthesia for scoliosis surgery. The purpose of this study was to establish the reliability of this test in normal children emerging from volatile anesthesia. A secondary objective was to determine if there was a difference in the validity of this test with either sevoflurane or isoflurane anesthesia. M Me et th ho od ds s: :In a randomized, prospective blinded clinical trial, 32 healthy children aged three to 13 yr, were randomized to receive either isoflurane (Group I, n = 15) or sevoflurane (Group S, n = 17) for maintenance of anesthesia during dental restorative surgery. During emergence, an observer, blinded to group allocation, recorded ankle clonus scores (number of beats to a maximum of 5 on each side) at 60-sec intervals until tracheal extubation. End-tidal anesthetic concentration was measured contemporaneously.

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Hyperalgesia during sedation: effects of barbiturates and propofol in the rat

Cited by 54 publications

References 19 publications

Pentobarbital induces nocifensive hyperrflexia, not hyperalgesia in rats

Pentobarbital induces nocifensive hyperrflexia, not hyperalgesia in rats

Anesthetics Change the Excitation/Inhibition Balance That Governs Sensory Processing in the Cat Superior Colliculus

The ankle clonus test is not a clinically useful measure of spinal cord integrity in children

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