Search

There exists a pressing need for the identification of novel analgesics. We recently reported on a new preclinical assay for rapid analgesic screening based on intraplantar (i.pl.) injection of 10% hypertonic saline (HS) in female outbred (CD-1) mice. Herein, we characterized the HS assay’s performance in inbred (C57BL/6) mice, sensitivity to sex differences, and effects of diurnal rhythm phase. In randomized, controlled, blinded in vivo animal experiments, we studied nociceptive responses induced by i.pl. HS in C57BL/6 (vs CD-1) mice of both sexes (n = 240) and determined diurnal rhythm phase effects in female animals. We established the HS assay’s sensitivity to morphine by constructing dose-response curves and calculating half-maximal inhibitory doses (ID50s). The injection of i.pl. HS produced nociceptive (licking and biting) responses in all C57BL/6 mice tested. In both C57BL/6 and CD-1 mice, the mean (95% confidence interval [CI]) response magnitudes were greater in females vs males (C57BL/6: 87 sec [64 to 110] vs 45 sec [29 to 61]; difference in means, 42 sec; 95% CI, 17 to 68; P < 0.001; n = 10/group; CD-1: 110 sec [95 to 126] vs 53 sec [32 to 74]; difference in means, 57 sec; 95% CI, 34 to 79; P < 0.001; n = 10/group). The mean (95% CI) nociceptive responses were greater at 24:00 hr than at 12:00 hr in C57BL/6 mice (64 sec [40 to 88] vs 37 sec [24 to 51]; difference in means, 27 sec; 95% CI, 7 to 47; P = 0.007; n = 10/group), but not in CD-1 mice (P = 0.97). Intravenous morphine dose-dependently attenuated nociceptive responses of both C57BL/6 and CD-1 mice (ID50, 0.6 and 2.5 mg·kg−1, respectively; P = 0.41). These findings in inbred and outbred mice solidify the utility of the HS assay as an effective, rapid, robust, and versatile preclinical tool for analgesic screening.

Background Legalization of cannabis encourages the development of specific cultivars to treat disease such as neuropathic pain. Because of the large number of cultivars, it is necessary to prioritize extracts before proceeding to clinical trials. Purpose To compare extracts of two unique cannabis cultivars (CT-921, CT-928) for treatment of neuropathic pain induced by constriction of sciatic nerve in mice and to illustrate the use of this animal model to set priority for future trials. Methods Pain severity was measured by threshold force causing paw withdrawal. Dose-response relationships and time course were determined for intravenously injected extracts of cultivars and vehicle. The doses for allodynia relief were correlated with decreased respiratory rate, temperature and behavioral changes. Results Effective analgesic dose for 50 and 95% (ED50An and ED95An) was 15, and 29 mg/kg for CT-921 and 0.9 and 4.7 for CT-928. At ED50An, for both extracts, the duration was 120 min. At ED95An, administration of CT-928 significantly decreased respiratory rate while CT-921 did not. CT-928 decreased temperature more than CT-921. CT-928 produced frantic hyperactivity not seen with CT-921. At equivalent analgesic doses, THC was much less in CT-921 than in CT-928 suggesting interactions with components other than THC influenced the analgesia. At equivalent analgesic doses, efficacy-to-adverse effect profile for CT-928 was worse than for CT-921. Conclusion Both extracts relieved neuropathic pain; however, CT-921 had a better efficacy-to-adverse effect profile, a rational basis for prioritizing cultivars for future clinical evaluation.

There exists a pressing need for the identification of novel analgesics. We recently reported on a new preclinical assay for rapid analgesic screening based on intraplantar (i.pl.) injection of 10% hypertonic saline (HS) in female outbred (CD-1) mice. Herein, we characterized the HS assay's performance in inbred (C57BL/6) mice, sensitivity to sex differences, and effects of diurnal rhythm phase.In randomized, controlled, blinded in vivo animal experiments, we studied nociceptive responses induced by i.pl. HS in C57BL/6 (vs CD-1) mice of both sexes (n = 240) and determined diurnal rhythm phase effects in female animals. We established the HS assay's sensitivity to morphine by constructing dose-response curves and calculating half-maximal inhibitory doses (IDThe injection of i.pl. HS produced nociceptive (licking and biting) responses in all C57BL/6 mice tested. In both C57BL/6 and CD-1 mice, the mean (95% confidence interval [CI]) response magnitudes were greater in females vs males (C57BL/6: 87 sec [64 to 110] vs 45 sec [29 to 61]; difference in means, 42 sec; 95% CI, 17 to 68; P0.001; n = 10/group; CD-1: 110 sec [95 to 126] vs 53 sec [32 to 74]; difference in means, 57 sec; 95% CI, 34 to 79; P0.001; n = 10/group). The mean (95% CI) nociceptive responses were greater at 24:00 hr than at 12:00 hr in C57BL/6 mice (64 sec [40 to 88] vs 37 sec [24 to 51]; difference in means, 27 sec; 95% CI, 7 to 47; P = 0.007; n = 10/group), but not in CD-1 mice (P = 0.97). Intravenous morphine dose-dependently attenuated nociceptive responses of both C57BL/6 and CD-1 mice (IDThese findings in inbred and outbred mice solidify the utility of the HS assay as an effective, rapid, robust, and versatile preclinical tool for analgesic screening.RéSUMé: OBJECTIF: Il existe un besoin impérieux d’identification de nouveaux analgésiques. Nous avons récemment publié les conclusions d’un nouveau test préclinique portant sur le dépistage analgésique rapide basé sur l’injection intraplantaire (i.pl.) d’une solution saline hypertonique à 10 % (HS) chez des souris femelles croisées (CD-1). Dans notre présente étude, nous avons caractérisé la performance du test de HS chez des souris consanguines (C57BL/6), la sensibilité aux différences de sexe, et les effets des phases de rythme diurne. MéTHODE: Dans le cadre d’expériences animales in vivo en aveugle randomisées contrôlées, nous avons étudié les réponses nociceptives induites par une i.pl. de HS chez des souris C57BL/6 (vs CD-1) des deux sexes (n = 240) et déterminé les effets des phases du rythme diurne chez les animaux femelles. Nous avons établi la sensibilité du test HS à la morphine en construisant des courbes de dose-réponse et en calculant des doses inhibitrices semi-maximales (DI

Background Legalization of cannabis encourages the development of specific cultivars to treat disease such as neuropathic pain. Because of the large number of cultivars, it is necessary to prioritize extracts before proceeding to clinical trials. Purpose To compare extracts of two unique cannabis cultivars (CT-921, CT-928) for treatment of neuropathic pain induced by constriction of sciatic nerve in mice and to illustrate the use of this animal model to set priority for future trials. Methods Pain severity was measured by threshold force causing paw withdrawal. Dose–response relationships and time course were determined for intravenously injected extracts of cultivars and vehicle. The doses for allodynia relief were correlated with decreased respiratory rate, temperature and behavioral changes. Results Effective analgesic dose for 50 and 95% (ED50An and ED95An) was 15, and 29 mg/kg for CT-921 and 0.9 and 4.7 for CT-928. At ED50An, for both extracts, the duration was 120 min. At ED95An, administration of CT-928 significantly decreased respiratory rate while CT-921 did not. CT-928 decreased temperature more than CT-921. CT-928 produced frantic hyperactivity not seen with CT-921. At equivalent analgesic doses, THC was much less in CT-921 than in CT-928 suggesting interactions with components other than THC influenced the analgesia. At equivalent analgesic doses, efficacy-to-adverse effect profile for CT-928 was worse than for CT-921. Conclusion Both extracts relieved neuropathic pain; however, CT-921 had a better efficacy-to-adverse effect profile, a rational basis for prioritizing cultivars for future clinical evaluation.

Background RSD921, the R,R enantiomer of the kappa (k) agonist PD117,302, lacks significant activity on opioid receptors. Methods The pharmacological and toxicological actions were studied with reference to cardiovascular, cardiac, antiarrhythmic, toxic and local anaesthetic activity. Results In rats, dogs and baboons, RSD921 dose-dependently reduced blood pressure and heart rate. In a manner consistent with sodium channel blockade it prolonged the PR and QRS intervals of the ECG. Furthermore, in rats and NHP, RSD921 increased the threshold currents for induction of extra-systoles and ventricular fibrillation (VFt), and prolonged effective refractory period (ERP). In rats, RSD921 was protective against arrhythmias induced by electrical stimulation and coronary artery occlusion. Application of RSD921 to voltage-clamped rat cardiac myocytes blocked sodium currents. RSD921 also blocked transient (ito) and sustained (IKsus) outward potassium currents, albeit with reduced potency relative to sodium current blockade. Sodium channel blockade due to RSD921 in myocytes and isolated hearts was enhanced under ischaemic conditions (low pH and high extracellular potassium concentration). When tested on the cardiac, neuronal and skeletal muscle forms of sodium channels expressed in Xenopus laevis oocytes, RSD921 produced equipotent tonic block of sodium currents, enhanced channel block at reduced pH (6.4) and marked use-dependent block of the cardiac isoform. RSD921 had limited but quantifiable effects in subacute toxicology studies in rats and dogs. Pharmacokinetic analyses were performed in baboons. Plasma concentrations producing cardiac actions in vivo after intravenous administration of RSD921 were similar to the concentrations effective in the in vitro assays utilized. Conclusions RSD921 primarily blocks sodium currents, and possesses antiarrhythmic and local anaesthetic activity.

Background Neuraxial opioids are widely used for intraoperative and post-operative analgesia. The risk of severe adverse effects including respiratory depression accompanies this analgesia, prompting the need for effective non-opioid alternatives. Systemic 1-amino-1-cyclobutanecarboxylic acid showed promise in preliminary studies to produce antinociception without observable toxicity. However, the effects of 1-amino-1-cyclobutanecarboxylic acid after intrathecal administration are unknown. The aim of this study was to determine whether intrathecal administration of 1-amino-1-cyclobutanecarboxylic acid produces antinociceptive effects in murine models and to elucidate its site and receptor mechanism of action. Methods Female CD-1 mice were randomized to receive intrathecal, intraperitoneal and intraplantar injections of 1-amino-1-cyclobutanecarboxylic acid. Animals receiving intrathecal injections were anaesthetized and injected between L5 and L6. Animals then received an intraplantar injection of 10% hypertonic saline into the right hindpaw and were video-recorded for 30 min. Videos were analyzed by a blinded observer who determined the duration that animals exhibited nocifensive responses. Results Intrathecal or intraperitoneal administration of 1-amino-1-cyclobutanecarboxylic acid reduced the time that animals exhibited nocifensive behaviour, whereas intraplantar administration produced no effect. The effects of intrathecal 1-amino-1-cyclobutanecarboxylic acid were restricted in dermatomal distribution, reversible and produced little or no depression of respiratory rate. An NMDA antagonist blocked antinociception, while mu-opioid or GABAB antagonists did not prevent ACBC antinociception. Conclusions Intrathecal 1-amino-1-cyclobutanecarboxylic acid in mice produces robust, brief antinociceptive effects with a dermatomal distribution corresponding to the lumbar site of administration. This amino acid merits further exploration as a non-opioid neuraxial analgesic with little or no respiratory side effects. Significance The novel, non-opioid analgesic, 1-amino-1-cyclobutanecarboxylic acid, produced robust, reversible and localized antinociception in murine models of pain. This study provides evidence supporting further investigation and development of 1-amino-1-cyclobutanecarboxylic acid as a non-opioid spinal analgesic.

BACKGROUND Development of new analgesics is limited by shortcomings of existing preclinical screening assays such as wide variations in response, suitability for a narrow range of analgesics, and propensity to induce tissue damage. Our aim was to determine the feasibility of a new in vivo animal assay as an analgesic screen based on nociceptive responses (licking and biting) after intraplantar (i.pl.) injection of hypertonic saline (HS) in mice. METHODS With approval from the Institutional Animal Care Committee, we conducted a randomized, investigator-blinded in vivo study in adult CD-1 mice. We first studied the concentration-response relationship, time course, and sex difference of animals' nociceptive responses to HS. Subsequently, we assessed the screening ability of the HS assay to detect a range of established analgesics belonging to different classes. Finally, we performed histopathologic studies to assess potential tissue damage. RESULTS The response produced by i.pl. HS was greater and longer in female than in male mice. The responses to HS were concentration dependent with minimal variance. Ten percent HS evoked a maximal response within the first 5 minutes. Morphine dose-dependently attenuated animals' nociceptive responses (1-10 mg/kg intraperitoneally [i.p.]). The peripherally restricted µ-opioid receptor agonist, loperamide, reduced nociceptive responses when injected locally (30-100 µg/paw, i.pl.) but not systemically (1-10 mg/kg, i.p.). Acetylsalicylic acid (300 mg/kg, i.p.), naproxen (150 mg/kg, i.p), and acetaminophen (300 mg/kg, i.p.) all decreased nociceptive responses, as did i.pl. coinjections of lidocaine (0.003%-1%) with 10% HS. Histopathologic assessment revealed no tissue damage due to HS. CONCLUSIONS The i.pl. HS assay is easily performed, rapidly detects standard analgesics, and produces minimal animal suffering without tissue damage. We propose this assay as a useful addition to the armamentarium of existing preclinical analgesic screens.

Current centrally acting analgesics such as opioids are associated with adverse effects that limit their use and threaten patient safety. Isovaline is a novel prototype analgesic that produces peripheral antinociception in several pain models with little or no effect on the central nervous system. The aim of this study was to establish a preliminary structure-activity relationship for isovaline derivatives by assaying efficacy in the formalin foot assay and central adverse effect profile in mice. Selected compounds were tested using the formalin foot assay to determine efficacy in reducing formalin-induced behaviors. Of the compounds tested, R-isovaline, S-isovaline, and 1-amino-1-cyclobutanecarboxylic acid reduced nocifensive behavior in phase II of the assay. These effects occurred without affecting performance on the rotarod, indicating that the reduction in nocifensive behaviors was not due to sedation or motor incoordination. Modifications to isovaline that increased its steric size without a cyclobutane ring formation produced compounds with no activity in the formalin foot assay. These findings indicate that the conformational stability of isovaline or the ability to form a cyclobutane ring is necessary for activity in the formalin foot assay.

R-isovaline is a non-proteinogenic amino acid which produces analgesia in a range of nociceptive assays. Mediation of this effect by metabotropic receptors for γ-aminobutyric acid (GABA) and glutamate, demonstrated by previous work, may depend on the type of tissue or receptor system. The objective of this study was to assess the activity of R-isovaline acting at GABAB and group II metabotropic glutamate receptors in guinea pig ileum, which is known to exhibit well-defined responses to GABAB agonists such as baclofen. The effects of bath-applied R-isovaline and RS-baclofen were examined on electrically evoked contractions of guinea pig ileum and during GABAB antagonism by CGP52432. In separate experiments, the group II metabotropic glutamate receptor agonist, LY354740 was applied to determine the functional presence of these receptors. R-isovaline (1-100mM) decreased the amplitude of ileal muscle contractions and increased tension. RS-baclofen reduced contraction amplitude, but decreased tension. CGP52432 did not prevent the effects of R-isovaline on contraction amplitude, but antagonized effects of RS-baclofen on contraction amplitude. The group II metabotropic glutamate receptor agonist, LY354740, produced no detectable effects on evoked contractions. R-isovaline differed significantly from RS-baclofen in its actions in the guinea pig ileum, indicated in particular by the finding that CGP52432 blocked only the effects of RS-baclofen. The ileal tissue did not respond to a group II metabotropic glutamate receptor agonist, previously shown to co-mediate R-isovaline analgesia. These findings raise the possibility of a novel therapeutic target at unknown receptors for R-isovaline-like compounds in the guinea pig ileum.

BACKGROUND The combination of propofol and an opioid analgesic is widely used for procedural sedation, as well as total IV anesthesia. However, opioids produce respiratory depression, a primary cause of death due to these agents. We recently reported on the antinociceptive actions of isovaline, a small nonbiogenic amino acid that does not readily cross the blood-brain barrier and acts on peripheral γ-aminobutyric acid type B receptors. Here, we explored the possibility that isovaline may be an effective and safe alternative to opioids as an adjunct to propofol for producing anesthesia. METHODS With approval from our Animal Care Committee, we conducted an in vivo study in adult female CD-1 mice using Dixon's "up-and-down" method for dose assessment. Animals received intraperitoneal saline, propofol, isovaline, fentanyl, or coadministration of propofol with isovaline or fentanyl. We assessed hypnosis by a loss of righting reflex and immobility by an absence of motor response to tail clip application. General anesthesia was defined as the presence of both hypnosis and immobility. We assessed conscious sedation as a decrease in time on a rotarod. The maximal dose without respiratory rates of

BACKGROUND In vivo animal assays are a cornerstone of preclinical pain research. An optimal stimulus for determining the activity of potential analgesics would produce responses of a consistent magnitude on repeated testing. Intraplantar (i.pl.) injection of hypertonic saline (HS) in mice produces robust nociceptive responses to different analgesics, without evidence of tissue damage. Here, we investigated whether the nociceptive response is changed by repeating the injection at different times and sites in a mouse and whether it is attenuated by morphine. METHODS We conducted randomized and blinded experiments to assess responses to repeated i.pl. 10% HS in female CD-1 mice. An injection of HS was followed by a second injection into the same hind paw at 4 hours, 24 hours, or 7 days. A separate group of mice each received i.pl. injections at 5, 10, and 15 days. In 2 independent experiments, 30 minutes after initial HS injections in the ipsilateral hind paw, mice received HS injection into the contralateral hind paw or ipsilateral forepaw. The ability of morphine to block the nociceptive responses was examined by injecting morphine at 5-day intervals. RESULTS Repeated injection of HS did not alter the responses at 4 hours (84 vs 75 seconds; mean difference [95% CI], -9 [-40 to 23]; P = .6), 24 hours (122 vs 113 seconds; -6 [-24 to 12]; P = .5), or 7 days (112 vs 113 seconds; -0.3 [-12 to 11]; P = .95) or at multiple injections (day 0, 122 seconds vs day 5, 121 seconds; -0.3 [-28 to 27], P > .99; day 10, 118 seconds; 2.5 [-36 to 41], P = .99; day 15, 119 seconds; 2 [-36 to 38], P = .99). A previous hind paw injection did not change the responses of the contralateral hind paw (right, 93 seconds versus left, 96 seconds; -3 [-20 to 13], P = .7) or of the ipsilateral forepaw (forepaw after HS, 146 seconds versus forepaw after 0.9% saline, 149 seconds; -3 [-28 to 22], P = .8). Morphine dose-dependently attenuated HS responses (control, 94 seconds vs 4 mg/kg, 66 seconds; 29 [-7 to 64], P = .12; vs 10 mg/kg, 27 seconds; 67 [44-90], P < .0001; 4 vs 10 mg/kg, 67 [44-90], P = .03). CONCLUSIONS The repetition of i.pl. HS produces consistent reproducible responses without tissue damage. This results in efficient, rapid detection of analgesic activity, reducing the number of animals required.

R-isovaline is a non-proteinogenic amino acid which produces analgesia in a range of nociceptive assays. Mediation of this effect by metabotropic receptors for γ-aminobutyric acid (GABA) and glutamate, demonstrated by previous work, may depend on the type of tissue or receptor system. The objective of this study was to assess the activity of R-isovaline acting at GABA

Peripherally restricted analgesics are desirable to avoid central nervous system (CNS) side effects of opioids. Nonsteroidal anti-inflammatory drugs produce peripheral analgesia but have significant toxicity. GABA(B) receptors represent peripheral targets for analgesia but selective GABA(B) agonists like baclofen cross the blood-brain barrier. Recently, we found that the CNS-impermeant amino acid, isovaline, produces analgesia without apparent CNS effects. On observing that isovaline has GABA(B) activity in brain slices, we examined the hypothesis that isovaline produces peripheral analgesia mediated by GABA(B) receptors. We compared the peripheral analgesic and CNS effect profiles of isovaline, baclofen, and GABA (a CNS-impermeant, unselective GABA(B) agonist). All three amino acids attenuated allodynia induced by prostaglandin E2 injection into the mouse hindpaw and tested with von Frey filaments. The antiallodynic actions of isovaline, baclofen, and GABA were blocked by the GABA(B) antagonist, CGP52432, and potentiated by the GABA(B) modulator, CGP7930. We measured Behavioural Hyperactivity Scores and temperature change as indicators of GABAergic action in the CNS. ED(95) doses of isovaline and GABA produced no CNS effects while baclofen produced substantial sedation and hypothermia. In a mouse model of osteoarthritis, isovaline restored performance during forced exercise to baseline values. Immunohistochemical staining of cutaneous layers of the analgesic test site demonstrated co-localization of GABA(B1) and GABA(B2) receptor subunits on fine nerve endings and keratinocytes. Isovaline represents a new class of peripherally restricted analgesics without CNS effects, mediated by cutaneous GABA(B) receptors.

We recently showed that the quaternary lidocaine derivative, QX-314, produces long-lasting local anesthesia with a slow onset in animal models in vivo. As quaternary agents do not rapidly penetrate biological membranes or the blood-brain barrier, QX-314 may represent a local anesthetic with decreased systemic toxicity compared with conventional tertiary aminoamines. To test this hypothesis, we conducted an in vivo animal study in mice to compare QX-314 with lidocaine in terms of its relative central nervous system (CNS) and cardiac toxicity.With approval from the institutional Animal Care Committee, we used the "up-and-down" method to determine the relative potencies (ED(50)) of lidocaine and QX-314 for CNS and cardiac toxicity in adult CD-1 mice (weight, 20 to 35 g). The animals were administered either intravenous lidocaine or QX-314 (dose range, 7.5 to 30 mg·kg(-1)) and were observed for signs of CNS toxicity (convulsions, ataxia, loss of righting reflex, and/or death). We also observed animals for electrocardiographic evidence of toxic effects on cardiac automaticity, conductivity, and rhythmicity.The ED(50) of lidocaine for CNS toxicity as determined by the "up-and-down" method was 19.5 mg·kg(-1) (95% confidence interval [CI], 17.7 to 21.3 mg·kg(-1); n = 6) compared with 10.7 mg·kg(-1) for QX-314 (95% CI, 9.1 to 12.3 mg·kg(-1); n = 6) (potency ratio, 1.8). Similarly, the ED(50) of lidocaine for electrocardiographic evidence of cardiac toxicity was significantly higher than that of QX-314 (ED(50) of lidocaine, 21.2 mg·kg(-1); 95% CI, 19.0 to 23.4 mg·kg(-1); n = 6 vs ED(50) of QX-314, 10.6 mg·kg(-1); 95% CI, 8.4 to 12.8 mg·kg(-1); n = 6) (potency ratio, 2.0).In this in vivo animal study, the relative potencies of QX-314 for systemic CNS and cardiac toxicity were significantly higher than those of lidocaine. These data do not support the hypothesis that QX-314 is a safer local anesthetic compared with lidocaine in terms of systemic toxicity. Whereas our results do not exclude the possibility that QX-314 may represent a clinically useful agent to produce long-lasting local anesthesia and nociceptive blockade after a single shot in humans, its systemic toxicity relative to conventional tertiary aminoamide local anesthetics and the underlying mechanisms warrant further study.

Background We recently found that peripheral administration of the quaternary lidocaine derivative, QX-314, produces long-lasting sensory and motor blockade in animals. The goal of this study was to test whether intrathecal QX-314 has similar properties. Methods We conducted a randomized, double-controlled, blinded study with female CD-1 mice. Animals in the treatment group received lumbar intrathecal QX-314 (0.5-10 mM; volume, 2 microl; each concentration, n = 6). Normal saline and lidocaine (70 mM) served as negative and positive controls (each group, n = 12), respectively. Animals were tested for up to 3 h for lumbosacral neural blockade and observed for adverse effects. Results No animal injected with saline and 11 of 12 (92%) animals injected with lidocaine displayed reversible lumbosacral motor blockade (P < 0.001). QX-314 (5 mM) produced motor blockade in four of the six (67%) and sensory blockade in five of the six animals (83%; P < 0.05 vs. saline). However, six of the six mice (100%) at 5 mM QX-314 and five of the six (83%) at 10 mM exhibited marked irritation; one of the six animals at 5 mM (17%) and two of the six at 10 mM (33%) died. We observed no neural blockade without adverse effects in any animal injected with QX-314. All animals injected with saline and 11 of the 12 (92%) animals injected with lidocaine demonstrated normal behavior. Conclusion Lumbar intrathecal QX-314 concentration-dependently produced irritation and death in mice, at lower concentrations than those associated with robust motor blockade. Although QX-314 did produce long-lasting neural blockade, these findings indicate that QX-314 is unlikely to be a suitable candidate for spinal anesthesia in humans.

BACKGROUND Isovaline, a nonproteinogenic alpha-amino acid rarely found in the biosphere, is structurally similar to the inhibitory neurotransmitters glycine and gamma-aminobutyric acid. Because glycine(A) and gamma-aminobutyric acid receptor agonists are antiallodynic, we hypothesized that isovaline produces antinociception in mice. METHODS All experiments were performed on female CD-1 mice using a blinded, randomized, and controlled design. The effects of RS-isovaline were studied on nociceptive responses to (1) formalin injection into the hindpaw; (2) glutamate injection into the hindpaw; and (3) strychnine injection either into the lumbar intrathecal space or cisterna magna. We determined the effects of IV RS-isovaline (50, 150, or 500 mg/kg; n = 10/dose) or intrathecal RS-, R-, and S-isovaline, glycine, and beta-alanine into the lumbar intrathecal space (5-microL volumes of 60, 125, 250, and 500 mM; n = 9/dose/group) on the response to formalin in the paw. The response to 20 microL intraplantar glutamate (750 mM) was compared with glutamate (750 mM) coadministered with isovaline. We also determined the response to intraplantar strychnine. Lumbar intrathecal (100 microM) or intracisternal (200 microM) injections of strychnine into the lumbar intrathecal space or the cisterna magna were used to induce allodynia as a measure of glycine inhibitory dysfunction. The effects of intrathecal or intracisternal strychnine were compared with isovaline coapplied with the strychnine (n = 8/group). RESULTS In the formalin paw test, IV isovaline did not change phase I but decreased phase II responses in a dose-dependent manner (50% effective dose = 66 mg/kg, n = 10, P < 0.01). There was no effect on rotarod performance, appearance, or behavior of the mouse, and no respiratory depression. Intrathecal isovaline, glycine, and beta-alanine attenuated phase I and II responses (P < 0.01 for each drug). In contrast to beta-alanine and glycine, isovaline at maximally effective doses did not produce scratching, biting, or agitation. Intrathecal RS- and S-isovaline attenuated phase I (P < 0.05 for each group) and RS-, R-, and S-isovaline attenuated phase II responses (P < 0.05 for each group), with no significant difference between the efficacies of R- and S-enantiomers. Localized strychnine-induced glycine inhibitory dysfunction was greatly reduced by intracisternal (P < 0.01) and intrathecal (P < 0.01) isovaline. Although intraplantar strychnine did not induce peripheral allodynia, high doses of isovaline did not block the peripheral allodynia induced by glutamate. CONCLUSIONS Isovaline reduced responses in mouse pain models without producing acute toxicity, possibly by enhancing receptor modulation of nociceptive information.

The use of peripheral tramadol to block pain has been advocated. However, since its actions in the periphery have not been elucidated fully, we tested the hypothesis that peripheral tramadol blocks peripheral glutamate-induced nociceptive behaviour in mice.First, we compared the duration of paw licking after intraplantar (ipl.) glutamate administration, with and without tramadol, using a randomized blinded controlled design. Next, we established the half maximal effective concentrations (EC(50s)) for local tramadol and reference compound lidocaine in the hot water tail-flick latency test and the glutamate-induced paw allodynia assay.Tramadol reduced glutamate-induced paw licking from 33 +/- 12 sec to 4 +/- 4 sec (mean +/- SD; t test, P0.05; n = 6 per group). The tramadol and lidocaine EC(50) nerve conduction blocks in the tail did not differ significantly (84 +/- 24 mM vs 69 +/- 5 mM, respectively). Although tramadol reduced glutamate-induced allodynia (EC(50), 46 +/- 13 mM), lidocaine was more potent (EC(50), 13 +/- 5 mM; Dixon's up-and-down method; P0.05). Tramadol was 2.5 times as effective at blocking nerve conduction in the tail compared with allodynia in the paw.Local tramadol administration blocked nociceptive behaviour in mice induced by peripheral glutamate. Compared with lidocaine, the relative potency of tramadol was lower for blocking glutamate-induced allodynia than for sensory nerve conduction blockade, suggesting the activation of a pronociceptive receptor system in the periphery.

BACKGROUND: Conventional incremental bolus administration of neuromuscular blocking (NMB) drugs is associated with limitations in intraoperative control, potential delays in recovery, and residual blockade in the postanesthetic period. To overcome such limitations, we developed a novel adaptive control computer program, the Neuromuscular Blockade Advisory System (NMBAS). The NMBAS advises the anesthesiologist on the timing and dose of NMB drugs based on a sixth-order Laguerre model and the history of the patient’s electromyographic responses. Here, we tested the hypothesis that the use of the NMBAS improves NMB compared to standard care. METHODS: We conducted a prospective, randomized, controlled, blinded, parallelgroup, clinical trial with n 73 patients (ASA physical status I-III) undergoing abdominal surgery under general anesthesia 1.5 h with NMB using rocuronium. Patients were allocated to standard care or NMBAS-guided rocuronium administration. The primary outcome variable was the incidence of intraoperative events reflecting inadequate NMB. Secondary outcome variables included train-of-four (TOF) ratios at the end of surgery before reversal, the total doses of rocuronium, reversal agents, anesthetics and other drugs, the incidence of postoperative adverse events, and the incidence of anesthesiologist noncompliance with NMBAS recommendations. RESULTS: Of 73 enrolled patients, n 30 per group were eligible for analysis. Patient demographics were comparable between the groups. The incidence in total intraoperative events associated with inadequate NMB was significantly lower in the NMBAS group compared to standard care (8/30 vs 19/30; P 0.004). Mean TOF ratios at the end of surgery before reversal were higher in the NMBAS group (0.59 [95% CI, 0.48–0.69] vs 0.14 [95% CI, 0.04–0.24]; P 0.0001). Total administered doses of rocuronium, reversal drugs, and other drugs, and the incidence of postoperative adverse events were not different. CONCLUSIONS: Compared to standard practice, NMBAS-guided care was associated with improved NMB quality and higher TOF ratios at the end of surgery, potentially reducing the risk of residual NMB and improving perioperative patient safety. (Anesth Analg 2008;107:1609‐17)

Background: QX-314 is a quaternary lidocaine derivative considered to be devoid of clinically useful local anesthetic activity. However, several reports document that extracellular QX-314 application affects action potentials. Hence, the authors tested the hypothesis that QX-314 could produce local anesthesia in animal models in vivo. Methods: The authors tested QX-314 (10, 30, and 70 mM )i n three standard in vivo local anesthetic animal models, using a randomized, blinded experimental design with negative (placebo) and positive (70 mM lidocaine) controls. The guinea pig intradermal wheal assay (n 29) was used to test for peripheral inhibition of the cutaneous trunci muscle reflex, the mouse tail-flick test (n 30) was used to test for sensory blockade, and the mouse sciatic nerve blockade model (n 45) was used to test for motor blockade. Results: In all three animal models, QX-314 concentrationdependently and reversibly produced local anesthesia of long duration, at concentrations equivalent to those clinically relevant for lidocaine. In the guinea pig intradermal wheal assay, QX-314 produced peripheral nociceptive blockade up to 6 times longer than lidocaine (650 171 vs. 100 24 min [mean SD]; n 6 per group; P < 0.0001). In the mouse tail-flick test, QX-314 produced sensory blockade up to 10 times longer than lidocaine (540 134 vs. 50 11 min; n 6 per group; P < 0.0001). Finally, in the mouse sciatic nerve model, QX-314 produced motor blockade up to 12 times longer compared with lidocaine (282 113 vs. 23 10 min; n 9 or 10 per group; P < 0.0001). The onset of QX-314‐mediated blockade was consistently slower compared with lidocaine. Animals injected with saline exhibited no local anesthetic effects in any of the three models. Conclusion: In a randomized, controlled laboratory study, the quaternary lidocaine derivative, QX-314, concentration-dependently and reversibly produced long-lasting local anesthesia with a slow onset in animal models in vivo. The authors’ results raise the possibility that quaternary ammonium compounds may produce clinically useful local anesthesia of long duration in humans and challenge the conventional notion that these agents are ineffective when applied extracellularly. LOCAL anesthetic research during the past four decades has demonstrated that amino-ester and amino-amide local anesthetics block the generation and propagation of action potentials via an intracellular site of action at the voltage-gated Na channel. 1– 4 Many of the underlying experiments were performed using QX-314 (lidocaine N-ethyl chloride; N-(2,6-dimethylphenylcarbamoylmethyl)triethylammonium chloride; molecular weight, 298.9), a lidocaine derivative whose sole structural difference to the mother compound is in the presence of an additional N-ethyl group. This permanently renders the amino group quaternary, i.e., positively charged. As a result, the agent cannot readily pass biologic membranes. Indeed, a series of in vitro experiments where QX-314 was applied extracellularly found this agent to be ineffective in blocking action potentials. 5– 8 In contrast, intracellular application of QX-314 to peripheral and central neurons produces marked local anesthetic actions, blocking both fast, Na-dependent action potentials and voltage-dependent, noninactivating Na conductances. 5–10 However, various studies on a range of other quaternary cationic compounds have shown that these can block electrical conductances in axons when applied outside of the cell. Such studies involved QX572, 11,12 quaternary tropine esters, 7,13 tonicaine, 14 –16

Isovaline is a non-proteinogenic amino acid that has analgesic properties. R-isovaline is a proposed agonist of the γ-aminobutyric acid type B (GABA(B)) receptor in the thalamus and peripheral tissue. Interestingly, the responses to R-isovaline differ from those of the canonical GABA(B) receptor agonist R-baclofen, warranting further investigation. Using whole cell recording techniques we explored isovaline actions on GABA(B) receptors coupled to rectifying K+ channels in cells of recombinant and native receptor preparations. In AtT-20 cells transfected with GABA(B) receptor subunits, bath application of the GABA(B) receptor agonists, GABA (1 μM) and R-baclofen (5 μM) produced inwardly rectifying currents that reversed approximately at the calculated reversal potential for K+ R- isovaline (50 μM to 1 mM) and S-isovaline (500 μM) did not evoke a current. R-isovaline applied either extracellularly (250 μM) or intracellularly (10 μM) did not alter responses to GABA at 1 μM. Co-administration of R-isovaline (250 μM) with a low concentration (10 nM) of GABA did not result in a response. In cultured rat hippocampal neurons that natively express GABA(B) receptors, R-baclofen (5 μM) induced GABA(B) receptor-dependent inward currents. Under the same conditions R-isovaline (1 or 50 μM) did not evoke a current or significantly alter R-baclofen-induced effects. Therefore, R-isovaline does not interact with recombinant or native GABA(B) receptors to open K+ channels in these preparations.

In this paper, preliminary results of the Neuromuscular Blockade Advisory System (NMBAS) clinical trial comparing the safety and efficacy of NMBAS to standard care are presented. The NMBAS offers advice to the anesthesiologist on dosing of rocuronium based on measured patient response. The NMBAS is being compared against standard practice in a randomized, controlled clinical trial. The NMBAS uses a sixth order Laguerre model to approximate neuromuscular response and a extended horizon control scheme to predict future levels and needs for NMB agent. Thirty-six patients were tested, thirteen patients in the NMBAS group, eleven in the standard care group and twelve excluded. Patient health and demographics, procedures, drug use, and ability to maintain surgically useful conditions and with easy reversibility were equivalent between the two groups. The incidence of adverse events in the OR showed a marked improvement with the NMBAS. As well, responses measured at reversal and extubation were higher for the NMBAS indicating less chance of post-operative adverse events.

Exposure to general anesthesia may contribute to postoperative cognitive impairment in elderly patients, but the relationship remains poorly understood. We investigated whether aged mice, 18-19 mo, are more susceptible to postanesthetic cognitive impairment than young mice, 3-4 mo, using spatial memory (Barnes maze) and psychomotor (rotarod) tasks. Initially we studied the effect of a single anesthetic episode on asymptotic maze performance. We then tested whether repeated anesthesia would impair spatial memory and psychomotor performance to a greater extent in aged mice. Mice were anesthetized with isoflurane (1.4% atm) for 30 min; controls received 90% oxygen. Anesthesia, administered during the asymptotic period of maze learning, did not impair performance tested the following day (P0.05). Repeated anesthesia, 2-3 h after each session, did not impair overall maze or rotarod performance in young or aged mice (P0.05). Spatial learning appeared to be facilitated by anesthesia, F(1,204) = 7.97, P0.01 for pooled results. Asymptotic performance-when learning had stabilized-remained unimpaired in both the maze and rotarod tasks. These results suggest that an age-related risk of anesthetic-induced impairment appears to be limited to acquisition of a novel motor skill and that anesthesia alone does not lead to prolonged cognitive impairments in aged mice.This study demonstrates that repeated isoflurane general anesthesia impaired psychomotor performance in aged mice during the initial learning period; however, spatial learning improved and, overall, spatial memory and psychomotor performance were unimpaired. Thus, general anesthesia alone does not appear to result in prolonged cognitive deficits in aged mice.

Background: Cognitive impairments are the main complication after electroconvulsive therapy (ECT). Modification of treatment parameters has been shown to affect the magnitude of these impairments, but the role of anesthetic type remains unclear. This study tested whether there is a difference in cognitive impairments immediately after ECT with propofol compared to thiopental anesthesia. Methods: This randomized, double-blind, crossover study included 15 patients receiving right unilateral ECT for depression. Patients received propofol or thiopental on alternating ECTs up to 6 treatments. Immediate and delayed verbal memory, motor speed, reaction speed, visuospatial, and executive functions were assessed 45 minutes after each ECT. Differences were assessed with repeated measures analysis of variance. Results: Cognitive impairments were reduced after ECT with propofol compared to thiopental. Time to emergence was quicker and EEG seizure duration was shorter after propofol treatments. There was no significant correlation between seizure duration and neuropsychological test performance. Conclusions: Our results indicate that cognitive impairments in the early recovery period after ECT are reduced with propofol compared to thiopental anesthesia. We suggest that, in addition to ECT parameters, the type of anesthetic agent should be considered to reduce cognitive impairments after ECT.

We previously showed that isovaline is a peripheral analgesic which acts in vivo and in brain slices as an atypical metabotropic GABA B agonist. Peripheral inhibitory group II and III metabotropic glutamate receptors (mGluRs) belong to the same family C as GABA B receptors; therefore, we hypothesized that isovaline’s analgesic effects could include their activation. We examined the effects of R-isovaline on mechanical allodynia produced by prostaglandin E 2 in the mouse paw. Subcutaneous R-isovaline produced dose-dependent antiallodynia restricted to the injected hindlimb. This antiallodynia was blocked by co-injection with a selective group II mGluR antagonist, LY341495, but not a group III mGluR antagonist (MAP-4). The antiallodynic effect of R-isovaline was potentiated by co-administration of a group II mGluR-positive allosteric modulator, LY487379. Injection of a group II mGluR agonist (LY354740) produced an antiallodynic effect which was completely reversed by group II antagonism, but was not affected by group III or GABA B (CGP35348) antagonism. Similarly, group II mGluR antagonism did not alter the antiallodynia produced by the prototypical GABA B agonist, baclofen. Hence, there was no apparent crosstalk between group II mGluRs and GABA B receptors. Previous studies have demonstrated that peripheral GABA B receptor activation by isovaline produces antiallodynia. In addition, the present results indicate that activation of peripheral group II mGluRs by R-isovaline produces antiallodynia.

To test the efficacy of a combination of selective pre- and post-surgical local anesthetic infiltrations of the knee, compared with standard intra-articular injection at the end of surgery alone, to reduce postoperative opioid requirements following arthroscopic cruciate ligament reconstruction (ACLR).In a double-blind, randomized, controlled trial, we studied 23 patients (ASA I or II) scheduled for elective ACLR under general anesthesia. The treatment group (n = 12) received infiltrations with bupivacaine 0.25% with epinephrine 1:200,000 presurgically (10 ml into the portals, 10 ml at the medial tibial incision site, 10 ml at the lateral femoral incision site, and 10 ml intra-articularly) and postsurgically (5 ml at the medial tibial incision and 10 ml at the lateral femoral incision). The control group (n = 11) received infiltrations with saline 0.9% in the same manner. All patients received a standard intra-articular local anesthetic instillation of the knee (25 ml of bupivacaine 0.25% with epinephrine 1:200,000) at the completion of surgery.Postoperative opioid requirements were lower in the treatment group (5.8 +/- 2.9 mg morphine equivalent) than in the control group ( 13.7 +/- 5.8 mg; P = 0.008). Treatment patients were ready for discharge approximately 30 min earlier than control patients (P = 0.046). There were no adverse events in the treatment group. In the control group, 2/11 patients vomited and a third experienced transient postoperative diaphoresis, dizziness and pallor.We conclude that a combination of selective pre- and post-surgical wound infiltration with bupivacaine 0.25% provides superior analgesia compared with a standard post-surgical intra-articular injection alone.

The electrophysiological actions of lidocaine, tedisamil and RSD1019 were assessed on normal and ischaemic cardiac tissue using monophasic action potentials (MAPs) recorded from the epicardium of anaesthetized rabbits. Drug effects on ischaemia-induced arrhythmias were assessed simultaneously in the same rabbits. Lidocaine, infused at 2.5, 5 and 10 μmol kg−1 min−1 i.v., accelerated and worsened the electrophysiological derangement caused by ischaemia, had profibrillatory actions and reduced the time to the occurrence of ventricular fibrillation (VF) relative to controls. Tedisamil, infused at 0.063, 0.125 and 0.25 μmol kg−1 min−1 i.v., prolonged MAP duration at 90% repolarization (MAPD90%) before induction of ischaemia in a dose-related manner; however, this effect was not maintained 5 min after induction of ischaemia. Tedisamil had no significant antiarrhythmic actions over the dose-range tested. RSD1019, infused at 2, 4 and 8 μmol kg−1 min−1 i.v., produced a small increase in MAPD90% before induction of ischaemia and only at the highest dose tested. In contrast to tedisamil, RSD1019 suppressed ischaemia-induced MAP shortening assessed 5 min after induction of ischaemia. This effect was dose-related. RSD1019 completely prevented ischaemia-induced tachyarrhythmias at the mid and highest infusion levels tested. The results of this study illustrate a pathologically targeted approach for preventing ischaemia-induced arrhythmias. Suppression of ischaemia-induced MAP shortening, demonstrated herein for RSD1019, represents a novel antifibrillatory approach. British Journal of Pharmacology (2000) 131, 405–414; doi:10.1038/sj.bjp.0703592

To determine the "real world" cost of sevoflurane compared with isoflurane in balanced general anesthesia for daycare arthroscopic menisectomy, we prospectively investigated perioperative drug requirement and expense as well as recovery time.Following intravenous induction, 40 consenting adult patients randomly received either sevoflurane- or isoflurane-based anesthesia with a standardized gas inflow rate of 3 l x min. Recovery was assessed in the postanesthetic recovery room (PARR) in a double-blind manner at 15 min intervals using the Aldrete scoring system until patients met discharge criteria.Patient demographics, anesthetic duration, volatile potency and adjunct drug requirements were similar in the two groups. Total perioperative drug cost per patient was CAN$38.10+/-10.13 (mean +/- SD) for the sevoflurane group and $23.87+/-6.59 for the isoflurane group (P0.01). Although the nonvolatile drug cost was comparable between the two groups, the volatile drug cost per patient was $19.40+/-8.80 for sevoflurane and $4.50+/-1.90 for isoflurane (P0.01). This four-fold sevoflurane-to-isoflurane cost difference was the product of two ratios, both based on the volume of liquid anesthetic: the ratio of consumption, 2.1; and the ratio of institutional price, 2.1. Intraoperative hemodynamic response, time until discharge from the PARR and incidences of postoperative nausea and vomiting did not significantly differ between the two groups.When used to maintain equipotent balanced general anesthesia for daycare arthroscopic menisectomy, volatile consumption and cost were greater for sevoflurane compared with isoflurane. Nonvolatile perioperative drug cost and recovery times were similar, however, in the two groups.

A method of recording epicardial monophasic action potentials (MAPs) and ischemia-induced arrhythmias following coronary artery ligation in intact rabbits is described. It is expected that this model will have utility in analyzing drug effects and mechanisms of ischemic arrhythmogenesis. Rabbits were found to have two arrhythmic phases following coronary artery occlusion which correspond to phase Ia and Ib arrhythmias in other species. Epicardial MAPs recorded from ischemic tissue allowed electrophysiological effects to be correlated with these phases. Phase Ia arrhythmias occurred within the first 2 min of coronary artery occlusion and were associated with a reduction in the maximum upstroke velocity of MAPs and changes in MAP duration, including the occurrence of alternans in duration. Phase Ib arrhythmias occurred between 8 and 15 min after coronary artery occlusion. These arrhythmias were associated with a decrease in MAP duration and amplitude, alternans in MAP duration as well as conduction block. Coronary artery occlusion reliably induced arrhythmias in rabbits if the left branch of the coronary artery and the left anterior descending artery were occluded. There was a 95% incidence of premature ventricular contractions, 38% of ventricular tachycardia, and 48% of ventricular fibrillation (n = 21). The results of this study show that epicardial MAPs can be used to aid in the characterization of the electrophysiological mechanisms of ischemia-induced arrhythmias in vivo.

Background There is a clinical requirement for longer-acting local anesthetics, particularly for the management of post-operative and chronic pain. In this regard, liposomes have been suggested to represent a potentially useful vehicle for sustained drug release after local administration. In the current study, the authors used a transmembrane pH gradient to efficiently encapsulate bupivacaine within large unilamellar vesicles. They report on the kinetics of drug uptake and release and the duration of nerve blockade. Methods The rate and extent of bupivacaine uptake into large unilamellar vesicles that exhibit a pH gradient (interior acidic) were determined and compared to drug association with control liposomes that did not exhibit a proton gradient. In subsequent studies, researchers examined the kinetics of bupivacaine release from these liposome systems in vitro. Using the guinea pig cutaneous wheal model, the rate of clearance of the liposome carrier was monitored after intradermal administration, using a radiolabelled lipid marker, and the duration of nerve blockade produced by free and liposomal bupivacaine was compared. Results Bupivacaine was rapidly and efficiently accumulated within liposomes that exhibited a pH gradient (interior acidic) with trapping efficiencies of 64-82% of total drug, depending on the initial bupivacaine:phospholipid ratio. Little uptake was seen, however, for control vesicles that did not exhibit a transmembrane proton gradient. Using an in vitro model of drug clearance, liposomally encapsulated bupivacaine was found to be slowly released for a longer period of time compared with either the free drug or bupivacaine associated with control (no pH gradient liposomes). In the guinea pig cutaneous wheal model, more than 85% of the liposomal carrier was found to remain at the site of administration for 2 days. The sustained drug release afforded by liposomes that exhibited a pH gradient resulted in an increase in the duration of nerve blockade of as much as threefold compared with either the free drug or bupivacaine in the presence of control (no pH gradient) liposomes. Recovery of half maximal response (R2.5) after administration of 0.75% free bupivacaine, for example, was approximately 2 h, whereas the same dose of bupivacaine in pH gradient liposomes exhibited a R2.5 of approximately 6.5 h. Conclusions Large unilamellar vesicles that exhibit a pH gradient can efficiently encapsulate bupivacaine and subsequently provide a sustained-release system that greatly increases the duration of neural blockade.

Intractable neuropathic dynamic allodynia remains one of the major symptoms of human trigeminal neuropathy and is commonly accepted to be the most excruciatingly painful condition known to humankind. At present, a validated animal model of this disorder is necessary for efficient and effective development of novel drug treatments. Intracisternal strychnine in rats has been shown to result in localized trigeminal dynamic allodynia, thus representing a possible model of trigeminal neuralgia. The purpose of this study was to validate a mouse model of trigeminal glycinergic inhibitory dysfunction using established positive (carbamazepine epoxide) and negative (morphine) controls. The actions of conventional first-line treatment (carbamazepine epoxide [CBZe]) and clinically ineffective morphine were tested for trigeminal dynamic mechanical allodynia produced by intracisternal strychnine. In mice under halothane anesthesia, we injected either strychnine (0.3 μg), strychnine with CBZe (4 ng), or artificial cerebrospinal fluid (aCSF) intracisternally (i.c.). In a separate set of experiments, subcutaneous morphine (3 mg·kg−1 sc) was injected with intracisternal strychnine. Dynamic mechanical allodynia was induced by stroking the fur with polyethylene (PE-10) tubing. The response of each mouse was rated to determine its allodynia score, and scores of each group were compared. In addition, in a separate dichotomous disequilibrium study, pairs of mice were injected with strychnine/saline, strychnine/strychnine-CBZe, or strychnine/strychnine-morphine. A blinded observer recorded which mouse of each pair had the greater global pain behaviour. Strychnine (i.c.) produced higher quantitative allodynia scores in the trigeminal distribution (mean 81.5%; 95% confidence interval [CI] 76.4 to 86.6) vs the aCSF group (mean 11.3%; 95% CI 8.1 to 14.4) (P

In this paper, we propose a novel wavelet-based algorithm for the detection of epileptic seizures. The algorithm is based on the recognition of rhythmic activities associated with ictal states in surface EEG recordings. Using a moving-window analysis, we first decomposed each EEG segment into a wavelet packet tree. Then, we extracted the coefficients corresponding to the frequency band of interest defined for rhythmic activities. Finally, a normalized index sensitive to both the rhythmicity and energy of the EEG signal was derived, based on the resulting coefficients. In our study, we evaluated this combined index for real-time detection of epileptic seizures using a dataset of approximately 11.5 hours of multichannel scalp EEG recordings from three patients and compared it to our previously proposed wavelet-based index. In this dataset, the novel combined index detected all epileptic seizures with a false detection rate of 0.52/hr.

1. Rats were used to evaluate the antiarrhythmic properties of tedisamil, a novel agent with the electrophysiological properties of a Class III antiarrhythmic drug. Tedisamil was tested against coronary artery occlusion-induced arrhythmias in conscious animals. 2. The actions of tedisamil on the ECG, as well as responses to electrical stimulation, were compared with those on the configuration of epicardial intracellular action potentials recorded in vivo. 3. Tedisamil (1-4 mg kg-1, i.v.) caused bradycardia, elevated blood pressure and dose-dependently reduced ventricular fibrillation (VF) induced by occlusion of the left anterior descending coronary artery. Other ischaemia-associated arrhythmias were not so well suppressed. Antiarrhythmic activity was greatest when the tedisamil-induced bradycardia was prevented by electrically-pacing the left ventricle. 4. Tedisamil dose-dependently lengthened the effective refractory period and prevented electrically-induced VF. In vivo, tedisamil (0.5-4 mg kg-1, i.v.) prolonged the duration of epicardial intracellular action potentials by up to 400%. 5. Results showed that tedisamil possessed antifibrillatory actions in rats that were related to Class III electrophysiological actions as revealed by electrical stimulation and electrophysiological analyses.

Electroconvulsive therapy (ECT) is an effective treatment for severe depression. In this paper, we have used an algorithm based on wavelet packet (WP) analysis of EEG signals to detect seizures induced by ECT. After determining dominant frequency bands in the ictal period during ECT, the energy ratio of these bands was computed using the corresponding WP coefficients. This ratio was then used as an index to recognize seizure periods. Four different approaches to detect ECT seizures were employed in 41 EEG recordings from nine patients. Sensitivity in ECT seizure detection ranged from 76 to 95% while the false detection rate ranged from 6 to 13.

This paper investigates the use of wavelet decomposition of the electroencephalogram (EEG) to assess the hypnotic state of anesthetized patients undergoing surgery. A single case study and a comparison with an existing monitor of hypnosis are presented. The proposed technique can differentiate clearly between the anesthetized state and the awake "baseline" state.

OBJECTIVE To provide evidence for the clinical efficacy of changes in urinary pH on the pain associated with interstitial cystitis (IC). PATIENTS AND METHODS A prospective, randomized, double-blind cross-over study was conducted with 26 women with IC between 2000 and 2002, consisting of cross-over instillations of urine at physiological pH (5.0), and neutral buffered pH (NaH2PO4 buffered to pH 7.5). The outcome measured was the subjective symptom of pain assessed using a visual analogue scale at baseline, after the initial instillation of solution, at washout, and after the crossover instillation. Data were analysed using repeated-measures analysis of variance. RESULTS There was no statistically significant difference between the mean (sd) change from baseline pain scores after instilling neutral buffered solution, at 0.50 (2.78), and acidic solution, at 0.33 (3.43) (P = 0.85). Secondary outcomes were analysed, including baseline variability and treatment-order effects; neither were significantly different between the groups. CONCLUSIONS There was no statistically significant difference in subjective pain scores on instilling urine at physiological pH or sodium-phosphate buffered saline in these patients with IC. Further work is required to define the role, if any, of urinary pH in the pathophysiology and treatment of IC.

To compare the measured "real world" perioperative drug cost and recovery associated with desflurane- and isoflurane-based anesthesia in short (less than one hour) ambulatory surgery.We conducted a prospective, randomized, blinded trial with patients undergoing arthroscopic meniscectomy under general anesthesia. Following iv induction, patients received either isoflurane (group I; n = 25) or desflurane (group D; n = 20) for maintenance. The primary outcome variable was total perioperative drug cost per patient in Canadian dollars. Secondary outcome variables included volatile agent consumption and cost, adjuvant anesthetic and postanesthesia care unit (PACU) drug cost, readiness for PACU discharge, and incidence of adverse events.Total perioperative drug cost per patient was 14.58 +/- 6.83 Canadian dollars (mean +/- standard deviation) for group I, and 21.47 +/- 5.18 Canadian dollars for group D (P0.001). Isoflurane consumption per patient was 6.0 +/- 3.0 mL compared to 18.6 +/- 7.7 mL for desflurane (P0.0001); corresponding costs were 0.83 +/- 0.42 Canadian dollars vs 7.61 +/- 3.15 Canadian dollars (P0.0001). There were no differences in adjuvant anesthetic or PACU drug cost. All but one patient from each group were deemed ready for PACU discharge at 15 min postoperatively (Aldrete scoreor= 9). One patient in group D experienced postoperative nausea. No other adverse events were noted.Measured total perioperative drug cost for a short ambulatory procedure (less than one hour) under general anesthesia was higher when desflurane rather than isoflurane was used for maintenance, essentially due to volatile agent cost. Desflurane use did not translate into faster PACU discharge under "real world" conditions.

Current aerosol irritant assays trap animals in noxious atmospheres and put a lot of stress on them. For this reason, the Minimal Animal Stress Irritant Assay Chamber (MASIAC) was developed based on the principle of avoidance, and evaluated. The MASIAC reproducibly detected citric acid with more sensitivity than conventionally used assays. With a group of mice tested simultaneously, the responses were not significantly affected by the presence of other mice. In addition, following multiple exposures to citric acid, the mice either sensitized to the irritant, or learned to avoid it. This suggests a number of areas where the MASIAC could be applied, including behavioral and asthma research. If this new method turns out to be as good as currently used assays, it could provide investigators with an alternative, more humane method of evaluating pulmonary irritants.

To test the hypothesis that the addition of a preincisional femoral 3-in-1 block to intra-articular instillation with ropivacaine 0.2% at the end of surgery improves postoperative pain control in patients undergoing arthroscopic anterior cruciate ligament reconstruction (ACLR) under general anesthesia.In a prospective, randomized, placebo-controlled, double-blind trial, we studied 44 patients scheduled for inpatient ACLR. Prior to incision, the treatment group (n = 22) received a femoral 3-in-1 block with 40 ml ropivacaine 0.2%, augmented by infiltrations of the lateral and anteromedial incisions with 20 ml ropivacaine 0.2% at the end of the procedure. The control group (n = 22) received saline 0.9% instead of ropivacaine. All patients received an intra-articular instillation with 30 ml ropivacaine 0.2% at the end of surgery. The primary efficacy variable was 24 hr morphine consumption postoperatively standardized by weight, administered intravenously via a patient-controlled analgesia (PCA) pump.There was no difference between both groups in 24 hr PCA morphine consumption postoperatively (control, 0.45 +/- 0.44 [mean +/- SD] mg x kg(-1); treatment, 0.37 +/- 0.50 mg x kg(-1); p = 0.55). No difference was found in postoperative visual analog scale pain scores, adverse events, or vital signs. In the treatment group, R = 10/22 patients did not require postoperative morphine compared with R = 6/22 in the control group (P = 0.35).We found no effect of a femoral 3-in-1 block with ropivacaine 0.2% on postoperative analgesic consumption, compared to intra-articular instillation with ropivacaine 0.2% alone, in patients undergoing ACLR under general anesthesia.

The antiarrhythmic and electrophysiological actions of quinacainol, a new Class I antiarrhythmic, were assessed in rats. Electrophysiological actions of quinacainol were assessed in vivo in terms of drug-induced changes in ECG, responses to left ventricular electrical stimulation, and changes in epicardial intracellular potentials to precisely characterize the electrophysiological effects of this putative subclass Ic antiarrhythmic compound. Antiarrhythmic actions were assessed in conscious rats subjected to occlusion of the LAD coronary artery. Antiarrhythmic actions occurred with 2.0 and 4.0 mg/kg, whereas 8.0 mg/kg was pro-arrhythmic. At doses of 0.5 mg/kg and above quinacainol increased threshold currents for capture and for ventricular fibrillation. Doses of 2.0 mg/kg and above increased ventricular refractoriness. From 1.0 to 8.0 mg/kg, quinacainol reduced dV/dtmax of phase 0 of epicardial action potentials but only 8.0 mg/kg increased action potential duration. The Q-T interval was also increased with the highest dose. Quinacainol dose-relatedly increased P-R interval whereas QRS did not change. Thus the Class I electrophysiological properties of quinacainol over the dose range tested did not fit accurately into a single subclass of the various subclasses of Class I. However, the Class Ic actions seen with 2.0 and 4.0 mg/kg were associated with antiarrhythmic actions.

The effects of variations in serum concentrations of potassium on the occurrence and severity of ischemia- and reperfusion-induced arrhythmias have been studied in conscious rats. Serum potassium concentrations were modified by maintaining rats on diets which varied in potassium concentration, by treatment with hydrochlorthiazide, amiloride, spironolactone or infusions of potassium chloride. An inverse linear relationship was demonstrated between ischemia-induced arrhythmias and log e serum potassium concentration such that a 50% reduction in arrhythmias occur with a 3.8-fold increase in serum potassium concentration. On the other hand, the incidence of reperfusion-induced arrhythmias after 7 min of regional ischemia prior to reperfusion in previously untreated rats were not influenced by elevation of serum potassium concentrations prior to and after reperfusion. Effects on ischemia-induced arrhythmias could not be explained by changes in blood pressure or heart rate. It is speculated that modification of potassium concentration in non-ischemic or border zone ventricular tissue may directly modify arrhythmogenesis due to ischemia but not that due to reperfusion.

The actions of intravenous verapamil against arrhythmias induced by occlusion of a coronary artery were investigated in conscious rats. Verapamil (2-20 mg kg-1, i.v. given pre-occlusion) dose-dependently reduced arrhythmias in rats with either large or small occluded zones at an ED50 of 6 mg kg-1. This dose was effective when given immediately post-occlusion. Severe arrhythmias, as opposed to PVC, were preferentially reduced. In conscious, and pentobarbitone-anaesthetized rats, verapamil (6 mg kg-1) had different effects on electrically-induced arrhythmias, and the ECG, from an equi-effective anti-arrhythmic dose of quinidine (20 mg kg-1, i.v.). Quinidine decreased following frequency, but increased threshold current and pulse width, whereas verapamil did not. Both drugs increased P-R interval, but only quinidine increased QRS and Q-T intervals. Thirty minutes post-occlusion, the verapamil content of tissue and blood was determined after a 6 mg kg-1 dose given pre- or post-occlusion. Measurable levels of verapamil were found in both normal and ischaemic myocardium. Plasma and plasma water concentrations were 3.6 +/- 0.8 mumol l-1 and 0.6 +/- 0.1 mumol l-1 (mean +/- s.e. mean), respectively following post-occlusion administration vs. 2.7 +/- 1.2 and 0.24 +/- 0.04 for pre-occlusion administration. Plasma water concentrations were close to IC50 values for inhibition of contractility in rat atria and ventricles. Similar concentrations depressed slow action potentials induced in rat ventricles by raised K+ We suggest that the ability of verapamil to prevent severe ventricular arrhythmias following myocardial ischaemia in the conscious rat is largely due to the calcium antagonist effects of the drug.