A comparison of sedative effects of xylazine alone or combined with levomethadone or ketamine in calves prior to disbudding.

OBJECTIVE: To compare the sedative effects of intramuscular xylazine alone or combined with levomethadone or ketamine in calves before cautery disbudding. STUDY DESIGN: Randomized, blinded, clinical trial. ANIMALS: A total of 28 dairy calves, aged 21 ± 5 days and weighing 61.0 ± 9.3 kg (mean ± standard deviation). METHODS: Calves were randomly allocated to three groups: xylazine (0.1 mg kg-1) and levomethadone (0.05 mg kg-1; group XL), xylazine (0.1 mg kg-1) and ketamine (1 mg kg-1; group XK) and xylazine alone (0.2 mg kg-1; group X). Local anaesthesia (procaine hydrochloride) and meloxicam were administered subcutaneously 15 minutes after sedation and 15 minutes before disbudding. The calves' responses to the administration of local anaesthesia and disbudding were recorded. Sedation was assessed at baseline and at intervals up to 240 minutes postsedation. Times of recumbency, first head lift and first standing were recorded. Drug plasma concentrations were measured. RESULTS: Data were obtained from 27 animals. All protocols resulted in sedation sufficient to administer local anaesthesia and to perform disbudding. Sedation scores significantly correlated with drug plasma concentrations (p ≤ 0.002). Times to recumbency did not differ among protocols (2.8 ± 0.3, 3.1 ± 1.1 and 2.1 ± 0.8 minutes for groups XL, XK and X, respectively), whereas interval from drug(s) administration until first head lift was significantly shorter in group XK than X (47.3 ± 14.1, 34.4 ± 5.3 and 62.6 ± 31.9 minutes for groups XL, XK and X, respectively). The area under the time-sedation curve was significantly greater in group X than XK or XL (754 ± 215, 665 ± 118 and 1005 ± 258 minutes for groups XL, XK and X, respectively). CONCLUSIONS AND CLINICAL RELEVANCE: Levomethadone or ketamine with a low dose of xylazine produced short but sufficient sedation for local anaesthesia and disbudding with minimum resistance.

Antinociceptive, physiologic and biochemical effects of electroacupuncture combined with xylazine in hybrid goats.

OBJECTIVE: To elucidate the antinociceptive, physiologic and biochemical effects of electroacupuncture (EA) and xylazine in hybrid goats. STUDY DESIGN: Prospective experimental study. ANIMALS: A total of 30 female hybrid goats aged 1-2 years and weighing 25 ± 2.9 kg (mean ± standard deviation). METHODS: The goats were divided into five groups and administered xylazine (0.1 mg kg-1; group XYL.1), xylazine (0.3 mg kg-1; group XYL.3), EA (group EA), EA + xylazine (0.1 mg kg-1; group XYL.1-EA) and 0.9% saline (0.3 mL; control group CON). Nociceptive threshold and serum glucose concentration were measured at time 0 and at 15, 30, 45, 60 minutes and 24 hours after treatment. Nociceptive threshold was measured by passing potassium ions through the skin using potassium iontophoresis. Mean arterial pressure (MAP), heart rate (HR), respiratory frequency (fR) and rectal temperature (RT) were recorded at times 0 and at 5, 10, 15, 20, 30, 45, 60 minutes and 24 hours. Repeated-measures analyses were performed for each response variable; p < 0.05 was considered significant for all analyses. RESULTS: Antinociceptive effects in groups XYL.1 and XYL.3 were increased significantly at 15-60 minutes compared with group CON. Antinociceptive effect was higher in group XYL.1-EA than groups XYL.1 or EA at 15-60 minutes (p < 0.05). No significant difference in the nociceptive threshold was recorded in groups XYL.1-EA and XYL.3, except at 30 minutes. HR, MAP, fR, RT values were higher in group XYL.1-EA than in groups XYL.1 or XYL.3. Serum glucose concentration was higher in group XYL.3 at 15-60 minutes than in CON. CONCLUSIONS AND CLINICAL RELEVANCE: The XYL.1 and EA combination was effective for antinociception with minimum physiologic alteration, suggesting that the combination may be a new and effective strategy for pain relief during clinical procedures in goats.

Ketamine and xylazine effects in murine model of acute pancreatitis.

Ketamine and xylazine (Ket/Xyl) are anesthetic agents that target neural pathways and are commonly used in combination in mouse studies. Since neural pathways can modulate acute pancreatitis severity, we asked if Ket/Xyl affect disease severity. C57BL/6 mice were treated with six hourly injections of cerulein to induce mild acute pancreatitis. Mice were also treated with and without ketamine, xylazine, and Ket/Xyl before pancreatitis induction in vivo and in vitro. Ket/Xyl pretreatment in vivo increased selected parameters of pancreatitis severity such as trypsin activity and edema; these effects were predominantly mediated by xylazine. Ket/Xyl also changed markers of autophagy. These in vivo effects of Ket/Xyl were not attenuated by atropine. The drugs had no little to no effect on pancreatitis responses in isolated pancreatic cells or lobules. These findings suggest that Ket/Xyl administration can have substantial effect on acute pancreatitis outcomes through nonmuscarinic neural pathways. Given widespread use of this anesthetic combination in experimental animal models, future studies of inflammation and injury using Ket/Xyl should be interpreted with caution.NEW & NOTEWORTHY Ketamine and xylazine anesthetic agent administration before acute pancreatitis induction in mice lead to changes in pancreatitis responses independent of acute pancreatitis induction. Future studies should consider the potential effects of anesthesia administration when studying disease processes associated with inflammation and injury.

Conditioned place aversion of caustic paste and hot-iron disbudding in dairy calves.

Cauterization by hot iron and application of caustic paste are 2 common methods of disbudding calves. In this study, we compared the affective experience of these 2 procedures on young dairy calves using conditioned place aversion. Male dairy calves (n = 14; 7 ± 2 d old) were disbudded by both thermal and chemical methods (1 horn bud at a time, 48 h apart). Calves received treatments in pens made visually distinct with either red squares or blue triangles on the walls. Calves were restricted to these treatment pens for 6 h following disbudding. For all treatments, calves received a sedative (xylazine, 0.2 mg/kg), local anesthetic (lidocaine, 5 mL), and analgesic (meloxicam, 0.5 mg/kg). Calves were then tested for conditioned place aversion at 48, 72, and 96 h after their last treatment. During tests, calves were placed in a neutral pen connected to both treatment pens where they had previously been disbudded. Time spent in each treatment pen was recorded until calves chose to lie down for 1 min (latency to lie down: 31.0 ± 8.6 min). During the first test (48 h after last disbudding), calves spent more time in the pen associated with hot-iron disbudding compared with what would be expected by chance (intercept: 73.5%, 95% CI: 56.5, 90.5) and fewer calves lay down in the caustic paste pen than in the hot-iron pen (3 vs. 10 lying events). No evidence of preference for the hot-iron pen was found in the following test sessions (72 and 96 h since last disbudding). These results suggest that calves initially remember caustic paste disbudding as a more negative experience than hot-iron disbudding, even with the use of sedation, local anesthesia, and analgesia.

Basolateral amygdala - nucleus accumbens circuitry regulates optimal cue-guided risk/reward decision making.

Maladaptive decision making is a characteristic feature of substance use disorder and pathological gambling. Studies in humans and animals have implicated neural circuits that include the basolateral amygdala (BLA) and nucleus accumbens (NAc) in facilitating risk/reward decision making. However, the preclinical literature has focussed primarily on situations where animals use internally-generated information to adapt to changes in reward likelihood, whereas many real-life situations require the use of external stimuli to facilitate context-appropriate behavior. We recently developed the "Blackjack" task, to measure cued risk/reward decision making requiring rats to chose between Small/Certain and Large/Risky rewards, with auditory cues at the start of each trial explicitly informing that the probability of obtaining a large reward was either good (50%) or poor (12.5%). Here we investigated the contribution of the BLA and its interaction with the NAc in guiding these types of decisions. In well-trained male rats, bilateral inactivation of the BLA induced suboptimal decision making, primarily by reducing risky choice on good-odds trials. In comparison, pharmacological disconnection of the BLA and NAc-shell also induced suboptimal decision making, diverting choice from more preferred option by reducing or increasing risky choice on good vs. poor odds trials respectively. Together, these results suggest that the BLA-NAc circuitry plays a crucial role in integrating information provided by discriminative stimuli. Furthermore, this circuitry may aid in guiding action selection of advantageous options in situations to maximize rewards. Finally, they suggest that perturbations in optimal decision making observed in substance abuse and gambling disorders may be driven in part by dysfunction within this circuitry.

Validation of the xylazine/ketamine anesthesia test as a predictor of the emetic potential of pharmacological compounds in rats.

The xylazine/ketamine anesthesia test is widely used as a predictor of the emetic potential of pharmacological compounds in rats. An emetic reflex is usually triggered by the emetic center, which is populated with many different chemoreceptors. Inhibition of the α2 adrenergic receptor (α2 receptor) is involved in the initiation of the emetic reflex, and this is the key mechanism behind the xylazine/ketamine anesthesia test. In this study, we attempt to validate this test as a predictor of the emetic potential of pharmacological compounds. Furthermore, it was investigated whether an anti-emetic potential of pharmacological compounds could be assessed within this test as well. Rats were anesthetized with a combination of low doses of ketamine and xylazine, and subsequently treated with PDE4 inhibitor rolipram, α2 receptor antagonist yohimbine, α2 receptor agonist clonidine, tricyclic antidepressant imipramine, D2-receptor antagonist haloperidol, or 5-HT3 receptor antagonist (and anti-emetic drug) ondansetron. We were able to successfully reproduce the reduction in anesthesia time after rolipram or yohimbine treatment, as found in previous studies and has been suggested to be indicative of emetic properties of these treatments is humans. Furthermore, clonidine shortened anesthesia duration whereas imipramine and haloperidol lengthened anesthesia duration. Ondansetron was unable to rescue the reduction in duration of anesthesia induced by either rolipram or yohimbine. Altogether, the xylazine/ketamine anesthesia test is a reliable measure for α2 receptor antagonism. However, it may not be appropriate to assess emesis independent of this mechanism.

Gas Anesthesia Impairs Peripheral Auditory Sensitivity in Barn Owls (Tyto alba).

Auditory nerve single-unit recordings were obtained from two groups of young barn owls (age, between posthatching days 11 and 86) in terminal experiments under two different anesthetic regimes: ketamine (6-11 mg/kg) plus xylazine (∼2 mg/kg); or isoflurane (1-1.5%) in oxygen, delivered via artificial respiration. In a second series of minimally invasive experiments, auditory brainstem responses (ABRs) were recorded in the same four adult barn owls (Tyto alba; age, between 5 and 32 months) under three different anesthetic protocols: ketamine (10 mg/kg) plus xylazine (3 mg/kg), isoflurane (1-1.5%), and sevoflurane (2-3%) in carbogen. Finally, the ABR measurements on adult owls were repeated in terminal experiments including more invasive procedures such as artificial respiration and higher isoflurane dosage. The main finding was a significant deterioration of auditory sensitivity in barn owls under gas anesthesia, at the level of the auditory nerve (i.e., a very peripheral level of the auditory system). The effect was drastic in the young animals that experienced threshold elevations in auditory nerve single-unit responses of ≥20 dB. ABR thresholds assessed repeatedly in experiments on adult owls were also significantly higher under isoflurane and sevoflurane, on average by 7 and 15 dB, compared with ketamine/xylazine. This difference already occurred with minimal dosages and was reversibly enlarged with increased isoflurane concentration. Finally, there was evidence for confounding detrimental effects associated with artificial respiration over many hours, which suggested oxygen toxicity.

Pharmacological analysis of Poecilotheria spider venoms in mice provides clues for human treatment.

Bites of tiger spiders belonging to Poecilotheria genus cause moderate to severe pain and long-lasting local or generalized muscle cramps in humans. Bites occur in regions of the spiders' natural habitat, India and Sri Lanka, but the popularity of these colorful tarantulas as pets leads to reports of envenomation cases worldwide. Treatment is predominantly symptomatic and often inadequate since there is almost no clinical or toxicology research data available, and physicians outside India or Sri Lanka typically have no experience in treating such cases. We report toxicity studies of venom from nine Poecilotheria species in laboratory mice (Mus musculus Balb/C males). LD50 values are 5-14 mg of lyophilized crude venom per 1 kg (i.v.). The major symptoms of envenomation include tonic-clonic seizures, jerks, characteristic motor stereotypy, and hyperalgesia and point to voltage-gated sodium channels as a potential target of the venom components. Poecilotheria fasciata venom effects were studied in detail at a sub-lethal dose of 5 mg/kg (LD50 = 12 mg/kg). 13 widely used pharmacological agents (atropine, chloropyramine, chlorpromazine, diazepam, ethanol, flupirtine, haloperidol, ketotifen, lamotrigine, oxcarbazepine, tolperisone, xylazine, and CaCl2) were checked for ability to suppress the envenomation symptoms. Chlorpromazine (10 mg/kg, i.p.), oxcarbazepine (60 mg/kg, p.o.), tolperisone (50 mg/kg, s.c.) and xylazine (2.5 mg/kg, i.p.) were found effective as a pretreatment to mitigate muscle cramps and motor stereotypy. When administered after envenomation chlorpromazine (5 mg/kg, i.v.) effectively reduced the cramps, while oxcarbazepine (30 mg/kg, i.v.) and xylazine (1 mg/kg, i.v.) suppressed the stereotypy.

Differential Intraocular Pressure Measurements by Tonometry and Direct Cannulation After Treatment with Soluble Adenylyl Cyclase Inhibitors.

PURPOSE: To validate the increase in intraocular pressure (IOP) caused by soluble adenylyl cyclase (sAC) inhibitors and determine reasons behind variation in IOP measurements performed by tonometry. METHODS: C57BL/6J mice were administered DMSO solubilized sAC inhibitors (KH7 or LRE-1) by intraperitoneal injection. Two hours post-treatment, mice were anesthetized with avertin or ketamine/xylazine/acepromazine (KXA). IOP was measured by a rebound tonometer or direct cannulation of the anterior chamber. Spectral-domain optical coherence tomography was used to measure anterior chamber depth and corneal thickness in live mice. Outflow facility was measured in perfused, enucleated mouse eyes. RESULTS: Compared with DMSO controls, KH7 treatment caused an increased IOP in avertin- and KXA-anesthetized mice when measured by direct cannulation [avertin: 14.4 ± 2.1 mmHg vs. 11.1 ± 1.0 mmHg (P = 0.003); KXA: 14.4 ± 1.0 mmHg vs. 11.3 ± 0.8 mmHg (P < 0.001)] and tonometry [avertin: 10.8 ± 1.4 mmHg vs. 7.4 ± 0.6 mmHg (P < 0.001); KXA: 11.9 ± 0.9 mmHg vs. 10.3 ± 1.7 mmHg (P = 0.283)]. However, treatment with KH7 in nonanesthetized mice showed a significant decrease in IOP measured by tonometry and compared with DMSO-treated animals [13.1 ± 2.6 mmHg vs. 15.6 ± 0.5 mmHg (P = 0.003)]. Both KH7- and DMSO-treated groups anesthetized with avertin showed increased corneal thickness, whereas KH7-treated mice anesthetized with KXA exhibited a shallower anterior chamber compared with untreated mice. KH7 decreased outflow facility by 85.1% in nonanesthetized, enucleated eyes (P < 0.003). CONCLUSIONS: Systemically administered DMSO and anesthesia have significant effects on anterior chamber characteristics, resulting in altered IOP readings measured by tonometry. In the presence of DMSO and anesthesia, tonometry IOP readings should be confirmed with direct cannulation.

Transcranial flavoprotein-autofluorescence imaging of sound-evoked responses in the mouse auditory cortex under three types of anesthesia.

The effects of anesthesia on the functional auditory characteristics of cortical neurons, such as spatial and temporal response properties, vary between an anesthetized and an awake subject. However, studies have shown that an appropriate anesthetic method that approaches the awake condition is still useful because of its greater stability and controllability. The present study compared neural response properties from two core fields of the mouse auditory cortex under three anesthetic conditions: urethane; ketamine and xylazine hydrochloride (KX) mixture; and a combination of medetomidine, midazolam, and butorphanol (MMB). To measure sound stimulation in vivo, we recorded flavoprotein-autofluorescent images of endogenous green fluorescence. Under all conditions, fluorescence changes in auditory core subfields in response to tones were observed, and response properties, such as peak intensity, latency, duration, and activated areas were analyzed. Results showed larger response peak intensity, latency, and duration in the core subfields under urethane compared with KX and MMB, with no significant differences between KX and MMB. Conversely, under KX anesthesia the activated areas showed characteristic response properties in a subfield-dependent manner. These results demonstrated the varied effects of anesthesia on response properties in the core subfields of the auditory cortex.

Effect of analgesia and anti-inflammatory treatment on weight gain and milk intake of dairy calves after disbudding.

AIM: To assess the effect of analgesia at disbudding on weight gain and milk intake of dairy calves. METHODS: Four disbudding protocols were used on 3- to 6-week-old Friesian-Jersey calves. Farm staff disbudded 101 calves without sedation or local analgesia, of which 51 received 20 mg meloxicam S/C. Veterinary staff disbudded 101 calves with sedation and local analgesia, of which 51 also received 20 mg meloxicam S/C. Calves were weighed before disbudding, 15 and 30 days later, and individual milk consumption was recorded for 11 days. Daily weight gain and milk consumption were analysed using mixed models and ANOVA. RESULTS: From disbudding (Day 0) to Day 15 farmer-disbudded calves receiving meloxicam grew faster (0.65 kg/day) than calves without meloxicam (0.55 kg/day; p=0.011), but an interaction between operator and meloxicam treatment (p=0.056) meant that meloxicam treatment did not increase growth rates in veterinary-disbudded calves (0.63 vs. 0.64 kg/day; p=0.872). From Days 16-30 there was no significant effect of meloxicam on growth rate, but veterinarian-disbudded calves grew faster (0.76 kg/day) than farmer-disbudded calves (0.66 kg/day; p=0.034). Overall, for the first 30 days after disbudding, if meloxicam was not used', veterinarian-disbudded calves grew faster than farmer-disbudded calves (p=0.002). However if meloxicam was used at disbudding there was no difference in growth rate between veterinarian- and farmer-disbudded calves (p=0.878). Mean cumulative milk consumption for the 11 days after disbudding was greater for calves disbudded by veterinary staff than by farm staff (p<0.001), but there was no effect of meloxicam treatment (p=0.618) and no interaction with operator (p=0.86) on cumulative milk consumption. CONCLUSIONS: Three to 6-week-old dairy calves disbudded by farm staff with no analgesia grew significantly slower over the next 15 days than farmer-disbudded calves given meloxicam, and slower over the next 30 days than veterinarian-disbudded calves given xylazine and lignocaine. However addition of meloxicam to the latter protocol had no effect on growth rate. Milk intake was significantly higher for 11 days for veterinarian- compared with farmer-disbudded calves. CLINICAL RELEVANCE: This study adds to the evidence that analgesia during disbudding is beneficial for calf productivity as well as calf welfare.

Systemic blockage of nitric oxide synthase by L-NAME increases left ventricular systolic pressure, which is not augmented further by Intralipid®.

Intravenous lipid emulsions (LEs) are effective in the treatment of toxicity associated with various drugs such as local anesthetics and other lipid soluble agents. The goals of this study were to examine the effect of LE on left ventricular hemodynamic variables and systemic blood pressure in an in vivo rat model, and to determine the associated cellular mechanism with a particular focus on nitric oxide. Two LEs (Intralipid(®) 20% and Lipofundin(®) MCT/LCT 20%) or normal saline were administered intravenously in an in vivo rat model following induction of anesthesia by intramuscular injection of tiletamine/zolazepam and xylazine. Left ventricular systolic pressure (LVSP), blood pressure, heart rate, maximum rate of intraventricular pressure increase, and maximum rate of intraventricular pressure decrease were measured before and after intravenous administration of various doses of LEs or normal saline to an in vivo rat with or without pretreatment with the non-specific nitric oxide synthase inhibitor N(ω)-nitro-L-arginine-methyl ester (L-NAME). Administration of Intralipid(®) (3 and 10 ml/kg) increased LVSP and decreased heart rate. Pretreatment with L-NAME (10 mg/kg) increased LSVP and decreased heart rate, whereas subsequent treatment with Intralipid(®) did not significantly alter LVSP. Intralipid(®) (10 ml/kg) increased mean blood pressure and decreased heart rate. The increase in LVSP induced by Lipofundin(®) MCT/LCT was greater than that induced by Intralipid(®). Intralipid(®) (1%) did not significantly alter nitric oxide donor sodium nitroprusside-induced relaxation in endothelium-denuded rat aorta. Taken together, systemic blockage of nitric oxide synthase by L-NAME increases LVSP, which is not augmented further by intralipid(®).

Sedative and clinical effects of the pharmacopuncture with xylazine in dogs.

PURPOSE: To investigate the sedative and clinical effects of the pharmacopuncture with xylazine, compared to the conventional dose of a intramuscular injection in dogs. METHODS: Twelve dogs were randomly distributed in two groups of six animals and treated as follows: control group (X-IM): 1mg kg(-1) of xylazine given intramuscularly (IM); pharmacopuncture group (X-Yintang): 0.1mg kg(-1) of xylazine diluted to 0.5 mL of saline injected into the Yin Tang acupoint. Heart rate, cardiac rhythm (ECG), systolic arterial blood pressure (SABP), respiratory rate (RR), rectal temperature (RT), blood glucose concentration, degree of sedation and adverse effects were evaluated. RESULTS: Sedative effect was observed in both groups. The degree of sedation was greater in X-IM only at 15 min when compared with X-Yintang group. Cardiovascular established was observed in X-Yintang group, while marked reduction in the HR and increased incidence of ECG abnormalities were detected in X-IM. In both treatment groups, minimal changes were observed in relation to SABP, RR, RT and blood glucose. High incidence (66%) of vomiting was observed in X-IM, while this adverse effect was absent in X-Yintang. CONCLUSION: Pharmacopuncture with xylazine induced clinically relevant sedative effects in dogs, with the advantage of reduction of undesirable side effects associated with α2-agonists, including bradycardia, cardiac arrhythmias, and emesis.

Sensory transduction of weak electromagnetic fields: role of glutamate neurotransmission mediated by NMDA receptors.

Subliminal electromagnetic fields (EMFs) triggered nonlinear evoked potentials in awake but not anesthetized animals, and increased glucose metabolism in the hindbrain. Field detection occurred somewhere in the head and possibly was an unrecognized function of sensory neurons in facial skin, which synapse in the trigeminal nucleus and project to the thalamus via glutamate-dependent pathways. If so, anesthetic agents that antagonize glutamate neurotransmission would be expected to degrade EMF-evoked potentials (EEPs) to a greater extent than agents having different pharmacological effects. We tested the hypothesis using ketamine which blocks N-methyl-d-aspartate (NMDA) receptors (NMDARs), and xylazine which is an α2-adrenoreceptor agonist. Electroencephalograms (EEGs) of rats were examined using recurrence analysis to observe EEPs in the presence and absence of ketamine and/or xylazine anesthesia. Auditory evoked potentials (AEPs) served as positive controls. The frequency of observation of evoked potentials in a given condition (wake or anesthesia) was compared with that due to chance using the Fisher's exact test. EEPs were observed in awake rats but not while they were under anesthesia produced using a cocktail of xylazine and ketamine. In another experiment each rat was measured while awake and while under anesthesia produced using either xylazine or ketamine. EEPs and AEPs were detected during wake and under xylazine (P<0.05 in each of the four measurements). In contrast, neither EEPs nor AEPs were observed when anesthesia was produced partly or wholly using ketamine. The duration and latency of the EEPs was unaltered by xylazine anesthesia. The afferent signal triggered by the transduction of weak EMFs was likely mediated by NMDAR-mediated glutamate neurotransmission.

Characterization of phase transition in the thalamocortical system during anesthesia-induced loss of consciousness.

The thalamocortical system plays a key role in the breakdown or emergence of consciousness, providing bottom-up information delivery from sensory afferents and integrating top-down intracortical and thalamocortical reciprocal signaling. A fundamental and so far unanswered question for cognitive neuroscience remains whether the thalamocortical switch for consciousness works in a discontinuous manner or not. To unveil the nature of thalamocortical system phase transition in conjunction with consciousness transition, ketamine/xylazine was administered unobtrusively to ten mice under a forced working test with motion tracker, and field potentials in the sensory and motor-related cortex and thalamic nuclei were concomitantly collected. Sensory and motor-related thalamocortical networks were found to behave continuously at anesthesia induction and emergence, as evidenced by a sigmoidal response function with respect to anesthetic concentration. Hyperpolarizing and depolarizing susceptibility diverged, and a non-discrete change of transitional probability occurred at transitional regimes, which are hallmarks of continuous phase transition. The hyperpolarization curve as a function of anesthetic concentration demonstrated a hysteresis loop, with a significantly higher anesthetic level for transition to the down state compared to transition to the up state. Together, our findings concerning the nature of phase transition in the thalamocortical system during consciousness transition further elucidate the underlying basis for the ambiguous borderlines between conscious and unconscious brains. Moreover, our novel analysis method can be applied to systematic and quantitative handling of subjective concepts in cognitive neuroscience.

Oxygen breathing affects 3'-deoxy-3'-18F-fluorothymidine uptake in mouse models of arthritis and cancer.

UNLABELLED: Noninvasive in vivo imaging of biologic processes using PET is an important tool in preclinical studies. We observed significant differences in 3'-deoxy-3'-(18)F-fluorothymidine ((18)F-FLT) uptake in arthritic ankles and carcinomas between dynamic and static PET measurements when mice breathed oxygen. Thus, we suspected that air or oxygen breathing and the anesthesia protocol might influence (18)F-FLT tracer uptake. METHODS: We injected arthritic, healthy, and CT26 colon carcinoma-bearing mice with (18)F-FLT before static or dynamic small-animal PET measurements. The spontaneously oxygen- or air-breathing mice were kept conscious or anesthetized with ketamine and xylazine during (18)F-FLT uptake before the 10-min static PET measurements. For dynamic PET scans, mice were anesthetized during the entire measurement. (18)F-FLT uptake was reported in percentage injected dose per cubed centimeter by drawing regions of interest around ankles, carcinomas, and muscle tissue. Additionally, venous blood samples were collected before (18)F-FLT injection and after PET measurement to analyze pH, carbon dioxide partial pressure (pCO(2)), and lactate values. RESULTS: A significantly reduced (18)F-FLT uptake was measured in arthritic ankles and in CT26 colon carcinomas when the mice breathed oxygen and were conscious during tracer uptake, compared with mice that were anesthetized during (18)F-FLT uptake. Breathing air completely abolished this phenomenon. Analysis of blood samples that were obtained from the mice before (18)F-FLT injection and after the PET scan implicated respiratory acidosis that was induced by oxygen breathing and consciousness during tracer uptake. Acidosis was found to be the primary factor responsible for the reduced (18)F-FLT uptake, as reflected by increased pCO(2) and reduced pH and lactate values. CONCLUSION: Oxygen-breathing conscious mice sustained respiratory acidosis and, consequently, reduced cell proliferation and (18)F-FLT uptake in arthritic ankles and CT26 colon carcinomas. Thus, we suggest the use of air instead of oxygen breathing for (18)F-FLT PET measurements.

High doses of ketamine-xylazine anesthesia reduce cardiac ischemia-reperfusion injury in guinea pigs.

Choosing an appropriate anesthetic protocol that will have minimal effect on experimental design can be difficult. Guinea pigs have highly variable responses to a variety of injectable anesthetics, including ketamine-xylazine (KX). Because of this variability, supplemental doses often are required to obtain an adequate plane of anesthesia. Our group studies the isolated guinea pig heart, and we must anesthetize guinea pigs prior to harvesting this organ. In this study, we sought to determine whether a higher dose of KX protected isolated guinea pig hearts against myocardial ischemia-reperfusion injury. Male Hartley guinea pigs (Crl:HA; 275 to 300 g; n = 14) were anesthetized with either of 2 doses of KX (K: 85 mg/kg, X: 15 mg/kg; or K: 200 mg/kg, X: 60 mg/kg). After thoracotomy, hearts underwent 20 min of ischemia followed by 2 h of reperfusion. The high dose of KX significantly reduced myocardial infarct size as compared with the low dose (36% ± 3% and 51% ± 6%, respectively). Furthermore, the high dose of KX improved hemodynamic function over that associated with the low dose as measured by increases in both left ventricular developed pressure (49 ± 4 and 30 ± 8 mm Hg, respectively) and maximal rate of left ventricular relaxation (-876 ± 70 and -576 ± 120 mm Hg/s, respectively). However, the high dose of KX did not alter the maximal rate of left ventricular contraction or coronary flow. These results suggest that supplementation of KX to ensure an adequate anesthetic plane may introduce unwanted variability in ischemia-reperfusion studies.

Action of a Novel PDE4 inhibitor ZL-n-91 on lipopolysaccharide-induced acute lung injury.

In the present study, we investigated the effect of classic PDE4 inhibitor rolipram and novel PDE4 inhibitor ZL-n-91 on LPS-induced acute lung injury (ALI) in mice and its mechanism. ALI was induced in ICR mice by instilling intratracheally with LPS, and mice were divided into seven groups: control (Saline), LPS group, ZL-n-91 (3 microg, 10 microg, and 30 microg kg(-1), ip), Rolipram (1.0 mg kg(-1), ip) and dexamethasone (0.5 mg kg(-1), ip). After the 6h of instilling intratracheally with LPS in mice, total leukocyte number, neutrophil number and protein content in BALF increased rapidly, a large number of neutrophil infiltration around the pulmonary vessel and airway, the lung wet weight/dry weight (w/d)ratio raised significantly. MPO activity, TNF-alpha level and cAMP-PDE, PDE4 activity in lung homogenate raised significantly. P(a)O(2), P(a)CO(2) and PH value in peripheral arterial blood also changed obviously, P(a)O(2) and PH value dropped slightly and P(a)CO(2) increased significantly in LPS group. ZL-n-91 (3 microg, 10 microg, 30 microg kg(-1)) dose-dependently reduced the total leukocyte number, neutrophil number and total protein content in BALF, MPO activity, TNF-alpha level and cAMP-PDE, PDE4 activity in lung homogenate, but the effect of ZL-n-91 in pathological changes and lung wet w/d ratio is slight; Rol and Dex significantly reduced lung wet w/d ratio and improved pathological changes, neutrophil around the pulmonary vessel and airway significantly reduced, symptoms of lung edema relieved; The PH value, P(a)O(2) and P(a)CO(2) in ZL-n-91 high dosage group and Rol group had changes, but there was no significant difference compared with LPS group or saline group; After the administration, the righting reflex recovery time significantly shorten in every group of ZL-n-91. the righting reflex recovery time of Rol group was similar with ZL-n-91 30 microg kg(-1) group, while Dex group was similar with saline group. The present study confirms that the inhibitory effect of ZL-n-91(30 microg kg(-1)) on the inflammatory reactivity, including inhibition of inflammatory cell and protein exudation, MPO and PDE4 activity, improvement of the blood gas, those effects were equivalent with rolipram 1 mg kg(-1), and suggested that ZL-n-91 was stronger than rolipram in PDE4 inhibition. So we speculated that ZL-n-91 may have stronger therapeutic potential for treatment of inflammatory disease than rolipram, meantime have stronger nervous system effect than rolipram.

Physiologic effects of electroacupuncture combined with intramuscular administration of xylazine to provide analgesia in goats.

OBJECTIVE: To investigate physiologic effects of electroacupuncture (EA) combined with xylazine administration in goats. ANIMALS: 48 healthy crossbred goats. PROCEDURES: Goats were randomly allotted to 8 groups of 3 (nonpregnant and nonlactating) female goats and 3 male goats each. The 8 treatment groups were as follows: 1 EA group, 3 xylazine (0.1, 0.2, and 0.4 mg/kg, IM) groups, 3 EA plus xylazine (0.1, 0.2, and 0.4 mg/kg, IM) groups, and 1 control group. Electroacupuncture was performed for 90 minutes. Xylazine was administered 20 minutes after EA was performed. Pain threshold, heart rate, mean arterial pressure (MAP), respiration rate, and rectal temperature were observed at 0, 5, 25, 45, 65, and 85 minutes after xylazine administration. RESULTS: Xylazine administered at 0.4 mg/kg increased the pain threshold and reduced MAP. Xylazine administered at 0.1, 0.2, or 0.4 mg/kg reduced heart rate, respiration rate, and temperature. Electroacupuncture increased the pain threshold but had no effect on heart rate, MAP, respiratory rate, or rectal temperature. Pain threshold in goats that underwent EA plus xylazine administration was higher than in goats that received EA or xylazine alone. Electroacupuncture combined with xylazine at 0.1 mg/kg did not affect heart rate, MAP, respiratory rate, or rectal temperature. Pain threshold in goats that underwent EA plus xylazine administration at 0.1 mg/kg was higher than in goats given xylazine at 0.4 mg/kg alone. CONCLUSIONS AND CLINICAL RELEVANCE: Electroacupuncture combined with xylazine, even at 0.1 mg/kg, provided analgesia without significantly affecting cardiorespiratory parameters or rectal temperature in goats.