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PubMed1991

Chemical restraint for surgery in the standing horse.

Chemical restraint can be a useful pharmacologic tool to assist the veterinarian performing surgery in the standing horse. The agents discussed impose minimal adverse side effects and are considered relatively safe when administered in the doses described. Acetylpromazine, the most widely used tranquilizer, produces mild sedation but no analgesia. The use of tranquilizers for surgical procedures requires the combined use of either a local anesthetic technique or a sedative-hypnotic or opiate to provide analgesia. Sedative-hypnotics such as xylazine and detomidine or opiates such as morphine and butorphanol are commonly used. The sedative-hypnotics also can induce deep CNS depression and may be sufficient alone for many procedures. Opiates may be used to supplement the analgesia produced by sedative-hypnotics or provide analgesia to the tranquilized horse. Opiates are not useful alone because of their potential to cause CNS excitement in the horse. The combination of detomidine and butorphanol is probably the most effective drug combination to facilitate painful surgery in the standing horse.

Animals↗
PubMed2002

Nasal administration of opioids for pain management in adults.

BACKGROUND: Nasal administration of opioids may be an alternative route to intravenous, subcutaneous, oral transmucosal, oral or rectal administration in some patients. Key features may be self-administration, combined with rapid onset of action. The aim of this paper is to evaluate the present base of knowledge on this topic. METHODS: The review is based on human studies found in Medline or in the reference list of these papers. The physiology of the nasal mucosa and some pharmaceutical aspects of nasal administration are described. The design of each study is described, but not systematically evaluated. RESULTS: Pharmacokinetic studies in volunteers are reported for fentanyl, alfentanil, sufentanil, butorphanol, oxycodone and buprenorphine. Mean times for achieving maximum serum concentrations vary from 5 to 50 min, while mean figures for bioavailability vary from 46 to 71%. Fentanyl, pethidine and butorphanol have been studied for postoperative pain. Mean onset times vary from 12 to 22 min and times to peak effect from 24 to 60 min. There is considerable interindividual variation in pharmacokinetics and clinical outcome. This may partly be due to lack of optimization of nasal formulations. Patient-controlled nasal analgesia is an effective alternative to intravenous PCA. Adverse effects are mainly those related to the opioids themselves, rather than to nasal administration. Some experience with nasal opioids in outpatients and for chronic pain has also been reported. CONCLUSION: Nasal administration of opioids has promising features, but is still in its infancy. Adequately designed clinical studies are needed. Improvements of nasal sprayer devices and opioid formulations may improve clinical outcome.

Administration, Intranasal↗
PubMed1998

Effects of intramuscular sedative and opioid combinations on tear production in dogs.

The effect of commonly used sedation protocols on tear production rate was evaluated in dogs. Schirmer I tear tests were examined before and after intramuscular injection of acepromazine and oxymorphone (ACE + OXY; n = 7), diazepam and butorphanol (DIA + BUT; n = 8), and xylazine and butorphanol (XYL + BUT; n = 8). Two Schirmer I tear tests were also performed 15-25 min apart in dogs which received no sedative drugs (control; n = 4). Tear production rate decreased to 15 +/- 2, 17 +/- 1, and 6 +/- 1 mm min-1, respectively, while control animals averaged 21 +/- 2 mm min-1 at the same time point. Because XYL + BUT profoundly decreased tear production rate, we evaluated the two drugs separately. While BUT mildly decreased tear production when given alone to dogs (18 +/- 1 mm min-1; n = 5), xylazine had no effect on tear production. Thus it appears that the two agents act synergistically to decrease tear production rate in dogs. Moreover, sterile ocular lubricant or tear replacement should be used during XYL + BUT sedation.

Journal Article↗
PubMed1997

Decreased paralysis and better motor coordination with microspinal versus PE10 intrathecal catheters in pain study rats.

We compared the standard PE10 catheter to a smaller microspinal catheter for intrathecal (IT) catheterization in rats. The PE10 or microspinal catheter was implanted in the lumbar subarachnoid space through the atlantooccipital membrane in rats (21 each group). Surviving rats without paralysis were tested on a rota-rod treadmill for motor function on Postoperative Days (POD) 3-6. Different doses of IT butorphanol were injected to demonstrate the functionality of the catheters by measuring tail-flick antinociception. Methylene blue was injected IT immediately before the spinal necropsy in each rat to identify the catheter tip location. For PE10 and microspinal catheters, the immediate death rate after the catheter implantation was 4 of 21 and 3 of 21 (no significant difference); paralysis rate was 8 of 21 and 2 of 21 (P < 0.05), and motor coordination recovery on POD6 was 67% and 91% (P < 0.01), respectively. Rats in both groups showed a dose-dependent response to IT butorphanol. Intrathecal methylene blue stained the lumbar spinal cord but not the surrounding tissue in both groups. Therefore, the microspinal catheter is better than the PE10 for IT catheterization in rats because it causes less paralysis and provides faster recovery of motor function.

Animals↗
PubMed2000

Severe lightning pain after subarachnoid block in a patient with neuropathic pain of central origin: which drug is best to treat the pain?

OBJECTIVE: There have been many reports that spinal anesthesia induces severe lightning pain in the lower limbs of patients with phantom limb pain, tabes dorsalis, or causalgia. We report on a patient with neuropathic pain of central origin who showed newly developed severe lightning pain after therapeutic subarachnoid block (SAB). We performed SAB 16 times in this patient, and he complained of severe pain each time. We investigated which drug was best for treating such induced pain by administering various drugs to the patient. SETTING: The patient was hospitalized for treatment and observation. PATIENT: The patient was a 48-year-old man with neuropathic pain secondary to an incomplete spinal cord injury at the cervical segment. INTERVENTIONS: Various drugs were administered for relieving the newly developed severe pain, and the effectiveness of these agents was compared. RESULTS AND CONCLUSIONS: Intravenous thiopental, fentanyl, butorphanol, ketamine, midazolam, droperidol, and sevoflurane-oxygen anesthesia were quite effective. Intramuscular butorphanol was not effective. Intravenous physiologic saline and atropine sulfate as a placebo, intrathecal morphine hydrochloride, intravenous mexiletine, and lidocaine were ineffective. Intravenous thiopental (approximately 1 mg/kg) was thought to obtain the best pain relief because it stopped the pain quickly, the dose needed was subanesthetic, and there was no adverse effect.

Analgesics↗
PubMed1988

The effect of four narcotics on cholecystokinin octapeptide stimulated gallbladder contraction.

In an attempt to find the ideal analgesic to treat biliary tract pain we compared the effects of saline and equianalgesic doses of morphine, pentazocine, pethidine, and butorphanol on CCK-OP stimulated gallbladder emptying in healthy volunteers. Morphine produced a profound delay in gallbladder emptying while the other narcotics produced a significant delay in comparison to saline, but less than morphine. None of the drugs affected common bile duct diameter, bilirubin, liver enzymes or amylase. We recommend avoiding the use of morphine in the treatment of biliary and pancreatic pain, but although pethidine, pentazocine and butorphanol may be potentially detrimental we could find no definite superiority of one versus the others.

Adolescent↗
PubMed2005

Effects of acepromazine on pulmonary gas exchange and circulation during sedation and dissociative anaesthesia in horses.

OBJECTIVE: To study pulmonary gas exchange and cardiovascular responses to sedation achieved with romifidine and butorphanol (RB) alone, or combined with acepromazine, and during subsequent tiletamine-zolazepam anaesthesia in horses. ANIMALS: Six (four males and two females) healthy Standardbred trotters aged 3-12 years; mass 423-520 kg. STUDY DESIGN: Randomized, cross-over, experimental study. MATERIALS AND METHODS: Horses were anaesthetized on two occasions (with a minimum interval of 1 week) with intravenous (IV) tiletamine-zolazepam (Z; 1.4 mg kg(-1)) after pre-anaesthetic medication with IV romifidine (R; 0.1 mg kg(-1)) and butorphanol (B; 25 microg kg(-1) IV). At the first trial, horses were randomly allocated to receive (protocol ARBZ) or not to receive (protocol RBZ) acepromazine (A; 35 microg kg(-1)) intramuscularly (IM) 35 minutes before induction of anaesthesia. Each horse was placed in left lateral recumbency and, after tracheal intubation, allowed to breathe room air spontaneously. Respiratory and haemodynamic variables and ventilation-perfusion (; multiple inert gas elimination technique) ratios were determined in the conscious horse, after sedation and during anaesthesia. One- and two-way repeated-measures anova were used to identify within- and between-technique differences, respectively. RESULTS: During sedation with RB, arterial oxygen tension (PaO(2)) decreased compared to baseline and increased mismatch was evident; there was no O(2) diffusion limitation or increase in intrapulmonary shunt fraction identified. With ARB, PaO(2) and remained unaffected. During anaesthesia, intrapulmonary shunt occurred to the same extent in both protocols, and mismatching increased. This was less in the ARBZ group. Arterial O(2) tension decreased in both protocols, but was lower at 25 and 35 minutes of anaesthesia in RBZ than in ARBZ. During sedation, heart rate (HR) and cardiac output (Qt) were lower while arterial-mixed venous oxygen content differences and haemoglobin concentrations were higher in RBZ compared with ARBZ. Total systemic vascular resistance, mean systemic, and mean pulmonary arterial pressures were higher during anaesthesia with RBZ compared to ARBZ. CONCLUSIONS AND CLINICAL RELEVANCE: Acepromazine added to RB generally improved haemodynamic variables and arterial oxygenation during sedation and anaesthesia. Arterial oxygenation was impaired as a result of increased shunt and mismatch during anaesthesia, although acepromazine treatment reduced disturbances and falls in PaO(2) to some extent. Haemodynamic variables were closer to baseline during sedation and anaesthesia when horses received acepromazine. Acepromazine may confer advantages in healthy normovolaemic horses.

Acepromazine↗
PubMedDate not supplied

Comparison of intra-articular and epidural morphine for analgesia following stifle arthrotomy in dogs.

We prospectively studied 18 dogs that presented for exploratory stifle arthrotomy, with or without meniscectomy, and lateral extracapsular stabilization as a result of cranial cruciate ligament rupture. Dogs were premedicated with acepromazine, induced with thiopental, and maintained with halothane in oxygen. Preoperatively, dogs were assigned to one of three groups. Group 1 (n = 6) received intra-articular morphine (0.1 mg/kg diluted in 1 mL/10 kg body weight of saline) and epidural saline (1 mL/5 kg body weight saline plus the volume of saline representing 0.1 mg/kg of morphine). Group 2 (n = 6) received intra-articular saline (1 mL/10 kg body weight of saline plus the volume of saline representing 0.1 mg/kg of morphine) and epidural saline (1 mL/5 kg body weight saline plus the volume of saline representing 0.1 mg/kg of morphine). Group 3 (n = 6) received intra-articular saline (1 mL/10 kg body weight of saline plus the volume of saline representing 0.1 mg/kg of morphine) and epidural morphine (0.1 mg/kg of morphine diluted in 1 mL/5 kg body weight saline). The efficacy of each analgesia regimen was evaluated for 6 hours postoperatively with a pain score based on subjective and objective variables. Serum cortisol and blood glucose concentrations were measured. Butorphanol was used to provide analgesia as needed based on a predetermined maximum pain score. Supplemental analgesics were required postoperatively every 2 to 3 hours for 6 hours in all dogs that did not initially receive analgesics (group 2). Pain scores were significantly lower in dogs administered morphine intra-articularly (group 1) and epidurally (group 3) at 30 minutes and 30, 120, and 360 minutes, respectively, compared with dogs that did not initially receive analgesics (group 2). One dog in group 1 and one dog in group 3 required supplemental analgesia with butorphanol. There was no difference between analgesia produced by intra-articular morphine compared with that of epidural morphine. Side effects after intra-articular or epidural morphine were not observed. Intra-articular administration of morphine can produce effective analgesia in dogs comparable with that produced by epidural administration of morphine.

Analgesia↗
PubMed2003

The competitive N-methyl-D-aspartate receptor antagonist (-)-6-phosphonomethyl-deca-hydroisoquinoline-3-carboxylic acid (LY235959) potentiates the antinociceptive effects of opioids that vary in efficacy at the mu-opioid receptor.

(-)-6-Phosphonomethyl-deca-hydroisoquinoline-3-carboxylic acid (LY235959) is a competitive N-methyl-D-aspartate receptor antagonist shown to prevent the development of tolerance to the antinociceptive effects of morphine in rodents. Although administration of LY235959 alone generally does not produce antinociception, LY235959 potentiates the antinociceptive effects of morphine in squirrel monkeys. The present study was designed to determine whether LY235959 would potentiate the acute antinociceptive effects of morphine as well those of the opioid receptor agonists l-methadone, levorphanol, butorphanol, and buprenorphine. A squirrel monkey titration procedure was used in which shock (delivered to the tail) increased in intensity every 15 s (0.01-2.0 mA) in 30 increments. Five lever presses during any given 15-s shock period (fixed ratio 5) produced a 15-s shock-free period after which shock resumed at the next lower intensity. Morphine (0.3-3.0 mg/kg i.m.), l-methadone (0.1-0.56 mg/kg i.m.), levorphanol (0.1-1.0 mg/kg i.m.), butorphanol (1.0-10 mg/kg i.m.), and buprenorphine (0.01-0.03 mg/kg i.m.), but not LY235959 (0.1-1.0 mg/kg i.m.), dose and time dependently increased the intensity below which monkeys maintained shock 50% of the time (median shock level, MSL). LY235959 dose dependently potentiated the effect of each opioid agonist on MSL when concurrently administered to monkeys. Although LY235959 potentiated the antinociceptive effect of each opioid examined in a statistically significant manner, LY235959 seemed more potent and effective when combined with higher efficacy opioids. The present data suggest that the N-methyl-D-aspartate antagonist, LY235959, can potentiate the antinociceptive effects of a range of opioid receptor agonists independently of nonspecific motor effects.

Animals↗
PubMed1997

Down-regulation of mu-opioid receptor by full but not partial agonists is independent of G protein coupling.

In C6 glial cells stably expressing rat mu-opioid receptor, opioid agonist activation is negatively coupled to adenylyl cyclase through pertussis toxin-sensitive G proteins. In membranes, [D-Ala2, N-MePhe4,Gly-ol5]enkephalin (DAMGO) increases guanosine-5'-O-(3-[35S]thio)triphosphate (GTP[gamma-35S]) binding by 367% with an EC50 value of 28 nM. Prolonged exposure to agonists induced desensitization of the receptor as estimated by a reduction in the maximal stimulation of GTP[gamma-35S] binding by DAMGO and rightward shifts in the dose-response curves. In cells treated with 10 microM concentrations of etorphine, DAMGO, beta-endorphin, morphine, and butorphanol, DAMGO-stimulated GTP[gamma-35S] binding was 58%, 149%, 205%, 286%, and 325%, respectively. Guanine nucleotide regulation of agonist binding was correspondingly lower in membranes from tolerant cells. Furthermore, chronic opioid treatment increased forskolin-stimulated adenylyl cyclase activity, and potency of DAMGO to inhibit cAMP accumulation was lower in morphine- and DAMGO-tolerant cells (EC50 = 55 and 170 nM versus 18 nM for control). Chronic treatment with agonists reduced [3H]DAMGO binding in membranes with the rank order of etorphine > DAMGO = beta-endorphin > morphine > butorphanol, and the affinity of DAMGO in alkaloid- but not peptide-treated membranes was significantly lower in comparison with control. Pertussis toxin treatment of the cells before agonist treatment did not prevent the down-regulation by full agonists; DAMGO and etorphine exhibited approximately 80% internalization, whereas the ability of partial agonists was greatly impaired. In addition to establishing this cell line as a good model for further studies on the mechanisms of opioid tolerance, these results indicate important differences in the inactivation pathways of receptor triggered by full and partial agonists.

Adenylyl Cyclases↗
PubMed1983

Comparative effects and analgesic efficacy of the agonist-antagonist opioids.

Pentazocine, butorphanol, nalbuphine, and buprenorphine are mixed agonist-antagonist opioids that are effective analgesics, with less abuse potential than the agonists morphine, propoxyphene, and codeine. The dual properties of the agonist-antagonists are largely explained by their varying actions at the postulated three types (mu, chi, and sigma) of opioid receptors. The agonist-antagonists are classified as either morphine-like or nalorphine-like, based on their acute effects and withdrawal symptoms after chronic dosing. Buprenorphine is morphine-like, while the other drugs are nalorphine-like. These agents vary in the duration of analgesia, with pentazocine having a mean action of three hours and buprenorphine greater than six hours. The hemodynamic effects of nalbuphine and buprenorphine generally resemble those of morphine, while pentazocine and butorphanol increase cardiac workload, blood pressure, and pulmonary artery pressure. The agonist-antagonists have ceilings for respiratory depression, whereas the agonists produce dose-dependent depression. Agonist-antagonists generally produce less increase in biliary ductal pressure than does morphine. The major clinical limitations are that agonist-dependent patients may experience unpleasant subjective effects, when treated with the agonist-antagonists, and the nalorphine-like agents can produce psychotomimetic effects. More clinical experience is needed to rank the abuse potential within this group of opioids. The newer agents are being studied for oral use in acute and chronic pain.

Analgesics↗
PubMed2006

Pharmacological profiles of opioid ligands at kappa opioid receptors.

BACKGROUND: The aim of the present study was to describe the activity of a set of opioid drugs, including partial agonists, in a human embryonic kidney cell system stably expressing only the mouse kappa-opioid receptors. Receptor activation was assessed by measuring the inhibition of cyclic adenosine mono phosphate (cAMP) production stimulated by 5 microM forskolin. Intrinsic activities and potencies of these ligands were determined relative to the endogenous ligand dynorphin and the kappa agonist with the highest intrinsic activity that was identified in this study, fentanyl. RESULTS: Among the ligands studied naltrexone, WIN 44,441 and dezocine, were classified as antagonists, while the remaining ligands were agonists. Intrinsic activity of agonists was assessed by determining the extent of inhibition of forskolin-stimulated cAMP production. The absolute levels of inhibition of cAMP production by each ligand was used to describe the rank order of intrinsic activity of the agonists; fentanyl = lofentanil > or = hydromorphone = morphine = nalorphine > or = etorphine > or = xorphanol > or = metazocine > or = SKF 10047 = cyclazocine > or = butorphanol > nalbuphine. The rank order of affinity of these ligands was; cyclazocine > naltrexone > or = SKF 10047 > or = xorphanol > or = WIN 44,441 > nalorphine > butorphanol > nalbuphine > or = lofentanil > dezocine > or = metazocine > or = morphine > hydromorphone > fentanyl. CONCLUSION: These results elucidate the relative activities of a set of opioid ligands at kappa-opioid receptor and can serve as the initial step in a systematic study leading to understanding of the mode of action of these opioid ligands at this receptor.

Analgesics, Opioid↗
PubMed2002

Effects of preoperative administration of ketoprofen on whole blood platelet aggregation, buccal mucosal bleeding time, and hematologic indices in dogs undergoing elective ovariohysterectomy.

OBJECTIVE: To determine effects of preoperative administration of ketoprofen on whole blood platelet aggregation, buccal mucosal bleeding time, and hematologic indices in dogs after elective ovariohysterectomy. DESIGN: Randomized, masked clinical trial. ANIMALS: 22 healthy dogs. PROCEDURE: 60 minutes before induction of anesthesia, 11 dogs were given 0.9% NaCl solution (control), and 11 dogs were given ketoprofen (2 mg/kg [0.9 mg/lb], IM). Thirty minutes before induction of anesthesia, glycopyrrolate (0.01mg/kg [0.005 mg/lb]), acepromazine (0.05 mg/kg [0.02 mg/lb]), and butorphanol (0.2 mg/kg 10.09 mg/lb]) were given IM to all dogs. Anesthesia was induced with thiopental (5 to 10 mg/kg [2.3 to 4.5 mg/lb], IV) and maintained with isoflurane (1 to 3%). Ovariohysterectomy was performed and butorphanol (0.1 mg/kg [0.05 mg/lb], IV) was given 15 minutes before completion of surgery. Blood samples for measurement of variables were collected at intervals before and after surgery. RESULTS: In dogs given ketoprofen, platelet aggregation was decreased 95 +/- 10% and 80 +/- 35% (mean +/- SD) immediately after surgery and 24 hours after surgery, respectively, compared with preoperative values. At both times, mean values in dogs given ketoprofen differed significantly from those in control dogs. Significant differences between groups were not observed for mucosal bleeding time or hematologic indices. CONCLUSIONS AND CLINICAL RELEVANCE: Preoperative administration of ketoprofen inhibited platelet aggre gation but did not alter bleeding time. Ketoprofen can be given before surgery to healthy dogs undergoing elective ovariohysterectomy, provided that dogs are screened for potential bleeding problems before surgery and monitored closely after surgery.

Animals↗
PubMed2002

Effects of preoperative administration of ketoprofen on anesthetic requirements and signs of postoperative pain in dogs undergoing elective ovariohysterectomy.

OBJECTIVE: To determine the effects of preoperative administration of ketoprofen on anesthetic requirements and signs of postoperative pain in dogs undergoing elective ovariohysterectomy. DESIGN: Randomized, controlled clinical trial. ANIMALS: 22 clinically normal client-owned dogs. PROCEDURE: 60 minutes before induction of anesthesia, 11 dogs were given ketoprofen (2 mg/kg [0.9 mg/lb], i.m.), and the other 11 were given saline (0.9% NaCl) solution. Dogs were premedicated with glycopyrrolate, acepromazine, and butorphanol and anesthetized with thiopental; anesthesia was maintained with isoflurane. Ovariohysterectomy was performed by an experienced surgeon, and butorphanol was given 15 minutes before completion of the procedure. Objective behavioral scores and numerical pain scores at rest and with movement were recorded every 2 hours for 12 hours after surgery and then every 4 hours for an additional 12 hours. RESULTS: Preoperative administration of ketoprofen did not reduce the dose of thiopental required to induce anesthesia or the end-tidal concentration of isoflurane required to maintain anesthesia. Activity levels and median objective behavioral scores were significantly higher 4 and 6 hours after surgery in dogs given ketoprofen than in dogs given saline solution. However, mean numerical pain scores in dogs given ketoprofen were not significantly different from scores for dogs given saline solution at any time. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that preoperative administration of ketoprofen does not reduce anesthetic requirements in dogs undergoing elective ovariohysterectomy but may reduce signs of pain after surgery. Results also suggest that the objective behavioral score may be a more sensitive measure of acute postoperative pain than traditional numerical pain scores.

Animals↗
PubMedDate not supplied

Morbidity and mortality associated with anesthetic management in small animal veterinary practice in Ontario.

During 1993, 66 small animal practices participated in a prospective study to evaluate the incidence and details of anesthetic-related morbidity and mortality. Considering a total of 8,087 dogs and 8,702 cats undergoing anesthesia, the incidences of complications were 2.1% and 1.3%, respectively. Death occurred in 0.11% and 0.1% of cases, respectively. Logistic regression models were developed and showed that a significant odds ratio (OR) of complications in dogs was associated with xylazine (OR, 91.5); heart rate monitoring (OR, 3.2); American Society of Anesthesiologists (ASA) 3, 4, or 5 classification (OR, 2.5); isoflurane (OR, 2.4); butorphanol (OR, 0.35); technician presence (OR, 0.26); acepromazine (OR, 0.24); ketamine (OR, 0.21); and mask induction (OR, 0.2). Complications in cats were associated with ASA 3, 4, or 5 classification (OR, 5.3); diazepam (OR, 4.1); intubation (OR, 1.7); butorphanol (OR, 0.45); and ketamine (OR, 0.17). Cardiac arrest in dogs was associated with xylazine (OR, 43.6) and ASA 3, 4, or 5 classification (OR, 7.1). Cardiac arrest in cats was associated with ASA 3, 4, or 5 classification (OR, 21.6) and technician presence (OR, 0.19). This paper reports the incidences of complications and cardiac arrest in small animal practice and identifies common complications and factors that may influence anesthetic morbidity and mortality. This information may be useful in comparing anesthetic management practices.

Anesthesia↗
PubMed1998

Delta opioid-like discriminative stimulus effects of mu opioids in pigeons discriminating the delta opioid BW373U86 from saline.

The purpose of this experiment was to examine the substitution patterns produced by opioids with activity at the mu receptor in pigeons trained to discriminate the delta opioid BW373U86 from saline. A low dose of naltrindole (0.1 mg/kg) produced at least a 16-fold rightward shift in the dose-effect curve for the stimulus effects of BW373U86 (yielding a pK(B) = 7.9), whereas a relatively high dose of naloxone (1.0 mg/kg) produced only a 2-fold rightward shift (yielding a pK(B) = 5.6). The delta opioid SNC80 and the mixed mu/kappa opioids ethylketocyclazocine and ketocyclazocine substituted completely for the BW373U86 stimulus. Various opioids with activity at the mu receptor (levallorphan, [-]-cyclazocine, [-]-n-allylnormetazocine, morphine, butorphanol, nalbuphine, [+]-propoxyphene, etorphine, fentanyl) substituted partially for the BW373U86 stimulus. There was no relationship between the substitution patterns produced by these opioids and their relative intrinsic efficacy at the mu receptor, their relative selectivity for the mu receptor or their relative affinity for the delta receptor. Naloxone (1.0 mg/kg) was considerably more effective than naltrindole (0.1 mg/kg) in antagonizing the substitution patterns produced by etorphine, ethylketocyclazocine, ketocyclazocine and butorphanol, suggesting that these effects were not mediated by activity at the delta receptor. There was no evidence that these opioids antagonized the BW373U86 stimulus, suggesting that they were not functioning as low efficacy agonists at the delta receptor. The kappa opioids bremazocine and U50,488, as well as the non-opioids cocaine and pentobarbital, failed to produce appreciable levels of BW373U86 responding. The present findings indicate that in pigeons mu opioids most likely produce delta-like discriminative stimulus effects by activation of mu rather than delta or kappa receptors.

Animals↗
PubMed1999

Changes in cortisol concentration in response to stress and postoperative pain in client-owned cats and correlation with objective clinical variables.

OBJECTIVE: To identify clinical variables that indicate postoperative pain in cats after ovariohysterectomy in a veterinary hospital setting. ANIMALS: 40 cats. PROCEDURE: Cats were anesthetized and ovariohysterectomized by senior veterinary students. Butorphanol (0.1 mg/kg [n = 20] or 0.3 mg/kg [20] of body weight) was administered IM after surgery. Blood samples were obtained before, during, and after the anesthetic period for measurements of PCV and blood glucose and cortisol concentrations. Clinical variables measured included heart rate, systolic blood pressure, respiratory rate, and rectal temperature. Data for these variables were compared with changes in cortisol concentrations and with similar data-which was used as historical control data-obtained from 20 cats in another study (10 that had been ovariohysterectomized but had not received butorphanol and 10 that had only been anesthetized). RESULTS: Surgical durations were longer in this study, and cats had higher cortisol concentrations, compared with historical control cats. Objective clinical variables did not consistently correlate with changes in cortisol concentration. CONCLUSIONS: Cortisol concentration increased in response to surgical stress and pain. This response was greater in cats in which duration of surgery was longer. CLINICAL RELEVANCE: The objective clinical variables evaluated in this study were not consistent indicators of pain in an uncontrolled, clinical situation.

Animals↗
PubMed1999

Sensitivity to the discriminative stimulus and antinociceptive effects of mu opioids: role of strain of rat, stimulus intensity, and intrinsic efficacy at the mu opioid receptor.

Effects of low (butorphanol, nalbuphine)-, intermediate (buprenorphine)-, and high (morphine, levorphanol)-efficacy mu opioids were examined in F344, Sprague-Dawley (SD), Long-Evans (LE), and Lewis rats using a tail withdrawal and a drug discrimination procedure. In the tail withdrawal procedure using low (50 degrees C), intermediate (52 degrees C), and high (56 degrees C) water temperatures, morphine and levorphanol produced maximal effects in each of the strains and were most potent in F344 and least potent in Lewis. Similar differences across strains were obtained with buprenorphine, and at the high intensity, maximal effects were not obtained in Lewis. At the low intensity, butorphanol produced maximal effects in F344 and SD at relatively low doses, half-maximal effects in LE at very high doses, and no effect in Lewis. Nalbuphine produced near maximal effects in F344 and SD when tested with the low intensity and no effect in the LE and Lewis. Similar results were obtained at the intermediate intensity for these opioids, although the absolute level of antinociception was lower. These results indicate that there are profound differences to the antinociceptive effects of mu opioids across rat strains. The magnitude of these differences increased with higher stimulus intensities and when tested with lower efficacy opioids. In rats trained to discriminate morphine (3.0 or 5.6 mg/kg) from water, there were no consistent differences across rat strains to the effects of these mu opioids. Possible reasons for differences between the results obtained in the tail withdrawal and drug discrimination procedures are discussed.

Analgesics, Opioid↗