THE PULMONARY AND METABOLIC EFFECTS OF SUSPENSION BY THE FEET COMPARED WITH LATERAL RECUMBENCY IN IMMOBILIZED BLACK RHINOCEROSES (DICEROS BICORNIS) CAPTURED BY AERIAL DARTING.

Aerial translocation of captured black rhinoceroses (Diceros bicornis) has been accomplished by suspending them by their feet. We expected this posture would compromise respiratory gas exchange more than would lateral recumbency. Because white rhinoceroses (Ceratotherium simum) immobilized with etorphine alone are hypermetabolic, with a high rate of carbon dioxide production (VCO2), we expected immobilized black rhinoceroses would also have a high VCO2. Twelve (nine male, three female; median age 8 yr old [range: 4-25]; median weight 1,137 kg [range: 804-1,234] body weight) wild black rhinoceroses were immobilized by aerial darting with etorphine and azaperone. The animals were in lateral recumbency or suspended by their feet from a crane for approximately 10 min before data were collected. Each rhinoceros received both treatments sequentially, in random order. Six were in lateral recumbency first and six were suspended first. All animals were substantially hypoxemic and hypercapnic in both postures. When suspended by the feet, mean arterial oxygen pressure (PaO2) was 42 mm Hg, 4 mm Hg greater than in lateral recumbency (P=0.030), and arterial carbon dioxide pressure (PaCO2) was 52 mm Hg, 3 mm Hg less than in lateral recumbency (P=0.016). Tidal volume and minute ventilation were similar between postures. The mean VCO2 was 2 mL/kg/min in both postures and was similar to, or marginally greater than, VCO2 predicted allometrically. Suspension by the feet for 10 min did not impair pulmonary function more than did lateral recumbency and apparently augmented gas exchange to a small degree relative to lateral recumbency. The biological importance in these animals of numerically small increments in PaO2 and decrements in PaCO2 with suspension by the feet is unknown. Black rhinoceroses immobilized with etorphine and azaperone were not as hypermetabolic as were white rhinoceroses immobilized with etorphine.

Use of butorphanol and diprenorphine to counter respiratory impairment in the immobilised white rhinoceros (Ceratotherium simum).

Opioid-induced immobilisation results in severe respiratory impairment in the white rhinoceros. It has therefore been attempted in the field to reverse this impairment with the use of opioid agonist-antagonists, such as nalorphine, nalbuphine, butorphanol and diprenorphine; however, the efficacy of some of these treatments has yet to be determined. The efficacy of butorphanol, either alone or in combination with diprenorphine both with and without oxygen insufflation, in alleviating opioid-induced respiratory impairment was evaluated. The study was performed in two parts: a boma trial and a field trial. Rhinoceroses were immobilised specifically for the study, according to a strict protocol to minimise confounding variables. A two-way analysis of variance was used to compare the physiological responses of the rhinoceroses to the different treatments and their effects over time. The intravenous administration of butorphanol (at 3.3 mg per mg etorphine) plus diprenorphine (at 0.4 mg per mg etorphine) did not offer any advantage over butorphanol (at 15 mg per mg etorphine) alone with regard to improving PaO2, PaCO2 and respiratory rates in etorphine-immobilised white rhinoceroses. Both butorphanol + diprenorphine + oxygen and butorphanol + oxygen, at the doses used, significantly improved the etorphine-induced hypoxaemia in both boma- and field-immobilised white rhinoceroses. Clinically acceptable oxygenation in field-immobilised white rhinoceroses can be achieved by using either treatment regimen, provided that it is combined with oxygen insufflation.

Increased opioid release in specific brain areas in animals exposed to prenatal morphine and emotional stress later in life.

Prenatal morphine treatment and emotional stress both have been shown to increase sensitivity to reward-related behaviors. It has been postulated that this increased sensitivity to rewarding stimuli may be the result of an enhanced release of endogenous opioids. In the present study, in vivo autoradiography was employed to investigate the endogenous opioid release in specific brain areas in rats. Pregnant animals were exposed to morphine or saline from day 8 of gestation till birth. Development of pups was monitored and play behavior was tested on postnatal day 21. Adult rats were exposed to repeated emotional stress or control treatment for five consecutive days and tested in a small open field 5 days later. [(3)H]-Diprenorphine was injected following this test to investigate endogenous opioid release. Prenatal morphine treatment increased play behavior and endogenous opioid release in a number of cortical and subcortical brain areas after being subjected to an open field challenge later in life. Emotional stress exposure increased locomotor activity in the open field irrespective of the type of prenatal treatment and increased endogenous opioid release in some specific brain areas. It is suggested that the increased release of endogenous opioids in the substantia nigra, the piriform cortex and the septum observed after both types of treatments is related to the increased sensitivity to reward.

Opioid binding in DYT1 primary torsion dystonia: an 11C-diprenorphine PET study.

The opioid transmitters enkephalin and dynorphin are known to regulate pallidal output and consequently cortical excitability. Indeed, abnormal basal ganglia opioid transmission has been reported in several involuntary movement disorders, including levodopa-induced dyskinesias in Parkinson's disease (PD), tardive dyskinesias/dystonia, Huntington's disease, and Tourette's syndrome. Moreover, a previous 11C-diprenorphine PET study investigating levodopa-induced dyskinesias found reduced opioid receptor availability in PD with but not without dyskinesias. We wished to investigate if a similar alteration in basal ganglia opioid binding was present in DYT1 primary torsion dystonia (PTD). Regional cerebral 11C-diprenorphine binding was investigated in 7 manifesting carriers of the DYT1 gene and 15 age-matched normal controls using a region-of-interest (ROI) approach and statistical parametric mapping (SPM). No difference in regional mean 11C-diprenorphine binding was found between DYT1-PTD and controls, and no correlation between the severity of dystonia and opioid binding was seen. We conclude that aberrant opioid transmission is unlikely to be present in DYT1-PTD and altered opioid transmission is not a common mechanism underlying all disorders of involuntary movement.

Changes in respiratory function following the intramuscular administration of etorphine to boer goats (Capra hircus).

The physiological effects on respiratory function of etorphine (M99, Logos Agvet) (30 microg/kg) administered intramuscularly were determined in boer goats. The goats were habituated to the experimental procedures so that respiratory function could be determined while the animals stood quietly at rest. This enabled the physiological changes induced by etorphine to be measured and compared with those obtained before administration of the immobilising drug. The effectiveness of diprenorphine (M5050, Logos Agvet) (3 mg/l mg etorphine) as an antagonist of the physiological changes induced by the etorphine treatment was also determined. Etorphine depressed respiratory function, which resulted in a decrease in PaO2 and an increase in PaCO2. These changes were limited and occurred as a result of decreases in respiratory minute volume and alveolar minute ventilation caused by a decrease in respiratory rate. The physiological shunt fraction did not change significantly but there was a significant decrease in percentage physiological dead space ventilation. It was not possible to determine how effectively diprenorphine reversed the respiratory effects due to etorphine.

A Zoletil-Rompun mixture as an alternative to the use of opioids for immobilization of feral red deer.

Sixty chemical immobilizations of red deer (Cervus elaphus hippelaphus) have been carried out during an etho-ecological study from August 1994 to December 1996 in a 35 ha pen in the district of Nitra (Slovac Republic). Our objective was to determine the efficacy and standard dosages of Zoletil and Rompun for the immobilization of adult red deer in feral conditions as an alternative to the use of the highly toxic opioids. We therefore compared an Immobilon-Rompun combination (ImRo) with a 1:1 mixture of Zoletil and Rompun (ZoRo) as an injectable solution. Use of both combinations led to the immobilization of >92% of deer with an injection volume <3 ml. Mean (SD) dose to achieve immobilization was 35 (14) microg/kg ethorphine + 0.14 (0.056) mg/kg acepromazine + 0.36 (0.14) mg/kg xylazine compared to 1.2 (0.8) mg/kg tiletamine + 1.2 (0.8) mg/kg zolazepam + 2.3 (1.6) mg/kg xylazine. This corresponds to a volume of 1.8 (0.7) ml/100 kg body mass (BM) for ImRo (range = 1.0 to 4.6) and to 2.3 (1.6) ml/100 kg BM for ZoRo (range = 0.7 to 4.0), respectively. Heart rate, respiratory rate and oxyhaemoglobin saturation values did not differ significantly between the two groups during immobilization. Three deer (5%) died during immobilization, but fatalities could not be directly associated with the drug effect. Mean (SD) time from darting to complete immobilization was 5.5 (4.2) min for ImRo and 7.5 (6.1) min for ZoRo, respectively. Differences were not statistically significant. Anesthesia with both combinations of immobilizing agents could be reversed within 2 min using sarmazenile-yohimbine for ZoRo and diprenorphine-yohimbine for ImXy immobilizations, respectively. We conclude that the 1:1 combination of Zoletil and xylazine is a valuable alternative to the use of opioids for the immobilization of adult red deer including feral adult animals.

Chemical restraint of the Nile hippopotamus (Hippopotamus amphibius) in captivity.

This retrospective study describes 16 immobilizations performed on nine adult captive Nile hippopotamus (Hippopotamus amphibius). Animals were immobilized using intramuscular etorphine alone (1.0-5.0 micrograms/kg; n = 9) or in combination with xylazine (67-83 micrograms/kg; n = 6) or acepromazine (20 micrograms/kg; n = 1). Exact weights for the animals were unknown so drug dosages were based on estimated weights. Seven animals either were in good health or had minor or localized medical problems. Following etorphine and xylazine induction, one animal undergoing castration was anesthetized with isoflurane in oxygen delivered by endotracheal tube. Ten immobilizations occurred without complications, and eight of those procedures were rated as good or excellent. Complications, including bradypnea, cyanosis, and apnea, occurred during six immobilizations. One animal died following prolonged apnea, and the necropsy failed to find a specific cause of death. Immobilizations were reversed with diprenorphine alone (4.4-10.0 micrograms/kg; n = 13), diprenorphine (2.9 micrograms/kg) and naloxone (14.6 mu k/kg; n = 1), or naltrexone (146-180 micrograms/kg; n = 2). Mean time to reversal of immobilization for those animals given etorphine alone and reversed with diprenorphine alone was 21.6 min (n = 5). Time to reversal for the two immobilizations reversed with only naltrexone was 4 min. No renarcotizations were observed. Total doses of 2.0-6.0 mg etorphine i.m. should produce heavy sedation to surgical anesthesia in calm adult captive Nile hippopotamuses. Insufflation with oxygen during immobilization seems warranted.

11C-diprenorphine binding in Huntington's disease: a comparison of region of interest analysis with statistical parametric mapping.

We compare region of interest (ROI) analytical approaches with statistical parametric mapping (SPM) of 11C-diprenorphine positron emission tomography findings in five patients with Huntington's disease (HD) and nine age-matched controls. The ROI were placed on caudate, putamen, and an occipital reference area. Ratios of striatal-occipital uptake from averaged static images centered at 60 minutes showed a mean 20% reduction in caudate (P = 0.034) and 15% reduction in putamen (P = 0.095) receptor binding in the HD patients. Dynamic data from caudate and putamen ROI, together with a plasma tracer input function, were analyzed using spectral analysis to give regional impulse response functions. Regional data at 60 minutes after impulse showed a mean 29% decrease in caudate (P = 0.006) and 23% decrease in putamen (P = 0.029) opioid binding in the HD cohort. Parametric images of tracer binding also were produced with spectral analysis on a voxel basis. The images of the unit impulse response function at 60 minutes showed a mean 31% decrease in caudate (P = 0.005) and a 26% decrease in putamen binding (P = 0.011) in HD. The voxel-based parametric images were transformed into standard stereotactic space, and a between-group comparison (patient versus controls) was performed with SPM. This approach revealed symmetrical decreases in caudate (peak 40% decrease, z score = 4.38) and putamen opioid binding (peak 24% decrease, z score = 4.686) with additional nonhypothesized changes in cingulate, prefrontal, and thalamic areas. The significance and precision of changes measured with spectral analysis applied to dynamic data sets were superior to ROI-based ratio analysis on static images. The SPM replicated the striatal reductions in opioid binding in HD and detected additional nonpredicted changes. This study suggests that SPM is a valid alternative to conventional ROI analytical approaches for determining binding changes with positron emission tomography and may have advantages over region-based analyses in exploratory studies.

Chemical immobilisation of giraffe to facilitate short procedures.

OBJECTIVE: To describe the chemical immobilisation of giraffe (Giraffa camelopardalis) for short procedures at Taronga Zoo. DESIGN: A clinical report. ANIMALS: Five giraffe. PROCEDURE: The weight of each animal was determined and pre-immobilisation fasting, careful preparation of the site, and planing were carried out prior to each procedure. Etorphine and acetylpromazine were used as the sole immobilising agents. During immobilisation, elevation of the head and constant monitoring of the heart rate, respiratory rate and temperature were employed; blood pressure and blood oxygen saturation (SpO2) were monitored in one case 5. Intravenous fluids were administered. None of the animals was intubated, and supplemental oxygen was administered via an intranasal cannula in case 5. At the end of the procedures, diprenorphine was administered to reverse immobilisation. RESULTS: Induction times were 8 to 15 min. The mean heart rate, respiratory rate and rectal temperature were 58.6 beats per min, 12.2 breaths per min and 37.1 degrees C, respectively. SpO2 in case 5 increased to over 90% with the administration of supplemental oxygen. Recovery to standing after reversal of immobilisation was rapid (2 or 3 min) in three cases, but took 30 and 31 min in the other two. CONCLUSIONS: Successful immobilisation of giraffe relies on consideration of all variables prior to and during the procedure. Careful selection and preparation of the venue and presence of sufficient numbers of adequately trained personnel are essential. Body weight determination allows accurate calculation of immunobilising agent dose. Pre-immobilisation fasting followed by elevation of head and neck help preclude regurgitation and aspiration. Relevant vital signs monitoring, fluid replacement and oxygen supplementation promote cardiopulmonary homeostasis. Preoperative planning to ensure efficient performance of the procedure helps minimise recumbency time and increase the likelihood of a successful outcome.

Capture of wood bison (Bison bison athabascae) using carfentanil-based mixtures.

Between 1986 and 1991, 155 wood bison (Bison bison athabascae) (33 adult females, 92 adult males, twelve 6 mo-old calves, eighteen 1 to 2 mo-old calves) in the Mackenzie Bison Sanctuary, Northwest Territories, Canada, and adjacent area were captured by dart immobilization. Initial trials with carfentanil, xylazine and R51163 as immobilizing agents were conducted. Subsequently, carfentanil alone, or in combination with xylazine, was used. Small doses of xylazine were used when required to control head and hind limb movement of recumbent bison. The mean dose of carfentanil used was 7.0 micrograms/kg. Narcotic antagonists used were naltrexone, naloxone and M5050. Narcotic recycling was seen in animals treated with naloxone and low doses of naltrexone. Furthermore recycling was suspected in the deaths of several animals treated with these antagonist regimes. No recycling was seen when doses of naltrexone in excess of 90:1 naltrexone:carfentanil were used. We recommend using a naltrexone:carfentanil dose in excess of 125:1 to ensure uneventful recovery.

After chronic opioid exposure sensory neurons become supersensitive to the excitatory effects of opioid agonists and antagonists as occurs after acute elevation of GM1 ganglioside.

Mouse sensory dorsal-root ganglion (DRG) neurons chronically exposed to 1 microM D-Ala2-D-Leu5-enkephalin (DADLE) for greater than 1 week in culture become tolerant to opioid inhibitory effects, i.e. shortening of the duration of the calcium-dependent component of the action potential (APD). Acute application of higher concentrations of DADLE (ca. 10 microM) to these treated neurons not only fails to shorten the APD but, instead, generally elicits excitatory effects, i.e. prolongation of the APD. The present study shows that chronic DADLE- or morphine-treated DRG neurons also become supersensitive to the excitatory effects of opioids. Whereas nM concentrations of dynorphin(1-13) are generally required to prolong the APD of naive DRG neurons, fM levels become effective after chronic opioid treatment. Whereas 1-30 nM naloxone or diprenorphine do not alter the APD of naive DRG neurons, both opioid antagonists unexpectedly prolong the APD of most of the treated cells. Similar supersensitivity to the excitatory effects of opioid agonists and antagonists was previously observed after acute treatment of naive DRG neurons with GM1 ganglioside. Our results suggest that both chronic opioid and acute GM1 treatments of DRG neurons greatly enhance the efficacy of opioid excitatory receptor functions so that even the extremely weak agonist properties of naloxone and diprenorphine become effective in prolonging the APD of these treated cells when tested at low concentrations, whereas their antagonist properties at inhibitory opioid receptors do not appear to be altered. Furthermore, whereas cholera toxin-B subunit (CTX-B; 1-10 nM) blocks opioid-induced APD prolongation in naive DRG neurons (presumably by interfering with endogenous GM1 modulation of excitatory opioid receptors functions), even much higher concentrations of CTX-B were ineffective in chronic opioid-treated as well as acute GM1-elevated neurons. These and related data suggest that opioid excitatory supersensitivity in chronic opioid-treated DRG neurons may be due to a cyclic AMP-dependent increase in GM1 ganglioside levels. Our results may clarify mechanisms of opioid dependence and the paradoxical supersensitivity to naloxone which triggers withdrawal symptoms after opiate addiction.

[Hemodynamic effect of an opioid receptor antagonist diprenorphine in canine endotoxic shock].

The hemodynamic effect of diprenorphine (M5050) in canine endotoxic shock was studied. Mean arterial pressure, left ventricular pressure, left ventricular contractility (dp/dt max), stroke volume, and cardiac output in the endotoxin-shocked dogs were significantly improved by intravenous injection of naloxone (2 mg/kg) and intraventricular microinjection of diprenorphine (40 micrograms), but not by intravenous injection of diprenorphine. It was suggested that the site of action of diprenorphine might be in the central nervous system, and the endogenous opioid substances in the central nervous system may play a more important role in the pathogenesis of septic shock than does that in the peripheral system.

Opiate receptor binding-effect relationship: sufentanil and etorphine produce analgesia at the mu-site with low fractional receptor occupancy.

The analgesic activity of the opiate agonists etorphine and sufentanil and the antagonistic effects of diprenorphine and naloxone have been related to the occupancy of 3 classes of opiate binding sites previously defined in vivo in order to establish their pharmacological significance. Sufentanil binds specifically in vivo to the first type of site (site 1), exhibiting approximately 1100-fold selectivity over site 2, whereas etorphine displays approximately 20-fold selectivity for site 1 over site 2. Neither agonist has a measurable affinity to the third type of binding site. The binding data suggest that site 1 is analogous to the mu site previously identified in vitro. Both agonists produce analgesia in the rat tail flick test at the same low fractional occupancy of site 1 (approximately 2% at the ED50) while they display much lower and quite different occupancies at site 2. Both of the opiate antagonists naloxone and diprenorphine reduce the potency of sufentanil and etorphine by a factor of 2 at 50% occupancy of site 1 alone. These results provide strong evidence that these 4 drugs exert their effects by interaction with site 1 (mu sites) which therefore may be regarded as the receptor responsible for analgesic action in this test. The assumption of a direct relationship between antagonistic effect and fractional occupancy appears to be valid for naloxone and diprenorphine at site 1, while the agonists exert their action at a very low fractional occupancy implying a non-linear binding-effect process.

Long-acting narcotic antagonist complexes.

We evaluated the ability of close to 100 organic acids to form water-soluble salts with methadone, cyclazocine, naloxone, naltrexone and, more recently, diprenorphine. About half the acids yielded insoluble salts. Polybasic acids affording insoluble salts were evaluated for their ability to form drug:acid:metal complexes with the polyvalent metal ions, Zn++, Al+++, Mg++ and Ca++. Optimum conditions for forming complexes have been developed and the consistency of their composition has been established. Salts were analyzed spectrophotometrically for drug content, and complexes were analyzed for drug and metal content. The in vitro degree of dissociation at equilibrium was measured for the preparations suspended in a simulated physiological buffer, pH 7.3. Preparations of the narcotic antagonist drugs showing relatively low degrees of dissociation in vitro, since it early appeared that a high degree of dissociation contraindicated a prolonged duration of pharmacological action, were evaluated in mice after intramuscular administration at several dose levels by the mouse tail-flick test for the potency and duration of their morphine antagonist activity. Our most promising preparations to date, showing the most prolonged durations of action without evidence of gross toxicity, are naltrexone zinc tannate and naltrexone aluminum tannate. These are undergoing detailed evaluation as potential clinical candidates. Thus far, the most useful of several dosage forms studied is a suspension in an aluminum monostearate gel.

Long-acting narcotic antagonist complexes.

We evaluated the ability of close to 100 organic acids to form water-soluble salts with methadone, cyclazocine, naloxone, naltrexone and, more recently, diprenorphine. About half the acids yielded insoluble salts. Polybasic acids affording insoluble salts were evaluated for their ability to form drug:acid:metal complexes with the polyvalent metal ions, Zn++, Al+++, Mg++ and Ca++. Optimum conditions for forming complexes have been developed and the consistency of their composition has been established. Salts were analyzed spectrophotometrically for drug content, and complexes were analyzed for drug and metal content. The in vitro degree of dissociation at equilibrium was measured for the preparations suspended in a simulated physiological buffer, pH 7.3. Preparations of the narcotic antagonist drugs showing relatively low degrees of dissociation in vitro, since it early appeared that a high degree of dissociation contraindicated a prolonged duration of pharmacological action, were evaluated in mice after intramuscular administration at several dose levels by the mouse tail-flick test for the potency and duration of their morphine antagonist activity. Our most promising preparations to date, showing the most prolonged durations of action without evidence of gross toxicity, are naltrexone zinc tannate and naltrexone aluminum tannate. These are undergoing detailed evaluation as potential clinical candidates. Thus far, the most useful of several dosage forms studied is s suspension in an aluminum monostearate gel.