During the breeding season, the effect of constant administration of an agonist analog of gonadotropin-releasing hormone (GnRH; goserelin acetate) on reproductive activity of mares was determined. Twenty-four mares undergoing estrous cycles were allocated at random to 6 groups (n = 4/group) and, on May 29 (day 0), received no treatment (group 1, controls), 120 micrograms (group 2), 360 micrograms (group 3), 600 micrograms (group 4), or 1,200 micrograms (group 5) of GnRH agonist/d for 28 days via a depot implanted subcutaneously. The final group of mares (group 6) was treated with 120 miocrograms of GnRH agonist/d for 84 days (3 occasions at 28-day intervals). During a pretreatment period (April 19 to May 29) and for 90 days after initiation of GnRH agonist treatment, follicular development and ovulation were monitored by transrectal ultrasonography of the reproductive tract at 2- to 3-day intervals. On each occasion a blood sample was collected for determination of luteinizing hormone (LH) and progesterone. Estrous behavior was monitored by teasing of mares with a stallion. Initiation of agonist treatment was random, relative to the stage of the estrous cycle, and all mares ovulated within 11 days before or after implantation. in 3 of 4 nontreated control mares, estrous cycles were observed throughout the study, with interovulatory intervals ranging from 18 to 26 days. In the remaining mare, concentration of progesterone was high after asynchronous double ovulation during the pretreatment period, suggestive of persistent corpus luteum. In group-2 mares, ovulation occurred in all mares 7 days before and 2 days after initiation of treatment; however, the next anticipated ovulation was delayed in 3 of 4 mares (interovulatory interval, 33 to 70 days). Estrous cycles were not disrupted in the remaining mare. At higher doses (groups 3-5), 1 mare each from groups 3 and 5 ovulated between days 0 and 2 of treatment initiation.

Hypoxia is a common pathological condition after spinal cord injury. Oestrogen-related receptor alpha (ERRα), as a key regulator of energy metabolism and mitochondrial functions, plays an important role in maintaining cell homeostasis. However, its role in hypoxic spinal microglia has not been fully elaborated. This study investigated the receptor’s activity when these cells are hypoxic and used as an in vitro model. In this study, microglia (BV2) were exposed to cobalt chloride as a hypoxic model, and the inverse agonist of ERRα, XCT790, and pyrido[1,2-α]-pyrimidin-4-one were used to regulate the expression of the receptor to explore the ERRα-related mechanisms involved in hypoxic spinal cord injury (SCI). ERRα promoted autophagy in BV2 cells and inhibited the activation of the p38 mitogen-activated protein kinase (MAPK) pathway and the expression of anti-inflammatory factors under hypoxic conditions. It also promoted the expression of fibronectin type III domain containing protein 5 (FNDC5). When a hypoxic SCI occurs, ERRα may maintain the homeostasis of spinal cord nerve cells by regulating autophagy and the p38MAPK/nuclear factor-kappa B cell and FNDC5/brain-derived neurotrophic factor signalling pathways, which are beneficial to the recovery of these cells.

Objective-To evaluate the duration of effects on movement patterns of horses after sedation with equipotent doses of xylazine hydrochloride, detomidine hydrochloride, or romifidine hydrochloride and determine whether accelerometry can be used to quantify differences among drug treatments. Animals-6 healthy horses. Procedures-Each horse was injected IV with saline (0.9% NaCl) solution (10 mL), xylazine diluted in saline solution (0.5 mg/kg), detomidine diluted in saline solution (0.01 mg/kg), or romifidine diluted in saline solution (0.04 mg/kg) in random order. A triaxial accelerometric device was used for gait assessment 15 minutes before and 5, 15, 30, 45, 60, 75, 90, 105, and 120 minutes after each treatment. Eight variables were calculated, including speed, stride frequency, stride length, regularity, dorsoventral power, propulsive power, mediolateral power, and total power; the force of acceleration and 3 components of power were then calculated. Results-Significant differences were evident in stride frequency and regularity between treatments with saline solution and each α2-adrenoceptor agonist drug; in speed, dorsoventral power, propulsive power, total power, and force values between treatments with saline solution and detomidine or romifidine; and in mediolateral power between treatments with saline solution and detomidine. Stride length did not differ among treatments. Conclusions and Clinical Relevance-Accelerometric evaluation of horses administered α2-adrenoceptor agonist drugs revealed more prolonged sedative effects of romifidine, compared with effects of xylazine or detomidine. Accelerometry could be useful in assessing the effects of other sedatives and analgesics. Accelerometric data may be helpful in drug selection for situations in which a horse's balance and coordination are important.

Objective: To evaluate platelet-neutrophil aggregate (PNA) formation and neutrophil shape as indicators of neutrophil activation in dogs with systemic inflammatory diseases and after blood sample incubation with various platelet and neutrophil agonists. Animals: 20 dogs with systemic inflammatory response syndrome (SIRS) and 10 healthy Beagles. Procedures: Neutrophils were isolated from blood samples directly after blood sample collection and after incubation of blood samples with phorbol myristate acetate, collagen, adenosine diphosphate, epinephrine, or various concentrations of lipopolysaccharide or arachidonic acid. CD61+ neutrophils as an indicator of PNA formation were evaluated, and neutrophil size and granularity were assessed via flow cytometry. Results: Dogs with SIRS had more PNA formation, larger neutrophil size, and less granularity relative to control dogs, but no differences were evident when these dogs were grouped by whether they had sepsis (n = 6) or disseminated intravascular coagulation (12). A significant increase in PNA formation occurred after neutrophil incubation with all agonists, and incubation with phorbol myristate acetate elicited the strongest response. Neutrophils increased in size and decreased in granularity after incubation with all agonists except epinephrine. Incubation with lipopolysaccharide or arachidonic acid resulted in a dose-dependent effect on PNA formation and neutrophil shape. Conclusions and Clinical Relevance: SIRS appeared to increase the degree of PNA formation and neutrophil shape change. Similar changes after neutrophil incubation with platelet agonists suggested that platelet activation has a role in PNA formation. Additional studies are necessary to determine the clinical importance and diagnostic value of PNA formation in dogs with SIRS and sepsis.

Chickens (n = 18), ranging in age from 30 to 50 weeks and in body weight from 1.1 to 2.1 kg, were anesthetized with isoflurane. Ventilation was controlled, and temperature was maintained at 40.1 +/- 1.0 C. The minimal anesthetic concentration (MAC) of isoflurane was determined by use of a bracketing technique based on purposeful movement in response to a toe clamp. After determining isoflurane MAC in triplicate, birds were given a mu-opioid agonist (morphine, n = 9) or a kappa-opioid agonist (U50488H, n = 9). Determination of MAC was repeated after each IV administration of agonist in progressive doses of 0.1, 1.0, and 3.0 mg/kg of body weight. Heart rate and mean arterial blood pressure (MAP) were recorded immediately before and after each injection. Control MAC (mean +/- SEM) was 1.24 +/- 0.05% and 1.05 +/- 0.03% for the mu- and kappa-opioid agonist groups, respectively. Morphine and U50488H caused a dose-dependent decrease in isoflurane MAC in all birds. Reduction of MAC from control (mean +/- SEW) was 15.1 +/- 2.7, 39.7 +/- 3.1, and 52.4 +/- 4.0% after the 3 successive doses of morphine and was 13.3 +/- 3.0, 27.6 +/- 3.3, and 40.8 +/- 3.8% after U50488H was given. Each opioid injection resulted in significant (P less than or equal to 0.05, repeated measures ANOVA) lowering of MAC. Heart rate and MAP did not change significantly (P less than or equal to 0.05, paired Student's t-test) after any dose of opioid. In conclusion, morphine or U50488H decreased isoflurane MAC in dose-dependent manner without significant effect on heart rate and MAP.

Urethral smooth muscle tone in response to treatment with phenylephrine, a selective alpha 1-adrenergic receptor agonist, and prazosin a selective alpha 1-adrenergic receptor antagonist, was evaluated in 12 anesthetized healthy adult sexually intact male cats. Intravenous administration of prazosin (20 to 30 micrograms/kg of body weight) decreased the average preprostatic and prostatic intraurethral pressure, compared with baseline and postphenylephrine (20 to 30 micrograms(kg) administration, values. Neither prazosin nor phenylephrine administration had an effect on functional urethral length. Results have implications for the pharmacologic management of lower urinary tract disorders in male cats.

OBJECTIVE To quantify plasma fentanyl concentrations (PFCs) and evaluate antinociceptive and respiratory effects following application of transdermal fentanyl patches (TFPs) and assess cerebrospinal μ-opioid receptor mRNA expression in ball pythons (compared with findings in turtles). ANIMALS 44 ball pythons (Python regius) and 10 turtles (Trachemys scripta elegans). PROCEDURES To administer 3 or 12 μg of fentanyl/h, a quarter or whole TFP (TFP-3 and TFP-12, respectively) was used. At intervals after TFP-12 application in snakes, PFCs were measured by reverse-phase high-pressure liquid chromatography. Infrared heat stimuli were applied to the rostroventral surface of snakes to determine thermal withdrawal latencies after treatments with no TFP (control [n = 16]) and TFP-3 (8) or TFP-12 (9). Breathing frequency was measured in unrestrained controls and TFP-12–treated snakes. μ-Opioid receptor mRNA expression in brain and spinal cord tissue samples from snakes and turtles (which are responsive to μ-opioid receptor agonist drugs) were quantified with a reverse transcription PCR assay. RESULTS Mean PFCs were 79, 238, and 111 ng/mL at 6, 24, and 48 hours after TFP-12 application, respectively. At 3 to 48 hours after TFP-3 or TFP-12 application, thermal withdrawal latencies did not differ from pretreatment values or control treatment findings. For TFP-12–treated snakes, mean breathing frequency significantly decreased from the pretreatment value by 23% and 41% at the 24- and 48-hour time points, respectively. Brain and spinal cord tissue μ-opioid receptor mRNA expressions in snakes and turtles did not differ. CONCLUSIONS AND CLINICAL RELEVANCE In ball pythons, TFP-12 application resulted in high PFCs, but there was no change in thermal antinociception, indicating resistance to μ-opioid-dependent antinociception in this species.

OBJECTIVE To assess the effect of decreased platelet and WBC counts on platelet aggregation as measured by a multiple-electrode impedance aggregometer in dogs. ANIMALS 24 healthy dogs. PROCEDURES From each dog, 9 mL of blood was collected into a 10-mL syringe that contained 1 mL of 4% sodium citrate solution to yield a 10-mL sample with a 1:9 citrate-to-blood ratio. Each sample was then divided into unmanipulated and manipulated aliquots with progressively depleted buffy-coat fractions such that 2 to 3 blood samples were evaluated per dog. The Hct for manipulated aliquots was adjusted with autologous plasma so that it was within 2% of the Hct for the unmanipulated aliquot for each dog. All samples were analyzed in duplicate with a multiple-electrode impedance aggregometer following the addition of ADP as a platelet agonist. The respective effects of platelet count, plateletcrit, Hct, and WBC count on platelet aggregation area under the curve (AUC), aggregation, and velocity were analyzed with linear mixed models. RESULTS WBC count was positively associated with platelet AUC, aggregation, and velocity; blood samples with leukopenia had a lower AUC, aggregation, and velocity than samples with WBC counts within the reference range. Platelet count, plateletcrit, and Hct did not have an independent effect on AUC, aggregation, or velocity. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that WBC count was positively associated with platelet aggregation when ADP was used to activate canine blood samples for impedance aggregometry. That finding may be clinically relevant and needs to be confirmed by in vivo studies.

Objective: To evaluate the role of the semitendinosus muscle in stabilization of the canine stifle joint. Sample: Left stifle joints collected from cadavers of 8 healthy Beagles. Procedures: Left hind limbs, including the pelvis, were collected. To mimic the tensile force of the quadriceps, gastrocnemius, and semitendinosus muscles, wires were placed under strain between the ends of each muscle. A sensor was used to measure the tensile force in each wire. Specimens were tested in the following sequence: cranial cruciate ligament (CrCL) intact, CrCL transected, released (tensile force of semitendinosus muscle was released in the CrCL-transected stifle joint), and readjusted (tensile force of semitendinosus muscle was reapplied in the CrCL-transected stifle joint). Specimens were loaded at 65.3% of body weight, and tensile force in the wires as well as the cranial tibial displacement were measured. Results: Tensile force for the CrCL-transected condition increased significantly, compared with that for the CrCL-intact condition. Mean ± SD cranial tibial displacement for the CrCL-transected condition was 2.1 ± 1.3 mm, which increased to 7.2 ± 2.3 mm after release of the tensile force in the semitendinosus muscle. Conclusions and Clinical Relevance: Results supported the contention that the semitendinosus muscle is an agonist of the CrCL in the stifle joint of dogs. Moreover, the quadriceps and gastrocnemius muscles may be antagonists of the CrCL. These findings suggested that the risk of CrCL rupture may be increased by diseases (such as cauda equina syndrome) associated with a decrease in activity of the semitendinosus muscle.

Objective-To determine the presence of adenosine receptor subtypes A1 and A2a in equine forebrain tissues and to characterize the interactions of caffeine and its metabolites with adenosine receptors in the CNS of horses. Sample Population-Brain tissue specimens obtained during necropsy from 5 adult male research Procedures-Membrane-enriched homogenates from cerebral cortex and striatum were evaluated by radioligand binding assays with the A1-selective ligand [3H]DPCPX and the A2a-selective ligand [3H]ZM241385. Functional responses to adenosine receptor agonists and antagonists were determined by a nucleotide exchange assay using [35S]-guanosine 5'-(γ-thio) triphosphate [35S]GTPγS). Results-Saturable high affinity [3H]DPCPX binding (A1) sites were detected in cerebral cortex and striatum, whereas high-affinity [3H]ZM241385 binding (A2a) sites were detected only in striatum. Caffeine and related methylxanthines had similar binding affinities at A1 and A2a sites with rank orders of drug binding affinities (theophylline > paraxanthine ≥ caffeine >> theobromine) similar to other species. [35S]GTPγS exchange revealed that caffeine and its metabolites act as pure adenosine receptor antagonists at concentrations that correspond to A1 and A2a receptor binding affinities. Conclusions and Clinical Relevance-Results of our study affirm the presence of guanine nucleotide binding protein linked adenosine receptors (ie, high-affinity A1 and A2a adenosine receptors) in equine forebrain tissues and reveal the antagonistic actions by caffeine and several biologically active caffeine metabolites. Antagonism of adenosine actions in the equine CNS by these stimulants may be responsible for some central actions of methylxanthine drugs, including motor stimulation and enhanced racing performance.