Saline-treated Cats Research Articles

Pharmacometabolomics with a combination of PLS-DA and random forest algorithm analyses reveal meloxicam alters feline plasma metabolite profiles.

Repeated administration of meloxicam to cats is often limited by the potential damage to multiple organ systems. Identifying molecules that predict the adverse effects of meloxicam would help to monitor and individualize its administration, maximizing meloxicam's beneficial effects. The objectives of this study were to (a) determine if the repeated administration of meloxicam to cats alters the plasma metabolome and (b) identify plasma metabolites that may serve to monitor during the administration of meloxicam in cats. Purpose bred young adult cats (n=12) were treated with meloxicam at 0.3mg/kg or saline subcutaneously once daily for up to 17days. An untargeted metabolomics approach was applied to plasma samples collected prior to and at designated time points after meloxicam or saline administration. To refine the discovery of biomarkers, the machine-learning algorithms, partial least squares discriminant analysis (PLS-DA) and random forest (RF), were trained and validated using a separate unrelated group of meloxicam- and saline-treated cats (n=8). A total of 74 metabolites were included in the statistical analysis. Metabolomic analysis shows that the repeated administration of meloxicam alters multiple substances in plasma, including nonvolatile organic acids, aromatic amino acids, monosaccharides, and inorganic compounds as early as four days following administration of meloxicam. Seventeen plasma molecules were able to distinguish meloxicam-treated from saline-treated cats. The metabolomic changes discovered in this study may help to unveil unknown mechanisms of NSAID-induced side effects. In addition, some metabolites could be valuable for individualizing the administration of meloxicam to cats to mitigate adverse effects.

Urinary chemical fingerprint left behind by repeated NSAID administration: Discovery of putative biomarkers using artificial intelligence.

Prediction and early detection of kidney damage induced by nonsteroidal anti-inflammatories (NSAIDs) would provide the best chances of maximizing the anti-inflammatory effects while minimizing the risk of kidney damage. Unfortunately, biomarkers for detecting NSAID-induced kidney damage in cats remain to be discovered. To identify potential urinary biomarkers for monitoring NSAID-based treatments, we applied an untargeted metabolomics approach to urine collected from cats treated repeatedly with meloxicam or saline for up to 17 days. Applying multivariate analysis, this study identified a panel of seven metabolites that discriminate meloxicam treated from saline treated cats. Combining artificial intelligence machine learning algorithms and an independent testing urinary metabolome data set from cats with meloxicam-induced kidney damage, a panel of metabolites was identified and validated. The panel of metabolites including tryptophan, tyrosine, taurine, threonic acid, pseudouridine, xylitol and lyxitol, successfully distinguish meloxicam-treated and saline-treated cats with up to 75–100% sensitivity and specificity. This panel of urinary metabolites may prove a useful and non-invasive diagnostic tool for monitoring potential NSAID induced kidney injury in feline patients and may act as the framework for identifying urine biomarkers of NSAID induced injury in other species.

Understanding the effect of repeated administration of meloxicam on feline renal cortex and medulla: A lipidomics and metabolomics approach.

Repeated administration of meloxicam can cause kidney damage in cats by mechanisms that remain unclear. Metabolomics and lipidomics are powerful, noninvasive approaches used to investigate tissue response to drug exposure. Thus, the objective of this study was to assess the effects of meloxicam on the feline kidney using untargeted metabolomics and lipidomics approaches. Female young-adult purpose-breed cats were allocated into the control (n=4) and meloxicam (n=4) groups. Cats in the control and meloxicam groups were treated daily with saline and meloxicam at 0.3mg/kg subcutaneously for 17days, respectively. Renal cortices and medullas were collected at the end of the treatment period. Random forest and metabolic pathway analyses were used to identify metabolites that discriminate meloxicam-treated from saline-treated cats and to identify disturbed metabolic pathways in renal tissue. Our results revealed that the repeated administration of meloxicam to cats altered the kidney metabolome and lipidome and suggest that at least 40 metabolic pathways were altered in the renal cortex and medulla. These metabolic pathways included lipid, amino acid, carbohydrate, nucleotide and energy metabolisms, and metabolism of cofactors and vitamins. This is the first study using a pharmacometabonomics approach for studying the molecular effects of meloxicam on feline kidneys.

Chronic morphine exposure affects contrast response functions of V1 neurons in cats

Opiates disrupt neural functions in many brain areas, including visual cortex. Previous studies have indicated substantial changes of many neuronal response properties induced by chronic morphine exposure in the visual information processing system. However, it remains unclear whether neuronal contrast coding is also affected. To investigate this issue, we measured the contrast response functions (CRFs) of V1 neurons in chronic morphine-treated and saline-treated cats by using extra-cellular single-unit recording techniques. Our results indicated significantly lower contrast sensitivity in morphine-treated cats than in saline-treated cats and V1 neurons in morphine-treated cats exhibited enhanced maximum visual responses, higher baseline responses and lower signal-to-noise ratios compared with saline-treated cats. These findings provide some neurobiological evidence for the morphine-mediated degenerations of the visual cortex, which could underlie the opiate-induced deficits in visual function.

CHRONIC MORPHINE EXPOSURE AFFECTS VISUAL RESPONSE LATENCY OF THE LATERAL GENICULATE NUCLEUS IN CATS

Chronic morphine exposure results in degradation of the functional properties of cortical cells. However, little evidence has been reported about the effect of morphine on the temporal properties of the visual system. We compared the visual response latency of different cells of the lateral geniculate nucleus (LGN) in morphine (10 mg/mL)- and saline-treated cats. Morphine-treated cats were given morphine sulphate by cervical subcutaneous injection twice daily for 10 days, whereas saline-treated cats received injections of 0.9% saline instead. We found that LGN neurons in morphine-treated cats exhibited significantly longer response latency than those in saline-treated cats (P < 0.001). To investigate whether different types of neurons exhibited similar changes in response to morphine, we classified LGN neurons as on- and off-centre, X and Y, and layer A, A1 and C neurons. There was a tendency for prolonged latency in layer C neurons and a significantly longer latency for the other neurons in morphine-treated cats (P < 0.05). These findings suggest that chronic morphine administration (10 mg/kg by cervical subcutaneous injection twice daily for 10 days) delays information transfer earlier in the visual pathway.

Chronic morphine exposure affects the visual response properties of V1 neurons in cat

Chronic opiate exposure leads to maladaptive changes in brain function. In view of the localization of opiate receptors in mammalian visual system, chronic opiate exposure is likely to affect the visual responses properties of V1 neurons. Using in vivo single-unit recording, we here showed that chronic morphine treatment resulted in the functional abnormality of primary visual cortical cells. When compared with saline-treated (as control) cats, cortical neurons in morphine-treated cats exhibited higher spontaneous activity, lower signal-to-noise ratios and weaker orientation and direction selectivity. However, re-exposure with morphine could significantly improve the function of V1 neurons in morphine-treated cats. These findings demonstrated that chronic morphine treatment could significantly degrade the response properties of V1 neurons and may lead to a function dependence on morphine in visual cortical cells.

Chronic morphine exposure induces degradation of receptive field properties of LGN cells in cats1

To investigate the effect of chronic morphine exposure on the receptive field properties of lateral geniculate nucleus (LGN) neurons in cats. Cats were injected with morphine (10 mg/kg) or saline twice daily, for 10 d. Subsequently, extracellular single-unit recording techniques were used to examine the sensitivity of LGN neurons to visual stimuli in chronic morphine-treated and saline-treated cats. Compared with saline-treated cats (as controls), LGN neurons in morphine-treated cats had decreased signal-to-noise ratios (1.9 vs 3.1), and orientation and direction sensitivity (0.103 vs 0.135 and 0.074 vs 0.10, respectively), accompanied by significant increases in spontaneous (27.4 vs 17.5) and evoked activity (preferred: 42.2 vs 38.1; average: 28.1 vs 22.3). Chronic morphine exposure can lead to the functional degradation of LGN neurons in cats, which might result from the effects of chronic morphine exposure on inhibitory neurotransmission.

Degradation of response modulation of visual cortical cells in cats with chronic exposure to morphine

The primary visual cortex (V1) plays an important role in vision and visual perception. Studies in many brain regions demonstrate that opiate abuse can change excitatory and inhibitory neurotransmission. To investigate the effect of chronic morphine exposure on the response modulation of V1 simple and complex neurons, we carried out in vivo extracellular recordings in V1 of morphine- and saline-treated (control) cats. Response modulation was quantified as the ratio of first Fourier components (F1) to the mean response (F0). Compared with saline-treated cats, V1 neurons in morphine-treated cats exhibited weaker response modulation and a longer time course of response. The decrease of response modulation was caused by an increase of F0. Further, morphine re-exposure significantly improved the response properties of V1 neurons in morphine-treated cats. These results suggest that chronic morphine treatment leads to a significant degradation of response modulation of V1 neurons and a morphine dependence of primary visual cortical function.

Administration of Selective Endothelin Receptor Type a Antagonist Ro 61-1790 Does Not Improve Outcome in Focal Cerebral Ischemia in Cat

The authors examined the effect of selective endothelin (ET) receptor type A (ET(A)) antagonism on histological and functional recovery in cat at 24 hours after reversible middle cerebral artery occlusion (MCAO). A novel and specific ET(A) antagonist, Ro 61-1790 [5-methylpyridine-2-sulfonic acid-6-(2-hydroxyethoxy)-5-(2-methoxyphenoxy)-2-(2-1H-tetrazol-5-y l-pyridin-4-yl)-pyrimidin-4-ylamide sodium salt (1:2)] (Roche, Basel, Switzerland), was used at doses that produced steady-state plasma concentrations and abolished ET-induced pial arteriolar vasoconstriction. In a cranial window preparation, 8 nmol/L ET constricted pial arterioles by 33 +/- 18% (mean +/- SD), but this response was ablated by intravenous Ro 61-1790 treatment (10-mg/kg bolus, 4-mg/kg/h infusion). In additional animal cohorts, halothane-anesthetized cats were treated with 90 minutes of MCAO and 24 hours of reperfusion. Animals received Ro 61-1790 infusion beginning at the onset of reperfusion and continuing for 6 or 24 hours (n = 41). Control cats were treated with 0.9% saline by intravenous infusion throughout reperfusion. There was no difference in injury volume or neurologic evaluation score in saline-treated cats (n = 11; caudate 24 +/- 28%, cortical injury 7.5 +/- 5% of ipsilateral structure; score 52 +/- 8) versus the results in cats treated with Ro 61-1790 for either 24 hours (n = 6; caudate 22 +/- 23%, cortex 6 +/- 5%, injury volume of ipsilateral structure; score 55 +/- 3) or 6 hours (n = 11; caudate 33 +/- 30%, cortex 12 +/- 14%, injury volume of ipsilateral structure; score 50 +/- 10). Mortality was greatest in the 24-hour drug treatment group. These data suggest that blockade of ET(A) receptor activity is not beneficial to tissue or functional outcomes from experimental stroke in cat.

Neuroprotective effect of YM-39558 in focal cerebral ischemia in cats

We studied the effect of YM-39558, orotic acid ethylester, in a focal cerebral ischemia model in anesthetized cats. YM-39558 has good permeability across the blood brain barrier, and in the brain is hydrolyzed to orotic acid, the main active substance. Cats were subjected to permanent occlusion of the middle cerebral artery (MCA) for 6 h, then killed and examined histologically. Treatment with YM-39558 (intravenous infusion of 11.8 mg (10 mg as orotic acid)/6 ml per kg per h) starting 15 min after MCA occlusion markedly reduced the volume of ischemic damage (from 2450±82 mm 3 of the cerebral hemisphere in the saline-treated cats to 1644±123 mm 3 in the YM-39558-treated cats, P<0.01). In contrast, YM-39558 (2.26 and 1.18 mg/0.8 ml per kg per h) showed no significant protective effect on ischemic damage. No significant differences were observed between saline- and YM-39558-treated cats concerning physiological variables including brain temperature. This evidence for the neuroprotective efficacy of YM-39558 in gyrencephalic species suggests its therapeutic potential in the treatment of stroke in humans.

Neuroprotective effect of YM90K, a novel AMPA/kainate receptor antagonist, in focal cerebral ischemia in cats.

We studied the effect of a novel alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA)/kainate antagonist, YM90K [6-(1H-imidazol-1-yl)-7-nitro-2, 3(1H, 4H)-quinoxalinedione monohydrochloride], in a focal cerebral ischemia model using anesthetized cats. Cats were subjected to permanent occlusion of the middle cerebral artery (MCA) for 6 h, then killed and examined histologically. The amount of ischemic damage was assessed in 12 stereotaxic coronal sections. Treatment with YM90K (i.v. infusion of 0.5 mg/5 ml/kg/h) starting 10 min after MCA occlusion markedly reduced the volume of ischemic damage (from 2823 +/- 164 mm3 of the cerebral hemisphere in saline-treated cats to 1737 +/- 305 mm3 in YM90K-treated cats). No essential differences were observed between YM90K-and saline-treated cats concerning physiological variables or brain temperature. These results further support the notion that the AMPA/kainate receptor plays an important role in the pathogenesis of focal cerebral ischemia. This evidence for the neuroprotective efficacy of YM90K in a gyrencephalic species suggests its therapeutic potential in the treatment of human stroke.

Amphetamine-induced recovery of visual cliff performance after bilateral visual cortex ablation in cats: measurements of depth perception thresholds.

After bilateral visual cortex ablation, cats exhibit a loss of depth perception as measured on a visual cliff, which recovers following administration of d-amphetamine. In this Study, 3 amphetamine-treated cats with visual cortex ablations showed a rapid and enduring recovery, with 2 of these animals obtaining levels of performance seen only with binocular vision, suggesting a restoration of binocular depth perception. Cats with asymmetrical lesions showed only a transient improvement during amphetamine treatment, and some animals not displaying autonomic signs of amphetamine intoxication did not improve. Saline-treated cats showed no signs of improvement, and the effect of amphetamine was blocked by the catecholaminergic antagonist haloperidol. These results indicate that amphetamine can induce an enduring recovery from a behavioral deficit after brain injury, which if left untreated would not spontaneously recover.

The Effect of Timolol Given Five Minutes After Coronary Occlusion on Plasma Catecholamines

The reported study determined whether timolol would afford a protective effect by preventing the coronary occlusion-induced arrhythmias associated with the increase in plasma norepinephrine (NE) and epinephrine (E). Ten anesthetized cats received saline or timolol (5 mg/kg, IV) five minutes after coronary occlusion of the left anterior descending coronary artery 10 to 14 mm below its origin. Coronary occlusion produced arrhythmia in three of the cats that received saline and in four of the cats that received timolol. Three of the saline-treated cats died in cardiogenic shock; two were sacrificed six hours postocclusion. Four of the timolol-treated cats died in congestive heart failure postcoronary occlusion. There was a gradual increase in NE (P greater than .05) and E (P less than .05) in both groups after coronary occlusion. Death produced a significant increase in NE and E levels. Timolol did not modify the occurrence of arrhythmias and the associated increase in plasma NE and E that developed after coronary occlusion and at death.

Megadose corticosteroid therapy following experimental traumatic spinal injury.

Corticosteroids are frequently used in the treatment of spinal trauma, although neither experimental nor clinical evidence to support their use is persuasive. Recently there have been claims that extremely high doses ("megadoses") of corticosteroids (equivalent to 15 to 30 mg/kg of methylprednisolone) improve neurological recovery compared to results with traditional steroid doses. The authors have compared the effect of megadose dexamethasone and methylprednisolone therapy to that of saline treatment following traumatic cervical spinal injury in the cat. During 6 weeks postinjury, neurological recovery did not differ significantly in corticosteroid-treated and saline-treated animals. Moreover, histopathological changes in the spinal cord were similar in methylprednisolone- and saline-treated cats. Corticosteroid-treated animals had a higher mortality rate than did control animals, with the predominant cause of death being neurogenic pulmonary edema. It is concluded that megadose corticosteroid treatment does not improve neurological recovery in this experimental model of spinal injury, and is associated with increased mortality.

Infarct size restriction in cats by the β-adrenergic blocker timolol

The β-adrenergic antagonist, timolol, was previously shown to exert a protective effect in cats subjected to 5 h of myocardinal ischemia. The present study was designed to determine the effect of timolol on infarct size in cats 24 h after coronary occlusion. Timolol (25 μg/kg) or vehicle (0.9% NaCl) was administered 0.5, 5, 10, 15 and 20 h after acute ligation of the left anterior descending coronary artery. There was no significant difference in arterial blood pressure or heart rate in MI cats receiving timolol or vehicle. Timolol markedly decreased S-T segment elevation at 2–12 h (P<0.05). Left ventricular weights in MI+ vehicle cats (8.5±0.7g, n=6) were similar to timolol-treated MI cats (8.9±0.4 g, n=7). However, the percent of the left ventricular myocardium infarcted, determined by nitroblue tetrazolium staining, was significantly less (P<0.001) in timolol MI cats compared to saline-treated cats, 9.8±1.2% (n=7) vs 18.9±1.8% (n=6), respectively. Hemodynamic or cytoprotective actions of timolol do not appear to explain these results. Rather, the mechanism of infarct size reduction by timolol is probably explained by antagonism of β-receptor-mediated metabolic effects.

Effect of naloxone on posttraumatic ischemia in experimental spinal contusion.

The effect of naloxone on blood flow and somatosensory evoked potentials was studied in cats subjected to 400 gm-cm contusion injuries of the thoracic spinal cord. Eight cats were treated with 10 mg/kg naloxone 45 to 60 minutes after injury, 11 cats were given 10 ml of saline instead of naloxone, and six cats were neither injured nor treated. Hydrogen clearance was used to measure blood flow in the lateral white columns at the contusion site. Naloxone, given intravenously, significantly inproved the blood flow rates in the lateral column white matter. At 2 hours after injury, the mean blood flow in the saline-treated cats fell to 50% (p greater than 0.01) of preinjury flow rates, whereas it increased 6% (p greater than 0.50) in naloxone-treated cats, and 12% (p greater than 0.50) in uninjured cats. At the 3rd hour after injury, the respective flows fell 47% (p less than 0.01), and 6% (p greater than 0.50), and increased 15% (p greater than 0.50) of the preinjury flow rates. The naloxone-treated cats had striking preservation of sensory function and somatosensory evoked potentials at 24 hours after injury. At 24 hours, responses had returned in all the naloxone-treated cats and in only 11% of the saline-treated cats. The probability of this combination of events occurring by chance is 0.0030. The authors conclude that naloxone may be useful for the treatment of spinal cord injury. The mechanism of the effect is unknown.

Effect of a single injection of reserpine on kinetics of 3H-dexamethasone binding to receptors of the cat hypothalamus and hippocampus.

Cats were injected intraperitoneally with reserpine (5 mg/kg) or saline and sacrificed 16 h later. Hypothalamic and hippocampal cytosols were assayed for the kinetics of 3H-dexamethasone (3H-DM) binding. A parallel series was performed in which saline-injected cats were infused via venocatheter with hydrocortisone (HC). Reserpine-injected cats were infused with saline. The hypothalamic cytosol of reserpinized cats showed a marked decrease in 3H-DM binding capacity relative to that from saline-treated cats. Hippocampal cytosol 3H-DM binding capacity was unaffected by reserpinization. Infusion of high levels of HC reduced the amount of 3H-DM binding in the hypothalamus, but did not account for all the reduction found after reserpine treatment. HC infusion had no effect on hippocampal binding capacity. Reserpine treatment did not change the dissociation constant differences between the two brain regions. The data suggest that depletion of neurotransmitters by reserpine treatment from the hypothalamus, but not the hippocampus, significantly reduces the number of 3H-DM binding sites and that such a reduction is due, in part, to the effects of reserpine and not to high circulating levels of HC.