Chronic stress in dogs subjected to social and spatial restriction. I. Behavioral responses.

Six weeks of social and spatial restriction were used as a model to induce chronic stress in Beagles. Behavioral and physiological measurements were performed during a period of enriched spacious outdoor housing in groups (GH) and during a subsequent period of solitary housing in small indoor kennels (IH). Behavioral parameters that may indicate chronic stress in dogs are reported. During IH, the dogs showed significantly (comparison-wise error rate <0.05) lower postures than during GH. IH induced enduring increments in frequencies of autogrooming, paw lifting, and vocalizing, and was associated with incidents of coprophagy and repetitive behavior. So far, we interpret the behavioral changes as signs of chronic stress. Relatively low levels of walking, digging, intentions to change from one state of locomotion to another, and increments in circling are conceived as obvious adaptations to the specific features of the IH system. By challenging the dogs outside their home kennel we tested whether the dogs' coping abilities were affected by IH. Dogs that were challenged were introduced into a novel environment, given the opportunity to escape from their home kennel, restrained, walked down an unfamiliar corridor, presented a novel object, exposed to loud noise, given food, or confronted with a conspecific. During IH, challenged dogs exhibited higher postures, showed more tail wagging, nosing, circling, urinating, and defecating, and changed more often from one state of locomotion (or posture) to another than during GH. These behavioral changes were observed across the different types of challenges, with the exception of the noise administration test. In the presence of conspecifics, the socially and spatially restricted male dogs behaved more dominantly and aggressive than during the time that they were kept in groups. Such behavior manifested as increased performances of raised hairs, growling, paw laying, and standing over. Both sexes showed increases in paw lifting, body shaking, ambivalent postures, intentions to change from one state of locomotion to another, and trembling in any of the challenges, excluding the walking down the corridor test. In short, during a variety of challenges, socially and spatially restricted dogs exhibited a heightened state of aggression, excitement, and uncertainty. Behavioral differences between dogs that had experienced pleasant and bad weather conditions during GH, suggested that "pleasant-weather individuals" had experienced early stress during the control period, and, as a result, responded to the subsequent period of IH differently. Regardless of the housing conditions, challenged bitches showed stronger indications of acute stress than male dogs. Gender did not affect the chronic stress responses to social and spatial restriction. A low posture and increased auto-grooming, paw lifting, vocalizing, repetitive behavior, and coprophagy may indicate chronic stress in dogs, and as such, can help to identify poor welfare. When challenged, chronically stressed dogs may show increased excitement, aggression, and uncertainty, but the nonspecificity of such emotional behavior will complicate its practical use with regard to the assessment of stress.

Chronic stress in dogs subjected to social and spatial restriction. II. Hormonal and immunological responses.

Two groups of beagles, accustomed to spacious group housing, were subjected to social and spatial restriction and studied for manifestations of chronic stress with a time interval of 7 weeks between the groups. The change from outside group housing (the control period) to individual housing in small indoor kennels resulted in sustained decreases in urinary adrenaline/creatinine and noradrenaline/creatinine ratios for the total group. Urinary dopamine/creatinine and noradrenaline/adrenaline ratios were statistically unaffected. Socially and spatially restricted dogs that had experienced pleasant weather during the control period showed (a) increased salivary and urinary cortisol concentrations, (b) a diminished responsiveness of the pituitary-adrenal axis to a sudden sound blast or exogenous CRH, (c) intact plasma ACTH and cortisol suppressions after dexamethasone administration, and (d) increased concanavalin A induced lymphocyte proliferations. When social and spatial restriction was preceded by a control period during which the weather was bad, these physiological responses were either augmented (lymphocyte proliferation), or offset (salivary and urinary cortisol), or directed oppositely (CRH-induced ACTH and cortisol responses). Together with the previously presented behavioral observations, these data suggest that bad weather conditions during spacious outdoor group housing induced early stress that attenuated the negative appraisal of the subsequent period of social and spatial restriction. In comparison to male dogs, bitches showed increased HPA responses to a sound blast or exogenous CRH. Their increased attenuations of the ACTH and cortisol responses to CRH after 5 weeks of restricted housing indicates that bitches are not only more susceptible to acute stress, but also to chronic housing stress. It is concluded that the quality of circumstances preceding a period of affected well-being determines the magnitude and even the direction of the behavioral and physiological stress responses. Basal salivary and urinary cortisol measurements are useful for the assessment of chronic stress, and of poor welfare in dogs. The use of urinary catecholamine, peripheral leucocyte, and lymphocyte proliferation measures requires further investigation.

Comparison of inhalation-to-perfusion ratio in anesthetized dogs with barrel-shaped thorax vs dogs with deep thorax.

Interregional, as well as intraregional (local), distributions of the inhalation-to-perfusion ratio were analyzed in the lungs of 20 prone anesthetized healthy dogs--10 dogs with barrel-shaped thorax (Beagles) and 10 dogs with deep thorax (Greyhound-type dogs)--using 99mTc inhalation-perfusion lung scintigraphy. Dorsoventral and lateral views were analyzed. In both types of dogs, the ratio between the mean inhalation and perfusion values (interregional mismatching factor gamma) decreased from craniad to caudad and the decrease was more sustained in the right than in the left lung. However, the total decrease was less in Greyhound-type dogs than in Beagles (cranial-to-caudal decrease of 14 and 27%, respectively, in the left lung, and 62 and 56%, respectively, in the right lung). The dorsal-to-ventral distribution of gamma was different in the 2 types of dogs. In Beagles, it increased from dorsal to ventral zones by about 50% of the initial dorsal zone value, whereas in Greyhound-type dogs, only a slight dorsal-to-ventral decrease was evident, with the exception of the more ventral zone. Differences in the intraregional mismatching factor (rho) indicated that the intraregional inhalation-to-perfusion inequalities were more pronounced within the caudal regions and within the ventral zones of the lungs in both types of dogs, and in the more cranial zones in the lungs of Beagles. However, the degree of intraregional mismatching was generally lower in Greyhound-type dogs. Thus, the gravitational force is not the dominating determinant of interregional or intraregional inhalation-to-perfusion ratio distributions in the lungs of anesthetized prone dogs.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of posture and anaesthesia on the distribution of pulmonary perfusion and lung configuration in beagle dogs.

To investigate the effect of posture and anaesthesia on the topographical distribution of pulmonary perfusion in canine lungs, the changes in lung shape, configuration and regional perfusion were assessed in healthy beagle dogs, using a repeated 99mTc perfusion scintigraphic procedure. The general shape of the lung images was similar in standing and prone postures, except for a relative increase of the more ventral zone in the prone posture, ascribed to vertical flattening of the lung associated with enlargement of the ventral zones. Configuration changes revealed a shift of the parenchyma towards the more caudal parts in the prone posture, which suggests a parenchymal compression of the paradiaphragmatic lung zones. The prone posture induced a decreased perfusion to the caudal third of the lung. Anaesthesia induced significant changes in lung shape without an obvious direction. The perfusion to the more ventral as well as to the more cranial zones was reduced. Differences in the perfusion distribution are thought to be mainly due to the pressure exerted by the abdominal content through the diaphragm and to the shift of the blood towards better ventilated lung regions.

Quantitative analysis of radioaerosol inhalation and perfusion scintigraphy in dogs.

A method was developed for the analysis of 99mTc MAA perfusion and 99mTc phytate colloid aerosol inhalation distribution patterns. Scintigraphic images were compared, based on the activity of corresponding picture elements (pixels). The possible mismatching in a pixel between both distributions was expressed in terms of a regional mismatching (common to a whole region) and an additional intraregional mismatching at the individual pixel level. Parameters characterizing the degree of regional and intraregional mismatching were introduced. The method was applied to 16 anesthetized healthy dogs in which a cranial-to-caudal gradient in regional mismatching was found.

Pulmonary scintigraphy in canine lobar and sublobar airway obstruction.

The intrapulmonary distribution of the inhalation-to-perfusion ratio (I/P) was studied after placement of an obstruction in a sublobar bronchus (SLO) or in a lobar bronchus (LO) in 17 anesthetized prone (sternal recumbent) dogs. Placement of an SLO or LO did not induce any significant changes in the standard ventilatory and hemodynamic parameters measured. With the use of 99mTc aerosol inhalation combined with 99mTc perfusion lung scintigraphy, parameters quantifying the inhalation (I) to perfusion (P) mismatching at regional as well as at intraregional levels were calculated. The SLO increased the relative ventilation to the lung containing the obstruction, induced a shift of blood from the obstructed segment to the rest of the same lung, and increased the ratio between the mean I and the mean P (regional mismatching factor) in both the obstructed segment and the lung containing the obstruction. The LO diverted air and blood away from the obstructed lobe to the contralateral lung, but blood to a lesser extent. The LO decreased the regional mismatching factor in the obstructed lobe but also in the lung containing the obstruction. It also increased significantly the intraregional I to P mismatching in the obstructed lobe as well as in the rest of the same lung. After withdrawal of LO and reinsufflation of the collapsed lobe, blood continued to leave this lobe, while the withdrawal of SLO allowed recovery of the initial perfusion. This suggests that both hypoxic vasoconstriction and mechanical factors such as vascular distortion are involved in the blood shifts observed, and require some delay to be relieved. It is concluded that in dogs compensating mechanisms such as collateral ventilation are very effective. In case of SLO, I to the lung involved is increased. In case of LO, vasoconstriction in response to alveolar hypoxia could not fully compensate for the decreased I to the obstructed lobe.

Scintigraphic analysis as a diagnostic tool in canine experimental lung embolism.

Scintigraphic changes occurring after lung embolism induced by intravenous administration of agar were assessed in 10 anesthetized prone dogs. Using 99mTc aerosol inhalation combined with 99mTc perfusion scintigraphy, parameters quantifying the regional distribution of the inhalation-to-perfusion ratio (I/P) and the degree of intraregional I-P mismatching were calculated from dorsoventral views (DV) for 6 equidistant cranial-to-caudal left and right lung zones before (B) and after acute embolism (PE). Postmortem examination was performed in 7 dogs. Several perfusion defects could be detected in either the conventional or the functional (I-P) lung scintigrams. Nevertheless, PE did not induce significant changes in blood gases. On the scintigrams, the outer zones appeared to be the most heavily embolized. The regional I/P ratio was increased in the more caudal and cranial parts of both lungs. However, postmortem examination of the lungs showed the presence of emboli diffuse in all lobes. Their presence was revealed in all zones by a significant increase of an intraregional mismatching index rho and especially of an intraregional mismatching factor mean value of gamma. After acute embolism, blood was redistributed to perihilar regions, especially in the right lung. This redistribution process continued during the experiment. In conclusion, the use of combined aerosol inhalation/perfusion lung scintigraphy with quantitative analysis provides a sensitive method for the detection of pulmonary embolism.

Effects of age and breed on the phospholipid composition of canine surfactant.

To investigate possible age- and breed-related changes in the composition of canine pulmonary surfactant, we determined the phospholipid patterns of surfactants isolated by bronchoalveolar lavage of 3 age categories of beagles (3-7 months; 3-7 years; 12 years and older) and of 1 group of greyhounds (4-14 years). There was a significant (p = 0.01) increase in the proportion of phosphatidylcholine in surfactant with age, whereas the proportions of phosphatidylserine and sphingomyelin were significantly lower in old beagles compared to young dogs. Although the differences were generally rather small, they may nevertheless be of biological importance, as was indicated by comparing the minimal surface tensions of lavage fluids obtained from young and old beagles. It is attractive to speculate that the shift in surfactant lipid composition could be 1 of the mechanisms that permit efficient lung function in old dogs, despite changes in morphology and mechanics in the aging lung. The phospholipid composition of surfactant isolated from greyhounds differed significantly from that in beagles. The surfactant of greyhounds was enriched in phosphatidylglycerol compared to all age groups of beagles. The degree of saturation of surfactant phosphatidylcholine was also higher in greyhounds, although this differences was significant only when compared to young and middle-aged beagles.

Four methods for general anaesthesia in the rabbit: a comparative study.

The efficacy and safety of pentobarbitone, ketamine/xylazine, fentanyl/fluanisone/diazepam, and halothane/nitrous oxide anaesthesia were compared in 4 groups of six New Zealand White rabbits. Heart and respiratory rates, body temperature, reflexes, blood pressure and blood gases were measured. Pentobarbitone appeared to be unsuitable for anaesthesia in rabbits, as 5 of the 6 rabbits to whom it was administered, required artificial respiration or died. The combinations of ketamine/xylazine and fentanyl-fluanisone/diazepam both produced unpredictable levels of anaesthesia together with a substantial decline in arterial blood pressure and PO2. Despite a severe drop in blood pressure (up to 37.5%), anaesthesia with halothane and nitrous oxide was found to be superior to the other anaesthetic agents.

Volume-regulated arginine vasopressin release in conscious dogs. Evidence for dopaminergic or opioid modulation?

The possibility of a dopaminergic and/or opioid modulation of the volume-regulated release of AVP was investigated in conscious dogs. Either bromocriptine, 10 micrograms/kg body weight po, or naloxone, 0.1 mg/kg body weight iv, was administered prior to induction of nonhypotensive hypovolemia. Volume contraction of 15 ml/kg body weight was induced gradually, over a period of 30 min. Basal plasma AVP levels in the bromocriptine group were not significantly different from control group values. Bromocriptine administration significantly augmented AVP release following volume contraction. Mean arterial pressure in the bromocriptine group decreased to a slightly, but significantly, lower level than that in the control group. Mean arterial pressures, however, did not adequately explain the magnitude of the AVP response in the bromocriptine group. In the naloxone group, neither baseline levels, nor AVP values following volume contraction, differed significantly from respective control group values. In conclusion, the results suggest the possibility of a stimulatory role for endogenous dopamine in the volume-regulated, but not the basal, release of AVP in conscious dogs.

Osmolality-regulated arginine vasopressin release in conscious dogs. Evidence for dopaminergic or opioid modulation?

Experiments were performed in conscious dogs, in order to study the possibility of dopaminergic or opioid modulation of the osmolality-regulated release of AVP. Hypertonic saline (20%), infused during a period of 2 h at a rate of 0.03 ml.kg-1.min-1, induced a significant AVP response, which was not influenced by prior administration of bromocriptine or naloxone. Data presented in this report, therefore, are not in support of a dopaminergic or opioid modulation of the osmolality-regulated AVP release in dogs. The results demonstrate a great consistency in individual plasma osmolality-plasma AVP relationships, next to a large inter-individual variation.

Radionuclides in lung diagnostics: a new approach. Summary of the first results.

With a 99mTc-labelled aerosol an inhalation (ventilation) image of the lungs was obtained. A lung perfusion image was obtained with 99mTc-labelled macro-aggregates. The data from the gamma camera were stored in a computer and the inhalation-perfusion (I/P) ratio was calculated for the total lung as well as for one half, another selected region, and a local (pixel) area. In the anaesthetised dog in sternal recumbency, the I/P ratio decreased from the cranial to the caudal lung regions. Hence in the dog gravity is not the only determinant of the I/P ratio distribution, as it is assumed to be in man. Position and anaesthesia appeared to influence the distribution of I/P ratios within the lung.

Crimidine (2-chloro-4-(dimethylamino)-6-methylpyrimidine) poisoning in a dog due to ingestion of the rodenticide Castrix.

The diagnosis and treatment of a case of crimidine poisoning in a dog are described. Presenting signs were seizures and vomiting. The vomitus contained a purple coloured cereal grain. The signs and grain colour were suggestive for a rodenticide with convulsive effects. The diagnosis of crimidine poisoning was made by thin layer chromatography and was later confirmed by finding the source of the poison. Except for the administration of Vit B6, the specific antidote for crimidine, general treatment principles for poisoning were followed. The treatment of crimidine poisoning is time consuming and requires intensive care facilities.

Capillary and venous blood compared with arterial blood in the measurement of acid-base and blood gas status of dogs.

Acid-base and blood gas status of capillary blood from the ear was compared with acid-base and blood gas status of arterial and venous blood in dogs with induced hypoxemia, hypercapnea, and hypovolemia. It was concluded that capillary blood samples can replace arterial blood samples for the measurement of acid-base and blood gas status of dogs with severe impairment of lung function. When circulation is impaired capillary blood samples cannot replace arterial blood samples for the measurement of acid-base and blood gas status of dogs. With impaired capillary circulation, the capillary-arterial differences become unacceptably large. It is, therefore, advisable to submit samples of capillary blood for analysis only if circulation is not impaired and microtubes can be filled quickly and easily.

Hemodynamic and metabolic consequences of hemodilution with different diluents.

Hemodilution was performed with the crystalloid Ringer's lactate (n = 6) and the colloid Haemaccel (n = 5) in dogs during automatically controlled total cardiopulmonary bypass with constant arterial and venous pressures. Single observations were made with Macrodex and Rheomacrodex hemodilution. Hemoglobin concentration and hematocrit were used as parameters for hemodilution. Total plasma protein proved to be unsuitable. The volume needed to induce the same level of hemodilution with lactated Ringer's and Haemaccel was twice the volume needed with Macrodex and Rheomacrodex. The volume shift from intravascular to extravascular was larger during Ringer's lactate hemodilution than during Haemaccel hemodilution. The amount of volume shift was clearly related to changes in colloid osmotic pressure. Lowering of total peripheral vascular resistance, with increased arterial line flow during controlled constant arterial and venous pressures was seen during hemodilution with each of the above materials. Potassium and calcium concentrations in the blood increased significantly during hemodilution with Haemaccel. Base excess was constant during hemodilution with lactated Ringer's but decreased in all other cases. A decrease in oxygen consumption was common, and most pronounced during hemodilution with Haemaccel.