Recovery of male rats from major abdominal surgery after treatment with various analgesics.

The objective of this study was to compare the recovery of male rats after a major abdominal surgical procedure (the implantation of a radiotelemetry transmitter) when treated with buprenorphine, butorphanol, or ketoprofen and subcutaneous fluids (5% dextrose) or with subcutaneous fluids only. The parameters for assessing recovery were heart rate (HR), mean arterial blood pressure (MAP), home cage activity, food and water consumption, and body weight. HR, MAP, and activity were continuously monitored by radiotelemetry methods, food and water intakes were determined daily, and body weights were measured once or three times a week. In light of HR, nocturnal home cage activity, water consumption, and body weight gain, animals were recovered by about 7 days after surgery. MAP normalized by 1 to 2 days postsurgery, and food consumption returned to presurgical levels 5 to 12 days after surgery, depending on the analgesic treatment. On the basis of nocturnal activity, HR, and food and water intakes, buprenorphine-treated animals recovered more slowly than did the other two analgesic-treated groups. By the other parameters, all three analgesic-treated groups showed very similar responses across time. Surprisingly, when compared with the groups receiving only subcutaneous fluids, buprenorphine and butorphanol delayed or did not advance recovery, whereas ketoprofen neither retarded nor advanced recovery. Explanations for these results include: (a) the analgesics were effective in relieving pain but had pharmacological side effects that altered the measured parameters, making it difficult to determine recovery; (b) the level of pain experienced did not notably affect recovery; (c) the analgesics, at the doses and/or dosing schedules used, were not effective in the relief of pain, thereby causing both groups of animals to recover at the same rate; and (d) the analgesics interfered with recovery. Final resolution of these issues awaits further investigation.

Stress-like responses to common procedures in individually and group-housed female rats.

The objective of this study was to assess the cardiovascular function and behavior of female Sprague-Dawley rats housed individually or with one or three cage mates under resting conditions and when subjected to common husbandry and experimental procedures and potentially stressful olfactory stimuli. Heart rate (HR) and mean arterial blood pressure (MAP) were assessed continuously by using radiotelemetry and are reported for the following periods: for 1 hour each day prior to any human interaction; for 12 h each day during the dark phase of the 12:12-h light: dark photoperiod; and for 2 h before and 3 h after acute husbandry and experimental procedures. Home-cage behaviors (sleeping, awake but not moving, moving, rearing, and grooming) were scored once each minute for 15 min before and 45 min after the acute procedures. Mean resting HR values in the mornings prior to human contact were significantly (P < 0.05) lower in rats housed four per cage than animals housed alone or with one cage mate, whereas MAP during this period was lowest in rats housed two per cage. Nocturnal HRs were highest in rats housed two per cage, whereas nocturnal MAP did not differ significantly between housing groups. When rats were subjected to acute husbandry and experimental procedures, HRs increased 80 to 180 beats per min (bpm) above a baseline of 300 to 325 bpm and were significantly (P < 0.05) increased for periods of 30 to 90 min after the procedures. MAP showed increases that were proportionately the same as those in HR. Group housing often, but not always, reduced these cardiovascular responses. Procedure-induced arousal behaviors occurred in all housing groups after the acute husbandry and experimental procedures, but the occurrence of these behaviors was less frequent and of shorter duration in group-housed rats than rats housed alone. In light of these results, we conclude that under resting conditions group housed rats were somewhat less stressed than were rats housed alone. Further, we conclude that common procedures induce significant stress-like responses in female rats, and the magnitude and duration of these responses are reduced by group housing.

Are "by-stander" female Sprague-Dawley rats affected by experimental procedures?

The objective of this study was to test the hypotheses that female rats are stressed by being in the same room as animals subjected to common husbandry and experimental procedures and that the level of stress is affected by housing density. Two commonly used indices of stress, heart rate (HR) and mean arterial blood pressure (MAP), were determined by using radiotelemetry for 2 h before and 3 h after rats witnessed the following procedures: decapitation, simulated decapitation, cage change, simulated cage change, restraint and subcutaneous injection, removal of rats to another room for injection, restraint and tail-vein injection, handling and weighing, and handling and vaginal lavage. In addition, home cage behaviors (sleeping, awake, moving, rearing, and grooming) were scored once each minute for 15 min before and 45 min after the procedures. Witnessing decapitation of six other rats induced small, but significant, increases in HR above undisturbed baseline values in animals housed alone, whereas responses in animals housed with one or three cage mates were slightly greater than those of rats housed alone. Witnessing a routine cage change induced significant increases in HR in rats which were equal to or greater than those induced by witnessing decapitations; however, housing density had little effect on the responses to cage change. HR did not significantly increase above baseline values in rats witnessing restraint and a subcutaneous or tail-vein injection of other rats or when witnessing other rats being handled and weighed. However, rats housed alone showed significant increases in HR when witnessing a vaginal lavage of other rats. Active behaviors (moving, rearing, grooming) in the home cage were significantly altered only in rats housed alone and then only when witnessing a cage change or a tail-vein injection. Considering primarily increased HR, we conclude that female Sprague-Dawley rats may be marginally stressed when present in the same room in which decapitation is being performed, but similar stress-like responses are induced by common husbandry and experimental procedures. Finally, group housing often, but not always, reduces the stress-like responses that can occur in female by-stander rats.

Does witnessing experimental procedures produce stress in male rats?

The objective of this study was to test the hypotheses that male rats are stressed by being in the same room as animals subjected to common husbandry and experimental procedures and that the level of stress is affected by housing density. Two commonly used indices of stress, heart rate (HR) and mean arterial blood pressure (MAP), were determined by using radiotelemetry for 2 h before and 3 h after rats witnessed the following procedures: decapitation, decapitation and necropsy, cage change, restraint and subcutaneous injection, and restraint and tail-vein injection. In addition, home cage behaviors (sleeping, awake, moving, rearing, and grooming) were scored once each minute for 15 min before and 45 min after the procedures. Witnessing decapitation or decapitation and necropsy of 6 other rats induced small, but significant, increases in HR and MAP in animals housed alone, whereas responses in animals housed with one or three cagemates were more transient or not significant. Witnessing a routine cage change also induced small increases in HR and MAP in rats housed alone or with one cagemate, but HR and MAP decreased in rats housed four per cage. HR and MAP did not change in rats witnessing restraint and a subcutaneous injection of other rats, but these indices were transiently increased when rats witnessed animals being restrained in a rodent restrainer and given a tail-vein injection. Home cage behaviors were significantly altered only in rats witnessing decapitation and necropsy and then only in rats housed alone. We conclude that male Sprague-Dawley rats are not significantly stressed when present in the same room in which decapitation or other common experimental procedures are being performed, especially when the animals are housed with cagemates.

Stress-like responses to common procedures in rats: effect of the estrous cycle.

The objective of this study was to assess cardiovascular and behavioral responses of Sprague-Dawley female rats subjected to or witnessing common husbandry and experimental procedures at various points during the estrous cycle. Heart rate (HR) and mean arterial blood pressure (MAP) were determined using radiotelemetry for 2 h before and 3 h after: cage change, restraint and subcutaneous (s.c.) injection, restraint and tail-vein injection, witnessing decapitation of other rats, smelling urine and feces from stressed rats, and smelling dried rat blood. Home cage behaviors (sleeping, awake, moving, rearing, and grooming) were scored once each minute for 15 min before and 45 min after the incidents. Being subjected to cage change, restraint and injections, and odors significantly increased HR and MAP 60-120 beats per min and 10-20 mm Hg over baseline respectively for 45 to 90 min. Witnessing these procedures also significantly increased HR and MAP but the magnitude was reduced by 20% to 30% compared to that seen in rats subjected to the procedures. Witnessing decapitation of other rats induced cardiovascular responses which were not different from those of rats witnessing other procedures. The cardiovascular responses were not enhanced during proestrus-estrus compared to metestrus-diestrus. There were also no significant effects of the estrous cycle on home cage behavior after these procedures. We conclude that cycling female rats show stress-like effects when they are subjected to or witness common husbandry and experimental procedures, but there is little to no effect of the estrous cycle.

Stress-like responses to common procedures in male rats housed alone or with other rats.

The objective of this study was to assess the cardiovascular function and behavior of male Sprague-Dawley rats housed individually or with one or three cagemates during resting conditions and when subjected to common husbandry and experimental procedures and potentially stressful olfactory stimuli. Heart rate (HR), mean arterial blood pressure (MAP), and movement in the cage were collected by using radiotelemetry for 24 h on an experiment-free day and for 2 h before and 3 h after the following acute procedures: cage change, restraint and subcutaneous injection, restraint and tail-vein injection, exposure to the odor of urine and feces from stressed rats, and exposure to the odor of dried rat blood. Home cage behaviors (sleeping, awake, moving, rearing, and grooming) were scored once each minute for 15 min before and 45 min after the acute procedures. Resting HR and MAP values consistently were lower in rats housed four per cage than animals housed alone or with one cage mate. Compared to that of animals housed individually, general activity was higher during the light phase and lower during the dark phase in rats housed four per cage. Rats housed four per cage showed significantly lower HR and MAP in response to acute husbandry and experimental procedures than rats housed alone, and the HR and MAP of rats housed in pairs were not consistently lower than those of rats housed alone. Procedure-induced arousal behaviors were observed in all housing groups after the acute husbandry and experimental procedures, but rats housed four per cage returned to sleeping behavior more quickly than did rats in the other housing groups. In light of these results, we concluded that under resting conditions, rats housed four per cage were less stressed than were rats housed alone, that common procedures induce noteworthy stress-like responses in male rats, and that the magnitude and duration of these responses are reduced by group housing.