Unrestrained Controls Research Articles

Antinociceptive and respiratory effects following application of transdermal fentanyl patches and assessment of brain μ-opioid receptor mRNA expression in ball pythons.

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.

Dopamine D1 receptor modulation of set shifting

Chronic stress exerts detrimental effects on higher order executive functions that are governed by the prefrontal cortex. Experimental data suggest that dopamine D1 receptor-mediated hypodopaminergic dysfunction may underlie stress-induced cognitive deficits. However, although the involvement of D1 receptors in working memory is well established, less is known about their role in the modulation of set-shifting ability. Therefore, the aim of the present study was to examine the impact of the selective D1 receptor agonist, SKF 81297, on the attentional set-shifting task performance of rats subjected to repeated restraint stress and of unrestrained controls. The acute administration of SKF 81297 to control rats facilitated extradimensional set-shifting. However, only intermediate doses (0.1 and 0.3 mg/kg) were effective, whereas no effect was observed after the administration of either lower (0.01 mg/kg) or higher (1 mg/kg) doses. This dose-response curve was shifted to the left in stressed animals as the effectiveness of SKF 81297 (as compared with either vehicle-treated controls or stressed animals) was found only after the administration of lower drug doses (0.01 and 0.1 mg/kg). The beneficial effects of SKF 81297 on the attentional set-shifting task performance of stressed rats may have therapeutic implications for the treatment of frontal-like disturbances, particularly cognitive inflexibility, in stress-related psychiatric disorders.

Early associations with food in anorexia nervosa patients and obese people assessed in the affective priming paradigm

Two experiments are reported that used the affective priming paradigm (Fazio, R. H., Sanbonmatsu, D. M., Powell, M. C., & Kardess, F. R. (1986). On the automatic activation of attitudes. Journal of Personality and Social Psychology, 50, 229–238) to uncover associations with food at a relatively automatic level. Experiment 1 tested the hypothesis that anorexia nervosa (AN; n=22) patients would show less sensitivity to the palatability of foods than unrestrained lean controls ( n=27). Results indeed suggested that AN patients did not display a liking of palatable foods over unpalatable foods, whereas unrestrained controls did. Experiment 2 tested the hypothesis that obese people ( n=27) would show more sensitivity to the palatability of (high-fat) palatable foods than unrestrained lean controls ( n=27) would. However, results suggested that the priming effect was based on health concerns, in that participants showed a preference for low-fat palatable foods over high-fat palatable foods. Average speed of responding and context are discussed as variables influencing the affective priming effect. Taken together, results suggest that food evaluations at a relatively automatic level are controlled by an interaction between participant characteristics, stimuli characteristics, and the specific context.

NO mediates effects of estrogen on central regulation of blood pressure in restrained, ovariectomized rats.

We tested the hypotheses that estrogen replacement in ovariectomized (OVX) rats attenuates cardiovascular responses to psychological stress and that nitric oxide (NO) in the brain mediates these effects. Female rats were OVX; one group received 17beta-estradiol (OVX-E) for 11-12 days and the other received vehicle (OVX-V). Seven days after OVX, OVX-E and OVX-V rats were chronically instrumented for arterial pressure measurements and intracerebroventricular injections. Later (4-5 days), OVX-E and OVX-V rats received intracerebroventricular injections of NG-nitro-l-arginine (88 microg/kg), an inhibitor of constitutive NO production, or vehicle. Mean arterial pressure (MAP) and heart rate responses were then measured in conscious rats exposed to two cycles of 1-h restraint/1-h rest. We show that MAP responses in restrained OVX-E rats were attenuated both during restraint and during rest. Although inhibition of NO production in the brain had no effect on MAP responses to restraint in OVX-V rats, it augmented responses in restrained OVX-E rats, especially during periods of rest, so that MAPs in restrained OVX-E and OVX-V rats were indistinguishable. Finally, NO levels in hypothalami and brain stems were elevated in restrained OVX-E, but not OVX-V, rats compared with their respective unrestrained controls. These results show that estrogen replacement in OVX rats reduces arterial pressure responses to psychological stress and that these effects are mediated, at least in part, by NO.

Adolescent development alters stressor-induced Fos immunoreactivity in rat brain

Adult-typical behavioural responses to environmental challenges as well as the stressor responsiveness of several neural systems emerge over adolescent development. The present study was undertaken to determine whether stressors might activate different neural populations in adult vs juvenile male rats. Fos-immunoreactivity was determined in various forebrain nuclei following 15 min or 2 h of restraint in 28- and 60-day-old male rats (representing late juvenile and young adult ages, respectively) and compared to non-restrained control animals at each age. Few Fos-positive cells were identifed in unrestrained controls at either age. Restraint, however, induced the production of Fos in several areas. Fos immunoreactivity was marked in parvocellular regions of the paraventricular nucleus of the hypothalamus following both restraint periods and at both ages, an observation consistent with previous observations that restraint increases plasma corticosterone at both ages. And at both ages, Fos immunoreactivity was evident in magnocellular regions of the hypothalamus only following the longer restraint period. Fos immunoreactivity, however, clearly varied as a function of adolescent age in several regions. Moderate to intense Fos immunoreactivity was observed in adults in all divisions of the anterior olfactory nucleus, cortical and medial amygdaloid nuclei, pyriform cortex and tenia tecta. In contrast to the adult, only a few Fos positive cells were observed in any of these regions in juveniles. Exposure to the same stressor induced Fos in a broader spectrum of neurons in young adult than in juvenile male rats. The lack of Fos-positive cells in specific areas of juveniles may relate to maturation in specific amygdaloid nuclei, which project to many of the other regions that showed age-related differences in Fos production. The emergence over adolescence of Fos-positive cells in specific areas in response to stressors may underlie the emergence of adult-typical behavioural and neural stressor-responsiveness.

Rat strain differences in the potentiation of morphine-induced analgesia by stress

Restraint stress has been shown to increase the magnitude and duration of morphine-induced analgesia; however, this phenomenon has only been investigated using the Sprague-Dawley rat strain. The purpose of this study was to determine if other rat strains would also exhibit a potentiated analgesic response to morphine compared to their unrestrained controls. Dose-response and time course curves for the analgesic effect of morphine (1.0, 3.0, 5.6, 10 mg/kg) were generated in adult, male Wistar, Lewis, Fischer 344, Long-Evans Hooded, and Sprague-Dawley rats either unrestrained or restrained in Plexiglas cylinders, using the tail flick assay. Morphine produced dose-dependent increases in tail flick latencies, and this effect was potentiated by restraint stress in the Sprague-Dawley, Wistar, Lewis, and Fischer 344 strains, but not in the Long-Evans Hooded rats. Because Sprague-Dawley and Wistar rats displayed the most robust stress effect, the use of either of these rat strains is appropriate in studying the mechanisms of stress-induced potentiation of analgesia. The differences among rat strains demonstrated in this study may serve as a basis for correlation with opioid function.

Estrogen antibodies reduce vulnerability to stress-induced failure of intrauterine implantation in inseminated mice

In Experiment 1, inseminated mice were randomly assigned to either an undisturbed control condition or four conditions involving exposure to restraint stress on days 1 through 5 of pregnancy. Restrained animals received one of three doses of estrogen antibodies or just vehicle injections on each day of restraint. Restrained animals receiving vehicle only showed significantly fewer uterine implantation sites than did unrestrained controls, while restrained animals given estrogen antibodies showed more implantation sites than did vehicle-treated restrained animals. In Experiment 2, varied dosages of refined estrogen antibodies were administered to inseminated females concurrent to restraint-stress on days 1 through 5 of pregnancy. More females receiving the higher dosages of antibodies produced litters than did restrained females with just vehicle injections, and at the highest dose the number of litters was similar to that produced by undisturbed control females. These results converge with other evidence to suggest that stress-induced pregnancy blocks are mediated by estrogens.

Research Note: The Effects of Post-Mortem Wing Restraint (Muscle Tensioning) on Tenderness of Early-Harvested Broiler Breast Meat

In each of two trials, 80 broilers were slaughtered by conventional methods. Forty carcasses served as unrestrained controls. The wings of the other carcasses were bound tightly together at the elbow above the dorsal surface of the carcass prior to chilling. All carcasses were chilled in agitated 13 C water for 15 min followed by an additional 45 min in ice slush (1C). Breast fillets were removed from the carcasses immediately after chilling, aged 24 h, cooked, and evaluated for shear value.Wing restraint significantly decreased shear values of cooked fillets (8.3 kg/g of meat) compared with shear values for cooked fillets obtained from unrestrained, conventionally chilled carcasses (9.4 kg/g of meat). Shear value means for both treatments were above the accepted sensory panelist toughness threshold shear value of 8 kg/g of meat.

Comparison of body size estimation and eating disorder inventory scores in anorexia and bulimia patients with obese, and restrained and unrestrained controls

Psychological attributes and body size estimation were compared in four subgroups of anorexia and bulimia patients, an obese group, an unrestrained control group, and a restrained control group. The four patient subgroups were anorectic-restrictors, anorectic-bulimics, bulimics with a history of anorexia, and bulimics without a history of anorexia. The bulimics with a past history of anorexia displayed the greatest degree of psychopathology, as measured by the Eating Disorder Inventory (ED/). Of the four anorexia and bulimia subgroups, the anorectic-restrictors displayed the least pathological EDI profile while the anorectic-bulimics and bulimics with no history of anorexia displayed intermediate profiles. All anorexia and bulimia subgroups overestimated the size of their hips and their body depth relative to the two control groups and the obese group. There were no differences in body size estimation between the subgroups of anorexia and bulimia patients. All four groups of patients showed improvements on both the EDI and body size estimation task with treatment. The implications of these findings for diagnostic criteria and appropriate subgrouping of anorexia and bulimia patients is discussed.

Stress-induced suppression of herpes simplex virus (HSV)-specific cytotoxic T lymphocyte and natural killer cell activity and enhancement of acute pathogenesis following local HSV infection

Stressful events suppress a broad spectrum of both humoral and cellular immunological responses. However, studies of the effects of stress on the development of specific antiviral immune responses have not been reported. We have utilized an established murine model of an acute, local footpad Herpes simplex virus type 1 (HSV-1) infection to study the effect of restraint stress on the generation of HSV-specific cytotoxic T lymphocytes (CTL) and natural killer (NK) cell activity. Lymphoproliferative responses in the popliteal lymph nodes following footpad infection as well as the generation of HSV-specific CTL and NK cell activity were depressed in restrained mice compared to infected, unrestrained controls. Frequency analyses of HSV-specific pre-CTL indicated that suppression of the CTL response occurred early in the sequence of events that precedes the generation of functionally lytic CTL and was not mediated by a diminished IL-2 response. Although restrained mice exhibited fewer lymphocytes in the popliteal lymph nodes, the subset distribution was the same as that in the unrestrained controls. Furthermore, stress-induced immunosuppression resulted in a higher titer of infectious HSV at the site of infection. Overall, these findings provide evidence that physiological changes associated with restraint stress can influence the immune response to a specific viral infection and alter the course of viral pathogenesis.

Patient characteristics associated with the use of mechanical restraints

To compare the characteristics of restrained patients with those of unrestrained patients by assessing a number of medical, behavioral, and cognitive variables including a disruptive-behavior inventory. Case-control study. A 719-bed university-affiliated teaching hospital. The 80 cases were patients identified by the nursing staff as having had a restraint applied within the last 24 hours prior to entry in the study. The 80 unrestrained controls were selected from the rooms adjacent to the cases' in order to match for proximity to the nursing station and nurse staffing. Demographic data, data on diagnoses and treatments, results of the Folstein Mini-Mental State (MMS) test and an eight-item disruptive-behavior inventory, and outcome information were obtained for each patient using a standardized procedure. Three important patient characteristics were significantly associated with restraint use in a multiple logistic regression model: disruptive behaviors, nursing assessment of risk of falling, and cognitive impairment. Cases were older than controls, but age was not an independent characteristic associated with restraint use when controlling for cognitive impairment, risk of falling, and disruptive behaviors. Restraint use was more likely in patients with disruptive behaviors, at risk of falling, and with cognitive impairment. Attention to these factors and alternative strategies for dealing with them may reduce the use of physical restraints.

Pharmacological profile of the potentiation of opioid analgesia by restraint stress

Morphine-treated rats exposed to restraint stress show potentiated magnitude and duration of analgesia compared to unstressed rats. The present study was performed to assess the pharmacological characteristics of stress-induced potentiation of opioid analgesia. We tested 10 opioids to determine whether restraint stress treatment would potentiate their ability to produce antinociception indexed by the tail-flick assay. We tested full mu, delta and kappa opioid receptor agonists (fentanyl, meperidine, DPDPE, U50488H, ethylketocyclazocine), and mixed agonist/ antagonists representing a range of receptor selectivities and intrinsic activities (profadol, buprenorphine, pentazocine, butorphanol and nalbuphine). Dose-effect and time-response curves were generated for unrestrained and restrained rats after either subcutaneous (SC) and/or intracerebroventricular (ICV) injections. In restrained rats, all drugs except for SC-administered nalbuphine produced dose- and time-dependent analgesic effects of greater magnitude (1.5–3 times) than they produced in unrestrained rats. However, restrained rats given agonists with high intrinsic activity at the μ receptor displayed the most potent and consistent potentiation of analgesia compared to unrestrained controls. Our results suggest that activation of the μ receptor is of primary importance for restraint to potentiate analgesia, because restrained rats injected with δ and κ agonists displayed potentiation of analgesia only at doses high enough to possibly exceed the selective activation of their respective receptor types.

Paradoxical DSP-4 effects: protection against gastric erosions and depletion of musocal glycoproteins

We have previously reported that rats pretreated with the central noradrenergic neurotoxin DSP-4 are protected against 23 h restraint-induced gastric erosions. To elucidate the peripheral mechanisms of this protection, we undertook direct biochemical analyses of the gastric mucosa in terms of glycoproteins and proteins. A simple method for preparation of gastric mucosa devoide of the muscular stomach wall tissue is described. A restrain-induced decrease in gastric wet weight and mucosal glycoprotein content was revealed. Restraint had no effect no mucosal protein content, and no changes were found in gastric wall glycoprotein or protein content. Despite showing protection against restrain-induced gastric erosions, unrestrained DSP-4-treated animals exhibited reduced mucosal wet weight mucosal glycoprotein content when compared to unrestrained controls. After the stress period, no significant differences on mucosal weight or glycoproteins could be detected between control and DSP-4 treated animals. The results indicate that the protective effect of DSP-4 in this paradign is not due to enhanced gastric mucosal protection against erosive factors. We suggest that an additional effect of central nervous NA depletion by DSP-4 may be elimination of aggresive factors which precipitate overt ulcers.

Effects of localised tumour hyperthermia on pimonidazole (Ro 03-8799) pharmacokinetics in mice.

We have investigated the effects of localised tumour hyperthermia (LTH; 43.5 degrees C x 30 min) on the acute toxicity and pharmacokinetics of the hypoxic cell sensitizer pimonidazole (Ro 03-8799) in mice. There were three treatment groups: unrestrained controls, sham-treated and LTH treated mice. LTH had minimal effects on the acute toxicity (LD50/7d) of pimonidazole with no significant difference between the three treatment groups. Pharmacokinetic studies were carried out at the maximum tolerated dose (MTD; approximately 60% LD50) of 437 micrograms g-1 i.v. in plasma, brain and tumour. Sham tumour treatment consistently increased plasma drug concentrations compared to unrestrained controls but had minimal effects on the elimination t1/2. The AUC0-infinitive was increased by 35% and the plasma clearance decreased by 26%. By contrast, LTH had minimal effects on these parameters compared to sham treatment. Brain pimonidazole concentrations were increased in restrained mice (sham and LTH treatments) compared to unrestrained controls, but average brain/plasma ratios were similar in all three groups at between 400 and 500%. Sham tumour treatment markedly reduced peak tumour pimonidazole concentrations compared to unrestrained controls giving a 29% lower AUC0-180min. Average tumour/plasma ratios were reduced from 236 to 129%. The most important finding was that LTH further reduced pimonidazole tumour concentrations, giving a 31% lower AUC0-180 min compared to sham treated tumours. Tumour/plasma ratios for pimonidazole were reduced by 41%. Plasma exposure to the pimonidazole N-oxide metabolite, Ro 31-0313, was unaltered by LTH. The markedly reduced drug concentrations in heated tumours may be a result of hyperthermia-stimulated bioreductive drug activation.

Predictable and unpredictable shock stimulates gastric contractility and causes mucosal injury in rats.

The effects of tailshock on gastric contractility and lesions were investigated in rats exposed to 100 1-mA tailshocks while confined inside plastic tubes. A light preceded each shock in one group and was randomly presented with respect to shock in the other. Following the session, animals were given 3 hr of rest before being sacrificed. Contractility of the corpus of the stomach was measured by means of chronically implanted extraluminal force transducers. Contractility was measured in 10-min blocks and analyzed by computer. Lesions were quantified by inspection; quantitative histology was performed on corpus and antrum sections. Signaled (n = 13) and unsignaled (n = 17) shock stimulated high-amplitude gastric contractions in fasted rats, which continued for 2 hr after the shock session. Cumulative contractile activity (1.5-hr shock plus 2-hr rest) in shocked animals was twice that in restrained and unrestrained control animals (n = 19, p less than .05), and contractile activity had a 30%-40% greater average amplitude than after a meal. Compared with unrestrained controls, shocked rats had visibly more mucosal injury (2.2 +/- 0.5 mm2 vs. 0.1 +/- 0 mm2). Larger cumulative contractile activity was associated with a larger area of erosions (r = .36, p less than .05). Frequency and duration of contractions did not distinguish between shocked and unshocked groups. We conclude that in rats, signaled and unsignaled tailshock stimulates persistent, high-amplitude gastric contractions and is associated with injury of the mucosa of the stomach.

Protection from lethal audiogenic seizures in mice by physical restraint of movement

To study the effects of physical restraint on audiogenic seizures, susceptible mice were restrained in various ways and compared with unrestrained controls for lethal seizures. Binding the front limbs together and/or the back limbs together, suspending subjects with harnesses, or restraining subjects in “body casts” were not effective in inhibiting lethal seizures, but binding subjects in “hogtied” fashion was quite effective in reducing the incidence of lethal seizures. Various hypotheses were evaluated in light of the present results. The most plausible hypothesis related protection from seizures to disruption of central neural activity normally evoked by bodily movements during audiogenic seizures.