Sex-specific Stress and Behavioural Responses to Human Experimenters in Rats

The sex of the experimenter may cause stress in animal models and be a major confounding factor in preclinical research. We studied the effects of the sex of the experimenter on female and male rat anxiety behaviours using thigmotaxis in the open field test, anxiety-induced changes in brain and back temperature using infra-red thermography, and alterations in plasma concentrations of stress hormones, corticosterone and oxytocin. Female rats displayed consistently exacerbated anxiety-related behaviours along with increased infrared cutaneous temperature during repeated exposure to male experimenters. Experimental stress further intensified thermal responses to a male experimenter, especially in female rats. These behavioural responses to a male experimenter in females were associated with higher circulating corticosterone and lower oxytocin levels. Similar responses were induced by a T-shirt worn by a human male. These findings suggest that emotional and physiological responses of female rats to a male experimenter are influenced by visual and olfactory cues. These results emphasize the need to standardize and report experimenter sex throughout a study to avoid ambiguity in interpretation of the results.

Usefulness of infrared thermography in diagnosing and evaluating severity of carpal tunnel syndrome

Background: Pain and autonomic dysfunction are prominent symptoms in some patients with carpal tunnel syndrome (CTS). Infrared thermography (IRT) has been used to evaluate CTS by measuring the cutaneous temperature and sympathetic vasomotor function.Methods: This study enrolled the 66 hands of 33 subjects, some of which had clinical CTS and the others were healthy. The enrolled patients completed the Boston Carpal Tunnel Questionnaire (BCTQ) and Historical-Objective scale, and underwent nerve conduction studies (NCSs) and IRT. Skin temperature was measured at the fingertips and the thenar and hypothenar regions in each hand. We analyzed (1) the correlations between self-reported severity, physician-assessed severity, and test results, and (2) the sensitivity and specificity of IRT in diagnosing CTS.Results: No significant correlation was observed between the results of the BCTQ, NCS, and IRT. IRT had a low sensitivity and high specificity in diagnosing CTS.Conclusions: IRT cannot replace NCS in diagnosing CTS, nor did it provide an advantage in combination with NCS. However, lower temperatures at the median nerve in some hands with moderate-to-severe CTS suggested the involvement of sympathetic nerve fiber function. Follow-up studies with a larger-scale and complementary design are required to elucidate the relationships.

Perception of Thermal Comfort during Skin Cooling and Heating

Due to the static and dynamic activity of the skin temperature sensors, the cutaneous thermal afferent information is dependent on the rate and direction of the temperature change, which would suggest different perceptions of temperature and of thermal comfort during skin heating and cooling. This hypothesis was tested in the present study. Subjects (N = 12; 6 females and 6 males) donned a water-perfused suit (WPS) in which the temperature was varied in a saw-tooth manner in the range from 27 to 42 °C. The rate of change of temperature of the water perfusing the suit (TWPS) was 1.2 °C min−1 during both the heating and cooling phases. The trial was repeated thrice, with subjects reporting their perception of the temperature and thermal comfort at each 3 °C change in TWPS. In addition, subjects were instructed to report when they perceived TWPS uncomfortably cool and warm during cooling and heating, respectively. Subjects reproducibly identified the boundaries of their Thermal Comfort Zone (TCZ), defined as the lower (Tlow) and upper (Thigh) temperatures at which subjects reported slight thermal discomfort. During the heating phase, Tlow and Thigh were 30.0 ± 1.5 °C and 35.1 ± 2.9 °C, respectively. During the cooling phase, the boundary temperatures of Tlow and Thigh were 35.4 ± 1.9 °C and 38.7 ± 2.3 °C, respectively. The direction of the change in the cutaneous temperature stimulus affects the boundaries of the TCZ, such that they are higher during cooling and lower during heating. These findings are explained on the basis of the neurophysiology of thermal perception. From an applied perspective, the most important observation of the present study was the strong correlation between the perception of thermal comfort and the behavioral regulation of thermal comfort. Although it is not surprising that the action of regulating thermal comfort is aligned with its perception, this link has not been proven for humans in previous studies. The results therefore provide a sound basis to consider ratings of thermal comfort as reflecting behavioral actions to achieve the sensation of thermal neutrality.

Body temperature and esthesia in individuals with stroke

Patients with sequelae of stroke commonly report somatosensory losses. It is believed that body temperature may be associated with tactile sensibility and sensorimotor recovery of these patients. Demonstrate the associations among tactile sensibility, cutaneous temperature, subjective temperature perception, and sensorimotor recovery of patients with stroke sequelae. 86 patients with stroke sequelae were included. Patients had standardized regions of interest (ROIs) assessed with infrared thermography (FLIR T650SC) and monofilaments esthesiometry, and global motor recovery was evaluated with Fugl-Meyer Assessment (FMA). The presence of self-reported perception of temperature difference was used to divide the participants into two groups of 43 patients, and correlation tests were applied to establish correlations among variables. There is no clinically relevant association between tactile sensibility and cutaneous temperature of the foot, regardless of the subjective sensation of temperature changes. Sensorimotor recovery evaluated by FMA is associated with the difference of sensibility between both sides of the body (p < 0.001), as well as with the difference of tactile sensibility (p < 0.001). A clinically significant association between the difference of cutaneous temperature and tactile sensibility was not found, regardless of the presence or absence of subjective perception of such temperature difference. However, sensorimotor recovery is correlated with cutaneous temperature differences and tactile sensibility.

Chronic ethanol vapor exposure potentiates cardiovascular responses to acute stress in male but not in female rats

Background Ethanol use is related to a wide variety of negative health outcomes, including cardiovascular diseases. Stress is also involved in numerous pathologies, such as cardiovascular diseases and psychiatric disorders. Sexual dimorphism is an important factor affecting cardiovascular response and has been proposed as a potential risk factor for sex-specific health problems in humans. Here, we evaluated the effect of prolonged ethanol vapor inhalation on arterial pressure, heart rate, and tail skin temperature responses to acute restraint stress, investigating differences between male and female rats. Methods We exposed male and female Long-Evans rats to ethanol vapor for 14 h, followed by ethanol withdrawal for 10 h, for 30 consecutive days, or to room air (control groups). The animals underwent surgical implantation of a cannula into the femoral artery for assessment of arterial pressure and heart rate values. The tail skin temperature was measured as an indirect measurement of sympathetic vasomotor response. Results Chronic ethanol vapor inhalation reduced basal heart rate in both female and male rats. Sex-related difference was observed in the decrease of tail cutaneous temperature evoked by stress, but not in the pressor and tachycardiac responses. Furthermore, prolonged ethanol inhalation enhanced the blood pressure and heart rate increase caused by acute restraint stress in male, but not in female rats. However, no effect of chronic ethanol vapor was observed in the tail cutaneous temperature response to restraint in either sex. Conclusion Chronic ethanol vapor exposure increased the cardiovascular reactivity to stress in male, but not in female rats.

Chronic ethanol vapor exposure potentiates cardiovascular responses to acute stress in male but not in female rats

Background: Ethanol use is related to a wide variety of negative health outcomes, including cardiovascular diseases. Stress is also involved in numerous pathologies such as cardiovascular diseases and psychiatric disorders. Sexual dimorphism is an important factor affecting cardiovascular response and has been proposed as a potential risk factor for sex-specific health problems in humans. Here, we evaluated the effect of prolonged ethanol vapor inhalation on arterial pressure, heart rate and tail skin temperature responses to acute restraint stress, investigating differences between male and female rats. Methods: We exposed male and female Long-Evans rats to ethanol vapor for 14 hours, followed by ethanol withdrawal for 10 hours, for 30 consecutive days, or to room air (control groups). The animals underwent surgical implantation of a cannula into the femoral artery for assessment of arterial pressure and heart rate values. The tail skin temperature was measured as an indirect measurement of sympathetic vasomotor response. Results: Chronic ethanol vapor inhalation reduced basal heart rate in both female and male rats. Sex-related difference was observed in the decrease of tail cutaneous temperature evoked by stress, but not in the pressor and tachycardiac responses. Furthermore, prolonged ethanol inhalation enhanced the blood pressure and heart rate increase caused by acute restraint stress in male, but not in female rats. However, no effect of chronic ethanol vapor was observed in the tail cutaneous temperature response to restraint in either sex. Conclusion: Chronic ethanol vapor exposure increased the cardiovascular reactivity to stress in male, but not in female rats.