Effects of physical training on hypothalamic neuronal activation and expressions of vasopressin and oxytocin in SHR after running until fatigue.

To assess the influence of physical training on neuronal activation and hypothalamic expression of vasopressin and oxytocin in spontaneously hypertensive rats (SHR), untrained and trained normotensive rats and SHR were submitted to running until fatigue while internal body and tail temperatures were recorded. Hypothalamic c-Fos expression was evaluated in thermoregulatory centers such as the median preoptic nucleus (MnPO), medial preoptic nucleus (mPOA), paraventricular nucleus of the hypothalamus (PVN), and supraoptic nucleus (SON). The PVN and the SON were also investigated for vasopressin and oxytocin expressions. Although exercise training improved the workload performed by the animals, it was reduced in SHR and followed by increased internal body temperature due to tail vasodilation deficit. Physical training enhanced c-Fos expression in the MnPO, mPOA, and PVN of both strains, and these responses were attenuated in SHR. Vasopressin immunoreactivity in the PVN was also increased by physical training to a lesser extent in SHR. The already-reduced oxytocin expression in the PVN of SHR was increased in response to physical training. Within the SON, neuronal activation and the expressions of vasopressin and oxytocin were reduced by hypertension and unaffected by physical training. The data indicate that physical training counterbalances in part the negative effect of hypertension on hypothalamic neuronal activation elicited by exercise, as well as on the expression of vasopressin and oxytocin. These hypertension features seem to negatively influence the workload performed by SHR due to the hyperthermia derived from the inability of physical training to improve heat dissipation through skin vasodilation.

The role of peripheral transient receptor potential vanilloid 1 channels in stress-induced hyperthermia in rats subjected to an anxiogenic environment.

Anxiety resulting from psychogenic stimuli elicit stress-induced hyperthermia in rats, often called "psychogenic fever", which is part of a coordinated response to situations seen as novel or distressing. Brain transient receptor potential vanilloid 1 (TRPV1) channels modulate both thermoregulation and animal behavior; however, the role of peripheral TRPV1 channels in regulating these responses during exposure to an anxiogenic environment has not been determined. Thus, the present study aimed to investigate the involvement of abdominal TRPV1 channels in stress-induced hyperthermia and behavior in rats subjected to an unconditioned anxiety test. Desensitized rats (peripheral desensitization of TRPV1 channels with resiniferatoxin; RTX) and their respective controls were subjected to a 15-min open field (OF) test. The core body temperature (Tcore), tail skin temperature (Tskin), and rats' movements inside the arena were recorded. The OF test induced a similar increase in Tcore in both groups throughout the exposure time; however, at the recovery period, the RTX-treated rats had a slower reduction in Tcore due to lower tail skin heat loss. Tskin decreased significantly in both groups during exposure to OF but, during recovery, the RTX-treated rats showed impaired skin vasodilation. Also, RTX-treated rats entered fewer times and spent less time in the OF center square, suggesting an anxiety-related behavior. Our findings indicate that, under stressful conditions, peripheral TRPV1 channels modulate thermoregulatory and behavioral responses. The TRPV1 desensitization induces a more prolonged hyperthermic response due to lower cutaneous heat dissipation, alongside a more evident anxiety-like behavior in rats subjected to the OF apparatus.

Early maternal separation alters the activation of stress-responsive brain areas in adulthood.

The expression of c-Fos protein has been extensively used as a marker of neuronal activation in response to stressful stimuli. Early maternal separation (MS) is a model of early life adversity that affects the responsiveness of the brain areas to stressors. Thus, this study examined the impact of early MS on activating stress-responsive areas in the brain of adult rats in response to physical (ether) or psychological (restraint) stressors. Male pups were divided for the MS or non-handled (NH) groups. The MS was carried out daily between the 2nd and 14th day of postnatal life and consisted in removing the dams from the cage for 180 min. The rats were then subjected to experimental protocols of restraint or ether exposure at 10-12 weeks old. The rats were anesthetized 90 min after exposure to the stressors, and their brains were prepared for immunohistochemical analysis of c-Fos immunoreactive (c-Fos-ir) neurons in the hypothalamic paraventricular nucleus (PVN), supraoptic nucleus (SON), medial preoptic area (MPA), medial amygdaloid nucleus (MeA), locus coeruleus (LC), and nucleus of the solitary tract (NST). The MS-group presented 86%, 125%, 73%, 56%, and 137% higher c-Fos-ir neurons in the LC, PVN, SON, MPA, and MeA, respectively, compared to NH-group in response to the restraint stressor. In addition, the MS-group presented 180%, 137%, 170%, and 138% higher c-Fos-ir neurons for the ether exposure in the LC, PVN, MPA, and MeA, respectively. Our results show a greater increase in neuronal activation in the MS group, indicating that early life adversity can induce reprogramming in the brain response to stress in adulthood.

Survey of off-label prescribing in a university paediatric outpatient in Brazil.

Ours is a cross-sectional, descriptive, retrospective study evaluating the extent of off-label prescribing for patients attending a university paediatric outpatient department in Goiás, Brazil. 391 patients were treated in the outpatient, and 668 medicines were prescribed. Of these, 70.4% followed the terms of the marketing authorization; 0.3% were unlicenced, and 11% were off-label. Dose was the main factor in off-label prescribing. Infants (0-2 years) received 37.8% of the off-label prescriptions. Vitamins and drugs for the treatment of respiratory diseases were the most prevalent culprits. Of the total prescriptions, 23 different drugs were defined as off-label. Salbutamol was the most prescribed (41.9%). Owing to practical and legal difficulties in carrying out clinical trials, medicines are inadequately studied in children; cooperation between industry, regulatory authorities, and healthcare professionals is required to improve treatment safety. Our results may help guide clinical researcher on off-label prescripting in future trials.

The time-course of thermoregulatory responses during treadmill running is associated with running duration-dependent hypothalamic neuronal activation in rats.

This study evaluated the hypothalamic neuronal activation during exercise and investigated whether this activation is related to heat storage and exercise duration. Rats were subjected to a treadmill running that was interrupted at three different moments: (1) at the early phase, when minimal heat dissipation occurred due to tail vasoconstriction and the tail skin temperature (Tskin) reached its nadir; (2) at the steady-state phase, when both the Tskin and core body temperature (Tcore) plateaued at a high level (~ 20 min); and (3) at fatigue, when Tcore and Tskin were still elevated. c-Fos expression in the medial and ventromedial preoptic areas (mPOA and vmPOA), median preoptic nucleus (MnPO), paraventricular and supraoptic nucleus (PVN and SON), and septohypothalamic nucleus (SHy) was determined. Exercise increased the expression of c-Fos in all brain areas, but with different activation patterns of activation. c-Fos expression in the SHy and vmPOA was similar in all exercising groups, while in the mPOA, MnPO, and PVN, c-Fos expression gradually increased during exercise. Increased c-Fos in the SON was only evident after 20 min of exercise. Neuronal activation in the mPOA, MnPO, PVN, and SON was positively correlated with both exercise duration and heat storage. Our findings indicate that with the exception of SON, the brain areas analyzed are recruited following small changes in Tcore (~ 0.5 °C), while the SON is recruited only when Tcore reaches higher values (greater than 1.0 °C increase). c-Fos expression in the PVN, mPOA, MnPO, and SON is also influenced by exercise duration, which does not occur in the SHy and vmPOA.

Central blockade of nitric oxide transmission impairs exercise-induced neuronal activation in the PVN and reduces physical performance.

The blockade of central nitric oxide (NO) signaling modifies the thermoregulatory and metabolic adjustments that occur during exercise, thereby impairing physical performance. However, the brain areas involved in this response remain unknown. Nitrergic neurons are present in the hypothalamic areas that are activated during exercise and participate in autonomic and neuroendocrine responses, such as, the hypothalamic paraventricular nucleus (PVN) and the supraoptic nucleus (SON). To investigate whether brain NO signaling affects thermoregulation during exercise through the activation of hypothalamic neurons, rats underwent acute submaximal treadmill exercise (18 mmin(-1), 5% inclination) until fatigue received an intracerebroventricular injection of 1.43 µmol Nω-nitro-l-arginine metil ester (L-NAME), a nitric oxide synthase inhibitor, or saline (SAL). Skin tail temperature (Tsk) and internal body temperature (Ti) were continuously recorded and c-Fos expression was determined in the PVN and the SON. L-NAME treatment reduced physical performance by 48%, which was positively correlated with tail vasodilation capacity, which was reduced by 28%, and negatively correlated with heat storage rate (HSR), which was increased by 38%. Physical exercise until fatigue increased the number of c-Fos-immunoreactive (ir) neurons in the PVN and the SON. L-NAME-treatment significantly reduced the exercise-induced c-Fos expression in the PVN, whereas it had no effect in the SON. Interestingly, the number of c-Fos-ir neurons in the PVN was closely correlated with physical performance and inversely associated with HSR. Thus, the inhibition of central NO attenuates neuronal activation induced by exercise in the PVN, impairs the autonomic regulation of heat dissipation, and anticipates the fatigue. Brain NO seems to play a role in exercise performance through the regulation of neuronal activation in the PVN, but not in the SON, although the SON neurons are also activated by running exercise. Moreover, this role in performance mediated by neuronal activation in the PVN can be related with the improvement of thermoregulatory adjustments that occur during exercise.

Treadmill exercise induces neutrophil recruitment into muscle tissue in a reactive oxygen species-dependent manner. An intravital microscopy study.

Intense exercise is a physiological stress capable of inducing the interaction of neutrophils with muscle endothelial cells and their transmigration into tissue. Mechanisms driving this physiological inflammatory response are not known. Here, we investigate whether production of reactive oxygen species is relevant for neutrophil interaction with endothelial cells and recruitment into the quadriceps muscle in mice subjected to the treadmill fatiguing exercise protocol. Mice exercised until fatigue by running for 56.3±6.8 min on an electric treadmill. Skeletal muscle was evaluated by intravital microscopy at different time points after exercise, and then removed to assess local oxidative stress and histopathological analysis. We observed an increase in plasma lactate and creatine kinase (CK) concentrations after exercise. The numbers of monocytes, neutrophils, and lymphocytes in blood increased 12 and 24 hours after the exercise. Numbers of rolling and adherent leukocytes increased 3, 6, 12, and 24 hours post-exercise, as assessed by intravital microscopy. Using LysM-eGFP mice and confocal intravital microscopy technology, we show that the number of transmigrating neutrophils increased 12 hours post-exercise. Mutant gp91phox-/- (non-functional NADPH oxidase) mice and mice treated with apocynin showed diminished neutrophil recruitment. SOD treatment promoted further adhesion and transmigration of leukocytes 12 hours after the exercise. These findings confirm our hypothesis that treadmill exercise increases the recruitment of leukocytes to the postcapillary venules, and NADPH oxidase-induced ROS plays an important role in this process.