Reduced sympathetic activity is associated with the development of pain and muscle atrophy in a female rat model of fibromyalgia.

Fibromyalgia (FM) is characterized by chronic widespread musculoskeletal pain accompanied by fatigue and muscle atrophy. Although its etiology is not known, studies have shown that FM patients exhibit altered function of the sympathetic nervous system (SNS), which regulates nociception and muscle plasticity. Nevertheless, the precise SNS-mediated mechanisms governing hyperalgesia and skeletal muscle atrophy in FM remain unclear. Thus, we employed two distinct FM-like pain models, involving intramuscular injections of acidic saline (pH 4.0) or carrageenan in prepubertal female rats, and evaluated the catecholamine content, adrenergic signaling and overall muscle proteolysis. Subsequently, we assessed the contribution of the SNS to the development of hyperalgesia and muscle atrophy in acidic saline-injected rats treated with clenbuterol (a selective ß2-adrenergic receptor agonist) and in animals maintained under baseline conditions and subjected to epinephrine depletion through adrenodemedullation (ADM). Seven days after inducing an FM-like model with acidic saline or carrageenan, we observed widespread mechanical hyperalgesia along with loss of strength and/or muscle mass. These changes were associated with reduced catecholamine content, suggesting a common underlying mechanism. Notably, treatment with a ß2-agonist alleviated hyperalgesia and prevented muscle atrophy in acidic saline-induced FM-like pain, while epinephrine depletion induced mechanical hyperalgesia and increased muscle proteolysis in animals under baseline conditions. Together, the results suggest that reduced sympathetic activity is involved in the development of pain and muscle atrophy in the murine model of FM analyzed.

Myrtenol Reduces Orofacial Nociception and Inflammation in Mice Through p38-MAPK and Cytokine Inhibition.

Orofacial pain is one of the commonest and most complex complaints in dentistry, greatly impairing life quality. Preclinical studies using monoterpenes have shown pharmacological potential to treat painful conditions, but the reports of the effects of myrtenol on orofacial pain and inflammation are scarce. The aim of this study was to evaluate the effect of myrtenol in experimental models of orofacial pain and inflammation. Orofacial nociceptive behavior and the immunoreactivity of the phosphorylated p38 (P-p38)-MAPK in trigeminal ganglia (TG) and spinal trigeminal subnucleus caudalis (STSC) were determined after the injection of formalin in the upper lip of male Swiss mice pretreated with myrtenol (12.5 and 25 mg/kg, i.p.) or vehicle. Orofacial inflammation was induced by the injection of carrageenan (CGN) in the masseter muscle of mice pretreated with myrtenol (25 and 50 mg/kg, i.p.) or its vehicle (0.02% Tween 80 in saline). Myeloperoxidase (MPO) activity and histopathological changes in the masseter muscle and interleukin (IL)-1ß levels in the TG and STSC were measured. The increase in face-rubbing behavior time induced by formalin and P-p38-MAPK immunostaining in trigeminal ganglia were significantly reduced by myrtenol treatment (12.5 and 25 mg/kg). Likewise, increased MPO activity and inflammatory histological scores in masseter muscle, as well as augmented levels of IL-1ß in the TG AND STSC, observed after CGN injection, were significantly decreased by myrtenol (25 and 50 mg/kg). Myrtenol has potential to treat orofacial inflammation and pain, which is partially related to IL-1ß levels in the trigeminal pathway and p38-MAPK modulation in trigeminal ganglia.

Sakuranetin exerts anticonvulsant effect in bicuculline-induced seizures.

Epilepsy is a chronic neurological disorder characterized by an abnormal, spontaneous, and synchronized neuronal hyperactivity. Therapeutic approaches for controlling epileptic seizures are associated with pharmacoresistance and side effects burden. Previous studies reported that different natural products may have neuroprotector effects. Sakuranetin (SAK) is a flavanone with antiparasitic, anti-inflammatory, antimutagenic, antiallergic, and antioxidant activity. In the present work, the effect of SAK on seizures in a model of status epilepticus induced by bicuculline (BIC) in mice was evaluated. Male Swiss mice received an intracerebroventricular injection (i.c.v.) of SAK (1, 10, or 20 mg/kg-SAK1, SAK10, or SAK20). Firstly, animals were evaluated in the open field (OF; 20 min), afterwards in the elevated plus maze (EPM) test (5 min). Next, 30 min prior the administration of BIC (1 mg/kg), mice received an injection of SAK (1 or 10 mg/kg, i.c.v.) and were observed in the OF (20 min) for seizures assessment. After behavioral procedures, immunohistochemical analysis of c-Fos was performed. Our main results showed that the lowest doses of SAK (1 and 10 mg/kg) increased the total distance traveled in the OF, moreover protected against seizures and death on the BIC-induced seizures model. Furthermore, SAK treatment reduced neuronal activity on the dentate gyrus of the BIC-treated animals. Taken together, our results suggest an anticonvulsant effect of SAK, which could be used for the development of anticonvulsants based on natural products from herbal source.

Myrtenol complexed with ß-cyclodextrin ameliorates behavioural deficits and reduces oxidative stress in the reserpine-induced animal model of Parkinsonism.

Current pharmacological approaches to treat Parkinson's disease have low long-term efficacy and important adverse side effects. The development of new pharmacological therapies has focused on novel plant-derived phytochemicals. The alcoholic monoterpene myrtenol has been isolated from several plant species, and has anxiolytic, analgesic, anti-inflammatory and antioxidant actions. Our study evaluated the neuroprotective potential of myrtenol complexed with ß-cyclodextrin (MYR) on a progressive parkinsonism model induced by reserpine (RES) in mice. The complexation with cyclodextrins enhances the pharmacological action of monoterpenes. Male Swiss mice were treated daily with MYR (5 mg/kg, p.o.) and with RES (0.1 mg/kg, s.c.) every other day during 28 days. Behavioural evaluations were conducted across treatment. At the end of the treatment, immunohistochemistry for tyrosine hydroxylase (TH) and oxidative stress parameters were evaluated. Chronic MYR-treatment protected against olfactory sensibility loss, restored short-term memory and decreased RES-induced motor impairments. Moreover, this treatment prevented dopaminergic depletion and reduced the oxidative status index in the dorsal striatum. Therefore, MYR ameliorated motor and non-motor impairments in the progressive animal model of parkinsonism, possibly by an antioxidant action. Additional research is needed to investigate the mechanisms involved in this neuroprotective effect.

Patterns of c-Fos expression in telencephalic areas of Tropidurus hygomi (Iguania: Tropiduridae) exposed to different social contexts.

Social behavior in lizards contributes to understanding biological standards and provides models for structuring research about neural mechanisms. Studies have confirmed the effectiveness of comparative models and evidence has contributed to clarifying adult brain plasticity phenomenon when exposed to different stimuli. The expression of c-Fos has been widely used to identify brain areas involved in different behavioral stimuli. The purpose of the present study was to map the expression of c-Fos protein in different telencephalic areas of the lizard Tropidurus hygomi after they were exposed to visual stimuli with another individual of the same species in different social contexts. Lizards were allocated to one of four groups: 1) control group (CTL) - males not exposed to any other animal; 2) exposure to juvenile (EJU) - males exposed to a juvenile; 3) exposure to male (EMA) - males exposed to another adult male; and 4) exposure to females (EFE) -males exposed to female. The EFE group exhibited a greater number of c-Fos + cells in cortical areas (medial cortex - MC and dorsomedial cortex - DMC) and in amygdala (AMY), showing a possible relationship between these structures and behavioral components. Studies like this can contribute significantly to a better understanding of neurophysiological, behavioral, and evolutive aspects.

Characterization of NADPH Diaphorase- and Doublecortin-Positive Neurons in the Lizard Hippocampal Formation.

The lizard cortex has remarkable similarities with the mammalian hippocampus. Both regions process memories, have similar cytoarchitectural properties, and are important neurogenic foci in adults. Lizards show striking levels of widespread neurogenesis in adulthood and can regenerate entire cortical areas after injury. Nitric oxide (NO) is an important regulatory factor of mammalian neurogenesis and hippocampal function. However, little is known about its role in nonmammalian neurogenesis. Here, we analyzed the distribution, morphology, and dendritic complexity (Neurolucida reconstructions) of NO-producing neurons through NADPH diaphorase (NADPHd) activity, and how they compare with the distribution of doublecortin-positive (DCX+) neurons in the hippocampal formation of the neotropical lizard Tropidurus hispidus. NADPHd-positive (NADPHd+) neurons in the dorsomedial cortex (DMC; putatively homologous to mammalian CA3) were more numerous and complex than the ones in the medial cortex (MC; putatively homologous to the dentate gyrus). We found that NADPHd+ DMC neurons send long projections into the MC. Interestingly, in the MC, NADPHd+ neurons existed in 2 patterns: small somata with low intensity of staining in the outer layer and large somata with high intensity of staining in the deep layer, a pattern similar to the mammalian cortex. Additionally, NADPHd+ neurons were absent in the granular cell layer of the MC. In contrast, DCX+ neurons were scarce in the DMC but highly numerous in the MC, particularly in the granular cell layer. We hypothesize that NO-producing neurons in the DMC provide important input to proliferating/migrating neurons in the highly neurogenic MC.

Morphological changes in the suprachiasmatic nucleus of aging female marmosets (Callithrix jacchus).

The suprachiasmatic nuclei (SCN) are pointed to as the mammals central circadian pacemaker. Aged animals show internal time disruption possibly caused by morphological and neurochemical changes in SCN components. Some studies reported changes of neuronal cells and neuroglia in the SCN of rats and nonhuman primates during aging. The effects of senescence on morphological aspects in SCN are important for understanding some alterations in biological rhythms expression. Therefore, our aim was to perform a comparative study of the morphological aspects of SCN in adult and aged female marmoset. Morphometric analysis of SCN was performed using Nissl staining, NeuN-IR, GFAP-IR, and CB-IR. A significant decrease in the SCN cells staining with Nissl, NeuN, and CB were observed in aged female marmosets compared to adults, while a significant increase in glial cells was found in aged marmosets, thus suggesting compensatory process due to neuronal loss evoked by aging.

Low temperature-acclimation impairs cellular migration in the adult cerebral cortex of the tropical lizard, Tropidurus hispidus (Spix, 1825) (Squamata: Tropiduridae).

The effects of different temperature-acclimations on cellular proliferation and migration were studied in the cerebral cortex of the tropical lizard, Tropidurus hispidus. Lizards were divided in two groups: warm-acclimated lizards (WALs), maintained at the temperature and photoperiod conditions of their natural habitat (mean temperature 26°C; 12:12 light:dark) and the cold-acclimated lizards (CALs), maintained at the same cycle of illumination and a mean temperature of 16°C. Animals were injected with the proliferative marker 5-bromodeoxyuridine (BrdU) and euthanized fifteen or thirty days later for the immunostaining. There was no difference in the number of BrdU-positive nuclei between the experimental groups in any of the cortical layers. In CALs, the positive nuclei were found mostly close to the ependyma, whereas in WALs many positive nuclei were also found in the plexiform and cellular layers of the cortex. In CALs, BrdU-positive nuclei appeared grouped (of 2-3 nuclei), a characteristic not seen in the other group. These data suggest that temperature affects the migrating capability of the newly generated neurons in the lizard cortex, but appears not to interfere with its generation.

Structural organization of the cerebral cortex of the neotropical lizard Tropidurus hispidus.

Lizards belonging to the Tropiduridae family are "sit-and-wait" foragers, relying mainly on visual identification to catch prey that cross their visual fields. Little is known about the neurobiology of Tropiduridae lizards. We have used neurohistological techniques to study the structural organization of the telencephalon of the neotropical lizard Tropidurus hispidus, paying special attention to the cerebral cortex. As revealed by the Nissl technique and Golgi staining, the telencephalon of T. hispidus follows the squamate pattern, with some differences: the lateral cortex appears relatively atrophic, and most of the neuronal somata of the dorsal cortex are dispersed without forming a conspicuous cell layer. Golgi staining has revealed ten different neuronal types in the three cortical layers, based on somata shape and dendritic morphology: the granular (unipolar, bipolar, and multipolar), pyramidal (normal, inverted, open, bipyramidal, and horizontal), spherical horizontal, and fusiform neuronal types. The axon direction could be traced in five of the subtypes. We have also studied the distribution of zinc-enriched terminals in the telencephalon of T. hispidus by the Neo-Timm method. Some portions of the cortex, septum, striatum, and amygdaloid complex stain heavily, with patterns resembling those described for other lizard families. Thus, T. hispidus appears to be an interesting representative of the Tropiduridae family for further neurobiological comparative studies.

Expression of the immediate-early gene egr-1 and substance P in the spinal cord following locomotor training in adult rats.

The immediate-early gene egr-1 has been shown to have an increased expression during long-term potentiation (LTP). High frequency electrical stimulation induces an increase in such expression in the dorsal horn of the spinal cord. However, evidence demonstrating the activation of this gene in the spinal cord and its relationship with LTP is still scarce. The substance P (SP) has also been associated with LTP in the dorsal horn of the spinal cord following high frequency stimulation. Here we evaluated the expression of both Egr-1 and SP in the sacrolumbar area of the spinal cord after locomotor training in adult rats. Increased neuronal Egr-1 expression was found in the spinal cord sections in rats that underwent locomotor training, especially in laminae IV and X across L3-S4 levels (p<0.05). Conversely, SP expression in synaptic terminals was not altered in the abovementioned regions. Our results suggest that locomotor training activates mechanisms in a similar way to LTP, and is involved in the synaptic plasticity in the spinal cord. The results also indicate that variations in the training protocol influence Egr-1 expression. Such events appear not to be directly influenced by SP, which suggests a plastic process that differs from those triggered by nociceptive stimuli.