Activation of 5-HT2C receptors in the dorsal periaqueductal gray increases antinociception in mice exposed to the elevated plus-maze

Several findings have pointed to the role of the dorsal periaqueductal gray (dPAG) serotonin 5-HT1A and 5-HT2(A-C) receptor subtypes in the modulation of defensive behavior in animals exposed to the elevated plus-maze (EPM). Besides displaying anxiety-like behavior, rodents also exhibit antinociception in the EPM. This study investigated the effects of intra-dPAG injections of 5-HT1A and 5-HT2B/2C receptor ligands on EPM-induced antinociception in mice. Male Swiss mice received 0.1 mu l intra-dPAG injections of vehicle, 5.6 and 10 nmol of 8-OHDPAT, a 5-HT1A receptor agonist (Experiment 1), or 0.01, 0.03 and 0.1 nmol of mCPP, a 5-HT2B/2C receptor agonist (Experiment 2). Five minutes later, each mouse received an intraperitoneal injection of 0.6% acetic acid (0.1 ml/10 g body weight; nociceptive stimulus) and was individually confined in the open (OA) or enclosed (EA) arms of the EPM for 5 min, during which the number of abdominal writhes induced by the acetic acid was recorded. While intra-dPAG injection of 8-OHDPAT did not change open-arm antinociception (OAR). mCPP (0.01 nmol) enhanced it. Combined injections of ketanserin (10 nmol/0.1 mu l), a 5-HT2A/2C receptor antagonist, and 0.01 nmol of mCPP (Experiment 3), selectively and completely blocked the OAR enhancement induced by mCPP. Although intra-dPAG injection of mCPP (0.01 nmol) also produced antinociception in EA-confined mice (Experiment 2), this effect was not confirmed in Experiment 3. Moreover, no other compound changed the nociceptive response in EA-confined animals. These results suggest that the 5-HT2C receptors located within the PAG play a role in this type of environmentally induced pain inhibition in mice. (c) 2012 Elsevier B.V. All rights reserved.

Cardiovascular effects of the microinjection of L-proline into the third ventricle or the paraventricular nucleus of the hypothalamus in unanesthetized rats

We investigated the cardiovascular effects of the microinjection of L-proline (L-Pro) into the third ventricle (3V) and its peripheral mechanisms. Different doses of L-Pro into the 3V caused dose-related pressor and bradycardiac responses. The pressor response to L-Pro injected into the 3V was potentiated by intravenous pretreatment with the ganglion blocker pentolinium (5 mg/kg), thus excluding any significant involvement of the sympathetic nervous system. Because the response to the microinjection of L-Pro into the 3V was blocked by intravenous pretreatment with the V1-vasopressin receptor antagonist dTyr(CH2)5(Me)AVP (50 mu g/kg), it is suggested that these cardiovascular responses are mediated by a vasopressin release. The pressor response to the microinjection of L-Pro into the 3V was found to be mediated by circulating vasopressin, so, given that the paraventricular nucleus of the hypothalamus (PVN) is readily accessible from the 3V, we investigated whether the PVN could be a site of action for the L-Pro microinjected in the 3V. The microinjection of L-Pro (0.033 mu moles/0.1 mu l) into the PVN caused cardiovascular responses similar to those of injection of the 3V and were also shown to be mediated by vasopressin release. In conclusion, these results show that the microinjection of L-Pro into the 3V causes pressor and bradycardiac responses that could involve stimulation of the magnocellular cells of the PVN and release of vasopressin into the systemic circulation. Also, because the microinjection of L-Pro into the PVN caused a pressor response, this is the first evidence of cardiovascular effects caused by its injection in a supramedullary structure. (c) 2012 Wiley Periodicals, Inc.

Effect of simvastatin on passive strain-induced skeletal muscle injury in rats

Introduction: HMG-CoA reductase inhibitors are the most frequently prescribed drugs for treatment of lipid imbalance, but they have side effects, such as myopathy. Our aim was to assess the effect of simvastatin on the inflammatory process induced by skeletal muscle injury. Methods: Rats were divided into experimental groups [control group, simvastatin (20 mg/kg) group, group treated with simvastatin (20 mg/kg) and subjected to injury, and group subjected to injury only]. Histological analysis and analyses of creatine kinase activity and C-reactive protein were performed. Results: Animals treated with simvastatin exhibited significantly greater morphological and structural skeletal muscle damage in comparison to the control group and injured animals without treatment. Conclusions: Although simvastatin has a small anti-inflammatory effect in the early stage after a muscle strain injury, the overall picture is negative, as simvastatin increases the extent of damage to muscle morphology. Further studies are needed. Muscle Nerve 46: 908-913, 2012

Inhibition of iNOS induces antidepressant-like effects in mice: Pharmacological and genetic evidence

Recent evidence has suggested that systemic administration of non-selective NOS inhibitors induces antidepressant-like effects in animal models. However, the precise involvement of the different NOS isoforms (neuronal-nNOS and inducible-iNOS) in these effects has not been clearly defined yet. Considering that mediators of the inflammatory response, that are able to induce iNOS expression, can be increased by exposure to stress, the aim of the present study was to investigate iNOS involvement in stress-induced behavioral consequences in the forced swimming test (FST), an animal model sensitive to antidepressant drugs. Therefore, we investigated the effects induced by systemic injection of aminoguanidine (preferential iNOS inhibitor), 1400W (selective iNOS inhibitor) or n-propyl-L-arginine (NPA, selective nNOS inhibitor) in mice submitted to the FST. We also investigated the behavior of mice with genetic deletion of iNOS (knockout) submitted to the FST. Aminoguanidine significantly decreased the immobility time (IT) in the FST. 1400W but not NPA, when administered at equivalent doses considering the magnitude of their Ki values for iNOS and nNOS, respectively, reduced the IT, thus suggesting that aminoguanidine-induced effects would be due to selective iNOS inhibition. Similarly, iNOS KO presented decreased IT in the FST when compared to wild-type mice. These results are the first to show that selective inhibition of iNOS or its knockdown induces antidepressant-like effects, therefore suggesting that iNOS-mediated NO synthesis is involved in the modulation of stress-induced behavioral consequences. Moreover, they further support NO involvement in the neurobiology of depression. This article is part of a Special Issue entitled 'Anxiety and Depression'. (C) 2011 Elsevier Ltd. All rights reserved.

Moxonidine into the lateral parabrachial nucleus reduces renal and hormonal responses to cell dehydration

The deactivation of the inhibitory mechanisms with injections of moxonidine (alpha(2)-adrenoceptor/imidazoline receptor agonist) into the lateral parabrachial nucleus (LPBN) increases hypertonic NaCl intake by intra- or extracellular dehydrated rats. In the present study, we investigated the changes in the urinary sodium and volume, sodium balance, and plasma vasopressin and oxytocin in rats treated with intragastric (i.g.) 2 M NaCl load (2 ml/rat) combined with injections of moxonidine into the LPBN. Male Holtzman rats (n=5-12/group) with stainless steel cannulas implanted bilaterally into LPBN were used. Bilateral injections of moxonidine (0.5 nmol/0.2 mu l) into the LPBN decreased i.g. 2 M NaCIinduced diuresis (4.6 +/- 0.7 vs. vehicle: 7.4 +/- 0.6 ml/120 min) and natriuresis (1.65 +/- 0.29 vs. vehicle: 2.53 +/- 0.17 mEq/120 min), whereas the previous injection of the alpha(2)-adrenoceptor antagonist RX 821002 (10 nmol/0.2 mu l) into the LPBN abolished the effects of moxonidline. Moxonidine injected into the LPBN reduced i.g. 2 M NaCl-induced increase in plasma oxytocin and vasopressin (14.6 +/- 2.8 and 2.2 +/- 0.3 vs. vehicle: 25.7 +/- 7 and 4.3 +/- 0.7 pg/ml, respectively). Moxonidine injected into the LPBN combined with i.g. 2 M NaCl also increased 0.3 M NaCl intake (7.5 +/- 1.7 vs. vehicle: 0.5 +/- 0.2 mEq/2 h) and produced positive sodium balance (2.3 +/- 1.4 vs. vehicle: -1.2 +/- 0.4 mEq/2 h) in rats that had access to water and NaCl. The present results show that LPBN alpha(2)-adrenoceptor activation reduces renal and hormonal responses to intracellular dehydration and increases sodium and water intake, which facilitates sodium retention and body fluid volume expansion. (C) 2012 IBRO. Published by Elsevier Ltd. All rights reserved.

Into the Island: A new technique of non-invasive cortical stimulation of the insula

Study aim. - We describe a new neuronavigation-guided technique to target the posterior-superior insula (PSI) using a cooled-double-cone coil for deep cortical stimulation. Introduction. - Despite the analgesic effects brought about by repetitive transcranial magnetic stimulation (TMS) to the primary motor and prefrontal cortices, a significant proportion of patients remain symptomatic. This encouraged the search for new targets that may provide stronger pain relief. There is growing evidence that the posterior insula is implicated in the integration of painful stimuli in different pain syndromes and in homeostatic thermal integration. Methods. - The primary motor cortex representation of the lower leg was used to calculate the motor threshold and thus, estimate the intensity of PSI stimulation. Results. - Seven healthy volunteers were stimulated at 10 Hz to the right PSI and showed subjective changes in cold perception. The technique was safe and well tolerated. Conclusions. - The right posterior-superior insula is worth being considered in future studies as a possible target for rTMS stimulation in chronic pain patients. (c) 2012 Elsevier Masson SAS. All rights reserved.

Cardiovascular responses to glutamate microinjection in the dorsomedial periaqueductal gray of unanesthetized rats

The periaqueductal gray area (PAG) is a mesencephalic area involved in cardiovascular modulation. Glutamate (L-Glu) is an abundant excitatory amino acid in the central nervous system (CNS) and is present in the rat PAG. Moreover, data in the literature indicate its involvement in central blood pressure control. Here we report on the cardiovascular effects caused by microinjection of L-Glu into the dorsomedial PAG (dmPAG) of rats and the glutamatergic receptors as well as the peripheral mechanism involved in their mediation. The microinjection of L-Glu into the dmPAG of unanesthetized rats evoked dose-related pressor and bradycardiac responses. The cardiovascular response was significantly reduced by pretreatment of the dmPAG with a glutamatergic M-methyl-D-aspartate (NMDA) receptor antagonist (LY235959) and was not affected by pretreatment with a non-NMDA receptor antagonist (NBQX), suggesting a mediation of that response by the activation of NMDA receptors. Furthermore, the pressor response was blocked by pretreatment with the ganglion blocker pentolinium (5 mg/kg, intravenously), suggesting an involvement of the sympathetic nervous system in this response. Our results indicate that the microinjection of L-Glu into the dmPAG causes sympathetic-mediated pressor responses in unanesthetized rats, which are mediated by glutamatergic NMDA receptors in the dmPAG. (c) 2012 Wiley Periodicals, Inc.

Medial amygdaloid nucleus 5-HT2C receptors are involved in the hypophagic effect caused by zimelidine in rats

The medial amygdaloid nucleus (MeA) is a sub-region of the amygdaloid complex that has been described as participating in food intake regulation. Serotonin has been known to play an important role in appetite and food intake regulation. Moreover, serotonin 5-HT2C and 5-HT1A receptors appear to be critical in food intake regulation. We investigated the role of the serotoninergic system in the MeA on feeding behavior regulation in rats. The current study examined the effects on feeding behavior regulation of the serotonin reuptake inhibitor, zimelidine, administered directly into the MeA or given systemically, and the serotoninergic receptors mediating its effect. Our results showed that microinjection of zimelidine (0.2, 2 and 20 nmol/100 nL) into the MeA evoked dose dependent hypophagic effects in fasted rats. The selective 5-HT1A receptor antagonist WAY-100635 (18.5 nmol/100 nL) or the 5-HT1B receptor antagonist SB-216641 microinjected bilaterally into the MeA did not change the hypophagic effect evoked by local MeA zimelidine treatment. However, microinjection of the selective 5-HT2C receptor antagonist SB-242084 (10 nmol/100 nL) was able to block the hypophagic effect of zimelidine. Moreover, microinjection of the 5-HT2C receptor antagonist SB-242084 into the MeA also blocked the hypophagic effect caused by zimelidine administered systemically. These results suggest that MeA 5-HT2C receptors modulate the hypophagic effect caused by local MeA administration as well as by systemic zimelidine administration. Furthermore, 5-HT2C into the MeA could be a potential target for systemic administration of zimelidine. (C) 2012 Elsevier Ltd. All rights reserved.

Acetic acid- and phenyl-p-benzoquinone-induced overt pain-like behavior depends on spinal activation of MAP kinases, PI3K and microglia in mice

The acetic acid and phenyl-p-benzoquinone are easy and fast screening models to access the activity of novel candidates as analgesic drugs and their mechanisms. These models induce a characteristic and quantifiable overt pain-like behavior described as writhing response or abdominal contortions. The knowledge of the mechanisms involved in the chosen model is a crucial step forward demonstrating the mechanisms that the candidate drug would inhibit because the mechanisms triggered in that model will be addressed. Herein, it was investigated the role of spinal mitogen-activated protein (MAP) kinases ERK (extracellular signal-regulated kinase), JNK (Jun N-terminal Kinase) and p38, PI3K (phosphatidylinositol 3-kinase) and microglia in the writhing response induced by acetic acid and phenyl-p-benzoquinone, and flinch induced by formalin in mice. Acetic acid and phenyl-p-benzoquinone induced significant writhing response over 20 min. The nociceptive response in these models were significantly and in a dose-dependent manner reduced by intrathecal pre-treatment with ERK (PD98059), JNK (SB600125), p38 (SB202190) or PI3K (wortmannin) inhibitors. Furthermore, the co-treatment with MAP kinase and PI3K inhibitors, at doses that were ineffective as single treatment, significantly inhibited acetic acid- and phenyl-p-benzoquinone-induced nociception. The treatment with microglia inhibitors minocycline and fluorocitrate also diminished the nociceptive response. Similar results were obtained in the formalin test. Concluding. MAP kinases and PI3K are important spinal signaling kinases in acetic acid and phenyl-p-benzoquinone models of overt pain-like behavior and there is also activation of spinal microglia indicating that it is also important to determine whether drugs tested in these models also modulate such spinal mechanisms. (C) 2012 Elsevier Inc. All rights reserved.

Assessing Pathogenicity for Novel Mutation/Sequence Variants: The Value of Healthy Older Individuals

Improvement in DNA technology is increasingly revealing unexpected/unknown mutations in healthy persons and generating anxiety due to their still unknown health consequences. We report a 44-year-old healthy father of a 10-year-old daughter with bilateral coloboma and hearing loss, but without muscle weakness, in whom a whole-genome CGH revealed a deletion of exons 38-44 in the dystrophin gene. This mutation was inherited from her asymptomatic father, who was further clinically and molecularly evaluated for prognosis and genetic counseling (GC). This deletion was never identified by us in 982 Duchenne/Becker patients. To assess whether the present case represents a rare case of non-penetrance, and aiming to obtain more information for prognosis and GC, we suggested that healthy older relatives submit their DNA for analysis, to which several complied. Mutation analysis revealed that his mother, brother, and 56-year-old maternal uncle also carry the 38-44 deletion, suggesting it an unlikely cause of muscle weakness. Genome sequencing will disclose mutations and variants whose health impact are still unknown, raising important problems in interpreting results, defining prognosis, and discussing GC. We suggest that, in addition to family history, keeping the DNA of older relatives could be very informative, in particular for those interested in having their genome sequenced.

Thomsen or Becker myotonia? A novel autosomal recessive nonsense mutation in the CLCN1 gene associated with a mild phenotype

We describe a large Brazilian consanguineous kindred with 3 clinically affected patients with a Thomsen myotonia phenotype. They carry a novel homozygous nonsense mutation in the CLCN1 gene (K248X). None of the 6 heterozygote carriers show any sign of myotonia on clinical evaluation or electromyography. These findings confirm the autosomal recessive inheritance of the novel mutation in this family, as well as the occurrence of phenotypic variability in the autosomal recessive forms of myotonia. Muscle Nerve, 2012

Segregated anatomical input to sub-regions of the rodent superior colliculus associated with approach and defense

The superior colliculus (SC) is responsible for sensorimotor transformations required to direct gaze toward or a way from unexpected, biologically salient events. Significant changes in the external world are signaled to SC through primary multisensory afferents, spatially organized according to a retinotopic topography. For animals, where anunexpected event could indicate the presence of either predator or prey, early decisions to approach or avoid are particularly important. Rodents' ecology dictates predators are most often detected initially as movements in upper visual field (mapped in medial SC), while appetitive stimuli are normally found in lower visual field (mapped in lateral SC). Our purpose was to exploit this functional segregation to reveal neural sites that can bias or modulate initial approach or avoidance responses. Small injections of Fluoro-Gold were made into medial or lateral sub-regions of intermediate and deep layers of SC (SCm/SCl). A remarkable segregation of input to these two functionally defined areas was found. (i) There were structures that projected only to SCm (e.g., specific cortical areas, lateral geniculate and suprageniculate thalamic nuclei, ventromedial and premammillary hypothalamic nuclei, and several brain-stem areas) or SCl (e.g., primary somatosensory cortex representing upper body parts and vibrissae and parvicellular reticular nucleus in the brainstem). (ii) Other structures projected to both SCm and SCl but from topographically segregated populations of neurons (e.g., zona incerta and substantia nigra pars reticulata). (iii) There were a few brainstem areas in which retrogradely labeled neurons were spatially overlapping (e.g., pedunculopontine nucleus and locus coeruleus). These results indicate significantly more structures across the rat neuraxis are in a position to modulate defense responses evoked from SCm, and that neural mechanisms modulating SC-mediated defense or appetitive behavior are almost entirely segregated.

Vascular dementia

The epidemic growth of dementia causes great concern for the society. It is customary to consider Alzheimer's disease (AD) as the most common cause of dementia, followed by vascular dementia (VaD). This dichotomous view of a neurodegenerative disease as opposed to brain damage caused by extrinsic factors led to separate lines of research in these two entities. Indeed, accumulated data suggest that the two disorders have additive effects and probably interact; however it is still unknown to what degree. Furthermore, epidemiological studies have shown "vascular" risk factors to be associated with AD. Therefore, a clear distinction between AD and VaD cannot be made in most cases, and is furthermore unhelpful. In the absence of efficacious treatment for the neurodegenerative process, special attention must be given to the vascular component, even in patients with presumed mixed pathology. Symptomatic treatment of VaD and AD is similar, although the former is less effective. For prevention of dementia it is important to treat all factors aggressively, even in stroke survivors who do not show evidence of cognitive decline. In this review, we will give a clinical and pathological picture of the processes leading to VaD and discuss its interaction with AD. (c) 2012 Elsevier B.V. All rights reserved.

Differential Expression of Genes Involved in the Degeneration and Regeneration Pathways in Mouse Models for Muscular Dystrophies

The genetically determined muscular dystrophies are caused by mutations in genes coding for muscle proteins. Differences in the phenotypes are mainly the age of onset and velocity of progression. Muscle weakness is the consequence of myofiber degeneration due to an imbalance between successive cycles of degeneration/regeneration. While muscle fibers are lost, a replacement of the degraded muscle fibers by adipose and connective tissues occurs. Major investigation points are to elicit the involved pathophysiological mechanisms to elucidate how each mutation can lead to a specific degenerative process and how the regeneration is stimulated in each case. To answer these questions, we used four mouse models with different mutations causing muscular dystrophies, Dmd (mdx) , SJL/J, Large (myd) and Lama2 (dy2J) /J, and compared the histological changes of regeneration and fibrosis to the expression of genes involved in those processes. For regeneration, the MyoD, Myf5 and myogenin genes related to the proliferation and differentiation of satellite cells were studied, while for degeneration, the TGF-beta 1 and Pro-collagen 1 alpha 2 genes, involved in the fibrotic cascade, were analyzed. The result suggests that TGF-beta 1 gene is activated in the dystrophic process in all the stages of degeneration, while the activation of the expression of the pro-collagen gene possibly occurs in mildest stages of this process. We also observed that each pathophysiological mechanism acted differently in the activation of regeneration, with distinctions in the induction of proliferation of satellite cells, but with no alterations in stimulation to differentiation. Dysfunction of satellite cells can, therefore, be an important additional mechanism of pathogenesis in the dystrophic muscle.

Chronic Intermittent Hypoxia Depresses Afferent Neurotransmission in NTS Neurons by a Reduction in the Number of Active Synapses

Long-term synaptic plasticity has been recently described in brainstem areas associated to visceral afferent sensory integration. Chronic intermittent hypoxia (CIH), an animal model for studying obstructive sleep apnea in humans, depresses the afferent neurotransmission in nucleus tractus solitarii (NTS) neurons, which affect respiratory and autonomic regulation. Here we identified the synaptic mechanisms of CIH-induced depression of the afferent neurotransmission in NTS neurons in juvenile rats. We verified that CIH reduced the amplitude of both NMDA and non-NMDA glutamatergic excitatory currents (eEPSCs) evoked by tractus solitarii stimulation (TS-eEPSC) of second-order neurons in the NTS. No changes were observed in release probability, evidenced by absence of any CIH-elicited effects on short-term depression and failures in EPSCs evoked in low calcium. CIH also produced no changes in TS-eEPSC quantal size, since the amplitudes of both low calcium-evoked EPSCs and asynchronous TS-eEPSCs (evoked in the presence of Sr2+) were unchanged. Using single TS afferent fiber stimulation in slices from control and CIH rats we clearly show that CIH reduced the quantal content of the TS-eEPSCs without affecting the quantal size or release probability, suggesting a reduction in the number of active synapses as the mechanism of CIH induced TS-eEPSC depression. In accordance with this concept, the input-output relationship of stimulus intensity and TS-eEPSC amplitude shows an early saturation in CIH animals. These findings open new perspectives for a better understanding of the mechanisms underlying the synaptic plasticity in the brainstem sensory neurons under challenges such as those produced by CIH in experimental and pathological conditions.