Agglutinin isolated from the red marine alga Hypnea cervicornis J. Agardh reduces inflammatory hypernociception: Involvement of nitric oxide

Hypnea cervicornis agglutinin (HCA), a lectin isolated from the red marine alga has been previously shown to have an antinociceptive effect. In the present study in rats, mechanisms of action of HCA were addressed regarding mechanical hypernociception induced by carrageenan, ovalbumin (as antigen), and also by prostaglandin E(2) in rats. The lectin administered intravenously inhibited carrageenan- and antigen-induced hypernociception at 1,3, 5 and 7 h. This inhibitory effect was completely prevented when lectin was combined with mucin, demonstrating the role of carbohydrate-binding sites. The inhibition of inflammatory hypernociception by HCA was associated with the prevention of neutrophil recruitment to the plantar tissue of rats but was not associated with the inhibition of the release of pro-hypernociceptive cytokines (TNF-alpha, IL-1 beta and CINC-1). HCA also blocked mechanical hypernociception induced by PGE(2), which was prevented by the administration of nitric oxide synthase inhibitors. These results were corroborated by the increased circulating levels of NO metabolites following HCA treatment. These findings suggest that the anti-hypernociceptive effects of HCA are not associated with the inhibition of pro-inflammatory cytokine production. However, these effects seem to involve the inhibition of neutrophil migration and also the increase in NO production. (C) 2010 Elsevier Inc. All rights reserved.

Cannabidiol injected into the bed nucleus of the stria terminalis modulates baroreflex activity through 5-HT(1A) receptors

Cannabidiol (CBD) is a non-psychotomimetic constituent of the Cannabis sativa plant that inhibits behavioral and cardiovascular responses to aversive situations. facilitating 5-HT(1A)-mediated neurotransmission. Previous results from our group suggest that the bed nucleus of the stria terminalis (BNST) may be involved in CBD`s anti-aversive effects. To investigate whether the cardiovascular effects of the CBD could involve a direct drug effect on the BNST, we evaluated the effects of CBD microinjection into this structure on baroreflex activity. We also verified whether these effects were mediated by the activation of 5-HT(1A) receptors. Bilateral microinjection of CBD (60 nmol/100 nL) into the BNST increased the bradycardiac response to arterial pressure increases. However, no changes were observed in tachycardiac responses evoked by arterial pressure decreases. Pretreatment of the BNST with the selective 5-HT(1A) receptor antagonist WAY100635 (0.37 nmol/100 nL) prevented CBD effects on the baroreflex activity. Moreover, microinjection of the 5-HT(1A) receptor agonist 8-OH-DPAT (4 nmol/100 nL) caused effects that were similar to those observed after the microinjection of CBD, which were also blocked by pretreatment with WAY100635. In conclusion, the present studies show that the microinjection of CBD into the BNST has a facilitatory influence on the baroreflex response to blood pressure increases, acting through the activation of 5-HT(1A) receptors. (C) 2010 Elsevier Ltd. All rights reserved.

The lateral habenula regulates defensive behaviors through changes in 5-HT-mediated neurotransmission in the dorsal periaqueductal gray matter

Chemical stimulation of the lateral nucleus of the habenula (LHb), an area implicated in the regulation of serotonergic activity in raphe nuclei, affects the acquisition of inhibitory avoidance and escape expression of rats submitted to the elevated T-maze test of anxiety. Here, we investigated whether facilitation of 5-HT-mediated neurotransmission in the dorsal periaqueductal gray (dPAG) accounts for the behavioral consequences in the elevated T-maze induced by chemical stimulation of the LHb. The dPAG in the midbrain, which is innervated by 5-HT fibers originating from the dorsal raphe nucleus (DRN), has been consistently implicated in the genesis/regulation of anxiety- and fear-related defensive responses. The results showed that intra-dPAG injection of WAY-100635 or ketanserin, 5-HT(1A) and 5-HT(2A/2C) receptor antagonists, respectively, counteracted the anti-escape effect caused by bilateral intra-LHb injection of kainic acid (60 pmol/0.2 mu l). Ketanserin, but not WAY-100635, blocked kainic acid`s facilitatory effect on inhibitory avoidance acquisition. Overall, the results suggest that the pathway connecting the LHb to the DRN is involved in the control of 5-HT release in the dPAG, and facilitation of 5-HT-mediated neurotransmission in the latter area distinctively impacts upon the expression of anxiety- and fear-related defensive behaviors. While stimulation of 5-HT(1A) receptors selectively affects escape performance, 5-HT(2A/2C) receptors modulate both inhibitory avoidance and escape. (C) 2010 Elsevier Ireland Ltd. All rights reserved.

Effects of Lidocaine Infusion during Experimental Endotoxemia in Horses

Background The clinical efficacy of IV infusion of lidocaine for treatment of equine endotoxemia has not been studied. Hypothesis Lidocaine infusion after exposure to lipopolysaccharide (LPS) will inhibit the inflammatory response and have inhibitory effects on the hemodynamic and cytokine responses to endotoxemia. Animals Twelve horses. Methods Two equal groups (n = 6): saline (GI) and lidocaine (GII). In all animals, endotoxin (500 ng/kg body weight [BW]) was injected intraperitoneally over 5 minutes. Twenty minutes later, animals received a bolus of GI or GII (1.3 mg/kg BW) over 5 minutes, followed by a 6-hour continuous rate infusion of GI or GII (0.05 mg/kg BW/min). Treatment efficacy was judged from change in arterial blood pressure, peripheral blood and peritoneal fluid (PF) variables (total and differential cell counts, enzyme activities, and cytokine concentrations), and clinical scores (CS) for behavioral evidence of abdominal pain or discomfort during the study. Results Compared with the control group, horses treated with lidocaine had significantly lower CS and serum and PF tumor necrosis factor-alpha (TNF-alpha) activity. At several time points in both groups, total and differential cell counts, glucose, total protein and fibrinogen concentrations, and alkaline phosphatase, creatine kinase, and TNF-alpha activities were significantly different from baseline values both in peripheral blood and in PF. Conclusions and Clinical Importance Lidocaine significantly decreased severity of CS and inhibited TNF-alpha activity in PF.

Cannabidiol inhibitory effect on marble-burying behaviour: involvement of CB1 receptors

Cannabidiol (CBD) is a major nonpsychotomimetic component of Cannabis sativa that has been shown to have an anxiolytic effect in human and animal models. Earlier studies suggest that these effects involve facilitation of serotonin, a neurotransmitter that has also been related to obsessive-compulsive disorder. On the basis of this evidence, this study investigated the effects of CBD in C57BL/6J mice submitted to the marble-burying test (MBT), an animal model proposed to reflect compulsive behaviour. CBD (15, 30 and 60 mg/kg) induced a significant decrease in the number of buried marbles compared with controls (34, 41 and 48%, respectively). A similar, although larger, decrease was also found after the serotonin selective reuptake inhibitor paroxetine (10 mg/kg, 77% decrease) and the benzodiazepine diazepam (2.5 mg/kg, 84% decrease). The effect of CBD (30 mg/kg) was still significant after 7 days of daily repeated administration, whereas the effect of diazepam disappeared. Pretreatment with WAY100635 (3 mg/kg), a 5HT1A receptor antagonist, prevented the effects of paroxetine but failed to alter those of CBD. These latter effects, however, were prevented by pretreatment with the CB1 receptor antagonist AM251 (1 mg/kg). These results indicated that CBD and paroxetine decrease the number of buried marbles in the MBT through distinct pharmacological mechanisms. They also suggest a potential role of drugs acting on the cannabinoid system in modulating compulsive behaviour. Behavioural Pharmacology 21: 353-358 (C) 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins.

Involvement of the lateral septal area in the expression of fear conditioning to context

Considering the evidence that the lateral septal area (LSA) modulates defensive responses, the aim of the present study is to verify if this structure is also involved in contextual fear conditioning responses. Neurotransmission in the LSA was reversibly inhibited by bilateral microinjections of cobalt chloride (CoCl(2), 1 mM) 10 min before or after conditioning or 10 min before re-exposure to the aversively conditioned chamber. Only those animals that received CoCl(2) before re-exposure showed a decrease in both cardiovascular and behavioral conditioned responses. These results suggest that the LSA participates in the expression, but not acquisition or consolidation, of contextual fear conditioning.

Involvement of the prelimbic prefrontal cortex on cannabidiol-induced attenuation of contextual conditioned fear in rats

Rationale: Systemic administration of cannabidiol (CBD), a non-psychotomimetic component of Cannabis sativa, is able to attenuate cardiovascular and behavioral (freezing) changes induced by re-exposure to a context that had been previously paired with footshocks. The brain sites mediating this effect, however, remain unknown. The medial prefrontal cortex (mPFC) has been related to contextual fear conditioning. Objectives: (1) To verify, using c-Fos immunocytochemistry, if the mPFC is involved in the attenuation of contextual fear induced by systemic administration of CBD; (2) to investigate if direct microinjections of CBD into mPFC regions would also attenuate contextual fear. Results: Confirming previous results systemic administration of CBD (10 mg/kg) decreased contextual fear and associated c-Fos expression in the prefrontal cortex (prelimbic and infralimbic regions). The drug also attenuated c-Fos expression in the bed nucleus of the stria terminalis (BNST). Direct CBD (30 nmol) microinjection into the PL prefrontal cortex reduced freezing induced by re-exposure to the aversively conditioned context. In the infralimbic (IL) prefrontal cortex, however, CBD (30 nmol) produced an opposite result, increasing the expression of contextual fear conditioning. This result was confirmed by an additional experiment where the conditioning session was performed under a less aversive protocol. Conclusion: These results suggest that the PL prefrontal cortex may be involved in the attenuation of contextual fear induced by systemic injection of CBD. They also support the proposition that the IL and PL play opposite roles in fear conditioning. A possible involvement of the BNST in CBD effects needs to be further investigated. (C) 2009 Elsevier B.V. All rights reserved.

Effect of acute restraint stress on the tachycardiac and bradycardiac responses of the baroreflex in rats

In the present study, we evaluated cardiac baroreflex responses of rats submitted to acute restraint stress. The baroreflex was tested: immediately before, during a 30 min exposure to restraint stress, as well as 30 and 60 min after ending the stress session (recovery period). Restraint increased both mean arterial pressure (MAP) and heart rate (HR). The magnitude of tachycardiac responses evoked by intravenous infusion of sodium nitroprusside was higher during restraint stress, whereas that of bradycardiac responses evoked by intravenous infusion of phenylephrine was decreased. Restraint-evoked baroreflex changes were still observed at 30 min into the recovery period, although MAP and HR values had already returned to control values. The baroreflex was back to control values at 60 min of the recovery period. Intravenous administration of the selective beta(1)-adrenoceptor antagonist atenolol blocked the restraint-evoked increase in the tachycardiac baroreflex response, but did not affect the effects on the bradycardiac response. In conclusion, the present results suggest that psychological stresses, such as those resulting from acute restraint, affect the baroreflex. Restraint facilitated the tachycardiac baroreflex response and reduced the bradycardiac response. Restraint-related effects on baroreflex persisted for at least 30 min after ending restraint, although MAP and HR had already returned to control levels. The cardiac baroreflex returned to control values 60 min after the end of restraint, indicating non-persistent effects of acute restraint on the baroreflex. Results also indicate that the influence of restraint stress on the baroreflex tachycardiac response is mainly dependent on cardiac sympathetic activity, whereas the action on the bradycardiac response is mediated by the cardiac parasympathetic component.

ACTIVATION OF PERIPHERAL kappa/delta OPIOID RECEPTORS MEDIATES 15-DEOXY-(Delta 12,14)-PROSTAGLANDIN J(2) INDUCED-ANTINOCICEPTION IN RAT TEMPOROMANDIBULAR JOINT

This study assessed the effect of the agonist 15d-PGJ(2) administered into the rat temporomandibular joint (TMJ) on nociceptive behavioral and the anti-inflammatory potential of this prostaglandin on TMJ. It was observed that 15-deoxy-(Delta 12,14)-prostaglandin J(2) (15d-PGJ(2)) significantly reduced formalin-induced nociceptive behavior in a dose dependent manner, however injection of 15d-PGJ(2) into the contralateral TMJ failed to reduce such effects. This antinociceptive effect is dependent on peroxisome proliferator-activated receptors-gamma (PPAR-gamma) since pre-treatment with GW9662 (PPAR-gamma receptor antagonist) blocked the antinociceptive effect of 15d-PGJ(2) in the TMJ. In addition, the antinociceptive effect of 15d-PGJ(2) was also blocked by naloxone suggesting the involvement of peripheral opioids in the process. Confirming this hypothesis pre-treatment with kappa, delta, but not mu receptor antagonists significantly reduced the antinociceptive effect of 15d-PGJ(2) in the TMJ. Similarly to opioid agonists, the 15d-PGJ(2) antinociceptive action depends on the nitric oxide (NO)/guanilate cyclase (cGMP)/ATP-sensitive potassium channel blocker(K(ATP)(+)) channel pathway since it was prevented by the pre-treatment with the inhibitors of nitric oxide synthase (NOS; aminoguanidine), cGMP (ODQ), or the K(ATP)(+) (glibenclamide). In addition, 15d-PGJ(2) (100 ng/TMJ) inhibits 5-HT-induced TMJ hypernociception. Besides, TMJ treated with 15d-PGJ(2) showed lower vascular permeability, assessed by Evan`s Blue extravasation, and also lower neutrophil migration induced by carrageenan administration. Taken together, these results demonstrate that 15d-PGJ(2) has a potential peripheral antinociceptive and anti-inflammatory effect in the TMJ via PPAR-gamma activation. The results also suggest that 15d-PGJ(2) induced-peripheral antinociceptive response in the TMJ is mediated by kappa/delta opioid receptors by the activation of the intracellular L-arginine/NO/cGMP/K(ATP)(+) channel pathway. The pharmacological properties of the peripheral administration of 15d-PGJ(2) highlight the potential use of this PPAR-gamma agonist on TMJ inflammatory pain conditions. (C) 2009 IBRO. Published by Elsevier Ltd. All rights reserved.

Comparative neuroanatomical and temporal characterization of FluoroJade-positive neurodegeneration after status epilepticus induced by systemic and intrahippocampal pilocarpine in Wistar rats

The aims of this study were to characterize the spatial distribution of neurodegeneration after status epilepticus (SE) induced by either systemic (S) or intrahippocampal (H) injection of pilocarpine (PILO), two models of temporal lobe epilepsy (TLE), using FluoroJade (FJ) histochemistry, and to evaluate the kinetics of FJ staining in the H-PILO model. Therefore, we measured the severity of behavioral seizures during both types of SE and also evaluated the FJ staining pattern at 12, 24, and 168 h (7 days) after the H-PILO insult. We found that the amount of FJ-positive (FJ+) area was greater in SE induced by S-PILO as compared to SE induced by H-PILO. After SE induced by H-PILO, we found more FJ+ cells in the hilus of the dentate gyrus (DG) at 12 h, in CA3 at 24 h, and in CA1 at 168 h. We found also no correlation between seizure severity and the number of FJ+ cells in the hippocampus. Co-localization studies of FJ+ cells with either neuronal-specific nuclear protein (NeuN) or glial fibrillary acidic protein (GFAP) labeling 24 h after H-PILO demonstrated spatially selective neurodegeneration. Double labeling with FJ and parvalbumin (PV) showed both FJ+/PV+ and FJ+/PV- cells in hippocampus and entorhinal cortex, among other areas. The current data indicate that FJ+ areas are differentially distributed in the two TLE models and that these areas are greater in the S-PILO than in the H-PILO model. There is also a selective kinetics of FJ+ cells in the hippocampus after SE induced by H-PILO, with no association with the severity of seizures, probably as a consequence of the extra-hippocampal damage. These data point to SE induced by H-PILO as a low-mortality model of TLE, with regional spatial and temporal patterns of FJ staining. (C) 2010 Elsevier B.V. All rights reserved.

Study of spontaneous recurrent seizures and morphological alterations after status epilepticus induced by intrahippocampal injection of pilocarpine

Epileptic seizures are clinical manifestations of neuronal discharges characterized by hyperexcitability and/or hypersynchrony in the cortex and other subcortical regions. The pilocarpine (PILO) model of epilepsy mimics temporal lobe epilepsy (TLE) in humans. In the present study, we used a more selective approach: microinjection of PILO into the hilus of the dentate gyrus (H-PILO). Our main goal was to evaluate the behavioral and morphological alterations present in this model of TLE. Seventy-six percent of all animals receiving H-PILO injections had continuous seizures called status epilepticus (SE). A typical pattern of evolution of limbic seizures during the SE with a latency of 29.3 +/- 16.3 minutes was observed using an analysis of behavioral sequences. During the subsequent 30 days, 71% of all animals exhibited spontaneous recurrent seizures (SRSs) during a daily 8-hour videotaping session. These SRSs had a very conspicuous and characteristic pattern detected by behavioral sequences or neuroethological analysis. Only the animals that had SE showed positive Neo-Timm staining in the inner molecular layer of the dentate gyrus (sprouting) and reduced cell density in Ammon`s horn pyramidal cell subfield CA1. However, no correlation between the intensity of sprouting and the mean number and total number of SRSs was found. Additionally, using Fluoro-Jade staining, we observed neurodegeration in the hilus and pyramidal cell subfields CA3 and CM 24 hours after SE. These data indicate that H-PILO is a reliable, selective, efficient, low-mortality model that mimics the acute and chronic behavioral and morphological aspects of TLE. (C) 2010 Elsevier Inc. All rights reserved.

Corticotrophin-releasing factor mediates hypophagia after adrenalectomy, increasing meal-related satiety responses

Adrenalectomy-induced hypophagia is associated with increased satiety-related responses, which involve neuronal activation of the nucleus of the solitary tract (NTS). Besides its effects on the pituitary-adrenal axis, corticotrophin-releasing factor (CRF) has been shown to play an important role in feeding behaviour, as it possesses anorexigenic effects. We evaluated feeding-induced CRF mRNA expression in the paraventricular nucleus (PVN) and the effects of pretreatment with CRF(2) receptor antagonist (Antisauvagine-30, AS30) on food intake and activation of NTS neurons in response to feeding in adrenalectomised (ADX) rats. Compared to the sham group, ADX increased CRF mRNA levels in the PVN of fasted animals, which was further augmented by refeeding. AS30 treatment did not affect food intake in the sham and ADX + corticosterone (B) groups; however, it reversed hypophagia in the ADX group. In vehicle-pretreated animals, refeeding increased the number of Fos and Fos/TH-immunoreactive neurons in the NTS in the sham, ADX and ADX + B groups, with the highest number of neurons in the ADX animals. Similarly to its effect on food intake, pretreatment with AS30 in the ADX group also reversed the increased activation of NTS neurons induced by refeeding while having no effect in the sham and ADX + B animals. The present results show that adrenalectomy induces an increase in CRF mRNA expression in the PVN potentiated by feeding and that CRF(2) receptor antagonist abolishes the anorexigenic effect and the increased activation of NTS induced by feeding in the ADX animals. These data indicate that increased activity of PVN CRF neurons modulates brainstem satiety-related responses, contributing to hypophagia after adrenalectomy. (C) 2010 Elsevier Inc. All rights reserved.

A combined study of behavior and Fos expression in limbic structures after re-testing Wistar rats in the elevated plus-maze

The elevated plus-maze is an animal model used to study anxiety. In a second session, rats show a reduction in the exploratory behavior even when the two sessions are separated by intervals as large as 7 days. The aim of the present study was to investigate whether the reduction in the exploratory behavior is maintained after intervals larger than 7 days. Additionally, we aimed at investigating eventual correlations between behaviors in the plus-maze and activation of limbic structures as measured by Fos protein expression after the second session. Rats were tested for 5 min in the elevated plus-maze and re-tested 3, 9 or 33 days later. Other groups were tested only once. The rat brains were processed for immunohistochemical detection of Fos protein. The results show a decrease in the open arms exploration in the second trial with intervals of 3, 9 and 33 days. The expression of Fos protein in the piriform cortex, septal nucleus and paraventricular hypothalamic nucleus in the groups tested with intervals of 9 and 33 days were statistically different from the other groups. The alterations observed in exploratory behavior in the second session in the plus-maze did not correlate with Fos expression. In conclusion, although the specific test conditions were sufficient to evoke behavioral alterations in exploration in the elevated plus-maze, they were enough to induce significant Fos protein expression in piriform cortex, septal nucleus and thalamic and hypothalamic paraventricular nuclei but not in other areas such as dorsomedial nucleus of the hypothalamus and amygdala nuclei, known to be also active participants in circuits controlling fear and anxiety. (C) 2010 Elsevier Inc. All rights reserved.

Role of homocysteic acid in the guinea pig (Cavia porcellus) anterior cingulate cortex in tonic immobility and the influence of NMDA receptors on the dorsal PAG

Tonic immobility (TI) is an innate defensive behaviour elicited by physical restriction and Postural inversion, and is characterised by a profound and temporary state of akinesis. Our previous studies demonstrated that glutamatergic stimulation of the dorsomedial/dorsolateral Portion of periaqueductal gray matter (dPAG) decreases the duration of TI in guinea pigs (Cavia porcellus). Furthermore, evidence suggests that the anterior cingulate cortex (ACC) constitutes an important Source of glutamate for the dPAG. Hence, in the current study, we investigated the effects of microinjection of the excitatory amino acid (EAA) agonist DL-homocysteic acid (DLH) and the N-methyl-D-aspartate (NMDA) receptor antagonist MK-801 into the ACC on the duration of TI in guinea pigs. We also assessed the effect of the NMDA receptor antagonist (MK-801) into the dorsal periaqueductal gray matter (dPAG) prior to DLH microinjection into the ACC on the TI duration in the guinea pig. Our results demonstrated that DLH microinjections into the ACC decreased the duration of TI. This effect was blocked by previous MK-801 microinjections into the ACC or into the dPAG. The MK-801 microinjections alone did not influence TI duration. These results provide the new insight that EAAs in the ACC can decrease the duration of TI. The mechanism seems to be dependent on the NMDA receptors present in the ACC and in the dPAG. (C) 2009 Elsevier B.V. All rights reserved.

Ontogenetic role of angiontensin-converting enzyme in rats: Thirst and sodium appetite evaluation

We investigated the influence of captopril (an angiotensin converting enzyme inhibitor) treatment during pregnancy and lactation period on hydromineral balance of the male adult offspring, particularly, concerning thirst and sodium appetite. We did not observe significant alterations in basal hydromineral (water intake, 0.3 M NaCl intake, volume and sodium urinary concentration) or cardiovascular parameters in adult male rats perinatally treated with captopril compared to controls. However, male offspring rats that perinatally exposed to captopril showed a significant attenuation in water intake induced by osmotic stimulation, extracellular dehydration and beta-adrenergic stimulation. Moreover, captopril treatment during perinatal period decreased the salt appetite induced by sodium depletion. This treatment also attenuated thirst and sodium appetite aroused during inhibition of peripheral angiotensin 11 generation raised by low concentration of captopril in the adult offspring. Interestingly. perinatal exposure to captopril did not alter water or salt intake induced by i.c.v. administration of angiotensin I or angiotensin II. These results showed that chronic inhibition of angiotensin converting enzyme during pregnancy and lactation modifies the regulation of induced thirst and sodium appetite in adulthood. (C) 2009 Elsevier Inc. All rights reserved.