Antinociceptive and antiedema effects produced in rats by Brassica oleracea var. italica sprouts involving sulforaphane.

Natural products are recognized as potential analgesics since many of them are part of modern medicine to relieve pain without serious adverse effects. The aim of this study was to investigate the antinociceptive and anti-inflammatory activities of an aqueous extract of Brassica oleracea var. italica sprouts (AEBS) and one of its main reported bioactive metabolites sulforaphane (SFN). Antinociceptive activity of the AEBS (30, 100, and 300 mg/kg, i.p. or 1000 and 2000 mg/kg, p.o.) and SFN (0.1 mg/kg, i.p.) was evaluated in the plantar test in rats to reinforce its analgesic-like activity at central level using the reference drug tramadol (TR, 50 mg/kg, i.p.). The anti-inflammatory-like response was determined in the carrageenan-induced oedema at the same dosages for comparison with ketorolac (KET, 20 mg/kg, i.p.) or indomethacin (INDO, 20 mg/kg, p.o.). A histological analysis of the swollen paw was included to complement the anti-inflammatory response. Additionally, acute toxicity observed in clinical analgesics as the most common adverse effects, such as sedation and/or gastric damage, was also explored. As a result, central and peripheral action of the AEBS was confirmed using enteral and parenteral administration, in which significant reduction of the nociceptive and inflammatory responses resembled the effects of TR, KET, or INDO, respectively, involving the presence of SFN. No adverse or toxic effects were observed in the presence of the AEBS or SFN. In conclusion, this study supports that Brassica oleracea var. italica sprouts are a potential source of antinociceptive natural products such as SFN for therapy of pain alone and associated to an inflammation condition.

Antinociceptive effects of maqui-berry (Aristotelia chilensis (Mol.) Stuntz).

Maqui-berry is characterised by presenting a high concentration of (poly)phenols, accounting anthocyanins (cyanidin and delphinidin) for over 85% of the total. These coloured flavonoids have demonstrated potential neurological activity, but the evidence of their antinociceptive properties is scarce. In order to cover this gap, different doses (suitable for human administration) of a maqui-berry powder (1.6% anthocyanin), using enteral and parenteral routes of administration, were compared at central and peripheral levels using a nociceptive pain model (formalin test) in mice. Gastric damage analysis as possible adverse effects of analgesic and anti-inflammatory drugs was also explored. Dose-antinociceptive response was confirmed using both routes of administration and in both neurogenic and inflammatory phases of the formalin test, without gastric damage. In conclusion, these preliminary data provide evidence of pharmacological properties of maqui-berry to alleviate nociceptive pain.

Lamiaceae in Mexican Species, a Great but Scarcely Explored Source of Secondary Metabolites with Potential Pharmacological Effects in Pain Relief.

The search for molecules that contribute to the relief of pain is a field of research in constant development. Lamiaceae is one of the most recognized families world-wide for its use in traditional medicine to treat diseases that include pain and inflammation. Mexico can be considered one of the most important centers of diversification, and due to the high endemism of this family, it is crucial for the in situ conservation of this family. Information about the most common genera and species found in this country and their uses in folk medicine are scarcely reported in the literature. After an extensive inspection in bibliographic databases, mainly Sciencedirect, Pubmed and Springer, almost 1200 articles describing aspects of Lamiaceae were found; however, 217 articles were selected because they recognize the Mexican genera and species with antinociceptive and/or anti-inflammatory potential to relieve pain, such as Salvia and Agastache. The bioactive constituents of these genera were mainly terpenes (volatile and non-volatile) and phenolic compounds such as flavonoids (glycosides and aglycone). The aim of this review is to analyze important aspects of Mexican genera of Lamiaceae, scarcely explored as a potential source of secondary metabolites responsible for the analgesic and anti-inflammatory properties of these species. In addition, we point out the possible mechanisms of action involved and the modulatory pathways investigated in different experimental models. As a result of this review, it is important to mention that scarce information has been reported regarding species of this family from Mexican genera. In fact, despite Calosphace being one of the largest subgenera of Salvia in the world, found mainly in Mexico, it has been barely investigated regarding its potential biological activities and recognized bioactive constituents. The scientific evidence regarding the different bioactive constituents found in species of Lamiaceae demonstrates that several species require further investigation in preclinical studies, and of course also in controlled clinical trials evaluating the efficacy and safety of these natural products to support their therapeutic potential in pain relief and/or inflammation, among other health conditions. Since Mexico is one of the most important centers of diversification, and due to the high endemism of species of this family, it is crucial their rescue, in situ conservation, and investigation of their health benefits.

Perinatal exposure to organohalogen pollutants decreases vasopressin content and its mRNA expression in magnocellular neuroendocrine cells activated by osmotic stress in adult rats.

Polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) are environmental pollutants that produce neurotoxicity and neuroendocrine disruption. They affect the vasopressinergic system but their disruptive mechanisms are not well understood. Our group reported that rats perinatally exposed to Aroclor-1254 (A1254) and DE-71 (commercial mixtures of PCBs and PBDEs) decrease somatodendritic vasopressin (AVP) release while increasing plasma AVP responses to osmotic activation, potentially emptying AVP reserves required for body-water balance. The aim of this research was to evaluate the effects of perinatal exposure to A1254 or DE-71 (30mgkg/day) on AVP transcription and protein content in the paraventricular and supraoptic hypothalamic nuclei, of male and female rats, by in situ hybridization and immunohistochemistry. cFOS mRNA expression was evaluated in order to determine neuroendocrine cells activation due to osmotic stimulation. Animal groups were: vehicle (control); exposed to either A1254 or DE-71; both, control and exposed, subjected to osmotic challenge. The results confirmed a physiological increase in AVP-immunoreactivity (AVP-IR) and gene expression in response to osmotic challenge as reported elsewhere. In contrast, the exposed groups did not show this response to osmotic activation, they showed significant reduction in AVP-IR neurons, and AVP mRNA expression as compared to the hyperosmotic controls. cFOS mRNA expression increased in A1254 dehydrated groups, suggesting that the AVP-IR decrease was not due to a lack of the response to the osmotic activation. Therefore, A1254 may interfere with the activation of AVP mRNA transcript levels and protein, causing a central dysfunction of vasopressinergic system.

Depressant Effects of Salvia divinorum Involve Disruption of Physiological Sleep.

Although Salvia divinorum is traditionally known as a 'mind-altering' or psychoactive herb used, among others things, as a tranquilizer, this property has not been validated with regard to its efficacy and safety. The objective of this study is to provide evidence for the sedative effects of S. divinorum and discriminate the nature of the responsible constituents by examining different experimental models. A battery of tests, including the open-field, hole-board, exploration cylinder, plus-maze and sodium pentobarbital-induced hypnosis potentiation, were used in mice after administration of non-polar, medium polar and/or polar extracts of the plant (10, 30 and 100 mg/kg). Polysomnographic analysis in rats receiving an active medium polar extract (10 and 100 mg/kg) containing salvinorins was also assessed to study the effects of this plant on sleep architecture. All tested extracts produced significant sedative-like responses, although those of the medium polar extract were more pronounced in mice. The sedative effect of this latter extract, which contains a mixture of salvinorins, caused fragmented sleep architecture in rats by diminishing rapid eye movement (REM) sleep and increased the quiet awake stage at 10 and 100 mg/kg. Our results provide evidence that S. divinorum exhibits sedative-like depressant properties that alter physiological sleep architecture. Copyright © 2016 John Wiley & Sons, Ltd.

Antinociceptive and anti-inflammatory activities of a pomegranate (Punica granatum L.) extract rich in ellagitannins.

Pomegranate (Punica granatum L.) has been used for centuries for the treatment of inflammatory diseases. However, there is a lack of comprehensive information focused on the properties of a certain pomegranate (poly)phenolic profile to cure pain and gastric injury induced by anti-inflammatory drugs. This study investigated the systemic effects of different doses of a HPLC-characterized pomegranate extract on the formalin-induced nociceptive behavior in mice. The effect of the extract against gastric injury caused by non-steroidal anti-inflammatory drugs and ethanol was also assessed. Pomegranate reduced nociception in both phases of the formalin test, suggesting central and peripheral activities to inhibit nociception. Indomethacin-induced gastric injury was not produced in the presence of pomegranate, which also protected against ethanol-induced gastric lesions. The present results reinforce the benefits of pomegranate (poly)phenolics in the treatment of pain as well as their anti-inflammatory properties.

Isobolographic analysis of the antinociceptive interaction between ursolic acid and diclofenac or tramadol in mice.

It is considered that natural products used in folk medicine can potentiate the effect of drugs. The aim of this study was to evaluate the pharmacological interaction between ursolic acid, a triterpene isolated from herbal medicines to treat pain, and the analgesics diclofenac or tramadol. Individual dose-response curves of the antinociceptive effect of these compounds were built to calculate the ED50, as well as the pharmacological interaction, by using isobolographic analysis. All treatments decreased significantly and in a dose-dependent manner the writhing behavior with ED50 values of 103.50 ± 19.66, 20.54 ± 6.05, and 9.60 ± 1.69 mg/kg, for ursolic acid, diclofenac, and tramadol, respectively. An isobolographic analysis allowed the characterization of the pharmacological interaction produced by a fixed ratio combination of 1 : 1 and 1 : 3 of equi-effective doses of these compounds. Theoretical antinociceptive ED50 values of ursolic acid-diclofenac were 62.12 ± 10.28 and 41.43 ± 6.69 mg/kg, respectively, not statistically different from those obtained experimentally (44.52 ± 5.25 and 44.89 ± 49.05 mg/kg, respectively), reporting an additive interaction. Theoretical antinociceptive ED50 values of ursolic acid-tramadol (56.56 ± 9.87 and 33.08 ± 5.07 mg/kg, respectively) were significantly lower than those observed experimentally (138.36 ± 49.05 and 67.34 ± 18.98 mg/kg, respectively) reporting antagonism in this interaction. Antinociceptive response obtained from isobolograms in the writhing test was corroborated by using formalin test in mice. Adverse effects such as gastric damage in the ursolic acid-diclofenac combination did not increase in an additive form similarly as with antinociception. Conversely, sedative response was significantly increased in the ursolic acid-tramadol combination. As observed in the formalin test, the antagonism on the antinociceptive response between ursolic acid and tramadol (1 : 1) was not reverted in the presence of the opioid antagonist naltrexone (1 mg/kg, i. p.). These results provide evidence for a differential pharmacological interaction, in which ursolic acid does not interfere with the antinociceptive effect of diclofenac but antagonizes that obtained with tramadol in an independent opioid mechanism. Therefore, medicinal plants containing abundant presence of ursolic acid may also modify efficacy in the alternative combinations for the pain therapy.

Preparations for colon capsule endoscopy. Prospective and randomized comparative study between two preparations for colon capsule endoscopy: PEG 2 liters + ascorbic acid versus PEG 4 liters.

INTRODUCTION: PillCam© colon capsule endoscopy (CCE) enables the study of colonic diseases in a safe and non-invasive way, although there are aspects that need to be improved. Current methods of bowel preparation lead to discordant rates of adequate cleansing and CCE excretion. AIMS: To compare the efficacy of colon cleansing using two different regimes (2L PEG plus ascorbic acid versus 4L PEG alone) for PillCam Colon (C2) capsule endoscopy. METHODS: Fifty eight patients included in this prospective study and randomized to: Group A, PEG plus ascorbic acid regimen (n = 28, 12 F/16 M) or group B, PEG alone regimen (n = 30, 14 F/16 M). The degree of cleansing was categorized into "excellent-good" or "fair-poor", according to Leighton´s recently published preparation scale. CCE excretion rate and colon cleansing were assessed. Patients underwent to PillCam colon of second generation (C2). RESULTS: Cleansing was considered to be excellent-good in 78 % of cases in group A and in 64 % of cases in group B, with no significant difference between the groups (p = 0.252). Nevertheless, when the grade of cleansing was analyzed in segments, a significant difference was found in the cecum and transverse colon. No differences were observed in the bubble effect between preparations. The excretion rate was 93 % in group A versus 70 % in group B (p = 0.043). CONCLUSIONS: These results suggest that a 2L PEG plus ascorbic acid regimen is at least as effective as a 4L PEG regimen. This regimen may be considered an effective alternative which would improve compliance because a smaller volume is required.

Antinociceptive effects of Raphanus sativus sprouts involve the opioid and 5-HT1A serotonin receptors, cAMP/cGMP pathways, and the central activity of sulforaphane.

Raphanus sativus L. cv. Sango, commonly known as red radish, is widely consumed around the world as a vegetable, but its benefit in pain relief is not sufficiently investigated. This study aimed to evaluate the antinociceptive effects of R. sativus and a possible mechanism of action. An aqueous extract of R. sativus sprouts (AERSS) was investigated by parenteral (10, 30, and 100 mg kg-1, i.p.) and enteral (500 mg kg-1, p.o.) administration in the neurogenic and inflammatory phases of the formalin test, where gastric damage was also evaluated as a possible adverse effect. Ketorolac (5 mg kg-1, i.p.) was used as the reference drug. Endogenous opioid and 5-HT1A serotonin receptors, as well as the cAMP/NO-cGMP pathways, were explored in the study of a possible mechanism of action by using their corresponding antagonists: naloxone, 1 mg kg-1, i.p., WAY100635, 1 mg kg-1, i.p., and enzymatic activators or inhibitors, respectively. Sulforaphane (SFN), a known bioactive metabolite, was analyzed using electroencephalography (EEG) to evidence its central involvement. A significant and dose-dependent antinociceptive activity was observed with the AERSS resembling the antinociceptive effect of the reference drug, with an equivalent significant response with a dose of 500 mg kg-1, p.o. without causing gastric damage. The participation of the endogenous opioid and 5-HT1A serotonin receptors at central and peripheral levels was also observed, with a differential participation of cAMP/NO-cGMP. SFN as one metabolite produced significant changes in the EEG analysis, reinforcing its effects on the CNS. Our preclinical evidence supports the benefits of consuming Raphanus sativus cv. Sango sprouts for pain relief.

Spasmolytic and antinociceptive activities of ursolic acid and acacetin identified in Agastache mexicana.

Agastache mexicana is a plant in high demand that has long been used in Mexican folk medicine to treat anxiety, insomnia, and stomachache, among other afflictions. Ursolic acid and acacetin were isolated and identified as two possible active compounds of A. mexicana aerial parts. An antinociceptive response was demonstrated in a significant and dose-dependent manner with ursolic acid and acacetin (i. p. and p. o.) in comparison to the analgesic diclofenac by using the writhing test in mice. Moreover, acacetin also produced a significant concentration-dependent spasmolytic response with major efficacy compared to ursolic acid and papaverine by using rings from the isolated guinea pig ileum. These results provide evidence of the presence of two active constituents of Agastache mexicana reinforcing its utility as a therapy for visceral pain as used in traditional medicine.

The nucleus accumbens dopamine increase, typically triggered by sexual stimuli in male rats, is no longer produced when animals are sexually inhibited due to sexual satiety.

RATIONALE: Exposure of male rats to an inaccessible receptive female and copulation increases dopamine (DA) levels in the nucleus accumbens (NAcc). Males copulating to satiety become sexually inhibited and most of them do not display sexual activity when presented with a sexually receptive female 24 h later. This inhibitory state can be pharmacologically reversed. There are no studies exploring NAcc DA levels during this sexual inhibitory state. OBJECTIVES: To characterize changes in NAcc DA and its metabolites' levels during sexual satiety development, during the well-established sexual inhibitory state 24 h later, and during its pharmacological reversal. METHODS: Changes in NAcc DA and its metabolites were measured in sexually experienced male rats, using in vivo microdialysis, during copulation to satiety, when presented to a new sexually receptive female 24 h later, and during the pharmacological reversal of the sexual inhibition by anandamide. RESULTS: NAcc DA levels remained increased during copulation to satiety. DA basal levels were significantly reduced 24 h after copulation to satiety, as compared to the initial basal levels. Presenting a receptive female behind a barrier 24 h after satiety did not induce the typical NAcc DA elevation in the sexually satiated males but there was a decrease that persisted when they got access to the female, with which they did not copulate. Anandamide injection slightly increased NAcc DA levels coinciding with sexual satiety reversal. CONCLUSIONS: Reduced NAcc DA concentrations coincide with the inhibition of an instinctive, natural rewarding behavior suggesting that there might be a DA concentration threshold needed to be responsive to a rewarding stimulus.

Pharmacological Interaction of Quercetin Derivatives of Tilia americana and Clinical Drugs in Experimental Fibromyalgia.

Fibromyalgia (FM) is a pain syndrome characterized by chronic widespread pain and CNS comorbidities. Tilia americana var. mexicana is a medicinal species used to treat anxiety, insomnia, and acute or chronic pain. However, its spectrum of analgesic efficacy for dysfunctional pain is unknown. To investigate a possible therapeutic alternative for FM-type pain, an aqueous Tilia extract (TE) and its flavonoid fraction (FF) containing rutin and isoquercitrin were evaluated alone and/or combined with clinical drugs (tramadol-TRA and pramipexol-PRA) using the reserpine-induced FM model in rats. Chromatographic analysis allowed the characterization of flavonoids, while a histological analysis confirmed their presence in the brain. TE (10-100 mg/kg, i.p.) and FF (10-300 mg/kg, i.p.) produced significant and dose-dependent antihyperalgesic and antiallodynic effects equivalent to TRA (3-10 mg/kg, i.p.) or PRA (0.01-1 mg/kg, s.c.). Nevertheless, the combination of FF + TRA or FF + PRA resulted in an antagonistic interaction by possible competitive action on the serotonin transporter or µ-opioid and D2 receptors, respectively, according to the in silico analysis. Flavonoids were identified in cerebral regions because of their self-epifluorescence. In conclusion, Tilia possesses potential properties to relieve FM-type pain. However, the consumption of this plant or flavonoids such as quercetin derivatives in combination with analgesic drugs might reduce their individual benefits.

Antihyperalgesic and Antiallodynic Effects of Amarisolide A and Salvia amarissima Ortega in Experimental Fibromyalgia-Type Pain.

Salvia amarissima Ortega is an endemic species of Mexico used in folk medicine to alleviate pain and as a nervous tranquilizer. The S. amarissima extract and one of its abundant metabolites, identified and isolated through chromatographic techniques, were investigated to obtain scientific evidence of its potential effects to relieve nociplastic pain such as fibromyalgia. Then, the extract and amarisolide A (3-300 mg/kg, i.p.) were pharmacologically evaluated in reserpine-induced fibromyalgia-type chronic pain and in depressive-like behavior (as a common comorbidity) by using the forced swimming test in rats. The 5-HT1A serotonin receptor (selective antagonist WAY100635, 1 mg/kg, i.p.) was explored after the prediction of a chemical interaction using in silico analysis to look for a possible mechanism of action of amarisolide A. Both the extract and amarisolide A produced significant and dose-dependent antihyperalgesic and antiallodynic effects in rats, as well as significant antidepressive behavior without sedative effects when the antinociceptive dosages were used. The 5-HT1A serotonin receptor participation was predicted by the in silico descriptors and was corroborated in the presence of WAY100635. In conclusion, S. amarissima possesses antihyperalgesic, antiallodynic, and anti-depressive activities, partially due to the presence of amarisolide A, which involves the 5-HT1A serotonin receptor. This pharmacological evidence suggests that S. amarissima and amarisolide A are both potential alternatives to relieve pain-like fibromyalgia.

Tracking the Temporal Footprint Effect of Thermonociception and Denervation on the Brain's Pain Matrix: fMRI and BOLD Study in Rats.

Objective: Pain constitutes an essential alarm for preserving the organism's integrity. Damage to the nervous system produces a pathological condition known as neuropathic pain. Purpose: Blood oxygenation level-dependent (BOLD) and functional magnetic resonance imaging (fMRI) have been widely used to map neuroanatomy and the active regions of interest (ROI) of nociceptive processing. Our study explored the brain's BOLD response in rats after thermal noxious stimulation, immediately after sciatic nerve damage and during 75 minutes after surgical lesion of the sciatic nerve. Methods: Nine male Wistar rats were tested; the experiments were performed on a 7-Tesla /21-cm Varian Agilent system. This approach allowed, for the first time, to measure in vivo the BOLD changes in brain regions involved with the pain process: cingulated (ACC), somatosensory (S1), and insular cortices (IC), as well as thalamus (Th) and ventral tegmental area (VTA) related with acute thermal pain and during the early stages of sciatic denervation that produce neuropathic pain. Results: During thermonociception scan, all subjects showed BOLD activation in the ROIs determined as ACC, S1, Th, IC and VTA. After denervation, these regions continued to show activation with a slow decrement in intensity for the duration of the experiment. The results suggest that these brain structures are overactive during the genesis of neuropathic pain. Conclusion: The study shows for the first time continuous activation of the pain matrix following an acute thermal nociceptive stimulus followed by neuropathic damage. These results have given insight into the early stages of the development of neuropathic pain in vivo.

Expression of the dopaminergic D1 and D2 receptors in the anterior cingulate cortex in a model of neuropathic pain.

BACKGROUND: The anterior cingulate cortex (ACC) has been related to the affective component of pain. Dopaminergic mesocortical circuits, including the ACC, are able to inhibit neuropathic nociception measured as autotomy behaviour. We determined the changes in dopamine D1 and D2 (D1R and D2R) receptor expression in the ACC (cg1 and cg2) in an animal model of neuropathic pain. The neuropathic group had noxious heat applied in the right hind paw followed 30 min. later by right sciatic denervation. Autotomy score (AS) was recorded for eight days and subsequently classified in low, medium and high AS groups. The control consisted of naïve animals.A semiquantitative RT-PCR procedure was done to determine mRNA levels for D1R and D2R in cg1 and cg2, and protein levels were measured by Western Blot. RESULTS: The results of D1R mRNA in cg1 showed a decrease in all groups. D2R mRNA levels in cg1 decreased in low AS and increased in medium and high AS. Regarding D1R in cg2, there was an increase in all groups. D2R expression levels in cg2 decreased in all groups. In cg1, the D2R mRNA correlated positively with autotomy behaviour. Protein levels of D2R in cg1 increased in all groups but to a higher degree in low AS. In cg2 D2R protein only decreased discretely. D1R protein was not found in either ACC region. CONCLUSIONS: This is the first evidence of an increase of inhibitory dopaminergic receptor (D2R) mRNA and protein in cg1 in correlation with nociceptive behaviour in a neuropathic model of pain in the rat.

Properties and Differential Expression of H+ Receptors in Dorsal Root Ganglia: Is a Labeled-Line Coding for Acid Nociception Possible?

Pain by chemical irritants is one of the less well-described aspects of nociception. The acidic substance is the paradigm of the chemical noxious compound. An acidic insult on cutaneous, subcutaneous and muscle tissue results in pain sensation. Acid (or H+) has at least two main receptor channels in dorsal root ganglia (DRG) nociceptors: the heat receptor transient receptor potential vanilloid 1 (TRPV1) and the acid-sensing ionic channels (ASICs). TRPV1 is a low-sensitivity H+ receptor, whereas ASIC channels display a higher H+ sensitivity of at least one order of magnitude. In this review, we first describe the functional and structural characteristics of these and other H+-receptor candidates and the biophysics of their responses to low pH. Additionally, we compile reports of the expression of these H+-receptors (and other possible complementary proteins) within the DRG and compare these data with mRNA expression profiles from single-cell sequencing datasets for ASIC3, ASIC1, transient receptor potential Ankiryn subtype 1 (TRPA1) and TRPV1. We show that few nociceptor subpopulations (discriminated by unbiased classifications) combine acid-sensitive channels. This comparative review is presented in light of the accumulating evidence for labeled-line coding for most noxious sensory stimuli.

Synergistic Interaction in the Analgesic-Like Effects of Maqui Berry and Citrus Is Antagonized by Sweeteners.

Although physiologically pain has a protective function, in many diseases, it is one of the most prominent symptoms. Today, new trends are focused on finding more natural alternatives to conventional treatments to alleviate it. Thereby, the purpose of this investigation was to obtain preclinical data of the antinociceptive properties of a lyophilized obtained from a newly designed maqui-citrus beverage alone and added with different sweeteners. To achieve this objective, maqui berry and citrus pharmacological activity were studied separately, as well as the interaction of both ingredients. In addition, due to the controversy generated regarding the intake of sugars, related to different metabolic diseases, the influence of different sweeteners (stevia, sucralose, or sucrose) was studied to determine their possible influence on the bioactive compounds of this product. For the attainment of our goals, a pharmacological evaluation, using the 1% formalin test, a nociceptive pain model in mice, was performed by using a sub-efficacious dosage of Maqui (25 mg/kg, i.p.) alone and combined with citrus, and then compared with the effects obtained in the presence of the different sweeteners. As a result, the antinociceptive response of the maqui was synergized in the presence of citrus in the neurogenic and inflammatory phases of the formalin test. However, this response was partially or totally reduced in the presence of the sweeteners. Our study gives preclinical evidence that a combination of maqui and citrus might exert beneficial actions to relieve pain, whereas the presence of sweeteners could reduce or avoid it.

Inflammatory nociception diminishes dopamine release and increases dopamine D2 receptor mRNA in the rat's insular cortex.

BACKGROUND: The insular cortex (IC) receives somatosensory afferent input and has been related to nociceptive input. It has dopaminergic terminals and D1 (D1R) -excitatory- and D2 (D2R) -inhibitory- receptors. D2R activation with a selective agonist, as well as D1R blockade with antagonists in the IC, diminish neuropathic nociception in a nerve transection model. An intraplantar injection of carrageenan and acute thermonociception (plantar test) were performed to measure the response to inflammation (paw withdrawal latency, PWL). Simultaneously, a freely moving microdyalisis technique and HPLC were used to measure the release of dopamine and its metabolites in the IC. Plantar test was applied prior, one and three hours after inflammation. Also, mRNA levels of D1 and D2R's were measured in the IC after three hours of inflammation. RESULTS: The results showed a gradual decrease in the release of dopamine, Dopac and HVA after inflammation. The decrease correlates with a decrease in PWL. D2R's increased their mRNA expression compared to the controls. In regard of D1R's, there was a decrease in their mRNA levels compared to the controls. CONCLUSIONS: Our results showed that the decreased extracellular levels of dopamine induced by inflammation correlated with the level of pain-related behaviour. These results also showed the increase in dopaminergic mediated inhibition by an increase in D2R's and a decrease in D1R's mRNA. There is a possible differential mechanism regarding the regulation of excitatory and inhibitory dopaminergic receptors triggered by inflammation.

Functional magnetic resonance imaging response to experimental pain in drug-free patients with schizophrenia.

Clinical evidence suggests that there is decreased pain sensitivity in schizophrenia; however, the neurobiological mechanism of this decrease remains unknown. Using functional magnetic resonance imaging, we examined the blood oxygen level-dependent (BOLD) changes induced by experimental pain-tolerance (endure) hot stimuli vs. non-painful stimuli during an acute psychotic episode in 12 drug-free patients with schizophrenia and in 13 gender- and age-matched healthy controls. The analyses revealed that patients showed a greater BOLD response at S1 compared with controls but a reduced BOLD response in the posterior cingulate cortex (PCC), insula, and brainstem during pain-tolerance stimuli. Pain-tolerance temperature was higher in patients than in healthy controls. BOLD response in the insula positively correlated with unpleasantness and temperature in controls, but this effect was not observed in patients. S1 BOLD response positively correlated with unpleasantness in patients but not in controls. These initial results confirm that unmedicated patients with schizophrenia have a higher pain tolerance than controls, decreased activation in pain affective-cognitive processing regions (insula, PCC, brainstem), and an over-activation of the primary sensory-discriminative pain processing region (S1). These pilot results are the first to explore the mechanism driving altered pain sensitivity in schizophrenia.

Environmental enrichment reduces behavioural sensitization in mice previously exposed to toluene: The role of D1 receptors.

It has been reported that environmental stimuli can positively influence addictive responses and the pharmacological effects of drugs of abuse. In this work, we evaluated the ability of environmental enrichment (EE) to attenuate addictive behaviours in mice after repeated exposure to toluene. We also analysed the role of D1 receptors (D1R) in animals chronically exposed to toluene and in those housed under EE. Mice (Swiss Webster) were exposed to toluene (0, 2000 or 4000 ppm, 30 min a day), and addictive responses were examined in the behavioural sensitization model. The induction of sensitization was evaluated over 4 weeks, and its expression was assessed in animals repeatedly exposed to toluene (0 or 4000 ppm, 30 min a day/4 weeks) and then housed under EE conditions during 4 more weeks. D1R levels were measured under these two experimental conditions in the prefrontal cortex, nucleus accumbens, hippocampus and caudate. The results showed that D1R levels decreased during toluene-induced behavioural sensitization. An increase in D1R levels was found in animals housed in EE conditions, in addition to the attenuated expression of behavioural sensitization. These results indicate that environmental stimulation attenuates addictive behaviour induced by toluene and that dynamic changes in D1R are linked in this response.