Administration Of Cannabinoid Receptor Agonist Research Articles

Chronic cannabinoid receptor stimulation selectively prevents motor impairments in a mouse model of Huntington's disease

Huntington's disease (HD) is a devastating neurodegenerative disease characterized by a progressive decline in motor abilities, as well as in cognitive and social behaviors. Most of these behavioral deficits are recapitulated in the R6/1 transgenic mouse, which can therefore be used as an experimental model to identify the neurobiological substrates of HD pathology and to design novel therapeutic approaches. The endocannabinoid system (ECS) is a relevant candidate to participate in the etiopathology of HD as it is a key modulator of brain function, especially in areas primarily affected by HD dysfunction such as the striatum. Thus, some studies have demonstrated an association between HD progression and alterations in the expression of several ECS elements, thereby suggesting that improving ECS function may constitute a useful strategy to eliminate or at least delay the appearance of HD symptoms. Here this hypothesis was specifically tested by evaluating whether the administration of a well-characterized cannabinoid receptor agonist (WIN 55,212), either acutely or chronically, improves the HD-like symptoms in R6/1 mice. While acute treatment did not change the behavioral phenotype of transgenic animals, chronic administration was able to prevent the appearance of motor deficits, to increase the number of striatal huntingtin inclusions and to prevent the loss of striatal medium-sized spiny neurons, without affecting the social or cognitive alterations. These findings suggest that prolonged administration of cannabinoid receptor agonists could be an appropriate strategy for selectively improving motor symptoms and stimulating neuroprotective processes in HD patients.

Improved Cardiac and Neurologic Outcomes With Postresuscitation Infusion of Cannabinoid Receptor Agonist WIN55, 212-2 Depend on Hypothermia in a Rat Model of Cardiac Arrest*

To investigate the mechanisms of improved myocardial and neurological function and survival following i.v. administration of cannabinoid receptor agonist, WIN55, 212-2 in a rat model of cardiac arrest. Prospective randomized controlled experimental study. University-affiliated research institute. Thirty male Sprague-Dawley rats. Ventricular fibrillation was electrically induced in 30 male Sprague-Dawley rats weighing between 450 and 550 g. Cardiopulmonary resuscitation was initiated after 6 minutes of untreated ventricular fibrillation. The precordial compression was performed with a pneumatically driven mechanical chest compressor. No pharmacological agent was used during cardiopulmonary resuscitation. After 8 minutes of cardiopulmonary resuscitation, up to three 2-J defibrillations were attempted. The animals were then randomized into three groups: 1) WIN55, 212-2 hypothermia, 2) WIN55, 212-2 with normal body temperature, and 3) placebo control. Either WIN55, 212-2 (1.0 mg/kg/hr) or saline placebo was continuously infused for 2 hours. Except for the WIN55, 212-2 hypothermia group, the body temperature in the other two groups was maintained at 37.0 ± 0.2°C using an external heating lamp. Postresuscitation myocardial function was measured by echocardiogram. Neurological deficit scores and survival time were observed for up to 72 hours. Blood temperatures decreased from 37°C to 33°C in 4 hours in animals in WIN55, 212-2 hypothermia group. Myocardial function, as measured by cardiac output, ejection fraction, and myocardial performance index, was significantly impaired in all animals after successful resuscitation when compared with the baseline values. There was a significant improvement in myocardial function in the animals treated with WIN55, 212-2 hypothermia beginning at 1 hour after start of infusion. However, no improvement was observed in the groups of WIN55, 212-2 with normal body temperature and placebo control. WIN55, 212-2 hypothermia group was associated with significantly improved neurologic deficit scores and survival time when compared with placebo control group and WIN55, 212-2 with normal body temperature group. In a rat model of cardiac arrest, better postresuscitation myocardial function, neurological deficit scores, and longer duration of survival were observed by the pharmacologically induced hypothermia with WIN55, 212-2. The improved outcomes of cardiopulmonary resuscitation following administration of WIN55, 212-2 appeared to be the results from its temperature reduction effects.

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Introduction: To determine the mechanisms of improved myocardial function and survival following administration of cannabinoid receptor agonist, WIN55, 212-2 in a rat post-cardiac arrest model. Hypothesis: We hypothesize that myocardial and neurological protective effects of WIN55, 212-2 are resulted from its temperature reduction effect. Methods: Ventricular fibrillation (VF) was electrically induced in 30 male Sprague-Dawley rats weighing between 450 - 550g. CPR was initiated after 6 min of untreated VF. After 8 min of CPR, up to three 2-J defibrillations were attempted. Restoration of spontaneous circulation (ROSC) was defined as return of supra ventricular rhythm with a mean aortic pressure above 50 mmHg for 5 min. If ROSC was not achieved, a 30 sec interval of CPR was performed prior to attempt a subsequent sequence of up to 3 shocks until successful resuscitation or for a maximum of 3 cycle attempts. Five min after post-resuscitation, the animals were randomized into 3 groups: (1) WIN55, 212-2 with normothermia; (2) WIN55, 212-2 alone; (3) control. Thirty mins after ROSC, the animals received continuous intravenous infusion of WIN55, 212-2 (1.0 mg/kg.h) for 2 hrs while control animals received a placebo. Except for the group in WIN55, 212-2 alone, the body temperature in the other 2 groups were maintained at 37.0 ± 0.2°C with the aid of a heating lamp to prevent spontaneous or pharmacologically induced hypothermia. The room temperature was identical in all animals. Neurological deficit scores (NDS) and survival time were observed for up to 72 hrs. Results: Blood temperatures decreased progressively in animals treated with WIN55, 212-2 alone from 37°C to 33°C in 4 hrs. Post-resuscitation myocardial function, NDS and survival time were significantly better in this group when compared with the control group. However, in animals treated with WIN55, 212-2 and normothermia, there were no statistical differences in post-resuscitation myocardial function, NDS and survival time when compared with the control group. Conclusions: In a rat model of cardiac arrest, better post-resuscitation myocardial function, neurological deficit scores and longer duration of survival were observed by the pharmacologically induced hypothermia with WIN55, 212-2. However, the protective effects of WIN55, 212-2 were diminished when body temperature was maintained at the normal level.

Intrathecal Administration of the Cannabinoid 2 Receptor Agonist JWH015 Can Attenuate Cancer Pain and Decrease mRNA Expression of the 2B Subunit of N-Methyl-D-Aspartic Acid

Cannabinoids bind to cannabinoid receptors type 1 and 2 and produce analgesia in several pain models, but central side effects from cannabinoid 1 receptors limit their clinical use. Because of the pain-relieving effects of cannabinoid 2 (CB2) receptor agonists in inflammation pain, incision pain, and neuropathic pain models, we tested whether spinal CB2 receptor activation would induce antihyperalgesia in cancer pain. Our previous study showed that the 2B subunit of N-methyl-D-aspartate (NR2B) receptor in the spinal cord participates in bone cancer pain in mice. In the present study, we also tested the cannabinoid effect on the expression of NR2B. Seventy-two mice were randomly allocated to 7 different groups: (1) control; (2) sham and tumor-bearing mice, which include (3) V; (4) J1; (5) J2; (6) J3; and (7) J4. In the groups of tumor-bearing mice, C(3)H/Hej mice were implanted with NCTC2472 fibrosarcoma cells into the femur bone to induce bone cancer-related pain behaviors. The sham mice were implanted with minimal essential medium α modification, whereas the control mice received no injection. On day 14 after implantation, tumor-invoked tactile allodynia and thermal hyperalgesia were assessed. Tumor-bearing mice were assigned to intrathecal administration of the CB2 receptor agonist JWH015 (0.5, 1, and 2 μg), CB2 receptor antagonist AM630 (2 μg), or vehicle, and the assessment of withdrawal thresholds was then performed. Tactile allodynia and thermal hyperalgesia were assessed before administration and at 1 hour, 6 hours, 12 hours, 24 hours, 48 hours, and 72 hours after administration. Spinal NR2B activation of all tumor-bearing mice at 12 hours and 72 hours were determined by reverse transcription-polymerase chain reaction analyses. At day 14 after operation, tumor-evoked tactile allodynia and thermal hyperalgesia were higher in tumor-bearing mice compared with the sham and control mice. Intrathecal administration of JWH015 dose dependently attenuated tumor-evoked tactile allodynia and thermal hyperalgesia but this effect was prevented by intrathecal administration of AM630 30 minutes before. The mRNA expression of NR2B was similar to this result. At 12 hours after administration, the expression of NR2B mRNA in the spinal cord was lower in mice that were administered JWH015 compared with the vehicle group. However, this phenomenon was reversed in the group that was preadministered AM630. These data indicated that intrathecal administration of cannabinoid receptor agonists might relieve cancer pain, probably by reducing NR2B-dependent activity in the spinal cord. These results also suggested that cannabinoids might be a useful alternative or adjunct therapy for relieving cancer pain.

Cannabinoids attenuate cancer pain and proliferation in a mouse model

We investigated the effects of cannabinoid receptor agonists on (1) oral cancer cell viability in vitro and (2) oral cancer pain and tumor growth in a mouse cancer model. We utilized immunohistochemistry and Western blot to show that human oral cancer cells express CBr1 and CBr2. When treated with WIN55,212-2 (non-selective), ACEA (CBr1-selective) or AM1241 (CBr2-selective) agonists in vitro, oral cancer cell proliferation was significantly attenuated in a dose-dependent manner. In vivo, systemic administration (0.013 M) of WIN55,212-2, ACEA, or AM1241 significantly attenuated cancer-induced mechanical allodynia. Tumor growth was also significantly attenuated with systemic AM1241 administration. Our findings suggest a direct role for cannabinoid mechanisms in oral cancer pain and proliferation. The systemic administration of cannabinoid receptor agonists may have important therapeutic implications wherein cannabinoid receptor agonists may reduce morbidity and mortality of oral cancer.

Influence of intracerebroventricular or intraperitoneal administration of cannabinoid receptor agonist (WIN 55,212-2) and inverse agonist (AM 251) on the regulation of food intake and hypothalamic serotonin levels

The effect of intracerebroventricular or intraperitoneal administration of cannabinoid receptor agonist WIN 55,212-2 or inverse agonist AM 251 on food intake and extracellular levels of serotonin and acetic acid 5-hydroxy-indol from presatiated rats was studied. Compared to the vehicle-injected control, the intracerebroventricular administration of WIN 55,212-2 was associated with a significant increase in food intake, whereas the administration of AM 251 caused a significant reduction in this respect. These results were accompanied by considerable reductions or increases in serotonin and acetic acid 5-hydroxy-indol levels compared to the vehicle-injected control and the baseline values for the different experimental groups studied. Intraperitoneal administration of WIN 55,212-2 at doses of 1 and 2 mg/kg promoted hyperphagia up to 6 h after injection, whereas administration of a higher dose (5 mg/kg) significantly inhibited food intake and motor behaviour in partially satiated rats. Administration of any of the AM 251 doses studied (0.5, 1, 2, 5 mg/kg) led to a significant decrease in the amount of food ingested from 2 h after the injection, compared to the vehicle-injected control group, with the most striking effect being observed when the 5 mg/kg dose was injected.

Gz Mediates the Long-Lasting Desensitization of Brain CB1 Receptors and is Essential for Cross-Tolerance with Morphine

BackgroundAlthough the systemic administration of cannabinoids produces antinociception, their chronic use leads to analgesic tolerance as well as cross-tolerance to morphine. These effects are mediated by cannabinoids binding to peripheral, spinal and supraspinal CB1 and CB2 receptors, making it difficult to determine the relevance of each receptor type to these phenomena. However, in the brain, the CB1 receptors (CB1Rs) are expressed at high levels in neurons, whereas the expression of CB2Rs is marginal. Thus, CB1Rs mediate the effects of smoked cannabis and are also implicated in emotional behaviors. We have analyzed the production of supraspinal analgesia and the development of tolerance at CB1Rs by the direct injection of a series of cannabinoids into the brain. The influence of the activation of CB1Rs on supraspinal analgesia evoked by morphine was also evaluated.ResultsIntracerebroventricular (icv) administration of cannabinoid receptor agonists, WIN55,212-2, ACEA or methanandamide, generated a dose-dependent analgesia. Notably, a single administration of these compounds brought about profound analgesic tolerance that lasted for more than 14 days. This decrease in the effect of cannabinoid receptor agonists was not mediated by depletion of CB1Rs or the loss of regulated G proteins, but, nevertheless, it was accompanied by reduced morphine analgesia. On the other hand, acute morphine administration produced tolerance that lasted only 3 days and did not affect the CB1R. We found that both neural mu-opioid receptors (MORs) and CB1Rs interact with the HINT1-RGSZ module, thereby regulating pertussis toxin-insensitive Gz proteins. In mice with reduced levels of these Gz proteins, the CB1R agonists produced no such desensitization or morphine cross-tolerance. On the other hand, experimental enhancement of Gz signaling enabled an acute icv administration of morphine to produce a long-lasting tolerance at MORs that persisted for more than 2 weeks, and it also impaired the analgesic effects of cannabinoids.ConclusionIn the brain, cannabinoids can produce analgesic tolerance that is not associated with the loss of surface CB1Rs or their uncoupling from regulated transduction. Neural specific Gz proteins are essential mediators of the analgesic effects of supraspinal CB1R agonists and morphine. These Gz proteins are also responsible for the long-term analgesic tolerance produced by single doses of these agonists, as well as for the cross-tolerance between CB1Rs and MORs.

Spinal Cannabinoid Receptor Type 2 Activation Reduces Hypersensitivity and Spinal Cord Glial Activation after Paw Incision

Cannabinoids bind to cannabinoid receptors type 1 and 2 and produce analgesia in several pain models, but central side effects from cannabinoid 1 receptors limit their clinical use. Cannabinoid 2 receptors reduce inflammatory responses in the periphery by acting on immune cells, and they are present on glia in the central nervous system. This study tested whether spinal cannabinoid activation would induce analgesia, glial inhibition, and central side effects in a postoperative model or incisional pain. Rats underwent paw incision surgery, with intrathecal injections of cannabinoid agonists and antagonists and assessment of withdrawal thresholds and behavioral side effects. Spinal glial activation was determined by immunohistochemistry. Intrathecal administration CP55940 reduced postoperative hypersensitivity (91 +/- 9% maximum possible effect; P < 0.05), and this was prevented by intrathecal administration of both cannabinoid 1 receptor (AM281) and cannabinoid 2 receptor (AM630) antagonists. CP55940 also caused several behavioral side effects, and these were prevented by the cannabinoid 1 receptor but not by the cannabinoid 2 receptor antagonist. Intrathecal injection of the cannabinoid 2 receptor agonist JWH015 reversed postoperative hypersensitivity (89 +/- 5% maximum possible effect; P < 0.05), and this was reversed by the cannabinoid 2 but not by the cannabinoid 1 receptor antagonist. JWH015, which did not induce behavioral side effects, reduced paw incision induced microglial and astrocytic activation in spinal cord (P < 0.05). These data indicate that intrathecal administration of cannabinoid receptor agonists may provide postoperative analgesia while reducing spinal glial activation, and that selective cannabinoid 2 receptor agonists may do so without central side effects.