“Several works have shown that triterpenes induce peripheral antinociception by activation of cannabinoid receptors and endocannabinoids; besides, several research groups have reported activation of cannabinoid receptors in peripheral antinociception.
The aim of this study was to assess the involvement of the cannabinoid system in the antinociceptive effect induced by tingenone against hyperalgesia evoked by prostaglandin E2 (PGE2) at peripheral level.
The results suggest that tingenone induced a peripheral antinociceptive effect via cannabinoidreceptor activation. Therefore, this study suggests a pharmacological potential for a new analgesic drug.”
“Fish dorsomedial telencephalon has been considered a pallial region homologous to mammals amygdala, being considered a possible substrate for nociception modulation in this animal group. The present study aimed to evaluate the participation of the cannabinoid system of Dm telencephalon on nociception modulation in the fish Leporinus macrocephalus. We demonstrated that cannabidiol microinjection in Dm telecephalon inhibits the behavioral nociceptive response to the subcutaneous injection of 3% formaldehyde, and this antinociception is blocked by previous treatment with AM251 microinjection. Furthermore, AM251 microinjection in Dm prior to restraint stress also blockades the stress-induced antinociception. These results reinforce the hypothesis that this pallial telencephalic structure has a pivotal role in nociception modulation in fish.”
“Endocannabinoids and opioids play a vital role in mediating pain-induced analgesia.
The specific effects of these compounds within orofacial region are largely unknown. In this study we tried to determine whether the increase of cannabinoid and opioid concentration in cerebrospinal fluid affects impulse transmission between the motor centers localized in the vicinity of the third and fourth cerebral ventricles.
We demonstrated that in the orofacial area analgesic activity is modulated by AEA and that EM-2-induced antinociception was mediated by MOR and CB1 receptors. The action of AEA and EM-2 is tightly regulated by FAAH and FAAH/MAGL, by preventing the breakdown of endogenous cannabinoids in regions where they are produced on demand.
Therefore, the current findings support the therapeutic potential of FAAH and FAAH/MAGL inhibitors as novel pharmacotherapeutic agents for orofacial pain.”
“Although opioids are highly efficacious analgesics, their abuse potential and other untoward side effects diminish their therapeutic utility. The addition of non-opioid analgesics offers a promising strategy to reduce required antinociceptive opioid doses that concomitantly reduce opioid-related side effects.
Inhibitors of the primary endocannabinoid catabolic enzymes fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MAGL) show opioid-sparing effects in preclinical models of pain. As simultaneous inhibition of these enzymes elicits enhanced antinociceptive effects compared with single enzyme inhibition, the present study tested whether the dual FAAH-MAGL inhibitor SA-57 [4-[2-(4-chlorophenyl)ethyl]-1-piperidinecarboxylic acid 2-(methylamino)-2-oxoethyl ester] produces morphine-sparing antinociceptive effects, without major side effects associated with either drug class.
Although high doses of SA-57 alone were required to produce antinociception, low doses of this compound, which elevated AEA and did not affect 2-AG brain levels, augmented the antinociceptive effects of morphine, but lacked cannabimimetic side effects.
Because of the high abuse liability of opioids and implication of the endocannabinoid system in the reinforcing effects of opioids, the final experiment tested whether SA-57 would alter heroin seeking behavior. Strikingly, SA-57 reduced heroin-reinforced nose poke behavior and the progressive ratio break point for heroin.
In conclusion, the results of the present study suggest that inhibition of endocannabinoid degradative enzymes represents a promising therapeutic approach to decrease effective doses of opioids needed for clinical pain control, and may also possess therapeutic potential to reduce opioid abuse.”
“The gonadal hormones testosterone (T) in adult males and estradiol (E2) in adult females have been reported to modulate behavioral effects of ∆9-tetrahydrocannabinol (THC). This study determined whether activational effects of T and E2 are sex-specific, and whether hormones modulate production of the active metabolite 11-hydroxy-THC (11-OH-THC) and the inactive metabolite 11-nor-9-carboxy-THC (THC-COOH). Adult male and female rats were gonadectomized (GDX) and treated with nothing (0), T (10-mm Silastic capsule/100g body weight), or E2 (1-mm Silastic capsule/rat). Three weeks later, saline or the cytochrome P450 inhibitor proadifen (25mg/kg; to block THC metabolism and boost THC’s effects) was injected i.p.; 1h later, vehicle or THC (3mg/kg females, 5mg/kg males) was injected i.p., and rats were tested for antinociceptive and motoric effects 15-240min post-injection. T did not consistently alter THC-induced antinociception in males, but decreased it in females (tail withdrawal test). Conversely, T decreased THC-induced catalepsy in males, but had no effect in females. E2 did not alter THC-induced antinociception in females, but enhanced it in males. The discrepant effects of T and E2 on males’ and females’ behavioral responses to THC suggests that sexual differentiation of THC sensitivity is not simply due to activational effects of hormones, but also occurs via organizational hormone or sex chromosome effects. Analysis of serum showed that proadifen increased THC levels, E2 increased 11-OH-THC in GDX males, and T decreased 11-OH-THC (and to a lesser extent, THC) in GDX females. Thus, hormone modulation of THC’s behavioral effects is caused in part by hormone modulation of THC oxidation to its active metabolite. However, the fact that hormone modulation of metabolism did not alter THC sensitivity similarly on all behavioral measures within each sex suggests that other mechanisms also play a role in gonadal hormone modulation of THC sensitivity in adult rats.”
“Several studies in humans have reported that improved pain control is associated with exercise in a variety of painful conditions, including osteoarthritis, fibromyalgia, and neuropathic pain.
Despite the growing amount of experimental data on physical exercise and nociception, the precise mechanisms through which high-intensity exercise reduces pain remain elusive.
Since the glutamatergic system plays a major role in pain transmission, we firstly analyzed if physical exercise could be able to decrease glutamate-induced nociception through G-protein-coupled receptor (G-PCR) activation.
The second purpose of this study was to examine the effect of exercising upon phosphorylation of protein kinase A (PKA) isoforms induced by intraplantar (i.pl.) glutamate injection in mice.
Our results demonstrate that high-intensity swimming exercise decreases nociception induced by glutamate and that i.pl. or intrathecal injections of cannabinoid, opioid, and adenosine receptor antagonists, AM281, naloxone, and 1,3-dipropyl-8-cyclopentylxanthine (DPCPX), respectively, prevent this effect.
Furthermore, the peripheral A1 and opioid receptors, but not CB1, are also involved in exercise’s effect. We also verified that glutamate injection increases levels of phosphorylated PKA (p-PKA). High-intensity swimming exercise significantly prevented p-PKA increase.
The current data show the direct involvement of the glutamatergic system on the hyponociceptive effect of high-intensity swimming exercise as well as demonstrate that physical exercise can activate multiple intracellular pathways through G-PCR activation, which share the same endogenous mechanism, i.e., inhibition of p-PKA.”
“Peltatoside is a natural compound isolated from leaves of Annona crassiflora Mart., a plant widely used in folk medicine.
This substance is an analogue of quercetin, a flavonoid extensively studied because of its diverse biological activities, including analgesic effects. Besides, a previous study suggested, by computer structure analyses, a possible quercetin-CB1cannabinoid receptor interaction.
Thus, the aim of this work was to assess the antinociceptive effect of peltatoside and analyze the cannabinoid system involvement in this action.
Our results suggest that this natural substance is capable of inducing analgesia through the activation of peripheral CB1 receptors, involving endocannabinoids in this process.”
“There is no published study regarding the interaction between muscarinic receptor modulators and antinociception induced by cannabinoidreceptor (CB2) agonist. The effect of pilocarpine (a muscarinic agonist) and atropine (a muscarinic antagonist) on JWH-133 (a CB2 agonist) induced analgesia in mice was studied. First the analgesic effect of JWH-133 (0.001-1 mg/Kg) or pilocarpine (2.5-20 mg/kg) or atropine (0.2-5 mg/kg) was evaluated. Subsequently, the effect of co-administration of pilocarpine (2.5 mg/kg) or atropine (5 mg/kg) and JWH-133 (0.001-1 mg/Kg) were studied too. JWH-133 and pilocarpine provoked antinociception in mice but atropine did not. Pilocarpine potentiated the analgesic effect of JWH-133 but atropine antagonized that. It can be concluded that JWH-133 induced antinociception is affected by muscarinic receptor modulators in mice.”