Pharmacological characterization of AM1710, a putative cannabinoid CB2 agonist from the cannabilactone class: antinociception without central nervous system side-effects.

Cannabinoid CB(2) agonists produce antinociception without central nervous system (CNS) side-effects. This study was designed to characterize the pharmacological and antinociceptive profile of AM1710, a CB(2) agonist from the cannabilactone class of cannabinoids. AM1710 did not exhibit off-target activity at 63 sites evaluated. AM1710 also exhibited limited blood brain barrier penetration. AM1710 was evaluated in tests of antinociception and CNS activity. CNS side-effects were evaluated in a modified tetrad (tail flick, rectal temperature, locomotor activity and rota-rod). Pharmacological specificity was established using CB(1) (SR141716) and CB(2) (SR144528) antagonists. AM1710 (0.1-10mg/kg i.p.) produced antinociception to thermal but not mechanical stimulation of the hindpaw. AM1710 (5mg/kg i.p.) produced a longer duration of antinociceptive action than the aminoalkylindole CB(2) agonist (R,S)-AM1241 (1mg/kg i.p.) at maximally antinociceptive doses. Antinociception produced by the low (0.1mg/kg i.p.) dose of AM1710 was blocked selectively by the CB(2) antagonist SR144528 (6mg/kg i.p.), whereas antinociception produced by the high dose of AM1710 (5mg/kg i.p.) was blocked by either SR144528 (6mg/kg i.p.) or SR141716 (6mg/kg i.p.). AM1710 did not produce hypoactivity, hypothermia, tail flick antinociception, or motor ataxia when evaluated in the tetrad at any dose. In conclusion, AM1710, a CB(2)-preferring cannabilactone, produced antinociception in the absence of CNS side-effects. Thus, any CB(1)-mediated antinociceptive effects of this compound may be attributable to peripheral CB(1) activity. The observed pattern of pharmacological specificity produced by AM1710 is consistent with limited blood brain barrier penetration of this compound and absence of CNS side-effects.

Endocannabinoids are expressed in bone marrow stromal niches and play a role in interactions of hematopoietic stem and progenitor cells with the bone marrow microenvironment.

Endocannabinoids are lipid signaling molecules that act via G-coupled receptors, CB(1) and CB(2). The endocannabinoid system is capable of activation of distinct signaling pathways on demand in response to pathogenic events or stimuli, hereby enhancing cell survival and promoting tissue repair. However, the role of endocannabinoids in hematopoietic stem and progenitor cells (HSPCs) and their interaction with hematopoietic stem cells (HSC) niches is not known. HSPCs are maintained in the quiescent state in bone marrow (BM) niches by intrinsic and extrinsic signaling. We report that HSPCs express the CB(1) receptors and that BM stromal cells secrete endocannabinoids, anandamide (AEA) (35 pg/10(7) cells), and 2-AG (75.2 ng/10(7) cells). In response to the endotoxin lipopolysaccharide (LPS), elevated levels of AEA (75.6 pg/10(7) cells) and 2-AG (98.8 ng/10(7) cells) were secreted from BM stromal cells, resulting in migration and trafficking of HSPCs from the BM niches to the peripheral blood. Furthermore, administration of exogenous cannabinoid CB(1) agonists in vivo induced chemotaxis, migration, and mobilization of human and murine HSPCs. Cannabinoid receptor knock-out mice Cnr1(-/-) showed a decrease in side population (SP) cells, whereas fatty acid amide hydrolase (FAAH)(-/-) mice, which have elevated levels of AEA, yielded increased colony formation as compared with WT mice. In addition, G-CSF-induced mobilization in vivo was modulated by endocannabinoids and was inhibited by specific cannabinoid antagonists as well as impaired in cannabinoid receptor knock-out mice Cnr1(-/-), as compared with WT mice. Thus, we propose a novel function of the endocannabinoid system, as a regulator of HSPC interactions with their BM niches, where endocannabinoids are expressed in HSC niches and under stress conditions, endocannabinoid expression levels are enhanced to induce HSPC migration for proper hematopoiesis.

The novel cannabinoid CB1 receptor neutral antagonist AM4113 suppresses food intake and food-reinforced behavior but does not induce signs of nausea in rats.

Drugs that interfere with cannabinoid CB1 transmission suppress various food-motivated behaviors, and it has been suggested that such drugs could be useful as appetite suppressants. Biochemical studies indicate that most of these drugs assessed thus far have been CB1 inverse agonists, and although they have been shown to suppress food intake, they also appear to induce nausea and malaise. The present studies were undertaken to characterize the behavioral effects of AM4113, which is a CB1 neutral antagonist, and to examine whether this drug can reduce food-reinforced behaviors and feeding on diets with varying macronutrient compositions. Biochemical data demonstrated that AM4113 binds to CB1 receptors, but does not show inverse agonist properties (ie no effects on cyclic-AMP production). In tests of spontaneous locomotion and analgesia, AM4113 reversed the effects of the CB1 agonist AM411. AM4113 suppressed food-reinforced operant responding with rats responding on fixed ratio (FR) 1 and 5 schedules of reinforcement in a dose-dependent manner, and also suppressed feeding on high-fat, high-carbohydrate, and lab chow diets. However, in the same dose range that suppressed feeding, AM4113 did not induce conditioned gaping, which is a sign of nausea and food-related malaise in rats. These results suggest that AM4113 may decrease appetite by blocking endogenous cannabinoid tone, and that this drug may be less associated with nausea than CB1 inverse agonists.