piperidines and iodoresiniferatoxin

The molecular mechanism of action of dipyrone, a widely used antipyretic and non-opioid analgesic drug, is still not fully understood. Actions upon peripheral inflamed tissues as well as the central nervous system, especially upon the PAG-RVM axis, have been suggested. Dipyrone is a prodrug and its activity is due to its immediate conversion to its active metabolites. We tested the effect of two recently discovered metabolites of dipyrone, the arachidonoyl amides of 4-methylaminoantipyrine and 4-aminoantipyrine, on the neurons of the rostral ventromedial medulla (RVM), which are part of the descending pathway of antinociception. These compounds reduced the activity of ON-cells and increased the activity of OFF-cells. Both CB1 and TRPV1 blockade reversed these effects, suggesting that the endocannabinoid/endovanilloid system takes part in the analgesic effects of dipyrone.

Topics: Analgesics; Animals; Arachidonic Acid; Dipyrone; Diterpenes; Drug Interactions; Extracellular Space; Male; Mechanical Phenomena; Mesencephalon; Mice; Neurons; Piperidines; Pyrazoles; Receptor, Cannabinoid, CB1; TRPV Cation Channels

It has been reported that the endocannabinoid anandamide (AEA) exerts an adverse effect on human sperm motility, which has been ascribed to inhibition of mitochondrial activity. This seems to be at variance with evidence suggesting a major role of glycolysis in supplying ATP for sperm motility; furthermore, the role of AEA-binding receptors in mediating mitochondrial inhibition has not yet been explored. In this study, human sperm exposure to Met-AEA (methanandamide, nonhydrolyzable analog of AEA) in the micromolar range significantly decreased mitochondrial transmembrane potential (ΔΨm), similarly to rotenone, mitochondrial complex I inhibitor. The effect of Met-AEA (1 μm) was prevented by SR141716, CB(1) cannabinoid receptor antagonist, but not by SR144528, CB(2) antagonist, nor by iodoresiniferatoxin, vanilloid receptor antagonist. The effect of Met-AEA did not involve activation of caspase-9 or caspase-3 and was reverted by washing. In the presence of glucose, sperm exposure either to Met-AEA up to 1 μm or to rotenone for up to 18 h did not affect sperm motility. At higher doses Met-AEA produced a CB(1)-independent poisoning of spermatozoa, reducing their viability. Under glycolysis blockage, 1 μm Met-AEA, similarly to rotenone, dramatically abolished sperm motility, an effect that was prevented by SR1 and reverted by washing. In conclusion, CB(1) activation induced a nonapoptotic decrease of ΔΨm, the detrimental reflection on sperm motility of which could be revealed only under glycolysis blockage, unless very high doses of Met-AEA, producing CB(1)-independent sperm toxicity, were used. The effects of CB(1) activation reported here contribute to elucidate the relationship between energetic metabolism and human sperm motility.

Topics: Camphanes; Diterpenes; Dose-Response Relationship, Drug; Energy Metabolism; Glucose; Glycolysis; Humans; Male; Piperidines; Pyrazoles; Receptor, Cannabinoid, CB1; Rimonabant; Rotenone; Sperm Motility; Spermatozoa; Uncoupling Agents

Anandamide is an endogenous agonist for cannabinoid receptors and produces analgesia by acting at these receptors in several sites in the brain and peripheral nervous system. Anandamide is also an agonist at the TRPV1 receptor, a protein that serves as an important integrator of noxious stimuli in sensory neurons. Although anandamide actions at CB1 and TRPV1 receptors can explain many of its effects on sensory neurons, some apparently CB1- and TRPV1-independent effects of anandamide have been reported. To explore possible mechanisms underlying these effects we examined the actions of the stable anandamide analog methanandamide on the membrane properties of trigeminal ganglion neurons from mice with TRPV1 deleted. We found that methanandamide and anandamide activate a novel current in a subpopulation of small trigeminal ganglion neurons. Methanandamide activated the current (EC(50) 2 microM) more potently than it activates TRPV1 under the same conditions. The methanandamide-activated current reverses at 0 mV and does not inactivate at positive potentials but declines rapidly at negative membrane potentials. Activation of the current is not mediated via cannabinoid receptors and does not appear to involve G proteins. The phytocannabinoid Delta(9)-tetrahydrocannabinol, the endocannabinoid-related molecules N-arachidonoyl dopamine and N-arachidonoyl glycine and the non-specific TRPV channel activator 2-aminoethoxydiphenyl borate do not mimic the effects of methanandamide. The molecular identity of the current remains to be established, but we have identified a potential new effector for endocannabinoids in sensory neurons, and activation of this current may underlie some of the previously reported CB1 and TRPV1-independent effects of these compounds.

Topics: Animals; Arachidonic Acids; Calcium Channel Blockers; Diterpenes; Dose-Response Relationship, Drug; Dose-Response Relationship, Radiation; Dronabinol; Drug Interactions; Electric Stimulation; Endocannabinoids; Female; In Vitro Techniques; Male; Membrane Potentials; Mice; Mice, Inbred C57BL; Mice, Knockout; Neurons, Afferent; Patch-Clamp Techniques; Piperidines; Polyunsaturated Alkamides; Pyrazoles; Rimonabant; Trigeminal Ganglion; TRPV Cation Channels

The presence of cannabinoid1 (CB1) receptors on primary afferent fibres may provide a novel target for cannabinoid analgesics. The present study investigated the ability of peripheral CB1 receptors to modulate innocuous and noxious transmission in noninflamed rats and rats with peripheral carrageenan inflammation. Effects of peripheral injection of arachidonyl-2-choroethylamide (ACEA; 10 and 30 micro g in 50 micro L), a selective CB1 receptor agonist, on mechanically evoked responses of dorsal horn neurons were studied in noninflamed rats and rats with peripheral carrageenan inflammation. Peripheral injection of ACEA (30 micro g in 50 micro L) significantly inhibited innocuous (12 g) mechanically evoked responses of spinal neurons in noninflamed (27 +/- 4% of control; P < 0.01) and inflamed (12 +/- 8% of control; P < 0.05) rats. Similarly, noxious (80 g) mechanically evoked responses of spinal neurons were inhibited by peripheral injection of ACEA (30 micro g in 50 micro L) in noninflamed rats (51 +/- 9% of control; P < 0.01) and rats with peripheral carrageenan inflammation (21 +/- 8% of control; P < 0.01). Inhibitory effects of ACEA were significantly greater in rats with peripheral carrageenan inflammation than in noninflamed rats (P < 0.05). Inhibitory effects of ACEA were significantly blocked by coadministration of the CB1 receptor antagonist SR141716A in both groups of rats. Peripheral injection of SR141716A alone did not alter mechanically evoked responses of spinal neurons in either group of rats. These data demonstrate that activation of peripheral CB1 receptors can inhibit innocuous and noxious somatosensory processing. Furthermore, following peripheral inflammation there is an enhanced inhibitory effect of a peripherally administered CB1 receptor agonist on both innocuous and noxious mechanically evoked responses of spinal neurons.

Topics: Animals; Arachidonic Acids; Carrageenan; Diterpenes; Dose-Response Relationship, Drug; Drug Interactions; Evoked Potentials; Hindlimb; Inflammation; Male; Neural Inhibition; Physical Stimulation; Piperidines; Posterior Horn Cells; Pyrazoles; Rats; Rats, Sprague-Dawley; Receptor, Cannabinoid, CB1; Receptors, Drug; Rimonabant; Spinal Cord; Time Factors