piperidines and 7-nitroindazole

A growing bulk of evidence suggests that cannabinoid system plays a pivotal role in the control of hyperexcitability phenomena. Notwithstanding, the anticonvulsant action of cannabinoids has not been fully addressed, in particular the involvement of potential cellular neuromodulators, for instance nitric oxide. In the current study, we focused on two distinct rat models of temporal lobe epilepsy, the Maximal Dentate Activation and the pilocarpine-induced acute seizures, providing both electrophysiological and behavioral data on cannabinoid and nitrergic system interplay. We evaluated the antiepileptic effects of WIN 55,212-2, (R)-(+)-[2,3-dihydro-5-methyl-3-(4-morpholinylmethyl) pyrrolo[1,2,3-de]-1,4-benzoxazin-6-Yl]-1-naphthalenylmethanone (WIN), a CB agonist, and of 7-Nitroindazole (7NI), a preferential neuronal nitric oxide synthase (nNOS) inhibitor, at different doses, alone and in combination. MDA study showed that these drugs protected animals in a dose-dependent manner from electrically induced epileptiform discharges. In pilocarpine model, a dose-related activity of 7NI and WIN: a) decreased the behavioral scoring, used to describe the severity of chemically induced acute seizures; b) affected latency of the onset of acute convulsions; c) dampened mortality rate. Interestingly, the combination of the treatments brought to light that individually ineffective doses of WIN turn into effective when nNOS activity is pharmacologically inhibited in both experimental conditions. This effect is mediated by CB1 receptor since the co-administration of N-(piperidin-1-yl)-5-(4-iodophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide (AM251), a CB1 receptor specific antagonist, thwarted the 7NI-WIN convergent action. In the light of this, our findings suggest a putative antagonism between CBr-activated pathway and NO signaling in the context of neuronal hyperexcitability and contribute to elucidate possible synaptic processes underlying neuroprotective properties of cannabinoids, with a view to better integrate antiepileptic therapy.

Topics: Animals; Benzoxazines; Cannabinoid Receptor Agonists; Cannabinoids; Disease Models, Animal; Dose-Response Relationship, Drug; Epilepsy, Temporal Lobe; Hippocampus; Indazoles; Male; Morpholines; Naphthalenes; Nitric Oxide; Nitric Oxide Synthase; Pilocarpine; Piperidines; Pyrazoles; Rats; Rats, Wistar; Receptor, Cannabinoid, CB1

An investigation was made to explore the possibility of anxiolytic activity of piperine in unstressed and stressed mice along with the underlying role of nitriergic and GABAergic modulation for the noted activity of piperine.. Piperine (5, 10 and 20mg/kg, ip) was administered to unstressed mice. In another groups of animals, piperine was administered 30 min before subjecting them to immobilization stress for 6h. Antianxiety activity was evaluated by employing elevated plus maze, light-dark box and social interaction test. Diazepam was employed as standard anxiolytic drug.. Piperine produced significant antianxiety-like activity in unstressed and stressed mice. The anxiolytic-like activity of piperine was comparable to diazepam. In unstressed mice, piperine significantly increased brain GABA levels, but could not produce any change in plasma nitrite levels. Meanwhile, in stressed mice, piperine did not produce any significant change in GABA levels, but significantly decreased nitrite levels. Pre-treatment with aminoguanidine (50mg/kg, ip), an inducible nitric oxide synthase (NOS) inhibitor, significantly potentiated the anxiolytic-like activity of piperine, as compared to piperine and aminoguanidine alone in stressed mice. On the other hand, pretreatment with 7-nitroindazole (20mg/kg, ip), a neuronal NOS inhibitor significantly potentiated the antianxiety-like activity of piperine, as compared to piperine and 7-nitroindazole alone in unstressed mice.. These data suggest that the piperine produced significant anxiolytic activity in unstressed mice possibly through increase in GABA levels and inhibition of neuronal NOS. On the other hand, antianxiety activity in stressed mice might be through inhibition of inducible NOS.

Topics: Alkaloids; Animals; Anti-Anxiety Agents; Anxiety; Benzodioxoles; Diazepam; Disease Models, Animal; Dose-Response Relationship, Drug; gamma-Aminobutyric Acid; Guanidines; Indazoles; Male; Maze Learning; Mice; Nitric Oxide Synthase Type I; Nitric Oxide Synthase Type II; Nitrites; Piperidines; Polyunsaturated Alkamides; Stress, Psychological

Oxaliplatin is a platinum-based chemotherapy drug characterized by the development of acute and chronic peripheral neuropathies. The chronic neuropathy is a dose-limiting toxicity. We previously reported that repeated administration of oxaliplatin induced cold hyperalgesia in the early phase and mechanical allodynia in the late phase in rats. In the present study, we investigated the involvement of NR2B-containing N-methyl-D-aspartate (NMDA) receptors in oxaliplatin-induced mechanical allodynia in rats.. Repeated administration of oxaliplatin (4 mg/kg, i.p., twice a week) caused mechanical allodynia in the fourth week, which was reversed by intrathecal injection of MK-801 (10 nmol) and memantine (1 μmol), NMDA receptor antagonists. Similarly, selective NR2B antagonists Ro25-6981 (300 nmol, i.t.) and ifenprodil (50 mg/kg, p.o.) significantly attenuated the oxaliplatin-induced pain behavior. In addition, the expression of NR2B protein and mRNA in the rat spinal cord was increased by oxaliplatin on Day 25 (late phase) but not on Day 5 (early phase). Moreover, we examined the involvement of nitric oxide synthase (NOS) as a downstream target of NMDA receptor. L-NAME, a non-selective NOS inhibitor, and 7-nitroindazole, a neuronal NOS (nNOS) inhibitor, significantly suppressed the oxaliplatin-induced pain behavior. The intensity of NADPH diaphorase staining, a histochemical marker for NOS, in the superficial layer of spinal dorsal horn was obviously increased by oxaliplatin, and this increased intensity was reversed by intrathecal injection of Ro25-6981.. These results indicated that spinal NR2B-containing NMDA receptors are involved in the oxaliplatin-induced mechanical allodynia.

Topics: Animals; Dizocilpine Maleate; Enzyme Inhibitors; Gene Expression Regulation; Hyperalgesia; Indazoles; Male; Memantine; Neurons; NG-Nitroarginine Methyl Ester; Nitric Oxide Synthase; Organoplatinum Compounds; Oxaliplatin; Phenols; Piperidines; Rats; Rats, Sprague-Dawley; Receptors, N-Methyl-D-Aspartate; RNA, Messenger; Spinal Cord

Spinal N-methyl d-aspartate receptor (NMDAR) plays a pivotal role in nerve injury-induced central sensitization. Recent studies suggest that NMDAR also contributes to neuron-astrocyte signaling. c-Jun N-terminal kinase (JNK) is persistently and specifically activated (indicated by phosphorylation) in spinal cord astrocytes after nerve injury and thus it is considered as a dependable indicator of pain-related astrocytic activation. NMDAR-mediated JNK activation in spinal dorsal horn might be an important form of neuron-astrocyte signaling in neuropathic pain. In the present study, we observed that intrathecal injection of MK-801, a noncompetitive NMDA receptor antagonist, or Ro25-6981 and ifenprodil, which are selective antagonists of NR2B-containing NMDAR each significantly reduced nerve injury-induced JNK activation. Double immunostaining showed that NR2B was highly expressed in neurons, indicating the effect of NMDAR antagonists on JNK activation was indirect. We further observed that intrathecal injection of NMDA (twice a day for 3 days) significantly increased spinal JNK phosphorylation. Besides, NMDAR-related JNK activation could be blocked by a neuronal nitric oxide synthase (nNOS) selective inhibitor (7-nitroindazole sodium salt) but not by a nNOS sensitive guanylyl cyclase inhibitor (1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one). Finally, real-time RT-PCR and immunostaining showed that nerve injury-induced interleukin-1beta expression was dependent on astrocytic JNK activation. Treatments targeting NMDAR-nNOS pathway also influenced interleukin-1beta expression, which further confirmed our hypothesis. Taken together, our results suggest that neuronal NMDAR-nNOS pathway could activate astrocytic JNK pathway. Excitatory neuronal transmission initiates astrocytic activation-induced neuroinflammation in this way, which contributes to nerve injury-induced neuropathic pain.

Topics: Animals; Astrocytes; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; Guanylate Cyclase; Hyperalgesia; Indazoles; JNK Mitogen-Activated Protein Kinases; Male; Neuralgia; Neurons; Nitric Oxide Synthase Type I; Pain Measurement; Phenols; Phosphorylation; Piperidines; Rats; Rats, Sprague-Dawley; Receptors, N-Methyl-D-Aspartate; Signal Transduction; Spinal Cord

To investigate whether nitric oxide (NO) regulates retinal circulation during and after induction of hyperoxia in cats.. Hyperoxia was induced for 10 minutes with 100% oxygen. The vessel diameter and blood velocity were measured simultaneously in second-order retinal arterioles by laser Doppler velocimetry; the retinal blood flow (RBF) and wall shear rate (WSR) were calculated during and after hyperoxia. PBS, L-NAME, D-NAME, BQ-123, BQ-788, and 7-nitroindazole (7-NI) were administered before induction of hyperoxia.. In the PBS group, vessel diameter, blood velocity, and RBF decreased during hyperoxia and returned to baseline within 10 minutes after hyperoxia ended. WSR decreased transiently and then returned to baseline by the delayed constriction of retinal arterioles during hyperoxia. In the l-NAME and BQ-788 groups, the decreases in RBF during hyperoxia did not differ from those in the PBS group. However, the recovery of RBF after hyperoxia ended was attenuated significantly until 20 minutes after hyperoxia ended in both groups compared with the PBS group (P < 0.05). In the BQ-123 group, the intravitreous injection of BQ-123 caused less reduction of blood velocity and RBF during hyperoxia compared with that in the PBS group, whereas the RBF immediately returned to baseline after hyperoxia. D-NAME and 7-NI did not affect RBF in response to hyperoxia.. The current results indicate that NO contributes to RBF recovery after hyperoxia, probably through the action of endothelial NOS via the ETB receptor in the vascular endothelium of the retinal arterioles, suggesting that the RBF response to hyperoxia may be used to evaluate the endothelial function of the retinal arterioles.

Topics: Animals; Antihypertensive Agents; Blood Flow Velocity; Blood Pressure; Cats; Enzyme Inhibitors; Female; Heart Rate; Hydrogen-Ion Concentration; Hyperoxia; Indazoles; Injections; Laser-Doppler Flowmetry; Male; NG-Nitroarginine Methyl Ester; Nitric Oxide; Oligopeptides; Oxygen; Partial Pressure; Peptides, Cyclic; Piperidines; Regional Blood Flow; Retinal Vessels; Vitreous Body

The ability of endothelins 1 and 3 (ET-1 and ET-3) to reduce neuronal norepinephrine release through ETB receptor activation involving nitric oxide (NO) pathways in the rat anterior hypothalamus region (AHR) was previously reported. In the present work, we studied the effects of ET-1 and -3 on tyrosine hydroxylase (TH) activity and the possible involvement of NO pathways. Results showed that ET-1 and -3 (10 nM) diminished TH activity in AHR and this effect was blocked by a selective ETB receptor antagonist (100 nM BQ-788), but not by a ET(A) receptor antagonist (BQ-610). To confirm these results, 1 microM IRL-1620 (ET(B) agonist) reduced TH activity whereas 300 nM sarafotoxin S6b falled to modify it. N(omega)-Nitro-L-arginine methyl ester (10 microM), 7-nitroindazole (10 microM), 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-ona (10 microM), KT5823 (2 microM), inhibitors of nitric oxide synthase, neuronal nitric oxide synthase, NO-sensitive-guanylyl cyclase, and protein kinase G, respectively, did not modify the reduction of TH activity produced by ETs. In addition, both 100 microM sodium nitroprusside and 50 microM 8-bromoguanosine-3',5'-cyclic monophosphate (NO donor and guanosine-3',5'-cyclic monophosphate analog, respectively) diminished TH activity. Present results showed that ET-1 and ET-3 diminished TH activity through the activation of ET(B) receptors involving the NO/guanosine-3',5'-cyclic monophosphate/protein kinase G pathway. Taken jointly present and previous results it can be concluded that both ETs play an important role as modulators of norepinephrine neurotransmission in the rat AHR.

Topics: Animals; Carbazoles; Cyclic GMP; Endothelin A Receptor Antagonists; Endothelin B Receptor Antagonists; Endothelin-1; Endothelin-3; Hypothalamus, Anterior; Indazoles; Indoles; Male; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitric Oxide Synthase Type I; Nitroprusside; Oligopeptides; Oxadiazoles; Piperidines; Quinoxalines; Rats; Suramin; Tyrosine 3-Monooxygenase

Traumatic brain injury (TBI) involves direct mechanical damage, which may be aggravated by secondary insults such as ischemia. We utilized an in vitro model of stretch-induced injury to investigate the effects of mechanical and combined mechanical/ischemic insults to cultured mouse cortical cells. Stretch injury alone caused significant neuronal loss and increased uptake of the dye, propidium iodide, suggesting cellular membrane damage to both glia and neurons. Exposure of cultures to ischemic conditions for 24h, or a combination of stretch and 24h of ischemia, caused greater neuronal loss compared to stretch injury alone. Next, we tested the neuroprotective effects of superoxide dismutase (SOD), and the nitric oxide (NO) synthase inhibitors 7-nitroindazole (7-NINA) and lubeluzole. In general, these agents decreased neuronal loss following stretch injury alone, but were relatively ineffective against the combined injury paradigm. A combination of SOD with 7-NINA or lubeluzole offered no additional protection than single drug treatment against stretch alone or combined injury. These results suggest that the effects of primary mechanical damage and secondary ischemia to cortical neurons are cumulative, and drugs that scavenge superoxide or reduce NO production may not be effective for treating the secondary ischemia that often accompanies TBI.

Topics: Animals; Brain Ischemia; Cell Count; Cell Survival; Cells, Cultured; Cerebral Cortex; Enzyme Inhibitors; Immunohistochemistry; Indazoles; Mice; Mitogen-Activated Protein Kinase 1; Neurons; Neuroprotective Agents; Nitric Oxide Synthase Type I; Physical Stimulation; Piperidines; Stress, Mechanical; Superoxide Dismutase; Thiazoles

Responding of rats was maintained under a 120-response fixed ratio (FR) schedule of food delivery, and animals received individual and combined injections of N-methyl-D-aspartic acid (NMDA), phencyclidine hydrochloride, (+)-MK-801 hydrogen maleate (MK-801), (+/-)-2-amino-5-phosphonopentanoic acid (AP5), 7-chlorokynurenic acid (7CK), ifenprodil tartrate, N(G)-nitro-L-arginine methyl ester hydorchloride (L-NAME), 7-nitroindazole, aminoguanidine hemisulfate, L-arginine, molsidomine, sodium nitroprusside, and 8-(diethylamino)octyl 3,4,5-trimethoxybenzoate hydrochloride (TMB-8). Behavioral suppression after NMDA was completely and dose-dependently reversed by MK-801, phencyclidine, AP5, and aminoguanidine; partially and dose-dependently attenuated by molsidomine, ifenprodil, and 7CK; and not attenuated at all by L-NAME, 7-nitroindazole, or TMB-8. These findings suggested that behavioral suppression after NMDA was associated with nitric oxide from the inducible synthase. In a second series of experiments, comparable behavioral suppression by 0.1 mg/kg MK-801, but not 3 mg/kg phencyclidine, was attenuated by nitroprusside, molsidomine, and L-arginine, suggesting that suppressions from MK-801 and phencyclidine were mediated by different final common pathways, and that behavioral suppression from MK-801, but not phencyclidine, may be associated with Ca(2+)-dependent nitric oxide.

Topics: 2-Amino-5-phosphonovalerate; Animals; Arginine; Conditioning, Operant; Dizocilpine Maleate; Dose-Response Relationship, Drug; Drug Combinations; Drug Interactions; Gallic Acid; Guanidines; Indazoles; Injections, Intraperitoneal; Kynurenic Acid; Molsidomine; N-Methylaspartate; NG-Nitroarginine Methyl Ester; Nitric Oxide Donors; Nitric Oxide Synthase; Nitric Oxide Synthase Type II; Nitroprusside; Phencyclidine; Piperidines; Rats; Rats, Sprague-Dawley; Receptors, N-Methyl-D-Aspartate

We previously reported that endothelin (ET) 3 inhibited presynaptically the dog stellate ganglionic transmission. Here, we report the investigation of the possible involvement of nitric oxide pathway in the endothelin-induced inhibition of the ganglionic transmission. The amount of acetylcholine released by preganglionic stimulation for 10 min was concentration-dependently inhibited after exposure to ET-3 (10(-9)-10(-6) M) or IRL-1620, endothelin ET(B) receptor agonist (10(-8)-10(-5) M). The inhibition was antagonized by pretreatment with a nonselective endothelin receptors antagonist (bosentan) and an ET(B) receptor antagonist (BQ-788) or a neuronal nitric oxide synthase inhibitor, 3-bromo-7-nitroindazole, but was not inhibited by a selective ET(A) receptor antagonist, BQ-123. The reduction induced by ET-3 was also antagonized by treatment with a selective inhibitor of soluble guanylyl cyclase, 1H-[1,2, 4]oxadiazolo[4,3-a]quinoxalin-1-one. In addition, similar reductions were also mimicked by exposure to cGMP analog, 8-bromoguanosine-3, 5-cyclic monophosphate and nitric oxide donor, S-nitroso-N-acetylpenicillamine. Exposure to ET-3 or IRL-1620 for a 30-min period increased the levels of total nitric oxide (NO), nitrite plus nitrate NO(x) concentration in the incubation medium, with the increase in NO(x) also being antagonized by BQ-788 at the same concentration. The ET-3-induced increase in NO(x) was antagonized by treatment with the same concentration of 3-bromo-7-nitroindazole or a selective inhibitor of receptor-mediated Ca(2+) entry, 1-[b-[3-(4-methoxyphenyl) propoxy]-4-methoxyphenethyl]-1H-imidazole (10(-5) M), and with a calmodulin antagonist, N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide. These results indicate that ET(B) receptor activation inhibits the sympathetic ganglionic transmission via reducing acetylcholine release from presynaptic nerve terminals, although this inhibition also seems to involve the ET(B) receptor-operated Ca(2+)-calmodulin-dependent activation of endogenous nitric oxide production.

Topics: 8-Bromo Cyclic Adenosine Monophosphate; Acetylcholine; Animals; Antihypertensive Agents; Dogs; Endothelin Receptor Antagonists; Enzyme Inhibitors; Female; In Vitro Techniques; Indazoles; Male; Nitric Oxide; Nitric Oxide Synthase; Nitric Oxide Synthase Type I; Oligopeptides; Oxadiazoles; Piperidines; Quinoxalines; Receptor, Endothelin A; Receptor, Endothelin B; Receptors, Endothelin; Stellate Ganglion; Sulfonamides; Synapses; Synaptic Transmission

We examined the effects of sarafotoxin 6c (S6c), an endothelin-B (ET(B)) receptor agonist, on adrenal catecholamine secretion in response to cholinergic stimuli in pentobarbital sodium-anesthetized dogs. Drugs were administered intra-arterially into the adrenal gland through the phrenicoabdominal artery. Infusion of S6c attenuated increases in adrenal catecholamine output induced by splanchnic nerve stimulation. The inhibitory effect of S6c on the catecholamine secretion response was suppressed with a selective ET(B) receptor antagonist N-cis 2, 6-dimethylpiperidinocarbonyl-L-gamma-methylleucyl-D-1-methoxycarbonyl tryptophanyl-D-norleucine (BQ-788), a nitric oxide synthase (NOS) inhibitor N(omega)-nitro-L-arginine methyl ester, and a neuronal NOS inhibitor 7-nitroindazole monosodium salt (7-NINA). Similar results were obtained with the catecholamine secretion response induced by injection of ACh. 7-NINA alone did not affect these catecholamine secretion responses. These results suggest that ET(B) receptors play an inhibitory role in adrenal catecholamine secretion by activating neuronal NOS, whereas neuronal NOS is unlikely to be involved in regulation of adrenal catecholamine secretion in the absence of simultaneous ET(B) receptor stimulation.

Topics: Acetylcholine; Adrenal Glands; Animals; Dogs; Electric Stimulation; Endothelin Receptor Antagonists; Enzyme Inhibitors; Epinephrine; Female; Indazoles; Male; NG-Nitroarginine Methyl Ester; Nitric Oxide; Norepinephrine; Oligopeptides; Piperidines; Receptor, Endothelin B; Receptors, Endothelin; Splanchnic Nerves; Viper Venoms

Glutamate stimulation of N-methyl-D-aspartate (NMDA) receptors results in release of nitric oxide which may mediate the effects of NMDA receptor stimulation and/or may result in feedback inhibition of the presynaptic neuron. Results of a previous study showed that nitric oxide synthase (NOS) inhibitors blocked dizocilpine-induced behavior in mice. In the present study, NOS inhibitors were tested in combination with phencyclidine (PCP), a drug which typically dose-dependently disrupts prepulse inhibition of the acoustic startle response in rats. Alone, NOS inhibitors and promoters do not affect prepulse inhibition; however, when tested in combination with PCP, the NOS inhibitors, L-NOARG, 7-nitroindazole and arcaine--but not the NR2B-selective polyamine site NMDA antagonist, eliprodil--attenuated PCP-induced disruption of prepulse inhibition of the acoustic startle response. These effects are similar to those produced by many atypical antipsychotics and suggests that this class of drugs should be investigated further for their potential utility as antipsychotics and as treatments for PCP abuse.

Topics: Acoustic Stimulation; Animals; Biguanides; Biogenic Polyamines; Enzyme Inhibitors; Excitatory Amino Acid Antagonists; Indazoles; Inhibition, Psychological; Male; Nitric Oxide Synthase; Nitroarginine; Phencyclidine; Piperidines; Rats; Rats, Sprague-Dawley; Receptors, N-Methyl-D-Aspartate; Reflex, Startle

To evaluate the role played by nitric oxide in global cerebral ischaemia we examined the effects of 7-nitroindazole and a sodium salt of 7-nitroindazole (inhibitors of neuronal nitric oxide (NO) synthase) and NG-nitro-L-arginine methyl ester (a more general inhibitor of NO synthase) in the gerbil model of cerebral ischaemia. Four experiments were carried out. In the first experiment, animals were either sham-operated, subjected to 5 min bilateral carotid occlusion (BCAO) or administered 7-nitroindazole or NG-nitro-L-arginine methyl ester immediately after occlusion followed by three further doses at 3, 6 and 24 h post-occlusion. In the second experiment, we examined the effects of a sodium salt of 7-nitroindazole, which is more soluble than 7-nitroindazole, using the same protocol. In the third experiment, the effects of the sodium salt of 7-nitroindazole administered at 10 mg/kg at 0, 3, 6, 24, 27, 30, 33, 52, 55, 72, 75 and 78 h post-occlusion or at 0.05 mg/h for 72 h via mini-pumps were evaluated. In separate experiments, we examined the effects of three reference compounds dizocilpine (MK-801), 2, 3-dihydroxy-6-nitro-7-sulphamoyl-benz(F)-quinoxaline (NBQX) and eliprodil using the same model. Extensive neuronal death was observed in the CA1 layer of the hippocampus in 5 min bilateral carotid occluded animals 5 days after surgery. Both 7-nitroindazole and NG-nitro-L-arginine methyl ester provided significant neuroprotection (P < 0.01) against this neuronal death. The sodium salt of 7-nitroindazole showed no protection when administered up to 12 times post-occlusion, but did provide significant (P < 0.01) neuroprotection when administered via mini-pump. The neuroprotection was similar to that provided by MK-801 and eliprodil, but not as good as that observed with NBQX. These results indicate that nitric oxide plays a role in ischaemic cell death and that selective neuronal nitric oxide synthase inhibitors can protect against ischaemic brain damage.

Topics: Animals; Brain Ischemia; Disease Models, Animal; Dizocilpine Maleate; Enzyme Inhibitors; Gerbillinae; Indazoles; Male; Neuroprotective Agents; NG-Nitroarginine Methyl Ester; Nitric Oxide Synthase; Piperidines; Quinoxalines