vofopitant and Disease-Models--Animal

Many patients with epilepsy are refractory to anticonvulsant drugs or do not tolerate side effects associated with the high doses required to fully prevent seizures. Antagonists of neurokinin-1 (NK1) receptors have the potential to reduce seizure severity, although this potential has not been fully explored in animals or humans. The present study was designed to evaluate the efficacy of the NK1-receptor antagonist, vofopitant, alone and in combination with different anticonvulsant drugs.. Studies were conducted in rats using a model of generalized seizure induced by electroshock. Drug concentrations in blood and brain were determined in parallel to distinguish pharmacodynamic from pharmacokinetic interactions.. The NK1-receptor antagonist, GR205171 (vofopitant) had no anticonvulsant efficacy by itself, but could potentiate the anticonvulsant efficacy of lamotrigine and other sodium channel blockers. However, GR205171 had no effect on the anticonvulsant potency of either valproate or gabapentin. GR205171 did not produce central nervous system (CNS) side effects at the doses tested, and it did not potentiate side effects induced by high doses of lamotrigine. The NK1-receptor inactive enantiomer of GR205171, GR226206 did not potentiate the efficacy of lamotrigine, suggesting that effects observed with GR205171 were mediated by NK1 receptors. Analysis of the dose-effect relationship for GR205171 indicated that a high (>99%) occupancy of NK1 receptors is required for effect, consistent with previous behavioral and human clinical studies with this pharmacologic class.. These results suggest that there may be benefit in adding treatment with a suitable NK1-receptor antagonist to treatment with a sodium channel blocker in patients with refractory epilepsy.

Topics: Animals; Anticonvulsants; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Synergism; Electroshock; Male; Neurokinin-1 Receptor Antagonists; Piperidines; Rats; Rats, Sprague-Dawley; Seizures; Sodium Channels; Tetrazoles

Substance P antagonists of the neurokinin-1 receptor type (NK1) have growing interest as new antidepressant therapies. It has been postulated that these drugs exert this putative therapeutic effect without direct interactions with serotonin (5-HT) neurons. In line with this assumption, previous intracerebral in vivo microdialysis experiments provided evidence that the NK1 receptor antagonists did not change basal cortical 5-HT levels. However, we found that increases in cortical 5-HT overflow caused by systemic injection of the selective serotonin reuptake inhibitor (SSRI), paroxetine was higher in freely moving (C57BL/6x129sv) NK1-/- mutants than in wild-type NK1+/+ mice. More recently, a pharmacological study has led to a similar conclusion since GR205171, a NK1 receptor antagonist, potentiated paroxetine-induced increases in cortical 5-HT dialysate following its acute systemic or intra-raphe administration to wild-type mice . In the present study, we tested whether an acute combination of SSRI and NK1 receptor antagonist could display antidepressant-like activity using the forced swimming test in Swiss mice. We found that a single systemic dose of GR205171 (10 and 30 mg/kg, i.p.) had no effect by itself. However, it selectively potentiated the antidepressant-like activity of subactive doses of two serotonergic antidepressant drugs, citalopram and paroxetine (without psychomotor stimulant activity), but not that of noradrenaline reuptake inhibitor, desipramine. In agreement with neurochemical data, the present study confirms that co-administration of a NK1 receptor antagonist with an antidepressant drug such as a SSRI may have a therapeutic potential to improve the treatment of major depressive episodes in human compared to SSRI alone.

Topics: Adrenergic Uptake Inhibitors; Analysis of Variance; Animals; Antidepressive Agents; Citalopram; Depressive Disorder; Desipramine; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Evaluation, Preclinical; Drug Synergism; Escape Reaction; Male; Mice; Neurokinin-1 Receptor Antagonists; Neurotransmitter Uptake Inhibitors; Paroxetine; Piperidines; Selective Serotonin Reuptake Inhibitors; Stress, Psychological; Swimming; Tetrazoles

We have examined the role of TRPV1 activation in disrupting the blood-brain barrier by measuring the permeability of single pial venular capillaries in anaesthetized rats. Capsaicin application to the brain surface resulted in increased permeability, maximal 2.1+/-0.12 x 10(-6) cm s(-1) (mean+/-s.e.m.) with log EC50 -4.5+/-0.10. Substance P methyl ester gave a similar response (maximal 2.0+/-0.07, n = 6, log EC50 -4.8+/-0.07), but the selective NK2 agonist, beta-Ala8-NKA(4-10) peptide, had no effect. Although CGRP decreased the permeability of venules (log EC50 10.3+/-0.11), its receptor antagonist CGRP(8-37) had no effect on the response to capsaicin. The TRPV1 antagonist capsazepine (1 mM) reduced the response to capsaicin (100 microM), from 1.78+/-0.15 to 0.63+/-0.10 (n = 4). The NK1 receptor antagonists GR205171 (100 microM) and SDZ NKT 376 (1 mM) also reduced the response to capsaicin (from 1.75+/-0.14 to 0.46+/-0.08; n = 6, and from 1.85+/-0.13 to 0.48+/-0.05; n = 5, respectively), indicating that capsaicin acts via TRPV1 in series with NK(1). Starch microspheres were used to produce transient focal ischaemia. Permeability was increased on reperfusion to a greater extent and more rapidly in vessels with diameter greater than 40 microm than those less than 15 microm. Capsazepine given intraperitoneally during ischaemia reduced the permeability increase in small venules from 5.9+/-0.3 to 2.4+/-0.1, and from 11.4+/-0.8 to 5.1+/-0.9 in large venules. In conclusion, the TRPV1 receptor is active in the brain microvasculature and has its permeability-increasing effect via substance P. It also plays a role in the immediate blood-brain barrier disruption following ischaemia-reperfusion.

Topics: Animals; Blood-Brain Barrier; Brain Ischemia; Capillaries; Capillary Permeability; Capsaicin; Disease Models, Animal; Dose-Response Relationship, Drug; Female; Male; Microspheres; Piperidines; Rats; Rats, Wistar; Receptors, Neurokinin-1; Starch; Substance P; Tetrazoles; Time Factors; TRPV Cation Channels

Investigation of the antidepressant-like actions of substance P (NK1 receptor) antagonists has been hindered by the few available compounds that bind with high affinity to the rat and mouse NK1 receptor, as these are the most commonly used preclinical species. The best available compounds for such studies are SR140333 and GR205171. However, SR140333 does not penetrate the central nervous system (CNS) after systemic administration, and GR205171 is active only at high doses, where unspecific pharmacological effects occur, so that changes in behaviour cannot be attributed to selective NK1 receptor blockade. These compounds may be substrates for P-glycoprotein (P-gp) and hence are actively excluded from the brain. The present studies used mdr1a-/- mice, a spontaneously occurring mutant that is deficient in P-gp, to examine the CNS penetration of SR140333 and GR205171. Following systemic administration of SR140333 and GR205171 (0.01-10 mg/kg i.v.), considerably higher drug concentrations were achieved in the brains of mdr1a-/- than in mdr1a+/+ mice, and this corresponded with a greater ability to inhibit NK1-agonist-induced behaviours in the mdr1a-/- mutants. Moreover, an NK1-receptor-specific inhibition of aggressive behaviour by GR205171 (10 mg/kg) could be demonstrated in mdr1a-/-, but not mdr1a+/+, mice. These findings suggest that P-gp deficient mice may have useful applications in behavioural pharmacology studies, especially when highly brain-penetrant compounds are not yet available.

Topics: Animals; ATP Binding Cassette Transporter, Subfamily B, Member 1; Blood-Brain Barrier; Brain Chemistry; Disease Models, Animal; Genes, MDR; Male; Mice; Mice, Knockout; Neurokinin-1 Receptor Antagonists; Piperidines; Quinuclidines; Stereoisomerism; Tetrazoles