Fentanyl Analogs Exert Antinociceptive Effects via Sodium Channel Blockade in Mice.

The formalin test is one approach to studying acute pain in rodents. Similar to formalin, injection with glutamate and veratrine can also produce a nociceptive response. This study investigated whether opioid-related compounds could suppress glutamate- and veratrine-induced nociceptive responses in mice at the same dose. The administration of morphine (3 mg/kg), hydromorphone (0.4 mg/kg), or fentanyl (0.03 mg/kg) suppressed glutamate-induced nociceptive response, but not veratrine-induced nociceptive response at the same doses. However, high doses of morphine (10 mg/kg), hydromorphone (2 mg/kg), or fentanyl (0.1 mg/kg) produced a significant reduction in the veratrine-induced nociceptive response. These results indicate that high doses are required when using morphine, hydromorphone, or fentanyl for sodium channel-related neuropathic pain, such as ectopic activity. As a result, concerns have arisen about overdose and abuse if the dose of opioids is steadily increased to relieve pain. In contrast, trimebutine (100 mg/kg) and fentanyl analog isobutyrylfentanyl (iBF; 0.1 mg/kg) suppressed both glutamate- and veratrine-induced nociceptive response. Furthermore, nor-isobutyrylfentanyl (nor-iBF; 1 mg/kg), which is a metabolite of iBF, suppressed veratrine-induced nociceptive response. Besides, the optimal antinociceptive dose of iBF, unlike fentanyl, only slightly increased locomotor activity and did not slow gastrointestinal transit. Cancer pain is a complex condition driven by inflammatory, neuropathic, and cancer-specific mechanisms. Thus, iBF may have the potential to be a superior analgesic than fentanyl.

Identification and pharmacological characterization of the voltage-gated potassium channel Shab in diamondback moth, Plutella xylostella.

BACKGROUND: Voltage-gated potassium channel Kv2 is the primarily delayed rectifier in insect nerves and muscles involved in several crucial biological processes, including action potential regulation, photoreceptor performance, and larval locomotor. It is a potential molecular target for developing a novel pesticide for mosquitos. However, there are few studies on the Kv2 channel in agricultural pests. RESULTS: The only α-subunit gene of the Kv2 channel in Plutella xylostella (L.), PxShab, was cloned, and its expression profile was analyzed. The relative expression level of PxShab was highest in the pupal stage of both sexes and male adults but lowest in female adults. Meanwhile, PxShab had the highest expression in the head in both larvae and adults. Then, PxShab was stably expressed in the HEK-293 T cell line. Whole cell patch clamp recordings showed an outward current whose current-voltage relationship conformed to a typical delayed-rectifier potassium channel. 20 µM quinidine could effectively inhibit the potassium current, while the channel was insensitive to 4-AP even at 10 mM. Several potential compounds and botanical pesticides were assessed, and carvedilol (IC50  = 0.53 µM) and veratrine (IC50  = 2.22 µM) had a good inhibitory effect on the channel. CONCLUSION: This study revealed the pharmacological properties of PxShab and screened out several high potency inhibitors, which laid the foundation for further functional research of PxShab and provides new insight into designing novel insecticides. © 2022 Society of Chemical Industry.

Sodium channel-directed alkaloids synergize the mosquitocidal and neurophysiological effects of natural pyrethrins.

We explored the potential of two sodium channel activators, veratrine and aconitine, as both insecticides and synergists of natural pyrethrins (NP) on Aedes aegypti adults and larvae. Aconitine was more toxic than veratrine, with an LD50 of 157 ng/mg compared to 376 ng/mg, on the pyrethroid-susceptible Orlando strain, but only aconitine showed significant resistance in the pyrethroid-resistant Puerto Rico strain (RR = 14.6 in topical application and 8.8 in larval bioassay). When applied in mixtures with piperonyl butoxide (PBO) and NP, large synergism values were obtained on the Orlando strain. Aconitine + PBO mixture synergized NP 21.8-fold via topical adult application and 10.2-fold in larval bioassays, whereas veratrine + PBO synergized NP 5.3-fold via topical application and 30.5-fold in larval bioassays. Less synergism of NP was observed on the resistant Puerto Rico strain, with acontine + PBO synergizing NP only 4.1-fold in topical application (8-fold in larval bioassays) and veratrine + PBO synergizing NP 9.5-fold in topical application (13.3-fold in larval bioassays). When alkaloids were applied directly to the mosquito larval nervous system, veratrine was nearly equipotent on both strains, while aconitine was less active on pyrethroid-resistant nerve preparations (no block at 10 µM compared to block at 1 µM on the susceptible strain). The nerve blocking effect of NP was significantly synergized by both compounds on the pyrethroid-susceptible strain by about 10-fold, however only veratrine synergized NP block on the pyrethroid-resistant strain, also showing 10-fold synergism). These results highlight the potential of site II sodium channel activators as insecticides and their ability to synergize pyrethroids, which may extend the commercial lifetime of these chemistries so essential to public health vector control.

Evaluation of the antinociceptive activities of several sodium channel blockers using veratrine test in mice.

An important role of voltage-gated sodium channels (VGSCs) in many different pain states has been established in animal models and humans wherein sodium channel blockers partially ameliorate pain. However, behavioral tests for screening analgesics that exhibit pharmacologic action by acting on VGSCs are rarely reported, and there are no studies on antinociception using veratrine as a nociceptive agent. The aim of the present study was to examine the amount of nociceptive behavior evoked by subcutaneous administration of veratrine into the hind paw and investigate whether veratrine can be used as a VGSC agonist to test the pharmacological properties of candidate analgesics via sodium channel blockade. We report for the first time that intraplantar injection of veratrine produced a reproducible nociceptive response in mice. Furthermore, several sodium channel blockers, namely carbamazepine, valproate, mexiletine, and the selective Nav1.7 inhibitor PF-04856264, but not flecainide or pilsicainide, reduced veratrine-induced nociception. In contrast, calcium channel blockers gabapentin and ethosuximide did not change veratrine-induced nociception. The veratrine test in mice might be a useful tool, at least in part, to evaluate the potential analgesic effect of sodium channel blockers.

Uliginosin B, a natural phloroglucinol derivative with antidepressant-like activity, increases Na+,K+-ATPase activity in mice cerebral cortex

ABSTRACT Uliginosin B, a phloroglucinol isolated from Hypericum polyanthemum Klotzsch ex Reichardt, Hypericaceae, has antidepressant-like effect in the forced swimming test in rodents and inhibits monoamines neuronal reuptake without binding to their neuronal carriers. Studies showed the involvement of Na+,K+-ATPase brain activity in depressive disorders, as well as the dependence of neuronal monoamine transport from Na+ gradient generated by Na+,K+-ATPase. This study aimed at evaluating the effect of uliginosin B on Na+,K+-ATPase activity in mice cerebral cortex and hippocampus (1 and 3 h after the last administration) as well as the influence of veratrine, a Na+ channel opener, on the antidepressant-like effect of uliginosin B. Mice were treated (p.o.) with uliginosin B single (10 mg/kg) or repeated doses (10 mg/kg/day, 3 days). Acute administration reduced the immobility in the forced swimming test and tail suspension test and increased Na+,K+-ATPase activity in cerebral cortex 1 h after treating, whereas the repeated treatment induced the antidepressant-like effect and increased the Na+,K+-ATPase activity at both times evaluated. None treatment affected the hippocampus enzyme activity. Veratrine pretreatment prevented uliginosin B antidepressant-like effect in the forced swimming test, suggesting the involvement of Na+ balance regulation on this effect. Altogether, these data indicate that uliginosin B reduces the monoamine uptake by altering Na+ gradient.

Neural control of submucosal gland and apical membrane secretions in airways.

The mechanisms that lay behind the low-level secretions from airway submucosal glands and the surface epithelium in the absence of external innervation have been investigated in small areas (1.0-1.5 cm(2)) of mucosa from sheep tracheas, freshly collected from a local abattoir. Glandular secretion was measured by an optical method while short circuit current was used as a measure of surface secretion. Activation of neurones in the intrinsic nerve net by veratrine alkaloids caused an immediate increase in both glandular secretion and short circuit current, both effects being blocked by the addition of tetrodotoxin. However, agents known to be acting directly on the glands, such as muscarinic agonists (e.g., carbachol) or adenylate cyclase activators (e.g., forskolin) were not influenced by tetrodotoxin. The toxin alone had no discernable effect on the low-level basal secretion shown by unstimulated glands. Calu-3 cell monolayers, generally agreed to be a surrogate for the secretory cells of submucosal glands, showed no sensitivity to veratrine alkaloids, strengthening the view that the veratrine-like drugs acted exclusively on the intrinsic nerve net. The data are discussed in relation way in which transplanted lungs can maintain mucociliary clearance and hence a sterile environment in the absence of external innervation, as in transplanted lungs.

A synthetic bioisoster of trimethadione and phenytoin elicits anticonvulsant effect, protects the brain oxidative damage produced by seizures and exerts antidepressant action in mice.

Epilepsy is recognized as one of the most common and serious neurological disorder affecting 1-2% of the world׳s population. The present study demonstrates that systemic administration of 3-butyl-5,5-dimethyl-1,2,3-oxathiazolidine-4-one-2,2-dioxide (DIOXIDE), a synthetic compound bioisoster of trimethadione and phenytoin (classical anticonvulsants), elicits a dose dependent anticonvulsant response in mice submitted to the subcutaneous pentylenetetrazole seizure test (scPTZ). Among various factors supposed to play role in epilepsy, oxidative stress and reactive species have strongly emerged. The protection exerted by DIOXIDE over the extent of brain oxidative damage produced by PTZ was determined, by measuring the levels of lipid peroxidation and reduced glutathione and the activity of Na(+)/K(+)-ATPase. Psychiatric disorders represent frequent comorbidities in persons with epilepsy. In this report, the potential anxiolytic and antidepressant activities of DIOXIDE were evaluated in several widely used models for assessing anxiolytic and antidepressant activities in rodents. Although DIOXIDE did not evidence anxiolytic activity at the doses tested, it revealed a significant antidepressant-like effect. Preliminary studies of its mechanism of action, by means of its capacity to act via the GABAA receptor (using the [(3)H]flunitrazepam binding assay in vitro and the picrotoxin test in vivo) and the Na(+) channel (using the alkaloid veratrine, a voltage-Na(+) channel agonist) demonstrated that the anticonvulsant effect is not likely related to the GABAergic pathway and the antidepressant-like effect could be due to its Na(+) channel blocking properties. The results for DIOXIDE suggested it as a new anticonvulsant-antioxidant and antidepressant compound that deserves further development.

Cytotoxic effect of veratrine hydrochloride on HepG2 cells and its possible mechanism / 中国药理学与毒理学杂志

OBJECTIVE Tostudythehepatotoxicityofveratrinehydrochloride(VH)anditsmecha-nismoninductionofapoptosisinvitro.METHODS HepG2cellswereexposedtoVH0.1-0.6g·L-1 for 24 h,cell viability was examined by CCK-8 assay,and the morphologic changes in HepG2 cells were quantified.After the treatment with VH 0.1 -0.5 g·L-1 for 24 h,cell membrane injury was examined by detecting the release rate of lactate dehydrogenase (LDH).The effect on reactive oxygen species (ROS),mitochondrial membrane potential and apoptosis was detected by flow cytometry.The mRNA expression of p53,Bax,cytochrome c,caspase 9,caspase 3 was evaluated by real-time PCR. RESULTS HepG2cellviabilitywassignificantlyreducedfollowingexposuretoVH0.1-0.5g·L-1. The IC50 value was 0.4 g·L-1 .The 95%confidence limit was 0.2558-0.6965 g·L-1 .The LDH release rate,ROS and apoptosis rate of HepG2 cells were significantly increased after exposure to VH 0.1 -0.5 g·L-1 for 24 h (P<0.05,P<0.01 ),and the mitochondrial membrane potential markedly declined (P<0.05,P<0.01 ).The expression of p53,Bax,cytochrome c,caspase 9 and caspase 3 was increased(P<0.05,P<0.01).CONCLUSION VHhascytotoxicpotential.Damagetocell me mbrane and mitochondria and initiation of apoptosis-related genes of caspase 9 and caspase 3 mRNA expression may be the mechanis m of apoptosis.

The antimanic-like effect of phenytoin and carbamazepine on methylphenidate-induced hyperlocomotion: role of voltage-gated sodium channels.

The objective of this study was to verify whether phenytoin modifies methylphenidate-induced hyperlocomotion, an animal model for screening antimanic-like drugs, and also evaluate the effect of veratrine, a voltage-gated sodium channel opener, pretreatment on the effect of phenytoin in this model. Carbamazepine was used as a positive control. Methylphenidate (5 mg/kg, s.c.) increased open-field locomotion, and phenytoin (5-10 mg/kg, i.p.) and carbamazepine (20 mg/kg, i.p.) blocked this effect. Veratrine (0.4 mg/kg, s.c.) pretreatment reversed the effects of phenytoin (10 mg/kg, i.p.) and carbamazepine (20 mg/kg, i.p.). Phenytoin (1-50 mg/kg, i.p.) and carbamazepine (10-20 mg/kg i.p.) alone did not change spontaneous locomotor activity. These results indicate that voltage-gated sodium channels play an important role in antimanic-like effects of phenytoin and carbamazepine on psychostimulant-induced hyperlocomotion model.

Cytological mechanism of epileptoid activities of rats hippocampus pyramidal cells induced by low dose of veratrine / 解放军医学杂志

Objective To observe the effects of low dose of veratrine on the discharges of rat hippocampus pyramidal neurons,and to elucidate its possible cytological mechanism.Methods The discharge features of hippocampus CA1 pyramidal neurons of 14-day-aged healthy Sprague-Dawley rats induced by low dose(0.3～0.8?mol/L)of veratrine were observed by slice patch-clamp technique.Presynap- tic stimulation was given to Schaffer collaterals.Presynaptic receptor inhibitors such as 6-cyano-7-nitroquinoxaline-2,3-dione(CNQX, 5?mol/L),DL-2-amino-5-phosphonopentanoic acid(AP-5,12.5?mol/L),bicuculline(Bic,10?mol/L)and tetrodotoxin(TTX,40～80nmol/L)were used to investigate the influence on veratrine-induced epilepsy andⅠ-Ⅴcurves were plotted under these conditions.Elec- trophysiological mechanism of veratrine-induced epilepsy was elucidated on the basis of these experiments,Results After a perfusion with low dose of veratrine,the pyramidal neurons were found to discharge relatively fixed-mode slow wave epileptoid bursts accompanied with hyperpolarization of membrane potential.These epileptoid bursts were not blocked by a mixture of CNQX,AP-5 and Bic,but by low dose of TTX.After a perfusion with veratrine,Ⅰ-Ⅴrelationship tended to be nonlinear and the depolarization rectification was enhanced,which were reversed by administration of low dose of TTX.The subthreshold TTX-sensitive persistent sodium current of CA1 pyramidal cells was enhanced by veratrine in a voltage-dependent manner.Conclusion Inducing slow wave epileptoid bursts,the low dose of veratrine can remarkably change the discharge features of CA1 pyramidal neurons.Such epileptoid activities were not influenced by the synaptic receptor inhibitors,and were obviously related to the persistent sodium current.