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Objective: The SLIT and NTRK‐like 1 (SLITRK1) gene mutation and striatal cholinergic interneurons (ChIs) loss are associated with Tourette syndrome (TS). ChIs comprise only 1 to 2% of striatal neurons but project widely throughout the stratum to impact various striatal neurotransmission, including TS‐related dopaminergic transmission. Here, we link striatal Slitrk1, ChI function, and dopaminergic transmission and their associations with TS‐like tic behaviors. Methods: Slitrk1‐KD mice were induced by bilaterally injecting Slitrk1 siRNA into their dorsal striatum. Control mice received scrambled siRNA injection. Their TS‐like tic behaviors, prepulse inhibition, sensory‐motor function and dopamine‐related behaviors were compared. We also compared dopamine and ACh levels in microdialysates, Slitrk protein and dopamine transporter levels, and numbers of Slitrk‐positive ChIs and activated ChIs in the striatum between two mouse groups, and electrophysiological properties between Slitrk‐positive and Slitrk‐negative striatal ChIs. Results: Slitrk1‐KD mice exhibit TS‐like haloperidol‐sensitive stereotypic tic behaviors, impaired prepulse inhibition, and delayed sensorimotor response compared with the control group. These TS‐like characteristics correlate with lower striatal Slitrk1 protein levels, fewer Slitrk1‐containing ChIs, and fewer activated ChIs in Slitrk1‐KD mice. Based on their electrophysiological properties, Slitrk1‐negative ChIs are less excitable than Slitrk1‐positive ChIs. Slitrk1‐KD mice have lower evoked acetylcholine and dopamine levels, higher tonic dopamine levels, and downregulated dopamine transporters in the striatum, increased apomorphine‐induced climbing behaviors, and impaired methamphetamine‐induced hyperlocomotion compared with controls. Interpretation: Slitrk1 is pivotal in maintaining striatal ChIs activity and subsequent dopaminergic transmission for normal motor functioning. Furthermore, conditional striatal Slitrk1‐KD mice may serve as a translational modality with aspects of TS phenomenology. ANN NEUROL 2024;95:174–189 [ABSTRACT FROM AUTHOR]

Previous studies have shown that systemic administration of 6'-hydroxy-2',4'-dimethoxychalcone (flavokawin B, FKB) exerts significant peripheral and central antinociceptive effects in laboratory animals. However, the mechanisms underlying these peripheral and central antinociceptive effects have yet to be elucidated. Therefore, the objective of the present study was to evaluate the participation of nitric oxide (NO)/cyclic guanosine monophosphate (cGMP)/potassium (K+) channels pathway in the peripheral antinociception induced by FKB. It was demonstrated that intraplantar (i.pl.) administration of FKB (150, 250, 375 and 500 µg/paw) resulted in dose-dependent peripheral antinociception against mechanical hyperalgesia in carrageenan-induced hyperalgesia test model in rats. The possibility of FKB having either a central or a systemic effect was excluded since administration of FKB into the right paw did not elicit antinociception in the contralateral paw. Furthermore, peripheral antinociception induced by FKB (500 µg/paw) was significantly reduced when L-arginine (25 µg/paw, i.pl.), Oxadiazolo[4,3-a]quinoxalin-1-one (ODQ; 50 µg/paw, i.pl.), glibenclamide (300 µg/paw, i.pl.), tetraethylammonium (300 µg/paw, i.pl.) and charybdotoxin (3 µg/paw, i.pl.) were injected before treatment. Taken together, our present data suggest that FKB elicits peripheral antinociception when assessed in the mechanical hyperalgesia induced by carrageenan. In addition, it was also demonstrated that this effect was mediated through interaction of the NO/cGMP/K+ channels signaling pathway.

The use of opioids in pain management is hampered by the emergence of analgesic tolerance, which leads to increased dosing and side effects, both of which have contributed to the opioid epidemic. One promising potential approach to limit opioid analgesic tolerance is activating the endocannabinoid system in the CNS, via activation of CB1 receptors in the descending pain inhibitory pathway. In this review, we first discuss preclinical and clinical evidence revealing the potential of pharmacological activation of CB1 receptors in modulating opioid tolerance, including activation by phytocannabinoids, synthetic CB1 receptor agonists, endocannabinoid degradation enzyme inhibitors, and recently discovered positive allosteric modulators of CB1 receptors. On the other hand, as non‐pharmacological pain relief is advocated by the US‐NIH to combat the opioid epidemic, we also discuss contributions of peripheral neuromodulation, involving the electrostimulation of peripheral nerves, in addressing chronic pain and opioid tolerance. The involvement of supraspinal endocannabinoid systems in peripheral neuromodulation‐induced analgesia is also discussed. LINKED ARTICLES: This article is part of a themed issue on Advances in Opioid Pharmacology at the Time of the Opioid Epidemic. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v180.7/issuetoc [ABSTRACT FROM AUTHOR]

A sensitive and accurate high performance liquid chromatography with ultraviolet/visible light detection (HPLC-UV/VIS) method for the quantification of 2,6-bis-(4-hydroxy-3-methoxybenzylidene)-cyclohexanone (BHMC) in rat plasma was developed and validated. BHMC and the internal standard, harmaline, were extracted from plasma samples by a simple liquid–liquid extraction using 95% ethyl acetate and 5% methanol. Plasma concentration of BHMC and internal standard were analyzed by reversed phase chromatography using a C18 column (150 × 4.6 mm I.D., particle size 5 µm) and elution with a gradient mobile phase of water and methanol at a flow rate of 1.0 mL/min. Detection of BHMC and internal standard was done at a wavelength of 380 nm. The limit of quantification was 0.02 µg/mL. The calibration curves was linear (R2 > 0.999) over the concentration range of 0.02–2.5 µg/mL. Intra- and inter-day precision were less than 2% coefficient of variation. The validated method was then applied to a pharmacokinetic study in rats by intravenous administration of BHMC at a single dose of 10 mg/kg. Pharmacokinetic parameters such as half-life, maximum plasma concentration, volume of distribution, clearance and elimination rate constant for BHMC were calculated.

Ethanol has been shown to suppress essential tremor (ET) in patients at low-to-moderate doses, but its mechanism(s) of action remain unknown. One of the ET hypotheses attributes the ET tremorgenesis to the over-activated firing of inferior olivary neurons, causing synchronic rhythmic firings of cerebellar Purkinje cells. Purkinje cells, however, also receive excitatory inputs from granule cells where the α6 subunit-containing GABAA receptors (α6GABAARs) are abundantly expressed. Since ethanol is a positive allosteric modulator (PAM) of α6GABAARs, such action may mediate its anti-tremor effect. Employing the harmaline-induced ET model in male ICR mice, we evaluated the possible anti-tremor effects of ethanol and α6GABAAR-selective pyrazoloquinolinone PAMs. The burrowing activity, an indicator of well-being in rodents, was measured concurrently. Ethanol significantly and dose-dependently attenuated action tremor at non-sedative doses (0.4-2.4 g/kg, i.p.). Propranolol and α6GABAAR-selective pyrazoloquinolinones also significantly suppressed tremor activity. Neither ethanol nor propranolol, but only pyrazoloquinolinones, restored burrowing activity in harmaline-treated mice. Importantly, intra-cerebellar micro-injection of furosemide (an α6GABAAR antagonist) had a trend of blocking the effect of pyrazoloquinolinone Compound 6 or ethanol on harmaline-induced tremor. In addition, the anti-tremor effects of Compound 6 and ethanol were synergistic. These results suggest that low doses of ethanol and α6GABAAR-selective PAMs can attenuate action tremor, at least partially by modulating cerebellar α6GABAARs. Thus, α6GABAARs are potential therapeutic targets for ET, and α6GABAAR-selective PAMs may be a potential mono- or add-on therapy. [ABSTRACT FROM AUTHOR]

The antinociceptive effects produced by intraperitoneal administration of a novel synthetic chalcone, 3-(2,3-dimethoxyphenyl)-1-(5-methylfuran-2-yl)prop-2-en-1-one (DMFP), were investigated in several mouse models of induced nociception. The administration of DMFP (0.1, 0.5, 1.0 and 5.0 mg/kg) produced significant attenuation on the acetic acid-induced abdominal-writhing test. It also produced a significant increase in response latency time in the hot-plate test and a marked reduction in time spent licking the injected paw in both phases of the formalin-induced paw-licking test. In addition, it was also demonstrated that DMFP exhibited significant inhibition of the neurogenic nociceptive response induced by intraplantar injections of capsaicin and glutamate. Moreover, the antinociceptive effect of DMFP in the acetic acid-induced abdominal-writhing test and the hot-plate test was not antagonized by pretreatment with a non-selective opioid receptor antagonist, naloxone. Finally, DMFP did not show any toxic effects and/or mortality in a study of acute toxicity and did not interfere with motor coordination during the Rota-rod test. Our present results show that DMFP exhibits both peripheral and central antinociceptive effects. It was suggested that its peripheral antinociceptive activity is associated with attenuated production and/or release of NO and various pro-inflammatory mediators, while central antinociceptive activity seems to be unrelated to the opioidergic system, but could involve, at least in part, an interaction with the inhibition of capsaicin-sensitive fibers and the glutamatergic system.

Neurons containing neuropeptide S (NPS) and orexins are activated during stress. Previously, we reported that orexins released during stress, via orexin OX1 receptors (OX1 Rs), contribute to the reinstatement of cocaine seeking through endocannabinoid/CB1 receptor (CB1 R)-mediated dopaminergic disinhibition in the ventral tegmental area (VTA). Here, we further demonstrated that NPS released during stress is an up-stream activator of this orexin-endocannabinoid cascade in the VTA, leading to the reinstatement of cocaine seeking. Mice were trained to acquire cocaine conditioned place preference (CPP) by context-pairing cocaine injections followed by the extinction training with context-pairing saline injections. Interestingly, the extinguished cocaine CPP in mice was significantly reinstated by intracerebroventricular injection (i.c.v.) of NPS (1 nmol) in a manner prevented by intraperitoneal injection (i.p.) of SHA68 (50 mg/kg), an NPS receptor antagonist. This NPS-induced cocaine reinstatement was prevented by either i.p. or intra-VTA microinjection (i.vta.) of SB-334867 (15 mg/kg, i.p. or 15 nmol, i.vta.) and AM 251 (1.1 mg/kg, i.p. or 30 nmol, i.vta.), antagonists of OX1 Rs and CB1 Rs, respectively. Besides, NPS (1 nmol, i.c.v.) increased the number of c-Fos-containing orexin neurons in the lateral hypothalamus (LH) and increased orexin-A level in the VTA. The latter effect was blocked by SHA68. Furthermore, a 30-min restraint stress in mice reinstated extinguished cocaine CPP and was prevented by SHA68. These results suggest that NPS is released upon stress and subsequently activates LH orexin neurons to release orexins in the VTA. The released orexins then reinstate extinguished cocaine CPP via an OX1 R- and endocannabinoid-CB1 R-mediated signaling in the VTA. [ABSTRACT FROM AUTHOR]

Introduction: Clinacanthus nutans (Burm. f.) Lindau, a shrub found in South East Asia, particularly in Malaysia, Thailand, and Indonesia has many potential medicinal uses. It is used as a traditional herbal medicine for treating many diseases including skin rashes. Skin rash often appear in an allergic reaction. Recently, we have shown that C. nutans aqueous extract has the ability to alleviate ovalbumin-induced active systemic anaphylaxis rats from anaphylaxis – the acute form of allergy. This present study is aimed at comparing the ability of ethanolic and aqueous extracts of C. nutans to suppress IgE-mast cell degranulation. Materials and Methods: IgE-presensitized rat basophilic leukemic (RBL-2H3) cells pretreated with C. nutans ethanolic (100% ethanolic, 70% and 50% aqueous ethanolic) or 100% aqueous extracts were challenged with dinitrophenyl-bovine serum albumin to analyze the release of early and late-phase pro-inflammatory mediators. Results: We found that at concentrations of 5 mg/ml and above, C. nutans aqueous extract was able to suppress the levels of β-hexosaminidase and histamine while suppression was not seen in ethanolic extracts pretreated RBL-2H3 cells.Conclusion: Hence, we proposed that C. nutans aqueous extract is more active compared to the ethanolic extracts in suppressing the mediators of IgE-mast cell degranulation. [ABSTRACT FROM AUTHOR]