Habenula cholinergic neurons regulate anxiety during nicotine withdrawal via nicotinic acetylcholine receptors.

Cholinergic neurons in the medial habenula (MHb) modulate anxiety during nicotine withdrawal although the molecular neuroadaptation(s) within the MHb that induce affective behaviors during nicotine cessation is largely unknown. MHb cholinergic neurons are unique in that they robustly express neuronal nicotinic acetylcholine receptors (nAChRs), although their behavioral role as autoreceptors in these neurons has not been described. To test the hypothesis that nAChR signaling in MHb cholinergic neurons could modulate anxiety, we expressed novel "gain of function" nAChR subunits selectively in MHb cholinergic neurons of adult mice.

Increased CRF signalling in a ventral tegmental area-interpeduncular nucleus-medial habenula circuit induces anxiety during nicotine withdrawal.

Increased anxiety is a prominent withdrawal symptom in abstinent smokers, yet the neuroanatomical and molecular bases underlying it are unclear. Here we show that withdrawal-induced anxiety increases activity of neurons in the interpeduncular intermediate (IPI), a subregion of the interpeduncular nucleus (IPN). IPI activation during nicotine withdrawal was mediated by increased corticotropin releasing factor (CRF) receptor-1 expression and signalling, which modulated glutamatergic input from the medial habenula (MHb).

Activation of GABAergic neurons in the interpeduncular nucleus triggers physical nicotine withdrawal symptoms.

Background: Chronic exposure to nicotine elicits physical dependence in smokers, yet the mechanism and neuroanatomical bases for withdrawal symptoms are unclear. As in humans, rodents undergo physical withdrawal symptoms after cessation from chronic nicotine characterized by increased scratching, head nods, and body shakes.

Results: Here we show that induction of physical nicotine withdrawal symptoms activates GABAergic neurons within the interpeduncular nucleus (IPN).

Dicer expression is essential for adult midbrain dopaminergic neuron maintenance and survival.

The type III RNAse, Dicer, is responsible for the processing of microRNA (miRNA) precursors into functional miRNA molecules, non-coding RNAs that bind to and target messenger RNAs for repression. Dicer expression is essential for mouse midbrain development and dopaminergic (DAergic) neuron maintenance and survival during the early post-natal period. However, the role of Dicer in adult mouse DAergic neuron maintenance and survival is unknown.

Activation of mammalian target of rapamycin mediates rat pain-related responses induced by BmK I, a sodium channel-specific modulator.

The mammalian target of rapamycin (mTOR) is known to regulate cell proliferation and growth by controlling protein translation. Recently, it has been shown that mTOR signaling pathway is involved in long-term synaptic plasticity. However, the role of mTOR under different pain conditions is less clear.

Phenotypes and peripheral mechanisms underlying inflammatory pain-related behaviors induced by BmK I, a modulator of sodium channels.

The integrated mechanisms of dynamic signaling of sodium channels involved in clinical pain are still not yet clear. In this study, a new rat inflammatory pain model was developed by using the unilateral intraplantar injection of BmK I, a receptor site 3-specific modulator of sodium channels from the venom of scorpion Buthus martensi Karsch (BmK). It was found that BmK I could induce several kinds of inflammatory pain-related behaviors including spontaneous pain companied with unique episodic paroxysms, primary thermal hypersensitivity, and mirror-image mechanical hypersensitivity with different time course of development, which could be suppressed by morphine, indomethacin, or bupivacaine to a different extent.

Activation of alpha4* nAChRs is necessary and sufficient for varenicline-induced reduction of alcohol consumption.

Recently, the smoking cessation therapeutic varenicline, a nicotinic acetylcholine receptor (nAChR) partial agonist, has been shown to reduce alcohol consumption. However, the mechanism and nAChR subtype(s) involved are unknown. Here we demonstrate that varenicline and alcohol exposure, either alone or in combination, selectively activates dopaminergic (DAergic) neurons within the posterior, but not the anterior, ventral tegmental area (VTA).

Spinal astrocyte and microglial activation contributes to rat pain-related behaviors induced by the venom of scorpion Buthus martensi Karch.

The present study investigated whether spinal astrocyte and microglia were activated in Buthus martensi Karch (BmK) venom-induced rat pain-related behaviors. The results showed that glial fibrillary acidic protein (GFAP) immunoreactivity indicative astrocyte activation in bilateral spinal cord started to increase by day 3, peaked at day 7 and gradually reversed at day 14 following intraplantar injection of BmK venom. Western blotting analysis confirmed GFAP expression was up-regulated by BmK venom.

Slow rise of intracellular Ca(2+) concentration in rat primary sensory neurons triggered by loureirin B.

In the present study, the intracellular free calcium concentration ([Ca(2+)](i)) in acutely isolated rat dorsal root ganglia (DRG) neurons modulated by loureirin B, an active component of "dragon's blood" which is a kind of Chinese herbal medicine, was determined by the means of Fura-2 based microfluorimetry. It was found that loureirin B could evoke the elevation of [Ca(2+)](i) in a dose-dependent manner. However, the elevation of [Ca(2+)](i) evoked in the calcium free solution was much smaller than that in the standard external cell solution, suggesting that most change of [Ca(2+)](i) was generated by the influx of extracellular Ca(2+), not by the activities of intracellular organelles like Ca(2+) stores and mitochondria.

Functional depletion of capsaicin-sensitive primary afferent fibers attenuates rat pain-related behaviors and paw edema induced by the venom of scorpion Buthus martensi Karch.

The role of capsaicin-sensitive primary afferent fibers in rat pain-related behaviors and paw edema induced by scorpion Buthus martensi Karch (BmK) venom was investigated in this study. It was found that functional depletion of capsaicin-sensitive primary afferent fibers with a single systemic injection of resiniferatoxin (RTX) dramatically decreased spontaneous nociceptive behaviors, prevented the development of primary mechanical and thermal hyperalgesia as well as mirror-image mechanical hyperalgesia. RTX treatment significantly attenuated BmK venom-induced c-Fos expression in all laminaes of bilateral L4-L5 lumbar spinal cord, especially in superficial laminaes.

Involvement of spinal nitric oxide (NO) in rat pain-related behaviors induced by the venom of scorpion Buthus martensi Karsch.

In the present study, we investigated the role of spinal nitric oxide (NO) in rat pain-related behaviors induced by the venom of scorpion Buthus martensi Karsch (BmK). The results showed that the number of neuronal NO synthase (nNOS) positive neurons significantly increased in superficial (I-II), deep (V-VI) dorsal horn laminae and the ventral gray laminae (VII-X), but not in the nucleus proprius (III and IV) of bilateral L4-L5 lumbar spinal cord after unilateral intraplantar injection of BmK venom from 2h to 7d. This increase on the ipsilateral side to BmK venom injection was always greater than that on the contralateral side.

Anti-nociceptive effects induced by intrathecal injection of BmK AS, a polypeptide from the venom of Chinese-scorpion Buthus martensi Karsch, in rat formalin test.

Aim Of The Study: Asian scorpion Buthus martensi Karsch (BmK) is widely used to treat neurological symptoms, especially chronic pain, in traditional Chinese medicine for thousands of years. BmK AS, a polypeptide from BmK venom, could produce peripheral potent anti-nociceptive effects in rats. In the present study, spinal anti-nociceptive effects of BmK AS were investigated in rat formalin test.

Activation of spinal ERK signaling pathway contributes to pain-related responses induced by scorpion Buthus martensi Karch venom.

It has been demonstrated that spontaneous nociceptive behaviors, cutaneous hyperalgesia and paw edema can be induced by intraplantar injection of scorpion Buthus martensi Karch (BmK) venom in rats. In the present study, activation of spinal extracellular signal-regulated kinase (ERK) signaling pathway and its contribution to pain-related responses induced by scorpion BmK venom were investigated. It was found that ERK was activated not only in the superficial layers but also in deep layers of L4-L5 spinal cord dorsal horn, which started at 2 min, peaked at 30-60 min and almost disappeared at 4h following intraplantar injection of BmK venom.

Intrathecal injection of glutamate receptor antagonists/agonist selectively attenuated rat pain-related behaviors induced by the venom of scorpion Buthus martensi Karsch.

The present study investigated the involvement of spinal glutamate receptors in the induction and maintenance of the pain-related behaviors induced by the venom of scorpion Buthus martensi Karsch (BmK). (5R,10S)-(+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]-cyclohepten-5-10-imine hydrogen maleate (MK-801; 40nmol; a non-competitive NMDA receptor antagonist), 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX; 40nmol; a non-NMDA receptor antagonist), dl-amino-3-phosphonopropionic acid (dl-AP3; 100nmol; a group I metabotropic glutamate receptor antagonist) and 4-aminopyrrolidine-2,4-dicarboxylate (APDC; 100nmol; a group II metabotropic glutamate receptor agonist) were employed. On intrathecal injection of glutamate receptor antagonists/agonist before BmK venom administration by 10min, BmK venom-induced spontaneous nociceptive responses could be suppressed by all tested agents.

Degranulation of mast cells and histamine release involved in rat pain-related behaviors and edema induced by scorpion Buthus martensi Karch venom.

In the present study, it was investigated whether the degranulation of mast cells and histamine release were involved in rat pain-related behaviors and edema induced by the venom of scorpion Buthus martensi Karch (BmK) or not. It was found that the obvious degranulation of mast cells could be triggered in rat hindpaw skin by BmK venom. The chronic degranulation of mast cells using compound 48/80 relieved the spontaneous nociceptive responses, the primary thermal and bilateral mechanical hyperalgesia and the rat paw edema, as well as partially reduced c-Fos expression in superficial layers (laminae I-II) of bilateral spinal cord induced by BmK venom.

Suppression by intrathecal BmK IT2 on rat spontaneous pain behaviors and spinal c-Fos expression induced by formalin.

The central anti-nociception of BmK IT2, a sodium channel modulator from scorpion Buthus martensi Karsh (BmK) was investigated in this study. It was found that the formalin-induced rat spontaneous flinches and spinal c-Fos expression could be significantly suppressed by intrathecal BmK IT2 pre- or post-formalin injection in a dose-dependent manner. The time course of inhibitory effect exerted by intrathecal BmK IT2 on spontaneous flinches was longer in the pre-treatment group than in post-treatment group.

Rat epileptic seizures evoked by BmK alphaIV and its possible mechanisms involved in sodium channels.

This study showed that rat unilateral intracerebroventricular injection of BmK alphaIV, a sodium channel modulator derived from scorpion Buthus martensi Karsch, induced clusters of spikes, epileptic discharges and convulsion-related behavioral changes. BmK alphaIV potently promoted the release of endogenous glutamate from rat cerebrocortical synaptosomes. In vitro examination of the effect of BmK alphaIV on intrasynaptosomal free calcium concentration [Ca(2+)](i) and sodium concentration [Na(+)](i) revealed that BmK alphaIV-evoked glutamate release from synaptosomes was associated with an increase in Ca(2+) and Na(+) influx.

Rat pain-related responses induced by experimental scorpion BmK sting.

The developmental and pharmacological characteristics of pain responses induced by the experimental scorpion BmK (Buthus martensi Karsch) sting were detailed in this study. Following the unilateral intraplantar injection of BmK venom into rat hind paw, it was found: 1) BmK venom induced an edematogenic response, spontaneous pain and pain hypersensitivity in a dose-dependent manner; 2) the paw edema and flare were induced rapidly and restricted at the injected paw for about 24-48 h; 3) the monophasic tonic spontaneous pain manifested as continuous paw flinching and lifting/licking of the injected paw and lasted for more than 2 h; 4) the detectable thermal hypersensitivity to radiant heat stimuli was just at the injected side for about 72-96 h; 5) the mechanical hypersensitivity to von Frey filaments was evoked surprisingly to be the bilateral and mirror-like for about 2-3 weeks; 6) morphine, indomethacin and bupivacaine could suppress BmK venom-induced pain responses with different intensity and time courses. The results indicated that the experimental BmK sting could evoke the prolonged paw inflammation, tonic spontaneous behaviors, unilateral thermal and bilateral mechanical hypersensitivity.

Chinese-scorpion (Buthus martensi Karsch) toxin BmK alphaIV, a novel modulator of sodium channels: from genomic organization to functional analysis.

In the present study, BmK alphaIV, a novel modulator of sodium channels, was cloned from venomous glands of the Chinese scorpion (Buthus martensi Karsch) and expressed successfully in Escherichia coli. The BmK alphaIV gene is composed of two exons separated by a 503 bp intron. The mature polypeptide contains 66 amino acids.

The binding of BmK IT2 on mammal and insect sodium channels by surface plasmon resonance assay.

The binding of BmK IT2 to insect and mammal sodium channels was investigated by surface plasmon resonance technique. The results showed that BmK IT2 could bind not only to cockroach neuronal membranes but also to rat cerebrocortical and hippocampal synaptosomes with distinct affinity. The binding of BmK IT2 could be competed significantly by BmK AS and BmK abT, but not by AaH II, BmK I and veratridine.