High-Dose Benzodiazepines Positively Modulate GABAA Receptors via a Flumazenil-Insensitive Mechanism.

Benzodiazepines (BZDs) produce versatile pharmacological actions through positive modulation of GABAA receptors (GABAARs). A previous study has demonstrated that high concentrations of diazepam potentiate GABA currents on the α1ß2γ2 and α1ß2 GABAARs in a flumazenil-insensitive manner. In this study, the high-concentration effects of BZDs and their sensitivity to flumazenil were determined on synaptic (α1ß2γ2, α2ß2γ2, α5ß2γ2) and extra-synaptic (α4ß2δ) GABAARs using the voltage-clamp electrophysiology technique. The in vivo evaluation of flumazenil-insensitive BZD effects was conducted in mice via the loss of righting reflex (LORR) test. Diazepam induced biphasic potentiation on the α1ß2γ2, α2ß2γ2 and α5ß2γ2 GABAARs, but did not affect the α4ß2δ receptor. In contrast to the nanomolar component of potentiation, the second potentiation elicited by micromolar diazepam was insensitive to flumazenil. Midazolam, clonazepam, and lorazepam at 200 µM exhibited similar flumazenil-insensitive effects on the α1ß2γ2, α2ß2γ2 and α5ß2γ2 receptors, whereas the potentiation induced by 200 µM zolpidem or triazolam was abolished by flumazenil. Both the GABAAR antagonist pentylenetetrazol and Fa173, a proposed transmembrane site antagonist, abolished the potentiation induced by 200 µM diazepam. Consistent with the in vitro results, flumazenil antagonized the zolpidem-induced LORR, but not that induced by diazepam or midazolam. Pentylenetetrazol and Fa173 antagonized the diazepam-induced LORR. These findings support the existence of non-classical BZD binding sites on certain GABAAR subtypes and indicate that the flumazenil-insensitive effects depend on the chemical structures of BZD ligands.

Neuropeptide S attenuates methamphetamine-induced stereotyped behavior in rats.

Effective therapies for Methamphetamine (METH) induced stereotyped behavior are still being explored. It is unclear whether Neuropeptide S (NPS) is involved in the mechanism of METH-induced stereotyped behavior. In the contemporary behavioral study, pretreatment with NPS reduces stereotyped circling significantly, but didn't have any impact on the total incidence of stereotypy and stereotyped sniffing and biting induced by METH (10 mg/kg). When METH (10 mg/kg) was administered to rats, the level of NPS in the cerebrospinal fluid was not affected, but pretreatment with NPS reversed METH-induced glutamate release in the hippocampus and striatum. The findings suggest that NPS receptor system is likely to involve in the METH-overdose-induced behaviors.

P7, a novel antagonist of corticotropin releasing factor receptor type 1 (CRFR1) screened from phage display library.

The corticotropin releasing factor (CRF) plays a central role in regulating the activities of hypothalamic-pituitary-adrenal (HPA) axis in the presence of a variety of stressful stimuli via binding to its type 1 receptors (CRFR1). Despite that many peptidic or non-peptidic antagonists of CRFR1 have been developed to serve as therapeutic tools to CRF-related pathologies, none of them have been utilized clinically. Targeting the extracellular domain 1 (EC1) of CRFR1, the CRF-binding site, represents a new strategy to inhibit the function of the receptor. However, no such agents have been identified up to now. Herein, by using an 87-amino acid fragment corresponding to the EC1 region as the bait, we screened the binding polypeptides from a phage display (Ph.D.-12) peptide library. After 3-round biopanning, positive clones were selected and the polypeptides carried by them were identified. 5 polypeptides were found to bind with the target specifically. Among them, the P7 exhibited the highest affinity. By evaluating the cAMP accumulation in the CRFR1 or CRFR2-expressing HEK293 cells, we demonstrated that P7 blocking the function of CRFR1, but not CRFR2. In addition, we also found that P7 and CRF act on CRFR1 competitively. Taken together, we reveal that P7, a novel polypeptide identified from phage display library, inhibits the function of CRFR1 effectively and specifically by binding at its EC1 domain. The new polypeptide might provide a promising agent for diagnostic or therapeutic utilities in CRF-related disorders.

Effects of olanzapine on hippocampal CA3 and the prefrontal cortex local field potentials.

Olanzapine is an antipsychotic drug applied in psychiatry to treat psychoses, especially schizophrenia and schizoaffective disorders with similar or better improvement than haloperidol and risperidone in the treatment of depressive and negative symptoms. The effect of olanzapine on neural synchrony remains to be explored. We investigated the effects of olanzapine on gamma oscillations in the CA3 region of the hippocampus and frontal association cortex. Olanzapine reduced carbachol (CCh)-induced gamma oscillation power in CA3 slice and gamma oscillation power in the frontal association cortex in vivo. The power of theta oscillations was increased in the presence of olanzapine. The phase amplitude coupling of theta and gamma wave was strengthened by the administration of olanzapine in the frontal association cortex in vivo. Taken together, these results show that olanzapine modulates local field potential and the neuronal activity.

Ethyl-enedi-ammonium sodium tetra-kis-[bis-(ethyl-enedi-amine-κ(2) N,N')(oxalato-κ(2) O (1),O (2))cobalt(III)] [penta-hydrogen di(phosphato-octa-deca-tungstate)] tetra-deca-hydrate.

The title compound, Na(C2H10N2)[Co(C2O4)(C2H8N2)2]4[H5(P2W18O62)2]·14H2O, prepared under hydro-thermal conditions, consists of two Dawson-type [P2W18O62](6-) anions, four isolated [Co(en)2(ox)](+) cations (en = ethyl-enedi-amine and ox = oxalate), one Na(+) cation, one [H2en](2+) cation, and a number of ordered (14) and disordered solvent water mol-ecules. The [P2W18O62](6-) polyoxidometalate anion has site symmetry 1 and contains two structurally distinct types of W atoms: viz. six W atoms on vertical pseudo-mirror planes grouped in two sets of three, and 12 equatorial W atoms that do not lie in the pseudo-mirror planes grouped in two sets of six. In each [Co(en)2(ox)](+) cation, the Co(III) ion is coordinated by four N atoms from two en ligands and two O atoms from the ox ligands, completing a distorted octa-hedral structure. The sodium cation lies on an inversion centre and additionally links the complex cations and anions. In the crystal, the various units are linked by N-H⋯O and O-H⋯O hydrogen bonds, which together with C-H⋯O hydrogen bonds form a three-dimensional structure. The contribution of a region of disordered electron density, possibly highly disordered solvent water mol-ecules, to the scattering was removed with the SQUEEZE option of PLATON [Spek (2009 ▶). Acta Cryst. D65, 148-155]. To equilibrate the charges five H(+) ions have been added to the polyoxidometalate. These H(+) ions and the disordered solvent contribution were not included in the reported mol-ecular weight and density.

External Ba2+ block of the two-pore domain potassium channel TREK-1 defines conformational transition in its selectivity filter.

TREK-1 is a member of the two-pore domain potassium channel family that is known as a leak channel and plays a key role in many physiological and pathological processes. The conformational transition of the selectivity filter is considered as an effective strategy for potassium channels to control the course of potassium efflux. It is well known that TREK-1 is regulated by a large volume of extracellular and intracellular signals. However, until now, little was known about the selectivity filter gating mechanism of the channel. In this research, it was found that Ba(2+) blocked the TREK-1 channel in a concentration- and time-dependent manner. A mutagenesis analysis showed that overlapped binding of Ba(2+) at the assumed K(+) binding site 4 (S4) within the selectivity filter was responsible for the inhibitory effects on TREK-1. Then, Ba(2+) was used as a probe to explore the conformational transition in the selectivity filter of the channel. It was confirmed that collapsed conformations were induced by extracellular K(+)-free and acidification at the selectivity filters, leading to nonconductive to permeable ions. Further detailed characterization demonstrated that the two conformations presented different properties. Additionally, the N-terminal truncated isoform (ΔN41), a product derived from alternative translation initiation, was identified as a constitutively nonconductive variant. Together, these results illustrate the important role of selectivity filter gating in the regulation of TREK-1 by the extracellular K(+) and proton.

A functional relationship between trigeminal astroglial activation and NR1 expression in a rat model of temporomandibular joint inflammation.

OBJECTIVE: To examine the hypothesis that glial activation would regulate the expression of the N-methyl-D-aspartate receptor subunit 1 (NR1) in the trigeminal subnucleus caudalis (Sp5C) after temporomandibular joint (TMJ) inflammation. METHODS: Inflammation of TMJ was produced in rats by injecting 50 µL complete Freund's adjuvant (CFA) into unilateral TMJ space. Sham control rats received incomplete Freund's adjuvant injection. Mechanical nociception in the affected and non-affected TMJ site was tested by using a digital algometer. Fractalkine, fluorocitrate, and/or MK801 were intracisternally administrated to examine the relationship between astroglial activation and NR1 upregulation. RESULTS: CFA TMJ injection resulted in persistent ipsilateral mechanical hyperalgesia 1, 3, and 5 days after CFA injection. The inflammation also induced significant upregulation of CX3C chemokine receptor 1 and glial fibrillary acidic protein (GFAP) beginning on day 1 and of NR1 beginning on day 3 within the ipsilateral Sp5C. Intracisternal administration of fluorocitrate for 5 days blocked the development of mechanical hyperalgesia as well as the upregulation of GFAP and NR1 in the Sp5C. Conversely, intracisternal injection of fractalkine for 5 days exacerbated the expression of NR1 in Sp5C and mechanical hyperalgesia induced by TMJ inflammation. Moreover, once daily intracisternal fractalkine administration for 5 days in naïve rats induced the upregulation of NR1 and mechanical hyperalgesia. CONCLUSIONS: These results suggest that astroglial activation contributes to the mechanism of TMJ pain through the regulation of NR1 expression in Sp5C.

Role of 5-HT2A Receptor in Modulating Glutamatergic Activity in the Ventrolateral Orbital Cortex: Implication in Trigeminal Neuralgia.

5-HT2A receptors (5-HT2ARs) are widely expressed in the central nervous system, including in the ventrolateral orbital cortex (VLO). The VLO is an important cortical component for pain processing. Brain 5-HT2ARs are implicated in both pro- and anti- nociceptive functions. However, the roles of 5-HT2ARs in the VLO in trigeminal neuralgia and neuronal synaptic function remain to be understood. We used chronic constriction injury of infraorbital nerve (IoN-CCI) model and shRNA mediated gene knockdown in mice to investigate the role of 5-HT2ARs in the VLO in trigeminal neuralgia. We found that knockdown of 5-HT2ARs in the VLO aggravated spontaneous pain and mechanical allodynia in mice after IoN-CCI. At the synaptic level, decreasing 5-HT2AR expression by shRNA or inhibition of 5-HT2AR activity by its antagonist ketanserin decreased the frequency and amplitude of spontaneous excitatory postsynaptic currents (sEPSCs) of the neurons in the VLO, whereas 5-HT2AR partial agonist 2,5-Dimethoxy-4-iodoamphetamine (DOI) enhanced sEPSCs of the neurons in the VLO. In summary, 5-HT2ARs in the VLO modulate the trigeminal pain by regulating neuronal glutamatergic activity.

Role of 5-HT1A-mediated upregulation of brain indoleamine 2,3 dioxygenase 1 in the reduced antidepressant and antihyperalgesic effects of fluoxetine during maintenance treatment.

The reduced antidepressant and antihyperalgesic effects of selective serotonin reuptake inhibitors (SSRIs) such as fluoxetine during maintenance treatment has been reported, but little is known about the molecular mechanism of this phenomenon. In three comorbid pain and depression animal models (genetic predisposition, chronic social stress, arthritis), we showed that the fluoxetine's antidepressant and antihyperalgesic effects were reduced during the maintenance treatment. Fluoxetine exposure induced upregulation of the 5-hydroxytryptamine 1A (5-HT1A) auto-receptor and indoleamine 2,3 dioxygenase 1 (IDO1, a rate-limiting enzyme of tryptophan metabolism) in the brainstem dorsal raphe nucleus (DRN), which shifted the tryptophan metabolism away from the 5-HT biosynthesis. Mechanistically, IDO1 upregulation was downstream to fluoxetine-induced 5-HT1A receptor expression because 1) antagonism of the 5-HT1A receptor with WAY100635 or 5-HT1A receptor knockout blocked the IDO1 upregulation, and 2) inhibition of IDO1 activity did not block the 5-HT1A receptor upregulation following fluoxetine exposure. Importantly, inhibition of either the 5-HT1A receptor or IDO1 activity sustained the fluoxetine's antidepressant and antihyperalgesic effects, indicating that 5-HT1A-mediated IDO1 upregulation in the brainstem DRN contributed to the reduced antidepressant and antihyperalgesic effects of fluoxetine. These results suggest a new strategy to improving the therapeutic efficacy of SSRI during maintenance treatment.

Distribution of Acid Sensing Ion Channels in Axonal Growth Cones and Presynaptic Membrane of Cultured Hippocampal Neurons.

Although acid-sensing ion channels (ASICs) are widely expressed in the central nervous system, their distribution and roles in axonal growth cones remain unclear. In this study, we examined ASIC localization and function in the axonal growth cones of cultured immature hippocampal neurons. Our immunocytochemical data showed that native and overexpressed ASIC1a and ASIC2a are both localized in growth cones of cultured young hippocampal neurons. Calcium imaging and electrophysiological assay results were utilized to validate their function. The calcium imaging test results indicated that the ASICs (primarily ASIC1a) present in growth cones mediate calcium influx despite the addition of voltage-gated Ca2+ channels antagonists and the depletion of intracellular calcium stores. The electrophysiological tests results suggested that a rapid decrease in extracellular pH at the growth cones of voltage-clamped neurons elicits inward currents that were blocked by bath application of the ASIC antagonist amiloride, showing that the ASICs expressed at growth cones are functional. The subsequent immuno-colocalization test results demonstrated that ASIC1a and ASIC2a are both colocalized with Neurofilament-H and Bassoon in mature hippocampal neurons. This finding demonstrated that after reaching maturity, ASIC1a and ASIC2a are both distributed in axons and the presynaptic membrane. Our data reveal the distribution of functional ASICs in growth cones of immature hippocampal neurons and the presence of ASICs in the axons and presynaptic membrane of mature hippocampal neurons, indicating a possible role for ASICs in axonal guidance, synapse formation and neurotransmitter release.

Reversible luminescence switching of NaYF4:Yb,Er nanoparticles with controlled assembly of gold nanoparticles.

Upon the tunable surface plasmon band of the pH-induced reversible assembly of gold nanoparticles mediated by cysteine, the manipulation of green and red upconversion emission, and the switching of the red emission of the NaYF(4):Yb,Er nanoparticles have been achieved in a facile and reproducible way.

HCN channel antagonist ZD7288 ameliorates neuropathic pain and associated depression.

Chronic neuropathic pain has demonstrated that coexisting psychiatric disorders are associated with disability and poorer treatment outcomes. Hyperpolarization-activated cyclic nucleotide-gated (HCN, Ih) channels play a major role in pain via hyperexcitability and facilitation of ectopic firing in neurons. Neuronal hyperexcitability contributes to pain maintenance and anxiety/depression. GABA-mediated inhibitory postsynaptic neurotransmission in the brain is impaired in the pathophysiology of chronic neuropathic pain with comorbidity mood disorders. Currently, interaction of HCN channels and GABAergic synaptic transmission inhibition in neuropathic pain and the associated comorbidity anxiety/depression mechanism remains relatively unknown. To address this, the HCN channel inhibitor, ZD7288, was administrated to Wistar Kyoto (WKY) rats after spared nerve injury (SNI). Our findings show that intracerebroventricular injection of ZD7288 concurrently attenuates co-existing nociceptive and depression-like behaviors, and increases glutamicacid decarboxylase (GAD67/65) expression and GABA levels in the hippocampus and thalamus with High-performance liquid chromatography technique. It suggests that inhibition of HCN channels is likely to decrease the hyperexcitability of neurons in rat SNI and improve the level of GABA. Further, HCN channel may offer a new strategy to alleviate both neuropathic pain and comorbidity for depression.

C101, a novel 4-amino-piperidine derivative selectively blocks N-type calcium channels.

N-type Ca2+ channels located on presynaptic nerve terminals regulate neurotransmitter release, including that from the spinal terminations of primary afferent nociceptors. Pharmacological and ion-channel gene knockdown approaches in animals have revealed N-type Ca2+ channels to be particularly attractive molecular targets for the discovery and development of new analgesic drugs. In recent years, some non-peptide small molecular N-type Ca2+ channel blockers have been reported. However, low selectivity and some side effects limit their further development. To overcome these disadvantages, some new compounds were designed and synthesized in our institute by optimizing the 4-amino-piperidine template. C101, one of these compounds, was demonstrated to block N-type Ca2+ channels with higher selectivity. It was found that C101 produced concentration-dependent inhibition on N-type Ca2+ channels expressed in Xenopus oocytes with an IC50 is 2.2+/-0.6 microM. The current-voltage relationship was not altered after 2-min exposure to C101. However, the steady-state inactivation relationship curve was shifted to more negative potentials for channels. Therefore, it seemed that C101 blocks the inactivated channel. C101 did not present any remarkable effects on voltage-gated potassium, sodium channels in cultured rat hippocampal neurons, and L-, P/Q-, R-type calcium channels and HERG channels expressed in Xenopus oocytes. The results suggested that C101 was a high selective blocker targeting N-type Ca2+ channels, and may have a potential to be developed as a novel analgesic agent.

Cognitive impairment in a rat model of neuropathic pain: role of hippocampal microtubule stability.

Clinical evidence indicates that cognitive impairment is a common comorbid condition of chronic pain. However, the cellular basis for chronic pain-mediated cognitive impairment remains unclear. We report here that rats exhibited memory deficits after spared nerve injury (SNI). We found that levels of stable microtubule (MT) were increased in the hippocampus of the rats with memory deficits. This increase in stable MT is marked by α-tubulin hyperacetylation. Paclitaxel, a pharmacological MT stabilizer, increased the level of stable MT in the hippocampus and induced learning and memory deficits in normal rats. Furthermore, paclitaxel reduced long-term potentiation in hippocampal slices and increased stable MT (evidenced by α-tubulin hyperacetylation) levels in hippocampal neuronal cells. Intracerebroventricular infusion of nocodazole, an MT destabilizer, ameliorated memory deficits in rats with SNI-induced nociceptive behavior. Expression of HDAC6, an α-tubulin deacetylase, was reduced in the hippocampus in rats with cognitive impairment. These findings indicate that peripheral nerve injury (eg, SNI) affects the MT dynamic equilibrium, which is critical to neuronal structure and synaptic plasticity.

Nanonecklaces assembled from gold rods, spheres, and bipyramids.

Gold nanorods, nanospheres, and bipyramids have been assembled using glutathione and cysteine into three types of necklace structures, which might be useful for the fabrication of nanoscale photonic, electronic, and optoelectronic devices.

Aquaporin 4 Forms a Macromolecular Complex with Glutamate Transporter 1 and Mu Opioid Receptor in Astrocytes and Participates in Morphine Dependence.

The water channel aquaporin 4 (AQP4) is abundantly expressed in astrocytes and provides a mechanism by which water permeability of the plasma membrane can be regulated. Evidence suggests that AQP4 is associated with glutamate transporter-1 (GLT-1) for glutamate clearance and contributes to morphine dependence. Previous studies show that AQP4 deficiency changed the mu opioid receptor expression and opioid receptors' characteristics as well. In this study, we focused on whether AQP4 could form macromolecular complex with GLT-1 and mu opioid receptor (MOR) and participates in morphine dependence. By using immunofluorescence staining, fluorescence resonance energy transfer, and co-immunoprecipitation, we demonstrated that AQP4 forms protein complexes with GLT-1 and MOR in both brain tissue and primary cultured astrocytes. We then showed that the C-terminus of AQP4 containing the amino acid residues 252 to 323 is the site of interaction with GLT-1. Protein kinase C, activated by morphine, played an important role in regulating the expression of these proteins. These findings may help to reveal the mechanism that AQP4, GLT-1, and MOR form protein complex and participate in morphine dependence, and deeply understand the reason that AQP4 deficiency maintains extracellular glutamate homeostasis and attenuates morphine dependence, moreover emphasizes the function of astrocyte in morphine dependence.

Sigma-1 receptor agonist increases axon outgrowth of hippocampal neurons via voltage-gated calcium ions channels.

INTRODUCTION: Sigma-1 receptors (Sig-1Rs) are unique endoplasmic reticulum proteins that have been implicated in both neurodegenerative and ischemic diseases, such as Alzheimer's disease and stroke. Accumulating evidence has suggested that Sig-1R plays a role in neuroprotection and axon outgrowth. The underlying mechanisms of Sig-1R-mediated neuroprotection have been well elucidated. However, the mechanisms underlying the effects of Sig-1R on axon outgrowth are not fully understood. METHODS: To clarify this issue, we utilized immunofluorescence to compare the axon lengths of cultured naïve hippocampal neurons before and after the application of the Sig-1R agonist, SA4503. Then, electrophysiology and immunofluorescence were used to examine voltage-gated calcium ion channel (VGCCs) currents in the cell membranes and growth cones. RESULTS: We found that Sig-1R activation dramatically enhanced the axonal length of the naïve hippocampal neurons. Application of the Sig-1R antagonist NE100 and gene knockdown techniques both demonstrated the effects of Sig-1R. The growth-promoting effect of SA4503 was accompanied by the inhibition of voltage-gated Ca2+ influx and was recapitulated by incubating the neurons with the L-type, N-type, and P/Q-type VGCC blockers, nimodipine, MVIIA and ω-agatoxin IVA, respectively. This effect was unrelated to glial cells. The application of SA4503 transformed the growth cone morphologies from complicated to simple, which favored axon outgrowth. CONCLUSION: Sig-1R activation can enhance axon outgrowth and may have a substantial influence on neurogenesis and neurodegenerative diseases.

Growth of gold nanorods and bipyramids using CTEAB surfactant.

Gold nanorods and bipyramids have been synthesized using the seed-mediated approach in aqueous cetyltriethylammonium bromide (CTEAB) solutions in the presence of silver nitrate. Gold nanoparticle seeds that are stabilized with either CTEAB or sodium citrate have been used. The use of the CTEAB-stabilized seeds gives gold nanorods in high yield in one step with the longitudinal plasmon wavelength ranging from 750 to 1030 nm, depending on the amount of the seeds. The longitudinal plasmon wavelength can be extended to 1100 nm by the use of a two-step growth method. The growth of gold nanorods in CTEAB solutions takes 5-10 h, more than 5 times slower than that in cetyltrimethylammonium bromide solutions at the same concentration of surfactants. The use of the citrate-stabilized seeds gives both gold bipyramids and a small percentage of gold nanorods. The longitudinal plasmon wavelength of the bipyramids is tunable from 700 to 1100 nm by varying the amount of the citrate-stabilized seeds. The growth of gold bipyramids takes more than 1 day. Transmission electron microscopy characterizations reveal that the gold nanorods grown from both types of gold nanoparticle seeds are single-crystalline and that the gold bipyramids are penta-twinned.

Nucleus accumbens hyperpolarization-activated cyclic nucleotide-gated channels modulate methamphetamine self-administration in rats.

RATIONALE: Methamphetamine addiction is believed to primarily result from increased dopamine release and the inhibition of dopamine uptake. Some evidence suggests that hyperpolarization-activated cyclic nucleotide-gated (HCN) channels play important roles in the functional modulation of dopaminergic neurons and the pathophysiology of related diseases. However, little is known about the effects of HCN channels on methamphetamine addiction. OBJECTIVES: The present study investigated the role of brain HCN channels in methamphetamine addiction. RESULTS: Acute intracerebroventricular (i.c.v.) injection or bilateral intra-accumbens microinjections of non-selective HCN channel blocker ZD7288 (0.3125 and 0.625 µg) significantly reduced both methamphetamine (0.0125 or 0.05 mg/kg/infusion)-induced self-administration under fixed ratio 2 reinforcement and the breakpoint of methamphetamine (0.05 mg/kg/infusion) under progressive ratio reinforcement in rats. Moreover, compared with i.c.v. injection, bilateral intra-accumbens microinjections of ZD7288 exerted stronger inhibitory effects, suggesting that blockade of HCN channels in the nucleus accumbens reduced the reinforcing effects of and motivation for methamphetamine. We also found that ZD7288 (0.625 and 1.25 µg, i.c.v.) significantly decreased methamphetamine (1 mg/kg, intraperitoneal (i.p.))-induced hyperactivity with no effect on the spontaneous activity in rats. Finally, in vivo microdialysis experiments showed that the HCN channel blockade using ZD7288 (0.625 and 1.25 µg, i.c.v.) decreased methamphetamine (1 mg/kg, i.p.)-induced elevation of extracellular dopamine levels in the nucleus accumbens. CONCLUSIONS: These results indicate that HCN channels in the nucleus accumbens are involved in the reinforcing properties of methamphetamine and highlight the importance of HCN channels in the regulation of dopamine neurotransmission underlying methamphetamine addiction.

Neuropeptide S modulates the amygdaloidal HCN activities (Ih) in rats: Implication in chronic pain.

Neuropeptide S (NPS), an endogenous anxiolytic, has been shown to protect against chronic pain through interacting with its cognate NPS receptor (NPSR) in the brain. However, the cellular mechanism of this NPS action remains unclear. We report that NPS inhibits hyperpolarization-activated cyclic nucleotide-gated (HCN) channel current (Ih) in the rat's amygdala through activation of NPSR. This NPS effect is mediated through ERK1/2 phosphorylation in a subset of pyramidal-like neurons located in the medial amygdala. The characters of the recorded Ih suggest a major role for HCN1 activity in this process. Inhibition of Ih by NPS stimulates the glutamatergic drive onto fast spiking intra-amygdalolidal GABAergic interneurons, which in turn facilitates GABA release onto pyramidal-like neurons. Moreover, the HCN1 expression is increased in the amygdala of rats with peripheral nerve injury and intra-amygdaloidal administration of the HCN channel inhibitor ZD7288 attenuates nociceptive behavior in these rats. These results suggest that NPS-mediated modulation of intra-amygdaloidal HCN channel activities may be an important central inhibitory mechanism for regulation of chronic pain.