Local Blockade Research Articles

Cell Therapy for Parkinson's Disease: A Translational Approach to Assess the Role of Local and Systemic Immunosuppression.

Neural transplantation is a promising therapeutic approach for neurodegenerative diseases; however, many patients receiving intracerebral fetal allografts exhibit signs of immunization to donor antigens that could compromise the graft. In this context, we intracerebrally transplanted mesencephalic pig xenografts into primates to identify a suitable strategy to enable long-term cell survival, maturation, and differentiation. Parkinsonian primates received WT or CTLA4-Ig transgenic porcine xenografts and different durations of peripheral immunosuppression to test whether systemic plus graft-mediated local immunosuppression might avoid rejection. A striking recovery of spontaneous locomotion was observed in primates receiving systemic plus local immunosuppression for 6 mo. Recovery was associated with restoration of dopaminergic activity detected both by positron emission tomography imaging and histological examination. Local infiltration by T cells and CD80/86+ microglial cells expressing indoleamine 2,3-dioxigenase were observed only in CTLA4-Ig recipients. Results suggest that in this primate neurotransplantation model, peripheral immunosuppression is indispensable to achieve the long-term survival of porcine neuronal xenografts that is required to study the beneficial immunomodulatory effect of local blockade of T cell costimulation.

Ultrasound Guided Intercostobrachial Nerve Blockade in Patients with Persistent Pain after Breast Cancer Surgery: A Pilot Study

Background: Persistent pain after breast cancer surgery (PPBCS) affects 25 – 60% of breast cancer survivors and damage to the intercostobrachial nerve (ICBN) has been implicated as the cause of this predominantly neuropathic pain. Local anesthetic blockade of the ICBN could provide clues to pathophysiological mechanisms as well as aiding diagnosis and treatment of PPBCS but has never been attempted. Objectives: To assess the feasibility of ICBN blockade and assess its effects on pain and sensory function in patients with PPBCS. Study Design: This prospective pilot study was performed in 2 parts: Part 1 determined the sonoanatomy of the ICBN and part 2 examined effects of the ultrasound-guided ICBN blockade in patients with PPBCS. Setting: Section for Surgical Pathophysiology at Rigshospitalet, Copenhagen, Denmark. Methods: Part 1: Sixteen unoperated, pain free breast cancer patients underwent systematic ultrasonography to establish the sonoanatomy of the ICBN. Part 2: Six patients with PPBCS who had pain in the axilla and upper arm were recruited for the study. Summed pain intensity (SPI) scores and sensory function were measured before and 30 minutes after the block was administered. SPI is a combined pain score of numerical rating scale (NRS) at rest, movement, and 100kPa pressure applied to the maximum point of pain using pressure algometry (max = 30). Sensory function was measured using quantitative sensory testing, which consisted of sensory mapping, thermal thresholds, suprathreshold heat pain perception as well as heat and pressure pain thresholds. The ICBN block was performed under ultrasound guidance and 10 mL 0.5% bupivacaine was injected. Outcome Assessment: The ability to perform the ICBN block and its analgesic and sensory effects. Results: Only the second intercostal space could be seen on ultrasound which was adequate to perform the ICBN block. The mean difference in SPI was -9 NRS points (95%CI: -14.1 to -3.9), P = 0.006. All patients had pre-existing areas of hypoesthesia which decreased in size in 4/6 patients after the block. Limitations: The main limitation of this pilot study is its small sample size, but despite this, a statistically significant effect was observed. Conclusion: We have successfully managed to block the ICBN using ultrasound guidance and demonstrated an analgesic effect in patients in PPBCS calling for placebo-controlled studies. Key words: Anesthesia, local; intercostobrachial nerve; mastectomy; nerve block; neuralgia

Local Control of Extracellular Dopamine Levels in the Medial Nucleus Accumbens by a Glutamatergic Projection from the Infralimbic Cortex.

It is generally assumed that infralimbic cortex (ILC) and prelimbic cortex, two adjacent areas of the medial prefrontal cortex (mPFC) in rodents, provide selective excitatory glutamatergic inputs to the nucleus accumbens (NAc) shell and core, respectively. It is also generally believed that mPFC influences the extracellular levels of dopamine in the NAc primarily by an excitatory collateral to the ventral tegmental area (VTA). In the present study, we first established the existence of a selective functional connection between ILC and the posteromedial portions of the VTA (pmVTA) and the mNAc shell (pmNAc shell), by measuring striatal neuronal activation (immunohistochemical analysis of ERK1/2 phosphorylation) and glutamate release (in vivo microdialysis) upon ILC electrical stimulation. A novel optogenetic-microdialysis approach allowed the measurement of extracellular concentrations of glutamate and dopamine in the pmNAc shell upon local light-induced stimulation of glutamatergic terminals from ILC. Cortical electrical and local optogenetic stimulation produced significant increases in the extracellular concentrations of glutamate and dopamine in the pmNAc shell. Local blockade of glutamate release by perfusion of an adenosine A2A receptor antagonist in the pmNAc shell blocked the dopamine release induced by local optogenetic stimulation but only partially antagonized dopamine release induced by cortical electrical stimulation. The results demonstrate that ILC excitatory afferents directly modulate the extracellular concentration of dopamine in the pmNAc shell, but also support the involvement of an indirect mechanism of dopamine control, through a concomitant ILC-mediated activation of the pmVTA. Significance statement: We established the existence of a functional connection between the infralimbic cortex (ILC) and the posteromedial portions of the ventral tegmental area (pmVTA) and the medial nucleus acumbens shell (pmNAc shell). A novel optogenetic-microdialysis approach allowed us to demonstrate that local glutamate release from glutamatergic terminals from the ILC exert a significant modulation of extracellular concentration of dopamine in the pmNAc shell. This mechanism provides the frame for a selective cortical-mediated tonic dopaminergic modulation of specific striatal compartments.

The Specific Features of Microcirculatory Disorders Induced by Experimental Phlebothrombosis and Local Venous Blockade

The Specific Features of Microcirculatory Disorders Induced by Experimental Phlebothrombosis and Local Venous Blockade

Dopamine-dependent modulation of rat globus pallidus excitation by nicotine acetylcholine receptors.

The globus pallidus (GP) coordinates information processing in the basal ganglia nuclei. The contribution of nicotinic cholinergic receptors (nAChRs) to the spiking activity of GP neurons is largely unknown. Several studies have reported that the effect of nAChRs in other nuclei depends on dopaminergic input. Via in vivo single unit extracellular recordings and intranuclear drug infusions, we analyzed the effects of local activation and blockade of nAChRs in neurons of both sham and 6-hydroxydopamine (6-OHDA)-lesioned rats. In sham rats, the local application of nicotine and edrophonium (an acetylcholinesterase inhibitor) increases GP neurons spiking rate. Local application of mecamylamine, a neuronal nicotinic cholinergic antagonist, diminishes pallidal neurons spiking rate, an effect not produced by d-tubocurarine, a peripheral nicotinic cholinergic antagonist. Moreover, mecamylamine blocks the excitatory effect evoked by nicotine and edrophonium. In 6-OHDA-lesioned rats, local infusion of nicotine does not change pallidal neurons firing rate. Our results show that there is a tonic cholinergic input to the GP that increases their spiking rate through the activation of nAChRs and that this effect depends on functional dopaminergic pathways.

Early Immune Infiltrate and Tumor-Specific Immune Response Resulting in Improved Survival with Combination of Local Chemotherapy and Immune Checkpoint Blockade

Early Immune Infiltrate and Tumor-Specific Immune Response Resulting in Improved Survival with Combination of Local Chemotherapy and Immune Checkpoint Blockade

Effects of striatal nitric oxide production on regional cerebral blood flow and seizure development in rats exposed to extreme hyperoxia.

The endogenous vasodilator and signaling molecule nitric oxide has been implicated in cerebral hyperemia, sympathoexcitation, and seizures induced by hyperbaric oxygen (HBO2) at or above 3 atmospheres absolute (ATA). It is unknown whether these events in the onset of central nervous system oxygen toxicity originate within specific brain structures and whether blood flow is diverted to the brain from peripheral organs with high basal flow, such as the kidney. To explore these questions, total and regional cerebral blood flow (CBF) were measured in brain structures of the central autonomic network in anesthetized rats in HBO2 at 6 ATA. Electroencephalogram (EEG) recordings, cardiovascular hemodynamics, and renal blood flow (RBF) were also monitored. As expected, mean arterial blood pressure and total and regional CBF increased preceding EEG spikes while RBF was unaltered. Of the brain structures examined, the earliest rise in CBF occurred in the striatum, suggesting increased neuronal activation. Continuous unilateral or bilateral striatal infusion of the nitric oxide synthase inhibitor N(ω)-nitro-L-arginine methyl ester attenuated CBF responses in that structure, but global EEG discharges persisted and did not differ from controls. Our novel findings indicate that: 1) cerebral hyperemia in extreme HBO2 in rats does not occur at the expense of renal perfusion, highlighting the remarkable autoregulatory capability of the kidney, and 2) in spite of a sentinel increase in striatal blood flow, additional brain structure(s) likely govern the pathogenesis of HBO2-induced seizures because EEG discharge latency was unchanged by local blockade of striatal nitric oxide production and concomitant hyperemia.

Detection of attempted movement from the EEG during neuromuscular block: proof of principle study in awake volunteers.

Brain-Computer Interfaces (BCIs) have the potential to detect intraoperative awareness during general anaesthesia. Traditionally, BCI research is aimed at establishing or improving communication and control for patients with permanent paralysis. Patients experiencing intraoperative awareness also lack the means to communicate after administration of a neuromuscular blocker, but may attempt to move. This study evaluates the principle of detecting attempted movements from the electroencephalogram (EEG) during local temporary neuromuscular blockade. EEG was obtained from four healthy volunteers making 3-second hand movements, both before and after local administration of rocuronium in one isolated forearm. Using offline classification analysis we investigated whether the attempted movements the participants made during paralysis could be distinguished from the periods when they did not move or attempt to move. Attempted movement trials were correctly identified in 81 (68–94)% (mean (95% CI)) and 84 (74–93)% of the cases using 30 and 9 EEG channels, respectively. Similar accuracies were obtained when training the classifier on the participants’ actual movements. These results provide proof of the principle that a BCI can detect movement attempts during neuromuscular blockade. Based on this, in the future a BCI may serve as a communication channel between a patient under general anaesthesia and the anaesthesiologist.

Surgical injury in the neonatal rat alters the adult pattern of descending modulation from the rostroventral medulla.

Neonatal pain and injury can alter long-term sensory thresholds. Descending rostroventral medulla (RVM) pathways can inhibit or facilitate spinal nociceptive processing in adulthood. As these pathways undergo significant postnatal maturation, the authors evaluated long-term effects of neonatal surgical injury on RVM descending modulation. Plantar hind paw or forepaw incisions were performed in anesthetized postnatal day (P)3 Sprague-Dawley rats. Controls received anesthesia only. Hind limb mechanical and thermal withdrawal thresholds were measured to 6 weeks of age (adult). Additional groups received pre- and post-incision sciatic nerve levobupivacaine or saline. Hind paw nociceptive reflex sensitivity was quantified in anesthetized adult rats using biceps femoris electromyography, and the effect of RVM electrical stimulation (5-200 μA) measured as percentage change from baseline. In adult rats with previous neonatal incision (n = 9), all intensities of RVM stimulation decreased hind limb reflex sensitivity, in contrast to the typical bimodal pattern of facilitation and inhibition with increasing RVM stimulus intensity in controls (n = 5) (uninjured vs. neonatally incised, P < 0.001). Neonatal incision of the contralateral hind paw or forepaw also resulted in RVM inhibition of hind paw nociceptive reflexes at all stimulation intensities. Behavioral mechanical threshold (mean ± SEM, 28.1 ± 8 vs. 21.3 ± 1.2 g, P < 0.001) and thermal latency (7.1 ± 0.4 vs. 5.3 ± 0.3 s, P < 0.05) were increased in both hind paws after unilateral neonatal incision. Neonatal perioperative sciatic nerve blockade prevented injury-induced alterations in RVM descending control. Neonatal surgical injury alters the postnatal development of RVM descending control, resulting in a predominance of descending inhibition and generalized reduction in baseline reflex sensitivity. Prevention by local anesthetic blockade highlights the importance of neonatal perioperative analgesia.

Contracting human skeletal muscle maintains the ability to blunt α1‐adrenergic vasoconstriction during KIR channel and Na+/K+‐ATPase inhibition

During exercise there is a balance between vasoactive factors that facilitate increases in blood flow and oxygen delivery to the active tissue and the sympathetic nervous system, which acts to limit muscle blood flow for the purpose of blood pressure regulation. Functional sympatholysis describes the ability of contracting skeletal muscle to blunt the stimulus for vasoconstriction, yet the underlying signalling of this response in humans is not well understood. We tested the hypothesis that activation of inwardly rectifying potassium channels and the sodium-potassium ATPase pump, two potential vasodilator pathways within blood vessels, contributes to the ability to blunt α1 -adrenergic vasoconstriction. Our results show preserved blunting of α1 -adrenergic vasconstriction despite blockade of these vasoactive factors. Understanding this complex phenomenon is important as it is impaired in a variety of clinical populations. Sympathetic vasoconstriction in contracting skeletal muscle is blunted relative to that which occurs in resting tissue; however, the mechanisms underlying this 'functional sympatholysis' remain unclear in humans. We tested the hypothesis that α1 -adrenergic vasoconstriction is augmented during exercise following inhibition of inwardly rectifying potassium (KIR ) channels and Na(+) /K(+) -ATPase (BaCl2 +ouabain). In young healthy humans, we measured forearm blood flow (Doppler ultrasound) and calculated forearm vascular conductance (FVC) at rest, during steady-state stimulus conditions (pre-phenylephrine), and after 2min of phenylephrine (PE; an α1 -adrenoceptor agonist) infusion via brachial artery catheter in response to two different stimuli: moderate (15% maximal voluntary contraction) rhythmic handgrip exercise or adenosine infusion. In Protocol1 (n=11 subjects) a total of six trials were performed in three conditions: control (saline), combined enzymatic inhibition of nitric oxide (NO) and prostaglandin (PG) synthesis (l-NMMA+ketorolac) and combined inhibition of NO, PGs, KIR channels and Na(+) /K(+) -ATPase (l-NMMA+ketorolac+BaCl2 +ouabain). In Protocol2 (n=6) a total of four trials were performed in two conditions: control (saline), and combined KIR channel and Na(+) /K(+) -ATPase inhibition. All trials occurred after local β-adrenoceptor blockade (propranolol). PE-mediated vasoconstriction was calculated (%ΔFVC) in each condition. Contrary to our hypothesis, despite attenuated exercise hyperaemia of ∼30%, inhibition of KIR channels and Na(+) /K(+) -ATPase, combined with inhibition of NO and PGs (Protocol1) or alone (Protocol2) did not enhance α1 -mediated vasoconstriction during exercise (Protocol1: -27±3%; P=0.2vs. control, P=0.4vs. l-NMMA+ketorolac; Protocol2: -21±7%; P=0.9vs. control). Thus, contracting human skeletal muscle maintains the ability to blunt α1 -adrenergic vasoconstriction during combined KIR channel and Na(+) /K(+) -ATPase inhibition.

Aberrant Activation of TGF-β in Subchondral Bone at the Onset of Rheumatoid Arthritis Joint Destruction.

Rheumatoid arthritis (RA) is an autoimmune disease that often leads to joint destruction. A myriad of drugs targeting the immune abnormalities and downstream inflammatory cascades have been developed, but the joint destruction is not effectively halted. Here we report that aberrant activation of TGF-β in the subchondral bone marrow by immune response increases osteoprogenitors and uncoupled bone resorption and formation in RA mouse/rat models. Importantly, either systemic or local blockade of TGF-β activity in the subchondral bone attenuated articular cartilage degeneration in RA. Moreover, conditional deletion of TGF-β receptor II (Tgfbr2) in nestin-positive cells also effectively halted progression of RA joint destruction. Our data demonstrate that aberrant activation of TGF-β in the subchondral bone is involved at the onset of RA joint cartilage degeneration. Thus, modulation of subchondral bone TGF-β activity could be a potential therapy for RA joint destruction.

Complex regional pain syndrome type I: a comprehensive review.

Complex regional pain syndrome type I (CRPS I), formerly known as reflex sympathetic dystrophy (RSD), is a chronic painful disorder that usually develops after a minor injury to a limb. This topical review gives a synopsis of CRPS I and discusses the current concepts of our understanding of CRPS I in adults, the diagnosis, and treatment options based on the limited evidence found in medical literature. CRPS I is a multifactorial disorder. Possible pathophysiological mechanisms of CRPS I are classic and neurogenic inflammation, and maladaptive neuroplasticity. At the level of the central nervous system, it has been suggested that an increased input from peripheral nociceptors alters the central processing mechanisms. A literature search was conducted using, as electronic bibliographic database, Medline from 1980 until 2014. An early diagnosis and multidisciplinary treatment are necessary to prevent permanent disability. The pharmacological treatment of CRPS I is empirical and insufficiently effective. Further research is needed regarding the therapeutic modalities discussed in the guidelines. Physical therapy is widely recommended as a first-line treatment. The efficacy of local anesthetic sympathetic blockade as treatment for CRPS I is questionable.

Obturator nerve block transurethral surgery for bladder cancer: comparison of inguinal and intravesical approaches: prospective randomized trial.

Transurethral resection of bladder tumors close to these areas may stimulate the obturator nerve, causing violent adductor contraction and possible inadvertent bladder perforation. To avoid this reaction, local anesthetic blockade of the obturator nerve as it passes through the obturator canal is effective in stopping adductor spasm during spinal anesthesia. Forty-one patients undergoing (transurethral resection of bladder tumor) TUR-BT with spinal anesthesia who required (obturator nerve block) ONB were included in the study. After spinal anesthesia, ONB was performed with an inguinal approach (group 1) (n=21) or an intravesical approach (group 2) (n=20). In this study, we used 10ml of 2% lidocaine to perform the ONB. The mean age of patients was 60.8±7.5years. The groups were not different with regards to age, tumor localization and tumor size. There were two bladder perforations in group 1 and six perforations in group 2 (p=0.130). However, the efficacy of ONB was significantly higher in inguinal approach group compared to intravesical approach group (p=0.032). Obturator nerve block plays an additive role on the quality of analgesia for bladder surgery. Our data suggests that identification of the obturator nerve with ultrasound is easy and the block can be assessed by observing avoidance of bladder spasm.

Safety and tolerability of a novel inhaled GATA3 mRNA targeting DNAzyme in patients with TH2-driven asthma

Safety and tolerability of a novel inhaled GATA3 mRNA targeting DNAzyme in patients with TH2-driven asthma

Sympathoexcitation by Inhibition of SK Channel Activity in the Hypothalamic PVN is Attenuated by Local AT1 Receptor Blockade

Small conductance Ca2+ activated K+ (SK) channels act as negative feedback regulators of neuronal excitability. We have reported that SK channels expressed in the paraventricular nucleus (PVN) are involved in controlling neuronal activity, sympathetic nerve activity (SNA) and arterial pressure (AP). Blockade of SK channels in the pre‐sympathetic PVN neurons increases neuronal excitability, SNA and AP. Here we investigated the effect of angiotensin II type 1 receptor (AT1R) blockade on the sympathoexcitatory and presser responses elicited by the inhibition of SK channels in the PVN. In anesthetized rats, PVN microinjection of SK channel blocker with apamin (12.5 pmol, 50nl) (n=7) increased splanchnic SNA (SSNA) (278 ± 50%), renal SNA (RSNA) (193 ± 12%), and mean AP (MAP) (32 ± 4mmHg). Pre‐treatment with PVN injection of losartan (20 nmol), an AT1R antagonist, significantly attenuated (n=6) the elevated SSNA (129 ± 37%; p&lt;.05 vs vehicle control), RSNA (84 ± 40%; p&lt;.05 vs vehicle control), and MAP (10 ± 6mmHg; p&lt;.05 vs vehicle control) after PVN injection of apamin. Pre‐treatment with PVN injection of ZD7155 (1.0 nmol), another AT1R antagonist, significantly attenuated (n=5) the elevated SSNA (112 ± 30%; p&lt;.05 vs vehicle control), RSNA (81 ± 23%; p&lt;.05 vs vehicle control) and MAP (7 ± 2mmHg; p&lt;.05 vs vehicle control) elicited by PVN apamin. No significant difference was found between pretreatment with losartan and ZD7155 for SNA and MAP. Our data indicate that sympathoexcitation and pressor responses induced by inhibition of SK channel activity involve the activation of AT1R in the PVN. Support: AHA7420029 (ZYS) 2640130 (QHC).

Randomized clinical trial comparing two different techniques of local anesthesia (subcutaneous versus subcutaneous & deep infiltration) for postoperative pain in patients undergoing open appendecectomy.

This study compared the postoperative analgesic effect of local anesthetic (LA) injected subcutaneous (SC) alone versus local anesthetic injected both SC and deep in patients undergoing open appendecectomy operations. Sixty patients ASA class I-II undergoing open appendecectomy for presumed acute appendicitis will be randomly assigned into three groups. After routine monitoring, anesthesia induction was performed with propofol, fentanyl and, cis-atracurium; later, maintenance was continued with isoflurane. GA received local infiltration of the skin prior to incision with bupivacaine 0.25% (10 ml), GB received received half the bupivacaine infiltrated into the skin and other half deep-to external oblique prior to incision to create a local nerve field blockade & GC received half dose of saline subcutaneous & half deep to external oblique muscle prior to incision. Postoperative pain was assessed using visual analogue score (VAS) at 1, 4, 8, & 24 hours post extubation. Pethidine 1 mg/kg was given if VAS is ≥ 4. All patients in GA (SC) and Control required postoperative analgesics, compared to only 60% of the patients in GB (SC+deep). Time for the first analgesic requirement was prolonged in GB compared to other groups (P < 0.01). VAS scores were significantly lower in patients of GB in the first 8 hr. postoperative compared to GA &GC (P < 0.01).

Augmentation of Functional Sympatholysis via Endothelial Signaling Is Independent of Nitric Oxide and Prostaglandins in Humans

Sympathetic vasoconstriction is blunted in contracting skeletal muscle in an intensity dependent manner, and increasing endothelium‐dependent vasodilatory signaling during mild exercise can augment this “sympatholysis” similar to that observed during moderate exercise. Here, we determine the role of nitric oxide (NO) and vasodilating prostaglandins (PGs) to the endothelium‐dependent augmentation of sympatholysis during mild exercise. In 10 young subjects we measured forearm blood flow (Doppler ultrasound) and calculated vascular conductance (FVC) responses to local intra‐arterial infusion of phenylephrine (PE; α1‐agonist) during 1) infusion of the endothelium‐dependent dilator acetylcholine (ACH), 2) moderate (15% maximum voluntary contraction; MVC) handgrip exercise and 3) mild (5% MVC) exercise + ACH infusion. Trials were repeated after combined local blockade of NO/PGs (L‐NMMA/Ketorolac, respectively). Vasoconstriction to PE was blunted during 15% exercise compared to control ACH infusion (ΔFVC: ‐14±3% vs ‐30±3%, P&lt;0.05). Augmenting endothelium‐dependent signaling during 5% exercise blunted vasoconstriction similar to 15% exercise (ΔFVC: ‐8±4%). After blockade of NO/PGs, vasoconstriction to PE was blunted in all conditions (ΔFVC: ACH: ‐20±5%; 15% MVC: ‐15±5%; 5%MVC + ACH: ‐7±4%; all P&lt;0.05) relative to control ACH infusion. These data demonstrate that increasing endothelial vasodilatory signaling limits sympathetic vasoconstriction independent of NO/PGs, implicating a role for endothelial hyperpolarization in sympatholysis in humans. Support: HL102720

Increased expression of HCN2 channel protein in L4 dorsal root ganglion neurons following axotomy of L5- and inflammation of L4-spinal nerves in rats

A hallmark of peripheral neuropathic pain (PNP) is chronic spontaneous pain and/or hypersensitivity to normally painful stimuli (hyperalgesia) or normally nonpainful stimuli (allodynia).This pain results partly from abnormal hyperexcitability of dorsal root ganglion (DRG) neurons. We have previously shown, using a modified version of the lumbar 5 (L5)-spinal nerve ligation model of PNP (mSNA model involving L5-spinal nerve axotomy plus loose ligation of the lumbar 4 (L4)-spinal nerve with neuroinflammation-inducing chromic-gut), that L4 DRG neurons exhibit increased spontaneous activity, the key characteristic of neuronal hyperexcitability. The underlying ionic and molecular mechanisms of the hyperexcitability of L4 DRG neurons are incompletely understood, but could result from changes in expression and/or function of ion channels including hyperpolarization-activated cyclic nucleotide-gated (HCN) channels, which are active near the neuron’s resting membrane potential, and which produce an excitatory inward current that depolarizes the membrane potential toward the threshold of action potential generation. Therefore, in the present study we used the mSNA model to investigate whether: (a) expression of HCN1–HCN3 channels is altered in L4 DRG neurons which, in the mSNA model, are essential for transmission of the evoked pain, and which contribute to chronic spontaneous pain, and (b) local (intraplantar) blockade of these HCN channels, with a specific blocker, ZD7288, attenuates chronic spontaneous pain and/or evoked pain in mSNA rats. We found 7days after mSNA: (1) a significant increase in HCN2-immunoreactivity in small (<30μm) DRG neurons (predominantly IB4-negative neurons), and in the proportion of small neurons expressing HCN2 (putative nociceptors); (2) no significant change in HCN1- or HCN3-immunoreactivity in all cell types; and (3) attenuation, with ZD7288 (100μM intraplantar), of chronic spontaneous pain behavior (spontaneous foot lifting) and mechanical, but not, heat hypersensitivity. The results suggest that peripheral HCN channels contribute to mechanisms of spinal nerve injury-induced PNP, and that HCN channels, possibly HCN2, represent a novel target for PNP treatment.

Stress Impairs Prefrontal Cortical Function via D1 Dopamine Receptor Interactions With Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels

BackgroundPsychiatric disorders such as schizophrenia are worsened by stress, and working memory deficits are often a central feature of illness. Working memory is mediated by the persistent firing of prefrontal cortical (PFC) pyramidal neurons. Stress impairs working memory via high levels of dopamine D1 receptor (D1R) activation of cyclic adenosine monophosphate signaling, which reduces PFC neuronal firing. The current study examined whether D1R-cyclic adenosine monophosphate signaling reduces neuronal firing and impairs working memory by increasing the open state of hyperpolarization-activated cyclic nucleotide-gated (HCN) cation channels, which are concentrated on dendritic spines where PFC pyramidal neurons interconnect. MethodsA variety of methods were employed to test this hypothesis: dual immunoelectron microscopy localized D1R and HCN channels, in vitro recordings tested for D1R actions on HCN channel current, while recordings in monkeys performing a working memory task tested for D1R-HCN channel interactions in vivo. Finally, cognitive assessments following intra-PFC infusions of drugs examined D1R-HCN channel interactions on working memory performance. ResultsImmunoelectron microscopy confirmed D1R colocalization with HCN channels near excitatory-like synapses on dendritic spines in primate PFC. Mouse PFC slice recordings demonstrated that D1R stimulation increased HCN channel current, while local HCN channel blockade in primate PFC protected task-related firing from D1R-mediated suppression. D1R stimulation in rat or monkey PFC impaired working memory performance, while HCN channel blockade in PFC prevented this impairment in rats exposed to either stress or D1R stimulation. ConclusionsThese findings suggest that D1R stimulation or stress weakens PFC function via opening of HCN channels at network synapses.

Temporal expression of growth factors triggered by epiregulin regulates inflammation development.

In this study, we investigated the relationship between several growth factors and inflammation development. Serum concentrations of epiregulin, amphiregulin, betacellulin, TGF-α, fibroblast growth factor 2, placental growth factor (PLGF), and tenascin C were increased in rheumatoid arthritis patients. Furthermore, local blockades of these growth factors suppressed the development of cytokine-induced arthritis in mice by inhibiting chemokine and IL-6 expressions. We found that epiregulin expression was early and followed by the induction of other growth factors at different sites of the joints. The same growth factors then regulated the expression of epiregulin at later time points of the arthritis. These growth factors were increased in patients suffering from multiple sclerosis (MS) and also played a role in the development of an MS model, experimental autoimmune encephalomyelitis. The results suggest that the temporal expression of growth factors is involved in the inflammation development seen in several diseases, including rheumatoid arthritis and MS. Therefore, various growth factor pathways might be good therapeutic targets for various inflammatory diseases.