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Introduction: Previously observed increased sensitivity to noxious stimulation in the Dahl salt-sensitive rat strain (SS/JrHsdMcwi, abbreviated as SS) compared to Brown Norway rats (BN/NhsdMcwi abbreviated as BN) is mediated by genes on a single chromosome. The current study used behavioral and electrocortical data to determine if differences also exist between SS and BN rats in loss of consciousness. Methods: Behavioral responses, including loss of righting, (a putative index of consciousness) and concurrent electroencephalogram recordings, in 12 SS and BN rats were measured during isoflurane at inhaled concentrations of 0, 0.3, 0.6, 0.8, 1.0 and 1.2%. Results: In SS compared to BN rats, the mean ± SEM EC50 for righting was significantly less (0.65 ± 0.01% vs. 0.74 ± 0.02% inhaled isoflurane) and delta fraction in parietal electroencephalogram was enhanced 50–100% at all isoflurane levels during emergence. The frequency decay constant of an exponential fit of the parietal electroencephalogram spectrum graphed as a function of isoflurane level was three times less steep (mean ± SEM slope −57 ± 13 vs. −191 ± 38) and lower at each level of isoflurane in SS versus BN rats (i.e., shifted toward low frequency activity). Electroencephalogram differences between strains were larger during emergence than induction. Conclusions: Sensitivity is higher in SS compared to BN rats leading to unconsciousness at lower levels of isoflurane. This supports using additional strains in this animal model to study the genetic basis for differences in anesthetic action on mechanisms of consciousness. Moreover, induction and emergence appear to involve distinct pathways.

Background: ATP-sensitive potassium (KATP) channels in neurons mediate neuroprotection, they regulate membrane excitability, and they control neurotransmitter release. Because loss of DRG neuronal KATP currents is involved in the pathophysiology of pain after peripheral nerve injury, we characterized the distribution of the KATP channel subunits in rat DRG, and determined their alterations by painful axotomy using RT-PCR, immunohistochemistry and electron microscopy. Results: PCR demonstrated Kir6.1, Kir6.2, SUR1 and SUR2 transcripts in control DRG neurons. Protein expression for all but Kir6.1 was confirmed by Western blots and immunohistochemistry. Immunostaining of these subunits was identified by fluorescent and confocal microscopy in plasmalemmal and nuclear membranes, in the cytosol, along the peripheral fibers, and in satellite glial cells. Kir6.2 co-localized with SUR1 subunits. Kir6.2, SUR1, and SUR2 subunits were identified in neuronal subpopulations, categorized by positive or negative NF200 or CGRP staining. KATP current recorded in excised patches was blocked by glybenclamide, but preincubation with antibody against SUR1 abolished this blocking effect of glybenclamide, confirming that the antibody targets the SUR1 protein in the neuronal plasmalemmal membrane. In the myelinated nerve fibers we observed anti-SUR1 immunostaining in regularly spaced funneled-shaped structures. These structures were identified by electron microscopy as Schmidt-Lanterman incisures (SLI) formed by the Schwann cells. Immunostaining against SUR1 and Kir6.2 colocalized with anti-Caspr at paranodal sites. DRG excised from rats made hyperalgesic by spinal nerve ligation exhibited similar staining against Kir6.2, SUR1 or SUR2 as DRG from controls, but showed decreased prevalence of SUR1 immunofluorescent NF200 positive neurons. In DRG and dorsal roots proximal to axotomy SLI were smaller and showed decreased SUR1 immunofluorescence. Conclusions: We identified Kir6.2/SUR1 and Kir6.2/SUR2 KATP channels in rat DRG neuronal somata, peripheral nerve fibers, and glial satellite and Schwann cells, in both normal state and after painful nerve injury. This is the first report of KATP channels in paranodal sites adjacent to nodes of Ranvier and in the SLI of the Schwann cells. After painful axotomy KATP channels are downregulated in large, myelinated somata and also in SLI, which are also of smaller size compared to controls. Because KATP channels may have diverse functional roles in neurons and glia, further studies are needed to explore the potential of KATP channels as targets of therapies against neuropathic pain and neurodegeneration.

Painful axotomy decreases K ATP channel current (IK ATP ) in primary afferent neurons. Because cytosolic Ca 2+ signaling is depressed in injured dorsal root ganglia (DRG) neurons, we investigated whether Ca 2+ –calmodulin (CaM)–Ca 2+ /CaM-dependent kinase II (CaMKII) regulates IK ATP in large DRG neurons. Immunohistochemistry identified the presence of K ATP channel subunits SUR1, SUR2, and Kir6.2 but not Kir6.1, and pCaMKII in neurofilament 200–positive DRG somata. Single-channel recordings from cell-attached patches revealed that basal and evoked IK ATP by ionomycin, a Ca 2+ ionophore, is activated by CaMKII. In axotomized neurons from rats made hyperalgesic by spinal nerve ligation (SNL), basal K ATP channel activity was decreased, and sensitivity to ionomycin was abolished. Basal and Ca 2+ -evoked K ATP channel activity correlated inversely with the degree of hyperalgesia induced by SNL in the rats from which the neurons were isolated. Inhibition of IK ATP by glybenclamide, a selective K ATP channel inhibitor, depolarized resting membrane potential (RMP) recorded in perforated whole-cell patches and enhanced neurotransmitter release measured by amperometry. The selective K ATP channel opener diazoxide hyperpolarized the RMP and attenuated neurotransmitter release. Axotomized neurons from rats made hyperalgesic by SNL lost sensitivity to the myristoylated form of autocamtide-2-related inhibitory peptide (AIPm), a pseudosubstrate blocker of CaMKII, whereas axotomized neurons from SNL animals that failed to develop hyperalgesia showed normal IK ATP inhibition by AIPm. AIPm also depolarized RMP in control neurons via K ATP channel inhibition. Unitary current conductance and sensitivity of K ATP channels to cytosolic ATP and ligands were preserved even after painful nerve injury, thus providing opportunities for selective therapeutic targeting against neuropathic pain.

Background Pathophysiology in the primary sensory neuron may contribute to chronic neuropathic pain. Ca channels play a central role in neuronal processes, and sensory neurons are rich in low-voltage-activated calcium channels (LVACCs). However, the physiologic function of these channels is unknown. Their possible role in rebound burst firing makes them a candidate for increased excitability after neuropathic injury. Methods This study uses pharmacological methods to isolate LVACC in cells from the dorsal root ganglia of neuropathic and sham-operated rats, including the blockade of high-voltage-activated Ca channels with fluoride and selective toxins. LVACCs were examined with conventional whole cell patch clamp electrophysiology techniques. Results After chronic constriction injury of the peripheral axon, LVACC was significantly reduced compared to sham rats as shown by a 60% reduction in peak current density and an 80% reduction in total calcium influx. A depolarizing shift in the voltage dependence of activation and an increase in the rate of deactivation and inactivation appear to cause this reduction of LVACC. Either Ni2+ or mibefradil, blockers of LVACC, applied in the bath to normal dorsal root ganglion cells during current clamp significantly and reversibly increased excitability. Conclusions These results suggest that loss of LVACC may contribute to decreased spike frequency adaptation and increased excitability after injury to sensory neurons. Through decreased Ca2+ influx, the cell becomes less stable and more likely to initiate or transmit bursts of action potentials. Consequently, modulation of Ca2+ currents at the dorsal root ganglion may be a potential method of therapeutic intervention.

Background and Objectives: Neuropathic pain following injury to peripheral sensory neurons is a common clinical problem and frequently difficult to treat. Gabapentin (GBP), a novel anticonvulsant, has significant analgesic effects in clinical neuropathic states and in relevant preclinical models, but its mechanism of action remains unclear. Because calcium currents play a significant role in neuronal function, this study was designed to assess the effect of GBP on the membrane voltage-activated inward calcium currents (ICa) in dorsal root ganglia (DRG) primary afferent neurons of neuropathic versus control rats. Methods: Male rats were prepared according to the chronic constriction injury (CCI) model. The L4 and L5 dorsal root ganglia of those selected as CCI or control after appropriate behavioral testing were removed, and neurons were enzymatically dissociated. Fluorescent dye (DiI) placed at the injury site allowed identification of neurons projecting to that site. These were acutely studied using whole-cell, perforated (with [beta ]-escin) patch-clamp recordings. Additionally, neurons from sham or nonoperated rats were also studied. Results: Although there was marked variability among cells, concentrations of GBP ranging from 0.1 to 300 [mu ]mol/L decreased neuronal peak ICa in midsized neurons (30 to 40 [mu ]m) of both sham and neuropathic rats, in a fast, reversible, and concentration-dependent manner. Intergroup differences were not significant, however the concentration-response EC50s were 2.7 [mu ]mol/L for the sham and 16.5 [mu ]mol/L for the CCI neurons. The drug suppressed ICa in nonoperated rats to a lesser degree, but changes did not differ significantly from the operated groups. Calcium currents in either small or large diameter neurons were also variably decreased by 10 [mu ]mol/L of GBP in sham and CCI neurons. Current inhibition by GBP was partly voltage dependent. Conclusions: GBP, at clinically relevant concentrations, results in significant reduction of ICa in both sham and neuropathic neurons, while in nonoperated rats reduced ICa to a smaller degree. Sensitivity to drug was not affected by neuropathy. This current inhibition is partly voltage dependent. Depression of ICa may be partly related to the binding of the drug to the [alpha ]2[delta ] modulatory subunit of the voltage activated calcium channels (VACC). Analgesia may be due to diminished release of neurotransmitter by sensory neurons, a Ca2+-dependent process. Reg Anesth Pain Med 2002;27:47-57.

Currents through voltage-gated Ca2+channels (ICa) may be regulated by cytoplasmic Ca2+levels ([Ca2+]c), producing Ca2+-dependent inactivation (CDI) or facilitation (CDF). SinceICaregulates sensory neuron excitability, altered CDI or CDF could contribute to pain generation after peripheral nerve injury. We explored this by manipulating [Ca2+]cwhile recordingICain rat sensory neurons. In uninjured neurons, elevating [Ca2+]cwith a conditioning prepulse (−15 mV, 2 s) inactivatedICameasured during subsequent test pulses (−15 mV, 5 ms). This inactivation was Ca2+-dependent (CDI), since it was decreased with elimination of Ca2+influx by depolarization to above theICareversal potential, with high intracellular Ca2+buffering (EGTA 10 mmor BAPTA 20 mm), and with substitution of Ba2+for extracellular Ca2+, revealing a residual voltage-dependent inactivation. At longer latencies after conditioning (>6 s),ICarecovered beyond baseline. This facilitation also proved to be Ca2+-dependent (CDF) using the protocols limiting cytoplasmic Ca2+elevation. Ca2+/calmodulin-dependent protein kinase II (CaMKII) blockers applied by bath (KN-93, myristoyl-AIP) or expressed selectively in the sensory neurons (AIP) reduced CDF, unlike their inactive analogues. Protein kinase C inhibition (chelerythrine) had no effect. Selective blockade of N-type Ca2+channels eliminated CDF, whereas L-type channel blockade had no effect. Following nerve injury, CDI was unaffected, but CDF was eliminated in axotomized neurons. Excitability of sensory neurons in intact ganglia from control animals was diminished after a similar conditioning pulse, but this regulation was eliminated by injury. These findings indicate thatICain sensory neurons is subject to both CDI and CDF, and that hyperexcitability following injury-induced loss of CDF may result from diminished CaMKII activity.

Stably expressed housekeeping genes (HKGs) are necessary for standardization of transcript measurement by quantitative real time PCR (qRT-PCR). Peripheral nerve injury disrupts expression of numerous genes in sensory neurons, but the stability of conventional HKGs has not been tested in this context. We examined the stability of candidate HKGs during nerve injury, including the commonly used 18s ribosomal RNA (18s rRNA), β tubulin I (Tubb5) and β tubulin III (Tubb3), actin, glyceraldehyde 3-phosphate dehydrogenase (GAPDH) and hypoxanthine phosphoribosyl transferase 1 (HPRT1), and mitogen activated protein kinase 6 (MAPK6). Total RNA for cDNA synthesis was isolated from dorsal root ganglia of rats at 3, 7 and 21 days following either skin incision alone or spinal nerve ligation, after which the axotomized and adjacent ganglia were analyzed separately. Relative stability of HKGs was determined using statistical algorithms geNorm and NormFinder. Both analyses identified MAPK6 and GAPDH as the two most stable HKGs for normalizing gene expression for qRT-PCR analysis in the context of peripheral nerve injury. Our findings indicate that a priori analysis of HKG expression levels is important for accurate normalization of gene expression in models of nerve injury.

Background The nucleus basalis of Meynert of the basal forebrain has been implicated in the regulation of the state of consciousness across normal sleep-wake cycles. Its role in the modulation of general anesthesia was investigated. Methods Rats were chronically implanted with bilateral infusion cannulae in the nucleus basalis of Meynert and epidural electrodes to record the electroencephalogram in frontal and visual cortices. Animals were anesthetized with desflurane at a concentration required for the loss of righting reflex (4.6 ± 0.5%). Norepinephrine (17.8 nmol) or artificial cerebrospinal fluid was infused at 0.2 μl/min (1 μl total). Behavioral response to infusion was measured by scoring the orofacial, limb, and head movements, and postural changes. Results Behavioral responses were higher after norepinephrine (2.1 ± 1) than artificial cerebrospinal fluid (0.63 ± 0.8) infusion (P < 0.01, Student t test). Responses were brief (1-2 min), repetitive, and more frequent after norepinephrine infusion (P < 0.0001, chi-square test). Electroencephalogram delta power decreased after norepinephrine in frontal (70 ± 7%) but not in visual cortex (P < 0.05, Student t test). Simultaneously, electroencephalogram cross-approximate entropy between frontal and visual cortices increased from 3.17 ± 0.56 to 3.85 ± 0.29 after norepinephrine infusion (P < 0.01, Student t test). Behavioral activation was predictable by the decrease in frontal delta power (logistic regression, P < 0.05). Conclusions Norepinephrine infusion into the nucleus basalis of Meynert can modulate anesthetic depth presumably by ascending activation of the cortex. The transient nature of the responses suggests a similarity with microarousals normally observed during natural sleep, and may imply a mechanism for transient awareness under light anesthesia.

Medically unexplained physical symptoms (MUPS) are common and difficult to treat.To investigate the effectiveness of adding five-element acupuncture to usual care in 'frequent attenders' with MUPS.Randomised controlled trial in four London general practices.Participants were 80 adults with MUPS, consulting GPs ≥8 times/year. The intervention was individualised five-element acupuncture, ≥12 sessions, immediately (acupuncture group) and after 26 weeks (control group). The primary outcome was 26-week Measure Yourself Medical Outcome Profile (MYMOP); secondary outcomes were wellbeing (W-BQ12), EQ-5D, and GP consultation rate. Intention-to-treat analysis was used, adjusting for baseline outcomes.Participants (80% female, mean age 50 years, mixed ethnicity) had high health-resource use. Problems were 59% musculoskeletal; 65%1 year duration. The 26-week questionnaire response rate was 89%. Compared to baseline, the mean 26-week MYMOP improved by 1.0 (95% confidence interval [CI] = 0.4 to 1.5) in the acupuncture group and 0.6 (95% CI = 0.3 to 0.9) in the control group (adjusted mean difference: acupuncture versus control -0.6 [95% CI = -1.1 to 0] P = 0.05). Other between-group adjusted mean differences were: W-BQ12 4.4 (95% CI = 1.6 to 7.2) P = 0.002; EQ-5D index 0.03 (95% CI = -0.11 to 0.16) P = 0.70; consultation rate ratio 0.90 (95% CI = 0.70 to 1.15) P = 0.4; and number of medications 0.56 (95% CI = 0.47 to 1.6) P = 0.28. All differences favoured the acupuncture group. Imputation for missing values reduced the MYMOP adjusted mean difference to -0.4 (95% CI = -0.9 to 0.1) P = 0.12. Improvements in MYMOP and W-BQ12 were maintained at 52 weeks.The addition of 12 sessions of five-element acupuncture to usual care resulted in improved health status and wellbeing that was sustained for 12 months.

Background Reports of Ca(2+) current I(Ca) loss after injury to peripheral sensory neurons do not discriminate between axotomized and spared neurons. The spinal nerve ligation model separates axotomized from spared neurons innervating the same site. The authors hypothesized that I(Ca) loss is a result of neuronal injury, so they compared axotomized L5 dorsal root ganglion neurons to spared L4 neurons, as well as neurons from rats undergoing skin incision alone. Methods After behavioral testing, dissociated neurons from L4 and L5 dorsal root ganglia were studied in both current and voltage patch clamp modes. The biophysical consequence of I(Ca) loss on the action potential was confirmed using selective I(Ca) antagonists. Data were grouped into small, medium, and large cells for comparison. Results Reduced I(Ca) was predominantly a consequence of axotomy (L5 after spinal nerve ligation) and was most evident in small and medium neurons. ICa losses were associated with action potential prolongation in small and medium cells, whereas the amplitude and duration of after hyperpolarization was reduced in medium and large neurons. Blockade with Ca(2+) channel antagonists showed that action potential prolongation and after hyperpolarization diminution were alike, attributable to the loss of I(Ca). Conclusion Axotomy is required for I(Ca) loss. I(Ca) loss correlated with changes in the biophysical properties of sensory neuron membranes during action potential generation, which were due to I(Ca) loss leading to decreased outward Ca(2+)-sensitive K currents. Taken together, these results suggest that neuropathic pain may be mediated, in part, by loss of I(Ca) and the cellular processes dependent on Ca(2+).

Background Painful peripheral nerve injury results in disordered sensory neuron function that contributes to the pathogenesis of neuropathic pain. However, the relative roles of neurons with transected axons versus intact adjacent neurons have not been resolved. An essential first step is identification of electrophysiologic changes in these two neuronal populations after partial nerve damage. Methods Twenty days after spinal nerve ligation (SNL), intracellular recordings were obtained from axotomized fifth lumbar (L5) dorsal root ganglion neurons and adjacent, intact L4 neurons, as well as from control neurons and others subjected to sham-SNL surgery. Results Pronounced electrophysiologic changes were seen only in L5 neurons after SNL. Both Aalpha/beta and Adelta neuron types showed increased action potential duration, decreased afterhyperpolarization amplitude and duration, and decreased current threshold for action potential initiation. Aalpha/beta neurons showed resting membrane potential depolarization, and increased repetitive firing during sustained depolarization developed in Adelta neurons. The afterhyperpolarization duration in neurons with C fibers shortened after axotomy. In contrast to the axotomized L5 neurons, neighboring L4 neurons showed no changes in action potential duration, afterhyperpolarization dimensions, or excitability after SNL. Depolarization rate (dV/dt) increased after SNL in L4 Aalpha/beta and Adelta neurons but decreased in L5 neurons. Time-dependent rectification during hyperpolarizing current injection (sag) was greater after SNL in Aalpha/beta L4 neurons compared with L5. Sham-SNL surgery produced only a decreased input resistance in Aalpha/beta neurons and a decreased conduction velocity in medium-sized cells. In the L5 ganglion after axotomy, a novel set of neurons, consisting of 24% of the myelinated population, exhibited long action potential durations despite myelinated neuron conduction velocities, particularly depolarized resting membrane potential, low depolarization rate, and absence of sag. Conclusions These findings indicate that nerve injury-induced electrical instability is restricted to axotomized neurons and is absent in adjacent intact neurons.

Perforated patch recordings of neuronal calcium currents (I(Ca)) with amphotericin B or nystatin reduce dialysis of intracellular constituents and current rundown, but can be difficult and frequently unsuccessful. We investigated the saponin beta-escin as a putative ionophore for perforated patch I(Ca) recordings in acutely dissociated, rat dorsal root ganglion neurons. I(Ca) was recorded in time-course studies after including either beta-escin (50 microM), or amphotericin B (240 microg/ml) as perforating ionophores in the internal pipette solution, in comparison to standard ruptured-patch technique, using suction. Perforated patches were allowed to take place spontaneously. The percentage loss of I(Ca) per min (within the first 20 min) was significantly less after beta-escin (0.0518%) (n = 18), versus either amphotericin (1.82%) (n = 12) or standard patch (4.52%) (n = 7), (P0.001). The slope of the rundown after linear fit was also less after beta-escin (P0.001). Minimal "steady-state" access resistance (R(a)) of 6.6 +/- 1.6 MOmega was achieved within 7.1 +/- 9.3 min following perforation with beta-escin, 7.9 +/- 3.5 MOmega within 44 =/- 14 min after amphotericin B, and 6.8 +/- 1.9 MOmega with standard patch (P0.05 for R(a), and P0.01 for permeabilization time, respectively). Success rates were 59% with beta-escin versus 27% with amphotericin. Leak10% of peak I(Ca) was present in 25% of cells after beta-escin versus 20% after amphotericin, and 12% after standard technique. Perforated patches using beta-escin were stable for 15-60 min. We conclude that beta-escin may be used as an alternative ionophore for perforated patch-clamp studies in neurons, and results in minimal rundown that can facilitate long-term recordings of I(Ca). Limited rundown may be due to better preservation of cytosolic ATP content.

Background Behavioral criteria that confirm neuropathic pain in animal injury models are undefined. Therefore, the authors sought clinically relevant measures that distinguish pain behavior of rats with peripheral nerve injury from those with sham injury. Methods The authors examined mechanical and thermal sensory sensitivity, comparing responses at baseline to responses after spinal nerve ligation (SNL group), sham nerve injury (sham group), or skin incision alone (control group). Results Substantial variance was evident in all sensory tests at baseline. After surgery, tests using brush, cold, or heat stimulation showed minimal distinctions between surgical groups. Postsurgical thresholds for flexion withdrawal from mechanical stimulation with von Frey fibers were decreased bilaterally in SNL and sham groups. In contrast, the probability of a complex hyperalgesia-type response with prolonged elevation, shaking, or licking of the paw was selectively increased on the ipsilateral side in the SNL group. Nonetheless, the effect of SNL on behavior was inconsistent, regardless of the sensory test. The behavioral measure that best distinguishes between SNL and sham groups and thereby best identifies animals with successful SNL-induced neuropathic pain is increased ipsilateral postsurgical probability of a hyperalgesia-type response to noxious mechanical stimulation. Using receiver operating characteristics analysis, mechanical hyperalgesia identifies a local SNL effect in approximately 60% of animals when specificity is required to be 90% or higher. Conclusions Simple withdrawal from von Frey tactile stimulation, although frequently used, is not a valid measure of peripheral nerve injury pain in rats, whereas a complex hyperalgesic-type response is a specific neuropathy-induced behavior.

ATP-sensitive potassium (K(ATP)) currents were examined in dorsal root ganglion neurons from neuropathic and control rats using whole-cell voltage clamp recordings. K(ATP) channel openers (diazoxide and pinacidil) enhanced, and the blocker glibenclamide inhibited an outward current in control neurons in a manner dependent on the pipette ATP concentration. Analysis of reversal potentials showed that this current is carried by K(+) ions. Outward current in cells from rats with peripheral nerve injury was not sensitive to modulators of K(ATP) channels. Gabapentin, a putative K(ATP) channel opener, had minimal effect on currents in either group of neurons. We conclude that normal primary afferent neurons express K(ATP) channels that conduct current which is eliminated by peripheral nerve injury. Gabapentin does not affect this current significantly.

Hyperexcitability of the primary afferent neuron leads to neuropathic pain following injury to peripheral axons. Changes in calcium channel function of sensory neurons following injury have not been directly examined at the channel level, even though calcium is a primary second messenger-regulating neuronal function. We compared calcium currents (I(Ca)) in 101 acutely isolated dorsal root ganglion neurons from 31 rats with neuropathic pain following chronic constriction injury (CCI) of the sciatic nerve, to cells from 25 rats with normal sensory function following sham surgery. Cells projecting to the sciatic nerve were identified with a fluorescent label applied at the CCI site. Membrane function was determined using patch-clamp techniques in current clamp mode, and in voltage-clamp mode using solutions and conditions designed to isolate I(Ca). Somata of peripheral sensory neurons from hyperalgesic rats demonstrated decreased I(Ca). Peak calcium channel current density was diminished by injury from 3.06+/-0.30 pS/pF to 2. 22+/-0.26 pS/pF in medium neurons, and from 3.93+/-0.38 pS/pF to 2. 99+/-0.40 pS/pF in large neurons. Under these voltage and pharmacologic conditions, medium-sized neuropathic cells lacked obvious T-type calcium currents which were present in 25% of medium-sized cells from control animals. Altered Ca(2+) signalling in injured sensory neurons may contribute to hyperexcitability leading to neuropathic pain.

Publisher Summary This chapter demonstrates that inhaled anesthetics impede the reflex ability of mesenteric veins to actively constrict and dilate in reaction to baroreflex stimulation. Inhaled anesthetics depress mean arterial pressure, heart rate, and sympathetic efferent outflow. Both low and high doses of inhaled anesthetics attenuate the reflex constriction of mesenteric veins caused by lowered carotid sinus pressure, whereas reflex dilation in response to aortic depressor nerve stimulation has been reduced by the higher dose of inhaled anesthetics. Furthermore, volatile anesthetics dramatically reduce the reflex increase in sympathetic efferent nerve activity as a result of baroreceptor stimulation. On the other hand, direct celiac sympathetic postganglionic activation of the mesenteric veins has been unaffected by even the highest dose of inhaled anesthetics. These findings support the hypothesis that volatile anesthetics may influence mesenteric vascular capacitance through inhibition of the active sympathetic control of veins. An active change in venous capacitance is to be distinguished from a passive reduction of arterial inflow or a redistribution of blood among vascular beds. In situ studies of the differential effects of α1– and α2–adrenoceptor activation on the constriction of mesenteric arteries demonstrate the predominance of α1–receptors in response to endogenous electric stimulation of the celiac ganglion and exogenous application of phenylephrine. The present studies have contributed new evidence from direct observation of the mesenteric veins, indicating that anesthetics inhibit baroreflex regulation of vein diameter and subsequent changes in intravenous pressure, and that the capacitance of the mesenteric bed is, thereby increased.

The CACTUS Study is a randomised pragmatic trial with a nested qualitative study comparing traditional acupuncture with usual care in people who consult frequently with medically unexplained symptoms.1 2 Margaret McCartney has based her Observations article about it on several inaccuracies (quotations from her article in italics below).3 (1) The “wellbeing score” was better in the control group than in the acupuncture group . This statement is untrue: an adjusted mean difference in favour of acupuncture was seen with wellbeing (wellbeing questionnaire, W-BQ12: 4.4 (1.6 to 7.2); P=0.002). This difference remained significant after missing values were imputed (3.4 (0.5 to 6.3); P=0.02). (2) The graphical …

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Background ATP-sensitive potassium (KATP) channels in neurons regulate excitability, neurotransmitter release and mediate protection from cell-death. Furthermore, activation of KATP channels is suppressed in DRG neurons after painful-like nerve injury. NO-dependent mechanisms modulate both KATP channels and participate in the pathophysiology and pharmacology of neuropathic pain. Therefore, we investigated NO modulation of KATP channels in control and axotomized DRG neurons. Results Cell-attached and cell-free recordings of KATP currents in large DRG neurons from control rats (sham surgery, SS) revealed activation of KATP channels by NO exogenously released by the NO donor SNAP, through decreased sensitivity to [ATP]i. This NO-induced KATP channel activation was not altered in ganglia from animals that demonstrated sustained hyperalgesia-type response to nociceptive stimulation following spinal nerve ligation. However, baseline opening of KATP channels and their activation induced by metabolic inhibition was suppressed by axotomy. Failure to block the NO-mediated amplification of KATP currents with specific inhibitors of sGC and PKG indicated that the classical sGC/cGMP/ PKG signaling pathway was not involved in the activation by SNAP. NO-induced activation of KATP channels remained intact in cell-free patches, was reversed by DTT, a thiol-reducing agent, and prevented by NEM, a thiol-alkylating agent. Other findings indicated that the mechanisms by which NO activates KATP channels involve direct S-nitrosylation of cysteine residues in the SUR1 subunit. Specifically, current through recombinant wild-type SUR1/Kir6.2 channels expressed in COS7 cells was activated by NO, but channels formed only from truncated isoform Kir6.2 subunits without SUR1 subunits were insensitive to NO. Further, mutagenesis of SUR1 indicated that NO-induced KATP channel activation involves interaction of NO with residues in the NBD1 of the SUR1 subunit. Conclusion NO activates KATP channels in large DRG neurons via direct S-nitrosylation of cysteine residues in the SUR1 subunit. The capacity of NO to activate KATP channels via this mechanism remains intact even after spinal nerve ligation, thus providing opportunities for selective pharmacological enhancement of KATP current even after decrease of this current by painful-like nerve injury.