Influence of Voltage-sensitive Ca++Channel Drugs on Bupivacaine Infiltration Anesthesia in Mice

2001 ◽  
Vol 95 (5) ◽  
pp. 1189-1197 ◽  
Author(s):  
Forrest L. Smith ◽  
Richard W. Davis ◽  
Richard Carter
Keyword(s):  
Motor Block ◽  
Radiant Heat ◽  
Tail Flick ◽  
Channel Blockers ◽  
Ca Channel ◽  
Ca Channels ◽  
Duration Of Action ◽  
Bayk 8644 ◽  
Infiltration Anesthesia

Background Local anesthesia has been traditionally associated with blockade of voltage-sensitive sodium (Na(+)) channels. Yet in vitro evidence indicates that local anesthetic mechanisms are more complex than previously understood. For example, local anesthetics bind and allosterically modify 1,4-dihydropyridine-sensitive Ca(++) channels and can reduce Ca(++) influx in tissues. The current study examines the influence of voltage-sensitive Ca(++) channels in bupivacaine infiltration anesthesia. Methods Baseline tail-flick latencies to radiant heat nociception were obtained before subcutaneous infiltration of bupivacaine and Ca(++)-modulating drugs in the tails of mice. No musculature is contained in the tail that could result in motor block. The magnitude of infiltration anesthesia over time, as well as the potency of bupivacaine alone or in the presence of Ca(++)-modulating drug, was assessed by obtaining test latencies. Results The 1,4-dihydropyridine L-type Ca(++) channel agonist S(-)-BayK-8644 reduced the duration of action and potency of bupivacaine anesthesia. In opposite fashion, nifedipine and nicardipine increased the effects of bupivacaine. Neither nifedipine nor nicardipine alone elicited anesthesia. Alternatively, the phenylalkylamine L-type blocker verapamil elicited concentration-dependent anesthesia. Other Ca(++) channel subtype blockers were investigated as well. The N-, T-, P-, and Q-type channel blockers, omega-conotoxin GVIA, flunarizine, omega-agatoxin IVA, and omega-conotoxin MVIIC, respectively, were unable to modify bupivacaine anesthesia. Conclusions These results indicate that heat nociception stimulates Ca(++) influx through L-type channels on nociceptors in skin. Although other voltage-sensitive Ca(++) channels may be located on skin nociceptors, only the L-type channel drugs affected bupivacaine in the radiant heat test.

Spike-Mediated and Graded Inhibitory Synaptic Transmission Between Leech Interneurons: Evidence for Shared Release Sites

2006 ◽  
Vol 96 (1) ◽  
pp. 235-251 ◽  
Author(s):  
Andrei I. Ivanov ◽  
Ronald L. Calabrese
Keyword(s):  
Synaptic Transmission ◽  
Synaptic Vesicles ◽  
Low Voltage ◽  
Release Site ◽  
High Threshold ◽  
Channel Blockers ◽  
Ca Channel ◽  
Ca Channels ◽  
Inhibitory Synaptic Transmission ◽  
Graded Release

Inhibitory synaptic transmission between leech heart interneurons consist of two components: graded, gated by Ca2+ entering by low-threshold [low-voltage–activated (LVA)] Ca channels and spike-mediated, gated by Ca2+ entering by high-threshold [high-voltage–activated (HVA)] Ca channels. Changes in presynaptic background Ca2+ produced by Ca2+ influx through LVA channels modulate spike-mediated transmission, suggesting LVA channels have access to release sites controlled by HVA channels. Here we explore whether spike-mediated and graded transmission can use the same release sites and thus how Ca2+ influx by HVA and LVA Ca channels might interact to evoke neurotransmitter release. We recorded pre- and postsynaptic currents from voltage-clamped heart interneurons bathed in 0 mM Na+/5 mM Ca2+ saline. Using different stimulating paradigms and inorganic Ca channel blockers, we show that strong graded synaptic transmission can occlude high-threshold/spike-mediated synaptic transmission when evoked simultaneously. Suppression of LVA Ca currents diminishes graded release and concomitantly increases the ability of Ca2+ entering by HVA channels to release transmitter. Uncaging of Ca chelator corroborates that graded release occludes spike-mediated transmission. Our results indicate that both graded and spike-mediated synaptic transmission depend on the same readily releasable pool of synaptic vesicles. Thus Ca2+, entering cells through different Ca channels (LVA and HVA), acts to gate release of the same synaptic vesicles. The data argue for a closer location of HVA Ca channels to release sites than LVA Ca channels. The results are summarized in a conceptual model of a heart interneuron release site.

Graded Inhibitory Synaptic Transmission Between Leech Interneurons: Assessing the Roles of Two Kinetically Distinct Low-Threshold Ca Currents

2006 ◽  
Vol 96 (1) ◽  
pp. 218-234 ◽  
Author(s):  
Andrei I. Ivanov ◽  
Ronald L. Calabrese
Keyword(s):  
Synaptic Transmission ◽  
Synaptic Vesicles ◽  
Time Course ◽  
Channel Blockers ◽  
Ca Channel ◽  
Ca Channels ◽  
Inhibitory Synaptic Transmission ◽  
Ca Channel Blockers ◽  
Low Threshold ◽  
Ca Currents

In leeches, two pairs of reciprocally inhibitory heart interneurons that form the core oscillators of the pattern-generating network for heartbeat possess both high- and low-threshold (HVA and LVA) Ca channels. LVA Ca current has two kinetically distinct components (one rapidly activating/inactivating, ICaF, and another slowly activating/inactivating, ICaS) that mediate graded transmission, generate plateau potentials driving burst formation, and modulate spike-mediated transmission between heart interneurons. Here we used different stimulating protocols and inorganic Ca channel blockers to separate the effects of ICaF and ICaS on graded synaptic transmission and determine their interaction and relative efficacy. Ca2+ entering by ICaF channels is more efficacious in mediating release than that entering by ICaS channels. The rate of Ca2+ entry by LVA Ca channels appears to be as critical as the amount of delivered Ca2+ for synaptic transmission. LVA Ca currents and associated graded transmission were selectively blocked by 1 mM Ni2+, leaving spike-mediated transmission unaffected. Nevertheless, 1 mM Ni2+ affected homosynaptic enhancement of spike-mediated transmission that depends on background Ca2+ provided by LVA Ca channels. Ca2+ provided by both ICaF and ICaS depletes a common pool of readily releasable synaptic vesicles. The balance between availability of vesicles and Ca2+ concentration and its time course determine the strength of inhibitory transmission between heart interneurons. We argue that Ca2+ from multichannel domains arising from ICaF channels, clustered near but not directly associated with the release trigger, and Ca2+ radially diffusing from generally distributed ICaS channels interact at common release sites to mediate graded transmission.

scholarly journals The dihydropyridine-sensitive calcium channel subtype in cone photoreceptors.

1996 ◽  
Vol 107 (5) ◽  
pp. 621-630 ◽  
Author(s):  
M F Wilkinson ◽  
S Barnes
Keyword(s):  
Channel Blocker ◽  
Channel Blockers ◽  
Ca Channel ◽  
Ca Channels ◽  
Cone Photoreceptors ◽  
Channel Current ◽  
Ca Channel Blockers ◽  
Voltage Dependent ◽  
P Type ◽  
Ca Channel Current

High-voltage activated Ca channels in tiger salamander cone photoreceptors were studied with nystatin-permeabilized patch recordings in 3 mM Ca2+ and 10 mM Ba2+. The majority of Ca channel current was dihydropyridine sensitive, suggesting a preponderance of L-type Ca channels. However, voltage-dependent, incomplete block (maximum 60%) by nifedipine (0.1-100 microM) was evident in recordings of cones in tissue slice. In isolated cones, where the block was more potent, nifedipine (0.1-10 microM) or nisoldipine (0.5-5 microM) still failed to eliminate completely the Ca channel current. Nisoldipine was equally effective in blocking Ca channel current elicited in the presence of 10 mM Ba2+ (76% block) or 3 mM Ca2+ (88% block). 15% of the Ba2+ current was reversibly blocked by omega-conotoxin GVIA (1 microM). After enhancement with 1 microM Bay K 8644, omega-conotoxin GVIA blocked a greater proportion (22%) of Ba2+ current than in control. After achieving partial block of the Ba2+ current with nifedipine, concomitant application of omega-conotoxin GVIA produced no further block. The P-type Ca channel blocker, omega-agatoxin IVA (200 nM), had variable and insignificant effects. The current persisting in the presence of these blockers could be eliminated with Cd2+ (100 microM). These results indicate that photoreceptors express an L-type Ca channel having a distinguishing pharmacological profile similar to the alpha 1D Ca channel subtype. The presence of additional Ca channel subtypes, resistant to the widely used L-, N-, and P-type Ca channel blockers, cannot, however, be ruled out.

Assessment of Differential Blockade by Amitriptyline and Its N -Methyl Derivative in Different Species by Different Routes

2003 ◽  
Vol 98 (6) ◽  
pp. 1484-1490 ◽  
Author(s):  
Peter Gerner ◽  
Anna E. Haderer ◽  
Mustafa Mujtaba ◽  
Yukari Sudoh ◽  
Sanjeet Narang ◽  
...  
Keyword(s):  
Sciatic Nerve ◽  
Nerve Fibers ◽  
Spinal Block ◽  
Na Channel ◽  
Channel Blockers ◽  
Patch Clamp Technique ◽  
Duration Of Action ◽  
Drug Concentrations ◽  
Nerve Model

Background Increasing the duration of local anesthesia and/or creating greater differential blockade (i.e., selective block of pain-transmitting nerve fibers) has been attempted by modifying currently available agents. Most drugs show a different profile depending on the model or species studied. This study was designed to investigate the differential nerve-blocking properties of amitriptyline and its quaternary ammonium derivative in rats and sheep. Methods The Na+ channel-blocking properties of N-methyl amitriptyline were determined with the patch clamp technique in cultured GH(3) cells. Various functions (motor, nociception, proprioception-ataxia) were compared in rats (spinal and sciatic nerve blockade) and sheep (spinal blockade) with amitriptyline, N-methyl amitriptyline, lidocaine, and bupivacaine (partially from historical data). Results In vitro testing revealed N-methyl amitriptyline to be a potent Na+ channel blocker similar to amitriptyline but with a much longer duration of action. All drug concentrations tested in both the sciatic nerve model and the spinal block model produced no significant differential blockade in rats. Three of six rats in the 20-mM N-methyl amitriptyline group showed residual blockade 4 days after sciatic nerve injection. However, in the sheep spinal model, amitriptyline and in particular N-methyl amitriptyline displayed significant differential blockade at most time points. Sheep data for lidocaine and bupivacaine seemed to be more comparable to the clinical experience in humans than did rat data. Conclusions Amitriptyline and N-methyl amitriptyline are potent Na+ channel blockers and show greater differential blockade in sheep than in rats. This differential blockade in sheep is greater than that produced by lidocaine or bupivacaine.

Disparate effects of Ca channel blockade on afferent and efferent arteriolar responses to ANG II

1989 ◽  
Vol 256 (6) ◽  
pp. F1015-F1020 ◽  
Author(s):  
P. K. Carmines ◽  
L. G. Navar
Keyword(s):  
Calcium Antagonist ◽  
Angiotensin Ii ◽  
Calcium Channel Blockers ◽  
Channel Blockers ◽  
Ca Channel ◽  
Ang Ii ◽  
Channel Blockade ◽  
Afferent Arterioles ◽  
Organic Calcium Antagonists

Previous reports have suggested that organic calcium antagonists only partially inhibit the renal hemodynamic actions of angiotensin II (ANG II). This study tested the hypothesis that the calcium antagonist-sensitive component of ANG II-induced vasoconstriction is localized at a preglomerular site. Videomicroscopic measurements of vascular dimension were performed on in vitro blood-perfused juxtamedullary nephrons from captopril-treated rats. Under control conditions, afferent and efferent arteriolar diameters averaged 23.0 +/- 1.6 and 21.2 +/- 2.2 microns, respectively. Topical application of 0.1 nM ANG II decreased the diameters of afferent (-17 +/- 2%) and efferent (-15 +/- 3%) arterioles. Both 50 microM verapamil and 10 microM diltiazem dilated afferent arterioles. Verapamil also elicited a modest efferent vasodilation. In the presence of either verapamil or diltiazem, the effect of ANG II to decrease efferent diameter was sustained (-15 +/- 4%); however, the effect of ANG II on afferent diameter was abolished (-1 +/- 1%). These observations document differential influences of calcium channel blockers on ANG II-mediated vasoconstriction and suggest that the pre- and postglomerular vasoconstrictor actions of ANG II may occur through different calcium entry or mobilization mechanisms.

Modulation of Ca by agents affecting voltage-sensitive Ca channels in mesangial cells

1989 ◽  
Vol 257 (6) ◽  
pp. F1094-F1099 ◽  
Author(s):  
Y. M. Yu ◽  
F. Lermioglu ◽  
A. Hassid
Keyword(s):  
Mesangial Cells ◽  
Mechanisms Of Action ◽  
Bay K 8644 ◽  
Channel Blockers ◽  
Ca Channel ◽  
Ca Channels ◽  
High K ◽  
Ca Channel Blockers ◽  
Lanthanum Ion ◽  
Channel Activator

The purpose of this study was to investigate the effects of depolarizing media and of Ca-channel activators and blockers on cytosolic free Ca in cultured rat mesangial cells. Membrane depolarizing media, containing 10–100 mM K+, dose dependently increased cytosolic Ca, and this effect was sustained and reversible. Nifedipine and lanthanum ion inhibited this increase, whereas verapamil was ineffective. A Ca-channel activator, BAY K 8644, dose dependently increased resting Ca levels, and nifedipine inhibited this effect. Moreover, the increase of Ca induced by maximally effective high K+ and BAY K 8644 was additive, suggesting differential mechanisms of action for the two channel activators. Nifedipine and verapamil decreased resting Ca levels by up to 35–40%. The results support the idea that mesangial cells have spontaneously active Ca channels that can be further activated by membrane depolarization or by the Ca-channel activator, BAY K 8644, and inhibited by the Ca-channel blockers, nifedipine or verapamil. Voltage-sensitive Ca channels in mesangial cells may play a role in the regulation of the glomerular filtration rate.

scholarly journals Formulation and Evaluation of Parenteral Sustained Release Microspheres of Diclofenac Sodium

2003 ◽  
Vol 71 (2) ◽  
pp. 101-111
Author(s):  
C. Sajeev ◽  
R. Archna ◽  
V. Gupta ◽  
A. Sobti ◽  
R. Saha
Keyword(s):  
Sustained Release ◽  
Response Time ◽  
Diclofenac Sodium ◽  
In Vitro Release ◽  
Tail Flick ◽  
Duration Of Action ◽  
Sustained Release Formulation ◽  
Vitro Release

The aim of this study was to formulate and evaluate microsphere based depot type parenteral sustained release formulation of diclofenac sodium (DFS). Drug was formulated in the form of microspheres, using varying proportion of ethylcellulose (EC) as the retardant material to extend the release, by phase separation-coacervation technique. The in vitro release pattern of the designed formulations was studied using modified Franz diffusion cell. In vivo pharmacodynamic study was carried out by determining the index of analgesia (increase in response time to thermal stress as percentage of basal response time). Tail flick method was employed to measure both the degree of analgesia and its duration of action. The prepared microspheres were white, free flowing, and spherical in shape with a mean particle size of 50 μm. In vitro release study of the micro-spheres in aqueous media was found to extend the release of DFS beyond 24 hours with DFS and EC ratio 1:3. The plot of log percentage remaining to be released vs. time gave a linear relationship indicating first-order release kinetics. The in vitro release rate constant (Kr) for different microspheres varied between 0.1448 hr-1 and 0.0256 hr-1. A good correlation was obtained between K, and proportion of EC in the microspheres. In vivo pharmacodynamic studies indicated that the duration of analgesic action is prolonged beyond 24 hrs in case of microsphere products of 1:3 ratio of DFS to EC, whereas administration of marketed parenteral preparation showed activity only up to 11hrs. Also, a good correlation was obtained between analgesic activity in vivo and cumulative percentage of drug release from the formulations.

Calcium paradox of the heart: a role for intracellular sodium ions

1984 ◽  
Vol 247 (5) ◽  
pp. H874-H879 ◽  
Author(s):  
R. A. Chapman ◽  
G. C. Rodrigo ◽  
J. Tunstall ◽  
R. J. Yates ◽  
P. Busselen
Keyword(s):  
Membrane Potential ◽  
Calcium Paradox ◽  
Free Fluid ◽  
Channel Blockers ◽  
Ca Channel ◽  
Ca Channels ◽  
Fish Heart ◽  
Ca Addition ◽  
Ca Ions ◽  
Normal Calcium

Hearts that have been perfused in low calcium fluids suffer, on return to normal calcium solutions, an impairment of function which can be irreversible-- the "calcium paradox." In hypothermic mammalian, amphibian, and fish heart the strong contracture, which is a typical first stage in the development of the calcium paradox, is reversible and appears to depend on a large rise in intracellular Na concentration ([Na]i), which occurs during the period of Ca deprivation. This rise is mainly due to a maintained inward Na flux through the Ca channels and causes a depolarization of the membrane potential, which stabilizes at about -20 mV. In frog atrial muscle if the membrane potential is clamped to values more negative than -50 mV during the period of Ca deprivation, no contracture develops on the restoration of the extracellular Ca concentration ([Ca]o). In all tissues the depolarization, the rise in [Na]i, and the Ca addition contracture are blocked by Ca channel blockers, antiarrhythmic drugs, and Mg ions if present in the Ca-free fluid. These agents are ineffective, however, if applied after a period of Ca deprivation when [Na]i has already risen. The influx of Ca ions, on Ca repletion, is therefore unlikely to be via the Ca channels and would seem to be through the Na-Ca exchange.

scholarly journals Selectivity of the Ca binding site in synaptosome Ca channels. Inhibition of Ca influx by multivalent metal cations.

1984 ◽  
Vol 83 (6) ◽  
pp. 941-967 ◽  
Author(s):  
D A Nachshen
Keyword(s):  
Binding Site ◽  
Divalent Cations ◽  
Channel Blockers ◽  
Ca Channel ◽  
Ca Channels ◽  
Coulombic Interactions ◽  
Cation Selectivity ◽  
Channel Inhibition ◽  
Ca Uptake ◽  
Voltage Dependent

K-stimulated (voltage-dependent) influx of 45Ca was measured in synaptosomes (isolated presynaptic nerve terminals) from rat brain. Influx was terminated at 1 s with a rapid-filtration technique, so that most of the Ca uptake was mediated by inactivating ("fast") Ca channels (Nachshen, D. A., and Blaustein, M. P., 1980, J. Gen. Physiol., 76:709-728). This influx was blocked by multivalent cations with half-inhibition constants (K1) that clustered in three distinct groups: (a) K1 greater than 1 mM (Mg2+, Sr2+, and Ba2+); (b) K1 = 30-100 microM (Mn2+, Co2+, Ni2+, Cu2+, Zn2+, and Hg2+); (c) K1 less than 1 micro M (Cd2+, Y3+, La3+ and the trivalent lanthanides, and Pb2+). Most of these ions had very little effect on synaptosome steady state membrane potential, which was monitored with a voltage-sensitive fluorescent dye, or on the voltage dependence of Ca influx, which was assessed by measuring voltage-dependent Ca uptake at two levels of depolarization. The blockers inhibited Ca influx by competing with Ca for the channel site that is involved in the transport of divalent cations. Onset of fast channel inhibition by Mg, Co, Ni, Cu, Zn, Cd, La, Hg, and Pb was rapid, occurring within 1 s; inhibition was similar after 1 s or 30 min of exposure to these ions. The inhibition produced by Co, Cu, Zn, Cd, La, and Pb could be substantially reversed within 1 s by removing the inhibitory cation. The relative efficacies of the lanthanides as fast channel blockers were compared; there was a decrease in inhibitory potency with decreasing ionic radius. A model of the Ca channel binding site is considered, in which inhibitory polyvalent cation selectivity is determined primarily by coulombic interactions between the binding site and the different cations. The site is envisaged as consisting of two anions (radius 1 A) with a separation of 2 A between them. Small cations are unable to bind effectively to both anions. The selectivity sequences predicted for the alkaline earth cations, lanthanides, and transition metals are in substantial agreement with the selectivity sequences observed for inhibition of the fast Ca channel.

Lidocaine-loaded reduced graphene oxide hydrogel for prolongation of effects of local anesthesia: In vitro and in vivo analyses

2021 ◽  
Vol 35 (8) ◽  
pp. 1034-1042
Author(s):  
Weifan Li ◽  
Guangqi Zhang ◽  
Xiaoxia Wei
Keyword(s):  
Graphene Oxide ◽  
Reduced Graphene Oxide ◽  
Local Anesthesia ◽  
Ex Vivo ◽  
Tail Flick ◽  
Tail Flick Test ◽  
Duration Of Action ◽  
Reduced Graphene

Lidocaine is widely used as a local anesthetic for alleviation of post-operative pain and for management of acute and chronic painful conditions. Although several approaches are currently used to prolong the duration of action, an effective strategy to achieve neural blockage for several hours remains to be identified. In this study, a lidocaine-loaded Pluronic® F68-reduced graphene oxide hydrogel was developed to achieve sustained release of lidocaine. Fourier transform infrared spectroscopy, X-ray diffraction, and Raman spectroscopy confirmed the synthesis of Pluronic® F68-reduced graphene oxide. Transmission electron microscopy showed wrinkled, flat nanosheets with micelles attached. The developed hydrogel showed desirable pH, viscosity, adhesiveness, hardness, and cohesiveness for topical application. The ex vivo release study demonstrated the ability of the Pluronic® F68-reduced graphene oxide hydrogel to prolong release up to 10 h, owing to the strong π–π interactions between the graphene oxide and the lidocaine. In comparison with a commercial lidocaine ointment, the developed graphene oxide hydrogel showed sustained anesthetic effect in the radiant heat tail flick test and sciatic nerve block model. Thus, this study demonstrates the potential of using Pluronic® F68-reduced graphene oxide nanocarriers to realize prolonged effects of local anesthesia for effective pain management.

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