Modulation of calcium fluxes across synaptosomal plasma membrane by local anesthetics

Effect of Peribulbar Anesthesia with and Without Adrenaline on Retinal Thickness in Patients Undergoing Elective Cataract Surgery

Background

The toxic effect of local anesthesia on the retina has been previously investigated in animal studies but not in humans.

Objectives

The objective of this study was to clarify the effect of local anesthesia with lidocaine versus local anesthesia with lidocaine with extra administration of adrenaline on the retinal layer thickness measured by optical coherence tomography (OCT) in patients indicated for elective cataract surgery.

Methods

This is a randomized controlled trial conducted on 60 patients indicated for elective cataract surgery under local anesthesia with lidocaine. Thirty participants received local anesthesia with lidocaine 2% with extra administration of adrenaline (adrenaline group), and 30 participants received local anesthesia with lidocaine 2% only (control group). The retinal thickness was measured for all participants preoperatively and one week postoperatively using OCT.

Results

The OCT findings showed statistically significant decreases postoperatively in superior (P value = 0.028), inferior (P value = 0.017), and average (P value = 0.021) retinal thickness in the adrenaline group. Moreover, there were statistically significant decreases postoperatively in superior (P value = 0.032), inferior (P value = 0.046), and average (P value = 0.028) retinal thickness in the control group. Comparing the adrenaline and control groups for the OCT findings, there was no statistically significant difference between the groups regarding the decreases in superior (P value = 0.325), inferior (P value = 0.642), and average (P value = 0.291) retinal thickness.

Conclusions

Local anesthesia with lidocaine significantly decreased the retinal thickness. The extra administration of adrenaline to lidocaine did not affect the post-anesthetic changes in the retinal thickness.

Down-regulation of norepinephrine transporter expression on membrane surface induced by chronic administration of desipramine and the antagonism by co-administration of local anesthetics in mice

We have previously shown that chronic administration of the antidepressant desipramine, a norepinephrine transporter (NET) inhibitor to mice markedly enhanced convulsions induced by local anesthetics and that behavioral sensitization may be relevant to decreased [(3)H]norepinephrine uptake by the isolated hippocampus. The co-administration of local anesthetics with desipramine reversed the behavioral sensitization and down-regulation of NET function induced by desipramine. The present study aimed to elucidate whether chronic treatment with desipramine regulates the expression of NET protein examined in membrane fractions in various brain regions and whether co-administration of local anesthetics affects the desipramine-induced alteration of NET expression. Desipramine with or without local anesthetics was injected intraperitoneally once a day for 5 days. The animals were decapitated 48 h after the last administration of drugs and the whole cell fraction, membrane fraction and cell-surface protein fraction were prepared. [(3)H]nisoxetine binding was significantly reduced in the P2 fraction of the hippocampus by chronic administration of desipramine, and the reduction was overcome by co-administration of lidocaine with desipramine. Immunoreactive NET was detected by SDS-PAGE and immunoblotting in the murine hippocampus. NET protein expression in the whole cell fraction and membrane fraction was not affected by treatment with any drugs. However, administration of desipramine significantly reduced the amount of immunoreactive NET in the cell-surface protein fraction. This reduction was blocked by simultaneous injection of lidocaine, bupivacaine or tricaine. These results indicate that the NET down-regulation indicated by the reduction of [(3)H]nisoxetine binding was induced by administration of desipramine via decrease of NET localization on the cell surface. The antagonistic actions of local anesthetics against NET down-regulation by desipramine were related to alterations of the cell-surface localization of NET.

Multiple phases of relief from experimental mechanical allodynia by systemic lidocaine: responses to early and late infusions

Systemic lidocaine can relieve various forms of neuropathic pain that develop after nerve injury. Mechanical allodynia, defined by a significant drop in paw withdrawal threshold force following spinal nerve ligation (L5-L6) in rats, can be reversed by one 30min lidocaine infusion at a constant plasma concentration as low as 1-2 microg/ml, an effect that is still present when the rats are tested days and weeks afterwards. In this study, we resolved the detailed time course of reversal of ipsilateral and contralateral allodynia in rats with spinal nerve ligation by a single systemic infusion of lidocaine, to 4 microg/ml, given either 2 days after ligation (POD2) or 7 days after ligation (POD7). Male Sprague-Dawley rats were examined for 21 days after undergoing sham operation or spinal nerve ligation to produce allodynia, which was quantified by a lower force of von Frey hairs at the plantar hind paw just required to produce paw withdrawal (paw withdrawal threshold, PWT). Six experimental protocols were followed: rats were infused with lidocaine on POD2 (L2) or on POD7 (L7), or with saline on POD2 (S2) or on POD7 (S7), and sham operated rats were infused with lidocaine on POD2 or on POD7. PWTs were measured during the last 5min of a single 30min lidocaine infusion; at 30, 60, 90, 120, 240 and 360min, and 24, 48 and 72h after beginning infusion, and then every 1-3 days up to 21 days. Three distinct sequential phases of ipsilateral relief were apparent in both L2 and L7 groups: (1) an acute elevation of PWT during the infusion, returning to the pre-infusion allodynic level within 30-60min after infusion; (2) a second, transient elevation of PWT within the next 360min; (3) a sustained elevation of PWT developing slowly over 24h after infusion and maintained over the next 21 days. A significant, although weaker contralateral allodynia developed more slowly (>POD8) than the ipsilateral condition, and could be delayed for more than 2 weeks by lidocaine infusion on POD2 but for only 1 week by the same treatment on POD7. None of the sham operated animals had any allodynic signs and no saline infusions elevated PWT in ligated, allodynic rats. These results of separate phases imply that there are mechanistic differences between the acute relief and the sustained relief of allodynia after a single infusion of lidocaine, and may present an experimental paradigm for investigating the advantages of earlier rather than late therapeutic intervention.

Effect of diltiazem and methylene blue on human sperm motility, viability and cervical mucus penetration: potential use as vas irrigants at the time of vasectomy

The purpose of this study was to identify compounds that could potentially be useful for vas irrigation at the time of vasectomy. We studied the in vitro effects of a group of membrane-active and ion-channel blocking agents on human sperm motility, viability and cervical mucus penetration. Diltiazem, an anti-arrhythmic drug, and methylene blue, an agent commonly used in vasography, showed the most promising effects with marked reduction of sperm motility and cervical mucus penetration after incubation with sperm for a short period of 15 min. Diltiazem was more effective than methylene blue in inhibiting the motility and viability of sperm. Furthermore, unlike methylene blue, diltiazem significantly compromised sperm viability. Other compounds studied, such as lidocaine, nicardipine and Neosporin((R)), showed only partial inhibitory activity. Based on the data reported herein, both diltiazem and methylene blue appear to be suitable candidates to be developed for vas irrigation at the time of vasectomy.

Synaptosomal plasma membrane Ca(2+) pump activity inhibition by repetitive micromolar ONOO(-) pulses

A sustained increase of intracellular free [Ca(2+)] ([Ca(2+)](i)) has been shown to be an early event of neuronal cell death induced by peroxynitrite (ONOO(-)). In this paper, chronic exposure to ONOO(-) has been simulated by treatment of rat brain synaptosomes or plasma membrane vesicles with repetitive pulses of ONOO(-) during at most 50 min, which efficiently produced nitrotyrosine formation in several membrane proteins (including the Ca(2+)-ATPase). The plasma membrane Ca(2+)-ATPase activity at near-physiological conditions (pH 7, submicromolar Ca(2+), and millimolar Mg(2+)-ATP concentrations), which plays a major role in the control of synaptic [Ca(2+)](i), can be more than 75% inhibited by a sustained exposure to micromolar ONOO(-) (e.g., to 100 pulses of 10 microM ONOO(-)). This inhibition is irreversible and mostly due to a decreased V(max), and to the 2-fold increase of the K(0.5) for Ca(2+) stimulation and about 5-fold increase of the K(M) for Mg(2+)-ATP. [Ca(2+)](i) increases to >400 nM when synaptosomes are subjected to this treatment. Reduced glutathione can afford only partial protection against the inhibition produced by micromolar ONOO(-) pulses. Therefore, inhibition of the plasma membrane Ca(2+)-pump activity during chronic exposure to ONOO(-) may account by itself for a large and sustained increase of intracellular [Ca(2+)](i) in synaptic nerve terminals.

Inhibition of the Na,K-ATPase of canine renal medulla by several local anesthetics

The ATPase activity of Na,K-ATPase-enriched membranes from canine renal medulla was determined in the absence of local anesthetic and in the presence of procaine, chloroprocaine, bupivacaine, mepivacaine, lidocaine, and two quaternary derivatives of lidocaine (QX-222 and QX-314) at 37( composite function)C. Chloroprocaine (IC(50)= 13 mM) had slightly greater potency than procaine (IC(50)= 17.7 mM). Bupivacaine (IC(50)= 6.7 mM) was more potent than its congener mepivacaine (IC(50)> 10 mM, the solubility limit). QX-222 (IC(50)> 600 mM) and QX-314 (IC(50)= 132 mM) had less potency than lidocaine (IC(50)= 30.4 mM). This study supports the interpretation that the uncharged forms of local anesthetics are much more potent inhibitors of Na,K-ATPase activity than the cationic forms.

Effects of local anaesthetics on the activity of the Na,K-ATPase of canine renal medulla

The purpose of this study is to characterize the effects of local anaesthetics on Na,K-ATPase activity. The ATPase activity of Na, K-ATPase-enriched membranes from canine renal medulla was determined in the absence and in the presence of lidocaine, procaine, tetracaine, benzocaine, bupivacaine, prilocaine, and procainamide at 37 and 25 degrees C. All of these local anaesthetics, except benzocaine, inhibit the activity of the Na,K-ATPase of canine renal medulla at both 25 and 37 degrees C. Benzocaine inhibits Na,K-ATPase activity at 37 degrees C, but stimulates activity at 25 degrees C. The influence of lidocaine on stimulation of Na,K-ATPase activity by Na(+) and K(+) was investigated. Lidocaine increases the apparent K(0.5) of the Na,K-ATPase for both Na(+) and K(+) and decreases the V(max) values for both ions. IC(50) values for lidocaine increase with increasing concentrations of both Na(+) and K(+). The data indicate that lidocaine diminishes the affinity of the Na,K-ATPase for Na(+) and K(+) and that binding of Na(+) or K(+) decreases the potency of lidocaine as an inhibitor of the Na,K-ATPase. Lidocaine markedly decreases the affinity of the Na,K-ATPase for ouabain, but only slightly diminishes the maximum amount of ouabain bound. Unprotonated lidocaine is apparently a more potent inhibitor than is the protonated form.

Modulation of synaptosomal plasma membrane-bound enzyme activity through the perturbation of plasma membrane lipid structure by bupivacaine

We investigated modulations of lipid dynamics and lipid-protein interactions of rat brain synaptosomal plasma membrane (SPM) as one of the possible mechanisms by which the local anesthetic bupivacaine (BPV) has an adverse effect on nerve cell function, with SPM-bound enzyme activity used as a functional probe. The kinetics of BPV impact on the activity of the endoenzymes Ca2+/Mg2+-stimulated ATPase and Na+/K+-stimulated ATPase and the active concentrations of the drug were relevant to those that produce biphasic systemic toxicity. Arrhenius plots of these enzymes showed a transition temperature of 26.6 +/- 1.8 degrees C and 24.5 +/- 1.2 degrees C (mean +/- SD), respectively, in control SPM, which shifted to 17.1 +/- 0.95 degrees C (P < 0.01) and 18.2 +/- 0.85 degrees C (P < 0.05) in SPM treated with 10(-5) M BPV. The Hill coefficients for the allosteric inhibition of Ca2+/Mg2+-stimulated ATPase by Na+ and Na+/K+-stimulated ATPase by fluoride decreased from 1.73 +/- 0.20 and 1.95 +/- 0.25, respectively, in controls to 0.92 +/- 0.09 (P < 0.001) and 1.09 +/- 0.11 (P < 0.001) in the presence of 10(-5) M BPV. The fluidity perturbation in the microenvironment of the ectoenzyme acetylcholinesterase was observed only at 5 x 10(-3) M BPV, as confirmed by the disparity in transition temperature between the controls (22.3 +/- 1.2 degrees C) and the BPV-treated SPM (17.5 +/- 0.8 degrees C, P < 0.01) and that in the Hill coefficient in the two groups: 2.15 +/- 0.24 and 0.97 +/- 0.12 (P < 0.001), respectively.

IMPLICATIONS

We propose that under physiological conditions, the neutral and protonated forms of local anesthetics can affect nerve cell function through the asymmetric perturbation of the membrane lipid structure, accompanied by synaptosomal plasma membrane-bound enzyme dysfunction.

Hypothalamic hypophyseal inhibitory factor (HHIF) increases intrasynaptosomal free calcium concentration

We have isolated from bovine hypothalamic and pituitary tissues a sodium pump inhibitor that is structurally different from ouabain. By mass spectrometric analysis, this purified factor revealed a single unique molecular ion with an accurate mass of 412.277 and a mass spectra different from that of ouabain. It has been previously shown that this factor inhibits the Ca2+, Mg(2+)-ATPase of the plasma membrane of synaptosomes. Because Ca2+ plays a major role in cellular excitability, we carried out a systematic study of the effects of this inhibitor on the Ca2+ transport processes across the plasma membrane of synaptosomes: We measured ATP-dependent calcium uptake, Na(+)-Ca2+ exchange, and passive permeability using 45Ca2+ and Millipore filtration, chlortetracycline fluorescence, and light-scattering, respectively. This factor inhibits the Na+, K(+)-ATPase activity of the synaptosomal plasma membrane vesicles in the same range of concentrations that produced an increase of intrasynaptosomal free calcium, with nearly the same K0.5 value. In addition, in this concentration range, this factor stimulated 10- to 11-fold the passive flux of Ca2+ and 2.5- to 3-fold the Ca2+ influx via the Na(+)-Ca2+ exchange in these membranes with respect to control values. Measurements of fluorescence anisotropy showed that in this concentration range, the inhibitor did not significantly change the order parameter (fluidity) of these membranes. These results suggest that besides its known inhibition of the sodium pump, this factor could play a role in the control of Ca2+ homeostasis by direct modulation of transport systems implicated in the control of intracellular calcium.

Induction of apoptotic cell death in a neuroblastoma cell line by dibucaine

Dibucaine, a local anesthetic known to interact with cell membranes, induced apoptosis in SK-N-MC human neuroblastoma cells in a dose-dependent manner. Apoptosis was demonstrated by direct visualization of morphological nuclear changes using a DAPI staining technique and confirmed by the production of characteristic ladder patterns of DNA fragmentation on gel electrophoresis. At concentrations which induced apoptosis, dibucaine significantly altered membrane fluidity, indicating that fluidity may be a major target for the cytotoxic action of dibucaine. Also, dibucaine increased intracellular calcium levels more effectively in calcium-containing Krebs-Ringer buffer than in calcium-free Krebs-Ringer buffer. Removal of extracellular calcium or addition of antioxidants or protein synthesis inhibitor effectively blocked dibucaine-induced apoptosis. These results suggest that membrane damage, intracellular calcium levels, and oxygen free radicals may be involved in the apoptosis induced by dibucaine.

Effects of lidocaine on salicylate-induced discharge of neurons in the inferior colliculus of the guinea pig

Using the extracellular recording method, the effects of lidocaine (a local anesthetic known to relieve tinnitus) on discharge of inferior colliculus (IC) neurons of the guinea pig were studied before and after salicylate (200 mg/kg) administration. The salicylate-induced discharge was inhibited by intravenous injection of lidocaine at a concentration (1 mg/kg) clinically used for treating tinnitus. IC neurons could be classified into two groups according to the difference in sensitivity to lidocaine: (1) weakly-sensitive neurons and (2) highly-sensitive neurons. In weakly-sensitive neurons, the duration of the lidocaine effect lasted for less than 5 min, and the inhibitory action on the discharge of neurons was greater when the latency to sound stimulus became longer. In highly-sensitive neurons, on the other hand, the activity of neurons was almost completely inhibited for longer than 30 min, irrespective of the latency to sound stimulus. The clinical relevance of these types of neurons is discussed.

Rate of Na+/Ca2+ exchange across the plasma membrane of synaptosomes measured using the fluorescence of chlorotetracycline. Implications to calcium homeostasis in synaptic terminals

It is shown that the fluorescence of chlorotetracycline (CTC) can be used to continuously monitor Ca2+ fluxes mediated by the Na+/Ca2+-exchanger of the plasma membrane of synaptosomes. The kinetics of Ca2+ uptake can be followed from the kinetics of the increase of CTC fluorescence with external Ca2+ concentrations in the micromolar range. Since the fluorescence of CTC is not sensitive to Ca2+ concentration below 20 microM this avoids any significant contribution of Ca2+ flux through Ca2+ channels to CTC fluorescence. By replacing KCl by choline chloride in the buffer to avoid plasma membrane depolarization it is shown that the amplitude of the CTC fluorescence change is dependent upon the Na(+)-gradient preimposed across the plasma membrane, and the rate constant of the kinetic process is dependent upon the Ca2+ concentration. The rate constant of the Ca2+ influx measured with depolarized and non-depolarized synaptic plasma membrane vesicles at 37 degrees C and pH 7.4 were 0.55 +/- 0.10 and 0.25 +/- 0.02 min-1, respectively. The overall rate of Na+/Ca2+ exchange calculated under conditions close to physiological Na+ and Ca2+ gradients and membrane resting potential ranged from 15 to 25% of the activity of the plasma membrane Ca2+ pump under these experimental conditions. The results also point out that membrane depolarization increases approx. 2-fold the rate of Na+/Ca2+ exchange in synaptic plasma membrane vesicles.

Modulation of the Ca2+ pump by the hypothalamic-hypophysary inhibitory factor

We previously purified to homogeneity an endogenous sodium pump inhibitor from bovine hypothalamus and hypophysis that is different from digoxin or ouabain and studied the effects of this factor on the total Ca2+,Mg(2+)-ATPase activity of plasma membrane of synaptosomes. This factor inhibits the calcium pump and the total Mg(2+)-ATPase activity of these membranes with approximately the same K0.5 values of inhibition. The potency of this factor as an inhibitor depends on the membrane concentration in the assay medium. The inhibition of the magnesium-dependent ATPase activities of these membranes was of a noncompetitive type with respect to the substrate Mg(2+)-ATP and did not significantly shift the calcium dependence of the Ca2+,Mg(2+)-ATPase activity. We suggest that the calcium pump of the synaptosomal plasma membrane is inhibited by this factor through disruption of the lipid annulus; this inhibition could play a role in the control of calcium homeostasis by increasing the cytosolic free calcium concentration.

Involvement of phospholipase A2 and arachidonic acid in the depolarization-evoked accumulation of Ca2+ in hippocampal mossy fiber nerve endings

Depolarization-evoked increases in intraterminal free Ca2+ are required for the induction of neurotransmitter release from nerve terminals. Although the mechanisms that regulate the voltage-induced accumulation of presynaptic Ca2+ remain obscure, there is evidence that the phospholipase-dependent accumulation of arachidonic acid, or its metabolites, may be involved. Therefore, fura-2 loaded hippocampal mossy fiber nerve endings were used to investigate the relationships between membrane depolarization, lipid metabolism and presynaptic Ca2+ availability. It was observed that depolarization of the nerve terminals with KCl induced an increase in intraterminal free calcium that was inhibited more than 90% by a combination of voltage-sensitive Ca2+ channel blockers. In addition, the K(+)-dependent effects on Ca2+ concentrations were attenuated in the presence of phospholipase A2 inhibitors, but were mimicked by the phospholipase A2 activator melittin and exogenous arachidonic acid. Both the melittin- and arachidonic acid-induced increases in presynaptic Ca2+ were reduced by voltage-sensitive Ca2+ channel blockers. The stimulatory effects of arachidonic acid appeared to be independent of its further metabolism to prostaglandins. In fact, inhibition of either cyclooxygenase or lipoxygenase pathways resulted in a potentiation of the depolarization-evoked increase in intraterminal free Ca2+. From these results, we propose that some portion of the depolarization-evoked increase in intraterminal free calcium depends on the activation of phospholipase A2 and the subsequent accumulation of unesterified arachidonic acid.

The effect of lidocaine on growth of cells of head and neck squamous cell carcinoma

The effect of lidocaine on the growth rate of human squamous cell carcinoma of the head and neck area was investigated in tissue culture. As growth parameters, the mean cell area, the total cell area, the field area and the total number of cells have been measured by digital image analysis. The carcinoma's two cell types--round and spindle--were recorded separately to verify different patterns of alteration. All parameters did not decrease significantly when lidocaine was given as a single dose prior to the culture. A significant decrease (p < 0.05) at day 6, 9 and 12 in culture was found when lidocaine (7 micrograms ml-1) was added to the culture medium.

Changes in intracellular free calcium during hyperthermia: effects of local anesthetics and induction of thermotolerance

We wished to determine if local anesthetics (LAs) induced changes in intracellular free calcium ([fCa2+i]) that could have an effect on cell killing by hyperthermia. Flow cytometry was used to measure [fCa2+i] of mouse NIH 3T3 cells during heating at 45.5 degrees C. In both non-tolerant and thermotolerant cells, heating caused a rapid increase (within 1 min) in [fCa2+i] of approximately 100 nM, which remained relatively constant during 25 min of continued heating; however, survival was higher in thermotolerant cells. Procaine, lidocaine, and tetracaine had no effect on survival or [fCa2+i] of cells kept at 37 degrees C up to 25 min. Cells heated with procaine and lidocaine showed no difference in [fCa2+i] compared to cells heated without LAs but were greatly sensitized to killing. Cells heated with tetracaine became permeable to trypan blue within 10-15 min of heating. We conclude that heat sensitization by LAs does not involve changes in [fCa2+i]. Furthermore, these studies reject the hypothesis that changes in [fCa2+i] are involved in heat-induced cell killing.

Experimental basis for lidocaine therapy in cochlear disorders

In order to further our basic understanding of the effects of lidocaine hydrochloride in the inner ear, cochlear potentials and blood flow (CBF) were assessed after intravenous (i.v.), anterior inferior cerebellar artery (AICA), and local round window (RW) lidocaine administrations in guinea pigs and rats. Lidocaine RW applications produced a dose dependent decrease in compound action potentials (CAP) and cochlear microphonics (CM). The sensitivity changes were more pronounced at high frequencies. These findings suggest that lidocaine has specific pharmacological action in the inner ear other than simple anesthesia of the auditory nerve. The basal turn endocochlear potentials (EP) were not altered by topical lidocaine, implicating altered organ of Corti function following local application of lidocaine. RW applications of lidocaine had no effect on CBF or systemic blood pressure (BP). I.v. infusions caused substantial reductions in BP. In the case of systemic infusions the percent changes in CBF were equal to and accountable by the BP changes. The microinfusions (50 mg/ml, 100 nl/min) through AICA produced a 30%, long lasting increase in CBF. However, neither systemic lidocaine nor AICA infusions had an effect on CAP or CM. These findings indicate that systemically given lidocaine may not cross the blood-cochlear barrier and that the cochlear electrophysiological effects due to lidocaine when given locally are partly mediated by direct influence on cochlear hair cell function; they also suggest that lidocaine-induced interference with active ion transport in the lateral wall or an influence on CBF are not contributing factors.