Tertiary Amine Local Anesthetics Research Articles

Effect of tertiary amine local anesthetics on G protein-coupled receptor lateral diffusion and actin cytoskeletal reorganization

Although widely used clinically, the mechanism underlying the action of local anesthetics remains elusive. Direct interaction of anesthetics with membrane proteins and modulation of membrane physical properties by anesthetics are plausible mechanisms proposed, although a combination of these two mechanisms cannot be ruled out. In this context, the role of G protein-coupled receptors (GPCRs) in local anesthetic action is a relatively new area of research. We show here that representative tertiary amine local anesthetics induce a reduction in two-dimensional diffusion coefficient of the serotonin1A receptor, an important neurotransmitter GPCR. The corresponding change in mobile fraction is varied, with tetracaine exhibiting the maximum reduction in mobile fraction, whereas the change in mobile fraction for other local anesthetics was not appreciable. These results are supported by quantitation of cellular F-actin, using a confocal microscopic approach previously developed by us, which showed that a pronounced increase in F-actin level was induced by tetracaine. These results provide a novel perspective on the action of local anesthetics in terms of GPCR lateral diffusion and actin cytoskeleton reorganization.

Addition of Capsaicin to Local Anesthetics for Spinal Anesthesia in Rats Shortens Motor Deficits and Prolongs Anti-Nociception

Background and Objectives: Sensory-selective anesthesia, greater or longer-lasting anti-nociception than motor or autonomic deficits, is often clinically desirable but traditional local anesthetics rarely have such selective actions. Addition of capsaicin to tertiary amine local anesthetics has recently been reported to affect a preferential prolongation of nociceptive over motor block in rat sciatic nerve. We hypothesized that this combination when used intrathecally will also prolong nociceptive block. Methods: Under sevoflurane inhalation anesthesia, rats were injected intrathecally either with local anesthetics (bupivacaine, lidocaine, and articaine) alone or simultaneously with capsaicin. Motor block was evaluated by the contractile function of foot muscles, from proximal to distal. Anti-nociception was assessed by reductions in nocifensive withdrawal and vocalization induced by pinching the skin fold over the lateral metatarsus. Durations and degrees of deficits were assessed, along with complete recovery times and compared between local anesthetics alone and in combination with capsaicin. Results: Addition of capsaicin to any of the local anesthetics shortened motor deficits. Bupivacaine, lidocaine and articaine motor blocks were reduced upon combination with capsaicin to 0.32, 0.32 ans 0.43 of the duration from the respective local anesthetic alone. Duration of anti-nociceptive action was increased by capsaicin only for articaine. The ratios of block nociceptive to sensory block durations were 3.5, 5.1 and 3.3 for the respective local anesthetics. Conclusions: Intrathecal injection of capsaicin combined with local anesthetics produced a preferentially longer anti-nociceptive deficit. These combinations have potential clinical applications, including peri-operative spinal anesthesia and pain management.

A Comparative Evaluation of Local Application of the Combination of Eutectic Mixture of Local Anesthetics and Capsaicin for Attenuation of Venipuncture Pain

Topical capsaicin and eutectic mixture of local anesthetics (EMLA) have been found to be equally effective in minimizing the pain of venipuncture. After the injection of capsaicin, both tertiary amine local anesthetics and their quaternary ammonium derivatives can elicit a prolonged and predominantly sensory/nociceptor selective block. We hypothesized that the combined application of capsaicin and ELMA will be more effective than their individual effect, and lower concentrations of individual drugs in this mixture may also be associated with reduced side effects. One hundred twenty patients were randomized into 4 equal groups. The control group received plain lubricant cream; the EMLA group received EMLA cream; the capsaicin group received Myolaxin ointment (containing oleoresin capsaicin equivalent to capsaicin 0.075% w/w, methylsalicylate IP 20% w/w, menthol IP 10% w/w, camphor USP 5% w/w, and eucalyptus oil IP 5% w/w); and the EMLA + capsaicin group received EMLA cream and Myolaxin ointment mixed in equal amounts. An anesthesiologist applied the cream to a 10-cm(2) area (site of venous cannulation) on the dorsum of the nondominant hand of the patient 1 hour before venipuncture and covered the area with an occlusive transparent dressing. Venipuncture was performed with an 18-gauge cannula after removing the dressing. Venipuncture pain was graded by the patient on a 0 to 10 visual analog scale, where 0 means no pain and 10 means worst imaginable pain. P values (after correction for multiple comparisons) of <0.05 were considered significant. The incidence of no pain on venous cannulation (primary end point) was 0% in the control group (0/30). The incidence of no pain were significantly higher in the EMLA group (32%, 9/28, 95% corrected confidence interval for the difference 12%-57%, P = 0.0025), capsaicin group (30%, 9/30, 10%-53%, P = 0.0031), and EMLA + capsaicin groups (47%, 14/30, 25%-69%, P < 0.0001). Severity of venipuncture pain as assessed by visual analog scale median (interquartile range) was lower in the EMLA + capsaicin group 1 (2) compared with other groups 3 (1), 1.5 (3), and 1.5 (3) for control, EMLA, and capsaicin, respectively (P < 0.001, P = 0.04, and P = 0.04, respectively). We observed that the combination of capsaicin and EMLA in a low concentration is as effective in managing venous cannulation as when applied as an individual drug alone. Larger studies with varying concentration of capsaicin and EMLA are recommended to more fully evaluate the potential advantages.

Capsaicin Combined with Local Anesthetics Preferentially Prolongs Sensory/Nociceptive Block in Rat Sciatic Nerve

Transient receptor potential vanilloid 1 channels integrate nociceptive stimuli and are predominantly expressed by unmyelinated C-fiber nociceptors, but not low-threshold mechanoreceptive sensory or motor fibers. A recent report showed that the transient receptor potential vanilloid 1 channel agonist capsaicin allows a hydrophilic quaternary ammonium derivative of lidocaine, QX-314, to selectively block C fibers without motor block. The authors tested whether a similar differential block would be produced using amphipathic N-methyl amitriptyline, amitriptyline, bupivacaine, or lidocaine, either alone or together with 0.05% capsaicin, in a rat sciatic nerve block model. Rats (n = 8/group) were anesthetized with sevoflurane, and 0.2 ml of drug was injected either alone or with capsaicin (simultaneously or 10 min later) next to the sciatic nerve in the sciatic notch. Motor function was assessed by the extensor postural thrust. Nociception was evaluated by the nocifensive withdrawal reflex and vocalization evoked by pinch of a skin fold over the lateral metatarsus (cutaneous pain) with a serrated forceps. N-Methyl amitriptyline, amitriptyline, bupivacaine, or lidocaine, followed by injection of capsaicin 10 min later, each elicited a predominantly nociceptive-specific blockade. In comparison, simultaneous application of each local anesthetic with capsaicin did not elicit a clinically significant differential block, with the exception of N-methyl amitriptyline. Both tertiary amine local anesthetics and their quaternary ammonium derivatives can elicit a predominantly sensory/nociceptor selective block when followed by injection of capsaicin. The combined application of transient receptor potential vanilloid 1 channel agonists and various local anesthetics or their quaternary ammonium derivatives is an appealing strategy to achieve a long-lasting differential block in regional analgesia.

Interaction of Serotonin1AReceptors from Bovine Hippocampus with Tertiary Amine Local Anesthetics

1. We have examined the interaction of tertiary amine local anesthetics with the bovine hippocampal serotonin1A (5-HT1A) receptor, an important member of the G-protein-coupled receptor superfamily. 2. The local anesthetics inhibit specific agonist and antagonist binding to the 5-HT1A receptor at a clinically relevant concentration range of the anesthetics. This is accompanied by a concomitant reduction in the binding affinity of the 5-HT1A receptor to the agonist. Interestingly, the extent of G-protein coupling of the receptor is reduced in the presence of the local anesthetics. 3. Fluorescence polarization measurements using depth-dependent fluorescent probes show that procaine and lidocaine do not show any significant change in membrane fluidity. On the other hand, tetracaine and dibucaine were found to alter fluidity of the membrane as indicated by a fluorescent probe which monitors the headgroup region of the membrane. 4. The local anesthetics showed inhibition of agonist binding to the 5-HT1A receptor in membranes depleted of cholesterol more or less to the same extent as that of control membranes in all cases. This suggests that the inhibition in ligand binding to the 5-HT1A receptor brought about by local anesthetics is independent of the membrane cholesterol content. 5. Our results on the effects of the local anesthetics on the ligand binding and G-protein coupling of the 5-HT1A receptor support the possibility that G-protein-coupled receptors could be involved in the action of local anesthetics.

Influence of local anesthetics on the phosphatidylcholine model membrane: small-angle synchrotron X-ray diffraction and neutron scattering study

The phase preferences of egg yolk phosphatidylcholine (EYPC) have been examined in the presence of tertiary amine anesthetics [2-(propyloxy)phenyl]-2-(1-piperidinyl)ethyl ester of carbamic acid (C3A) and [2-(heptyloxy)phenyl]-2-(1-piperidinyl)ethyl ester of carbamic acid (C7A, heptacaine). Using the synchrotron small-angle X-ray diffraction (SAXD), it is shown that the C3A anesthetic induces the cubic and hexagonal ( H I) phases at 2≥C3A:EYPC>0.5 and H 2O:EYPC≤40 molar ratios. In contrast, longer alkyloxy chain homolog C7A has no effect on the bilayer arrangement of EYPC at C7A:EYPC≤1 molar ratios as observed by SAXD in C7A+EYPC mixtures hydrated at H 2O:EYPC≤40 molar ratios, as well as in sonicated C7A+EYPC mixtures hydrated in excess water as proved by the small-angle neutron scattering (SANS). The bilayer thickness d L decreases and the bilayer C7A surface area S C7A increases with the increase of C7A:EYPC molar ratio. It is suggested that the ability of tertiary amine local anesthetics to influence the d L and S C7A values and EYPC polymorphism is caused by their effective molecular shape and by charge. The possibility that anesthetic molecules may exert some of their biological effects by virtue of these properties is discussed.

Cardiotoxic and antiarrhythmic tertiary amine local anesthetics: sodium channel affinity vs. sodium channel gating.

Tertiary amine local anesthetics (LAs) are clinically valuable agents for controlling pain and for treating some cardiac arrhythmias. These drugs inhibit conduction of electrical activity by blocking voltage-gated sodium channels. Interestingly, LAs can influence the conduction of electrical activity in heart muscle without markedly altering normal skeletal muscle activity. This review discusses the interactions between sodium channels and LAs, the methods used to investigate these interactions, and the mechanisms proposed to explain the greater LA sensitivity of cardiac sodium channels as compared with skeletal muscle sodium channels.

Photophysical Study of Local Anesthetics in Reverse Micelles and Water-Ethanol Mixtures

Fluorescence emission from three tertiary amine local anesthetics, dibucaine (D), tetracaine (T), and procaine (P) was investigated in the membrane-mimetic environment of AOT/isooctane reverse micelles and water-ethanol mixtures. At room temperature all three show broad UV absorption bands and large Stokes' shifts in emission from aqueous medium. In reverse micelles the emission bands are blue-shifted, with the magnitude of this shift decreasing continuously as the waterto-surfactant molar ratio (w0) of the micelles is increased. The emission intensity of D is much stronger in water and in the interior of micelles than in ethanol, whereas for T and P the emission in water is much weaker than in ethanol and in micelles. Whereas the behavior in micelles is the result of the increased hydrophobicity with respect to bulk water in their interior, that in waterethanol mixtures may be explained on the basis of state reversal of the excited electronic levels of D with increasing hydrogen bonding capability of the solvent mixture. The steady-state anisotropy for both T and P is unusually high in bulk water (∼0.27) and increases with increasing w0 in micelles. However, the rotational correlation time of the anesthetics, as calculated using Perrin's equation, decreases with increasing w0, as expected from physical considerations relating the size of the water pool to the ease of rotational relaxation of probe molecules inside micelles. Together, these results point to a marked difference in emission properties between D on one hand and T and P on the other, arising from differences in electronic characters of their primary emitting chromophores—quinoline for D, para amino benzoate for T and P.

Carboxyl groups at the membrane interface as molecular targets for local anesthetics

The interaction of the tertiary amine drugs chlorpromazine and dibucaine in their cationic form with carboxyl groups at the membrane surface is studied at concentrations relevant to anesthesia. Spin-labeled stearic acid is used both to provide the carboxyl groups and to monitor binding and ionization behavior in egg lecithin liposomes. Membrane anesthetic concentrations are spectrophotometrically obtained. They are shown to determine the drug influence on carboxyl groups at the membrane surface, independently of aqueous concentrations. The intramembrane association constants (related to the usual aqueous phase ones through the partition coefficient) of the drugs with fatty acids are determined. The same value (10 2 M −1) is obtained for both drugs, suggesting that it is approximately the same for all tertiary amine local anesthetics. pH titrations of anesthetic-treated spin-labeled membranes are performed. The observed shifts in the fatty acid p K are higher than can be produced assuming uniform distribution of the drug in the membrane surface, implying that there is an increased affinity of local anesthetics for superficial carboxyl. This affinity could account for the resting block of voltage-gated Na + channels. Under these considerations, local anesthetic binding sites at voltage-gated Na + channels and at sarcoplasmic reticulum Ca 2+-ATPase are proposed.

Theoretical studies on local anesthetics: Procaine, lidocaine, tetracaine, bupivacaine, and dibucaine—neutral and monoprotonated

The molecular basis of the pharmacological action of tertiary amine local anesthetics (LA) is still unclear. However, there is experimental evidence that the LA penetrates into the axon as a neutral form and acts in the charged form from the intracellular phase. In this work we report quantum chemical semiempirical results for the neutral and monoprotonated forms of procaine, lidocaine, tetracaine, bupivacaine, and dibucaine. All geometries have been fully optimized with the AM1 Hamiltonian. Solvent effects were included at the self-consistent reaction field (SCRF) approximation. We have found that the most stable conformers of positively charged LA agents are all characterized by intramolecular H-bond formation involving the protonated amine groups. INDO/S-CIS calculations have revealed that the gas-phase absorption spectra of LAs result from the superposition of the spectra of the ring π system and the carbonyl, in a large extent perturbed by intramolecular charge transfer (CT). For all studied LAs, the benzene B2u bands are very weak and the benzene B1u bands gain intensity due to symmetry breaking. Formation of intramolecular H bond strongly affects the carbonyl CT bands. On the other hand, the spectrum of dibucaine is dominated by the quinoline π system. © 1997 John Wiley & Sons, Inc.

Theoretical studies on local anesthetics: Procaine, lidocaine, tetracaine, bupivacaine, and dibucaine?neutral and monoprotonated

The molecular basis of the pharmacological action of tertiary amine local anesthetics (LA) is still unclear. However, there is experimental evidence that the LA penetrates into the axon as a neutral form and acts in the charged form from the intracellular phase. In this work we report quantum chemical semiempirical results for the neutral and monoprotonated forms of procaine, lidocaine, tetracaine, bupivacaine, and dibucaine. All geometries have been fully optimized with the AM1 Hamiltonian. Solvent effects were included at the self-consistent reaction field (SCRF) approximation. We have found that the most stable conformers of positively charged LA agents are all characterized by intramolecular H-bond formation involving the protonated amine groups. INDO/S-CIS calculations have revealed that the gas-phase absorption spectra of LAs result from the superposition of the spectra of the ring π system and the carbonyl, in a large extent perturbed by intramolecular charge transfer (CT). For all studied LAs, the benzene B2u bands are very weak and the benzene B1u bands gain intensity due to symmetry breaking. Formation of intramolecular H bond strongly affects the carbonyl CT bands. On the other hand, the spectrum of dibucaine is dominated by the quinoline π system. © 1997 John Wiley & Sons, Inc.

Direct inhibition of the actomyosin motility by local anesthetics in vitro

Using a recently developed in vitro motility assay, we have demonstrated that local anesthetics directly inhibit myosin-based movement of single actin filaments in a reversible dose-dependent manner. This is the first reported account of the actions of local anesthetics on purified proteins at the molecular level. In this study, two tertiary amine local anesthetics, lidocaine and tetracaine, were used. The inhibitory action of the local anesthetics on actomyosin sliding movement was pH dependent; the anesthetics were more potent at higher pH values, and this reaction was accompanied by an increased proportion of the uncharged form of the anesthetics. QX-314, a permanently charged derivative of lidocaine, had no effect on actomyosin sliding movement. These results indicate that the uncharged form of local anesthetics is predominantly responsible for the inhibition of actomyosin sliding movement. The local anesthetics inhibited sliding movement but hardly interfered with the binding of actin filaments to myosin on the surface or with actomyosin ATPase activity at low ionic strength. To characterize the actomyosin interaction in the presence of anesthetics, we measured the binding and breaking force of the actomyosin complex. The binding of actin filaments to myosin on the surface was not affected by lidocaine at low ionic strength. The breaking force, measured using optical tweezers, was approximately 1.5 pN per micron of an actin filament, which was much smaller than in rigor and isometric force. The binding and breaking force greatly decreased with increasing ionic strength, indicating that the remaining interaction is ionic in nature. The result suggests that the binding and ATPase of actomyosin are governed predominantly by ionic interaction, which is hardly affected by anesthetics; whereas the force generation requires hydrophobic interaction, which plays a major part of the strong binding and is blocked by anesthetics, in addition to the ionic interaction.

Kinetic analysis of phasic inhibition of neuronal sodium currents by lidocaine and bupivacaine

Phasic ("use-dependent") inhibition of sodium currents by the tertiary amine local anesthetics, lidocaine and bupivacaine, was observed in voltage-clamped node of Ranvier of the toad, Bufo marinus. Local anesthetics were assumed to inhibit sodium channels through occupation of a binding site with 1:1 stoichiometry. A three-parameter empirical model for state-dependent anesthetic binding to the Na channel is presented: this model includes two discrete parameters that represent the time integrals of binding and unbinding reactions during a depolarizing pulse, and one continuous parameter that represents the rate of unbinding of drug between pulses. The change in magnitude of peak sodium current during a train of depolarizing pulses to 0 mV was used as an assay of the extent of anesthetic binding at discrete intervals; estimates of model parameters were made by applying a nonlinear least-squares algorithm to the inhibition of currents obtained at two or more depolarizing pulse rates. Increasing the concentration of drug increased the rate of binding but had little or no effect on unbinding, as expected for a simple bimolecular reaction. The dependence of the model parameters on pulse duration was assessed for both drugs: as the duration of depolarizing pulses was increased, the fraction of channels binding drug during each pulse became significantly larger, whereas the fraction of occupied channels unbinding drug remained relatively constant. The rate of recovery from block between pulses was unaffected by pulse duration or magnitude. The separate contributions of open (O) and inactivated (I) channel binding of drug to the net increase in block per pulse were assessed at 0 mV: for lidocaine, the forward binding rate ko was 1.3 x 10(5) M-1 s-1, kl was 2.4 x 10(4) M-1 s-1; for bupivacaine, ko was 2.5 x 10(5) M-1 s-1, kl was 4.4 x 10(4) M-1 s-1. These binding rates were similar to those derived from time-dependent block of maintained Na currents in nodes where inactivation was incomplete due to treatment with chloramine-T. The dependence of model parameters on the potential between pulses (holding potential) was examined. All three parameters were found to be nearly independent of holding potential from -70 to -100 mV. These results are discussed with respect to established models of dynamic local anesthetic-Na channel interactions.

Mechanism of local anesthetic effect on mitochondrial ATP synthase as deduced from photolabelling and inhibition studies with phenothiazine derivatives

The mode of interaction between mitochondrial ATP synthase and two phenothiazine derivatives, chlorpromazine (CPZ) and trifluoperazine (TFP), was studied as a model for the interaction of local anesthetic drugs with membrane proteins. Photolabelling experiments demonstrated that CPZ and TFP interact with various subunits of either the peripheral F 1 moiety or the membrane-embedded F 0 sector. Both drugs, however, labelled the membrane sector much more heavily. Qualitative differences in labelling were observed between CPZ and TFP, indicating non-identical sites of interaction. These diversities appeared related to the different hydrophobicities of the two drugs since: (a) TFP, which has a higher lipid/water partition coefficient, labelled the more hydrophobic subunits more markedly than CPZ; (b) reduced glutathione, a hydrophilic free radical scavenger that does not penetrate the membrane continuum, had a negligible effect on the labelling by TFP, whereas it reduced the labelling of various subunits by CPZ; (c) the labelling by [ 3H]TFP was poorly antagonized by cold CPZ, whereas it was almost totally prevented by fluphenazine, a phenothiazine similar to TFP in hydrophobic character. Consistently, double-inhibition experiments showed that TFP and fluphenazine are mutually exclusive inhibitors of mitochondrial ATP synthase, whereas TFP and CPZ are mutually nonexclusive. The nature of the phospholipid bilayer influenced neither the labelling nor the inhibition patterns. The complex of these data indicate that tertiary amine local anesthetics affect the activity of membrane proteins by interacting with a multiplicity of relatively aspecific hydrophobic sites located preferentially, but not exclusively, on the membrane-embedded domains. It is suggested that at least two phenothiazine derivatives of different hydrophobicities be used in photolabelling experiments, before any generalization is made, since the molecular targets of these drugs vary according to their hydrophobic character.

PHOTOPHYSICAL STUDIES OF LOCAL ANESTHETICS, TETRACAINE and PROCAINE: DRUG AGGREGATIONS

The effects of solvent and concentration on the photophysical properties of tertiary amine local anesthetics, tetracaine and procaine were studied experimentally using low temperature (77 K) emission spectroscopy and confirmed theoretically using a HAM/3 method. For tetracaine free base in methylcyclohexane, a broad fluorescence band observed at approximately 375 nm for concentrations greater than 1 x 10(-3) M is assigned to the molecular self-associated species. The disappearance of this band in ethanol (i.e. a model hydrophobic environment) indicates a greater tendency of neutral tetracaine towards molecular hetero-association. In an aqueous solution of procaine.HCl, a broad emission band centered at approximately 400 nm is detected even at a concentration as low as 1 x 10(-4) M and is attributed to the charged aggregates of procaine.HCl. Two general observations for procaine, tetracaine and dibucaine are noted: (1) the monocation and free base local anesthetics in ethanol solutions give identical photophysical properties, suggesting that the monocation drug species in ethanol is H+ dissociative, and (2) the lowest singlet excited state of neutral local anesthetics is calculated to have a charge-transfer character originating from a non-bonding electron in the N of tertiary amine group to the pi orbital of aromatic ring. The possible pharmacological implications of the deprotonation, the drug aggregations and the charge-transfer excitations of local anesthetics on the molecular basis of anesthesia are discussed.

Mechanism of local anesthetic effect. Involvement of F 0 in the inhibition of mitochondrial ATP synthase by phenothiazines

The mechanism whereby tertiary amine local anesthetics affect the activity of membrane proteins was investigated by studying the interaction of phenothiazines with mitochondrial ATP synthase. These drugs caused inhibition of the activity of the membrane-bound enzyme at concentrations that do not perturb the phospholipid bilayer. The inhibitory effect appeared consequent to interaction with multiple sites located on both the F 1 and the F 0 components of the enzyme complex, since: (a) Dixon plots were parabolic; (b) the membrane-bound enzyme was more sensitive to the drug effect than the isolated F 1 component; (c) conditions that decreased oligomycin sensitivity also decreased the sensitivity to phenothiazines; (d) irreversible binding of photochemically activated phenothiazines to the ATP synthase complex, followed by detachment of the F 1 moiety and reconstitution with purified F 1 resulted in an inhibited enzyme complex. These data are interpreted as indicating that tertiary amine local anesthetics affect the activity of membrane proteins by interacting with hydrophobic sites located on both their integral and peripheral domains.

Pheromone interactions and ionic communication in gametes of aquatic fungusAllomyces macrogynus

The flagellate male and female gametes of the aquatic fungusAllomyces macrogynus are each attracted to a sexual pheromone produced by the opposite gamete type. The sperm attractant, sirenin, causes chemotaxis to female gametes. Examination of sperm chemotaxis shows that the pheromone influences the frequency of directional changes and the duration of a chemotactic run. Physiological experiments using tertiary amine local anesthetics or calcium chelators such as EGTA demonstrate that sirenin stimulates the influx of calcium ions (Ca(2+)) into the sperm cytoplasm. Radiological experiments with(45)CaCl2 have demonstrated this calcium flux directly. Structurally, sirenin is an oxygenated sesquiterpene that consists of a cyclopropyl ring attached onto an isohexenyl side chain. The pheromone displays a threshold concentration for attraction at 10 pM in chemotaxis bioassays. Structure-activity relationships with racemic sirenin and sirenin analogs indicate that biological activity requires a terminal hydroxymethyl group on the side chain. In addition, a hydrophobic group must be present at the other end of the sirenin molecule. Besides sirenin, the sperm cells ofA. macrogynus produce a female attractant, parisin. While the molecular nature of this attractant is not completely resolved, some general features of the molecule suggest it may be similar structurally to sirenin.

Destabilization of herpes simplex virus type 1 virions by local anesthetics, alkaline pH, and calcium depletion

The infectivity of herpes simplex virus type 1 (HSV-1) was found to be markedly reduced by treating virions with the tertiary amine local anesthetics lidocaine, dibucaine and tetracaine. These treatments induced a characteristic shift in the buoyant density of the HSV-1 particles from a "light" to a "heavy" population. HSV-1 virions were unstable at alkaline pH, and alkali treatment caused the same shift in buoyant density. Ca2+ stabilized the "light" population. These results suggest that the physicochemical status of the HSV-1 envelope which is sensitive to the treatments described above plays an important role for the integrity of the virion.

局所麻酔剤の好中球機能に及ぼす影響について

We investigated the effects of tertiary amine local anesthetics (LA, procaine and lidocaine) on human neutrophil functions. For this purpose, the effects of LA on chemotaxis, phagocytosis and O2- production were estimated At concentrations of O.0125 percent or more, significant reduction of neutrophil chemotxis were observed, using zymosan treated serum as a chemoattractant. This inhibitory effect of LA was reversible and chemotactic ability was recovered after washing out of LA. Neutrophil phagocytosis and O2- production were also inhibited by LA, but 10 and 100 times concentrations of LA were required to inhibit them respectively.

Inhibition of human serum and rabbit muscle cholinesterase by local anesthetics

The effects of tertiary amine local anesthetics (procaine, mepivacaine, lidocaine, tetracaine, dibucaine, and bupivacaine) and chlorpromazine were investigated for rabbit muscle acetylcholinesterase and human serum cholinesterase. The muscle enzyme was poorly inhibited by local anesthetics containing an amide linkage. The serum cholinesterase was inhibited by all those compounds, their relative potencies being proportional to their octanol/water partition coefficients. The dissociation constants of tetracaine and procaine, ester anesthetics, were 1000-fold and 100-fold, respectively, that which would be expected from their partition coefficient basis respective to the other amide anesthetics. Procaine showed competitive inhibition of serum cholinesterase, whereas for most anesthetics a mixed type of inhibition was observed. Procaine probably binds at the main anionic site, while the other positively charged anesthetics bind to either the catalytic centre or to the peripheral or modulator anionic site, modifying the kinetic behaviour of cholinesterase as has been demonstrated by the appearance of negative cooperativity for binding to the substrate.