Membrane properties and lipid peroxidation in food restricted animals

Food restriction (FR) is a well-recognized method of extending mean and maximum longevity of rodents, but the mode of its action remains to be uncovered. This article reviews the effect of FR on the physical-chemical properties and lipid peroxidizability of cellular membranes. FR prevents the age-dependent increase in microviscosity and peroxidizability of cellular membranes. It has been suggested that a decrease in the body temperature occurring in undernourished animals may play a fundamental role in the process. Indeed, the lowering of average body temperature occurring in FR animals may induce a modification in membrane lipid composition, stimulating the cells to counteract the rigidifying effect of lower temperature. Thus, membranes are maintained in a proper functional state by a mechanism similar to that found in poikilotherm animals.

Dynamic receptor superstructures at the plasma membrane

1. INTRODUCTION 68

1.1 Receptor patterns in the plasma membrane 68

1.2 Different types of receptor patterns 71

2. METHODS TO INVESTIGATE NON-RANDOM RECEPTOR CLUSTERING 73

2.1 Fluorescence resonance energy transfer 73

2.2 Flow cytometric energy transfer measurement 78

2.3 Fluorescence anisotropy and energy transfer 79

2.4 Photobleaching energy transfer on single cells 81

2.5 Two-dimensional mapping of receptor superstructures 82

2.6 Detecting single receptor molecules 85

2.7 Chemical identification of receptor clusters 86

2.8 Electron microscopy 87

2.9 Scanning force microscopy 88

3. CONFORMATIONAL STATES OF RECEPTORS 90

3.1 Multi-subunit receptor structures 90

3.2 Physical parameters influencing conformational states 91

3.3 Chemical interactions and receptor conformations 92

4. ON THE ORIGIN OF NATURALLY OCCURRING RECEPTOR CLUSTERS 93

4.1 Synthesis of receptors and their localization in the plasma membrane 93

4.2 Lipid domain structure of the plasma membrane 94

4.3 The validity of the Singer–Nicolson model 94

5. CONCLUSIONS 96

6. ACKNOWLEDGEMENTS 96

7. REFERENCES 97

Dietary restriction affects antioxidant levels in rat liver mitochondria during ageing

Six experimental groups of young (7-month-old) and aged (24-32-month-old) rats, underwent different dietary manipulations (i.e. dietary restriction and/or a vitamin E-depleted diet), and their liver mitochondria were assayed for several antioxidants and peroxidation markers. Glutathione levels were affected both by age and dietary treatment. Coenzyme Q9 and C0Q10 showed the highest levels in the oldest rats where ageing, as well as other oxidative stresses, could induce ubiquinone biosynthesis.

Effect of acetylcholine on the electrophysiology and proliferative response of human lymphocytes

Using the patch-clamp technique, we determined that 1-15 mM extracellular acetylcholine reduced whole-cell n-type K+ currents in human peripheral blood lymphocytes and accelerated their inactivation. The percentage increase in K+ channel inactivation rate and the degree of drug induced block were independent of membrane potential. In flow cytometric membrane potential measurements with the oxonol dye similar doses of acetylcholine depolarized the lymphocyte population. Both acetylcholine induced K+ channel block and depolarization fully developed within 2 minutes. The depolarizing and K+ channel blocking effects of acetylcholine are in concert. [3H]thymidine incorporation experiments proved that the proliferative response of PHA stimulated peripheral blood lymphocytes was decreased by increasing concentrations of acetylcholine in the 1-50 mM range.

Food restriction increases the protection of erythrocytes against the hemolysis induced by peroxyl radicals

We have investigated the susceptibility to peroxidation of erythrocytes from young, adult and old ad libitum (AL) fed, as well as from adult and old food restricted rats, measuring the rate of hemolysis under controlled peroxidative condition. Food restriction has been applied on an every-other-day (EOD) schedule starting from the age of 3.5 months. The oxidation of red blood cells by molecular oxygen was performed in an aqueous suspension using the azo-compound 2-2'-azo-bis-(2-amidinopropane)hydrochloride (AAPH) as the free radical initiator. Several parameters were calculated from the time-dependent curve of AAPH induced hemolysis. The time required to achieve 50% hemolysis decreased with aging and this decrease was prevented by food restriction. The lag time, which reflects the capacity of the cell to buffer free radicals, was longer in young than in old AL fed animals also this impairment was almost completely prevented in EOD fed animals. The same beneficial effect of food restriction was observed considering the maximal amount of hemolysis attained with the dose of AAPH applied and the time necessary to reach this level. The general picture emerging from the present study is that erythrocyte membranes from EOD fed rats are better protected, than those from AL fed ones, against damages caused by peroxidation. This effect may be due to a difference in the chemical composition of the erythrocyte membranes as it was found in other organs.

Melatonin protects LDL from oxidation but does not prevent the apolipoprotein derivatization

Protective effect of melatonin against Cu++ induced peroxidative modification of low density lipoprotein (LDL) was studied in vitro. Melatonin was used for this purpose because of its known scavenging capacity against hydroxyl and peroxyl radicals. It was demonstrated by the diene formation kinetic analysis that melatonin protected polyunsaturated fatty acids of LDL lipids against peroxidation. Lag time duration was prolonged, peak time was delayed, whereas rate of diene formation was decreased in melatonin treated LDL; however, parameters related to apolipoprotein (apo-B) showed that the protein was derivatized. Fluorescence, relative electrophoretic mobility, lysine residues analysis data, as well as the uptake by macrophages all showed properties similar to those of oxidised LDL. Present data suggest that by-products of melatonin oxidation might react with lysine residues of apo-B, transforming LDL in its atherogenic form.

Glycosylated hemoglobin and fructosamines: does their determination really reflect the glycemic control in diabetic patients?

The present experiment was designed to determine whether scavenging capacity of serum, in addition to glucose level, influences hemoglobin and serum protein glycosylation in non-insulin dependent diabetic patients. For this purpose forty-seven patients homogeneous for age, disease duration, therapy and glyco-metabolic control were selected. Fasting and post-prandial glycemia and insulinemia as well as glycosuria were weekly analysed during the sixty days preceding glycosylated hemoglobin (HbA1c), fructosamines and serum scavenging capacity determination. This last parameter has been evaluated by a method based on the property of beta-phycoerythrin (beta-PE) to loss its fluorescence when damaged by oxygen radicals, that were produced by Cu++ and H2O2. The oxygen radical absorbance capacity (ORACOH) of serum was assayed as the ability of serum to delay the loss of beta-PE fluorescence. As expected, a statistically significant positive correlation was found comparing both fructosamines and HbA1c levels with mean fasting glycemia measured over twenty and sixty days, respectively. The key result of this study is represented by the finding that both HbAlc and fructosamines levels show a statistically significant negative correlation with ORACOH values. This correlation can explain a large percent of the data dispersion occurring when ORACOH is not taken into account. In order to better describe the role of ORACOH, patients were separated into two sub-groups with an ORACOH lower (L-ORACOH) and greater (H-ORACOH) than 100 U/ml. Examining the correlation between mean fasting glycemia and the two glycosylated proteins considered in these two sub-groups, curves with different slopes were obtained, supporting that the rate of glycosylation of both proteins was higher in L-ORACOH patients as compared to those with H-ORACOH. Present data suggest that for a proper interpretation of the HbA1c and fructosamines data in diabetic patients, the scavenging capacity level of serum should be taken into account.

The effect of juglone on the membrane potential and whole-cell K+ currents of human lymphocytes

Using flow cytometric membrane potential measurements with the oxonol dye, we determined that 5.7-57 microM juglone depolarizes human lymphocytes in a dose dependent manner. The depolarizing effect of juglone was verified by patch-clamp. Juglone decreased whole-cell n-type K+ currents in human peripheral blood lymphocytes and accelerated inactivation; however, it did not influence the kinetics of activation of the K+ conductance. The percentage increase in K+ channel inactivation rate and the degree of drug induced block was independent of membrane potential, K+ channel block by juglone fully developed within 4 minutes and was not removable by washing with drug free extracellular solution. Blocking of n-type K+ channels by juglone is in concert with its depolarizing effect on human lymphocytes.

The impairment of mitochondrial membrane potential and mass in proliferating lymphocytes from vitamin E deficient animals is recovered by glutathione

The time-dependent changes of mitochondrial membrane potential and mass have been investigated on splenocytes from control and vit. E deficient rats, stimulated to proliferate with Concanavalin A, in the presence and absence of reduced glutathione (GSH, 5 mM). Rhodamine-123 (Rh-123) and nonyl acridine orange (NAO) were used as specific probes to monitor the membrane potential and mass of mitochondria, respectively, by means of flow cytometry. Rh-123 uptake was high in an increasing number of cells from normally fed animals during the three-day culture period. On the contrary, splenocytes from vitamin E deficient rats showed a biphasic pattern. The number of cells showing a high uptake of Rh-123 increased after 24 hrs. from mitogenic stimulation, then it decreased at the other two time points considered. In parallel, a continuous increase of the number of cells with depolarized organelles (up to 60% by 72 hrs.) has been observed in vit. E deficiency. This impairment was fully prevented by GSH supplementation to the culture medium. In the presence of the thiol, about 80-85% of cells showed activated mitochondria, whereas the number of splenocytes with depolarized organelles did not exceed 17%, irrespective of the diet applied to the animals. The same pattern was observed considering the changes of mitochondrial mass, measured using NAO as a probe. Present results support that GSH may substitute vitamin E in protecting mitochondria from peroxidative damage.

Effect of reduced glutathione on mitochondrial parameters of proliferating splenocytes from young and old rats

The time-dependent changes of mitochondrial membrane potential and mass have been investigated on splenocytes from young, adult and old rats stimulated with Con A in the presence and absence of reduced glutathione (GSH). In addition, the basal level as well as the level of GSH during a 3-day culture period has been determined. No age-dependent changes of cellular GSH content were observed in freshly prepared splenocytes; however, in proliferating cells from old animals the expected increase in GSH levels was delayed. As regards the mitochondrial parameters, their membrane potential and mass were measured by means of the fluorescent probes rhodamine-123 (Rh-123) and nonyl acridine orange (NAO), respectively, and flow cytometry. During aging and with time of culture, an increased number of cells showed depolarization and loss of mitochondrial mass. This age-dependent impairment was completely prevented by addition of GSH to the culture medium, which resulted in a sharp increase in intracellular GSH. The present findings support the view that an impairment of the antioxidant defense system may be responsible for the damage observed in the mitochondria of proliferating splenocytes from old animals.

Effects of bretylium tosylate on voltage-gated potassium channels in human T lymphocytes

Using the patch-clamp technique, we determined that bretylium tosylate, a quaternary ammonium compound possessing immunomodulating activity, decreased the whole-cell K+ current in human T lymphocytes, in a dose-dependent manner, in the 0.05-5 mM extracellular concentration range. Bretylium tosylate prolonged the recovery from inactivation and accelerated the inactivation and deactivation of the K+ current but did not influence the kinetics of activation or the voltage dependence of activation and steady state inactivation of the K+ conductance. The percentage of drug-induced block was independent of membrane potential. K+ channel block by bretylium tosylate was partially and slowly removable by washing with drug-free extracellular solution. Bovine serum albumin (10 mg/ml) in the bath lifted the drug-induced block almost instantaneously, although not completely. In control experiments bovine serum albumin increased the inactivation time constant of the K+ channels but left the peak K+ current amplitude unaffected. On the basis of the experimental evidence, a gating-dependent allosteric interaction is suggested for the mechanism of drug action. The effective dose range, time of exposure, and reversibility of bretylium tosylate-induced K+ channel block correlated well with the same parameters of the drug-induced inhibition of T lymphocyte activation. The reported effects of bretylium tosylate on T cell mitogenesis can be regarded partly as a consequence of its blocking effects on voltage-gated K+ channels.

Food restriction in female Wistar rats. VII. Mitochondrial parameters in resting and proliferating splenic lymphocytes

The effect of food restriction on the mitochondria of resting and proliferating rat splenocytes was examined, measuring the membrane potential and mass of these organelles, by means of the specific fluorescent probes Rhodamine-123 and Nonyl Acridine Orange, respectively. Food restriction was applied on an every-other-day schedule (EOD) starting at the age of 3.5 months. The ad libitum fed (AL) animals were killed when they were 4, 11 and 24 months old, whereas the EOD rats were killed at 11 and 26 months. Resting lymphocytes from AL rats showed an age-dependent increase of both membrane potential and mass of their mitochondria. However, the mitochondrial mass increased to a larger extent when compared with the membrane potential resulting in a decrease of the respiratory quotient (RQ), i.e. of the respiratory activity per unit of mitochondrial mass. In EOD animals, the mitochondrial membrane potential was lower and the mitochondrial mass was higher in the corresponding age-matched controls, resulting in a further decrease of RQ. Following mitogenic stimulation, most of the cells from young and adult AL rat showed an increase of membrane potential and mass of their mitochondria. In contrast about 50% of cells from old AL rats had depolarized organelles after 72 h from the stimulation. Food restriction was able to prevent these alterations allowing the majority of cells, including those from old animals, to maintain the hyperpolarization of their mitochondria during the 3-day culture. In light of the well known sensitivity of mitochondrial membrane potential to peroxidative stress, present data suggest that the increase of respiration occurring during mitogenesis may increase free radical production, which is better tolerated by cells from EOD animals than by those from AL animals.

Melatonin: a peroxyl radical scavenger more effective than vitamin E

We have compared the peroxyl radical scavenger ability to melatonin with that of vitamin E, vitamin C and reduced glutathione (GSH). In the assay system, beta-phycoerythrin (beta-PE) was used as fluorescent indicator protein, 2-2'-azo-bis(2-amidinopropane)dihydrochloride as a peroxyl radical generator and the water soluble vitamin E analogue. Trolox, as reference standard. Results are expressed as oxygen radical absorbing capacity (ORAC(perox)) units, where 1 ORAC unit equals the net protection produced by 1 microM Trolox. A linear correlation of ORAC values with concentration (0.5-4 microM) of all the substances tested has been observed. However, on molar basis, the relative ORAC(perox) of Trolox, vitamin C, GSH and melatonin was 1:1.12:0:68:2.04, respectively. Thus, melatonin, which is a lipid-soluble compound, was twice more active than vitamin E, believed to be the most effective lipophilic antioxidant.

Vitamin E deficiency impairs the modifications of mitochondrial membrane potential and mass in rat splenocytes stimulated to proliferate

This study was designed to evaluate the time-dependent changes of mitochondrial membrane potential and mass during Con-A-induced proliferation of splenic lymphocytes from rat fed a normal or a vitamin E deficient diet. Rhodamine 123 and Nonyl Acridine Orange were used as specific probes to monitor the membrane potential and mass of mitochondria, respectively, by means of flow cytometry. The results demonstrate that the increase of Rh-123 and NAO uptake observed in cells from normally fed rats was prevented by vitamin E deficiency, at any time considered. After 72 h from Con A stimulation, 62% of cells from controls, as against 16% of cells from vitamin E deficient rats, showed hyperpolarized mitochondria. At the same time, in this last group, 60% of cells had depolarized organelles. The same pattern was observed considering the changes of mitochondrial mass, measured using NAO as a probe. These data support that mitogenic stimulation induced an increase of the respiratory activity of mitochondria with subsequent production of superoxide radicals. This resulted in depolarization and loss of mass of the organelles if the intracellular level of vitamin E is not adequate.

Reduced glutathione recovers the impairment of the proliferative response of splenic lymphocytes from vitamin E-deficient rats

The effect of reduced glutathione (GSH) on the Con A induce proliferative response of splenic lymphocytes from rats fed a normal or vitamin E-deficient diet has been investigated. The animals were killed when they were 12 months old and after 11 months of dietary treatment. As was expected, a decreased response, measured in terms of blast transformation or [(3)H]thymidine incorporation, was observed in vitamin E-deficient animals when compared with the control group. This pattern can be accounted for by the large number of dead cells found in deficient animals. GSH addition into the culture medium resulted in a strong increase of the response in both groups and it eliminated the difference caused by the different dietary regimens. Taking into account that, during proliferation, an increase of respiration occurs which increases the risk of free radical production, present data suggest that GSH may substitute vitamin E in protecting the cells.

Age-dependent modifications of mitochondrial trans-membrane potential and mass in rat splenic lymphocytes during proliferation

The specific fluorescent probes, Rhodamine 123 (Rh-123) and Nonyl-Acridine Orange (NAO) were, respectively, used to monitor the changes in membrane potential and mass of lymphocyte mitochondria during aging and proliferation. An age-dependent increase of the uptake of both fluorochromes was observed in resting cells; however, NAO fluorescence increased to a greater extent when compared with the Rh-123 probe. This resulted in a lower respiratory activity per unit of mitochondrial mass in old cells than in the young ones. Following mitogenic stimulation, most of the lymphocytes from young rats showed an increase in their membrane potential and mass. On the contrary about 50% of cells from old rats had depolarized mitochondria after 72 h from the stimulation. Present data support that mitochondria of lymphocytes from old rats are extremely sensitive to the stressing conditions resulting from mitogenic stimulation.

Bretylium differentiates between distinct signal transducing pathways in human lymphocytes

The selection of signal transducing pathways of T cells depends on the type of triggers. Antigens, antibodies or lectins induce the T cell receptor-CD3 operated pathway, and IL-2 transmits its activation signal via the IL-2 receptor. It has been demonstrated that bretylium, a quaternary ammonium ion, can significantly inhibit the first pathway at the same dose range that stimulates cell activation through the IL-2 receptor system. In the light of the different complexity of the two pathways at the plasma membrane level, and the non-toxic and reversible behavior of the drug, it is suggested that the bretylium induced sustained membrane hyperpolarization is responsible for the observation. This finding may open new possibilities in studying the mechanism of different signal transducing pathways.

The response of human lymphocytes to phytohemagglutinin is impaired at different levels during aging

Several parameters generally believed to be necessary for the activation and progression of proliferation of human lymphocytes have been investigated and compared with special reference to aging. The responding capacity of plasma membrane potential to depolarizing and also repolarizing conditions induced by exposure to mitogens like PHA was lower in lymphocytes from old donors as compared to those of young ones. This indicates a significant age-dependent difference in the readiness to respond to channel-activating perturbations. As an early signal of activation, after one hour PHA stimulation the merocyanine 540 uptake by the lipid regions was chosen, based on the property of this fluorescent probe to bind to loosely packed lipids of the plasma membrane. The proteins encoded by the c-myc and c-myb genes were chosen as markers of the G0/G1 and G1/S phased transition, respectively. The mean number of cells that increased the uptake of MC 540 following mitogenic stimulation did not differ in young vs. old individuals. However, 4 samples out of 10 from the old population showed lower MC 540 fluorescence than the lowest signal from the young population. The number of responding cells was decreased during aging when the presence of the c-myc protein was taken as its measure; and this decrease was further accentuated, determining the expression of the c-myb protein. This frequently encountered age-dependent pattern, however, was not followed by the lymphocytes of all old donors. One example is reported in which the MC 540 uptake, the c-myc and c-myb expression in the cells from one old subject fell in the range of the young subjects. However, even in this case, the response of the lymphocytes as measured by 3H-thymidine incorporation was only 64% of that of young subjects. For this sample, we found an impairment of the response at the mitochondrial level. In addition to these parameters, the amount of 3H-thymidine incorporated by the cells expressing the c-myb protein was calculated. The values in old individuals were lower than those in the young, suggesting that not all the cells expressing the c-myb protein were able to synthesize DNA in lymphocyte populations from the elderly. Our data support the view that the age-dependent decline of lymphocyte responsiveness to mitogens can be accounted for by impairments at different levels.(ABSTRACT TRUNCATED AT 400 WORDS)

Glutathione influences the proliferation as well as the extent of mitochondrial activation in rat splenocytes

The time-dependent changes of mitochondrial membrane potential and mass have been investigated on rat splenic lymphocytes stimulated with Con A in the presence and absence of reduced glutathione (GSH). Rhodamine-123 (Rh-123) and nonyl acridine orange (NAO) were used as specific dyes to monitor the membrane potential and mass of mitochondria, respectively. The percentage of cells showing blast transformation and the level of Rh-123 or NAO uptake were analyzed by flow cytometry. Present results demonstrate that a large number of cells showed activated mitochondria already at 24 hr after Con A stimulation and the activation of these organelles was not related to blast transformation. The addition of GSH into the culture medium increased the number of cells responding to mitogenic stimulation. In parallel it augmented the percentage of lymphocytes with activated mitochondria and also prevented their depolarization.

Bretylium-induced voltage-gated sodium current in human lymphocytes

Using the whole-cell variation of the patch-clamp technique it has been determined that 0.25-3 mM bretylium tosylate (BT) exerts a repolarizing effect on partially depolarized human lymphocytes. The repolarizing effect was ouabain (40 microM)-sensitive, and was inhibited by the removal of external Na+ or by the Na(+)-channel-blocker amiloride (10-44 microM), but K(+)-channel-blockers 4-aminopyridine (0.1-5 mM) and quinine (100 microM) had no effect. The drug induced a sodium dependent, amiloride-sensitive transient inward current reaching its maximum value approx. 20-30 s after the administration of BT and lasting for 6-10 min. This current was activated by depolarization within 25 ms at around -42 mV, its inactivation took about 2 s and its reversal potential was +24 +/- 5 mV. An increase in the intracellular sodium concentration (1.8-3.2 mM) has been observed upon the addition of BT by monitoring the SBFI fluorescence of the dye-loaded cells. It has been shown that whole-cell K+ currents are significantly decreased by BT. The existence of voltage and ligand (BT)-gated sodium channels has been postulated in human lymphocytes. These channels are thought to participate in the initiation of membrane repolarization in human lymphocytes, and thereby influence mitogenic or antigen-induced cell-activation processes.

Dynamic physical interactions of plasma membrane molecules generate cell surface patterns and regulate cell activation processes

Molecular interaction and transmembrane signal transducing events generate a very dynamic and ever changing "pattern" in the plasma membranes. Lymphocytes, the key functional elements of the immune system, are eminently suited to be the primary targets to investigate these proximity, mobility, or other physical-chemical changes in their plasma membranes. Recently, a number of experiments suggested that processed peptides from antigens can bind specific components of MHC molecules (Elliott et al., 1991). This is certainly a way to alter their structure. Cell surface patterns of topological nature, assembly and disassembly of oligomeric receptor structure like the IL-2 receptor have been investigated by sophisticated biophysical techniques. The dynamic changes in the two-dimensional cell surface pattern and intramolecular conformational changes within this "larger" macro-pattern may have a strong regulatory role in signal transducing and intercellular recognition processes. Recent data on these problems are presented together with brief and critical discussions.

Lipid peroxidation causes an increase of lipid order and a decrease of 5'-nucleotidase activity in the liver plasma membrane

The effect of peroxidation on 5'-nucleotidase activity as well as on membrane microviscosity has been investigated in liver plasma membranes from Wistar rats. The peroxidation was performed with 100 microM H2O2 and 200 microM FeSO4 and/or with 5 mM t-butylhydroperoxide. Treatment of the membranes with these oxidizing agents resulted in an elevation of the transition temperatures of the polarization of the lipid fluorescent probes 1,6 diphenyl-1,3,5 hexatriene (DPH), 3-p-(6-phenyl) 1,3,5 hexatriene phenylpropionic acid (PA-DPH) as well as of the fluorescent thiol reagent N-(1-pyrene) maleimide (1-PM). The peroxidation resulted in a decrease of the activity of 5'nucleotidase. Our data support that the increase of membrane microviscosity of the lipid domain regulates the activity of 5'-nucleotidase.

Phytohemagglutinin induced changes of membrane lipid packing, c-myc and c-myb encoded protein expression in human lymphocytes during aging

Three parameters which signal different stages of cell activation were analyzed in lymphocytes from young and old subjects. Merocyanine 540 (MC-540) incorporation into the membrane lipid phase was used as a very early marker of activation and was measured after 1 h of phytohemagglutinin (PHA) stimulation. The proteins coded by c-myc and c-myb protooncogenes were determined by appropriate antibodies and were taken as markers of the G0/G1 and G1/S phase transition, respectively. The number of cells which increased the uptake of MC-540 following PHA stimulation did not differ when comparing young and old individuals. Both the number of the responding cells and the size of the response were decreased during aging when the presence of the c-myc protein was taken into account. A consistent decrease of the percentage of lymphocytes able to express the c-myb protein was observed in the cells from old donors as compared to those from the young ones, but the amount of detectable protein per cell remained unchanged. Our data suggest that the deficiency of responsiveness which accompanies aging is due to impairments at different points of the cell cycle. The very low number of cells expressing the c-myb protein is likely the result of step by step elimination of those cells not able to fulfill the requirements to progress along the cell cycle.

Ion channel activity and transmembrane signaling in lymphocytes

Transmembrane signalling refers to the process of transfer of information from the extracellular world into the intracellular space. The information is transduced through several possible pathways. The significance of cell surface dynamics, ion channel activity and drug effects are discussed in the signal transmission, with special reference to Na+ channels and the Ca2+ sensitive potassium channels.