Different sensitivities to ethanol of three early transient voltage clamp currents of aplysia neurons

Ethanol suppresses neuronal Ca2+ currents by effects on intracellular signal transduction

The mechanism of action of ethanol on voltage-activated Ca2+ currents in neurons of the mollusk, Helix pomatia, was studied focusing on intracellular signaling. Ethanol suppressed inward Ca2+ currents in a time- and voltage-dependent manner. Buffering of intracellular Ca2+ with bis(o-aminophenoxy)ethane-N,N,N',N-tetraacetic acid (BAPTA) abolished the ethanol effects on Ca2+ currents. Intracellular GTP-gamma-S injection decreased Ca2+ currents whereas GDP-beta-S injection was ineffective. Ethanol had no further blocking effect on Ca2+ currents in GTP-gamma-S injected cells. In the presence of dopamine, which is known to suppress Ca2+ currents by G0-protein activation, ethanol application was ineffective. The protein kinase C (PKC) blockers, staurosporine and chelerythrine, prevented the ethanol effects on Ca2+ currents. The PKC activators, 1,2-oleoylacetylglycerol (OAG) and beta-phorbol-12,13-dibutyrate (PdBu), both, after maximum stimulation, also occluded the effect of ethanol on Ca2+ currents, whereas in the presence of 4-alpha-phorbol-12,13-didecanoate (4-alpha-PDD), an ineffective phorbol ester, ethanol suppressed Ca2+ currents. Ethanol increased the threshold of Ca2+-dependent action potentials and decreased their duration. Our results indicate that the suppression of voltage-activated Ca2+ currents by ethanol and its effects on action potentials involve activation of a G-protein/protein kinase transduction pathway.

Role of the GTP-binding protein G(o) in the suppressant effect of ethanol on voltage-activated calcium channels of murine sensory neurons

Whole-cell and single-channel recording techniques were used to investigate the acute, in vitro effects of ethanol on the function of voltage-activated Ca2+ channels in cultured neurons derived from dorsal root ganglia (DRG) of embryonic mice. Although 5.4 mM ethanol produced a sustained increase of the amplitude of the whole-cell Ca2+ current (ICa), 43.2 mM ethanol had a time-dependent biphasic effect. That is, within 0.5 min of exposure to 43.2 mM ethanol, the maximal amplitude of ICa initially increased before declining to a new steady-state value. As anticipated, the facilitatory and inhibitory effects of ethanol on ICa were associated with an increase and decrease, respectively, in the probability of single-channel open events. Pretreatment of DRG with 200 ng/ml of pertussis toxin abolished the inhibitory, but not the facilitatory, effect of 43.2 mM ethanol on ICa. Pretreatment with pertussis toxin also prevented the reduction of the probability of single-channel opening caused by 43.2 mM ethanol. Similarly, dialysis of neurons with polyclonal antibodies against the alpha-subunit of G(o) but not Gs, abolished the inhibitory effect of 43.2 mM ethanol on ICa. These data demonstrate concentration- and time-dependent biphasic effects of ethanol on the activity of Ca2+ channels. The inhibitory effect of ethanol requires activation of the alpha-subunit of G(o), which then decreases the probability of Ca2+ channel opening.

Ethanol decreases the velocity of spike propagation along a fast motor axon

Intracellular recordings were made from the fast bender excitor motor axon in autotomized crab limbs bathed in normal saline, and in salines made with up to 240 mM of ethanol. The presence of ethanol reduced the amplitude, the rise time and the decay time of the evoked action potential, and decreased the velocity at which the spike was conducted down the axon. There was a linear relationship between each of these four parameters and the concentration of ethanol in the saline. The close relationship between spike rise time and conduction velocity suggests that ethanol slows the rate of membrane depolarization by the spike and thus decreases the velocity at which action potentials are propagated along the axon.

Acute alcohol alters the excitability of cerebellar Purkinje neurons and hippocampal neurons in culture

Acute exposure to ethanol at 22 and 44 mM concentrations altered several features of the current-evoked voltage responses of cerebellar Purkinje neurons and hippocampal neurons studied in culture model systems. Whole cell current clamp techniques were used. At 22 mM, ethanol depressed current-evoked spiking in the hippocampal neurons but enhanced the current-evoked spiking in the Purkinje neurons. In both neuronal types, 44 mM ethanol depressed spiking, the amplitude of the afterhyperpolarization generated at the termination of a current pulse and the amplitude of the off-response generated at the termination of a hyperpolarizing pulse. Ethanol had little or no effect on resting membrane potential or the passive membrane properties measured near resting level in either neuronal type. Some changes in the current-voltage curves were observed at more depolarized or hyperpolarized potentials in both neuronal types. In the Purkinje neurons, where spontaneous activity was a prominent feature of some recordings, exposure to ethanol reduced the frequency of the spontaneous events. These results indicate that acute exposure to ethanol at intoxicating doses alters the membrane excitability of these two CNS neuronal types. The ethanol induced changes in neuronal excitability presumably contribute to the changes in firing properties observed in extracellular recordings from these neuronal types in vivo and the behavioral effects observed during alcohol intoxication in animal models.

Differential effects of alcohols on the spike threshold of an identified motor axon in a crab (Pachygrapsus crassipes)

Observations were made on the fast bender excitor (FBE) axon in autotomized crab limbs bathed in salines made up with different alcohols. It has been shown previously that the presence of ethanol at a certain level causes a single action potential to generate additional spikes in the peripheral axon branches. The present study examines the level of different alcohols required to induce peripheral spike generation. For primary alcohols, increasing the molecular weight decreased the level of alcohol required to produce peripheral spike generation. The threshold level of 2-butanol was greater than 1-butanol, but less than tertiary-butanol. These results are explained in terms of the partition coefficient, so that an alcohol with a higher partition coefficient enters the lipid bilayer more readily, thus a lower threshold level of that alcohol is required in the saline to generate additional spikes.

Chronic exposure to alcohol during development alters the membrane properties of cerebellar Purkinje neurons in culture

The active and passive membrane properties of developing Purkinje neurons in control cultures and cultures chronically treated with 20 or 40 mM ethanol for 1 or 2 weeks were examined using whole-cell current-clamp techniques. The membrane properties were characterized by the features of the voltage responses evoked by intracellular current injection of a series of depolarizing and hyperpolarizing current pulses. Analysis of these responses and background spontaneous activity showed several differences between the control and ethanol-treated Purkinje neurons: (1) membrane input resistance was significantly larger in the ethanol-treated neurons; (2) the percentage of neurons exhibiting immature firing patterns was significantly higher in the ethanol-treated neurons; (3) the afterhyperpolarization following a current-evoked train of action potentials was significantly larger in the ethanol-treated neurons; (4) spontaneous activity (synaptic potentials and synaptically evoked spike events) was significantly reduced in neurons treated with 40 mM ethanol for 1 week; spontaneous activity in neurons treated with 20 mM ethanol for 1 or 2 weeks was similar to that observed in the control group. These differences indicate that ethanol exposure during development directly alters the physiological properties of this CNS neuronal type. These neuronal actions of ethanol may contribute to the behavioral deficits observed in animals models of fetal alcohol syndrome. Similar target sites of ethanol action are likely to be present in the human CNS neurons and may be involved in human fetal alcohol syndrome.

Acute ethanol alters the firing pattern and glutamate response of cerebellar Purkinje neurons in culture

Modified explant cultures derived from the cortical region of fetal rat cerebellum, and extracellular recording techniques were used to examine the sensitivity and response of cerebellar neurons, isolated from extracerebellar afferent input, to acute ethanol (EtOH) exposure. Recordings were made from Purkinje neurons (PNs) and granule cells maintained in culture for several weeks, with the emphasis on the PN. Both the PNs and granule cells exhibited spontaneous activity in culture, but, unlike the PNs, not all of the granule cells were spontaneously active. The majority of PNs studied exhibited a high frequency, regular simple spike firing pattern, previously shown to be endogenously generated by voltage-sensitive mechanisms intrinsic to the PN. The granule cells exhibited slow, irregular patterns of activity. EtOH at doses as low as 22 mM (100 mg%), a concentration that reflects blood levels during EtOH intoxication, altered the spontaneous activity of both neuronal types, demonstrating that EtOH has direct actions on cerebellar neurons. In the PNs, acute EtOH (20-80 mM) produced an increase in the regularity of the spontaneous activity and either a transient increase or no change in firing rate. Acute EtOH also significantly altered the response of PNs to the excitatory transmitter glutamate. In the granule cells, acute EtOH altered firing pattern with small and variable effects on firing rate. These data demonstrate that there are multiple sites of EtOH action in the cerebellum and that changes in PN activity with acute EtOH exposure may occur via direct actions on the PN and indirect actions via synaptically connected cerebellar neurons. The demonstration of EtOH-sensitive sites intrinsic to the cerebellum suggests that EtOH actions at these sites contribute to alterations in PN activity that occur in vivo after acute EtOH exposure.

Ethanol-induced reduction of neuronal calcium currents in Aplysia: an examination of possible mechanisms

1. Experiments were performed to determine the mechanisms by which ethanol (EtOH) decreases the amplitude of voltage-dependent inward currents through calcium channels in Aplysia neurons. Voltage-clamp protocols used conditioning prepulses of varying amplitude, duration, and frequency, to examine the relationship between prior activity of the channel and EtOH action. Calcium and barium were used as charge carriers, allowing dissociation of effects due to inactivation of calcium channels from other perturbations resulting in the impediment of current flow through the open channel. 2. When Ba2+ was the charge carrier and channel activation was unconfounded by inactivation processes, the reduction of ICa produced by EtOH was independent of the voltage, frequency, or duration of conditioning prepulses. 3. When Ca2+ was the charge carrier, ICa was reduced as a function of conditioning prepulses, in three protocols used. EtOH enhanced this reduction, most probably because of its effects on the inactivation of ICa. Consistent with this interpretation, the time constant of decay of ICa was decreased, and recovery from inactivation was retarded by EtOH. 4. EtOH did not reduce ICa by a change in membrane surface potential, at least at low EtOH concentrations. 5. An analysis of the time course of development of ICa reduction by EtOH showed that it developed slowly, over a matter of minutes. 6. Our data indicate that EtOH does not reduce ICa by direct occlusion of the calcium channel. EtOH affects the inactivation of the calcium current, and this may occur by an action on the channel protein.

The electrophysiology of potassium channels

Ethanol actions have mainly been described in terms of physicochemical membrane actions. More recently, investigators using intracellular electrophysiological recording techniques have been able to describe ethanol effects on ionic channel function. This chapter reviews the literature on ethanol-potassium channel interactions and discusses the hypothesis that the inhibitory effects of ethanol on central neurons are mediated by increased potassium conductance.

Effects of ethanol on the functional properties of sodium channels in brain synaptosomes

Voltage-sensitive sodium channels in excitable cell membranes are responsible for the rapid increase in permeability to sodium ions that occurs during depolarization. Neurotoxins that bind with high affinity and specificity to voltage-sensitive sodium channels have been widely used to identify and characterize the structure and function of sodium channels in nerve and skeletal muscle. This chapter describes the actions of ethanol on the functional properties of voltage-sensitive sodium channels in mammalian brain nerve endings. The effects of acute and chronic ethanol administration are also reviewed. Alterations in the function of neuronal membrane sodium channels may be involved in the depressant effect of ethanol.

The effects of ethanol on the electrophysiology of calcium channels

Acute ethanol intoxication affects many systems in the body, especially the central nervous system. Because early experiments using axonal preparations required very high concentrations of ethanol to produce ionic current alterations, researchers turned their attention away from specific effects on electrogenesis and looked for effects at the synapse. The role of Ca2+ in the release of neurotransmitters was well known and was considered a possible site of action for ethanol. Indeed, several studies demonstrated that ethanol alters Ca2+ binding or transport in synaptosomes and neural tissue. The purpose of this chapter is to present electrophysiological evidence for the acute effects of ethanol on calcium channels. It is necessary first to define the relevant ethanol concentrations and to describe the characteristics of tissue preparations that may best help to determine the effects of ethanol. A discussion of these two points along with a brief synopsis of the role of Ca2+ in excitable tissues is presented. This is followed by a discussion of the effects of ethanol on Ca2+ and Ca2+-activated conductances in both nonmammalian and mammalian cells, and a model is presented in an attempt to unify the experimental evidence of the acute effects of ethanol.

Ethanol effects on voltage-dependent membrane conductances: comparative sensitivity of channel populations in Aplysia neurons

The study of ethanol (EtOH) action is interesting because of its clinical relevance and for the insights it provides into structure-function relationships of excitable membranes. This paper describes the concentration dependencies of various parameters of four currents in Aplysia cells. ICa is the most sensitive of the currents studied. There was a significant reduction of ICa at concentrations of 50 mM EtOH. At low concentrations, the reduction of amplitude was the primary effect of ethanol, with the kinetics and voltage dependency of activation not affected. INa and IA were also affected, but at EtOH levels higher than those which altered ICa. The primary effect of EtOH on INa was a reduction in its amplitude, although the time to peak current flow was increased by EtOH. The effects of EtOH on IA were cell specific and, for the purposes of this paper, we examined the giant metacerebral cell (MCC). In MCC, the primary effect of EtOH on IA was an increase in the time course of inactivation. The time to peak IA was also increased by high concentrations of EtOH, but its amplitude was unaffected even at high concentrations. The delayed rectifier current, IK, was the most EtOH resistant of the currents examined. High EtOH concentrations augmented the amplitude of IK, although even at 600 mM concentrations, the percentage change was only 30%. Our results indicate that the calcium channel is very susceptible to the influence of ethanol and is a serious candidate to be the primary target of EtOH action in the nervous system. The differential sensitivity of voltage-dependent currents and individual components of a given current suggests further experiments to probe the relationship between membrane structure and channel function in excitable membranes.

Role of alcohol in clinical nephrology

Different nephrological derangements are observed in severe alcoholics. Until now the direct toxicity of ethanol is only shown in the fetal alcohol syndrome with various malformations of the genitourinary tract. In the adult the kidney is often involved in the development, maintenance and counterregulation of complex electrolyte disturbances like phosphate and potassium hypoglycemia etc. The alcohol associated retention of urate, induced by hyperlactatemia and/or increased beta-hydroxybutyrate concentration is only rarely complicated by urate nephropathy. Alcohol intoxication (acute and chronic) predisposes to rhabdomyolysis with the risk of acute renal failure. There are some hints that chronic alcoholism with myopathy increases the vulnerability of the kidney for further toxic agents. In rats glycerol induced renal failure is enhanced by alcohol pretreatment. Finally, regular alcohol consumption raises the blood pressure, which per se is a risk factor for renal damage.

Effect of ethanol on subthreshold currents of Aplysia pacemaker neurons

The subthreshold currents in bursting pacemaker neurons of the Aplysia abdominal ganglion were individually studied with the voltage clamp technique for sensitivity to 4% ethanol. The most prevalent effect of ethanol on unclamped bursting neurons was a hyperpolarization. This was shown to be due to a decrease of a voltage independent inward leakage current. Direct measurement of the Na-dependent slow inward current showed that this current was eliminated by 4% ethanol. Direct measurement of the Ca-dependent slow inward current showed that this current was substantially reduced by 4% ethanol. Injection of EGTA into cell bodies did not eliminate the ethanol-induced block of the slow inward calcium current. Thus, ethanol cannot be reducing the Ca-dependent slow inward current solely by an increase of internal calcium concentration. The effect of ethanol on voltage dependent outward current was measured by blockage of all inward current. The peak outward current was increased by ethanol. The rate of inactivation of this outward current was also increased. Calcium activated potassium current (IK(Ca)) is particularly complicated in its response to ethanol because it is dependent on both Ca and voltage for its activation. The level of IK(Ca) elicited in response to constant Ca injection was increased by ethanol treatment. The level of this current as activated by voltage clamp pulses was either increased or decreased depending on the neuron type. Ca2+ activated potassium conductance increased e-fold for a 26 mV depolarization in membrane holding potential. Ethanol decreased this voltage dependence to e-fold for a 55 mV change in potential. This result was interpreted to mean that ethanol shifted an effective Ca2+ binding site of these channels from about halfway through the membrane field to one quarter of the way across. The same theoretical approach allowed the further conclusion that ethanol caused an increased internal free calcium concentration probably by decreasing calcium binding by intracellular buffers.

Postsynaptic actions of ethanol and methanol in crayfish neuromuscular junctions

Actions of ethanol and methanol on excitatory postsynaptic channels activated by quisqualate were investigated in opener muscles from the first walking leg and the claw of crayfish. Both ethanol and methanol reduced the elementary currents [i] that flow through channels operated by quisqualate in a concentration-dependent manner but did not affect the apparent mean open time, tau noise, of the channels estimated from power spectra. 0.26 mol/l ethanol, or 1 mol/l methanol, respectively, reduced [i] e-fold. Ethanol also markedly decreased the size and the decay time constant tau (sEPSCs) of spontaneous excitatory postsynaptic currents (sEPSCs). At ten fibres, on the average, 0.26 mol/l ethanol decreased tau (sEPSCs) by a factor 1.56 +/- 0.24 (SD). tau (sIPSCs) and tau noise of inhibitory postsynaptic currents apparently were not affected by ethanol. Moreover the size of elementary inhibitory postsynaptic currents did not decrease in the presence of this alcohol. Thus, in crayfish opener muscles ethanol seems to selectively depress excitatory postsynaptic currents.

Voltage clamp analysis of ethanol effects on pacemaker currents of Aplysia neurons

The effect of 4% ethanol on pacemaker currents of Aplysia neurons was studied under voltage clamp. In normal seawater the n-shape in the I-V disappeared and outward current increased. Ion substitution and drug blocking experiments determined that leakage current and the slow inward calcium current were decreased and that the outward currents, IA and IK, were increased. This knowledge can be used to explain ethanol effects on spontaneous firing patterns.

Electrophysiologic effects of acute ethanol exposure. I. Alterations in the action potentials of dorsal root ganglia neurons in dissociated culture

Dissociated dorsal root ganglion neurons from embryonic rats were exposed to 0.05, 0.15 and 0.30 g% ethanol for 1 h. Action potentials were recorded and statistically compared for differences from the control values. Exposure to ethanol produced no significant alterations in the resting membrane potential, spike amplitude, or maximum rate of rise in any of the experimental conditions. Significant differences were noted in parameters associated with the repolarization phase including decreases in the maximum rate of fall and one-half time to convergence and increases in the full width of half maximum and full width of base parameters. These alterations were reversed within 30 min after ethanol removal. In order to determine the specific ionic conductances affected by ethanol, action potentials were recorded from neurons exposed to specific Na+, Ca2+, and K+ current blockers. Analysis of the data indicates that K+ conductance is decreased as a result of a decreased Ca2+ current. Further, maximum Na+ conductance is not significantly affected by physiologic concentrations of ethanol.

Effects of alcohols upon pacemaker activity in neurons of Aplysia californica

1. Alcohols have been used as pharmacological tools to probe the nature of action-potential gates and channels. In this study, we examine the effects of alcohols upon activity patterns in Aplysia neurons. 2. Ethanol at concentrations of 0.4-0.6 M induces bursting pacemaker activity (BPA) in previously silent cells. The same effect is produced with 40-60 mM concentrations of butanol, suggesting that this induction is not due to osmotic effects. 3. Voltage-clamp measurements indicate that the induction of BPA is accompanied by the appearance of a negative-slope resistance (NSR) region in the steady-state current-voltage relationship of the cell. The induction of BPA and a NSR region in silent cells is antagonized by lowered temperatures. 4. Ethanol concentrations which produce BPA and a NSR region in silent cells abolish both of these normally present characteristics in endogenous bursters. This suggests that whatever membrane components are moved into optimal configuration for the expression of BPA in silent cells are shifted out of optimal configuration in endogenous bursters, by similar ethanol concentrations.

Ethanol alters synaptic activity in cultured spinal cord neurons

The acute effects of ethyl alcohol on mammalian central neurons were investigated using electrophysiological techniques and an in vitro model system, cultured fetal mouse spinal cord neurons. Intracellular recordings were made from the cultured neurons to evaluate the effect of alcohol (10-100 mM) on membrane potential, membrane permeability, amplitude of the action potential, sensitivity of the neurons to putative neurotransmitters and the process of synaptic transmission. Alcohol was applied by superfusion; putative amino acid neurotransmitters were applied by micropressure ejection. The most dramatic effect of alcohol on the spinal cord neurons was a reduction in the spontaneous activity (excitatory and inhibitory synaptic potentials and action potentials) and the glutamate evoked synaptic activity. Alcohol doses as low as 20-30 mM, concentrations which reflect blood levels during intoxication, were effective. Membrane potential, membrane permeability, and amplitude of the action potential were relatively resistant to these low doses of alcohol; at the higher alcohol doses, no effect or only modest alterations of these characteristics were observed. The responses of the neurons to the putative excitatory neuro-transmitter glutamate, and inhibitory transmitters GABA and glycine were also relatively resistant to alcohol exposure. These data indicate that acute exposure to alcohol has a predominantly inhibitory action on the activity of the cultured mammalian CNS neurons, and that this inhibition is most likely due to an alteration in the process of synaptic transmission.

Effect of ethanol on stretch response of muscle receptors in cats

The response of muscle spindles and tendon organs to steady and sinusoidal muscle stretch was investigated at different blood alcohol concentrations (BAC). After initial anesthesia (pentobarbital), cats were spinalized, the lumbar ventral roots cut and the gastrocnemius muscles of one hindleg prepared for controlled stretching. The animals were paralyzed and artificial respiration was applied. Action potentials from isolated Ia/Ib/II afferent fibers could be recorded. Under steady stretch conditions, all fibers responded to an increasing BAC with an increase in firing rate. This could be observed already at 0.8 mg/ml BAC. The increase in discharge rate reached at the most 80 imp/s. During intoxication the regularity of firing was higher than in the no-alcohol situation. At blood alcohol concentrations higher than 5 mg/ml, the neuronal activity suddenly dropped to zero, exhibiting an irregular impulse pattern. The increase in discharge rate at steady stretch is regarded to be of minor significance in the explanation of the impairment of motor performance under ethanol. When sinusoidal stretch was applied, the increase in the mean discharge rate was smaller than at steady stretch conditions. Up to about 10 mg/ml BAC the periodical modulation of firing rate during sinusoidal stretch of a large amplitude remained mainly unchanged. After the discharge rate had dropped to zero for the steady stretch condition at high BAC, elicitation of action potentials was always possible using dynamic stretch.

Altered invertebrate nerve function after chronic exposure to low concentrations of alcohol

Previous studies of direct alcohol toxicity on nerve tissue have been carried out using acute, extremely high doses of alcohol. Chronic administration of 20 mM ethanol to the mollusc Aplysia californica was achieved by adding ethanol to surrounding seawater. Although the animals appeared healthy, isolated ganglion cells from treated animals had significantly decreased mean action potential amplitudes and prolonged mean action potential durations compared to controls. These findings suggest that chronic exposure to a low concentration of ethanol comparable to that producing drunkeness in humans may have a direct toxic effect on invertebrate nerve tissue.

Labeling of rat brain synaptosomal phosphatidyl serine in the after state of acute alcoholic intoxication and in the withdrawal state

The synaptosomal phosphatidyl serine labeling by 14-C-serine after elimination of a single dose of 6 g EtOH/kg b.w. and after a prolonged ethanol period (8-11 g EtOH/kg b.w. for 8 days) was studied in vivo. In both experimental groups the 14-C-labeling of the phosphatidyl serine is decreased as compared with the controls. There is a great deal of evidence which implicates that phosphatidyl serine plays a major role in neural excitation providing ion exchanges sites which control the sodium current, known to be sensitive to ethanol. These ethanol induced changes in phosphatidyl serine labeling may be reflected functionally in the impulse conduction and increased sensitivity in the withdrawal state. These changes are suggested to be consequences of the primary membrane fluidity increasing properties of ethanol.

Neuronal aspects of opiate dependence and tolerance in comparison to central depressants

Some acute and chronic effects of opiates and of central depressants have been reviewed, in order that a comparison can be made between the actions of these drugs. Special emphasis has been given to opiate-induced changes at the neuronal level, which have been studied either by the direct microelectrophoretic application of drugs to single neurones or by application of drugs to the myenteric plexus/longitudinal muscle preparation of the guinea pig ileum. Available evidence suggests that chronic exposure of nervous tissue to opiates as well as to central depressants causes changes in neuronal excitability, which become apparent upon withdrawal of the drug. Although opiates and central depressants cause similar changes they appear to do so by different mechanisms. Such differences between the mode of action of opiates and central depressants may provide an explanation for the differing chronic effects of these drugs.

Effects of ethyl alcohol on the directly recorded standing potential of the human eye

The effects of ethanol on the human standing potential (SP) were studied with a recently developed method, which allows direct SP recordings by means of a suction contact lens, temperature stabilized calomel electrodes and d.c. amplification. It is well known that the human SP oscillates with a frequency of about 2/hour in response to a sudden change in illumination. In the present paper marked cyclic variations of the SP, resembling damped oscillations, were provoked by a small oral dose of ethyl alcohol. A first maximum was reached after about 10 min. The difference in amplitude between the peak and the trough of the first oscillation was of the order of 4 mV. The oscillatory frequency was about 2/hour. The length of a cycle varied between 25 and 34 min in different volunteers, being fairly constant in the same subject on different occasions. The SP response to ethanol was similar both under scotopic and photopic conditions. The results correlate well with earlier findings of 2/hour oscillations in c-wave amplitude in response to ethanol, as may be expected considering the partly common origin of the c-wave and the SP.

The effects of aliphatic alcohols on the biophysical and biochemical correlates of membrane function

The simplicity of the structure of aliphatic alcohols suggests that their interaction with receptors in the classical sense is unlikely. The actions of alcohols may involve a relatively nonspecific disruption of cell membranes, possibly physically dissolving into neuronal membranes especially, resulting in the malfunction of normal physiological processes. Studies of alcohol-membrane interactions have employed the use of artificial and nonneural membranes, invertebrate neurons for electrophysiological measurements and brain tissue for studying ion fluxes and enzymatic activities. For the most part these studies have been inclusive because high concentrations of alcohols were needed to elicit any effect. Also, it is difficult to extrapolate the data to in vivo mammalian systems, especially relative to the clinical signs of depression of the central nervous system.