Participation of the adenylate cyclase system in the postsynaptic mechanism of heterosynaptic facilitation

In an analysis of the postsynaptic mechanism of heterosynaptic facilitation, changes in the amplitude of the excitatory postsynaptic current (EPSC) and the current evoked by application of acetylcholine (ACh current), acting on the adenylate cyclase system of the LC-1 and RC-1 neurons of the molluskPlanorbis corneus, were compared. Both responses are n-cholinergic and depend on the membrane conductivity for Na⁺ and K⁺. Application of serotonin led to a 100–300% increase in the amplitude of the EPSC and (in most cases) the ACh current. However, in 30% of the cases, the increase in the EPSC was accompanied by a decrease in the ACh current. This is probably due to the different contributions of Na⁺ and K⁺ to the mechanism of activation of the conductivity of th channel-receptor complex of the nonsynaptic cell membrane. The influence of serotonin on the EPSC and ACh current was simulated by the action of phosphodiesterase blockers and adenylate cyclase activators. Phosphodiesterase activators and protein kinase blockers reversibly inhibited the EPSC and ACh current. Thus, activation of the adenylate cyclase system, mediated by the action of serotonin, promotes the development of a postsynaptic mechanism of formation of heterosynaptic facilitation of the EPSC in the command neurons of the mollusk.A. A. Bogomolets Institute of Physiology, Ukrainian Academy of Sciences, Kiev. Translated from Neirofiziologiya, Vol. 23, No. 6, pp. 676–683, November–December, 1991.     

Calcium currents of differentiated mouse neuroblastoma cells

Differentiated mouse neuroblastoma cells (line C 1300, clone N-18-TG₂A₁) were investigated by intracellular dialysis. A slow component was found in the potential-dependent inward current of these cells. The results of investigation of changes in amplitude of this component during variation of the ionic composition of the external and internal solutions showed that this component is due to transport of calcium ions. A calcium current was observed in all cells tested. The region of its activation was between –70 and –65 mV; maximal values of this current were reached when the membrane potential was between –30 and –40 mV. The kinetic characteristics of this current were examined. In its kinetics and potential-dependence, this calcium current of the mouse neuroblastoma cell membrane is analogous to the fast component of the calcium current in normal neurons of rat spinal ganglia.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 16, No. 4, pp. 527–531, July–August, 1984.     

Investigation of the TEA-resistant outward current in the somatic membrane of perfused nerve cells

Outward currents remaining after addition of 20–50 mM of tetraethylammonium (TEA) ions to the extracellular or intracellular solution, were investigated in perfused isolatedHelix neurons. After this addition, the inactivated inward current carried by potassium ions, the potential-dependent and kinetic characteristics of which differ from those of potassium outward currents suppressed by TEA, is preserved in the membrane. A component dependent on the inward calcium current was found in this TEA-resistant outward current; it was abolished by replacement of the extra-cellular calcium ions by magnesium ions, by blocking of the calcium channels by extracellular cadmium ions, and by their destruction by intracellular fluoride ions. Increasing the intracellular concentration of free calcium ions by perfusing the cell with solutions containing calcium-EGTA buffer potentiated the TEA-resistant component of the outward current, whereas removal of these ions with EGTA weakened it. It is concluded that a system of outward current channels whose activation depends on the presence of calcium ions near the inner surface of the membrane is present in the somatic membrane. It is suggested that to keep these channels capable of being activated, calcium ions must bind with the structures forming their internal opening.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 11, No. 5, pp. 460–468, September–October, 1979.     

Mechanism of action of nitric oxide donors on voltage-activated calcium channels in vascular smooth muscle cells

The effects of nitric oxide (NO) donors on inward barium current (I _Ba) in freshly isolated smooth muscle cells (SMC) of the guinea pig mesenteric artery and on inward calcium current (I _Ca) in SMC of the canine coronary artery were studied using a patch-clamp recording technique in whole-cell configuration. The inward current in SMC of the guinea pig artery was shown to flow through a single type of calcium channels, which have characteristics of high-threshold slowly inactivated channels of L-type. Nitroglycerin (NG) and sodium nitroprusside (NP) reversibly inhibitedI _Ba in a dose-dependent manner. Effects of NO donors onI _Ba were related to the changes in voltage-dependent properties of calcium channels. In particular, NG and NP accelerated the current inactivation, and their blocking effects increased with the membrane depolarization. Methylene blue, the guanylate cyclase inhibitor, decreased the inhibitory action of NG onI _Ba by a factor of 5. 8-Bromo-cGMP, the membrane-permeant cGMP analog, evokedI _Ba inhibition similar to that caused by NO donors. In the canine coronary artery, NO donors also inhibitedI _Ca flowing through the L-type calcium channels. It has been concluded that NO originating from NG and NP inhibits activity of L-type calcium channels in vascular SMC; it is possible that cGMP-dependent processes are involved.Neirofiziologiya/Neurophysiology, Vol. 28, No. 6, pp. 296–304, November–December, 1996.     

GABA-Mediated Inhibition in Cultured Neurons of the Rat Brain Cortex

In cultured pyramidal neurons of the rat brain cortex, we recorded (in the whole-cell configuration) postsynaptic currents (PSC) evoked by direct electrical microstimulation of an axon of the interneuron adjacent to the pyramidal cell. Application of 5 M bicuculline rapidly, entirely, and reversibly blocked these currents. Linear changes in the holding potential on the membrane of the postsynaptic cell resulted in linear changes in the amplitude of averaged currents. The currents underwent reversion when the holding potential was –16 mV, which was close to the reversal potential for Cl^- ions at their respective concentrations in the extra- and intracellular solutions. We conclude that the recorded currents are inhibitory PSC (IPSC) mediated by GABA release. The amplitudes of the recorded currents varied from a measurable minimum (8 pA) to more than 150 pA at a holding potential on the postsynaptic cell membrane of –80 mV. Times to peak of the high- and low-amplitude currents showed no significant differences, being about 6.4 msec on average. Decays of the current could be satisfactorily approximated by a monoexponential function with a mean time constant of 17 msec. The time constants of IPSC decay were distributed accordingly to the Gaussian law. In some cases, the amplitude distributions of IPSC were unimodal ((with a rightward asymmetry), but in most cases they were clearly polymodal. The amplitude distribution can be described by the sum of several Gaussian distributions; the distance between modes of the Gaussians was 25 ± 6 pA, on average. The obtained estimates of the amplitude of monoquantal GABA-induced IPSC in neurons of the brain cortex allow us to conclude that in various CNS regions the dimension of the vesicles in GABA-ergic synapses formed by inhibitory interneurons is identical.     

Ca2+ ion reversibly inhibits the cytoplasmic streaming ofNitella

Summary When Ca²⁺, K⁺ or Cl^– was injected iontophoretically into the cytoplasm of intactNitella cell, only Ca²⁺ reversibly inhibited the cytoplasmic streaming. However, when an extremely large current was used, the cytoplasmic streaming was reversibly inhibited irrespective of the ion species. This inhibition may be due to a transient increase of free Ca²⁺.     

Effect of intracellular cyclic AMP injection on calcium current in identifiedHelix pomatia neurons

The effect of intracellular injection of cyclic AMP (cAMP) and extracellular application of theophylline on the inward calcium current was investigated in neurons RPa3 and LPa3 ofHelix pomatia. Iontophoretic injection of cyclic AMP (current 10–35 nA, duration about 1 min) led to a decrease in amplitude of the calcium current to a new stationary level, which depended on the injection current. After the end of injection the calcium current was restored to its initial level. Current-voltage characteristic curves of the calcium current were not shifted along the voltage axis by cAMP injection, indicating that the reduction in this current was connected with a change in maximal calcium conductance. An increase in the frequency of depolarizing shifts from 0.1 to 0.5 Hz caused a decrease in the calcium current but did not affect the time course of the decrease in calcium current in response to injection of cAMP or the time course of its recovery after the end of injection. Theophylline an inhibitor of cyclic nucleotide phosphodiesterase, in a concentration of 1 mM in the external solution, lowered the amplitude of the calcium current by 50–75% of its initial value. In 40% of neurons, abolition of the action of theophylline by rinsing was incomplete, but in the rest the effect of theophylline was irreversible. It is postulated on the basis of the results that cytoplasmic compounds take part in regulation of the calcium current of molluscan neurons. The possible physiological role of this process is discussed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 14, No. 3, pp. 290–297, May–June, 1982.     

Effect of strychnine,hydrastine, and apamine on synaptic transmission in smooth muscle cells

The action of strychnine, hydrastine, and apamine on neuromuscular transmission in the stomach and taenia coli was investigated. Hydrastine and strychnine increase nonadrenergic IPSPs of smooth muscle cells. Under the influence of apamine the IPSP and hyperpolarization evoked by exogenous ATP are reversibly blocked and noncholinergic EPSPs appear; ATP, however, does not cause depolarization of the cell membrane. Consequently, apamine is a specific blocker of nonadrenergic inhibition, acting on the postsynaptic membrane, and ATP is a mediator both of this inhibition and of noncholinergic synaptic excitation discovered in smooth muscle cells.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 10, No. 3, pp. 295–299, May–June, 1978.     

Monosynaptic pathway responsible for generation of bursting activity in theHelix pomatia RPal neuron

The connection between a visceral ganglia interneuron initiating bursting pacemaker activity in the RPal neuron and the RPal neuron itself was investigated inHelix pomatia. Stimulating the interneuron either initiated or intensified bursting activity in the RPal neuron, depending on initial electrical activity in this cell. Replacing calcium with magnesium ions in the extracellular fluid and adding CdCl₂ to this fluid reversibly inhibited the effect of interneuronal stimulation on the RPal neuron. The latter effect was unaffected by increasing the concentration of extracellular Ca²⁺ 10 to 70 mM. Intracellular injection of both Cs⁺ and TEA into the interneuron produced an increase in the duration of its action potentials and rendered the link connecting the neurons more effective. It is deduced that a monosynaptic chemical connection exists between the interneuron and the RPal neuron for which a peptide compound serves as transmitter.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 19, No. 1, pp. 20–28, January–February, 1987.     

Characteristics of odorant elicited calcium fluxes in acutely-isolated chick olfactory neurons

To understand avian olfaction, it is important to characterize the peripheral olfactory system of a representative bird species. This study determined the functional properties of olfactory receptor neurons of the chicken olfactory epithelium. Individual neurons were acutely isolated from embryonic day-18 to newborn chicks by dissection and enzymatic dissociation. We tested single olfactory neurons with behaviorally relevant odorant mixtures and measured their responses using ratiometric calcium imaging; techniques used in this study were identical to those used in other studies of olfaction in other vertebrate species. Chick olfactory neurons displayed properties similar to those found in other vertebrates: they responded to odorant stimuli with either decreases or increases in intracellular calcium, calcium increases were mediated by a calcium influx, and responses were reversibly inhibited by 100 M L–cis–diltiazem, 1 mM Neomycin, and 20 M U73122, which are biochemical inhibitors of second messenger signaling. In addition, some cells showed a complex pattern of responses, with different odorant mixtures eliciting increases or decreases in calcium in the same cell. It appears that there are common features of odorant signaling shared by a variety of vertebrate species, as well as features that may be peculiar to chickens.     

Chemical specificity of synapses of frog midbrain tectum

The effects of anticholinesterase preparations and cholinolytics on the potentials of the midbrain tectum evoked by stimulation of the optic tract and the opposite hemisphere were investigated in experiments on the perfused isolatedRana temporaria head. Low concentrations of galanthamine and eserine intensify the first and second postsynaptic components of the evoked potentials connected with the activation of both myelinated and unmyelinated fibers, and in higher concentration, first increase, and then reversibly inhibit them. Amisyl, depending on the concentration, partially or completely blocks both components and these effects are also reversible. Gangleron does not have an effect on the evoked potentials. A clear antagonism was found between anticholinesterase compounds and amisyl. After tetanic stimulation of both optic nerves simultaneously, a substance of acetylcholine nature appears in the perfusate. This makes it possible to assume that the optic terminals in the midbrain tectum form cholinergic synapses and that the corresponding postsynaptic structures contain cholineroreceptors of the muscarine type. Some differences in the dynamics of the changes in the first and second postsynaptic components from the effect of both galanthamine and eserine, as well as amisyl, indicate higher sensitivity of synaptic systems which consist of unmyelinated optic fibers. In contrast to the optic terminals, the transcommissural links do not form cholinergic synapses and anticholinesterase and cholinolytic substances do not have an effect on the transcommissural potentials.A. N. Severtsov Institute of Evolutionary Animal Morphology and Ecology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 3, No. 4, pp. 386–393, July–August, 1971.     

Evoked pre- and post-synaptic activity in the optic tectum of the cannulated tadpole

Summary We describe the cannulated Rana pipiens, tadpole preparation that allows for stable recording in the tectum of the extracellular potential elicited by optic nerve stimulation. The largest components of the evoked tectal response consist of two previously identified waves and a major third, long-latency wave of long duration. These components were reversibly eleminated by perfusion of high magnesium/no calcium Ringer's solution or Ringer's solution containing cobalt chloride. In contrast, perfusion of high calcium/no magnesium Ringer's increased the amplitude and area of these components. We conclude that these components represent post-synaptic activity.Additionally, small, short-duration waves were identified as arising from the activity of retinal afferents. They consisted of a short-latency (3.1–7.6 ms) and a long-latency (12–23 ms) group. Waves belonging to both of these classes were still visible in both high magnesium/ no calcium Ringer's solution or Ringer's solution containing cobalt chloride and were unaffected by high calcium/no magnesium Ringer's. The average conduction velocities of the short- and long-latency groups matched the conduction velocities of, respectively, edge and convexity detectors in the adult. This indicates that retinal afferent input may already be present in adult patterns at the time that tectal circuitry is developing.Abbreviations TTX tetrodotoxin - NMDA N-methyl-D-aspartate - APV 2-amino-5-phosphonovaleric acid     

Effects of applying oxytocin to Helix pomatia neurons. I. Depolarization

Inward current produced by applying oxytocin (OT) to the neuronal soma (OT_I) current) under conditions of voltage-clamping at the cell membrane was investigated inHelix pomatia. Replacing sodium with Tris ions in the external medium produced a considerable decline in OT_I current. A reduction in the external concentration of chlorine ions by replacement with HEPES ions induced an increase in OT_I current and a shift in its current-voltage relationship towards depolarization values. The presence of furosemide in the external solution reversibly inhibited OT_I current. This current likewise declined reversibly following external application of imidazole and tolbutamide but was increased by theophylline action. It was inferred that OT receptors are present on the surface membrane of someHelix neurons which, when activated, lead to increased chlorine permeability — a process apparently mediated via the cyclic nucleotide system.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR. Kiev. Translated from Neirofiziologiya, Vol. 20, No. 5, pp. 652–659, September–October, 1988.     

Effects of α-latrotoxin on synaptic transmission between identified neurons in the snail central nervous system

The effects of -latrotoxin — a component of black widow spider venom — on an identified monosynaptic peptidergic synapse were investigated in the central nervous system ofHelix pomatia. Extracellular and intracellular application of the toxin was found to increase and block postsynaptic current respectively. Current induced by intracellular injection of cAMP which imitates postsynaptic current was inhibited, irrespective of the mode of toxin application. It was concluded on the basis of the experiments performed that -latrotoxin manifests its reinforcing effect, acting on the transmitter release system in the presynaptic neuron. It can also induce an inhibitory effect, however, operating on the postsynaptic cell direct — an effect which may be mediated by the cAMP system.A. A. Bogomolets Institute of Physiology, Ukrainian Academy of Sciences, Kiev. A. A. Bogomolets Medical Institute of Biochemistry, Ukrainian Academy of Sciences, Kiev. Translated from Neirofiziologiya, Vol. 24, No. 4, pp. 430–437, July–August, 1992.     

Ionic basis of methacholine-induced shrinkage of dissociated eccrine clear cells

Summary Apical membrane currents were recorded from the taste pore of single taste buds maintained in the tongue of the rat, using a novel approach. Under a dissection microscope, the 150-m opening of a saline-filled glass pipette was positioned onto single fungiform papillae, while the mucosal surface outside the pipette was kept dry. Electrical responses of receptor cells to chemical stimuli, delivered from the pipette, were recorded through the pipette while the cells remained undamaged in their natural environment. We observed monophasic transient currents of 10-msec duration and 10–100 pA amplitude, apparently driven by action potentials arising spontaneously in the receptor cells. When perfusing the pipette with a solution of increased Na but unchanged Cl concentration, a stationary inward current (from pipette to taste cell) of 50–900 pA developed and the collective spike rate of the receptor cells increased. At a mucosal Na concentration of 250mm, the maximal collective spike rate of a bud was in the range of 6–10 sec^–1. In a phasic/tonic response, the high initial rate was followed by an adaptive decrease to 0.5–2 sec^–1. Buds of pure phasic response were also observed. Amiloride (30 m) present in the pipette solution reversibly and completely blocked the increase in spike rate induced by mucosal Na. Amiloride also decreased reversibly the stationary current which depended on the presence of mucosal Na (inhibition constant near 1 m). During washout of amiloride, spike amplitudes were first small, then increased, but always remained smaller than the amiloride-blockable stationary current of the bud. This is understandable since the stationary current of a bud arises from a multitude of taste cells, while each current spike is presumably generated by just one taste cell. We suggest that, in a Na-sensitive receptor cell, (i) the apical amiloride-blockable Na inward current serves as a generator current causing cell depolarization and firing of action potentials, and (ii) each current spike recorded from the taste pore arises mainly from a modulation of the apical Na inward current of this cell, because the action potential generated by the taste cell will transiently decrease or abolish the driving force for the apical Na inward current. The transients are indicators of receptor cell action potentials, which appear to be physiological responses of taste cellsin situ.     

Cholinergic modulation of the synaptic transmission in the frog spinal cord

It was found during experiments on isolated frog spinal cord involving extracellular recording from the dorsal roots (sucrose bridging) and intracellular recording from motoneurons by microelectrodes that 10 mM of the M-cholinomimetic arecoline produces motoneuronal depolarization which is matched by depolarizing electronic ventral root potentials and a rise in motoneuronal input resistance. Arecoline changes synaptic transmission by increasing the amplitude of postsynaptic potentials during intracellular recording and that of motoneuronal reflex discharges in the ventral roots but reduces the duration of dorsal root potentials. In the presence of arecoline, L-glutamate-induced motoneuronal response increases. Facilitation of synaptic transmission produced by arecoline in the spinal cord is bound up with cholinergic M₂- activation, since it is suppressed by atropine but not by low concentrations of pirenzipine; it is also coupled with a reduction in adenylcyclase activity. When motoneuronal postsynaptic response has been suppressed, as in the case of surplus calcium or theophylline, arecoline produces an inhibitory effect on the amplitude of motoneuronal monosynaptic reflex discharges which is suppressed by pirenzipine at a concentration of 1×10^–7 M. This would indicate the presence at the primary afferent terminals of presynaptic cholinergic M₁ receptors which mediate its inhibition of impulses of transmitter release. This effect is independent of changes in cyclic nucleotide concentration.A. M. Gorkii Medical Institute, Donetsk. Translated from Neirofiziologiya, Vol. 19, No. 3, pp. 399–405, May–June, 1987.     

Calcium-regulated phosphorylation of proteins in the membrane-matrix compartment of the Chlamydomonas flagellum

Crosslinking of surface-exposed domains on certain Chlamydomonas flagellar membrane glycoproteins induces their movement within the plane of the flagellar membrane. Previous work has shown that these membrane glycoprotein movements are dependent on a critical concentration of free calcium in the medium and are inhibited reversibly by calcium channel blockers and the protein kinase inhibitors H-7, H-8, and staurosporine. These observations suggest that the flagellum may use a signaling pathway that involves calcium-activated protein phosphorylation to initiate flagellar membrane glycoprotein movements. In order to pursue this hypothesis, we examined the calcium dependence of phosphorylation of flagellar membrane-matrix proteins using an in vitro system containing [γ-³²P]ATP or [³⁵S]ATPγS. Using only endogenous enzymes and endogenous substrates found in the membrane-matrix fraction obtained by extraction of flagella with 0.05% Nonidet P-40, we observed both calcium-independent protein phosphorylation and calcium-dependent protein phosphorylation in addition to an active protein dephosphorylation activity. Addition of micromolar free calcium increased the amount of protein phosphorylation severalfold. Calcium-activated protein kinase activity was inhibited by H-7, H-8, and staurosporine, the same protein kinase inhibitors that inhibit the calcium-dependent glycoprotein redistribution in vivo. A small group of polypeptides in the 26–58 kDa range exhibited a dramatic increase in phosphorylation in the presence of 20 μM free calcium. We suggest that Chlamydomonas utilizes the intraflagellar free calcium concentration to regulate the phosphorylation of specific flagellar proteins in the membrane-matrix fraction, one or more of which may be involved in regulating the machinery responsible for flagellar membrane glycoprotein redistribution.     

Serotonin receptor activation reduces calcium current in an acutely dissociated adult central neuron

The release of serotonin (5-HT) from the terminals of serotonergic (raphe) neurons is under inhibitory feed-back control. 5-HT, acting on raphe cell body autoreceptors, also mediates inhibitory postsynaptic potentials as a result of release from collaterals from neighboring raphe neurons. This may involve a ligand (5-HT)-gated increase in the membrane potassium conductance, leading to a decrease in action potential frequency, which could indirectly reduce calcium influx into nerve terminals. In this report we demonstrate that 5-HT can also directly reduce calcium influx at potentials including and bracketing the peak of calcium current activation. Using acutely isolated, patch-clamped dorsal raphe neurons, we found that low concentrations of 5-HT and the 5-HT1A-selective agonist 8-OH-DPAT reversibly decrease whole-cell calcium current. This effect is antagonized by the putative 5-HT1A-selective antagonist NAN 190. Hence, the inhibition of calcium current may serve a physiological role in these cells and elsewhere in the brain.     

Electrogenic responses elicited by transmembrane depolarizing current in aerated body wall muscles ofDrosophila melanogaster larvae

Summary Electrical excitability of the longitudinal ventrolateral body wall muscle of the third instar larva ofDrosophila melanogaster was demonstrated. This is in contrast to previous papers which have reported that this muscle is electrically inexcitable. It was found that an air supply to the muscle through the tracheoles is essential for maintaining its excitability. In an aerated preparation, the muscle maintained a resting potential of around –80 mV for more than 1.5 h, while a nonaerated muscle depolarized to about –30 mV within 30 min. Muscles with resting potentials larger than –70 mV showed graded regenerative potentials with a double-peaked configuration in response to transmembrane depolarizing current. A tetrodotoxin- (TTX-)sensitive, voltage-dependent inward sodium current, and a tetraethylammonium-(TEA-)sensitive, voltage-dependent outward potassium current were found to be responsible for the first peak of the electrogenic response of this muscle. The rising phase of the second peak was caused by a cobalt/manganese-sensitive, voltage-dependent inward calcium current that had a threshold level near –40 mV. Elimination by TEA or barium of the delayed rectification following the first peak caused the second peak to be triggered at a lower threshold. The second peak was profoundly elongated by barium, and this effect was antagonized by external calcium. Thus, the falling phase of the second peak was most likely driven by a calcium-dependent, outward potassium current.     

Possible mechanisms of dendritic potential habituation in the cat association cortex

The effect of application of strychnine and calcium and of post-tetanic potentiation on the dynamics of gradual decay of dendritic potentials in the association cortex, which is regarded as monosynaptic habituation, was studied in acute experiments on cats anesthetized with pentobarbital. Despire a significant increase in amplitude of dendritic potentials after strychnine application or calcium enrichment of the physiological saline, the time course of habituation was unchanged. The course of habituation also remained unchanged during post-tetanic potentiation. It is concluded that habituation of dendritic potentials is due to processes taking place in the postsynaptic dendrite membrane itself and is independent of postsynaptic inhibition or transmitter exhaustion in presynaptic endings.I. S. Beritashvili Institute of Physiology, Academy of Sciences of the Georgian SSR, Tbilisi. Translated from Neirofiziologiya, Vol. 16, No. 2, pp. 208–213, March–April, 1984.