Cutaneous mechanism of electroreceptor temperature sensitivity of the ampullae of Lorenzini

The potential difference on the receptor epithelium of the ampullae of Lorenzini and on the skin and also spike discharges of single electroreceptor nerve fibers in response to temperature stimulation of the region of the pores of the ampullae were studied in the Black Sea skateRaja clavata. Heating the skin in the region of the pore led to the appearance of a positive potential on the skin and on the epithelium of the ampulla, and to inhibition of spike activity. The time course of the change in potential reflected the course of change of temperature; the temperature coefficient was 100–150 µV/°C. Cooling the skin was accompanied by a negative deviation of potential on the skin and in the ampullary canal and by excitation of spike activity. During cooling the temperature coefficient was 30–50 µV/°C. It is concluded that spike activity of electroreceptors reflects changes in potential on the skin due to changes in temperature. The mechanism and biological significance of the phenomena discovered are discussed.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 13, No. 3, pp. 307–314, May–June, 1981.     

Changes in transepithelial potential and spike responses of ampullae of Lorenzini of the skate to temperature stimulation

Response of the sensory epithelium of single ampullae of Lorenzini and spike responses of nerve fibers connected to them to temperature stimulation of the region of the sensory epithelium were studied in experiments on Black Sea skatesRaja clavata. Electrically isolated ampullae with input resistance R=500–800 k, to which an external load (a controllable resistance R_ext) could be connected through a feedback circuit, were investigated. Heating the ampulla was accompanied by the appearance of a negative potential in the canal, and other conditions being the same, its magnitude was an almost linear function of the resultant inward resistance of the preparation [R_in=(R_a·R_ext)/(R_a+R_ext)]. The character and intensity of the spike response of the nerve fiber also was determined by the magnitude of R_in. With a resistance of more than 400–500 k, quickening of spike activity occurred in response to heating, and the degree of quickening increased with an increase in R_in. With a smaller value of R_in, the discharge was inhibited, and the inhibition strengthened as the resistance decreased. The presence of two sources of potential, evoked by a change of temperature and giving rise to opposite spike responses, is discussed.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR. Leningrad I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 14, No. 1, pp. 11–18, January–February, 1982.     

Responses of the ampullae of Lorenzini in a uniform electric field

A linear relationship was established by analysis of discharges from electroreceptors of the ampullae of Lorenzini in a uniform electric field between the potential difference on a single ampulla and the relative change in the spike response of a single fiber. This relationship can serve as the basis for a model of activity of ampullary groups considered as functional units of the electroreceptor system.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 11, No. 2, pp. 158–166, March–April, 1979.     

Effects of calcium and potassium channel blockers on changes in transepithelial potential and spike responses in Lorenzi ampullary electroreceptors in Raja clavata

The effects of TEA, 4-AP, Co⁺⁺, Cd⁺⁺, Cs⁺, EDTA, and verapamil on the sensory epithelium of ampullae of Lorenzini were studied inRaja clavata (Black Sea skate). During voltage clamping, transepithelial application of TEA to the basal surface caused oscillations in transepithelial potentials in response to presentation of an excitatory stimulus, which had been suppressed by Co⁺⁺, Cd⁺⁺, and EDTA. Application of Cs⁺ was followed by complete or partial suppression of spike response adaptation. When applied to the apical epithelial surface, TEA produced an increase in spike response to stimulation and highly accelerated adaption. No substantial changes took place after apical application of Co⁺⁺, Cd⁺⁺, and verapamil. The mechanisms of these phenomena are discussed.Deceased.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 17, No. 5, pp. 652–659, September–October, 1985.     

Mechanism of perception of changes in the magnetic field by ampullae of lorenzini of elasmobranchs

The mechanisms of reception of changes in the magnetic field by electroreceptor formations were investigated in experiments on Black Sea rays in which spike activity was recorded from single nerve fibers connected with the ampullae of Lorenzini. The responses of the ampullae of Lorenzini to magnetic stimulation were shown to be due to induced electric currents creating potential gradients in the body tissues of the fish and the sea water. On the basis of differences in responses of different ampullae to magnetic stimulation, it is possible to distinguish between magnetic stimuli and other stimuli acting on the electroreceptor system. Potentiation of the receptor response to magnetic stimulation was found as the fish came closer to the "shore." The mechanisms and biological importance of reception of changes in the magnetic field by the ampullae of Lorenzini are discussed.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 10, No. 1, 75–83, January–February, 1978.     

Reversal potential for monosynaptic EPSP in frog motoneurons

Experiments were conducted on brain isolated from the frogRana ridibunda using a current chop technique of transmembrane polarization and discrete measurement of membrane potential by a single microelectrode during intervals between waves of current. It was found that the current-voltage relationship of the motorneuron is non-linear; i.e., membrane resistance decreases considerably in step with increased depolarizing current. After the initial reduction, membrane resistance began to climb back when a more protracted current lasting 1–2 min was applied; consequently membrane potential level shifted towards more positive values of +50 mV and above at current levels of 40–60 nA. It then became possible to bring about complete reversal of monosynaptic EPSP produced in the lumbar motoneurons by stimulation of the brainstem reticular formation or by microelectrode stimulation of the ventrolateral tract descending fibers and to measure reversal potential of these EPSP directly, without resorting to computing or extrapolation. Measurements varied mainly between 0 and –10 mV.I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 18, No. 4, pp. 534–542, July–August, 1986.     

Mechanisms of interaction between central neurons and abdominal stretch receptors in the crayfish

Mechanisms of interaction between central and receptor neurons of the crayfish (the principal inhibitory neuron — PIN — and the slow-adapting stretch receptor — SAR) when functioning under different conditions were investigated: during regular spontaneous activity of SAR, grouped discharges of PIN, and regular spontaneous activity of PIN. A close connection was found between the various parameters of the PIN and SAR responses. Adaptation of SAR to the action of adequate, regular repetitive stimulation takes place faster in the presence of stationary background activity of PIN. The appearance and disappearance of SAR spike activity are determined by the ratio between the firing rates of SAR and PIN: at the moment of changeover the neuron with the higher firing rate is predominant.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Institute of Zoology, Academy of Sciences of the Moldavian SSR, Kishinev. Translated from Neirofiziologiya, Vol. 4, No. 4, pp. 429–438, July–August, 1972.     

Determining neuronal response of the rabbit thermoregulatory center to thermal stimulation

A classification was made of neuronal spike activity in the dorso- and ventromedial hypothalamic nuclei. Thermosensitive neurons in which response was accompanied by change in activity pattern could be identified with 0.95 probability by means of an algorithm based on this classification.I. V. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 20, No. 3, pp. 291–301, May–June, 1988.     

Involvement of thalamic neurons and the striopallidal complex in maintaining constancy of visual perception in the human brain

Neuronal activity was investigated in different thalamic nuclei and the striopallidal complex in parkinsonian patients with long-term implantation of intracerebral electrodes in the structures concerned for diagnostic and therapeutic purposes. Directionally selective neurons were found with consistent response to presentation of visual stimuli oriented at the same angle in a variety of (spatial) head positions differing by 90°.Institute of Experimental Medicine, Academy of Medical Sciences of the USSR, Leningrad. Institute of Evolutionary Physiology and Biochemistry, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 21, No. 1, pp. 93–101, January–February, 1989.     

Possible role of voltage-sensitive potassium channels in generation of response in Pacinian corpuscles

The effects of 20 mM tetraethylammonium (TEA) and 5 mM 4-aminopyridine (4-AP) on mechanically and electrically excitable membranes of Pacinian corpuscles were investigated using the air gap technique for producing constant superfusion and recording electrical response at the receptor. The effects of TEA led to a 150% rise in the duration of receptor potential, the amplitude of which declined by 40%. No statistically significant changes in response to mechanical stimulation could be detected after applying 4-AP to the receptor membrane. The two blockers mentioned did modify the membrane of the first nodes of Ranvier, producing a 2–3-fold increase in the duration of action potentials. Computations based on the Dodge model would indicate that the observed effects may be explained by inhibition of voltage-dependent potassium channels which help to transform receptor current into spike response in the intact receptor.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 20, No. 5, pp. 623–630, September–October, 1988.     

Responses of cerebellar Purkinje cells to mechanical stimulation of the Achilles' tendon

Responses of cerebellar Purkinje cells to mechanical stimulation of the Achilles' tendon were studied in unanesthetized decerebrate cats. Approximately two-thirds of the Purkinje cells tested were activated in response to stimulation through climbing fibers, i.e., they generated a complex spike. In half of these cells (group A) the probability of appearance of a complex spike to a blow on the tendon was from 0.5 to 0.9 and the latent period of response from 20 to 25 msec. Purkinje cells with a latent period of response of over 35 msec were characterized by low probability of response (under 0.5) to a tap (group B). Responses of Purkinje cells to excitation of mossy fibers were weaker and more varied.I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 13, No. 2, pp. 159–167, March–April, 1981.     

Changes produced in neuronal excitability by subthreshold depolarization as a possible mechanism of interval selective relationships within the central nervous system

A neuronal process was identified inLymnaea stagnalis nerve cells which may be viewed as one of the mechanisms underlying the interval selectivity previously described in research into the functional relationships between mammalian brain cells. This process takes the form of regularly-occurring changes in excitability resulting in a high probability (of 0.6–1) of neuronal spike response to what had previously been subthreshold depolarizing current pulses following similar subthreshold (conditioning) pulses at intervals specific to each individual neuron. It was found that the cycle of change in neuronal excitability following threshold depolarization did not arise from temporal summation of electrotonic local or postsynaptic neuronal potentials; it was an endogenous (cytoplasmic) process insensitive to transmitter (acetylcholine) application but altering irreversibly under the effects of bombesin, one of the modulator peptides.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad; Institute of Experimental Medicine, Academy of Medical Sciences of the USSR, Leningrad. Translated from Neirofiziologya, Vol. 21, No. 3, pp. 291–299, May–June, 1989.     

Frequency characteristics of skate electroreceptive central neurons responding to electrical and magnetic stimulation

Responses of single neurons in the lateral lobes of the medulla to stimulation of the electroreceptive system by homogeneous sinusoidal electrical and magnetic fields were investigated in acute experiments on the skateRaja radiata. Thresholds of neuronal responses to electrical stimulation varied from 0.03 to 10 µV/cm. The optimal frequency ranges for electrical and magnetic reception were in the regions of 0.05–5 and 2–3 Hz respectively. The possible mechanisms and functional significance of frequency characteristics of central neurons are discussed.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. All-Union Cardiologic Scientific Center, Academy of Medical Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 16, No. 4, pp. 464–470, July–August, 1984.     

Changes in functional characteristics of the compound eye of bees caused by mutations disturbing tryptophan metabolism

The compound eye of worker honeybees with an inborn disturbance of intermediate metabolism of tryptophan — the snow (s) and laranja (la) mutations — has increased sensitivity to light, at least 100 times higher than normal in snow and at least 10 times higher in laranja. The maxima of the spectral sensitivity curves for the whole eye in snow are shifted into the 530 nm region and in laranja to 550 nm (comparedwith 545 nm for the wild type). The electroretinograms of s andla homozygotes are unusual in form on account of the presence of a fast additional component of the receptor potential that is absent in wild-type individuals. This may be the result of immaturity of the pigment granules in the mutants, due to the inherited absence of ommochromes. Pigment granules probably play an important role not only in the formation of the light-protective screen of the ommatidium, but also in biochemical processes considered to be responsible for the electrical passivity of the photoreceptor membrane. The possibility likewise cannot be ruled out that inherited changes in the photoreceptor membranes are connected with an imbalance between derivatives of tryptophan metabolism which participate in the generation of the cell receptor potential.I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry, Academy of Sciences of the USSR, Leningrad. I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 14, No. 1, pp. 69–75, January–February, 1982.     

Distribution of directionally selective neurons within the thalamic nuclei and striopallidal complex of the human brain

Spike activity was analyzed in the course of visual testing for directional sensitivity in 177 neuronal populations in different thalamic nuclei and the striopallidal complex in the brain of nine parkinsonian patients, diagnosed and treated using implanted intracerebral electrodes. Directionally selective neurons were discovered in the centrum medianum, the thalamic zona incerta and reticular nucleus, the caudate nucleus, and the central area of the globus pallidus. Proportions and distribution of neurons with different properties were investigated in the thalamic nuclei and striopallidal complex.Institute of Experimental Medicine, Academy of Medical Sciences of the USSR, Leningrad. Institute of Evolutionary Physiology and Biochemistry, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 21, No. 5, pp. 652–660, September–October, 1989.     

Anesthesia effect on rabbit hypothalamic neuron impulse activity

Neuronal impulse activity in the thermoregulation center in the anterior and posterior sections of the rabbit hypothalamus was studied in chronic experiments and in intravenously injected anesthetics (urethane and chloralose). Anesthesia decreased the neuronal firing rate, changed the impulse activity pattern, and decreased the number of neurons responding to skin thermal stimulation. These changes were most pronounced in the posterior hypothalamic section.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 23, No. 5, pp. 574–579, September–October, 1991.     

Effects of transcranial electrical stimulation of opioid brain structures on regeneration of peripheral nerves in the rat

The effects of transcranial electrical stimulation of opioid brain structures on regeneration of the rat sciatic nerve after transection and microsurgical suturing of the nerve were investigated. Electrical stimulation was found to accelerate regeneration of motor and sensory fibers of the sciatic nerve. The subject of the involvement of endogenous opioid peptides in regeneration of the peripheral nerves is discussed.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 22, No. 1, pp. 76–79, January–February, 1990.     

Evoked potentials in the parafascicular complex of the rabbit thalamus during peripheral noxious stimulation

Systematic research was conducted into the parafascicular complex of the nonspecific nociceptive system of the rabbit hypothalamus using a technique of evoked potentials. Two types of evoked response were recorded during electrocutaneous stimulation of the paw; a compound response consisting of early and late positive-negative potentials in the lateral region and a simple positive-negative evoked potential in the medial area. Evidence suggests a more complex organization of the thalamic parafascicular complex in leporines than previously supposed.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 18, No. 6, pp. 787–793, November–December, 1986.     

Functional characteristics of electroreceptors of the Turkestan catfish

Acute experiments to record spike activity from single fibers of the lateral line nerve of the Turkestan catfish revealed electroreceptor formations which, in their functional characteristics, were similar to the ampullated electroreceptors of other freshwater fish (the so-called small pit organs). The threshold intensity of the uniform electric field was 1 µV/cm. A voltage drop on the skin of the fish was shown to be an effective stimulus for the electroreceptors. A spike response to a change in the magnetic field was found for the first time in electroreceptors of freshwater fish. The threshold level of magnetic induction for a velocity of rotation of the permanent magnet of 1 m/sec was 2.9 · 10^–4 T. Temperature and mechanical sensitivity of the electroreceptors was determined. The biological significance of electroreceptors of the Turkestan catfish is discussed.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. M. I. Kalinin Andizhan Medical Institute, Ministry of Health of the Uzbek SSR. S. M. Kirov Murmansk Marine Biological Institute, Kola Branch, Academy of Sciences of the USSR, Dal'nie Zelentsy. Translated from Neirofiziologiya, Vol. 12, No. 5, pp. 508–516, September–October, 1980.     

Acoustic signal patterns as reflected in the frequency following response of the cat auditory system

In the source of experiments on unanesthetized cats it was shown that all the essential qualities of acoustic stimuli are expressed in the frequency following response (FFR) peculiar to the lower regions of the auditory system (the inferior colliculus included). Amplitude and wave-form of response largely depend on the frequency and intensity of stimulation, frequency and phasic spectra bands for complex signals, together with their wave form and periodicity, acoustic masking of the "useful" signal, and finally interaural differences in stimulation modelling different spatial positions of the sound source.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 19, No. 1, pp. 67–74, January–February, 1987.