[Effect of potassium and calcium channel blockers on changes in the transepithelial potential and spike responses of electroreceptors of the ampullae of Lorenzini in the skate]. / Vliianie blokatorov kalievykh o kal'tsievykh kanalov na izmeneniia transépitelial'nogo potentsiala i impul'snye otvety élektroretseptorov ampul Lorentsini skata.

Action of TEA, 4-AP, Co2+, Cd2+, Cs+, EDTA and verapamile on sensory epithelium of Lorenzinian ampullae was studied in the Black Sea skate Raja clavata. Application of TEA to the basal face of epithelium in current-clamped ampulla caused oscillations of transepithelial potential and oscillatory spike discharges in response to excitatory stimulation. The oscillations were suppressed by Co2+, Cd2+ and EDTA. Application of Cs+ was followed by partial or complete suppression of spike response adaptation. TEA injection into the ampulla produced an increase in the spike frequency reaction and speeding of adaptation. Co2+, Cd2+ and verapamile inside the ampulla caused almost no changes. The contribution of various ionic channels to the function of the electroreceptor cell is discussed.

[Reactions of the ampullae of Lorenzini of the skate to electric stimulation after polarization of the receptor epithelium]. / Reaktsii ampul Lorentsini skata na élektricheskuiu stimuliatsiiu na fone poliarizatsii retseptornogo épiteliia.

Responses of electrically insulated Lorentzinian ampullae to d. c. pulses were studied on skates Raja clavata in the course of polarization of receptor epithelium. With negative polarization of -4 divided by -6 mV reversed changes in spike frequency (acceleration to anodal and inhibition to cathodal pulses) appeared practically without loss of sensitivity, the course of adaptation being unchanged. The data are in accordance with the model described previously suggesting stationary N-shaped voltage-current relation of receptor cell apical membrane.

[Frequency characteristics of central neurons of the electroreceptor system of the skate in response to exposure to electric and magnetic fields]. / Issledovanie chastotnykh kharakteristik tsentral'nykh neironov élektroretseptornoi sistema skata pri deistvii élektricheskikh i magnitnykh polei.

Responses of single units to sinusoidal homogenous electrical and magnetic field stimulation were studied in the lateral-line lobes of the skate Raja radiata. The voltage gradient thresholds were in the range of 0.03-10 microV/cm. Optimal frequency ranges for electrical and magnetic stimuli were 0.05-0.5 and 2-3 Hz, respectively. Possible mechanisms and functional significance of frequency characteristics of the neurons are discussed.

[Electrophysiologic study of the central projections of the ampullae of Lorenzini in the skate]. / Elektrofiziologicheskoe issledovanie tsentral'nykh proektsii ampul Lorentsini u skata.

A large portion of the central nervous system of the skate Raja radiata was examined for responses related to single electroreceptor organs (ampullae of Lorenzini) or their groups. It was shown that electroreceptors project to the anterior lateral lobes of the medulla, caudal portion of the auricles and the mesencephalon. A topographic segregation of electroreceptors (to the anterior lateral lobes) and mechanical lateral afferents (to the posterior lateral lobes) was found. Unit receptive fields in the anterior lateral lobe showed no absolute somatotopic organization of electroreceptive input. Three main types of mesencephalic responses were found: ipsilateral, contralateral and both ipsi- and contralateral.

[Electrical model of the electroreceptor of the ampulla of Lorenzini]. / Elektricheskaia model' élektroretseptora ampuly Lorentsini.

An electrical model is proposed for the Lorenzinian ampulla receptor epithelium. The model is based on the authors' experimental results and explains most of the experimental data available in literature, including an unusual sign of spike response in afferent fibres and complex patterns of electroreceptor responses to the applied stimuli. Its main assumption is an N-shaped voltage-current relation of the receptor cell apical membrane possessing, within the range of operation, a stationary negative-slope resistance.

[Activity of central neurons of the electroreceptor system of Glyptosternum reticulatum]. / Aktivnost' tsentral'nykh neironov élektroretseptornoi sistemy turkestanskogo somika.

Acute experiments with extracellular recording of pulse activity from neurons of lateral lobes of the Turkestan catfish Glyptosternum reticulatum revealed tonic and phasic neurons. Tonic neurons as compared to phasic ones were more sensitive to a potential gradient in water and has spontaneous activity. Phasic neurons had no spontaneous activity, their responses did not depend on the intensity and duration of electric stimuli. The functional significance of the phasic neurons remains so far unclear.

[Study of the receptor mechanisms of the electroreceptors of ampullae of Lorenzini in the skate]. / Issledovanie retseptornykh mekhanizmov élektroretseptorov ampul Lorentsini skata.

Responses of the sensory epithelium of the electrically insulated Lorenzinian ampullae in the Black Sea skates (Raja clavata) as well as their spike frequency reactions to electrical stimulation were studied under the current-clamp conditions. The preparations have the input resistance of 200-800 k omega, the transepithelial resting potential of 0 divided by -2 mV and ordinary impulse activity in afferent fibres. Electroreceptor thresholds were of 2-10 microV (current approximately 10-11 A). With adequate parameters of stimulation (current up to 1 nA, voltage drop across the epithelium to +/-500 microV) the current-voltage relation of the epithelium was linear without any signs of both spike and oscillatory activity of the receptor cells. With negative currents more than 1-10 nA there appeared a regenerative spike in the epithelium. The spike was accompanied by abnormal impulse in an afferent fibre.

[Electroreceptor characteristics of elasmobranchs with pint sources of the electric field]. / Analiz kharakteristik élektroretseptorov plastinozhabernykh rib s pomoshch'iu tochechnykh istochnikov élektricheskogo polia.

Using mathematical modelling methods and experimental data possible space mechanisms of information conversion processes with Lorenzinian ampullary apparatus during detection of the dipole electric field were studied. The space selectivity of the ampullary groups was shown and its biological significance is discussed.

[Effective stimulation of Turkestan catfish electroreceptors]. / Effektivnyi stimul élektroretseptorov turkestanskogo somika.

In Turkestan catfish (Clyptosternum reticulatum) passive electrical properties of the skin, the structure of electrical field near and within the fish as well as single nerve fibre impulse activity of electroreceptors, were studied. The resistance and capacity of the skin were 18-25 kOhm.cm2 and 1 micro F/cm2, resp. The effective stimulus for the electroreceptors involved the voltage drop across the skin. The significance of the skin electrical properties for functional characteristics of electroreceptors is discussed.

[Cutaneous mechanism of the temperature sensitivity of ampulla of Lorenzini electroreceptors]. / Kozhnyi mekhanizm temperaturnoi chuvstvitel'nosti élektroretseptorov ampul Lorentsini.

In acute experiments on Black Sea skates Raja clavata the potential difference across the sensory epithelium and across the skin as well as the impulse activity of single electro-receptors were studied during thermal stimulation of pores of the ampullae of Lorenzini. Heating of the skin near the pore caused a positive potential shift inside the ampullary canal and across the skin (outside with respect to inside) and inhibition of the impulse activity. Cooling of the skin resulted in the opposite effects. Biological significance of the skin mechanism of thermal sensitivity of the ampullae of Lorenzini is discussed.

[Effect of focused ultrasound on the electroreceptor system of skates and certain fish and amphibian tissues]. / Deistvie fokusirovannogo ul'trazvuka na élektroretseptornuiu sistemu skatov i na nekotorye tkani ryb i amfibii.

The effects of focused ultrasound have been investigated on the structures of electroreceptor system of the Black Sea skates (Raja clavata, Dasyatis pastinaca), as well as on the tissues of some other poikilotherms (fishes Belone belone and Solea lascaris, toad Bufo viridis, frog Rana temporaria). It was shown that focused ultrasound evokes excitation (onset of impulse activity) when applied to the pore of electroreceptors and inhibition of the activity when applied to the ampulla itself. The data obtained indicate that thermal conductivity of tissues in poikilotherms is lower than that in homoiotherms.

[Mechanism of temperature sensitivity of ampulla of Lorenzini electroreceptors]. / Issledovanie mekhanizma temperaturnoi chuvstvitel'nosti élektroretseptorov ampul Lorentsini.

In acute experiments on the Black sea skates (Raja clavata) the transepithelial potential of Lorenzinian ampullae and impulse activity of their single nerve fibres were studied during electrical and thermal stimulation. The potential inside the canal and input resistance of the ampulla were 0 divided by -2 mV and 250-400 k omega respectively. Heating of the capsule was accompanied by a negative wave of the potential, an increase in the ampulla resistance and a decrease in spike frequency. Cooling of the preparation caused the opposite changes in the parameters. Waves of the transepithelial potential are supposed to reflect changes in the potential difference across the basal membrane of a receptor cell, which is hyperpolarized by heating.

[Functional characteristics of the electroreceptors of the Turkestan catfish]. / Funktsional'nye kharakteristiki élektroretseptorov turkestanskogo somika.

Experiments with recording of single fibre impulse activity from lateral-line nerve in Turkestan catfish (Glyptosternum reticulatum) show that the fish has a high-sensitive electroreceptor apparatus (threshold value in a uniform electric field was 1 muV/cm). The effective stimulus for the electroreceptors is the voltage drop across the fish skin. Impulse reactions to magnetic stimulation as well as thermal and mechanical sensitivity of the electroreceptors were observed. Biological significance of electroreceptors in Turkestan catfish is discussed.

[Responses of ampullae of Lorenzini in a uniform electric field]. / Reaktsii ampul Lorenzini v odnorodnom électricheskom pole.

Analysis of discharges of a single electroreceptor in a uniform electric field resulted in the conclusion that there is a linear relationship between the potential difference on a single ampulla and relative changes in the spike frequency. The topography of the ampullar groups can be described as a system composed by electric gratings. It is supposed that the maximum of the directional diagram of a grating corresponds to the area of a maximum sensitivity of an ampular group.

[Mechanism of perception of magnetic field changes by the ampullae of Lorenzini of elasmobranchs]. / O mekhanizme vospriiatiia izmenenii magnitnogo polia ampulami Lorentsini plastinozhabernykh ryb.

Investigating the impulse activity from single nerve fibres connected with Lorenzinian ampullae in Black Sea skates, the mechanisms of changing magnetic field detection were studied. It was shown that the receptor to magnetic stimulation were caused by induction of electric currents in fish body or sea water. The peculiarities of receptor responses enable the animal to differ magnetic stimuli from any other stimuli. An increase in fish receptor reaction to magnetic stimulation near the "coast" of the tank was observed. The biological significance of magnetic detection by the Lorenzini ampullae is discussed.