[Mechanisms of synaptic transmission in the ampullae of Lorenzini in skates]. / Issledovanie mekhanizmov sinapticheskoi peredachi v ampulakh Lorentsini skatov.

Effects of Mg2+, L-glutamate (L-GLU) and L-glutamic acid diethyl ester (GDEE) on background and evoked activity of the ampullae of Lorenzini were studied in marine skates (Raja clavata). Perfusion of the basal membrane with 10(-4)-10(-5) M L-GLU produced significant and reversible changes in background firing rate depending on its initial level. When excitability was blocked by perfusion with Mg2+, the background activity could be restored in L-GLU (10(-4)-10(-5) M) Mg2+-containing solution. GDEE (10(-3)-10(-4) M) blocked the synaptic transmission. The results are consistent with the view that L-GLU is the synaptic transmitter in the ampullae of Lorenzini of the skate.

[Effect of calcium ions on the electrical and temperature sensitivity of the ampullae of Lorenzini of Black Sea skates]. / Vliianie ionov kal'tsiia na élektricheskuiu i tempreaturnuiu chuvstvitel'nost' ampul Lorentsini chernomorskikh skatov.

Changes in the ambient calcium concentration affected similarly both thermal and electrical sensitivity of electroreceptors of the Lorenzini ampullae in the skates. In Ca-free solution containing EGTA the sensitivity first decreased, then increased and after that blocking of synaptic transmission occurred. In Ca-rich solution both thermal and electrical sensitivity decreased. Changes of spontaneous activity occurred much later than those of evoked responses.

[Analysis of the mechanism of amplitude change in Pacinian corpuscle receptor potential in a solution with a decreased calcium ion concentration]. / Analiz mekhanizma izmeneniia amplitudy retseptornogo potentsiala telets Pachini v rastvore s ponizhennoi kontsentratsiei ionov kal'tsiia.

The effect of Ca2+-free solution on the amplitude increase in the receptor potential (RP) of Pacinian corpuscles was studied using external perfusion technique. The RP amplitude increased in Ca2+-free solution. It was blocked after addition of 10-20 mM of tetraethylamonium. A temporary increase in the RP amplitude is seen in the solution with 0.2 mM of 2.4-dinitrophenol. Sensitivity of the receptor membrane to mechanical stimuli does not change in Ca2+-free solution. It is suggested that near the mechanosensitive ionic canal of Pacinian corpuscle receptor membrane the fixed negative charges which could influence the "gate" system state of the mechanosensitive canal are absent.

[Analysis of the mechanism of perception of temperature stimuli by the ampullae of Lorenzini of Black Sea skates]. / Analiz mekhanizma vospriiatiia temperaturnykh stimulov ampulami Lorentsini chernomorskikh skatov.

The single nerve fibre responses of the Lorenzini ampulla to thermal stimulation were studied in the Black Sea skates, Trygon pastinaca, and Raja clavata. Cooling of sea water applied to the ampulla capsule or to the skin overlying the sensory organ increased firing rate wheras warming led to transient decrease in frequency. The thermal sensitivity or receptors was found to depend on threshold to electric current. Static discharge rate of the receptors has positive or negative temperature coefficient according to the temperature range. Cooling of sea water increased the latency of response to electric stimuli. Biological significance of the thermal sensitivity of the Lorenzini ampulla is discussed.