Change in the activity of Na+/K+ pump and its effect on the spontaneous bioelectric activity of neuron of the garden snail Helix pomantia L. in the magnetic field

aktivnost neurona ima veliki značaj jer je magnetno polje umerene jačine prisutno u životnoj sredini. Jednako važno je i proučavanje mehanizama delovanja umereno jakog statičkog magnetnog polja na biofizičke osobine membrane neurona usled sve veće terapijske primene ovog polja, s tim što odgovarajuća jačina polja i dužina izlaganja polju tek treba da budu precizno određene. Uporednim eksperimentima primenom tehnike intracelularne registracije utvrđeno je da kratkotrajno izlaganje (15 min) umereno jakom statičkom magnetnom polju jačine 2,7 mT i 10 mT dovodi do promena bioelektrične aktivnosti spontano aktivnog Br neurona, dok promene nisu uočene kod nemog N1 neurona. Magnetno polje od 2,7 mT povećalo je amplitudu i skratilo trajanje akcionog potencijala, dok je magnetno polje od 10 mT hiperpolarisalo membranu, povećalo amplitudu, smanjilo frekvenciju i trajanje akcionog potencijala Br neurona. Veličine promena ispitivanih parametara zavisile su od jačine magnetnog polja i uočavane su i tokom perioda od 20 min nakon prestanka izlaganja Br neurona polju od 2,7 mT i 10 mT. Kombinovanim eksperimentima, biohemijskim analizama i 31P NMR spektroskopijom na okoloždrelnom ganglijskom kompleksu kao i tehnikom intracelularne registracije na Br neuronu vinogradskog puža, pronađeno je da kratkotrajno izlaganje (15 min) statičkom magnetnom polju jačine 10 mT povećava aktivnost Na+/K+ pumpe. Povećana aktivnost Na+/K+ pumpe dovodi do povećanja potrošnje ATP-a, kao i povećanja pHi posredstvom povećanja aktivnosti Na+/H+ izmenjivača, pH regulatornog sistema čija je aktivnost zavisna od gradijenta Na+ jona koji stvara i održava Na+/K+ pumpa. Rezultati elektrofizioloških eksperimenata na Br neuronu u saglasnosti su sa rezultatima dobijenim na okoloždrelnom ganglijskom kompleksu...It is important to investigate the effects of moderate intensity static magnetic field on the bioelectric activity of neurons, since this field is present in the environment. Equally important is to reveal the mechanism of action of moderate intensity static magnetic field on biophysical properties of neuronal membranes, as this field has been applied in disease treatment, whereby proper dosages of exposure still need to be determined. Comparative intracellular registration studies showed that short term exposure (15 min) to the moderate intensity static magnetic field of 2,7 mT and 10 mT strength changed bioelectric activity of the spontaneously active Br neuron, while bioelectric activity of silent N1 neuron remained unchanged. The 2,7 mT magnetic field increased amplitude and decreased duration of action potential, whereas the 10 mT magnetic field hyperpolarized membrane potential, increased amplitude, decreased firing frequency and duration of action potential of the Br neuron. The magnitude of change of measured bioelectric parameters depended on the strength of applied magnetic field, and was still observed during the period of 20 min after exposure of Br neuron to the 2,7 mT and 10 mT magnetic field. Combined experiments, using biochemical analysis and NMR spectroscopy on whole snail brains and intracellular registration on Br neuron, showed that short-term exposure (15 min) to the 10 mT magnetic field increased activity of Na+/K+ pump. Increased Na+/K+ pump activity in the snail brain caused an increase in ATP consumption and increase in the pHi which is mediated through an increase in the activity of Na+/H+ exchanger, a pH regulatory system governed by the gradient of Na+ ions created and maintained by Na+/K+ pump. Electrophysiology from Br neuron is in agreement with the results obtained on the whole snail brain..