[Study of optical absorption of sensitizers in vivo].

The subject of the paper is study of optical absorption of sensitizers in biological tissue. The study shows that absorbance can be used as a tool that allows studying biodistribution of sensitizers and their interaction with tissue in vivo. The article presents a simple technique of determining biological tissue absorption in vivo, and discusses the results of experimental animal studies of some sensitizers.

[Role of calcium ions in frequency accomodation of rat hippocampal neurons]. / Rol' ionov Ca v chastotnoi akkomodatsii neironov gippokampa krys.

Electrophysiological investigations of extracellular Ca ions the influence on the mechanism of frequency accommodation were carried out on isolated rat hippocampal neurones. It is established that interpulse interval during potential generation action linearly depended on quantity of Ca ions, which enter the cell through Ca2+ channels. Analysis of the results has shown that Ca ions influenced the forming and parameters of frequency accommodation in hippocampal neurones, probably via activation of Ca-dependent outward K-currents. Theoretical model that quantitatively describes the mechanisms of frequency adaptation is proposed. Adequacy of model to experimental data on frequency accommodation and electrical activity of hippocampal neurones is estimated.

[Electrochemical studies of induced secretion of catecholamines from individual vesicles of rat chromaffin cells]. / Elektrokhimicheskie issledovaniia indutsiruemoi sekretsii katekholaminov iz odinochnykh vezikul khromaffinnykh kletok krysy.

Influence of agents inducing secretion: KCl-induced membrane depolarization and acetylcholine on catecholamine secretion from individual vesicles of rat chromaffin cells was studied by using amperometric methods. It has been shown that secretory components participating in these processes are different. An importance of cellular response on different kind of stimulation is discussed.

[The effect of intracellular calcium on an increase in the cAMP-mediated calcium current]. / Issledovanie vliianiia vnutrikletochnogo kal'tsiia na uvelichenie kal'tsievogo toka, oposredovannoe tsAMF.

Intracellularly perfused neurons of Helix pomatia in which serotonin-induced increase of calcium current (Ica) is mediated by cAMP were studied by the voltage clamp technique. It was established that an increase of the calcium intracellular concentration ([Ca2+]i) caused inhibition of the serotonin (5-HT) effect. The 5-HT effect value at 10(-6) and 10(-7) mol/l [Ca2+]i was 60 and 32% of the control one, respectively. Addition of the calmodulin antagonist (5.10(-5) M trifluoperasine) and phosphodiesterase blockers (5 mM theophylline or 10(-4) mol/l IBMX) sharply reduced the Ca2+ ability to inhibit the 5-HT effect. It is concluded that the Ca(2+)-calmodulin-dependent phosphodiesterase is a key link in the interaction between two signal transduction pathways--Ca2+ and cAMP in modulation of the calcium channel activity.

[The effect of cAMP on the calcium currents of mollusk neurons possessing different sensitivities of their calcium conductance to serotonin action]. / Vliianie tsAMF na kal'tsievye toki neironov molliuskov, obladaiushchikh razlichnoi chuvstvitel'nost'iu ikh kal'tsievoi provodimosti k deistviiu serotonina.

The action of cAMP (100 microM) and serotonin (5-HT, 1-10 microM) on the calcium current (Ica) in intracellularly perfused Helix pomatia neurons was studied with voltage clamp method. Three types of 5-HT-induced changes in the calcium current were observed in different cells: reversible blockade, increase and no changes in the current amplitude. Intracellular introduction of exogenous cAMP (100 microM) affected Ica only in cells with the stimulatory effect of 5-HT; cAMP-induced increase in the current amplitude was not additive to that elicited by 5-HT while both of these effects were similarly potentiated by cyclic nucleotide-phosphodiesterase inhibitor. The data presented show that the stimulatory action of 5-HT on the potential-activated calcium current is mediated by an increase in intracellular cAMP. Existence of two types of calcium channels differing in their dependence on cAMP metabolism is suggested in the snail neurons. The presence of the cAMP-dependent calcium channels seems to correlate with the existence of the definite type of 5-HT receptors in the cell membrane. A new approach to the investigation of isolated neurons is suggested: their functional identification.

[Parathyroid hormone stimulation of nerve cell calcium conduction]. / Stimuliatsiia paratireoidnym gormonom kal'tsievoi provodimosti nervnykh kletok.

Parathyroid hormone (PTH) has been studied for its effect on the voltage-sensitive calcium channels in voltage-clamp experiments on intracellularly perfused snail neurons. A two-stage action of the hormone on the calcium current (Ica) was shown. An initial stage was a short-term one and consisted in an increase of ICa by 7-10%. The second stage developed slowly for 60-70 min, ICa increased twice. The exogenous cAMP and cGMP did not produce such an effect as PTH did. It is suggested that the phosphoinositide pathway mediates the PTH effect.

[Action of forskolin on the calcium current in the membrane of nerve cells in mollusks]. / Deistvie forskolina na kal'tsievyi tok v membrane nervnykh kletok molliuska.

The action of forskolin, adenylate cyclase activator, on the calcium inward current was studied on intracellularly perfused nonidentified snail neurons. Extracellular application of 5-20 mumol/l of forskolin was shown to cause about 20% increase of the calcium current amplitude and this confirms the previous suggestion that the stimulation of the cellular synthesis of cAMP leads to enhancement of the calcium current through the cell membrane.