Mechanisms of the facilitation of neurotransmitter secretion in strontium solutions.

Experiments on frog neuromuscular synapses using extracellular microelectrode recording of endplate currents (EPC) and nerve ending (NE) responses were performed to study the mechanisms of facilitation of quantum secretion of acetylcholine on replacement of extracellular Ca ions with Sr ions. Solutions with a Ca ion concentration of 0.5 mM (calcium solutions) or a Sr ion concentration of 1 mM (strontium solutions) were used; the basal levels of neurotransmitter secretion (in conditions of low-frequency stimulation) were essentially identical. In calcium solutions, the drop in EPC facilitation on paired-pulse stimulation as the interimpulse interval was increased from 5 to 500 msec was described by the sum of three exponential components - the early, the first, and the second. In strontium solutions, facilitation was decreased as compared with the level in calcium solutions predominantly because of decreases in the early and first components. At the same time, EPC facilitation in conditions of rhythmic stimulation (10 or 50 impulses/sec) in strontium solution was significantly increased as compared with the level in calcium solutions. In strontium solutions in conditions of high-frequency stimulation at 50 impulses/sec, there was also a marked decrease in the amplitude of the third phase of the NE response, reflecting NE potassium currents. These data lead to the conclusion that the facilitation sites underlying the first and early components had lower affinities for Sr ions than for Ca ions. Increases in facilitation in strontium solutions in conditions of high-frequency rhythmic activity resulted from two mechanisms: more marked widening of the NE action potential and an increase in the divalent cation influx current due to weak activation of the Ca2+-dependent potassium current in the presence of Sr ions, as well as the slow dynamics of the removal of Sr ions from the NE axoplasm as compared with that in the presence of Ca ions.

[Mechanisms of neurotransmitter release facilitation in strontium solutions].

Mechanisms of neurotransmitter release facilitation were studied using electrophysiological recording of end-plate currents (EPC) and nerve ending (NE) responses after substitution of extracellular Ca ions with Sr ions at the frog neuromuscular junction. The solutions with 0.5 mM concentration of Ca ions (calcium solution) or 1 mM concentration of Sr ions (strontium solution) were used where baseline neurotransmitter release (at low-frequency stimulation) is equal. Decay of paired-pulse facilitation of EPC at calcium solutions with increase of interpulse interval from 5 to 500 ms was well described by three-exponential function consisting of early, first and second components. Facilitation at strontium solutions was significantly diminished due mainly to decrease of early and first components. At the same time, EPC facilitation with rhythmic stimulation (10 or 50 imp/s) at strontium solutions was significantly increased. Also more pronounced decrease of NE response 3rd phase, reflecting potassium currents was detected under rhythmic stimulation of 50 imp/s at strontium solutions comparing to calcium solutions. It was concluded that facilitation sites underlying first and early components had lower affinity to Sr ions than to Ca ions. The enhancement of frequency facilitation at strontium solutions is mediated by two mechanisms: more pronounced broadening of NE action potential and increase of bivalent cation influx due to feebly marked activation of Ca(2+)-dependent potassium current by Sr ions, and slower dynamics of Sr(2+) removal from NE axoplasm comparing to Ca(2+).

[An efficacy study of the treatment of patients with chronic pyelonephritis and urolithiasis using sulfate-bicarbonate calcium-magnesium mineral water]. / Issledovanie éffektivnosti lecheniia sul'fatno-gidrokarbonatnoi kal'tsievo-magnievoi mineral'noi vodoi bol'nykh khronicheskim pielonefritom i mochekamennoi bolezn'iu.

Clinical effects of spa treatment on renal function in middle-aged and elderly male and female patients with chronic pyelonephritis and urolithiasis was studied. Combined sanatorium treatment included a course intake of low-mineral sulphate-hydrocarbonate calcium-magnesium mineral water Kazanskaia. Diuresis, especially daytime, was activated in all the patients. Maximum diuresis was observed in cool seasons in the elderly patients. To the end of the treatment proteinuria, oxaluria and uraturia diminished. A course of drinking mineral water Kazanskaia proved effective and is recommended for patients with chronic pyelonephritis and urolithiasis.

[Regulation of the postsynaptic alpha-1-adrenoreceptors of the smooth muscle of the nictitating membrane in the cat]. / Reguliatsiia postsinapticheskikh al'fa-1-adrenoretseptorov gladkoi myshtsy migatel'noi pereponki koshki.

Radioassay binding of the smooth muscle of the nictitating membrane of cat has revealed the specific binding sites of [3H]prazosin corresponding to alpha-1 adrenoceptors. There was a significant increase in the number of alpha-1 adrenoceptors without any changes in their affinity. Incubation of the culture of the preliminary sympathectomized smooth muscle with noradrenaline decreased the number of alpha-1 adrenoceptors also without altering the affinity of binding. So, it is concluded that sympathetic nervous system regulated the number of postsynaptic alpha-1 adrenoceptors by means of neurotransmitter (noradrenaline).

[The alpha-adrenergic sensitivity of smooth muscle following sympathectomy]. / Al'fa-adrenergicheskaia chuvstvitel'nost' gladkoi myshtsy posle desimpatizatsii.

The effect of sympathetic nerve stimulation on postsynaptic alpha-adrenoceptors of cat's smooth muscle nictitating membrane was studied. L-noradrenaline, adrenaline, phenylephrine and clonidine caused a concentration-dependent contraction. In denervated tissue, the concentration-response curve for clonidine mainly shifted to the left in comparison with the control; in contrast to the innervated smooth muscle, there were no reliable differences between the constant dissociation Ka and KB for alpha 1- and alpha 2-selective and nonselective adrenomimetics and adrenoblockaders. The data obtained suggest alteration of pharmacological characteristics of smooth muscle alpha-adrenoceptors after interruption of the sympathetic nerve.