Dynamics and Infradian Rhythmics of Thermal/Pain Sensitivity of the <Emphasis Type="Italic">Helix</Emphasis> Mollusc under the Action of Electromagnetic Fields

We measured characteristics of thermal/pain (th/p) sensitivity of Helix albescens (threshold and latency of the avoidance behavioral reaction) under conditions of the hot-plate test. As was found, weakening (shielding) of the background electromagnetic field, as well as the action of low-intensity radiations of extremalfrequency ranges, induced two-phase changes of these characteristics within a 21-day-long observation period with different manifestations and durations of the phases. Initial increase in the nociceptive sensitivity (hyperalgesia) was followed by an analgesic effect with subsequent return of the examined indices to the initial level. Low-intensity electromagnetic influences also induced modifications of the infradian rhythmics of th/p sensitivity of the molluscs; this was manifested in changes of the spectra and phase shifts of the identified rhythms and trends toward modulation of the amplitudes of these rhythmic components.     

ATP-induced calcium signalling in acinar cells of the submandibular salivary gland

To study changes in the cytoplasmic Ca²⁺ concentration ([Ca²⁺]_i) and the total amount of calcium in cells, we used, respectively, the fluorescent dye fura 2/AM and the metallochrome dye arsenazo III. The total amount of calcium in acinar cells after their incubation in calcium-free ATP-containing extracellular solution decreased. The action of ATP induced a dose-dependent increase in the [Ca²⁺]_i; the EC₅₀ was, on average, 130 ± ± 36 μM. Calcium transients induced by ATP demonstrated no desensitization. Against the background of a blocker of ionotropic P2X receptors, pyridoxal phosphate-6-azophenyl-2′,4′-disulfonic acid, we observed a decrease in the ATP-induced calcium transients by 72%. In addition, these transients were reduced by 65% in the calcium-free milieu, while after thapsigargin-induced exhaustion of the endoplasmic reticulum store they disappeared. This is indicative of the involvement of metabotropic P2Y receptors in the formation of the above calcium transients. Therefore, P2X and P2Y receptors participate in ATP-induced calcium signalling in acinar cells of the submandibular salivary gland; activation of these channels results in a rise in the [Ca²⁺]_i. The P2X receptors to a higher extent contribute to the formation of calcium signals; the P2Y-determined increase in the [Ca²⁺]_i is smaller (equal to about 35%). Therefore, the functionally active ligand-operated ionotropic P2Y receptors and metabotropic G protein-related P2Y receptors do exist in acinar cells of the submandibular salivary gland and play an important role in the control of functioning of this gland. Neirofiziologiya/Neurophysiology, Vol. 37, Nos. 5/6, pp. 395–402, September–December, 2005.     

Effects of Gabapentin on Calcium Transients in Neurons of the Rat Dorsal Root Ganglia

In our experiments on rat dorsal root ganglia (DRG) neurons, we studied the effects of an antiepileptic agent, gabapentin, on calcium transients evoked by depolarization of the membrane using the fluorescence calciumsensitive dye Fura-2/AM. Application of gabapentin to neurons with large-diameter somata practically did not change the characteristics of calcium transients. In mid-sized neurons, the amplitude of transients decreased, on average, by 27% with respect to the control, while in small-sized neurons the transients changed insignificantly (on average, less than by 7%). The mid-sized neurons were additionally subjected to the capsaicin test, which allowed us to differentiate primary nociceptive neurons of this group where TRPV1-type channels are expressed. In capsaicin-sensitive neurons, application of gabapentin led to a decrease in the amplitude of calcium transients, on average, by 37%, while such a decrease was only 16% in capsaicininsensitive neurons. Based on our own data and findings of other researchers on the ability of gabapentin to demonstrate affine binding with the accessory α₂δ subunit of voltage-dependent calcium channels and also on the peculiarities of expression of these channels in somatosensory neurons of the corresponding types, we discuss the probable pattern of expression of subunits of the α₂δ-1 subtype in DRG cells of different sizes. We demonstrated that the effects of gabapentin on calcium transients in nociceptive and hypothetically nonnociceptive mid-sized DRG neurons are selective (the effects in neurons involved in the sensation of acute pain are probably more intense). Neirofiziologiya/Neurophysiology, Vol. 40, No. 4, pp. 281–287, July–August, 2008.     

Synaptic connections of fibers of the rubrospinal tract in the cat spinal cord

The ultrastructure of the lateral part of laminae VI and VII of the spinal gray matter (the location of most of the terminal branches of the rubrospinal tract) was investigated in cats under normal conditions and at various times after destruction of the red nucleus. The neuron population of this region is formed by cells fairly homogeneous in size (25–40µ). The structure of the dendritic profiles is simple and they carry only infrequent and small membranous appendages. Most synapses are axo-dendritic. The axon terminals are divided into three groups depending on the size and shape of the synaptic vesicles and the presence of post-synaptic specialization. A few glomerular axon terminals contacting with various structures are found. Small axon terminals located chiefly on dendrites and their appendages show degenerative changes 1–8 days after destruction of the red nucleus. As a rule the degenerating terminals contain round synaptic vesicles. The glomerular terminals do not degenerate.A. A. Bogomol'ets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 6, No. 6, pp. 610–618, November–December, 1974.     

Effects of Gabapentin on Different Neuronal Populations in the Dorsal-Root Ganglia of Rats with Streptozotocin-Induced <Emphasis Type="Italic">Diabetes Mellitus</Emphasis>

We studied the effect of gabapentin (an agent similar, in its molecular structure, to gamma-aminobutyric acid, GABA) on depolarization-evoked calcium transients in small, mid-sized, and large (diameter of the soma up to 25, 25 to 35, and 35 μm or more, respectively) neurons of the dorsal-root ganglia (DRGs) of rats with experimental streptozotocin-induced diabetes mellitus. These transients were measured using a calcium-sensitive fluorescent dye, Fura 2/AM. The amplitude of calcium transients in rats with diabetes was somewhat higher than that in healthy animals (in large and mid DRG neurons by nearly 12% and in small cells by about 8%, on average). The development of diabetes led to a dramatic increase in the total duration of such transients. In large, mid, and small DRG neurons, the values of this parameter in animals with diabetes were, respectively, about 260, 430, and 250% as compared with the norm. The duration of transients at the level of 50% amplitude (Т _0.5) in diabetes changed to a significantly smaller extent. Applications of gabapentin (25 μM) led to a decrease in the amplitude of calcium transients, their full duration, and Т _0.5. The effects of gabapentin were the strongest in large DRG neurons where the amplitude of calcium transients dropped by nearly 36%, while the total duration demonstrated a more than threefold decrease. Upon the action of gabapentin, the parameter Т _0.5 changed moderately (in all groups of DRG neurons, the decrease varied from 8 to 12%). Gabapentin-induced decreases in the amplitude of calcium transients differed in various subgroups of DRG neurons. Among neurons with mid-sized somata, the decrease in this parameter in capsaicin-positive cells was 16.3%, while that in capsaicin-negative cells reached 36.7%. The obtained data are indicative of the ability of gabapentin to normalize, to a certain extent, the parameters of diabetes-modified calcium transients in DRG neurons. This ability is more clearly pronounced in large neurons (we hypothesize that a part of such cells in animals with diabetes are, probably, abnormally involved in transmission of nociceptive influences) and also in a part of mid-sized DRG neurons participating in the formation of acute pain sensation.     

Myeloperoxidase/nitrite-mediated lipid peroxidation of low-density lipoprotein as modulated by flavonoids

In the presence of a H(2)O(2)-generating system, myeloperoxidase (MPO) caused conjugated diene formation in low-density lipoprotein (LDL), indicating lipid peroxidation which was dependent on nitrite but not on chloride. The oxidation of LDL was inhibited by micromolar concentrations of flavonoids such as (-)-epicatechin, quercetin, rutin, taxifolin and luteolin, presumably via scavenging of the MPO-derived NO(2) radical. The flavonoids served as substrates of MPO leading to products with distinct absorbance spectra. The MPO-catalyzed oxidation of flavonoids was accelerated in the presence of nitrite.     

Volume-regulated chloride conductance in the LNCaP human prostate cancer cell line

Patch-clamp recordings were used to study ioncurrents induced by cell swelling caused by hypotonicity in humanprostate cancer epithelial cells, LNCaP. The reversal potential of the swelling-evoked current suggested that Cl was the primarycharge carrier (termed I_Cl,swell). Theselectivity sequence of the underlying volume-regulated anion channels(VRACs) for different anions wasBrI > Cl > F > methanesulfonate glutamate, with relativepermeability numbers of 1.26, 1.20, 1.0, 0.77, 0.49, and 0.036, respectively. The current-voltage patterns of the whole cell currentsas well as single-channel currents showed moderate outwardrectification. Unitary VRAC conductance was determined at 9.6 ± 1.8 pS. Conventional Cl channel blockers5-nitro-2-(3-phenylpropylamino)benzoic acid (100 µM) and DIDS (100 µM) inhibited whole cell I_Cl,swell in a voltage-dependent manner, with the block decreasing from 39.6 ± 9.7% and 71.0 ± 11.0% at +50 mV to 26.2 ± 7.2% and14.5 ± 6.6% at 100 mV, respectively. Verapamil (50 µM), astandard Ca²⁺ antagonist and P-glycoprotein functioninhibitor, depressed the current by a maximum of 15%. Protein tyrosinekinase inhibitors downregulated I_Cl,swell(genistein with an IC₅₀ of 2.6 µM and lavendustin A by60 ± 14% at 1 µM). The protein tyrosine phosphatase inhibitorsodium orthovanadate (500 µM) stimulatedI_Cl,swell by 54 ± 11%. We conclude thatVRACs in human prostate cancer epithelial cells are modulated viaprotein tyrosine phosphorylation.

     

Changes in the ionic mechanisms of the electrical excitability of rat sensory neuronal somatic membrane during ontogenesis. Distribution of ionic channels carrying inward currents

The distribution of different types of ionic channels carrying inward currents was investigated in the somatic membranes of spinal ganglion neurons in rats belonging to three different age groups: at 5–9 days, 45 days, and 3 months. A decrease was found in the number of neuronal membranes operating all four types of inward current channels simultaneously: "fast" (tetrodotoxin-sensitive), "slow" (tetrodotoxin-resistant) sodium currents and low- and high-threshold calcium currents. There were 14.5% of such neurons in the first age group, 5% in the second, and 1% on the third. It was found that this change was related to the disappearance of "slow" (tetrodotoxin-resistant) sodium and high-threshold calcium channels from the membrane. The number of neuronal somatic membranes with only two types of inward current channels ("fast" sodium and high-threshold calcium channels) increased proportionately.A. A. Bogomolets Institute of Technology, Academy of Sciences of the Ukrainian SSR, Kiev Translated from Neirofiziologiya, Vol. 18, No. 6, pp. 813–820, November–December, 1986.     

Membrane currents induced by inflow of sodium ions into mollusk giant neurons

Membrane currents induced by inflow of sodium ions were investigated in giant neurons of the molluskHelix pomatia during tetanic stimulation or prolonged membrane depolarization under voltage clamp conditions. The membrane current thus produced consists of two components, a fast component with a reversal potential close to the potassium equilibrium potential, and a slow component only slightly dependent on membrane potential in the region from −50 to −90 mV. Addition of strophanthin K to the external solution, or replacement of sodium in the external solution by lithium or calcium abolished the slow component of the membrane current and reduced the fast component. It is concluded that the slow component appears as the result of activation of the sodium pump under electrogenic conditions, where-as the fast component arises as the result of an increase in potassium permeability, possibly coupled with intensive activity of this pump.