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M Kolaj

Publications and source records attributed to M Kolaj.

12 recordsLinked to original sources
PubMed1998

Vasopressin-induced currents in rat neonatal spinal lateral horn neurons are G-protein mediated and involve two conductances.

Arginine vasopressin (AVP) receptors are expressed early in the developing spinal cord. To characterize AVP-induced conductances in lower thoracic sympathetic preganglionic (SPN) and other lateral horn neurons, we used patch-clamp recording techniques in neonatal (11-21 days) rat spinal cord slices. Most (90%) of 273 neurons, including all 68 SPNs, responded to AVP with membrane depolarization and/or a V1 receptor-mediated, dose-dependent (0.01-1.0 microM) and tetrodotoxin (TTX)-resistant inward current. A role for G-proteins was indicated by persistence of this inward current after intracellular dialysis with GTP-gamma-S or GMP-PNP, its marked reduction with GDP-beta-S, and significant reduction, but not abolition, after preincubation with pertussis toxin or in the presence of N-ethylmaleimide. Analysis of individual current-voltage (I-V) relationships in 57 cells indicated the presence of two different membrane conductances. In 21 cells, net AVP-induced currents reversed around -103 mV, reflecting reduction in one or more barium-sensitive potassium conductances; in 12 cells, net AVP-induced current reversed around -40 mV and was not significantly sensitive to several potassium channel blockers including barium, tetraethylammonium chloride (TEA), 4-aminopyridine (4AP), cesium, or glibenclamide, suggesting increase in a nonselective cationic conductance that was separate from Ih; in 24 cells where I-V lines shifted in parallel, AVP-induced inward currents were significantly greater and probably involved both conductances. These data indicate that SPNs and a majority of unidentified neonatal lateral horn neurons possess functional G-protein-coupled V1-type vasopressin receptors. The wide distribution of AVP receptors in neonatal spinal lateral column cells suggests a role that may extend beyond involvement in regulation of autonomic nervous system function.

Animals↗
PubMed1997

Two conductances mediate thyrotropin-releasing-hormone-induced depolarization of neonatal rat spinal preganglionic and lateral horn neurons.

Thyrotropin-releasing hormone (TRH) has been recognized as a neuromodulator in several CNS regions, including the thoracolumbar spinal cord where an influence on cardiovascular autonomic function has been proposed. To identify the cellular mechanisms involved in the latter, whole cell patch-clamp recordings were obtained from 52 thoracolumbar lateral horn cells, including 17 sympathetic preganglionic neurons (SPNs), in spinal cord slices from neonatal rat (11-21 days). Under current clamp, bath applications of TRH (1-20 microM) induced a slowly rising and prolonged membrane depolarization in eight of nine cells tested. Under voltage clamp (holding potential -65 mV), 33 of 37 tested cells displayed a TRH-induced, tetrodotoxin-resistant inward current that was associated with either a reduction or an increase in membrane ion conductances. Current-voltage (I-V) relationships in 28 cells suggested two conductances. In 9 cells the current reversed at about -107 mV; in 10 cells the I-V lines remained parallel, whereas in 9 cells the current reversed at around -40 mV. In three of three cells, addition of 2 mM barium was associated with an inward current, and the TRH-induced inward current was also suppressed, suggesting the presence of a resting barium- and TRH-sensitive potassium conductance. A residual barium-insensitive conductance was seen to reverse near -40 mV. Intracellular dialysis with guanosine 5'-o-(3-thiotriphosphate) significantly enhanced the duration of the TRH effect, indicating that G protein activation participates in the TRH response. These observations not only reveal a direct, G-protein-mediated depolarizing action of TRH on neonatal rat SPNs and lateral horn cells but also imply that two separate conductances may be involved in the TRH responses in some neurons.

Animals↗
PubMed1996

mu-Opioid receptor-mediated reduction of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid-activated current in dorsal horn neurons.

Whole-cell voltage-clamp recording was used to examine the effects of mu-opioid receptor agonists DAGO (Tyr-D-Ala-Gly-MePhe-Gly-ol-enkephalin) and PL017 (Tyr-Pro-N-MePhe-D-Pro-NH2) on alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-induced currents in acutely isolated spinal dorsal horn (DH) neurons from laminae I-IV of young rats. We found that the peak and steady-state amplitude of the AMPA-induced current were depressed by mu-opioid agonists (1 nM-5 microM) in a dose-dependent manner in about 80% of the tested cells. When experiments were performed using whole-cell perforated patch technique, similar depression of AMPA current was produced by mu-opioids. The mu-opioid receptor selective antagonist CTAP (100 nM) prevented or reduced the depressant effects of DAGO and PL017. Intracellular dialysis with guanosine 5'-O-(2-thiodiphosphate) (GDP-beta-S, 0.2 mM) significantly diminished the PL017-induced depression of AMPA responses. In addition, when the cells were dialyzed with guanosine 5'-O-(3-thiotriphosphate) (GTP-gamma-S, 0.1 mM) the amplitude and duration of the PL017-induced depression was significantly enhanced. Besides depressing the AMPA responses of DH cells, co-application of PL017 and kainic acid (KA) decreased the magnitude of the KA-induced current in 60% of the tested cells. These results indicate that in acutely isolated rat DH neurons, the activation of mu-opioid receptor inhibits AMPA-activated current through activation of a G-protein. This action may contribute to the regulation of the strength of the primary afferent neurotransmission including nociception.

Amino Acid Sequence↗
PubMed1996

Quantifying rigidity with a new computerized elbow device.

A new computerized method is described for measuring parkinsonian rigidity with an elbow device. We present data from 127 subjects (103 controls and 24 parkinsonian patients) to show the clinical utility of the method. The instrumental quantification of rigidity correlates highly with clinical ratings of parkinsonian rigidity. The test-retest repeatability was excellent. In parkinsonian patients versus normal controls, significantly higher values of measured rigidity were observed. Moreover, activation procedure significantly increases rigidity only in parkinsonian patients. Activated rigidity in control subjects is lower than basal values. The procedure was sensitive to increased rigidity in parkinsonian patients during 3 days' drug holiday. Contrary to previous reports, levodopa therapy reduced both basal and activated rigidity in parkinsonian patients. This method is relatively simple and takes only 15 min to complete.

Adult↗
PubMed1995

The opioid peptide dynorphin modulates AMPA and kainate responses in acutely isolated neurons from the dorsal horn.

In freshly isolated spinal dorsal horn (DH) neurons (laminae I-IV) of the young rat, the effects of dynorphin A1-17, U-50,488H and U-69,593 on inward currents induced by alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) and kainate (KA) were studied under whole-cell voltage-clamp conditions. When the cells were clamped to a holding potential of -60 mV, co-application of dynorphin A1-17 (10(-6) M) and AMPA (2 x 10(-5) M) reversibly decreased the peak amplitude of the initial transient component of the AMPA-induced current in 72% of the examined cells. In addition, dynorphin (10 microM) in perforated patch-recordings consistently produced a decrease in the steady-state component of the AMPA response. The depressant effect was concentration-dependent (IC50 = 86 nM) and reversible. The dynorphin A1-17-induced depression of the AMPA response was associated with slowing of the response kinetics, including both a 10-90% rise-time and time constant of decay. The AMPA-induced currents were modulated by dynorphin not only during the co-administration but also after the removal of the peptide. Dynorphin increased the initial peak AMPA current in 42% of the examined cells. Similar as with dynorphin A1-17, the peak amplitude of the AMPA-induced current was reversibly suppressed in the presence of 1 microM U-50,488H and U-69,593 in 75% and 86% of the examined cells, respectively. Naloxone and the kappa 1-selective antagonist norbinaltorphimine (nor-BNI) blocked the initial depressant but not late excitatory effects of dynorphin A1-17 and U-50,488H. This antagonistic effect of naloxone and norbinaltorphimine suggests that the depressant effect of dynorphin A1-17 on the AMPA-activated conductance is a true opioid, probably kappa 1-opioid receptor-mediated event. In contrast, the dynorphin-induced late potentiation of AMPA/KA responses appears to be a non-opioid effect since it was not inhibited by nor-BNI, CTAP and naltrindole, the selective kappa-, mu- and delta-opioid receptor blocking agents, respectively. Pretreatment of DH neurons with pertussis toxin blocked the depressant action of dynorphin A1-17, indicating that a Gi- or Go-type G protein was required for this effect on AMPA-activated currents. Intracellular dialysis with a highly specific peptide inhibitor (peptide 6-22) of the cAMP-activated protein kinase (PKA), and with Rp-cAMPS, prevented the depressant effect of dynorphin A1-17. In addition, staurosporine, a nonselective kinase inhibitor, blocked the dynorphin depression of the AMPA response.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1995

Alpha-subunit of calcium/calmodulin-dependent protein kinase II enhances gamma-aminobutyric acid and inhibitory synaptic responses of rat neurons in vitro.

1. Here we report that in acutely isolated rat spinal dorsal horn neurons, the gamma-aminobutyric acid-A (GABAA) receptor can be regulated by calcium/calmodulin-dependent protein kinase II (CaM-KII). Intracellularly applied, the alpha-subunit of CaM-KII enhanced GABAA-receptor-activated current recorded with the use of the whole cell patch-clamp technique. This effect was associated with reduced desensitization of GABA responses. 2. GABA-induced currents are also potentiated by calyculin A, an inhibitor of protein phosphatases 1 and 2A. 3. Conventional intracellular recordings were made from hippocampal CA1 neurons in slices to determine the effect of intracellular application of CaM-KII on inhibitory synaptic potentials evoked by electrical stimulation of the stratum oriens/alveus. The inhibitory synaptic potential was enhanced by CaM-KII; this mechanism may contribute to long-term enhancement of inhibitory synaptic transmission and may also play a role in other forms of plasticity in the mammalian brain.

Animals↗
PubMed1994

Alpha subunit of calcium/calmodulin-dependent protein kinase enhances excitatory amino acid and synaptic responses of rat spinal dorsal horn neurons.

1. Here we report that in acutely isolated rat spinal dorsal horn (DH) neurons, the alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA)/kainate and N-methyl-D-aspartate (NMDA) receptors can be regulated by endogenous and exogenous calcium/calmodulin-dependent protein kinase II (CaM-KII). Intracellularly applied, the alpha-subunit of CaM-KII enhanced AMPA/kainate and NMDA currents recorded with the use of the whole cell patch-clamp technique. 2. Microcystin, a nonselective phosphatases inhibitor, also enhances AMPA and NMDA responses. 3. Conventional intracellular recordings were made from substantia gelatinosa neurons in spinal cord slices to determine the effect of intracellular application of CaM-KII on excitatory synaptic potentials evoked by electrical stimulation of primary afferent fibers. Excitatory synaptic transmission was enhanced by CaM-KII, which is consistent with the importance of phosphorylation of the postsynaptic AMPA/kainate and NMDA receptor-ion complexes in the short- and long-term changes in synaptic transmission.

Animals↗
PubMed1991

Analysis of calcium activated chloride current fluctuations in Xenopus laevis oocytes.

Fluctuations of calcium activated chloride currents were investigated in oocytes of Xenopus laevis. The method of noise analysis and the model of chloride channels activation by calcium ions were used to estimate the chloride channels lifetime and the average frequency of current fluctuations, which depends on changes of cytoplasmic calcium concentration. This current fluctuations can be evoked by activation of cholinergic receptors or inhibition by Na3VO4 of plasma membrane Ca(2+)-ATPase. The average opening lifetime of chloride channels was approximately 100 ms. The frequency of fluctuations increased with the increasing extracellular calcium concentrations and external ACh concentrations. Caffeine in 2 mmol/l concentration changed the current fluctuations into oscillations with a period of about 18-20s. Ten mmol/l caffeine fully inhibited the oscillation activity.

Action Potentials↗
PubMed1982

Primary afferent depolarization and changes in extracellular potassium concentration induced by L-glutamate and L-proline in the isolated spinal cord of the frog.

To test the hypothesis that L-proline acts as an antagonist on glutamate receptors [17, 18], the interaction between L-glutamate and L-proline was studied in the isolated spinal cord of the frog. Glutamate at concentrations of 10(-6) -5 x 10(-3) mol/l depolarized the primary afferent fibres and increased extracellular potassium concentration, [K+]e, by 0.3-4 mmol/l. Repeated applications lead to inactivation of the response. L-Proline at 5 x 10(-3) -10(-2) mol/l, also depolarized the primary afferents and increased [K+]e by 0.5-2 mmol/l, but there was only a slight decrease of the effects after repeated application. The effects were additive when the amino acids were applied simultaneously. The effect of L-proline was still present when it was applied during inactivation of the glutamate receptors. This suggests that L-glutamate and L-proline act on different receptors.

Afferent Pathways↗