Balazs Rozsa

Publications (2)9.93 Total impact

• Article: Distance-dependent scaling of calcium transients evoked by backpropagating spikes and synaptic activity in dendrites of hippocampal interneurons.

  Balazs Rozsa, Tibor Zelles, E Sylvester Vizi, Balazs Lendvai
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  ABSTRACT: Although interactions between backpropagating action potentials and synaptic stimulations have been extensively studied in pyramidal neurons, dendritic propagation and the summation of these signals in interneurons are not nearly as well known. In this study, two-photon imaging was used to explore the basic properties of dendritic calcium signaling in CA1 stratum radiatum interneurons. In contrast to hippocampal pyramidal neurons, the backpropagating action potential-evoked calcium transients in dendrites of interneurons underwent a distance-dependent increment. Although, in proximal dendrites, an increment could be attributed to a smaller dendrite diameter, distal dendrites did not show such dependence. Calcium responses in interneurons had a smaller amplitude, slower rise time, and decay than in pyramidal neurons. To explore the factors underlying the difference, we compared the calcium-binding capacity in interneurons and in pyramidal neurons. Our finding that endogenous calcium buffers had a higher level in interneurons may primarily explain the different kinetics and amplitudes of calcium transients. Synaptic stimulation-evoked calcium transients were also larger at distant dendritic locations. The spread of these signals was restricted to 12-13 microm long dendritic compartments. Supporting the reported lack of long-term potentiation in these interneurons, we found only sublinear or linear summations of calcium responses to coincident synaptic inputs and backpropagating spikes.
  Journal of Neuroscience 02/2004; 24(3):661-70. · 7.11 Impact Factor
• Article: A vinca alkaloid enhances morphological dynamics of dendritic spines of neocortical layer 2/3 pyramidal cells.

  Balazs Lendvai, Tibor Zelles, Balazs Rozsa, E Sylvester Vizi
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  ABSTRACT: We imaged neocortical layer 2/3 pyramidal cells in rat brain slices with two-photon laser scanning microscopy to investigate that spine motility can be influenced by the voltage-dependent Na(+) and Ca(2+) channel inhibitor, vinpocetine, which exhibited positive cognitive effects in human studies. Veratridine, which enhances sodium influx, was also tested on dendritic spine motility. Perfusion with vinpocetine, a derivative of vinca alkaloids, caused a substantial increase in the structural dynamics of dendritic spines measured by the changes in length or the number of new/retracted spines. In contrast, enhancement of sodium influx with veratridine failed to change spine motility. Our results indicate that the rapid changes in spine shape and size could occur, when calcium and sodium influx has been decreased by this vinca alkaloid. Spine motility induced by vinpocetine may be associated to microtubule alterations, an effect that was described for other vinca alkaloids. On the other hand, the potential of vinpocetine to enhance cognition in clinical studies suggests that the increased spine motility may be related to cognitive functions.
  Brain Research Bulletin 02/2003; 59(4):257-60. · 2.82 Impact Factor