Wyniki wyszukiwania

1

Modification of electrophysioogical properties of barrel cortex neurons induced by enriched environment - ex vivo study

100%

Garkun Y., Bekisz M., Zakrzewska R., Kossut M.

Acta Neurobiologiae Experimentalis

|

2011

|

tom 71

|

nr S

In laboratory animals, exposure to the enriched environment (EE) induces broad range of modifications in nerve cells at both molecular and anatomical levels. EE also improves animal’s cognitive performance in learning and memory tasks. Despite some progress in revealing the effects of EE on synaptic transmission in the hippocampus, scant and inconsistent data are available on the impact of EE on synaptic properties in the neocortex. The aim of the present study was to examine the influence of the EE exposure on neuronal properties in layer IV of the barrel cortex. Twenty five days old mice (bred under standard laboratory conditions) were put for two weeks to the enriched environment (i.e. to bigger cage with playing tools: tunnels, ladders, a running wheel, spatial maze box and with a set of objects of different shape, made from various fabrics). Control mice were housed in standard laboratory cages during the same period of time. Next, we prepared brain slices containing the barrel cortex and performed visually guided whole-cell recordings from excitatory layer IV neurons within barrels B-D. The results were compared between control and EE-exposed animals. We found that EE experience increased the spontaneous firing rate of excitatory layer IV cells. This phenomenon seems to be due to stronger excitatory synaptic input to these neurons, because both frequency and amplitude of spontaneous excitatory postsynaptic currents were bigger after EE exposure, while kinetic properties of spontaneous inhibitory postsynaptic currents as well as intrinsic excitability remained unchanged. Our results indicate that EE selectively enhances excitatory transmission within the cortical representation of whiskers. The research was supported by the Ministry of Science and Higher Education “PolPostDoc” grant PBZ/MNiSW/07/2006/09 to GY.

2

Identification of cells undergoing plastic changes in the barrel cortex after simple associative learning using transgenic fosGFP mice

88%

Garkun Y., Bekisz M., Radwanska A., Barth A., Kossut M.

Acta Neurobiologiae Experimentalis

|

2009

|

tom 69

|

nr 3

Learning is assumed to be connected with neuronal c-fos expression. In this study we investigate whether associative learning involving tactile stimulation of one row of whiskers induced changes in c-fos expression level in neurons within the cortical representation of the stimulated vibrissae. We use transgenic mice in which the expression of green fl uorescent protein (GFP) is controlled by c-fos promoter [Barth et al. (2004) J Neurosci]. This construct allows us to identify individual neurons undergoing plastic changes in acute (living) brain slices using standard fl uorescence imaging. In the trained mice prior to experiments a 3-day sensory stimulation (20 min/day) of row B of whiskers (conditioned stimulus) paired with an electrical shock (unconditioned stimulus) was performed. The second group comprised of untrained animals. Acute slices from the somatosensory cortex (cut orthogonally to the rows of barrels) were prepared after the end of training and investigated using upright fl uorescent microscope. Our preliminary data indicate high variability of fosGFP expression throughout cortical layers. Biggest amount of GFP-labeled cells are observed in layer 2/3 and much smaller in layers VI and V. Sensory training alter amount of fosGFP+ cells in layer 2/3 of barrel B as compared to other barrels with little or no effect in layers IV and V. Supported by the Ministry of Science and Education grant: N30308131/2682.

3

Modification of excitability of cortical neurons induced by associative learning-ex vitro experiments

88%

Bekisz M., Garkun Y., Hess G., Wrobel A., Kossut M.

Acta Neurobiologiae Experimentalis

|

2009

|

tom 69

|

nr 3

In adult mice, whiskers stimulation paired with an electrical shock to the tail induces expansion of the cortical representation of stimulated vibrissae and enhances inhibitory interactions within the “trained” barrels. In present experiments we investigated whether such simple associative learning paradigm induced also changes in the neuronal excitability. We prepared brain slices through the barrel cortex and performed whole-cell recordings from visually identifi ed layer IV neurons. Our results showed that excitatory cells located in layer IV of the cortical representation of the “trained” row B of vibrissae had higher frequency of spikes recorded at threshold potential, as compared to both neurons from “untrained” barrel D and to cells from control animals. Additionally, cells within the “trained” barrels displayed bigger gain in the input-output function and decrease in the activation of BK channels responsible for the fast afterhyperpolarisation, which suggests the source for their enhanced intrinsic excitability. The increased excitability of cells within the “trained” barrels may express their homeostatic plasticity which parallels enhanced inhibitory interactions found previously within layer IV of the cortical representation of the “trained” vibrissae. This may be the way to increase the cortical selectivity of response to sensory input from “trained” whiskers. Supported by the MNiSW grants: N30308131/2682, N40114631/3239, COST/127/2007 and PBZ/MNiSW/07/2006.

Ograniczanie wyników

3 Acta Neurobiologiae Experimentalis

3 Bekisz M.

3 Garkun Y.

3 Kossut M.

1 Barth A.

1 Hess G.

1 Radwanska A.

1 Wrobel A.

1 Zakrzewska R.

1 2011

2 2009

Modification of electrophysioogical properties of barrel cortex neurons induced by enriched environment - ex vivo study

Identification of cells undergoing plastic changes in the barrel cortex after simple associative learning using transgenic fosGFP mice

Modification of excitability of cortical neurons induced by associative learning-ex vitro experiments