Biomedical subjects

Clemens Boucsein

Publications and source records attributed to Clemens Boucsein.

3 recordsLinked to original sources

PubMed2005

Controlling synaptic input patterns in vitro by dynamic photo stimulation.

Recent experimental and theoretical work indicates that both the intensity and the temporal structure of synaptic activity strongly modulate the integrative properties of single neurons in the intact brain. However, studying these effects experimentally is complicated by the fact that, in experimental systems, network activity is either absent, as in the acute slice preparation, or difficult to monitor and to control, as in in vivo recordings. Here, we present a new implementation of neurotransmitter uncaging in acute brain slices that uses functional projections to generate tightly controlled, spatio-temporally structured synaptic input patterns in individual neurons. For that, a set of presynaptic neurons is activated in a precisely timed sequence through focal photolytic release of caged glutamate with the help of a fast laser scanning system. Integration of synaptic inputs can be studied in postsynaptic neurons that are not directly stimulated with the laser, but receive input from the targeted neurons through intact axonal projections. Our new approach of dynamic photo stimulation employs functional synapses, accounts for their spatial distribution on the dendrites, and thus allows study of the integrative properties of single neurons with physiologically realistic input. Data obtained with our new technique suggest that, not only the neuronal spike generator, but also synaptic transmission and dendritic integration in neocortical pyramidal cells, can be highly reliable.

Action Potentials↗

PubMed2003

Purinergic receptors on microglial cells: functional expression in acute brain slices and modulation of microglial activation in vitro.

Microglial cells are the pathologic sensors in the brain. ATP released from damaged cells is a candidate for signalling neural injury to microglia. Moreover, ATP is an extracellular messenger for propagating astrocyte activity in the form of Ca2+ waves. To test for the functional expression of purinoreceptors in microglial cells we employed the patch-clamp technique in acute slices of adult mouse brain. ATP triggered a nonselective cationic and a K+ current. Pharmacological screening with purinergic ligands indicated the presence of P2Y1 and P2Y2/4 receptors linked to the activation of a K+ current and P2X receptors, including P2X7, linked to the activation of a nonselective cationic current. These findings suggest that microglial cells in situ express different purinergic receptors with distinct sensitivity and functional coupling. To test for the involvement of purinoreceptors in microglial activation, we stimulated cultured microglial cells with lipopolysaccharide and measured the release of tumour necrosis factor alpha, interleukin-6, interleukin-12 and macrophage inflammatory protein 1alpha, induction of K+ outward currents and nitric oxide release. All these parameters were reduced in the presence of purinergic ligands, indicating that purinergic receptor activation attenuated indicators of microglial activation.

Adenosine Triphosphate↗

PubMed2001

Astrocyte Ca2+ waves trigger responses in microglial cells in brain slices.

Pathologic impacts in the brain lead to a widespread activation of microglial cells far beyond the site of injury. Here, we demonstrate that glial Ca2+ waves can trigger responses in microglial cells. We elicited Ca2+ waves in corpus callosum glial cells by electrical stimulation or local adenosine triphosphate (ATP) ejection in acute brain slices. Macroglial cells, but not microglia, were bulk-loaded with Ca2+-sensitive dyes. Using a transgenic animal in which astrocytes were labeled by the enhanced green fluorescence protein (EGFP) allowed us to identify the reacting cell populations: the wave activated a Ca2+ response in both astrocytes and non-astrocytic glial cells and spread over hundreds of micrometers even into the adjacent cortical and ventricular cell layers. Regenerative ATP release and subsequent activation of metabotropic purinergic receptors caused the propagation of the glial Ca2+ wave: the wave was blocked by the purinergic receptor antagonist Reactive Blue 2 and was not affected by the gap junction blocker octanol, but enhanced in Ca2+ free saline. To test whether microglial cells respond to the wave, microglial cells were labeled with a dye-coupled lectin and membrane currents were recorded with the patch-clamp technique. When the wave passed by, a current with the characteristics of a purinergic response was activated. Thus, Ca2+ waves in situ are not restricted to astrocytic cells, but broadly activate different glial cell types.

Adenosine Triphosphate↗