Abstract II Goettingen 2001

Network Activity In Vitro Induced by Dynamic Photostimulation

M.P. Nawrot, B. Kampa, A. Aertsen, S. Rotter, D. Heck

Neurobiologie und Biophysik, Institut füur Biologie III
Albert-Ludwigs-Universität, Freiburg
www.brainworks.uni-freiburg.de

Important insights into properties of cortical neurons have been obtained from intracellular recordings in in vitro slice preparations. The main advantages of the acute slice preparation are the visibility and accessibility of neurons, and the stability of recordings.
     Recent results from in vivo experiments demonstrate that the electrophysiological properties of single neurons (e.g. membrane resistance and time constant) as well as the dynamic properties of the cortical network are clearly affected by ongoing ativity, constantly present in the intact brain [1,2,3]. These findings, supported by theoretical studies of network dynamics [4], make it necessary to re-evaluate results from in vitro slice experiments, where spontaneous background activity is sparse or absent.

Membrane potential before (A) and during (B) random dynamic photostimultaion.

Here, we present a new experimental approach which enables us to evoke an in vivo-like background activity in the reduced network of the cortical slice. To achieve this we use a photolabile precursor of the excitatory transmitter glutamate (caged glutamate), which is activated by means of a UV-laser beam, focused onto the slice. By sequentially stimulating randomly chosen sites within the plane of the slice, we induced network activity causing in vivo-like membrane potential fluctuations and increased spike rates in neurons recorded in whole-cell patch configuration (c.f. Figure) or extracellularly.
     Our present setup allows the stimulation of up to 1000 different targets per second within an area of 10mm x 10mm, with a precision of 10mum. This enables us to apply dynamic stimulation patterns and to study cortical network dynamics under controlled conditions.

Funded by the Deutsche Forschungsgemeinschaft (DFG, SFB\,505).

[1] Arieli et al. (1996) Science 273: 1868--1871
[2] Pare et al. (1998) J. Neurophysiol. 79: 1450--1460
[3] Heck et al. (2000) Soc. Neurosci. Abstr. 26: 609.6
[4] Diesmann et al. (1999) Nature 402: 529--533