In vivo studies on response properties to differently oriented gratings in neurons and astrocytes in ferret primary visual cortex identified three important features [1]. First, neurons and astrocytes respond to oriented grating selectively with a comparable width in tuning. Second, locations of pinwheels and orientation domains organzied in maps do coincide in neurons and astrocytes. Third, orientation tuning is differently affected in neurons and astrocytes during the application of a glutamate transporter blocker (TBOA): Blocking glutamate transport broadened the orientation tuning in neurons and fully suppressed orientation selectivity in astrocytes. However, the underlying mechanisms generating a broader orientation tuning in neurons and suppressing the tuned response in astrocytes during application of TBOA are unknown. In this context we first investigate how the influence of prolonged TBOA-mediated high glutamate concentrations at the synaptic cleft [2] is expressed in the opening rate of post-synaptic AMPA and NMDA receptors and finally in the resulting combined EPSC. The obtained transfer functions are further used to describe the currents mediated by excitatory synapses in a 2d network model [3] of the primary visual cortex. The network is composed of excitatory and inhibitory populations with Gaussian distributed random recurrent connections and receives weakly tuned afferent input. First simulations show that broadening in neuronal tuning curves during application of TBOA can be explained by changes in the time course of glutamate clearance.This suggests that astrocytic glutamate transporters can influence, the neural response properties to features like orientation by changing the glutamate clearance.
[1] Schummers, J., Hongbo, S., and Sur, M., Science 320,1638 (2008) [2] Diamond, D., J. Neurosci., 25(11),2906 (2005) [3] Stimberg, M., et al., Cerebr. Cort. 19,2166 (2009)

Society for Neuroscience Abstract, 2011.