Breathing requires a complex pattern of neuronal activity resulting in alternating contraction and relaxation of respiratory muscles. An important part of the respiratory network is located in the pre-Bötzinger complex (preBötC), which can be functionally isolated in a slice preparation. In this "breathing" slice the respiratory neurons continue to generate respiratory burst activity. While activity of respiratory neurons has been analyzed intensively, the discovery of specific functions of glial cells, e.g. astrocytes, in the respiratory network is still at its beginnings. In the preBötC the majority of astrocytes show a high potassium conductance, this indicates that they importantly contribute to potassium buffering. Furthermore astrocytes express neurotransmitter transporters. Here we analyzed the behavior of astrocytes in the preBötC during ongoing respiratory activity.

We performed whole cell recordings from identified eGFP-labeled astrocytes in the preBötC using TgN(hGFAP-eGFP) mice. Approximately 10% of recorded astrocytes showed some degree of inward current (Iinsp,A) in phase with the preBötC field potential bursts.

After blockade of synaptic inhibition by strychnine (10 mM) and bicuculline (10 mM) the amplitude of Iinsp,A increased. Furthermore, the inward current did not reverse within a membrane potential range from -80 to +20 mV, indicating that Iinsp,A is not mediated by ionotropic transmitter receptors. Additional application of the glutamate uptake inhibitor L-threo-beta-hydroxyaspartate acid (THA) reduced the amplitude of Iinsp,A.

These data suggest that glutamate transporter mediated glutamate uptake occurs during ongoing respiratory activity. However, we can not exclude that a major part of the measured current is due to extracellular accumulation of potassium.