Rhythmic slice preparations used to study neuronal control of breathing usually contain the preBötzinger complex (PBC) and caudal medullary respiratory centers. Recent studies suggest that respiratory rhythm generation also involves more rostral aspects such as the parafacial region (PFR). Also a potential role of the pontine Kölliker-Fuse (KF) is assumed. In 700 mm rat brainstem slices that contain the PBC, PFR and KF we imaged activity dependent intracellular Ca2+ changes to correlate neuronal activity patterns in the PBC with electrical mass activity. The novel slice preparation is characterized by a low frequency PBC mass activity of 2-6 burst/min (8 mM [K+ ]o) compared to 6-12 bursts/min in the "classic" PBC slice. Blocking inhibitory synapses with strychnine/bicuculline causes an initial, substantial augmentation of the PBC rhythm that stabilizes at frequencies of 5-10 bursts/min. This response pattern reflects the situation after pontine ablation in en-bloc preparations. Since changes in PBC burst frequency are accompanied by increased amplitudes of the integrated electrical mass activity, recruitment of additional neurons may be involved. Our imaging approach shows that after strychnine/bicuculline treatment expiratory neurons become arhythmic and additional inspiratory neurons are recruited.

Supported by the DFG (CMPB)