Transient, reversible apnoea following ablation of the pre-Bötzinger complex in rats

1. In some anaesthetized preparations, eupnoea is eliminated following a blockade or destruction of neurons in a rostral medullary pre-Botzinger complex. 2. Neurons in this region might underlie the neurogenesis of eupnoea, or be the source of an input which is necessary for eupnoea to be expressed. If the latter, any apnoea following ablation of the pre-Botzinger complex might be reversed by an augmentation in 'tonic input.' Contrariwise, this apnoea should be permanent if the neuronal activities of the pre- Botzinger complex are an exclusive generator of the eupnoeic rhythm. 3. Decerebrate, vagotomized, paralysed and ventilated adult rats were studied. Efferent activity of the phrenic nerve was recorded as an index of ventilatory activity. 4. Blockade or destruction of neuronal activities of the pre-Botzinger complex by unilateral and/or bilateral injections of muscimol or kainic acid eliminated eupnoea only transiently. Eupnoea returned following activation of the peripheral chemoreceptors and spontaneously over time. 5. Results do not support the concept that neuronal activities of the pre-Botzinger complex play an exclusive role in the neurogenesis of eupnoea in vivo. Rather, these neuronal activities appear to provide a tonic input to the ponto-medullary circuit which generates eupnoea and/or appear to be one component of this circuit.