Cooling of ventral medullary intermediate areas and respiration in the cat

We sought to address the contribution of the ventral medullary intermediate (I) areas to respiratory regulation in the close loop condition. The experiments were done on anesthetized, spontaneously breathing cats. The transient and steady-state neural respiratory output responses to longlasting cooling of the I areas and to vagotomy and hyperoxia performed during the cooling period were investigated. Cooling of the I areas resulted in an initial transient inhibitory response followed by respiratory output increase in the steady-state, provided other respiratory inputs were maintained intact. This investigation calls into question the crucial role of the I areas in regulation of respiration in the close loop condition.