Inhibition of the pontine Kolliker‐Fuse nucleus reduces respiratory central chemoreflex activation in conscious rats

The Kölliker–Fuse nucleus (KF) within the dorsolateral pons is an essential part of the respiratory network that contributes to respiratory pattern formation and adaptation of breathing to afferent information. Studies in anesthetized animals or in vitro suggest that KF neurons might have a key role in the regulation of upper airway resistance and breathing by influencing respiratory rate and breathing amplitude. However, the contribution of these neurons to cardiorespiratory control in conscious rats is unclear. Male Wistar rats (280–300 g) with bilateral stainless steel cannulas implanted into the KF were used. In conscious rats, bilateral microinjection of the GABA‐A agonist muscimol (100 pmol/50 nl) into the KF decreased resting ventilation (1087 ± 182 ml/kg/min, vs. saline: 1501 ± 273 ml/kg/min) and the increase in ventilation produced by hypercapnia (10% CO2) (3010 ± 126 ml/kg/min, vs. salina: 3784 ± 303 ml/kg/min). Muscimol into the KF did not affect the changes in mean arterial pressure and heart rate produced by hypercapnia. The results suggest that KF neurons activate facilitatory mechanisms important to the control of ventilation in resting or hypercapnic conditions in conscious rats. Financial support: FAPESP (06/60174‐9 to TSM and 10/15692‐7 to RSD)