Effect of Reversible Inactivation of the Kolliker Fuse Nucleus on Basal Blood Pressure and Heart Rate in Anesthetized Rat

Introduction: Several supra spinal areas such as rostral ventrolateral medulla (RVLM) area are involved in basic cardiovascular regulation. The Kolliker— Fuse nucleus (KF) is located in pons and is heavily connected with RVLM. The cardiovascular effect of KF nucleus has been shown and it is suggested that KF is involved in sympathetic vasomotor tone and basic cardiovascular regulation. Therefore, in the present study, the effects of KF on basic cardiovascular values were evaluated. Methods: After induction of anesthesia, a polyethylene catheter (PE-50) filled with heparinized saline was inserted into the femoral artery of rats. Animals were then placed in a stereotaxic apparatus and KF nucleus was inactivated by microinjection of cobalt chloride (CoCl2). Blood pressure and heart rate (HR) were continuously recorded pre and post inactivation. Results: Our result showed that inactivation of KF slightly changed mean arterial blood pressure (MAP) (92.3 ± 2.45 mmHg vs. 90.86 ± 1.7 mmHg) and HR (343.8 ± 4.6 beats/min vs. 350.7 ± 8.32 beats /min). However, these effects were not significant in comparison to the control group. Discussion: We concluded that synapses in the KF nucleus have no effect on regulation of basal blood pressure and heart rate, because CoCl2 is a synaptic blocker.