Baroreflex response with iron deficiency: sympathetic and parasympathetic components

We have previously demonstrated that the baroreflex is altered by iron deficiency (EB2005, EB2004). The objective of this study was to determine which component of the autonomic nervous system is altered by iron deficiency (ID). CD rats (Harlan) were put on an ID or control (C) diet for 4 weeks; ID was confirmed by microhematocrit (p<0.05). One femoral artery and both femoral veins were catheterized; rats recovered for 1 d. Phenylephrine and nitroprusside were infused intravenously to raise and lower arterial pressure, respectively, across a broad range; arterial pressure was constantly monitored to determine the baroreflex (HR to MAP relationship). Atropine (4 mg/kg ip) was then given to block postganglionic parasympathetic neurotransmission, and the baroreflex protocol was repeated after 10 min. Further experiments are continuing at time of abstract writing. However, a preliminary data analysis (n=8) has been completed. Atropine injection resulted in an increase in HR across all MAP for both ID and C rats (p<0.0001), indicating efficacy of parasympathetic blockade in both groups. HR was greater in ID than C across all MAP (p<0.0001), confirming baroreflex alterations with ID. A much smaller ID vs. C difference was found after atropine (p=0.06, Fisher's PLSD p<0.0001), suggesting that both sympathetic and parasympathetic components contribute to the baroreflex alterations with ID. Pulse pressure analysis across MAP is also consistent with less parasympathetic and more sympathetic baroreflex activity with ID (p<0.0001). If confirmed by final analysis, we conclude that ID alters both the parasympathetic and sympathetic components of the baroreflex. Supported by the Wyoming NIH INBRE Grant (LC4090).