The cholinergic stimulation of the hippocampus induced the activation of the sympathetic nervous system.

We previously demonstrated that the direct microinjection of cholinesterase inhibitor (neostigmine) into the hippocampus in rats activated the hypothalamo-pituitary -adrenal axis and increased the level of norepinephrine in the plasma. In the current study we tried to measure the effects of neostigmine injection into the hippocampus using the non-invasive measure of heart rate variability (HRV). After the hippocampal injection of neostigmine (50 nM and 125 nM) or saline as a control in rats, HRV measurement was performed for 30 min. After the injection of neostigmine into the hippocampus, LF/HF, the index of the sympathetic nervous system, significantly increased. The results of the current study indicated that stimulation of the hippocampal cholinergic system induced the activation of the sympathetic nervous system.