Fig. 4.

Sites of cholinergic agonist injections in the brainstem. The symbols in the left and right side represent cardiac and blood pressure responses to cholinergic injection, respectively. Carbachol was injected in pons only and produced prolonged hypotension with no change of heart rate. ACh injection produced hypotension with variable change of heart rate in most of the experiments. Tachycardia was always found in the pons and the rostral medulla, while tachycardia, bradycardia, or no change were seen in the caudal medulla. See Fig. 1 for the symbols and abbreviations.