Electrolytic Lesions of the Dorsal Rostral Pons Prevent Adrenocorticotropin Increases after Hemorrhage*

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Abstract
To determine if a discrete area of the dorsal rostral pons in the region of the locus coeruleus (LC) is essential for the reflex response of ACTH to hemorrhage, chloralose-anesthetized cats with bilateral electrolytic (11 cats) or sham (3 cats) lesions were challenged with a 15 ml/kg .cntdot. 3 min hemorrhage. Sequential arterial blood samples taken at -6, -3, 3, 6, 9, 15 and 21 min from hemorrhage were analyzed for ACTH content. Cats were grouped according to whether plasma ACTH increased in response to hemorrhage. Bilateral lesions in 7 cats with an area in common, which lay within the LC complex, blocked the reflex increase in plasma ACTH in response to hemorrhage which was seen in 3 sham-lesioned cats, in 3 cats with lesions that did not infringe in this region bilaterally, and in 1 cat with lesions that infringed only on the medial-ventral aspect of the LC-subceruleus. Apparently, hemodynamic information responsible for the reflex response of ACTH to hemorrhage of this magnitude passes through a discrete region of the dorsal rostral pons.