Tooth pulp stimulation potentiates the adrenocorticotropin response to hemorrhage in cats

Stimulation of the maxillary tooth pulp nerve (TP), a predominantly nociceptive afferent fiber system, was assessed for its effect on peripheral plasma ACTH in chloralose-urethane anesthetized cats. These results were compared to those after a transient 10 ml/kg hemorrhage (H), a submaximal neurogenic stressor for ACTH release, and to H plus TP in combination. TP alone for 3 min had no significant effect on ACTH. However, TP during H greatly potentiated the increase in plasma ACTH concentration compared to that seen after H alone. The TP potentiation of the H-induced rise in ACTH was not accompanied by altered cardiovascular responsiveness nor by differences in plasma norepinephrine or glucose relative to that seen after H alone. The data indicate that nociceptive and baroreceptor afferents share a common neural substrate for selective facilitation of ACTH release, but do not interact to potentiate several other physiological responses, such as sympathetic efferent activity. Furthermore, under the conditions of these experiments, selective nociceptor activation in the anesthetized cat is not an adequate stimulus for the release of ACTH.