Peptidergic Recruitment of Adrenal Chromaffin-Cell Ensembles During Stress Adaptation: Roles of PACAP, Vasopressin and Gap Junction Plasticity

Background: Adrenal chromaffin cells integrate cholinergic and peptidergic signaling to regulate catecholamine secretion during stress. Although pituitary adenylate cyclase-activating polypeptide (PACAP] sustains adrenal secretion during intense sympathetic activation, the systems-level mechanisms coordinating chromaffin-cell activity remain incompletely understood. Perspective: We suggest that chromaffin cells function as dynamically recruited chromaffin-cell ensembles rather than independent endocrine units. Within this framework, connexin-mediated gap junctions act as activity-dependent amplifiers that enable PACAP- and acetylcholine-dependent recruitment of progressively larger ensembles according to physiological demand. We further suggest that ensemble recruitability is continuously modified by physiological state and previous experience. Conclusions: Building upon recent evidence and our experimental observations, we propose that early-life adversity remodels hypothalamic autonomic circuits, altering subsequent PACAP-dependent recruitment of chromaffin-cell ensembles during adult stress. This unified framework integrates peptidergic signaling, gap junction plasticity, and developmental programming, generating experimentally testable hypotheses and providing a new systems-level view of sympathoadrenal regulation.