Leomi, R. | Search bioRxiv

bioRxiv2026

Adrenal remodeling encodes stress axis memory to shape fentanyl seeking

The hypothalamic-pituitary-adrenal (HPA) axis is implicated in substance use disorders, yet the features of this circuit that contribute to addiction vulnerability remain unclear. Here, we show that fentanyl engages with different components of the HPA axis, and this engagement varies across timescales. Within minutes, fentanyl activated corticotropin-releasing hormone neurons in the paraventricular nucleus of the hypothalamus (PVNCRH) and transiently increased adrenocorticotropic hormone (ACTH) levels. Hours to days later, fentanyl suppressed PVN activity, reduced adrenal size, and impaired corticosterone release. Conversely, ACTH-induced adrenal hypertrophy, increased corticosterone, suppressed fentanyl-evoked PVNCRH activity, and elevated fentanyl-seeking behavior. These findings identify adrenal remodeling as a physiological record of stress history that shapes neuroendocrine and behavioral responses to fentanyl, mechanistically linking stress and addiction while revealing treatment targets for opioid dependence.

neuroscience↗

bioRxiv2026

Modelling prodromal Parkinson's disease- gastrointestinal pathology and early motor deficits in mice after transient rotenone exposure

Early gastrointestinal (GI) dysfunction is a hallmark feature of Parkinson's disease (PD), yet models capturing prodromal gut and brain pathology in PD remain limited. Motivated by the increased PD risk associated with pesticide exposure, we monitored motor behavior, brain pathology, and GI structure and function over 9 months following 5 daily doses of rotenone in mice. Transient rotenone exposure induced significant nigrostriatal pathology, including {approx}48% loss of dopaminergic neurons and increased -synuclein aggregation in the substantia nigra, without significant changes in gross motor function. Notably, we identified pronounced GI dysfunction including reduced colonic transit velocity, altered motility dynamics, and delayed whole-gut transit. These functional changes were accompanied by enteric dopaminergic neurodegeneration, increased colonic -synuclein accumulation, increased colonic crypt depth, goblet cell hyperplasia with elevated mucin content per goblet cell. The findings are consistent with prodromal PD, suggesting the utility of this model for investigating early disease mechanisms and intervention strategies.

neuroscience↗