Abstract Body: In the context of the opioid crisis, diagnoses of opioid use disorder (OUD) during pregnancy—particularly driven by fentanyl misuse—have increased nearly fourfold. OUD is associated with increased rates of type 2 diabetes, hyperglycemia, and dyslipidemia. However, the long-term metabolic consequences of in utero fentanyl exposure (IUFE) remain poorly understood. Our laboratory developed a rat model of IUFE by allowing female rats to self-administer fentanyl. We showed that adult offspring with IUFE displayed reductions in plasma insulin, increased fasting blood glucose, and greater sympathetic tone.
Increased sympathetic outflow from the paraventricular nucleus of the hypothalamus (PVN) inhibits insulin secretion from pancreatic β-cells, while mu-opioid receptor antagonism prevents sympathetic activation and glucose intolerance. Thus, this study investigated the neuronal activation in PVN and other brain areas known to control glucose homeostasis and sympathetic outflow in adult offspring with IUFE. Brains from adult IUFE and vehicle-exposed male rats were fixed (4% PFA) to analyze Fos immunoreactivity (RPCA-c-FOS, 1:4000, 72 hours, 4^oC) as a marker of neuronal activation. IUFE increased the number of Fos+cells in anterior PVN (34±3 vs. 10±3, p<0.05), posterior PVN (47±4 vs. 24±2, p<0.05), and preoptic area (158±5 vs. 97±3, p<0.05). Conversely, high plasma glucose in IUFE rats could inhibit glucose-sensing neurons in the lateral hypothalamic area (11±1 vs. 16±1, p<0.05), whereas decreased insulin levels in IUFE-exposed males may activate neurons in dorsal raphe nucleus (36±2 vs. 21±1, p<0.05) and area postrema (16±1 vs. 5±1, p<0.05). In additional studies, brains from IUFE and vehicle-exposed male adult offspring were fixed with 4% PFA, cleared, and stained using electrophoretic-enabled device SmartBatch+ (LifeCanvas Technologies) to determine the mapping of noradrenergic neurons. IUFE increased TH signal in locus coeruleus (LC, 258 vs.175 cells/mm^3), the primary site for brain norepinephrine synthesis and release, as well as in brainstem (15.8 vs. 9.5 cells/mm^3), and hypothalamus (66.6 vs. 17.5 cells/mm^3). Taken together, our data show that prenatal opioid exposure increases neuronal activation in both anterior and posterior PVN in male rats, which could increase sympathetic activation to the pancreas to impair insulin secretion. Future studies will investigate whether this activation is mediated by increased noradrenergic input from LC.