SUN-015 Neural Activity Patterns Underlying the Glucocorticoid Withdrawal Syndrome

Abstract Disclosure: C.N. Snyder: None. L.L. Haddad: None. K.M. Liberman: None. S.E. Yang: None. J. Meng: None. J.L. Spencer-Segal: Corcept Therapeutics, Recordati Rare Diseases, Camurus AB, Crinetics Pharmaceuticals. Dependence on glucocorticoid excess can occur as a result of chronically elevated endogenous or exogenous glucocorticoid. A rapid decrease in circulating glucocorticoid can result in the glucocorticoid withdrawal syndrome (GWS). While the etiology of this syndrome remains unknown, one of the most prominent behavioral disturbances is generalized pain. The diffuse nature of these symptoms led us to hypothesize a central mechanism for GWS involving brain regions associated with pain sensitivity. To investigate this, we developed a mouse model of precipitated glucocorticoid withdrawal where male and female mice received 2x daily intraperitoneal injections of 5mg/kg dexamethasone (or vehicle) for 10 days followed by a single injection of 20mg/kg mifepristone (or vehicle). 90 minutes after mifepristone injection, mechanical pain sensitivity was tested using the von Frey apparatus. Mice were then perfused and brains collected for immunohistochemistry. To investigate how neural activity changes in response to mifepristone-precipitated glucocorticoid withdrawal, immunohistochemistry using 3,3’diaminobenzadine labeling for c-fos, a marker of neural activity, was performed on brain sections from mice treated with dexamethasone followed by vehicle and dexamethasone followed by mifepristone, and c-fos+ cell density was quantified throughout the brain. A 3-way ANOVA revealed that there was no effect of sex (F (1,29)=3.039, p=0.0919) on paw withdrawal thresholds in the von Frey, so the sexes were pooled and a 2-way ANOVA was used to examine the effect of dexamethasone treatment and GR antagonism. There was a main effect of dexamethasone treatment (F(1, 33)=8.607, p=0.0060) and GR antagonism (F(1, 33)=8.731, p=0.0057) on the paw withdrawal threshold. Post-hoc testing using Fisher’s Uncorrected LSD revealed that mifepristone-treated mice had a lower withdrawal threshold than dexamethasone-treated mice that received vehicle (p=0.0060) and a lower threshold than mice that received vehicle and mifepristone (p=0.0040). Thus, GR antagonism caused increased mechanical pain sensitivity specifically in mice previously treated with high doses of glucocorticoid. Unpaired t-tests showed that in dexamethasone-treated male mice, mifepristone decreased neural activity measured as cfos+ cell density in the motor cortex (t(7)=0.4.458, p=0.0029), somatosensory cortex (t(7)=2.578, p=0.0366), and basolateral amygdala (t(7)=3.888, p=0.0060). These results demonstrate specific patterns of neural activity associated with glucocorticoid withdrawal-induced mechanical pain sensitivity in mice. Future work will focus on the role of these brain regions in the behavioral phenotype. Understanding the mechanisms leading to the GWS will eventually allow us to better treat patients and relieve the burden of excess glucocorticoid treatment and its associated morbidity and mortality. Presentation: Sunday, July 13, 2025