Conditioned stress prevents cue-primed cocaine reinstatement only in stress-responsive rats

Abstract

Neurobiological mechanisms underlying comorbid posttraumatic stress disorder (PTSD) and cocaine use disorder (CUD) are unknown. We aimed to develop an animal model of PTSD + CUD to examine the neurobiology underlying cocaine-seeking in the presence of PTSD comorbidity. Rats were exposed to cat urine once for 10-minutes and tested for anxiety-like behaviors one week later. Subsequently, rats underwent long-access (LgA) cocaine self-administration and extinction training. Rats were re-exposed to the trauma context and then immediately tested for cue-primed reinstatement of cocaine-seeking. Plasma and brains were collected afterwards for corticosterone assays and real-time qPCR analysis. Urine-exposed (UE; n = 23) and controls not exposed to urine (Ctrl; n = 11) did not differ in elevated plus maze behavior, but UE rats displayed significantly reduced habituation of the acoustic startle response (ASR) relative to Ctrl rats. A median split of ASR habituation scores was used to classify stress-responsive rats. UE rats (n = 10) self-administered more cocaine on Day 1 of LgA than control rats (Ctrl + Coc; n = 8). Re-exposure to the trauma context prevented cocaine reinstatement only in stress-responsive rats. Ctrl + Coc rats had lower plasma corticosterone concentrations than Ctrls, and decreased gene expression of corticotropin releasing hormone (CRH) and Glcci1 in the hippocampus. Rats that self-administered cocaine displayed greater CRH expression in the amygdala that was independent of urine exposure. While we did not find that cat urine exposure induced a PTSD-like phenotype in our rats, the present study underscores the need to separate stressed rats into cohorts based on anxiety-like behavior in order to study individual vulnerability to PTSD + CUD.

Keywords:

• Addiction
• corticosterone
• CRH
• FKBP5
• Glcci1
• PTSD

Disclosure statement

The content of the information does not necessarily reflect the position or the policy of the Government, and no official endorsement should be inferred. The authors declare no conflicts of interest.

Funding information

This work was supported by Institute for Translational Neuroscience Subcontract 8738sc awarded to LK. Award Number: W81XWH-12-2-0048. The U.S. Army Medical Research Acquisition Activity, 820 Chandler Street, Fort Detrick, MD 21702-5014 is the awarding and administering acquisition office.