Inhibitory transmission in the bed nucleus of the stria terminalis in male and female mice following morphine withdrawal

Abstract

The United States is experiencing an opioid crisis imposing enormous fiscal and societal costs and driving the staggering overdose death rate. While prescription opioid analgesics are essential for treating acute pain, cessation of use in individuals with a physical dependence induces an aversive withdrawal syndrome that promotes continued drug use to alleviate/avoid these symptoms. Additionally, repeated bouts of withdrawal often lead to an increased propensity for relapse. Understanding the neurobiology underlying withdrawal is essential for providing novel treatment options to alleviate physiological and affective components accompanying the cessation of opiate use.Here, we administered morphine and precipitated withdrawal with naloxone to investigate behavioral and cellular responses in C57BL/6J male and female mice. Following 3 days of administration, both male and female mice demonstrated sensitized withdrawal symptoms. Since the bed nucleus of the stria terminalis (BNST) plays a role in mediating withdrawal-associated behaviors, we examined plastic changes in inhibitory synaptic transmission within this structure 24 hours following the final precipitated withdrawal. In male mice, morphine withdrawal increased spontaneous GABAergic signaling compared with controls. In contrast, morphine withdrawal decreased spontaneous GABAergic signaling in female mice. Intriguingly, these opposing GABAergic effects were contingent upon activity-dependent dynamics within the ex vivo slice. Our findings suggest that male and female mice exhibit some divergent cellular responses in the BNST following morphine withdrawal, and alterations in BNST inhibitory signaling may contribute to the expression of behaviors following opioid withdrawal.

Divergent behavioral responses in protracted opioid withdrawal in male and female C57BL/6J mice

“…Injections were delivered subcutaneously. All animals were observed for withdrawal behavior, and all morphine animals exhibited classical withdrawal signs (e.g., escape jumps, paw tremors, and teeth chattering) as we have previously reported in male and female C57BL/6J mice (Luster et al, ). Following the third day of the paradigm, animals were left undisturbed in the animal facility with the exception of routine cage changes for 6 weeks before testing.…”

“…To model opioid dependence in C57BL/6J mice, we used a 3‐day paradigm of exacerbated withdrawal (Figure ). We recently demonstrated that this paradigm enhances the development of withdrawal syndrome across the 3 days in both male and female mice and alters inhibitory transmission in the BNST (Luster et al, ). Interestingly, however, we found that both the manifestation of somatic withdrawal responses and BNST inhibitory transmission were sexually dimorphic (Luster et al, ).…”

“…We recently demonstrated that this paradigm enhances the development of withdrawal syndrome across the 3 days in both male and female mice and alters inhibitory transmission in the BNST (Luster et al, ). Interestingly, however, we found that both the manifestation of somatic withdrawal responses and BNST inhibitory transmission were sexually dimorphic (Luster et al, ). While this paradigm was developed as an acute dependence model (McElligott et al, ; Schulteis et al, , ), we hypothesized that there may be lasting changes in animal behavior in protracted abstinence.…”

“…All animals had food and water ad libitum for the duration of the study. Animals were treated for 3 days with the following paradigm, as described previously (Luster et al, ). Briefly, saline‐naloxone (SN) animals were injected with (0.9%) sterile saline (0.1 ml/10g) and 2 hr later with 1 mg/kg naloxone (in sterile saline 0.1 ml/10g).…”

“…Our laboratory has adapted a three‐day morphine dependence paradigm (Luster et al, ), which was used in this study to determine the effects of repeated bouts of morphine withdrawal. As observed in clinical settings and other established animal models, this model produces robust sensitization of physical withdrawal symptoms from morphine across the three‐day period (Azolosa, Stitzer, & Greenwald, ; Azorlosa & Stitzer, ; Schulteis, Heyser, & Koob, ; Schulteis, Yackey, Risbrough, & Koob, ) and acute anxiety‐like behavior in morphine‐treated animals (McElligott et al, ).…”