Neuronal Correlates of Hyperalgesia and Somatic Signs of Heroin Withdrawal in Male and Female Mice

Abstract

Opioid withdrawal involves the manifestation of motivational and somatic symptoms. However, the brain structures that are involved in the expression of different opioid withdrawal signs remain unclear. We induced opioid dependence by repeatedly injecting escalating heroin doses in male and female C57BL/6J mice. We assessed hyperalgesia during spontaneous heroin withdrawal and somatic signs of withdrawal that was precipitated by the preferential μ-opioid receptor antagonist naloxone. Heroin-treated mice exhibited significantly higher hyperalgesia and somatic signs than saline-treated mice. Following behavioral assessment, we measured regional changes in brain activity by automated the counting of c-Fos expression (a marker of cellular activity). Using Principal Component Analysis, we determined the association between behavior (hyperalgesia and somatic signs of withdrawal) and c-Fos expression in different brain regions. Hyperalgesia was associated with c-Fos expression in the lateral hypothalamus, central nucleus of the amygdala, ventral tegmental area, parabrachial nucleus, dorsal raphe (DR), and locus coeruleus (LC). Somatic withdrawal was associated with c-Fos expression in the paraventricular nucleus of the thalamus, lateral habenula, DR, and LC. Thus, hyperalgesia and somatic withdrawal signs were each associated with c-Fos expression in unique sets of brain areas. The expression of c-Fos in the DR and LC was associated with both hyperalgesia and somatic withdrawal. Understanding common neurobiological mechanisms of acute and protracted opioid withdrawal may help identify new targets for treating this salient aspect of opioid use disorder.

Escalation of intravenous fentanyl self-administration and assessment of withdrawal behavior in male and female mice

“…Additionally, increased anxiety-like behavior was found one week into abstinence from fentanyl. Withdrawal from opioids such as heroin and morphine has been shown to result in hyperalgesia in humans (74,75) and similarly in rats and mice (16,18). Recent studies have shown oxycodone withdrawal to result in increase of mechanical pain sensitivity in rats (10) and somatic withdrawal signs in mice (20)(21)(22).…”

“…In those rodent models, there is a clear pattern of increasing drug intake over time, accompanied by intensified drug-seeking behavior. Withdrawal symptoms are also a hallmark of drug dependence and upon withdrawal from opioids, both rats and mice exhibit allodynia (15–18), along with anxiety-like behaviors (19), and a spectrum of other withdrawal-related physical symptoms (20–23). These observations highlight the translational validity and value of such models in deepening our comprehension of the behavioral and physiological changes associated with OUD.…”

Extended access to fentanyl vapor self-administration leads to addiction-like behaviors in mice: Blood chemokine/cytokine levels as potential biomarkers

“…Heightened mechanical sensitivity was associated with higher opioid preference in mice with a history of stress but not in controls [ 67 ]. Naloxone-precipitated withdrawal in the LgA group loaded on a third independent factor, suggesting different brain circuitries compared with hyperalgesia in LgA mice [ 68 ]. These findings highlight qualitative differences between behavioral phenotypes of mice with different levels of drug access.…”

Embryonic exposure to fentanyl induces behavioral changes and neurotoxicity in zebrafish larvae

“…The c-fos is an excellent biomarker for identifying synaptic activation ( Torres-Hernandez et al, 2016 ), and the relative expression of c-fos was more than twice as high in zebrafish exposed to high fentanyl as it was in the control group. Experiments on mice revealed a correlation between c-fos expression in a specific subset of brain areas and opioid hyperalgesia and physical withdrawal symptoms ( Alvarez-Bagnarol et al, 2022 ). In addition, the expression level of c-fos mRNA in the zebrafish brain increased considerably following nicotine abstinence in the zebrafish nicotine withdrawal experiment ( Ponzoni et al, 2021 ).…”