In vitro and in vivo study of butyrylfentanyl and 4-fluorobutyrylfentanyl in female and male mice: Role of the CRF1 receptor in cardiorespiratory impairment

Sabrine Bilel; Joaquim Azevedo Neto; Micaela Tirri; Giorgia Corli; Marta Bassi; Anna Fantinati; Giovanni Serpelloni; Davide Malfacini; Claudio Trapella; Girolamo Calo'; Matteo Marti

doi:10.1111/bph.17333

In vitro and in vivo study of butyrylfentanyl and 4-fluorobutyrylfentanyl in female and male mice: Role of the CRF₁ receptor in cardiorespiratory impairment

Br J Pharmacol. 2024 Oct 4. doi: 10.1111/bph.17333. Online ahead of print.

Authors

Affiliations

¹ Section of Legal Medicine and LTTA Centre, Department of Translational Medicine, University of Ferrara, Ferrara, Italy.
² Section of Pharmacology, Department of Neuroscience and Rehabilitation, University of Ferrara, Ferrara, Italy.
³ Department of Environmental and Prevention Sciences, University of Ferrara, Ferrara, Italy.
⁴ Neuroscience Clinical Center & TMS Unit, Verona, Italy.
⁵ Department of Psychiatry, College of Medicine, Drug Policy Institute, University of Florida, Gainesville, Florida, USA.
⁶ Department of Pharmaceutical and Pharmacological Sciences, University of Padua, Padua, Italy.
⁷ Center of Gender Medicine, University of Ferrara, Ferrara, Italy.
⁸ Collaborative Center of the National Early Warning System, Department for Anti-Drug Policies, Presidency of the Council of Ministers, Rome, Italy.

PMID: 39367619
DOI: 10.1111/bph.17333

Abstract

Background and purpose: Fentanyl analogues have been implicated in many cases of intoxication and death with overdose worldwide. The aim of this study is to investigate the pharmaco-toxicology of two fentanyl analogues: butyrylfentanyl (BUF) and 4-fluorobutyrylfentanyl (4F-BUF).

Experimental approach: In vitro, we measured agonist opioid receptor efficacy, potency, and selectivity and ability to promote interaction of the μ receptor with G protein and β-arrestin 2. In vivo, we evaluated thermal antinociception, stimulated motor activity and cardiorespiratory changes in female and male CD-1 mice injected with BUF or 4F-BUF (0.1-6 mg·kg^-1). Opioid receptor specificity was investigated using naloxone (6 mg·kg^-1). We investigated the possible role of stress in increasing cardiorespiratory toxicity using the corticotropin-releasing factor 1 (CRF₁) antagonist antalarmin (10 mg·kg^-1).

Key results: Agonists displayed the following rank of potency at μ receptors: fentanyl > 4F-BUF > BUF. Fentanyl and BUF behaved as partial agonists for the β-arrestin 2 pathway, whereas 4F-BUF did not promote β-arrestin 2 recruitment. In vivo, we revealed sex differences in motor and cardiorespiratory impairments but not antinociception induced by BUF and 4F-BUF. Antalarmin alone was effective in blocking respiratory impairment induced by BUF in both sexes but not 4F-BUF. The combination of naloxone and antalarmin significantly enhanced naloxone reversal of the cardiorespiratory impairments induced by BUF and 4F-BUF in mice.

Conclusion and implications: In this study, we have uncovered a novel mechanism by which synthetic opioids induce respiratory depression, shedding new light on the role of CRF₁ receptors in cardiorespiratory impairments by μ agonists.

Keywords: 4‐fluorobutyrylfentanyl; CRF1; antalarmin; butyrylfentanyl; fentanyl; mu opioid receptor; naloxone; novel psychoactive substances; respiratory depression; β‐arrestin 2.

Abstract

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