# Extended abstinence from morphine alters sperm smRNA expression and prevents transmission of intergenerational phenotypes

## TL;DR

Prolonged abstinence from morphine in male rats prevents the transmission of addiction-related traits to their offspring.

## Contribution

Extended abstinence erases morphine-induced sperm smRNA changes and blocks intergenerational addiction phenotypes.

## Key findings

- 90-day abstinence from morphine eliminated offspring addiction-related behavioral changes.
- Two smRNAs were differentially expressed in sperm from morphine-exposed versus saline-treated rats.
- Abstinent morphine and saline sperm showed no smRNA differences, suggesting abstinence reverses germline effects.

## Abstract

Paternal exposure to drugs of abuse can impact addiction-related behaviours in progeny via germline epigenome remodelling. Previously, we found that offspring of morphine-exposed male rats showed increased morphine-taking, diminished adolescent social play, and increased sensitivity to morphine-derived analgesia. Here, we first tested the impact of a 90-day paternal abstinence period following morphine self-administration on the transmission of the aforementioned phenotypes. The previously observed changes in morphine-related behaviours were no longer present in offspring of morphine-abstinent sires. We next compared small RNA (smRNA) content in sperm collected from four sire intravenous self-administration groups: morphine, saline, abstinent morphine, and abstinent saline. Two smRNAs (rno-miR-150-5p and an snoRNA annotated to Snora42/Noc3l) were differentially expressed specifically between morphine- and saline-treated sperm. No differential expression between abstinent morphine and saline sperm was observed. These data begin to delineate the temporal limits of heritable germline modifications associated with morphine exposure, in addition to identifying F0 germline factors coinciding with the manifestation of F1 multigenerational phenotypes. Furthermore, these data suggest that paternal abstinence at conception can prevent inheritance of germline factors that may alter offspring susceptibility to addiction-related endophenotypes.