Social housing effects of Intermittent Access of Methamphetamine Self-administration and social behavior
Authors: Gonzalez Ivette L. , Chauhdri Ammar F. , Nessen Reily J. , Lee Kristin , Becker Jill B. 
Published: February 2025

Social support is a potentially protective factor against substance use disorders (SUDs). Previous studies in animal models for SUDs have shown that when females are pair housed, they have lower motivation for cocaine and methamphetamine (METH), than females who are single housed. In males, however, social housing has not had the same beneficial effect. This study investigates effects of social housing on METH self-administration in females or males when both cagemates are self-administering METH. The study also investigated how the quality of those relationships changed after METH self-administration. The results showed that singly housed females self-administered more METH than socially housed females, while males in both social housing conditions self-administered METH at the same rate. The social behavior data showed that females given saline spend more time apart, however the females given METH spend more time together, suggesting that their social behavior may play a role in the attenuation of METH self-administration. Males’ social behavior remained unchanged after METH. Males METH self-administration was affected by whether they were the dominant partner, while females’ self-administration was not affected by dominance. The results of this study showed that social housing provides some protective benefits to females, not males, for METH self-administration. Further, the type of relationship between cage mates affects males’ self-administration and may explain why social housing with a same sex mate is not beneficial for males.

STRUCTURED ABSTRACT

Background

Social support is a potentially protective factor against substance use disorders (SUDs). Previous studies in rats have shown that when females are pair housed, they have lower motivation for drugs such as cocaine and methamphetamine (METH), than females who are single housed. In males, however, socially housed and individual housed males both have the same motivation for drugs such as cocaine.

Purpose

The aim of this study was to investigate if social housing would attenuate METH self-administration in females or males when both cage mates are self-administering METH. The study also investigated how the quality of those relationships changed after METH self-administration, if dominance played a role in the rate of self-administration, and the extent to which the quality of the relationships was related to METH self-administration.

Methods

Male and female rats were individually housed or housed in same sex pairs from around day 42, then animals underwent self-administration of METH (0.3 mg/kg/inf) on an intermittent access (IntA) schedule of reinforcement. Both animals in a pair self-administered METH. Social behavior was evaluated prior to and throughout the period when animals were self-administering METH.

Results

The results showed that in females, single housed females self-administered more METH than socially housed females, while males in both social housing conditions self-administered METH at the same rate. More singly housed females on day one of the IntA have high rates of self-administration, compared to socially housed females, those differences were attenuated after the first session, but singly housed females still self-administering METH to a greater extent than socially housed females overall. The social behavior data showed that females given saline spend more time apart while the females given METH spend more time together. This suggested that social behavior may contribute to the attenuation of self-administration. Males’ social behavior largely remained unchanged after METH and males continued to exhibit dominance behaviors. Furthermore, males’ METH self-administration was affected by dominance, with dominant males exhibiting greater responding for METH than non-dominant males.

Conclusions

Social housing provides some protective benefits to females, not males, for METH self-administration. Further, the type of relationship between cage mates affects males’ self-administration and may explain why social housing with a same sex mate is not beneficial for males.

HIGHLIGHTS

Pair housing in female rats results in less methamphetamine self-administration compared with individually housed females.

Pair housing in male rats did not attenuate methamphetamine self-administration compared with individual housing.

Females self-administering methamphetamine spent more time together.

Males’ self-administration of methamphetamine was affected by dominance status.