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Sex differences in drug abuse behavior

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Venniro (2018)
When I was reading Experiment 1, I noticed that the authors only mentioned males for the methamphetamine experiments and mentioned both males and females for the heroin experiments which was interesting. It was positive that both sexes were being used in this experiment but not clear why only for the heroin experiment. I referred to the methods and there were 318 male rats and only 39 female rats used in this study, about 11%. Why wouldn’t the researchers use a ratio closer to 50/50 of male and female rats? I don’t know much about laboratory rat breeding but I would assume it’s not due to a shortage of females since most studies use only males. Why were all the females in the heroin group and none in the methamphetamine group? It says rats were randomly assigned to drug user and drug naive groups but it doesn’t say that they were randomly assigned to drug type groups. And if they were randomly assigned, it’s unlikely that all of the females were assigned to the heroin group. So their results show that sex does not have an effect on preference of social interaction or heroin but sex may have an effect on preference of social interaction or methamphetamine that has not been explored.
In experiment 3, the results show that the medium addiction group had higher resistance to punishment of social reward. I wonder where there was a bell curve here. It would make sense for the high addiction group to give up the social reward faster if there was punishment because their addiction is stronger so a social reward may not be that much more enticing than the drug to begin with. However, I’m not sure why the low addiction group would have low resistance to the social reward punishment as well.
An interesting next step for this research could be to see what kinds of stresses can undo the protection from incubation of craving brought on by abstinence. Humans after drug addiction treatment may turn to drugs again in order to deal with stressors so it would be interesting to see how strong this protection is against chronic mild stress, acute traumatic stress, etc.

de Guglielmo (2019)
I noticed this paper discussed rats being dependent on alcohol rather than saying they are addicted to alcohol. Any mentions of addiction in this paper used the term addiction-like. It reminds me of some of the papers we read previously that used phrases like “depressive-like phenotypes” or “anxiety-like behaviors” that used those terms since they can’t accurately call a rodent depressed. I wonder to what extent does that apply to addiction. Two out of the three components of addiction this paper lists are observable behaviors. Is it possible to diagnose rodents with addiction or is it not, such as with depression?

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