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Maternal care after childbirth is important for human development and drug consumption can greatly affect it1,2. Different drugs have been shown to reduce cognitive ability of offspring, like, for example, a lack of significant interaction with parental figures during childhood3–5. The effect of drug exposure during pregnancy on maternal care can be studied in animal models, which could be a source of changes of the mother disposition on childcare, having different cognitive or behavioral consequences for the offspring. Rats are an advantageous model of maternal care. These animals exhibit stress responses when they are separated from their pups during their preweaning period6, regardless of not showing preference towards specific individuals. Rats are motivated to take care of their newborns, while they also manifest prosocial behavior towards individuals that they recognize7,8. Parental care and social interaction could have reinforcing capabilities to individuals that receive them, thus these combined can be part of their kin recognition strategies when it comes to parental care9. Among other drugs, cannabis acts on the rewards neural system10, and it can interfere with the rewarding properties of maternal care and social recognition, diminishing their associated behaviors. The endocannabinoid receptor CB1 is involved in the reward circuit of the brain10. For example, Heroin is another drug that has an effect on the same receptor11 and its study has shown a diminishing effect on rat social behavior12. Cannabis exposure can have neurobiological effects on offspring13, adding to the interest of studying the behavioral consequences of THC exposure for its possible analogous effects with heroin on offspring and social behavior. THC (tetrahydrocannabinol, or delta-9-tetrahydrocannabinol; Δ9-THC), is the active component of cannabis sativa, and is mainly the cause of the effects of the drug14. It is important to investigate the possible adverse effects of cannabis consumption even if it has been proposed that it can have health benefits15. Cannabis research becomes more important when infant development can be affected, when people are exposed to drug at an early age. Cannabis consumption has increased among mothers, even during gestation, making it a more pressing matter. We can test the magnitude in which a mother takes care of their own offspring in a rat model, or also, the offspring of other mothers, from birth to weaning age16. Rats are a species that easily adopt litters from other mothers17, making them a good choice to study cross-fostered maternal care. Maternal care can be quantified through specific behaviors directed at infant care, either biological or adopted, by measuring the time the mother spends doing these behaviors18,19. In rats, observable maternal care includes feeding the pups by crouching over them and nesting them together in a spot20,21. Also, the offspring of these mothers can, in turn, be used to test other behaviors affected by experience, like social recognition and play behavior. Rats have been extensively used as a model of the effects of drugs on behavior 22–25 and rat adoption has been used as an experimental control of the effect of drugs on offspring 18,19. Beyond the merely pharmacological effects of drugs, the experience with drugs can affect behavior22,26–33 34. Learning can start in utero and infants can learn about the effects of the drug when they are exposed to it indirectly through the mother, during gestation or nursing2,34,35. Research about the effect of drugs on learning has been conducted mainly with drugs other than cannabis, leaving a gap in the knowledge about this drug in behavior and general learning, including experiences in early development exposure to drugs, in an intrauterine manner, and its effect in the offspring. In this series of experiments, we will compare the effects of cannabis on mothers that were exposed to cannabis during their pregnancy with mothers without such exposure, and the consequences on the offspring behavior. In Experiment 1A and Experiment 1B, maternal care will be measured the at first post-natal day (PND) and a day after. Then, in Experiment 2A and Experiment 2B, the social recognition and play behavior of the offspring in their juvenile age will be evaluated (from PND22 to about PND42). To explore the effect of an adoption procedure and their possible interactions with exposure or non-exposure to cannabis, mothers will be compared between biological mothers and adoptive mothers, both exposed to cannabis and vehicle. These requirements are met with a 2x2 factorial experiment design, with Maternal Experience with Cannabis (with or without experience with cannabis) and Mother status (biological or adoptive) as between group factors. All experiments will then have four groups: Biological-Cann, Biological-NoCann, Adoptive-Cann and Adoptive-NoCann. |
