Harmine impairs memory performance of treated rats and nontreated cagemates.

The interest in psychedelic substances as potential treatments for psychiatric disorders is increasing. The ß-carboline harmine, an Ayahuasca component, presents hallucinogenic and antidepressant effects. Although Ayuahuasca-and consequently harmine-is usually consumed in rituals, the role of social contexts in the behavioral effects of harmine has not been investigated yet. In this sense, affective states may modulate cohabitants' behavior, including learning/memory. This work investigates the effects of harmine on the learning/memory performance of rats evaluated on the contextual and tone fear conditioning (CFC and TFC) and on the plus-maze discriminative avoidance (PMDAT) tasks. The possible influence of a harmine-treated cohabitant was assessed by evaluating rats housed in homogeneous cages-where all the animals were acutely administered with the same treatment (vehicle, 5, 10, or 15 mg/kg harmine), and in heterogeneous cages-where each animal received a different drug treatment. The main results are: (a) harmine impaired CFC (10 mg/kg) and PMDAT discrimination (all doses); and (b) harmine caused a memory deficit in CFC, TFC, and PMDAT of untreated rats kept in heterogeneous cages. Our results show that harmine induces a memory deficit in tasks with emotional contexts. Further, the cohabitation with animals treated with this drug also seems to impair memory performance of untreated animals. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Sex differences in aversive memory in rats: possible role of extinction and reactive emotional factors.

Studies usually show better spatial learning in males and stronger emotional memory in females. Spatial memory differences could relate to diverse strategies, while dissimilar stress reactions could cause emotional memory differences. We compared male and female rats in two emotional (classical emotional conditioning and aversive discrimination memory) and two emotionally "neutral" tasks: (1) plus-maze discriminative avoidance, containing two open and two enclosed arms, one of which presenting aversive stimuli (light/noise). No differences were found in learning, retrieving, or basal emotional levels, while only male rats presented extinction of the task; (2) contextual fear conditioning--a cage was paired to mild foot shocks. Upon reexposure, freezing behavior was decreased in females; (3) spontaneous alternation--the animals were expected to alternate among the arms of a four-arm maze. No differences between genders were found and (4) open-field habituation was addressed in an arena which the rats were allowed to explore for 10 min. Habituation was similar between genders. Differences were found only in tasks with strong emotional contexts, where different fear responses and stress effects could be determinant. The lack of extinction of discriminative avoidance by females points out to stronger consolidation and/or impaired extinction of aversive memories.