Action of a chronic administration of mescaline in dynamic behavioural situations

The effect of psilocin on memory acquisition, retrieval, and consolidation in the rat

The involvement of the serotonin system in the pathophysiology of schizophrenia has been elucidated by experiments with hallucinogens. Application of a hallucinogen to humans leads to changes in perception, cognition, emotions, and induction of psychotic-like symptoms that resemble symptoms of schizophrenia. In rodent studies, their acute administration affects sensorimotor gating, locomotor activity, social behavior, and cognition including working memory, the phenotypes are considered as an animal model of schizophrenia. The complexity and singularity of human cognition raises questions about the validity of animal models utilizing agonists of 5-HT_2A receptors. The present study thus investigated the effect of psilocin on memory acquisition, reinforced retrieval, and memory consolidation in rats. Psilocin is a main metabolite of psilocybin acting as an agonist at 5-HT_2A receptors with a contribution of 5-HT_2C and 5-HT_1A receptors. First, we tested the effect of psilocin on the acquisition of a Carousel maze, a spatial task requiring navigation using distal cues, attention, and cognitive coordination. Psilocin significantly impaired the acquisition of the Carousel maze at both doses (1 and 4 mg/kg). The higher dose of psilocin blocked the learning processes even in an additional session when the rats received only saline. Next, we examined the effect of psilocin on reinforced retrieval and consolidation in the Morris water maze (MWM). The dose of 4 mg/kg disrupted reinforced retrieval in the MWM. However, the application of a lower dose was without any significant effect. Finally, neither the low nor high dose of psilocin injected post-training caused a deficit in memory consolidation in the MWM. Taken together, the psilocin dose dependently impaired the acquisition of the Carousel maze and reinforced retrieval in MWM; however, it had no effect on memory consolidation.

Behavioral modifications in relation to hypothyroidism and hyperthyroidism in adult rats

1. Behavioural experiments were carried out on adult rats made hypothyroid and hyperthyroid. The hypothyroid rats in an "open field" situation reduced the number of squares crossed and boluses defecated, the hyperthyroid rats reduced the number of squares crossed. A swimming endurance was conducted to evaluate the physical resistance of the rats: only hypothyroidism affected the performance. 2. Two operant tests were studied: a) an "extinction" trial (60 min), in which the rats trained in a fixed ratio schedule (FR 1:10), were no longer rewarded with pellets of food and b) the "reversal" test in which the contingency for food delivery was switched four times from one lever, where responses were previously reinforced, to the other lever where responses had no programmed consequences. 3. Both hypo and hyperthyroid conditions caused a lower rate of responses during the "extinction" trial, while in the "reversal" test only hyperthyroid rats showed improved performances. 4. Our data clearly demonstrate behavioural changes in adult hypothyroid and hyperthyroid rats.

Mescaline action on "memory decay" and "problem solving" behavior in the rat

The modifications of behavior caused in the rat by a chronic oral administration of mescaline have been studied in three experimental situations. In the staircase maze mescaline accelerated the spontaneous decay on the conditioned reflex (memory decay) during the period without daily training. Only the results observed at 30 mg/kg/day of mescaline were statistically significant. In a T maze two lateral alleys closed by two swinging doors, 30 mg/kg/day of mescaline increased the time spent in opening the first door. When the two doors of the lateral alleys were closed with a latch, mescaline 30 mg/kg/day, caused an increase in the time spent by the rat in opening the doors. Mescaline caused an increase in food consumption. The increase at 30 mg/kg/day is statistically significant.