Recent findings have identified an endogenous brain system mediating the actions of cannabis sativa preparations. This system includes the brain cannabinoid receptor (CB-1) and its endogenous ligands anandamide and 2-arachidonoyl-glycerol. The endogenous cannabinoid system is not only present in the adult brain, but is also active at early stages of brain development. Studies developed at our laboratory have revealed that maternal exposure to psychoactive cannabinoid results in neuro-developmental alterations. A model is proposed in which early Δ9-tetrahydrocannabinol (THC) exposure during critical developmental periods results in permanent alterations in brain function by either the stimulation of CB-1 receptors present during the development, or by the alterations in maternal glucocorticoid secretion. Those alterations will be revealed in adulthood after challenges either with drugs (i.e. opiates) or with environmental stressors (i.e. novelty). They will include a modified pattern of neuro-chemical, endocrine, and behavioral responses that might lead ultimately to inadaptation and vulnerability to opiate abuse.

It would be reasonable to expect that our previous experience regarding a stimulus that predicts harm would make the subsequent identification of that stimulus easier when harm happens again. Forty-eight volunteers were submitted to both phases of this sequence of events: learning of the predictive relationship and later priming. A face with neutral expression (CS+) was paired with a moderately aversive electric shock and another (CS−) with a neutral tone. Subsequently, these two faces, as well as other known and new faces, were presented for familiarity judgments. Both the CS+ and the CS− faces were preceded by an aversive stimulus (aversive prime) in one occasion and by a neutral stimulus (neutral prime) in another. The familiarity judgment regarding the CS+ was faster after the aversive prime than after the neutral prime, but there was no difference regarding the CS−. The differential effect of the aversive prime over the CS+ and the CS− showed a significant but small correlation with the differential skin conductance response to CS+ and CS− (signal learning), and with the differential evaluation of those stimuli in terms of like-dislike (evaluative learning). The scope of these results, as well as the usefulness of this methodological model, is discussed.