The co-occurrence of drug addiction in adults with attention deficit hyperactivity disorder (ADHD) is very common, but its etiology remains largely unknown. Therefore, animal models to study this kind of psychiatric comorbidity are needed. The Spontaneously Hypertensive Rat (SHR) strain shows neurochemical and behavioral characteristics which make it a suitable model of ADHD. Compared with their normotensive controls (Wistar-Kyoto) and with some other rat strains, SHR rats drink more ethanol and are more sensitive to its anxiolytic/stimulant effects. They also show increased sensitivity to psychostimulants, opioids and cannabinoids. Furthermore, chronic treatment with methylphenidate, the first-choice drug to treat ADHD, during adolescence, changes the ethanol...

The endocannabinoid signaling system is composed of the cannabinoid receptors; their endogenous ligands, the endocannabinoids; the enzymes that produce and inactivate the endocannabinoids; and the endocannabinoid transporters. The endocannabinoids are a new family of lipidic signal mediators, which includes amides, esters, and ethers of long-chain polyunsaturated fatty acids. Endocannabinoids signal through the same cell surface receptors that are targeted by 9 -tetrahydrocannabinol (9 -THC), the active principles of cannabis sativa preparations like hashish and marijuana. The biosynthetic pathways for the synthesis and release of endocannabinoids are still rather uncertain. Unlike neurotransmitter molecules that are typically held in vesicles before synaptic release, endocannabinoids are synthesized...