Concomitant activation of D₁ dopamine and α_2A adrenergic receptors improves cognition better than methylphenidate in...

Methylphenidate is commonly prescribed to manage symptoms of attention-deficit/hyperactivity disorder (ADHD), but like other stimulants it has variable effectiveness. Methylphenidate works by increasing the synaptic availability of dopamine and norepinephrine, resulting in stimulation of dopaminergic and adrenergic receptors. One hypothesis is that selective receptor targeting may be more effective clinically and have fewer side effects than non-selective stimulants.

To test this hypothesis, we compared methylphenidate with three compounds: the selective D_1/5 dopamine agonist 2-methyldihydrexidine; the selective α_2A adrenergic agonist guanfacine; and the cannabinoid compound cannabigerol, that has α_2A agonist properties and was included given the increasing recreational cannabis use among individuals with ADHD. Acute effects on temporal order memory, cognitive flexibility, and spatial working memory were evaluated using two rodent behavioral tasks.

Co-administration of an α_2A agonist and a D₁ agonist produced greater cognitive improvement than methylphenidate, but only in rats with poor baseline performance.

These findings suggest that potential benefits may emerge from the coadministration of selective agents (e.g., α_2A and D₁ agonists) and should be considered for further study, especially regarding individuals with decrements in cognitive function.