Emerging drugs for attention-deficit/hyperactivity disorder

Pharmacological characterization of N-[(2S)-5-(6-fluoro-3-pyridinyl)-2, 3-dihydro-1H-inden-2-yl]-2-propanesulfonamide: a novel, clinical AMPA receptor positive allosteric modulator

BACKGROUND AND PURPOSE

AMPA receptor positive allosteric modulators represent a potential therapeutic strategy to improve cognition in people with schizophrenia. These studies collectively constitute the preclinical pharmacology data package used to build confidence in the pharmacology of this molecule and enable a clinical trial application.

EXPERIMENTAL APPROACH

[N-[(2S)-5-(6-fluoro-3-pyridinyl)-2,3-dihydro 1H-inden-2-yl]-2-propanesulfonamide] (UoS12258) was profiled in a number of in vitro and in vivo studies to highlight its suitability as a novel therapeutic agent.

KEY RESULTS

We demonstrated that UoS12258 is a selective, positive allosteric modulator of the AMPA receptor. At rat native hetero-oligomeric AMPA receptors, UoS12258 displayed a minimum effective concentration of approximately 10 nM in vitro and enhanced AMPA receptor-mediated synaptic transmission at an estimated free brain concentration of approximately 15 nM in vivo. UoS12258 reversed a delay-induced deficit in novel object recognition in rats after both acute and sub-chronic dosing. Sub-chronic dosing reduced the minimum effective dose from 0.3 to 0.03 mg·kg^-1 . UoS12258 was also effective at improving performance in two other cognition models, passive avoidance in scopolamine-impaired rats and water maze learning and retention in aged rats. In side-effect profiling studies, UoS12258 did not produce significant changes in the maximal electroshock threshold test at doses below 10 mg·kg^-1 .

CONCLUSION AND IMPLICATIONS

We conclude that UoS12258 is a potent and selective AMPA receptor modulator exhibiting cognition enhancing properties in several rat behavioural models superior to other molecules that have previously entered clinical evaluation.

Oroxylin A improves attention deficit hyperactivity disorder-like behaviors in the spontaneously hypertensive rat and inhibits reuptake of dopamine in vitro

In previous studies we have demonstrated that the γ-aminobutryic acid-A (GABA-A) receptor antagonist oroxylin A has an awakening effect and it also represses ADHD-like behaviors (hyperactivity, impulsivity and inattention) in the spontaneously hypertensive rat (SHR) model of attention-deficit hyperactivity disorder (ADHD). We hypothesized that the effects of oroxylin A were exerted via the GABA-A receptor given the important role of the GABAergic system in ADHD. However, it is possible that aside from the GABAergic system, oroxylin A may influence other systems especially those implicated in ADHD (e.g. DAergic, etc.). To test this hypothesis, we evaluated the effects of GABA agonist, or dopamine (DA) antagonist in oroxylin A-induced alleviation of ADHD-like behaviors in SHR. SHR showed inattention and impulsivity as measured by the Y-maze and the electro-foot shock aversive water drinking tests, respectively. Oroxylin A significantly improved these behaviors, furthermore, its effect on SHR impulsivity was attenuated by haloperidol, a DA antagonist, but not by baicalein, an agonist of the GABA-A receptor. In vitro studies showed that oroxylin A inhibited DA uptake similar to methylphenidate, a dopamine transporter blocker, but did not influence norepinephrine uptake unlike atomoxetine, a selective NE reuptake inhibitor. Collectively, the present findings suggest that oroxylin A improves ADHD-like behaviors in SHR via enhancement of DA neurotransmission and not modulation of GABA pathway as previously reported. Importantly, the present study indicates the potential therapeutic value of oroxylin A in the treatment of ADHD.

Psychopharmacology of ADHD in pediatrics: current advances and issues

Attention deficit hyperactivity disorder (ADHD) is a neurobehavioral developmental disorder found in 3% to 8% of children and adolescents. An important part of ADHD management is psychopharmacology, which includes stimulants, norepinephrine reuptake inhibitors, alpha-2 agonists, and antidepressants. Medications with the best evidence-based support for ADHD management are the stimulants methylphenidate and amphetamine. A number of newer, long-acting stimulants are now available and a number of new medications are considered that are under current research.