Biogenic amines such as norepinephrine, dopamine, and serotonin play a well-described role in the treatment of mood disorders and some types of pain. As α2A-adrenoceptors regulate the release of these neurotransmitters, we examined the therapeutic potential of BRL 44408, a potent (Ki=8.5 nm) and selective (>50-fold) α2A-adrenoceptor antagonist (KB=7.9 nm). In rats, BRL 44408 penetrated the central nervous system resulting in peak brain and plasma concentrations of 586 ng/g and 1124 ng/ml, respectively. In a pharmacodynamic assay, pretreatment with BRL 44408 to rats responding under a fixed-ratio 30 operant response paradigm resulted in a rightward shift of the clonidine dose–response curve, an effect indicative of α2-adrenoceptor antagonism in vivo. Consistent with presynaptic autoreceptor antagonism and tonic regulation of neurotransmitter release, acute administration of BRL 44408 elevated extracellular concentrations of norepinephrine and dopamine, but not serotonin, in the medial prefrontal cortex. Additionally, BRL 44408, probably by inhibiting α2A heteroceptors, produced a significant increase in cortical levels of acetylcholine. In the forced swim test and schedule-induced polydipsia assay, BRL 44408 produced an antidepressant-like response by dose-dependently decreasing immobility time and adjunctive water intake, respectively, while in a model of visceral pain, BRL 44408 exhibited analgesic activity by decreasing para-phenylquinone (PPQ)-induced abdominal stretching. Finally, BRL 44408 did not produce deficits in overall motor coordination nor alter general locomotor activity. This preclinical characterization of the neurochemical and behavioural profile of BRL 44408 suggests that selective antagonism of α2A-adrenoceptors may represent an effective treatment strategy for mood disorders and visceral pain.

ABSTRACT

Background: The purpose of this analysis was to compare symptomatic remission rates between risperidone and placebo in a completed randomized controlled trial. Design and Methods: Two hundred ninety (290) adult patients who met DSM-IV criteria for Bipolar I Disorder Manic or Mixed episode were randomized to flexible doses of risperidone or placebo for 3 weeks. An entry Young Mania Rating Scale (YMRS) score of > 20 was required at trial screening and baseline. Time to first onset of remission (as defined as a YMRS score of < 8) was assessed using Cox proportional hazards. Persence or absence of sustained remission was analyzed using logistic regression. Sustained remission was defined as maintaining a YMRS < 8 for the remainder of the trial or until censor. Results: After adjusting for presence of psychosis, baseline YMRS, gender, number of mood cycles in the previous year and treatment,the odds of sustained remission for subjects on risperidone was 5.6 (p < 0.0001). Similarly the adjusted hazard or remission for subjects on rsiperidone was 4.0 (p < 0.0001). Interpretaion: A statistically significant proportion of manic patients receiving risperidone monotherapy achieved symptomatic remission within 3 weeks as compared to placebo.