The neurobiology of obsessive-compulsive disorder : neuroanatomy, neurochemistry, and pharmacotherapy

Dissertation (PhD)--Stellenbosch University, 2001.ENGLISH ABSTRACT: Obsessive-compulsive disorder (OCD) is characterized by intrusive thoughts (obsessions) and repetiti ve mental acts or behaviours (compulsions) . For many years, it was considered a rather uncommon condition, caused by unconscious conflict, and somewhat resistant to treatment. In recent decades, however, it has emerged that OCD is a highly prevalent disorder, mediated by particular neuroanatomical circuits (e.g. striatal pathways) and neurochemical systems (e.g. the serotonin system), and responsive to treatment with serotonin reuptake inhibitors (SRIs) . Nevertheless, many questions remain; about the specificity of neuroanatomical findings to OCD, about the role of the multiple serotonin (5-HT) receptor subtypes (e.g. 5-HT10)' and about the appropriate pharmacotherapy for patients resistent to SRI treatment? In a series of studies, 1) the neuroanatomy of OCD was assessed by means of magnetic resonance imaging and neuropsychological testing, 2) the neurochemistry of OCD was assessed by means of functional brain imaging after administration of a 5-HT10 agonist, and 3) the pharmacotherapy of OCD was explored in a series of treatment-refractory OCD and OCD spectrum disorder patients using SRI augmentation with a dopamine blocker. Although no significant difference was found in the volume of the caudate in women with OCD and controls, there was a significant correlation between caudate volume and neuropsychological dysfunction in patients, consistent with evidence of striatal involvement in OCD. Functional imaging demonstrated behavioural heterogeneity, but brain-behaviour correlations were positive, consistent with preclinical evidence of a role for the 5-HTlD receptor in the mediation of OCD. Finally, preliminary treatment findings with dopamine blocker augmentation of a SRI were promising, consistent with preclinical understandings of the interactions between the dopamine and serotonin systems. Although oeD is a complex disorder, a number of future research avenues hold promise for providing a thorough delineation of its pathogenesis.AFRIKAANSE OPSOMMING: Obsessief-kompulsiewe steuring (OKS) word gekenmerk deur indringende gedagtes (obsessies) en herhalende gedagtes of gedrag (kompulsies). Vir baie jare is dit beskou as 'n redelik seldsame toestand wat veroorsaak word deur onbewustelike konflik, en wat in 'n mate teen behandeling weerstandig is. Meer onlangs het dit egter na vore getree as 'n toestand wat baie dikwels voorkom, wat deur spesifieke neuroanatomiese siklusse (bv. striatale bane) en neurochemiese sisteme (bv. die serotonien-sisteem) teweeg gebring word, en wat op behandeling met serotonien heropname inhibeerders (SHIs) reageer. Nogtans is daar steeds baie vrae; oor die spesifisiteit van neuroanatomiese bevindinge vir OKS, oor die rol van die veelvuldige serotonien (5-HT) reseptor subtipes (bv. 5- HT1D), en oor die toepaslike farmakoterapie vir pasiënte wat weerstandig is vir SHI behandeling. In' n reeks van navorsingstudies, is 1.) die neuroanatomie van OKS deur middel van magnetiese resonans beelding en neurosielkundige toetse ondersoek, 2. ) die neurochemie van OKS deur middel van funksionele breinbeelding na toediening van 'n 5-HT1D agonis bepaal, en 3.) die farmakoterapie van OKS in 'n reeks van behandelingsweerstandige OKS en OKS-spektrum steuring pasiënte - waar gebruik gemaak is van SHI aanvulling met 'n dopamien-blokker - ondersoek. Alhoewel daar geen beduidende verskil in die volume van die caudata in vroue met OKS en kontroles gevind is nie, was daar 'n beduidende korrelasie tussen die caudata volume en neurosielkundige wanfunksionering in pasiënte, in ooreenstemming met striatale betrokkenheid in OKS. Funksionele beelding het positief, in demonstreer, maar ooreenstemming met brein-gedrag pre-kliniese heterogeneïteit korrelasies was in gedrag bewyse vir 'n rol vir die 5-HT1D reseptor in die bemiddeling van OKS. Ten laaste, voorlopige behandelingsbevindinge oor dopamienblokker aanvulling van 'n SHI is belowend, in ooreenstemming met