RESUMO
BACKGROUND AND PURPOSE: Insufficient prefrontal dopamine 1 (D1 ) receptor signalling has been linked to cognitive dysfunction in several psychiatric conditions. Because the PDE1 isoform B (PDE1B) is postulated to regulate D1 receptor-dependent signal transduction, in this study we aimed to elucidate the role of PDE1 in cognitive processes reliant on D1 receptor function. EXPERIMENTAL APPROACH: Cognitive performance of the D1 receptor agonist, SKF38393, was studied in the T-maze continuous alternation task and 5-choice serial reaction time task. D1 receptor/PDE1B double-immunohistochemistry was performed using human and rat prefrontal brain sections. The pharmacological activity of the PDE1 inhibitor, ITI-214, was assessed by measuring the increase in cAMP/cGMP in prefrontal brain tissue and its effect on working memory performance. Mechanistic studies on the modulation of prefrontal neuronal transmission by SKF38393 and ITI-214 were performed using extracellular recordings in brain slices. KEY RESULTS: SKF38393 improved working memory and attentional performance in rodents. D1 receptor/PDE1B co-expression was verified in both human and rat prefrontal brain sections. The pharmacological activity of ITI-214 on its target, PDE1, was demonstrated by its ability to increase prefrontal cAMP/cGMP. In addition, ITI-214 improved working memory performance. Both SKF38393 and ITI-214 facilitated neuronal transmission in prefrontal brain slices. CONCLUSION AND IMPLICATIONS: We hypothesize that PDE1 inhibition improves working memory performance by increasing prefrontal synaptic transmission and/or postsynaptic D1 receptor signalling, by modulating prefrontal downstream second messenger levels. These data, therefore, support the use of PDE1 inhibitors as a potential approach for the treatment of cognitive dysfunction.
Assuntos
2,3,4,5-Tetra-Hidro-7,8-Di-Hidroxi-1-Fenil-1H-3-Benzazepina/farmacologia , Cognição/efeitos dos fármacos , Nucleotídeo Cíclico Fosfodiesterase do Tipo 1/antagonistas & inibidores , Agonistas de Dopamina/farmacologia , Compostos Heterocíclicos de 4 ou mais Anéis/farmacologia , Receptores de Dopamina D1/metabolismo , Animais , Encéfalo/efeitos dos fármacos , Encéfalo/metabolismo , Encéfalo/fisiologia , Disfunção Cognitiva/tratamento farmacológico , AMP Cíclico/metabolismo , GMP Cíclico/metabolismo , Masculino , Aprendizagem em Labirinto/efeitos dos fármacos , Memória de Curto Prazo/efeitos dos fármacos , Camundongos , Ratos Sprague-Dawley , Transdução de Sinais , Transmissão Sináptica/efeitos dos fármacosRESUMO
Rats with a previous history of heroin self-administration were studied to assess interactions occurring between cannabinoids and opioids in an animal model of reinstatement of heroin-seeking behaviour. Rats were trained to self-administer heroin and after a long-term extinction were primed with one of the following non-contingent non-reinforced drug administrations: saline (or vehicle), heroin, synthetic cannabinoid CB(1) receptor agonists (WIN 55,212-2 or CP 55,940), opioid antagonist (naloxone) or CB(1) antagonist (SR 141716A), alone or in combination. After primings, lever-pressing activity was recorded and compared to those observed during previous phases of training and extinction. Results of this study showed that (i) priming injections of heroin (0.1 mg/kg) as well as CB(1) agonists WIN 55,212-2 (0.15 or 0.30 mg/kg) and CP 55,940 (0.05 or 0.1 mg/kg) completely restore heroin-seeking behaviour; (ii) primings of naloxone (1 mg/kg) and SR 141716A (0.3 mg/kg) had no effect when administered alone; (iii) heroin-induced reinstatement was fully prevented by pre-treatment with either naloxone or SR 141716A; (iv) pre-treatment with SR 141716A significantly reduced WIN 55,212-2 and CP 55,940 priming effects. These results suggest that cannabinoid CB(1) receptors play an important role in the mechanisms underlying relapse to heroin-seeking and depict CB(1) antagonists as possible therapeutic agents for use in the prevention of relapse to heroin abuse.