THE ALPHA1A ANTAGONIST TAMSULOSIN IMPAIRS MEMORY ACQUISITION, CONSOLIDATION AND RETRIEVAL IN A NOVEL OBJECT RECOGNITION TASK IN MICE.

Tamsulosin is an α1 -adrenoceptor antagonist used to treat benign prostatic hyperplasia. This drug exhibits high affinity for α1A - and α1D -adrenoceptor subtypes, which are also expressed in the brain. While dementia symptoms have been reported after administration of tamsulosin in humans, studies on its effects on the rodent brain are still rare. The present study investigated the effects of tamsulosin (and biperiden, an amnesic drug) on cognitive performance in the object recognition task (ORT). Tamsulosin (0.001-0.01mg/kg) was orally administrated in mice at three distinct time points: pre-training, post-training and pre-test session. Tamsulosin 0.01mg/kg impaired object recognition regardless of when it was injected, whereas at lower doses did not affect mouse performance in the ORT. Biperiden also impaired acquisition and consolidation of object recognition in mice. Furthermore, the effects of tamsulosin on locomotion, motivation and anxiety were excluded as potential confounding factors. At all doses tested, tamsulosin did not alter distance moved, time spent exploring objects in the ORT, and anxiety-related behaviors in the elevated plus-maze test. By contrast, diazepam evoked a significant reduction of anxiety-like behaviours. In conclusion, tamsulosin impaired memory acquisition, consolidation and retrieval in an object recognition task in mice, thus affecting memory performance in a non-specific phase manner. These findings contribute to our understanding of the potential adverse effects of tamsulosin, and shed light on the role played by α1 -adrenoceptors, particularly α1A - subtype, in cognitive processes.