Activation of 5-HT7 receptor by administration of its selective agonist, LP-211, modifies explorative-curiosity behavior in rats in two paradigms which differ in visuospatial parameters

AimsThe serotonin 7 receptor (5-HT7R) subtype, coded by Htr7 gene, is broadly expressed in the central nervous system (CNS) with clear involvement in behavioral functions such as learning/memory, regulation of mood, and circadian rhythms. In this study, we assessed effects of 5-HT7R stimulation by administration of its selective agonist, LP-211 (0.25mg/kg i.p.), in adult Wistar-Han rats. MethodsWe used two different explorative-curiosity tests. Drug was administered either before one side-chamber familiarization (CF/V group) or immediately after it, to act on consolidation of familiarization (V/CF group). ResultsExp. 1 for novelty seeking in black/white boxes (BWB), with door opening after 5minutes in the familiar chamber, showed that (i) time spent in the novel environment (significantly higher than in familiar chamber for controls) is enhanced in V/CF group (potentiated recognition for a visual consolidation) and not different in CF/V group; (ii) activity and chamber transitions, made by CF/V rats, are significantly higher than for other groups (interference on recognition for a spatial acquisition). Exp. 2 for novelty preference in D- vs L-shaped chambers (D/L), with start from neutral center, gave different results: (i) time spent in the novel environment by CF/V group is significantly higher than other groups (potentiated cognitive acquisition); (ii) chamber transitions made by V/CF group are significantly higher than other groups (potentiated emotional consolidation). ConclusionThese apparently conflicting results may reflect LP-211 effects on visual vs spatial memory (D/L apparatus has more pronounced hippocampal components than BWB). However, further experiments are needed to analyze more in depth the mechanisms involved.