Mice over-expressing the 5-HT1A receptor in cortex and dentate gyrus display exaggerated locornotor and hypothermic response to 8-OH-DPAT

The scrotonin 1A (5-HT1A)receptor is one of the best described receptor subtypes of the serotonemic system. Due to the complex distribution pattern, the pre- and postsynaptic localisation, the impact on various monoamines, as well as the influence on a wide range of physiological functions, the contribution of 5-HT1A receptors to behavioural outcomes is difficult to define. In this study, we present a new transgenic mouse model with a prominent over-expression of the 5-HT1A receptor in the outer cortical layers (I-III) and the dentate gyrus. Behavioural studies revealed a slight decrease in baseline motor activity of homozygous mice during the open field test. Moreover, core body temperature of male transgenic mice was significantly lower than that of wild-type mice. Pharmacological studies with the 5-HT1A receptor agonist 8-OH-DPAT (0.1-2.5 mg/kg, i.p.) revealed an exaggerated drug response in mutant mice. 8-OH-DPAT led to a drastic decrease in motor activity in the open field and elevated plus maze test. This significant effect oil motor activity became more apparent by investigating the serotonergic syndrome induced by 8-OH-DPAT. Concentration as low as 0.5mg/kg 8-OH-DPAT caused immobility in trans-enic mice for 30 min, head weaving behaviour, and backward walking. whereas in wild-type animals, typical behaviours of the serotonin syndrome were first observed at concentrations of 1.5 mg/kg and more. In addition, the 8-OH-DPAT induced hypothermia was more pronounced in mutant mice than in wild-type animals. Therefore, these genetically modified mice represent a promising model for further investigations of the role of 5-HT1A receptors. (c) 2005 Elsevier B.V. All rights reserved.