Serotonin 5-HT<sub>1A</sub>, 5-HT<sub>2A</sub> and 5-HT<sub>7</sub> Receptors in the Brainof Mice of BTBR Strain – The Model of Autism
Autism spectrum disorders (ASDs) are among the biggest epidemiological problems of humanity. Despite the enormous efforts of the scientific community, the mechanisms underlying the ASDs are far from being understood. Data on the brain serotonin (5-HT) system role in the development of ASDs are scarce and contradictory. Here we examined the functional response and expression of 5-HT<sub>1A</sub>, 5-HT<sub>2A</sub>, and 5-HT<sub>7</sub> receptors in the brain structures of BTBR mice, a widely used model of autism. BTBR mice showed a significant decrease in the 5-HT<sub>1A</sub> receptor-mediated hypothermic response compared to control C57BL/6J mice. Herewith, there was no significant difference between BTBR and C57BL/6J mice both in the 5-HT<sub>1A</sub> receptor mRNA and protein level in all investigated brain structures. The functional response of the 5-HT<sub>2A</sub> receptor as well as its protein level did not differ between BTBR and control mice. However, the 5-HT<sub>2A</sub> receptor gene mRNA was reduced in the hippocampus of BTBR mice. The functional activity, mRNA and protein levels for 5-HT<sub>7</sub> receptors were unchanged in BTBR mice compared with C57BL/6J mice. Thus, it was shown that the 5-HT<sub>1A</sub> receptor functional activity was significantly reduced in the brain of BTBR mice without significant changes in the 5-HT<sub>1A</sub> receptor expression. At the same time, the expression of the 5-HT<sub>2A</sub> receptor gene was changed along with unaltered 5-HT<sub>2A</sub> receptor functional activity and protein level. The expression and functional response of 5-HT<sub>7</sub> receptor did not differ in all investigated brain structures of the studied mouse strains.