0012-4966/05/0506- © 2005 Pleiades Publishing, Inc. 0205 Doklady Biological Sciences, Vol. 402, 2005, pp. 205–207. Translated from Doklady Akademii Nauk, Vol. 402, No. 2, 2005, pp. 282–285. Original Russian Text Copyright © 2005 by Naumenko, Ivanova, Kulikov, Popova. Monoamine oxidase A (MAO A), a mitochondrial enzyme which catalyzes oxidative deamination of monoamines, is one of the main enzymes of the metab- olism of brain neurotransmitters, such as serotonin, dopamine and noradrenalin. Recently, a strain of trans- genic mice (Tg8) with an irreversibly destroyed gene of MAO A was obtained at Curie Institute [1]. Tg8 mice are deprived of MAO A and characterized by high lev- els of serotonin and noradrenalin and low concentra- tions of the final products of the oxidative deamination of serotonin and dopamine, 5-hydroxyindolacetic (5-HIAA) and 3,4-dihydroxyphenylacetic (DOPAA) acids [1, 2]. In this work, we studied the effect of the genetic knockout of MAO A on the functional state and level of the mRNA of 5-çí 1Ä receptors in brain struc- tures. We established that a hereditary absence of MAO A resulted in regional changes in the expression of 5-çí 1Ä receptors in the brain: the sensitivity of 5-çí 1Ä receptors was decreased (desensitization), and the level of the mRNA of 5-çí 1Ä receptors was considerably increased in the frontal cortex and amygdala and remained at the same level in the midbrain and hypo- thalamus of the mice. The changes in the metabolism of neurotransmitter occur at the level of the receptor apparatus. The 5HT 1A receptor is of great interest among many other seroto- nin receptors, because the existing data suggest that 5-çí 1Ä receptors are involved in the regulation of emo- tions and behavior, including anxiety [3], depression [4, 5], and aggression [6, 7]. A characteristic property of mice with the genetic knockout of MAO A is high aggression [1, 8]; however, the effect of MAO A knock- out in the brain on the state of 5HT 1A receptors is not clear. A decrease in the sensitivity of 5HT 1A receptors and a small decrease in the receptor density in the region of the dorsal raphe nucleus, but not in other brain structures, was found in mice deprived of MAO A. Considerable changes in the expression of the mRNA of 5HT 1A receptors were not observed in this part of brain [9], whereas in the other regions, the expression of the mRNA of 5-çí 1Ä receptors was not detected. However, we recently found significant regional speci- ficity of the effect of MAO A knockout on the metabo- lism of serotonin and catecholamines in different brain structures. The frontal cortex was more resistant to the absence of MAO A than others, including the hippoc- ampus, midbrain, hypothalamus, striatum and amygdala [2, 10]. The purpose of this study was to investigate effect of the genetic knockout of MAO A on the functional state of 5-çí 1Ä receptors and the expression of the mRNA of 5-çí 1Ä receptors in brain structures. Experiments were carried out with pubertal Tg8 mice; C3H/HeJ (C3H) mice obtained from Curie Insti- tute (France) served as control. Mice weighed about 25 g and were maintained under the standard condi- tions in the vivarium of the Institute of Cytology and Genetics (Siberian Division, Russian Academy of Sci- ences). The animals were isolated two days before the experiment to exclude the so-called group effect. To determine the expression of 5-çí 1Ä receptor mRNA, the mice were decapitated; the frontal cortex, hypothal- amus, amygdala complex, and dorsal raphe nucleus of the midbrain were dissected on ice. Taq polymerase (30 U/μ l) and M-MLV reverse tran- scriptase (750 U/μ l) were obtained from Biosan (Rus- sia); the dNTP kit was obtained from Sibenzyme (Rus- sia); purified Tris, guanidinethyocyanate, sodium dode- cyl sulphate (SDS), KCl, MgCl 2 , MnCl 2 , dithiothreitol (DTT) and Triton X-100 were obtained from Sigma (United States); purified phenol, chlorophorm, isopro- panol, and ethanol were from Reachim (Russia). The primers for 5-çí 1Ä receptors were developed on the basis of described sequences [11] with the use of the Genrunner software. The PCR products were iden- tified by means of restriction analysis. All oligonucle- otides were synthesized in Biosan (Russia). Genomic DNA extracted from the liver of a male C57BL/6 mouse was used as an exogenous standard; its optical density was determined at wavelengths 260/280 nm. DNA was diluted with sterile water to 100 or 10 ng/μ l and stored at –20°C. The size of the mouse genome is 2.493 × 20 9 bp, and the weight is about 5 pg (Mouse GENERAL BIOLOGY Effect of Monoamine Oxidease A Knockout on the Expression of 5-HT 1A Receptors V. S. Naumenko, E. A. Ivanova, A. V. Kulikov, and N. K. Popova Presented by Academician V.K. Shumnyi August 31, 2004 Received August 31, 2004 Institute of Cytology and Genetics, Siberian Division, Russian Academy of Sciences, pr. Lavrent’eva 10, Novosibirsk, 630060 Russia