Insect Biochem. Molec. Biol. Vol. 27, No. 8/9, pp. 729–734, 1997  1997 Elsevier Science Ltd Pergamon PII: S0965-1748(97)00051-9 All rights reserved. Printed in Great Britain 0965-1748/97 $17.00 + 0.00 Role of DOPA Decarboxylase and N-Acetyl Transferase in Regulation of Dopamine Content in Drosophila virilis Under Normal and Heat Stress Conditions I. YU. RAUSCHENBACH,* M. JH. SUKHANOVA, L. V. SHUMNAYA, N. E. GRUNTENKO, L. G. GRENBACK, T. M. KHLEBODAROVA, N. A. CHENTSOVA Received 14 January 1997; revised and accepted 8 July 1997 Activity levels of DOPA decarboxylase (DDC), an enzyme responsible for dopamine (DA) synthesis, and of N-acetyl transferase (NAT), an enzyme responsible for its degradation, were studied under normal and stress conditions in two lines of Drosophila virilis which are in contrast concerning their DA content under normal conditions and its alterations under stress. Interlinear differences in DDC activity were detected, and genetic analysis was carried out. It was found out that neither DDC nor NAT activity in D. virilis changed under stress. Based on the results of this study and data obtained earlier by the authors, a mechanism of DA content control under normal and stress conditions was proposed.  1997 Elsevier Science Ltd. All rights reserved DOPA decarboxylase N-Acetyl transferase Dopamine Drosophila virilis Heat stress INTRODUCTION Within the past 15 years, it has been demonstrated in many studies that the content of biogenic amines in insects changes sharply if they are exposed to stress con- ditions. It has been shown that, in insects of various spec- ies from various orders, stress conditions cause an increase in the content of octopamine, dopamine (DA), and in a few cases, serotonin in the hemolymph and tissues of neural origin. This has been demonstrated with the locust (Orchard et al., 1982; Davenport and Evans, 1984), cockroach (Evans, 1985; Kozanek et al., 1986, 1988), honey bee (Harris and Woodring, 1992), Droso- phila (Rauschenbach et al., 1993) and beetle (Hirashima et al., 1992, 1993a,b, 1994; Hirashima and Eto, 1993a– c). Response of the system of biogenic amines to stress also appears to be non-specific. It arises under the action of high and low temperatures, high density, mechanical and chemical stimuli, under social and immobilization stress (Davenport and Evans, 1984; Kozanek et al., 1988; Hirashima and Eto, 1993a–c; Rauschenbach et al., 1993). *Author for correspondence. Institute of Cytology and Genetics, Siberian Department, Russian Academy of Sciences, Novosibirsk, 630090, Russia 729 It should be noted that in spite of considerable interest in this problem throughout the world, there have been practically no studies aimed at clarifying the question as to which links in the metabolism chain of biogenic amines in insects are responsible for this increase in their content under stress. Judging by the literature available to us, there are also no works in which attempts have been made to study the genetic control of the response of the biogenic amine system to stressing agents. In our laboratory, a model has been developed that allows us to carry out research of this kind. The model consists of two lines of Drosophila virilis which are in contrast in their reaction to stressing factors. Individuals of one line (r line) respond to stress by developing a stress reaction which helps them to adapt to unfavourable conditions. Individuals of the other line (nr line) have no such reaction (Rauschenbach et al., 1987). Using this model, we have studied the state of the DA metabolism system of Drosophila under normal and stress conditions. It has been shown that in D. virilis the amine content in normal conditions and its increase under stress are controlled by genes localized in different link- age groups, on the X chromosome and on an autosome, respectively (Rauschenbach et al., 1993). On the basis of activity examination results regarding three enzymes of