0231–424X/$ 20.00 © 2012 Akadémiai Kiadó, Budapest Acta Physiologica Hungarica, Volume 99 (2), pp. 126–132 (2012) DOI: 10.1556/APhysiol.99.2012.2.5 Effects of prenatal irradiation on behaviour and hippocampal neurogenesis in adult rats L Tomášová, B Šmajda, J Ševc Institute of Biology and Ecology, Faculty of Science, P. J. Šafárik University in Košice, Košice, Slovak Republic Received: March 31, 2011 Accepted after revision: January 23, 2012 Prenatal irradiation is known to have aversive effects on the brain development, manifested in changes in some behavioural parameters in adult individuals. The aim of our work was to assess the effect of prenatal irradiation on different forms of behaviour and on hippocampal neurogenesis in rats. Pregnant female rats were irradiated with a dose of 1 Gy of gamma rays on the 16 th day of gravidity. The progeny of irradiated and control animals aged 3 months were tested in Morris water maze (MWM), open field (OF) and in elevated plus maze test (PM). The prenatal irradiation negatively influenced the short-term spatial memory in MWM in female rats, although the long-term memory was not impaired. A statistically significant increase of basic locomotor activity in OF was observed in irradiated rats. The comfort behaviour was not altered. The results of PM showed an increase of anxiety in irradiated females. The level of hippocampal neurogenesis, assessed as the number of cells labelled with 5-bromo-2- deoxyuridine in the area of gyrus dentatus, was not statistically different in irradiated rats. Our results indicate, that prenatal irradiation with a low dose of gamma-rays can affect some innate and learned forms of behaviour in adult rats. We did not confirm a relation of behavioural changes to the changes of hippocampal neurogenesis. Keywords: prenatal irradiation, behaviour, hippocampal neurogenesis, rat, pregnant rats, Morris water maze, locomotor activity, gyrus dentatus The results of animal experiments, experiences from the use of ionizing radiation in health care (4) and from irradiation of people in nuclear accidents (18) as well, have shown that ionizing radiation applied during pregnancy has a very negative impact on the developing central nervous system. Prenatal irradiation can interfere with the development of brain in a variety of ways and may alter its normal development and function, which, in turn, can lead to behavioural disorders in the adult age (9). The hippocampus is critical in the integration of neural processes involved in emotional behaviour, learning and memory (13). It has been established recently, that in the area of gyrus dentatus of this brain structure new neurons are produced throughout the life (1, 5). In some studies a close connection between the dose of prenatal irradiation, the decrease of mitotic activity in the hippocampus and alterations of behaviour in adult animals were found (9, 17, 16), but these relations are still not fully understood (3). The main problem, we aimed to address in our experiments was, whether low doses of irradiation, applied during the embryonic development of the individual, would influence mental processes in the adult age and whether structural changes in the brain could be detected. Behavioural changes in the adult age (e.g. deprived learning ability, changes in motoric and emotional responses) after exposure to very low prenatal or perinatal doses represent a serious problem in human medicine (e.g. in radiotherapy of brain tumours in children). Corresponding author: Prof. Beňadik Šmajda E-mail: benadik.smajda@upjs.sk