P2.27. IMMOBILITY RELATED THETA RHYTHM IN THE POSTERIOR HYPOTHALAMIC AREA IN FREELY MOVING RATS
Klaudia Pszczółkowska1,,2, Bartosz Caban1, Renata Bocian1, Tomasz Kowalczyk1
1 University of Lodz, Faculty of Biology and Environmental Protection, Department of Neurobiology, 141/143 Pomorska Street, 90-236 Lodz, Poland
2 University of Lodz Doctoral School of Exact and Natural Sciences, 21/23 Jana Matejki Street, 90-237 Lodz, Poland
INTRODUCTION: Theta rhythm is one of the most prominent examples of rhythmic oscillatory activity in the mammalian brain. It is generated mainly in structures of the limbic cortex, including the hippocampal formation (HPC). Theta rhythm is observed in humans during many physiological processes, such as spatial navigation, paradoxical sleep, and language processes. Considering the correlation with the animal's behavior, rodents’ hippocampal theta rhythm was divided into two types: mobility-related and immobility-related rhythms. Studies from the 1970s showed, that theta rhythm may be also recorded in the posterior hypothalamic nuclei and supramammillary nucleus, together considered as the posterior hypothalamic area (PHa). Further studies have shown the presence of theta rhythm in local recordings from PHa during the performance of voluntary movements by rats.
AIM(S): The aim of present study was to verify whether the PHa is capable of generating, immobility-related theta rhythm in addition to mobility-related subtype described earlier.
METHOD(S): The experiments were conducted on 8 adult, male rats. Each animal was implanted with a 16-channel recording electrode in PHa, during stereotactic surgery. After 7 days of recovery, each animal was subjected to behavioral testing in the open field test. The animals were tested three times a week for the next 3 weeks, in the open field arena for 10min. During the test, radio-transmitted EEG recordings from PHa were collected in conjunction with video recording of each freely moving animal.
RESULTS: Obtained data indicated that theta rhythm can be recorded from PHa in freely moving rats not only during voluntary movements but also during immobility. Furthermore, there were significant differences in basic parameters between both kinds of that rhythmic oscillatory activity.
CONCLUSIONS: Considering the fact that HPC theta rhythm plays a significant role in multiple physiological conditions, further studies exploring the role of local theta activity in PHa seem relevant.
FINANCIAL SUPPORT: The research was funded by a grant from the National Science Center (PL): 2017/25/B/NZ4/01476