EN
INTRODUCTION: Hippocampal formation (HPC) theta rhythm is one of the best examples of neural synchrony in the mammalian brain. It is well-known that the pathway of theta generation originates in the pons, from where it projects to the posterior hypothalamic nuclei, and finally through the medial septal area reaches the HPC. Recent evidence shows that well-synchronized theta rhythm can also successfully be recorded locally from the posterior hypothalamic area (PHa) maintained in vivo and in vitro, specifically from the supramammillary nucleus (SuM) and the primary posterior hypothalamic nuclei (PH). Furthermore, the neuronal activity of the PH and SuM nuclei can be characterized according to the universal classification of theta-related cells which was earlier created for the hippocampus. AIM(S): The purpose of the present study is to investigate theta-related cell activity in posterior hypothalamic slices taken from adolescent rats in order to examine the age at which theta rhythm and accompanying theta-related neuronal activity appears in rats’ PHa. METHOD(S): Forty‑five experiments have been carried out using brain slices taken from 55 Wistar rats aged: 8–10 (A); 13–15 (B); 18–19 (C) and 22–24 (D) days. Each brain slice was perfused with 75 µM carbachol (cholinergic agonist) to induce theta rhythm and accompanying theta-related cell activity in the SuM and PH nuclei. RESULTS: This study resulted in recording 16 theta-related neurons, 56 timing neurons, and 103 neurons classified as non‑related to PHa theta among three experimental groups (B–D). There was no significant theta oscillations and accompanying cell discharges in slices taken from 8–10 days old rats. CONCLUSIONS: Theta oscillations as well as theta-related neuronal activity can be observed in PHa slices delivered from rats not younger than 13–15 days. FINANCIAL SUPPORT: Supported by NCN grant 2013/11/B/NZ4/04872.