EN
Theta rhythm is the largest, most prominent and best synchronized rhythmical waveform generated by the mammalian brain. Commonly, theta activity has been associated with hippocampal formation (HPC). Pharmacological and behavioral studies have shown that there were two distinct types of hippocampal theta activity in rodents. The first type (type 1) occurs during voluntary motor behavior and is atropineresistant. The second one (type 2) occurs during immobility and is atropine-sensitive. Interestingly, a number of in vitro reports have revealed that HPC is not the only limbic cortical region involved in the production of theta activity. Theta oscillations have also been recorded from the entorhinal and cingulate cortex in freely behaving or anesthetized rats. In our recent studies we provided for the first time, evidences that atropine-sensitive theta rhythm could be recorded also from posterior hypothalamic (PH) region. Current research has been devoted to determining the pharmacological and electrophysiological profile of PH theta. In separate experiments the effects of carbachol (0.5 µg/µl) and orexin B (0.2 µg/µl) administrations were examined. Microinjection of cholinergic agonist (carbachol) into PH induced well-synchronized theta with increased amplitude and power. However, the local injection of orexin B did not affect PH rhythmic activity. These results confirm cholinergic nature of posterior hypothalamic theta in anesthetized rats. Supported by NCN grant no. 2011/01/B/NZ4/00373.