[The effect of thyrotropin-releasing hormone on the activity of the septal neurons in brain slices from hibernating and active susliks Citellus undulatus].

Effects of thyrotropin-releasing hormone (TRH) on spontaneous and evoked activity were tested in the medial septum--diagonal band neurons (MS--DB complex) in the slices taken from the brain of hibernating (HS) and waking (WS) ground squirrels. Administration of TRH (0.1 microM) into the flow of incubating medium increased the frequency of spontaneous activity of all the MS--DB neurons in HS and of the majority of neurons in the WS. However, in the septal slices of HS this increase was significantly more pronounced. The excitatory influence of TRH on the units was preserved in conditions of synaptic blockade. In the neurons from other structures in the brain slices of both HS and WS groups TRH did not affect usually the level of spontaneous discharges. When studying the responses of the MS--DB neurons to electrical stimulation of medial forebrain bundle, it was found that application of TRH led to disappearance of responses in a half of units in both groups of animals. The existence of the forebrain modulatory TRH-system which participates post- and, probably, presynaptically in regulation of the MS--DB neuronal activity is suggested. The role of TRH and of MS--DB in neural control of hibernation is discussed.