[Effects of the afferent stimulation on neurons in the medial septal region slices and their modulation by biologically active compounds in hibernating and waking ground squirrels].

Responses of the medial septal (MS-DB) neurons to electrical stimulation of the medial forebrain bundle (MFB) and their modulation by some neuropeptides and monoamines were investigated in brain slices taken from two groups of ground squirrels-hibernating (HGS) and waking (WGS). Electrical stimulation evoked mostly inhibitory effects of various duration. Besides, responses by phase reset of the background rhythmic bursts and short-latency single spike responses were observed. The neuropeptides identified in the brain of hibernators differentially and reversibly modulated responses even in those neurons where they did not influence the level and pattern of the background activity. Effects of the peptides were state-dependent. E.g., the peptide TSKYR increased the duration of inhibitory effects in the HGS but shortened them in the WGS, while TSKY which had low efficacy in the HGS, increased the duration of inhibition in the WGS. Dipeptide DY depressed inhibitory components and augmented excitatory components of responses in the HGS but was much less effective in the WGS. Effects of noradrenaline and serotonin had stronger correlation with their influence on spontaneous activity. It is suggested that endogenous substances provide for the increased latent excitability and reactivity of the MS-DB neurons during seasonal hibernation. Thus, the MS-DB may function as a "sentry post" participating in signal detection and urgent arousal during hibernation.