[Modulation of neuronal evoked responses to the medial septal area of hibernating ground squirrels by some neuropeptides after chronic disconnection between septum and preoptico-hypothalamic structures].
Effects of some neuropeptides identified in the brain of hibernators (TSKYR, TSKY, DY) and of monoaminergic neurotransmitters (noradrenaline and serotonin) on responses of the medial septal neurons evoked by intraseptal electrical stimulation were analyzed in slices taken from the ground squirrels with chronic basal undercutting of the septum. Despite the elimination of direct contacts with the preoptic area and afferents ascending in the medial forebrain bundle, the neurons retained almost normal level of reactivity and distribution of the reaction types. The neuropeptides effectively modulated neuronal responses of various types, including oligosynaptic short-latency single-spike responses. The latter were strongly facilitated by the neuropeptides. As a rule, changes in the responses to electrical stimulation were independent of the spontaneous activity shifts (in 78% of the tests). It was suggested that the neuropeptides exert a double influence on the septal neurons: direct nonsynaptic effects on the pacemaker potential responsible for the background activity and modulation of synaptic processes. Our experiments showed that descending influences of the septo-hippocampal system are not crucial for the entrance into the hibernation state and its tonic maintenance. The influences of the thermoregulatory--circadian structures of the preoptico-hypothalamic area determine the paradoxically increased latent excitability of septal neurons that allows the septo-hippocampal system to gate external stimuli and organize arousal of the forebrain during hibernation in case of emergency.
Popova
I Iu
IIu
Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences, Pushchino.
Vinogradova
O S
OS
Kokoz
Iu M
IuM
Ziganshin
R Kh
RKh
Ivanov
V T
VT
D000818:Animals; D004558:Electric Stimulation; D004723:Endorphins / Q000494:pharmacology*; D005071:Evoked Potentials; D006605:Hibernation / Q000502:physiology*; D007031:Hypothalamus / Q000502:physiology; D066298:In Vitro Techniques; D009474:Neurons / Q000502:physiology*; D018377:Neurotransmitter Agents / Q000494:pharmacology; D009638:Norepinephrine / Q000494:pharmacology; D010446:Peptide Fragments / Q000494:pharmacology*; D012589:Sciuridae / Q000502:physiology*; D012686:Septal Nuclei / Q000187:drug effects / Q000502:physiology*; D012701:Serotonin / Q000494:pharmacology; D003336:Tectum Mesencephali / Q000502:physiology
D004723:Endorphins; D018377:Neurotransmitter Agents; D010446:Peptide Fragments; C100744:neokyotorphin (1-4); D012701:Serotonin; C036450:neo-kyotorphin; D009638:Norepinephrine