Spontaneous Activity of Preoptic Neurons in Slice Preparations of the Hypothalamus of European Hamsters (Cricetus cricetus) and Wistar Rats under Different States of Hypothermia

Arousal from hibernation and BAT thermogenesis against cold: central mechanism and molecular basis

“…Indeed the distinction between hibernators and non-hibernators could be characterized by their ability to sustain the activity of CNS neurons under extreme hypothermic conditions. However, electrophysiological recordings from brain slices showed no clear difference in thermal characteristics of CNS neurons between Wistar rats and European hamsters (Hashimoto et al, 1998c). In both animals PO/AH neurons exhibited spontaneous AP but the propagation rate and amplitude was dramatically reduced at low temperature.…”

“…In both in vivo and in vitro experiments, persistence of firing activity or spontaneously firing activity in CNS neurons during hibernation were confirmed even in several hibernator species when body temperatures were low (Wunnenberg et al, 1986;Hashimoto et al, 1998c).…”

“…These results are consistent with the suggestion that the activation of NST during arousal requires the inhibition of the activity of the midbrain tonic inhibitory mechanism, possibly originates from the rostral hypothalamic area. At present it is unknown if the APs recorded in PO/AH neurons (Satinoff, 1967;Hashimoto et al, 1998c) connect to the midbrain inhibitory network or if they are capable of inducing functional post-synaptic events.…”

Neuronal Activity in the Hibernating Brain

“…Although most of the earlier and more recent in vitro studies focused only on the hippocampus, the influence of hypothermia in a hibernating species was also investigated in neurons of the medial preoptic area (MPOA), the suprachiasmatic nucleus (SCN) and the nucleus tractus solitarius (NTS), all of which are brain regions potentially being involved in neuronal control of hibernation. The MPOA controls thermoregulation and was considered to be especially important for the entrance into hibernation (Satinoff, 1967; Hashimoto et al, 1998). Consistent with the results obtained in the hippocampus, spontaneous neuronal activity of MPOA neurons recorded extracellularly in hamster brain slices significantly changed with decreasing temperature, resulting in reduced firing rate and spike amplitude as well as increased spike width (Hashimoto et al, 1998).…”

“…The MPOA controls thermoregulation and was considered to be especially important for the entrance into hibernation (Satinoff, 1967; Hashimoto et al, 1998). Consistent with the results obtained in the hippocampus, spontaneous neuronal activity of MPOA neurons recorded extracellularly in hamster brain slices significantly changed with decreasing temperature, resulting in reduced firing rate and spike amplitude as well as increased spike width (Hashimoto et al, 1998). Almost half of the recorded neurons (42%) were still active below 10°C with an average cutoff temperature of 4.9°C.…”