CHANGES OF CHARACTERISTICS OF PREOPTIC NEURONS AND NA METABOLISM IN HYPOTHALAMUS OF GROUND-SQUIRREL (CITELLUS-DAUTIEUS) IN DIFFERENT SEASONS AND HIBERNATING PHASES
Jr. Sun et al., CHANGES OF CHARACTERISTICS OF PREOPTIC NEURONS AND NA METABOLISM IN HYPOTHALAMUS OF GROUND-SQUIRREL (CITELLUS-DAUTIEUS) IN DIFFERENT SEASONS AND HIBERNATING PHASES, SCIENCE IN CHINA SERIES C-LIFE SCIENCES, 41(5), 1998, pp. 488-497
The unit firing activities of neurons in the preoptic area (POA) of gr
ound squirrel hypothalamic tissue slices were recorded and the metabol
ism of NA in hypothalamus was measured with high performance liquid ch
romatography (HPLC). Thermosensitivity, proportions, the critical temp
erature (Tc) and the lowest temperature (TL) of firing activity of the
above-mentioned neurons, and NA metabolism in hypothalamus were compa
red in different seasons and hibernating phases. In comparison with th
at in summer euthermar, it was shown that (i) the percentage and therm
osensitivity of the POA neurons varied respectively in the hibernating
phases; (ii) TL and Te of the POA neurons in winter, both euthermar a
nd hibernation, were markedly decreased; (iii) the POA neurons in hibe
rnation became much more sensitive to NA, and the response of cold-sen
sitive neurons to NA changed from inhibiting pattern in summer to exci
ting one in hibernation; (iv) the contents and metabolism of NA in hyp
othalamus decreased significantly in the entering phase and deep hiber
nation phase, while the metabolism of NA increased remarkably in the a
rousal phase. These changes might explain the regulatory mechanism how
ground squirrel actively decreases body temperature (Tb) in entering
into hibernation and quickly recovers body temperature in arousal phas
e.