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The Journal of Neurophysiology Vol. 84 No. 6 December 2000, pp. 2844-2858
Copyright ©2000 by the American Physiological Society
1Department of Physiology, Faculty of Medicine, Toyama Medical and Pharmaceutical University, Toyama 930-0194; 2Torii Nutrient-stasis Project, Exploratory Research for Advanced Technology, Research Development Corporation of Japan, Technowave 100, Kanagawa-ku, Yokohama 221-0031; and 3Basic Research Laboratories, Central Research Laboratories, Ajinomoto Company, Kawasaki-ku, Kawasaki 210-8681, Japan
Tamura, Ryoi,
Takashi Kondoh,
Taketoshi Ono,
Hisao Nishijo, and
Kunio Torii.
Effects of Repeated Cold Stress on Activity of Hypothalamic
Neurons in Rats During Performance of Operant Licking Task. J. Neurophysiol. 84: 2844-2858, 2000. The present
study investigated the effects of repeated cold stress on single neuron
activity in the lateral hypothalamic area (LHA) and medial hypothalamic
area (MHA) of behaving rats. The rats were trained to lick a protruding
spout in response to one of several cue-tone stimuli (CTSs) to ingest
water, or amino acid, NaCl or glucose solution. Following this
training, the rats were raised under either stressed (repeated
temperature changes between
3 and 24°C) or control (24°C)
condition for 2 mo. During this period, neuronal activity was recorded
in the LHA and MHA. For rats raised under the stressed condition, mean
spontaneous firing rate of LHA neurons was significantly greater than
for rats under the control condition. More LHA neurons in the stressed
rats responded, with an accompanying decrease in activity (inhibitory
response), to CTSs than in the control rats. During extinction
learning, some LHA neurons enhanced or reversed the responses to CTSs
in the stressed rats, whereas no LHA neurons showed such response changes in the control rats. In contrast to the effects of the stressed
condition on LHA neuron activity, mean spontaneous firing rate of MHA
neurons in the stressed rats was significantly smaller than in the
control rats. Fewer MHA neurons in the stressed rats responded to CTSs
and/or ingestion of sapid solutions. The preceding results suggested
that repeated cold stress produces a specific pattern of changes in
spontaneous activity and responses to sensory stimuli in LHA and MHA
neurons; this could underlie the behavioral changes induced by repeated
cold stress such as hyperphagia and hyper-reactivity to sensory stimuli.
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