AJP - Regulatory, Integrative and Comparative Physiology, Vol 256, Issue 6 1293-R1298, Copyright © 1989 by American Physiological Society
Responses of thalamic neurons in rats to skin cooling and hypothalamic temperature
Y. Sakata, A. Morimoto and N. Murakami
Department of Physiology, Yamaguchi University School of Medicine, Japan.
The responses of rat thalamic neurons to skin cooling were
electrophysiologically examined. The responses of cold-excited neurons were
classified into two types. One is a steplike response in which the activity
abruptly increases with skin cooling, and the other is a graded response in
which the activity gradually increases with skin cooling. The sites of
these neurons were histologically identified in the ventrobasal complex of
the thalamus, ventrolateral thalamus, and posterior thalamus. Two-thirds of
them were found in a marginal region of the ventrobasal complex. There is
no specific localization between the sites of thalamic neurons showing the
steplike response and those showing the graded response. Furthermore, the
effects of hypothalamic temperature on the thalamic neurons responding to
skin cooling were observed. The response of thalamic neurons to cold
stimulation of the skin was markedly suppressed during the hypothalamic
warming. These results show that the steplike response is related to
converting thermal analog signals to digital signals and that the graded
response is related to relaying analog patterns of cold signals. Thermal
afferent signals are modulated by hypothalamic temperature and subsequently
cold sensation is modulated.
