AJP - Regulatory, Integrative and Comparative Physiology, Vol 235, Issue 1 41-R47, Copyright © 1978 by American Physiological Society
Changes in serotonin contents in brain affect metabolic heat production of rabbits in cold
M. T. Lin, I. H. Pang, S. I. Chern and W. Y. Chia
Elevating serotonin (5-HT) contents in brain with 5-hydroxytryptophan
(5-HTP) reduced rectal temperature (Tre) in rabbits after peripheral
decarboxylase inhibition with the aromatic-L-amino-acid decarboxylase
inhibitor R04-4602 at two ambient temperatures (Ta), 2 and 22 degrees C.
The hypothermia was brought about by both an increase in respiratory
evaporative heat loss (Eres) and a decrease in metabolic rate (MR) in the
cold. At a Ta of 22 degrees C, the hypothermia was achieved solely due to
an increase in heat loss. Depleting brain contents of 5-HT with
intraventricular, 5,7-dihydroxytryptamine (5,7-DHT) produced an increased
Eres and ear blood flow even at Ta of 2 degrees C. Also, MR increased at
all but the Ta of 32 degrees C. However, depleting the central and
peripheral contents of 5-HT with p-chlorophenylalanine (pCPA) produced
lower MR accompanied by lower Eres in the cold compared to the untreated
control. Both groups of pCPA-treated and 5,7-DHT-treated animals maintained
their Tre within normal limits. The data suggest that changes in 5-HT
content in brain affects the MR of rabbits in the cold. Elevating brain
content of 5-HT tends to depress the MR response to cold, while depleting
brain content of 5-HT tends to enhance the MR response to cold.
