AJP - Regulatory, Integrative and Comparative Physiology, Vol 238, Issue 5 364-R371, Copyright © 1980 by American Physiological Society
Effects of brain monoamine depletions on thermoregulation in rabbits
M. T. Lin
Biochemical analyses revealed that 5,7-dihydroxytryptamine- (5,7-DHT)
treated and 6-hydroxydopamine- (6-OHDA) treated rabbits, respectively, had
a significant reduction in diencephalic 5-hydroxytryptamine (5-HT) and
norepinephrine (NE) with minimal alterations in the other monoamines. Both
5,7-DHT-treated and 6-OHDA-treated animals, although showing the
maintenance of normal body temperatures, did exhibit specific alterations
in the thermoeffector outputs. The 5-HT-depleted animals displayed an
increase in ear skin blood flow, respiratory heat loss, and metabolism at
both ambient temperatures (Ta) of 22 and 2 degrees C. The NE-depleted
animals displayed a decrease in metabolism at all levels of Ta tested.
Also, the peripheral temperature threshold for the onset of heat loss
responses were displaced to higher values than in control animals. In
addition, the prostaglandin E1-induced fever was attenuated after the
pretreatment of rabbits with either 5,7-DHT or 6-OHDA. The data indicate
that brain levels of 5-HT and NE alter, in an apparently reciprocal
fashion, the thermoregulatory responses of rabbits. Also, the integrity of
5-HT and NE pathways in brain is vital for the full functioning of a
prostaglandin in producing a fever.
