AJP - Regulatory, Integrative and Comparative Physiology, Vol 243, Issue 3 218-R222, Copyright © 1982 by American Physiological Society
Alpha-methyl-p-tyrosine shifts circadian temperature rhythms
A. L. Cahill and C. F. Ehret
alpha-Methyl-p-tyrosine shifts the acrophase (time of highest temperature)
of the circadian temperature rhythm of the rat to earlier or later times of
day depending on the phase of the circadian cycle at which the drug is
administered. When alpha-methyl-p-tyrosine methyl ester HCl is injected
intraperitoneally at a dose of 100 mg/kg late in the projected 8-h light
phase, the acrophase of the intraperitoneal temperature rhythm is delayed
by up to 3 h. However, when the same dose of drug is given 9-10 h into the
projected 16-h dark phase of the daily cycle, the acrophase of the
temperature rhythm occurs about 2 h earlier than expected. The times of
alpha-methyl-p-tyrosine administration leading to maximal phase delays or
advances are correlated with the times of minimal and maximal turnover of
norepinephrine in the hypothalamus. These results suggest that changing
rates of norepinephrine turnover in the hypothalamus may regulate the
circadian temperature rhythm in rats. The results also emphasize the fact
that the effects of drugs may vary as a function of the time of
administration. This fact must be taken into account in pharmacologic
testing.
