Central serotonin level-dependent changes in body temperature following administration of tryptophan to pargyline- and harmaline-pretreated rats.
1. The effect of tryptophan on body temperature was studied in rats pretreated with pargyline, an irreversible monoamine oxidase inhibitor (MAOI), and harmaline, a reversible MAOI. 2. Tryptophan (100 mg/kg IP) produced hypothermia followed by hyperthermia in pargyline-pretreated rats, and hypothermia in harmaline-pretreated rats, but tryptophan did not cause body temperature changes by itself. 3. The tryptophan-induced hypo- and hyperthermic effects, which peaked at about 1 and 6 hr after tryptophan administration, respectively, were accompanied by a significant increase in serotonin (5-HT) levels in the pargyline-pretreated rat brain (75%-138.7% and 207%-240.9% increase, respectively), and the 5-HT levels in the hyperthermic state were significantly higher than those in the hypothermic state. 4. In harmaline-pretreated rats, tryptophan also increased the central 5-HT levels (80.5%-95.5% increase) in the hypothermic state, and the effect peaked at about 1 hr after tryptophan administration. The central 5-HT levels in harmaline-pretreated rats slightly decreased at 6 hr after tryptophan administration and were significantly lower than those in the hyperthermic state in the pargyline-pretreated rats. 5. Tryptophan (100 mg/kg IP) administration decreased 5-hydroxy indole acetic acid (5-HIAA) levels, 5-HT turnover, and dopamine (DA) turnover in the brain of pargyline-pretreated rats, but these parameters were not significantly different between the hypothermic and hyperthermic states (i.e., at 1 and 6 hr after tryptophan administration, respectively). 6. These results suggest that the tryptophan-induced body temperature change depends on the different 5-HT levels in the brain and that the 5-HT level needed to induce hyperthermia is higher than that needed to induce hypothermia.
Abdel-Fattah
A F
AF
Division of Pharmacology, Research Institute for Wakan-Yaku, (Oriental Medicines), Toyama Medical and Pharmaceutical University, Japan.
Matsumoto
K
K
Murakami
Y
Y
Adel-Khalek Gammaz
H
H
Mohamed
M F
MF
Watanabe
H
H
D000818:Animals; D001831:Body Temperature / Q000187:drug effects*; D001921:Brain / Q000187:drug effects* / Q000378:metabolism; D004298:Dopamine / Q000378:metabolism; D006246:Harmaline / Q000008:administration & dosage*; D008297:Male; D008996:Monoamine Oxidase Inhibitors / Q000008:administration & dosage*; D010293:Pargyline / Q000008:administration & dosage*; D051381:Rats; D017208:Rats, Wistar; D012701:Serotonin / Q000378:metabolism*; D014364:Tryptophan / Q000494:pharmacology*
D008996:Monoamine Oxidase Inhibitors; D012701:Serotonin; D014364:Tryptophan; D010293:Pargyline; D006246:Harmaline; D004298:Dopamine