Changes in extracellular serotonin in rat hypothalamus affect thermoregulatory function.
Experiments were carried out to determine the effects of altering the serotonin (5-HT) levels in the hypothalamus on thermoregulatory function in unanesthetized restrained rats. Local perfusion of the hypothalamus with dialysis solution containing 5-hydroxytryptophan (a 5-HT precursor), fluoxetine (a 5-HT reuptake inhibitor), or high potassium significantly increased both colonic temperature (Tco) and the extracellular concentrations of 5-HT in the hypothalamus. Reciprocally, both extracellular concentration of 5-HT in the hypothalamus and Tco were decreased with a dialysis solution containing tetrodotoxin (which blocks the voltage-dependent sodium channel), zero calcium concentration, or systemic administration of 8-hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT,5-HT1A agonist). Intrahypothalamic administration of 8-OH-DPAT and (2,5-dimethoxy-4-iodophenyl)-2-aminopropane (a 5-HT2 agonist) produced hypothermic and hyperthermic effects, respectively. The results indicate that elevating the 5-HT levels in the hypothalamus activates postsynaptic 5-HT2 receptors and results in hyperthermic effects, whereas stimulation of presynaptic 5-HT1A receptors in the hypothalamus reduces the endogenous 5-HT release and results in hypothermic effects.
Lin
M T
MT
Department of Physiology, National Yang-Ming University, Taipei, Taiwan, Republic of China.
Tsay
H J
HJ
Su
W H
WH
Chueh
F Y
FY
D000818:Animals; D001833:Body Temperature Regulation / Q000502:physiology*; D005110:Extracellular Space / Q000378:metabolism; D007031:Hypothalamus / Q000502:physiology* / Q000648:ultrastructure; D008297:Male; D017551:Microdialysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D012701:Serotonin / Q000502:physiology*; D013779:Tetrodotoxin
D012701:Serotonin; D013779:Tetrodotoxin