Inhibition of the preoptic area and anterior hypothalamus by tetrodotoxin alters thermoregulatory functions in exercising rats.
We have previously demonstrated a functional role of the preoptic area and anterior hypothalamus (PO/AH) in thermoregulation in freely moving rats at various temperature conditions by using microdialysis and biotelemetry methods. In the present study, we perfused tetrodotoxin (TTX) solution into the PO/AH to investigate whether this manipulation can modify thermoregulation in exercising rats. Male Wistar rats were trained for 3 wk by treadmill running. Body core temperature (Tb), heart rate (HR), and tail skin temperature (Ttail) were measured. Rats ran for 120 min at speed of 10 m/min, with TTX (5 microM) perfused into the left PO/AH during the last 60 min of exercise through a microdialysis probe (control, n=12; TTX, n=12). Tb, HR, and Ttail increased during the first 20 min of exercise. Thereafter, Tb, HR, and Ttail were stable in both groups. Perfusion of TTX into the PO/AH evoked an additional rise in Tb (control: 38.2 +/- 0.1 degrees C, TTX: 39.3 +/- 0.2 degrees C; P <0.001) with a significant decrease in Ttail (control: 31.2 +/- 0.5 degrees C, TTX: 28.3 +/- 0.7 degrees C; P <0.01) and a significant increase in HR (control: 425.2 +/- 12 beats/min, TTX: 502.1 +/- 13 beats/min; P <0.01). These results suggest that the TTX-induced hyperthermia was the result of both an impairment of heat loss and an elevation of heat production during exercise. We therefore propose the PO/AH as an important thermoregulatory site in the brain during exercise.
Hasegawa
Hiroshi
H
Dept. of Human Physiology and Sportsmedicine, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium. hhasegaw@vub.ac.be
Ishiwata
Takayuki
T
Saito
Takehito
T
Yazawa
Toru
T
Aihara
Yasutsugu
Y
Meeusen
Romain
R
D000818:Animals; D007025:Anterior Hypothalamic Nucleus / Q000187:drug effects / Q000502:physiology*; D001833:Body Temperature Regulation / Q000187:drug effects / Q000502:physiology*; D008297:Male; D017551:Microdialysis / Q000379:methods; D009498:Neurotoxins / Q000494:pharmacology; D010805:Physical Conditioning, Animal / Q000379:methods; D005082:Physical Exertion / Q000502:physiology*; D011301:Preoptic Area / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D013779:Tetrodotoxin / Q000008:administration & dosage*
D009498:Neurotoxins; D013779:Tetrodotoxin