Thermoregulation in rats during early postnatal maturation: importance of nitric oxide.
Experiments were carried out to determine the role of nitric oxide in mediating autonomic and behavioral thermoregulatory control in rat pups on postnatal days 1-2, 5-6, and 10-11. For an experiment, each pup received a subcutaneous injection of vehicle, NG-nitro-D-arginine methyl ester (D-NAME; 100 mg/kg), or NG-nitro-L-arginine methyl ester (L-NAME; 100 mg/kg) before being placed in a metabolic chamber or in a thermocline with a linear temperature gradient of 23 to 43 degrees C. In the metabolic chamber, oxygen consumption and core temperature were measured as ambient temperature was decreased from 40 to 15 degrees C over a 60-min period. Decreasing ambient temperature elicited an increase in oxygen consumption in all age groups that received vehicle or d-NAME. The lower critical temperature and peak oxygen consumption upon exposure to cold after vehicle were 41 +/- 10 ml x kg(-1) x min(-1) at 30 degrees C, 43 +/- 12 ml x kg(-1) x min(-1) at 28 degrees C, and 55 +/- 11 ml x kg(-1) x min(-1) at 25 degrees C in the 1- to 2-, 5- to 6-, and 10- to 11-day-old pups, respectively. Administration of L-NAME abolished the oxygen consumption response to cold in the 1- to 2- and 5- to 6-day-old pups and significantly attenuated the oxygen consumption response to cold in the 10- to 11-day-old pups. Selected ambient temperature in the thermocline was not significantly affected by prior administration of D-NAME or L-NAME compared with vehicle. Thus our data provide evidence that the nitric oxide system plays a role in mediating autonomic but not behavioral thermoregulatory control in rat pups during early postnatal maturation.
Malik
Sulleman S
SS
Department of Physiology and Biophysics, Health Sciences Centre, The University of Calgary, Calgary, Alberta, Canada T2N 4N1.
Fewell
James E
JE
D002001:Adipose Tissue, Brown / Q000254:growth & development / Q000502:physiology; D000818:Animals; D000831:Animals, Newborn; D001341:Autonomic Nervous System / Q000254:growth & development* / Q000502:physiology*; D001833:Body Temperature Regulation / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism*; D010101:Oxygen Consumption / Q000502:physiology; D011247:Pregnancy; D051381:Rats; D017207:Rats, Sprague-Dawley
D004791:Enzyme Inhibitors; D009569:Nitric Oxide; D019331:NG-Nitroarginine Methyl Ester