Noradrenaline-induced hypothermia is suppressed in the vagotomized cold-exposed pigeon.
Vagotomized (VX) pigeons studied 2 days after surgery exhibited a significant decrease in cloacal temperature (Tb) and respiratory rate (Rf), and an increase in heart rate (Hf) and metabolic rate (M) at the thermoneutral zone, when compared with sham-operated (SVX) pigeons. The effect of intravenous noradrenaline (NA) on Tb, Rf, Hf and M was examined in SVX and VX-pigeons at 15 degrees C. Following NA administration, the Tb and Rf in the SVX-birds dropped from the preinjection level, but in VX-pigeons, they were not significantly altered. In SVX-pigeons, a total suppression of shivering was apparent following NA-injection, while in the majority of VX-pigeons, shivering was only slightly affected or even increased. The Hf in both SVX- and VX-birds increased following NA-injection. The responses to reserpine were qualitatively similar to NA, although much slower. There were no differences between SVX- and VX-birds with regard to Tb, M and Rf following acetylcholine (ACh) and eserine (Ese) injection. Hf increased after ACh+Ese administration in SVX-pigeons, but in VX-birds, it decreased after an initial surge. Shivering was suppressed for 18-20 min in SVX-birds and 30-50 min in VX-birds. It is suggested that the lack of the hypothermic effect of NA in VX-birds is due to the maintenance of oxygen uptake with unimpaired capacity for shivering.
Hissa
R
R
Department of Zoology, University of Oulu, Finland.
John
M T
MT
Pilo
B
B
Viswanathan
M
M
George
J C
JC
D000109:Acetylcholine / Q000494:pharmacology; D000311:Adrenal Glands / Q000502:physiology; D000818:Animals; D001481:Basal Metabolism / Q000187:drug effects; D001831:Body Temperature / Q000187:drug effects / Q000502:physiology; D003080:Cold Temperature; D010856:Columbidae / Q000502:physiology*; D007035:Hypothermia / Q000139:chemically induced* / Q000503:physiopathology; D009638:Norepinephrine / Q000009:adverse effects* / Q000097:blood; D010830:Physostigmine / Q000494:pharmacology; D012110:Reserpine / Q000494:pharmacology; D012768:Shivering / Q000187:drug effects; D013961:Thyroid Gland / Q000502:physiology; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000097:blood; D014628:Vagotomy
D014284:Triiodothyronine; D012110:Reserpine; D010830:Physostigmine; D000109:Acetylcholine; D013974:Thyroxine; D009638:Norepinephrine