Effects of peripheral noradrenaline administration on certain blood metabolite and hormonal levels in the pigeon

Abstract

1. 1. Three groups of pigeons of both sexes were acclimated to 6, 22 or 35°C for a 3 week period. The 22°C acclimated pigeons were exposed to 6°C for 15, 30 and 60 min respectively after intramuscular injection of saline (0.85%) or noradrenaline (NA, 1 mg/kg). Furthermore this group was exposed to 35°C for 30 min. The other two groups were exposed either to 6 or 35°C for 30 min after the same injections. 2. 2. Exposure to cold significantly decreased plasma levels of both NA and adrenaline (A) 15 min post-injection of saline in the 22°C pigeons. At the same time plasma corticosterone level was slightly higher. NA significantly increased plasma NA ( P < 0.001) and A ( P < 0.05) levels in 15 min and corticosterone level in 30 min ( P < 0.001) post-injection. 3. 3. NA produced significant increase in levels of plasma glucose ( P < 0.01, in 15 min), plasma lactate ( P < 0.05, in 30 min) and plasma FFA ( P < 0.05, in 60 min) in the cold environment. 4. 4. In the 6°C group NA caused a rise only in plasma corticosterone ( P < 0.001) and glucose levels ( P < 0.005) but in the 35°C group only the glucose level was raised 30 min after NA injection in the cold environment. 5. 5. In the 35°C environment plasma lactate level was increased in the warm-acclimated group 30 min post-injection of NA ( P < 0.05). In all the acclimation groups corticosterone level was significantly increased due to the NA injection. 6. 6. These results suggest that the inhibition of shivering and the fall in body temperature due to NA may, at least partly, be due to the shortage of glucose following the blockade of insulin secretion from the pancreas by exogenous NA. However, a direct inhibitory effect of NA on the metabolism of the skeletal muscles cannot be excluded.