Intracerebroventricular injection of prostaglandin E-1 changes concentrations of biogenic amines in the posterior hypothalamus of the rat

Since the posterior hypothalamus (PH) plays a key role in the control of bo dy temperature, the aim of this study was to evaluate the changes in adrena line, noradrenaline and dopamine levels in the PH during the hyperthermia i nduced by prostaglandin E-1 (PGE(1)). The concentration of adrenaline, nora drenaline and dopamine in the PH, the firing rate of the sympathetic nerves innervating interscapular brown adipose tissue (IBAT), IBAT and colonic te mperatures (T-IBAT and T-C) were monitored in 12 urethane-anaesthetized mal e Sprague-Dawley rats before and after an intracerebroventricular injection of 500 ng PGE(1) dissolved in 2 mu l of 0.9% NaCl saline solution or only saline. The catecholamines were collected using a microdialysis probe and q uantified by HPLC. The results showed that PGE(1) caused a significant incr ement in the concentration of adrenaline from 15.83+/-2.69 to 34.95+/-3.9 n g ml(-1) and of dopamine from 35.15+/-4.48 to 55.68+/-6.21 ng ml(-1). A sig nificant decrease in the level of noradrenaline from 18.75+/-2.05 to 8.56+/ -2.26 ng ml(-1) was registered. The firing rate of sympathetic nerves to IB AT was increased from 100+/-0% to 204.83+/-15.22% by PGE(1). T-IBAT and T-C rose respectively from 36.91+/-0.15 degrees C to 38.88+/-0.29 degrees C, a nd from 36.7+/-0.15 degrees C to 38.13+/-0.36 degrees C after the injection of PGE(1). The changes in adrenaline and noradrenaline occurred during the first 20 min as did the changes in temperature and firing rate, while the change in dopamine was delayed until 21-60 min after the PGE(1) injection. No significant change of analyzed variables was found in the control rats. These findings suggest that these biogenic amines of the PH are involved in the control of the sympathetic and thermogenic changes induced by PGE(1). (C) 2000 Elsevier Science B.V. All rights reserved.