Unilateral adrenalectomy attenuates hemorrhagic shock-induced analgesia in rats.
OBJECTIVE
To assess the importance of the pituitary adrenal axis in producing stress-induced analgesia (SIA) after hemorrhagic shock, we performed formalin tests after hemorrhage and reinfusion in unilaterally adrenalectomized or sham-operated rats.


METHODS
Fifty-two adult Sprague-Dawley rats were divided into seven groups: sham-operation normotensive (n = 8), sham-operation shock (n = 8), adrenalectomy normotensive (n = 7), adrenalectomy shock (n = 7), sham-operation shock + yohimbine (n = 7), sham-operation normotensive + corticosterone (n = 7), and adrenalectomy shock + corticosterone (n = 8). The left adrenal gland was cauterized 24 h before the experiment. The mean blood pressure in the shock groups was kept at 50-60 mmHg for 30 min by draining arterial blood. After the blood-reinfusion or observation period, 10% formalin was injected into the rear paw. Nociceptive behaviors and locomotion were observed and rated for 1 h, using the criteria of Dubuisson and Dennis. In 12 other sham-operated and adrenalectomized rats, plasma adrenalin, noradrenalin, and corticosterone concentrations were measured before and after hemorrhagic shock.


RESULTS
Although the sham-operation shock group showed a lower pain score, the adrenalectomy shock group showed nociceptive behavior similar to that in the normotensive groups. Yohimbine did not affect the SIA; however, corticosterone administration reversed the effects of the adrenalectomy on the SIA. The plasma corticosterone levels in the unilaterally adrenalectomized rats were lower than those in the sham-operated rats and did not increase after hemorrhagic shock.


CONCLUSIONS
These results suggest that adrenocortical systems play an important role in hemorrhagic shock-induced SIA.
Department of Anesthesiology, Graduate School of Comprehensive Human Sciences, Tsukuba University, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8575, Japan.
Taeko
T
Fukuda
Chikako
C
Nishimoto
Masayuki
M
Miyabe
Hidenori
H
Toyooka
D000311:Adrenal Glands / Q000503:physiopathology*; D000315:Adrenalectomy / Q000379:methods*; D000317:Adrenergic alpha-Antagonists / Q000008:administration & dosage / Q000494:pharmacology; D000698:Analgesia; D000818:Animals; D001784:Blood Gas Analysis; D001794:Blood Pressure / Q000502:physiology; D003345:Corticosterone / Q000097:blood / Q000502:physiology; D004837:Epinephrine / Q000097:blood; D006339:Heart Rate / Q000502:physiology; D008297:Male; D009638:Norepinephrine / Q000097:blood; D010147:Pain Measurement; D051381:Rats; D017207:Rats, Sprague-Dawley; D012771:Shock, Hemorrhagic / Q000503:physiopathology*; D013315:Stress, Psychological / Q000503:physiopathology*; D013997:Time Factors; D015016:Yohimbine / Q000008:administration & dosage / Q000494:pharmacology
D000317:Adrenergic alpha-Antagonists; D015016:Yohimbine; D003345:Corticosterone; D009638:Norepinephrine; D004837:Epinephrine