Effect of melittin on pituitary-adrenal responsiveness to stress.
We previously have shown that melittin evokes a sustained increase in plasma corticosterone levels of the female rat. Significant increases occurred only during the morning and the duration of the response was increased from 48 h to 8 days by a second milittin injection 3 days after initial exposure to melittin. To further evaluate the effect of melittin on adrenocortical function, rats were given melittin at 09.00 h on days 1 and 4 and on day 8 rats were subjected to a variety of different stresses. Saline-injected rats served as controls. Blood for determining non-stress and stress levels of corticosterone concentration (RIA) was collected by decapitation. In all cases morning but not afternoon non-stress plasma corticosterone levels of melittin-injected rats were higher than those of saline-injected controls; afternoon non-stress corticosterone levels did not differ between groups. Melittin- and saline-treated rats showed comparable corticosterone responses to a morning 2-min restraint stress. In contrast, melittin treatment facilitated the pituitary-adrenal response to rotational and surgical stress as well as the stress of removing one rat from a cage of two. Fifteen min after removal of the first rat of a cage of two, plasma corticosterone levels of the melittin-injected rat were significantly higher than those of saline-injected rats. Likewise, plasma corticosterone levels of melittin-treated rats were higher (P less than 0.05) than those of saline-injected rats 15 min after rotational (10 rpm) and surgical (jugular cutdown and blood withdrawal) stress.(ABSTRACT TRUNCATED AT 250 WORDS)
Dunn
J D
JD
Department of Anatomy, Oral Roberts University, School of Medicine, Tulsa, Oklahoma.
Killion
J J
JJ
D000324:Adrenocorticotropic Hormone / Q000097:blood; D000818:Animals; D001007:Anxiety; D001514:Bee Venoms / Q000494:pharmacology*; D003345:Corticosterone / Q000097:blood; D004777:Environment; D008555:Melitten / Q000494:pharmacology*; D010913:Pituitary-Adrenal System / Q000187:drug effects*; D051381:Rats; D011919:Rats, Inbred Strains; D013312:Stress, Physiological; D013514:Surgical Procedures, Operative; D013997:Time Factors
D001514:Bee Venoms; D008555:Melitten; D000324:Adrenocorticotropic Hormone; D003345:Corticosterone