Peptidase inhibitor-induced antidiuresis mediated through angiotensin and opioid receptors in the rat hypothalamus

Involvement of protein kinase C and tyrosine kinase in lipopolysaccharide-induced anorexia

Injections of lipopolysaccharide (LPS, 3 microg) into the lateral ventricle elicited anorexia with fever and also decreased body weight in rats. The LPS-induced anorexia was inhibited by intracerebroventicular (i.c.v.) injections of anti-interleukin (IL)-1beta antibody (Ab), chelerythrine, genistein and tyrphostin 46, but not by injections of indomethacin. Consecutive injections of orthovanadate and LPS (0.3 microg, a dose of LPS that did not show any effect on food intake, body weight or body temperature) reduced body weight, but did not induce anorexia. On the other hand, injections of IL-1beta (50 ng) did not influence food intake, although they decreased body weight and produced fever. The IL-1beta-induced decrease in body weight was inhibited by injections of genistein, but not by injections of chelerythrine or indomethacin. These findings suggest that the LPS-induced anorexia is independent of hyperthermia and involves IL-1beta generation, tyrosine kinase (TK) and protein kinase C (PKC). This is the first in vivo evidence that activation of TK and PKC induced by LPS is linked to anorexia.

In vivo evidence that activation of tyrosine kinase is a trigger for lipopolysaccharide-induced fever in rats

We measured the rectal temperature of free-moving, conscious rats after intracerebroventricular (i.c.v.) injections of lipopolysaccharide (LPS) and interleukin-1beta (IL-1beta) with or without various antagonists to investigate the mechanisms involved in LPS-induced fever. LPS (3 microg) elicited significant increases in rectal temperature, which lasted from 0.5 h to more than 8 h after administration. This febrile response was inhibited by pretreatment with L-nitro-arginine (LNA), indomethacin (IND), genistein (GEN), tyrphostin 46 and anti-rat IL-1beta antibody (anti-IL-1beta Ab), but was not inhibited by pretreatment with daidzein or chelerythrine (CHE) into the ventricle. LPS (0.3 microg) following orthovanadate (i.c.v.) produced fever, although the small amount of LPS (0.3 microg) or orthovanadate alone showed no effect on rectal temperature. I.c.v. injections of IL-1beta also induced fever of approximately 4-h duration. This effect was inhibited by pretreatment with IND and anti-IL-1beta Ab, but was not inhibited by pretreatment with LNA, GEN or CHE into the ventricle. These findings demonstrate that in the central nervous system, LPS increases IL-1beta production after activation of tyrosine kinase and NO synthase, and IL-1beta promotes prostaglandin production resulting in increased rectal temperature. Activation of tyrosine kinase in the central nervous system is probably a trigger for the febrile response induced by LPS.