5-Hydroxytryptamine and Rat Passive Peritoneal Anaphylaxis

Abstract

Antigen challenge of rats, sensitized by intraperitoneal injection with rat anti-serum, did not result in a detectable increase in the 5-hydroxytryptamine (5-HT) levels in their peritoneal fluids over the background level induced by sensitisation alone. The maximum amount of extravasation produced by intraperitoneal injection of 5-HT into passively sensitised rats was less than that produced by antigen or histamine, and the doses of 5-HT producing these levels of extravasation produced an increase of 5-HT concentrations in the peritoneal fluids. Therefore, 5-HT is unlikely to make much direct contribution to the extravasation produced during rat passive peritoneal anaphylaxis. However, when given intra-peritoneally to rats, 5-HT potentiates the extravasation produced by histamine.

Rat Passive Peritoneal Anaphylaxis Following Sensitisation with Guinea Pig Antiserum: an Immediate Hypersensitivity Reaction without Histamine Release

“…It contrasts with peritoneal anaphylaxis pro duced in rats after sensitisation with antise ra raised in rats or mice by IgE-directing schedules, in which histamine is the main mediator of the extravasation produced [21,24]. Extravasation, during PPA in rats sen sitised with guinea pig antiserum, was not reduced by prior treatment of the rats with the H, antihistamines pyrilamine and cy proheptadine [8], given at doses which pro duced a marked inhibition of extravasation in PPA produced in rats sensitised with rat antiserum [23], Methysergide, a 5-HT an tagonist [8], when given at high doses [22], also failed to inhibit extravasation of PPA in rats sensitised with guinea pig antiserum. Administration of high doses of the SRS-A antagonist FPL 55712 [1] or BRL 19880 [5] to rats, just before subjecting them to this type of PPA, had no effect on the extra vasation.…”

“…Antisera were produced in mice and rats as de scribed previously [21,24], Passive Peritoneal Anaphylaxis (PPA) PPA was carried out as described previously [22], Groups of 6-8 rats were used in all experi ments. Rats were given intraperitoneal injections of 2 ml of a dilution of the antiserum in isotonic saline.…”