Immediate Hypersensitivity in the Flinders Rat: Further Evidence for a Possible Link between Susceptibility to Allergies and Depression

Rats of the Flinders sensitive line (FSL, selectively bred for their increased cholinergic activity and used as a genetic animal model of depression) were compared with their control counterparts, the Flinders resistant line, for their susceptibility to anaphylaxis and the response of small intestinal tissues to the muscarinic agonist, bethanechol. Following sensitization to ovalbumin (OA), rats of both lines were challenged in vivo either with 3 mg OA i.p. or with saline. In spite of the absence of line-related differences in IgE titers, FSL rats were more susceptible to the induction of anaphylactic shock as evidenced by (1) more pronounced mast cell degranulation; (2) a greater drop in rectal temperature; (3) higher hematocrit values; and (4) changes in gut function characterized by an elevation of basal short-circuit current and increased conductance (indicating increases in transport tone and permeability) of the tissues mounted in Ussing chambers. Thus, this study provides further evidence for a common cholinergic mechanisms in susceptibility to both allergies and depression.