Persistent hormonal effects of stress are not due to reduced food intake or exposure to stressed rats

Exposure to inescapable stress elicits persistent effects on the physiology and behavior of rats. Elevated basal plasma corticosterone concentrations have been observed for several days after cessation of stress. In this stud y, we measured hormonal concentrations in multiple axes at multiple levels, 24 h after one or three consecutive exposures to the same stress paradigm. The data indicated persistent activation of plasma corticosterone and prol actin concentrations, whereas plasma triiodothyronine, thyroxine, luteinizi ng hormone, and growth hormone concentrations were inhibited after either o ne or three stress sessions. In addition, we isolated the effects of restra int/tail shock per se from the effects of being moved and exposed to other stressed rats, and from the effects of reduced feeding produced by our stre ss protocol. The data clearly indicated that the stress paradigm, rather th an exposure to stressed rats or decreased nutrient intake, is necessary to induce the persistent physiologic changes we observe after stressed exposur es.