Induced Straub Tail ~li~/'ation Further Behavioral Evidence in Rats for the Involvement of Endorfhins in Stress

SUMMARY Adult male Sprague-Dawley rats briefly immersed-n cold water and forced to swim showed Straub tail elevation, a typical s~gn of opiate stimu-iation, upon removal. The presence of Straub tail was a function of degree of immersion and was reversed by naloxone. Th~s suggests the Straub taft response may be a novel behavioral index of stress-indu~ed endorphin release. Stressful manipulation~ of many sorts have been shown to affect behavior through the release of endogenous opioid peptides. ,~ kil et al. [ 2] reported the induction of analgesia after shock, which correlated with increased opiate-like activity and which was reversible in part by naloxone. Cold water stress produces a similar syndrome {e~g., ref. 3). Other forms of stress including cen/~ifugal rotation and the injection oi hypertonic saline solution may also induce related analgesic states although these may have primarily non-narcotic mediation [4]. In addition to analgesia, a further typical sign of opiate 3timulation in rodents is the Straub tail response. This response consists of tail extension, rigidity snd elevation subsequent to a variety of opiate treatments [ 1,5,6 ]. The response is opiate ~pecific, naloxone reversible and subject to modification by manipulation of bio~nic amines [ 1]. To ftttther characterize stre~ as a ~ioral syndrome with a possible relation to endorphins, stress-induced Straub tail response in the rat was examined in the present experiment. Twenty-four adult male Sprague-Dawley ~ats (Charles River, Portage, .MI) 80~-130days ofage and weighing ~ average of 405 g (rmige = 300-520) o.t the start of testing were individually maintained with food (Teklad 4.0% fat rodent die~) and tap wa~r con~nuot~ly av-,dlable. Normal 12-h/12-h