Differences in the stress response of Wistar-Kyoto (WKY) rats from different vendors

Wistar-Kyoto (WKY) rats are hyperresponsive to stress and prone to stress ulcer. However, some variability in these general findings has been reported. This variability may reflect differences in the rat stock from different WKY rat vendors. WKY rats from Taconic (WKY-T), Harlan Sprague-Dawley (WKY-H), and Charles River (WKY-CR) were observed in the open-field test (OFT) and the forced-swim test (FST), and subsequently exposed to ulcerogenic water-restraint stress. There were no differences between vendor stocks in the FST, but WKY-CR rats were significantly more immobile in the OFT as compared to WKY-T and a Wistar control group. WKY-CR and WKY-H rats revealed significantly more ulcers as compared to WKY-T and Wistar rats. The WKY inbreeding programs at Charles River and Harlan, as compared to the outbreeding practice at Taconic may contribute to these vendor differences. These data indicate that WKY rat sublines from different vendors represent an important source of variability when comparing studies of stress reactivity using WKY rats.