Paradoxical Hormonal and Behavioral Responses to Hypothyroid and Hyperthyroid States in the Wistar–Kyoto Rat

Abstract

The Wistar-Kyoto (WKY) rat is the normotensive progenitor strain of the spontaneously hypertensive rat (SHR) that Okamoto and Aoki (1963) isolated from a strain of Wistar rats, the Wistar/Hokkaido rat. The WKY rat differs from the SHR not only with respect to resting blood pressure but it also displays smaller stress-induced increases in plasma cathecholamines (McCarty et al. 1987), heart rate, and blood pressure (LeDoux et al. 1982;Rettig et al. 1986;Knardahl and Hendley 1990). In contrast, WKYs show larger endocrine and behavioral responses to stress compared not only to SHRs but also to Wistars and several other rat strains (Pare and Redei 1995). Because most current animal models of depression are based on stress-induced behavioral deficits, it is no surprise that the WKY rat, which is endogenously hyperresponsive to stress, also shows endogenous depressive behavior (Pare and Redei 1995).A large body of literature from different laboratories supports these findings. WKY rats show increased depressive and anxious behavior in a number of tests as compared to several inbred and outbred rat strains (Pare 1989;Pare 1992a;Tizabi et al. 1992;Castanon et al.

Orally administered whole egg demonstrates antidepressant-like effects in the forced swimming test on rats

“…In the OFT, WKY rats displayed less line crossing (in terms of the number of times crossed) compared with WIS rats, meaning that WKY rats are hypoactive, in agreement with the findings of previous studies (14,29,32). In addition, in the FST, WKY rats displayed higher immobility -the index of a depressive-like state -compared with WIS rats.…”

“…They display longer immobility in the FST compared with outbred Sprague-Dawley rats and other inbred strains (14,(27)(28)(29)(30); however, chronic antidepressant treatment has been found to alleviate this depression-like behaviour in the FST (31). In addition, WKY rats showed hypoactivity in the openfield test (OFT) compared with WIS rats (14,29,32). This abnormal behaviour in WKY rats corresponds with the findings of a study using human subjects, in which depressed patients exhibited hypoactivity compared with healthy subjects (33).…”

Neuronal 3′,3,5-Triiodothyronine (T3) Uptake and Behavioral Phenotype of Mice Deficient inMct8, the Neuronal T3Transporter Mutated in Allan–Herndon–Dudley Syndrome

“…Rather, some of our results pointed to increased T 3 signaling resulting in enhanced pain perception (Edmondson et al, 1990;Bruno et al, 2005Bruno et al, , 2006. However, in contrast to hy- perthyroid rodents (Redei et al, 2001;Sala-Roca et al, 2002), there was no indication for hyperactivity in Mct8 Ϫ/y mice as shown by unaltered locomotion. We thus speculate that neurons in specific brain regions with direct access to the increased circulating T 3 levels may be exposed to enhanced T 3 signaling, if their T 3 uptake is independent of Mct8.…”

Modulation of adult hippocampal neurogenesis by thyroid hormones: implications in depressive-like behavior

“…In a previous study, 65 severe hypothyroidism was also found to increase immobility in the forced swimming paradigm compared to euthyroid rats, an effect that was prevented by high doses of T4. In other studies, rat strain differences in thyroidal status seem to explain different behavior in the forced swimming test, 66 and TH treatment ameliorates the cognitive and mood impairments caused by alcohol exposure. 67 In our present study, chronic TH treatment restored the depressive-like behavior in parallel with normalization of proliferation in the hippocampus.…”