Hangover hyperthermia in rats: relation to tolerance and external stimuli

Abstract

The recent finding of rebound hyperthermia in rats on the day after a single IP injection or oral intubation of ethanol was confirmed. In our studies, body temperature measured by rectal probe was significantly decreased for 8 h after 2.5 g/kg ethanol IP and was then significantly elevated 16-24 h after injection; increased vocalization during handling at 24 h was also found. However, rats isolated in a sound-attenuation chamber with remote temperature measurement showed no hyperthermia even though they were hypothermic during intoxication. The results do not support the hypothesis that rebound hyperthermia was caused by either a disruption of circadian rhythms, or by a mild abstinence syndrome alone. Instead, it appears that external stimuli, perhaps related to stress or associated with ethanol administration, are necessary on the day after a moderate dose of ethanol to produce the hyperthermia. Like hangover in humans, hyperthermia was reduced in rats made tolerant to ethanol: both the hypothermia and the rebound hyperthermia were significantly lower on the day after the 12th alternate-day ethanol injection than after the first injection. The aftereffects in rats of acute intoxication are, by definition, hangover signs, and they resemble hangover in humans in several ways, but their relevance as an animal model of hangover remains to be determined.

Age Differences in the Expression of Acute and Chronic Tolerance to Ethanol in Male and Female Rats

“…Since animals in this study were given this habituation session 22 hr after their last injection, this motor suppression likely reflects withdrawal-induced hypomotility, which has been observed in rats up to 48 hr since their last EtOH administration (Macey et al, 1996). Decreases in motor activity join other measures, including convulsions, hypothermia, increased anxiety, hyperactivity, and rebound hyperthermia as being indicative of the withdrawal that occurs when chronic exposure to EtOH is terminated (Finn and Crabbe, 1997; Sinclair and Taira, 1988; Rasmussen et al, 2001; see Kliethermes, for review, 2005). There is ample evidence that adult rats show notable withdrawal after chronic EtOH exposure (File, 1991; 1993; 1994); however, withdrawal following chronic EtOH exposure during adolescence has been little investigated.…”

Acoustic Startle Reactivity During Acute Alcohol Withdrawal in Rats That Differ in Genetic Predisposition Toward Alcohol Drinking: Effect of Stimulus Characteristics

“…Relatively few objective measures of alcohol withdrawal have been shown to be useful in detecting mild signs of alcohol withdrawal that occur after acute alcohol exposure in alcohol-naive rats (Gallaher and Egner, 1987;Holloway et al, 1993;Sinclair and Gustafsson, 1987;Sinclair and Taira, 1988). Our prior work in alcohol-naive rats demonstrated that acoustic startle reactivity to a tone stimulus is a reliable and quantifiable index of mild alcohol withdrawal that occurs after a single alcohol exposure in rats selectively bred for high or low alcohol intake (Chester et al, 2003).…”

Further Evidence of an Inverse Genetic Relationship Between Innate Differences in Alcohol Preference and Alcohol Withdrawal Magnitude in Multiple Selectively Bred Rat Lines

“…Mild withdrawal signs and symptoms are seen following acute alcohol exposure in both humans and animals, and, in humans, these signs are often referred to as "hangover" (Gallaher and Egner, 1987;Holloway et al, 1993;Swift and Davidson, 1998). There is no consensus in the rodent literature regarding the use of the terms "hangover" or "alcohol withdrawal" to describe the signs and symptoms that occur following acute alcohol exposure, and both terms have been used (Chester et al, 2002;Gallaher and Egner, 1987;Holloway et al, 1993;Metten et al, 1998;Sinclair and Taira, 1988). In our work, we have chosen to use the term "alco-hol withdrawal" to describe the behavioral and physiologic changes that occur following acute alcohol exposure at times when blood alcohol levels are falling and after blood alcohol levels have reached zero.…”