Behavioural responses to elevated plus-maze and defensive burying testing: effects on subsequent ethanol intake and effect of ethanol on retention of the burying response.

Based upon repeated observations of a relationship between defensive burying (DB), ethanol intake and stress ulcer susceptibility, and recurring questions regarding what DB behaviour reflects, two experiments were performed. Experiment 1 showed that prod shock exposure per se reduced subsequent ethanol intake, as did access to burying material. In rats without burying material in the conditioning phase, subsequent access to ethanol resulted in reduced DB activity in the retest, pointing to some interference by ethanol on latent learning. Experiment 2 showed that there were no effects of anxiety as measured in the elevated plus-maze (EPM) on saccharin or ethanol intake. Behaviours in the EPM and DB test did not correlate. Rats entering the open arm on first entry into the EPM drank and preferred more ethanol than those choosing the closed arm. Saccharin intake was negatively related to burying latency, and positively related to initial ethanol intake. In conclusion, it is still questionable whether the DB test is measuring anxiety, but exposure to the test or performance of the DB activity appears to cause modifications, psychologically and perhaps physiologically, in rats. Ethanol intake may under certain conditions interfere with the acquisition of a defensive response. The testing of DB behaviour may be useful in studying drug effects on latent learning of prepared responses.

Relating acoustic startle reactivity and plasticity to alcohol consumption in male Wistar rats.

The purpose of this study was to investigate the relationship between the startle response and ethanol. Aspects of the startle response, including initial and average startle, habituation, and prepulse inhibition (PPI) were studied. The startle response was measured to detect potential predictors of voluntary ethanol consumption and to observe whether ethanol ingestion would affect startle in subsequent tests. Rats were tested three times in a standard startle chamber. After the initial startle test, rats categorized as showing high or low PPI were allocated in a balanced way to a free-choice ethanol-water regime or to the water-regime control group. At the end of the ethanol period (lasting for 16 days, including access to ethanol for 10 days), the rats were tested again in the startle chamber 24 h after ethanol removal. After 5 weeks of ethanol abstinence, rats were exposed to a final startle test. The response to the first 120-dB stimulus showed an inverted U-shaped, curvilinear relationship to later ethanol consumption. Startle habituation appeared to have predictive value regarding ethanol consumption, with rats showing the most efficient habituation drinking most. Data showed no relationship between PPI and ethanol intake. Rats given access to ethanol showed greater habituation in the post-ethanol test than did the water controls. After 5 weeks of abstinence, low ethanol-consuming rats showed lower startle responses to the first 120-dB stimulus than did high ethanol-consuming rats. The present data suggest a two-way relationship between startle response characteristics and alcohol.

Defensive burying and stress gastric erosions in alcohol-preferring AA and alcohol-avoiding ANA rats.

The aim of this study was to investigate differences in shock-prod induced defensive burying and vulnerability to stress gastric ulcerations in two lines of rats selectively bred for alcohol-preference (AA) and alcohol-avoidance (ANA). Alcohol-naïve animals from the AA and ANA lines were tested in the shock-prod defensive burying test and (after an interval of approximately 2 months) in a 75 min water-immersion stress ulceration-inducing procedure. The AA rats showed longer latencies (327.5 s) for burying after shock-prod compared with the ANA animals (128.0 s). Furthermore, the ANA rats developed more stomach ulcerations (12.35 mm) compared with the AA rats (1.30 mm). Animals also differed based on whether they had been tested for defensive burying or not, with the tested animals showing less ulceration development than the control group. We hypothesize that the difference between AA and ANA rats is controlled by some common biochemical mechanism. One likely candidate is the dopaminergic system, which is involved in both the motivational effects of alcohol, as well as anxiety and stomach ulceration. In addition, the alcohol-preferring strain seems to be less fearful and generally may be less sensitive to aversive stimuli, be it shock prod, the aversive properties of alcohol, or water immersion stress.

Voluntary alcohol consumption in rats: relationships to defensive burying and stress gastric erosions.

Rats with short latency to initiate burying in the defensive burying test later showed lower alcohol consumption in an ethanol preference test than animals with medium and long latencies. These short-latency, or "active" animals also had a slight tendency to develop more ulceration than the "passive" animals. In addition, there was a negative correlation between voluntary alcohol consumption and the amount of stress-induced stomach ulcers. Many researchers view active burying behaviour as an index of anxiety. Our results suggest the opposite: that passivity, rather than active burying, may be an index of anxiety and that such passive animals subsequently ingest more ethanol. The tendency of active animals to develop more ulcers than passive animals is in contradiction to earlier studies. Our interpretation is that the long-latency animals experience more fear in the defensive burying test, with increased alcohol consumption as a result. This increase in alcohol consumption gives a cumulative cytoprotective effect against stomach ulcers.

Restraint stress in biomedical research: an update.

Since the publication of our initial review of restraint stress in 1986, much work has continued with this technique, either as a tool for the investigation of other pharmacological, physiological, or pathologic phenomena or with restraint stress itself serving as the object of the study. As we noted in 1986, the major use of restraint has been for the induction of stress responses in animals and, more specifically, for the investigation of drug effects, particularly as they affect typical stress-related pathology--gastrointestinal, neuroendocrine, and immunological agents have been extensively studied. In compiling this update on restraint stress and its effects, we noted an increasing emphasis on central nervous system mechanisms in peripheral disease, especially gastrointestinal disease. In particular, many CNS-active agents have been tested for their effects on gastric and duodenal lesion formation and gastric secretion, including antidepressants, antipsychotics, anxiolytics, noradrenergic, serotonergic, dopaminergic, and peptidergic compounds. Some of these agents are especially active in the gastrointestinal tract even when administered centrally, further solidifying the concept of a brain-gut axis. The present update includes studies of: methods and procedures, pre-restraint manipulations, post-restraint/healing effects, and drug effects. In addition, a current bibliography of reports that have employed restraint is included.