In the elevated plus-maze test of anxiety the scores of control animals remain stable over repeated tests. However, a single prior exposure to the plus-maze renders an animal insensitive to the anxiolytic effects of chlordiazepoxide. This phenomenon of "one-trial tolerance" persisted even when the two trials were separated by as much as 2 weeks. It has previously been shown that the drug state of the animal on trial 1 is not important to the development of the phenomenon, but one-trial tolerance did not develop if a very high dose (75 mg/kg) of chlordiazepoxide was given on trial 1; it is suggested that this is due to the amnesic effects of the drug. The learning on trial 1 was not specific to a particular plus-maze and tolerance could be observed even when the maze on trial 1 was made from different material. The crucial experience on trial 1 was experience of an open arm of the maze. Whereas tolerance could be obtained as a result of a previous plus-maze experience, there was no evidence of an anxiogenic withdrawal response when rats were tested the following day undrugged. The phenomenon of one-trial tolerance is explained within our recently proposed two-factor theory of benzodiazepine dependence; it is suggested that one-trial tolerance provides a method for studying the mechanism underlying the development of tolerance to anxiolytic effects, independently from the mechanism underlying the development of withdrawal responses.

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Rats given one or two 5-min trials in the elevated plus-maze had plasma corticosterone concentrations significantly higher than the home cage control group and there was no sign of habituation in the group given two trials. In rats given two plus-maze trials the corticosterone responses were significantly higher in the group given 10-min rather than 5-min trials. A previous experience of cat odour (1 week earlier) has no effect on the plasma corticosterone response, but did have an anxiogenic effect that could be detected by a decrease in the percentage of time spent on the open arms of the plus-maze. The results are discussed with reference to the nature of anxiety generated by trials 1 and 2 and by the trial duration in the plus-maze, and with respect to dissociation between behavioural and endocrinological measures.

1st, 2nd, 3rd and 5th year medical students completed a questionnaire with 35 questions relating to diet, general health, exercise, smoking and drinking. Based on reported 'typical weekly intake' one-third of male non-Asian students in years 1-3, and 59% in year 5 were drinking above safe limits. 12-26% of non-Asian female students were drinking above safe limits. In all years most Asian students were drinking within safe limits. Non-Asians smoked more than Asians and males smoked more than females. A group of non-Asian male students with alcohol intake for the previous week > 35 units was compared with a group of safe drinkers (<25 > 0 units/week). Significantly more of the former group drank > 10 units per occasion, had been hurt as a result of someone's drinking, had caused physical harm and drank at lunch. Although 65% were aware their level of drinking was dangerous, only 7.5% wanted advice on safe drinking and only 5% wanted to drink less. The dangerous level drinkers ate less fruit and smoked more cigarettes than those drinking safely, but there were no other significant differences and there was no evidence for impaired academic performance.