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Maintain Your Subjective Experience

We recently demonstrated that family history positive (FHP) subjects expose themselves to higher alcohol levels than do FH negative (FHN) controls when they are asked to produce their usually preferred level of alcohol effects during computer-assisted self-infusion of ethanol (CASE) experiments. The CASE procedure implies that each time the subject pushes a button to request more alcohol, ethanol is infused i.v. to linearly increase blood alcohol concentration (BAC) by 7.5 mg% within 2.5 minutes, during which time no further alcohol requests can be made. After 2.5 minutes, the “request alcohol” button is reactivated, and redistribution of ethanol is utilized to make BAC fall by 1 mg% per minute until the subject requests another “drink”. Therefore, BAC never is constant, but either rises or falls at rates which are considerably higher than those occurring after oral administration. This means that subjects quickly can bring BAC into the range they prefer, compensating for BACs they consider too low (by requesting more often) or too high (by refraining from further alcohol requests for a while) within one experimental session. On the other hand, these dynamics make it difficult for the subjects to keep their brain alcohol exposure at a stable level over prolonged periods of time. Since subjects are blind against their current BAC and have no external cues helping them to estimate how much alcohol or volume they already self-administered, they can base their decisions about when to request more alcohol only on the subjective alcohol effects they perceive. 

Visual analysis of time-BAC- profiles in 21 subjects revealed that 8 FHN and 4 FHP subjects nevertheless produced a remarkably stable plateau of BAC over a period of at least 40 minutes. During that time, BAC oscillated in a saw-tooth shape by little more than the inevitable minimal variation of 7.5 mg%, without an upward or downward trend. Of the 9 subjects whose time-BAC profiles did not show such a plateau, 1 was FHN and 8 were FHP. Plateaus occurred significantly more often in FHN than FHP subjects (Fisher’s exact test, p<0.05). If such a plateau occurs, we assume that it provides a more reliable reflection of the subject’s preferred level of alcohol exposure than can be drawn from experiments where self-exposure is inconstant. 

We conclude that, although our experimental setup discourages stable levels of BAC, a subgroup of subjects spontaneously produces constant plateaus of BAC with only minimal variation, without being instructed to do so. Producing constant plateaus during CASE experiments is only possible if subjects can subtly perceive current alcohol effects, which is their only support to decide whether or when to request more alcohol. Therefore, the observation that FHP less often produce plateaus suggests that their apperception of alcohol effects is worse than in FHN subjects, which might explain why they tend to drink more in real life. 

Laufzeit:

Förderung: Klinikeigene Mittel

Projektmitarbeiter: Cand. med. Toni Blümke, Cand. med. Maik Spreer, Dr. Inge Mick

externe Kooperationspartner: Prof. O’Connor, University of Indiana at Indianapolis, USA