Failure of TRH and ORG 2766 hexapeptide to counteract alcoholic inebriation in man

Alcohol pharmacodynamics in young-elderly adults contrasted with young and middle-aged subjects

Effects of aging on ethyl alcohol (EtOH) pharmacodynamics were examined over progressive dosing schedules (0.4, 0.6, 0.8, 1.0 g/kg) in groups of young (25.0 +/- 2.9 years), middle-aged (41.1 +/- 6.6 years), and young-elderly adults (60.9 +/- 2.6 years) using three computerized cognitive-neuromotor tasks: digit-symbol substitution (DSS), keypad reaction time (KRT), and subcritical tracking (SCT). Hysteresis curves of performance impairment (adjusted for pre-drug baseline) as a function of blood alcohol concentration (BAC) were examined for time-course effects, and regression analyses were performed to assess the contribution of age beyond that accounted for by BAC. Results reflected differences in the patterning but not magnitude of impairment for elderly subjects, with earlier decrements and more rapid acute tolerance observed for DSS, in conjunction with less pharmacodynamic sensitivity for SCT. Regression analyses furthermore indicated that age and impairment were negatively related, arguing against synergistic intoxication effects as a function of aging. Analyses specifically comparing performance at baseline versus legally intoxicating BACs (> 1.0 mg/ml) likewise reflected a lack of interactive effects involving the elderly. Elderly subjects nevertheless exhibited significantly lower baseline performance for DSS and KRT than young subjects and achieved higher BACs with equivalent doses. These latter findings support the exercise of caution by elderly individuals consuming EtOH prior to engaging in neuromotor pursuits such as driving.

The subchronic effects of the TRH analog TA-0910 and bromocriptine on alcohol preference in alcohol-preferring rats: development of tolerance and cross-tolerance

In a previous study, we showed that a single injection of the thyrotropin-releasing hormone analog TA-0910 dose-dependently reduced alcohol intake in alcohol-preferring (P) rats and increased their water intake over a 24-hr period. In the present study, the effects of seven consecutive, once-daily injections of TA-0910 (0.75 mg/kg, ip) on alcohol preference were determined. P rats developed tolerance to the attenuating effects of TA-0910 on alcohol intake within 3-5 days. Following the development of tolerance to TA-0910, rats were injected with the dopamine agonist bromocriptine (0.5 mg/kg, sc). In the presence of tolerance to TA-0910, the attenuating effect of bromocriptine on alcohol intake was reduced. When rats were made tolerant to the attenuating effects of bromocriptine, they exhibited tolerance to the attenuating effects of TA-0910. These findings indicate that tolerance to the effects of TA-0910 on alcohol intake occurs and suggest dopamine involvement in the mechanism of action of TA-0910 in reducing alcohol intake in P rats.

Attenuation of alcohol preference in alcohol-preferring rats by a novel TRH analogue, TA-0910

Experiments were performed to characterize the acute effect of different doses of a novel thyrotropin-releasing hormone (TRH) analogue (TA-0910) on ethanol intake in rats. Selectively bred alcohol-preferring (P) rats received a single intraperitoneal injection of normal saline or 0.083, 0.25 and 0.75 mg/kg of TA-0910 at 9:30 AM, and their consumption of ethanol, water, and food was measured for 24 hr. TA-0910 dose-dependently attenuated ethanol intake and commensurately increased water consumption. Only the highest dose of TA-0910 increased the total caloric intake. TA-0910 did not affect the pharmacokinetics of ethanol. These findings indicate involvement of TRH systems in ethanol preference and suggest that centrally acting TRH analogues may be therapeutic in the treatment of alcoholism.

Behavioral and endocrine interactions between thyrotropin-releasing hormone and ethanol in normal human subjects

Thyrotropin-releasing hormone (TRH) has been shown to antagonize the depressant effects of ethanol in animals, but conflicting findings have been reported in humans. To test whether TRH counteracts any of a variety of ethanol-sensitive behavioral measures in normal human subjects and for an effect of ethanol on TRH-induced thyrotropin (TSH) and prolactin (PRL) response, we administered TRH (500 micrograms) or placebo over 1 min intravenously, 30 min after subjects had ingested 0.8 g/kg of ethanol or a placebo drink. Blood samples for TSH and PRL were drawn prior to and 15 and 30 min after injection. Eight male subjects were studied in a balanced, crossover design with each subject receiving placebo-placebo, TRH-placebo, placebo-ethanol, and TRH-ethanol. Whereas ethanol had significant and expected effects on subjective measures, memory, disinhibition, reaction time and time perception, TRH failed to counteract any ethanol effect, except for a small effect in one memory task. Similarly, no effect of ethanol on TRH-induced TSH or PRL response was found. Though the behavioral findings could be interpreted to indicate that TRH does not alter ethanol sensitive behaviors in humans it will be necessary to utilize higher dosages of TRH and/or TRH analogues before firmly drawing this conclusion.

Thyrotropin-releasing hormone antagonism of ethanol inebriation

The effect of ethanol [1 g/kg per orally (p.o.) during 1 hr] after thyrotropin-releasing hormone (TRH) pretreatment (five doses of 20 mg p.o. during 30 hr preceding ethanol intake) was studied in a placebo-controlled, double-blind design in 11 healthy subjects. Computerized reaction tests measuring errors and reaction time, as well as clinical testing and a self evaluation (modified Osgood test) were performed before, 75, 150, and 225 min after ethanol intake. TRH treatment did not influence blood ethanol concentrations. The effect of ethanol to produce errors was substantially reduced in all three reaction tests after TRH treatment compared to placebo treatment. The reaction times were slightly increased in simple and four choice reaction tests and up to 20% increased in a complex test in the TRH-ethanol situation compared to the placebo-ethanol situation. The effects caused by ethanol were also significantly reduced in three clinical tests and in two subjective tests of inebriation by TRH treatment compared to placebo treatment. In conclusion the study demonstrated that several acute effects of ethanol intake in humans were reduced by TRH pretreatment which did not interfere with the blood ethanol concentration versus time curve.

Failure of amantadine and bromocriptine to counteract alcoholic inebriation in man

Oral amantadine 100 mg and bromocriptine 2.5 + 2.5 mg, alone and in combination with ethanol (1 g/kg), were investigated in two placebo-controlled, double-blind and cross-over trials. In the first trial the psychomotor effects of amantadine and bromocriptine were compared to those of placebo, and in the second trial ethanol was added to the treatment. Bromocriptine lowered serum prolactin levels, thus confirming its absorption. Amantadine and bromocriptine alone had no psychomotor effects but unpleasant sensations, nausea and dizziness were reported after bromocriptine. Ethanol impaired performance in terms of impaired coordinative and reactive skills, lowered tapping speed, prolonged critical flicker interval and reduced gaze nystagmus angle (P less than 0.05 to 0.001; two-way ANOVA). Subjectively, ethanol induced mental slowness, clumsiness and impairment of performance (P less than 0.05 to 0.001). Amantadine and bromocriptine failed to counteract any of these ethanol-induced changes. It is concluded that in man, an acute dopaminergic activation by amantadine or bromocriptine does not significantly modify the psychomotor effects of ethanol.