Effects of age and drugs on food and fluid intake.

In young adults rats (5-month-old) d-amphetamine (2 mg/kg/d), administered on a long-term basis via drinking water, caused a moderate reduction in the intake of nutriments, which in part normalized within three weeks. Self-administration of a daily dose of 20 mg per kg diazepam over a period of 26 days led neither to hypodipsia nor to anorexia. Pentylenetetrazol (70 mg/kg/d) primarily produced a hypodipsia. The three drugs did not influence body weight. In 27-month-old rats d-amphetamine and pentylenetetrazol had the same qualitative effects. Intake of nutriments and the development of body weight were influenced more strongly than in young rats. Diazepam also had a marked effect in old animals. Nootropics (piracetam, pyrithinol, hydergin, centrophenoxin, aniracetam) had no effects on the parameters observed. When the agents were given in combination in both age groups the nootropic piracetam (230 mg/kg/d) weakened the effects induced by d-amphetamine, pentylenetetrazol or diazepam alone. The benzodiazepine, however, enhanced the loss of body weight and fluid intake in old rats caused by the stimulant or analeptic, whereas food intake remained unaffected. The results support the hypothesis that an organism's adaptivity to external and internal stimuli is reduced in later life. The behavior of young and old rats in the open field was not affected by any drug medication.