EFFECT OF METHYLPHENIDATE ON SPONTANEOUS ACTIVITY, FOOD INTAKE, AND COLD TOLERANCE OF PROPYLTHIOURACIL-TREATED RATS

Abstract

Dietary administration of methylphenidate to rats increases locomotor activity (tilt cage method) roughly in proportion to the logarithm of the dose ingested. The results suggest that a dose of 62 mg methylphenidate/kg body wt. per day increases activity level by 50%. At higher dose levels, a tolerance appears to develop and is characterized by high initial levels of activity (days 1 to 3) followed by reduction of activity to a new stable level (days 4 to 6). Methylphenidate increases activity level and decreases food intake and body weight of both hypothyroid (propylthiouracil-treated) and control rats subjected to ambient temperatures of 10, 15, 20, and 28 °C. It fails to increase the tolerance of hypothyroid rats either to chronic (10 and 15 °C) or to acute (5 °C) cold exposure.