Effect of clonidine on growth and plasma somatomedin C levels of young rats

To study the effects of clonidine on growth and plasma somatomedin C (SmC) levels, 42 male Wistar rats aged 28 days and weighing 75 to 105 g were given clonidine (1.5 micrograms/ml in drinking water), or filtered water alone and were weighed weekly. After 0, 4 and 8 weeks, the animals were sacrificed under ether anesthesia, their length was measured and blood was collected by cardiac puncture for measurement of SmC concentration. Growth and the weight/length ratio were lower, and plasma SmC levels (mean +/- SEM) were greater in the treated groups after 4 (616 +/- 44.7 vs 433.2 +/- 39.38 ng/ml, P less than 0.01) and 8 (595.2 +/- 28.3 vs 412.66 +/- 39.01 ng/ml, P less than 0.01) weeks of treatment, suggesting that clonidine treatment increased growth hormone secretion. In other experiments, treated animals showed increased food intake only during the first week of treatment and decreased epididymal fat weight after 3 weeks (1.412 +/- 0.0536 vs 1.6 +/- 0.1336 mg/100 g body weight, P less than 0.01). The results suggest that clonidine acts at the level of the central nervous system involving transitory modulation of food intake, as well as on the regulation of energy metabolism.