Clonidine-induced alterations in feeding in deprived rats

The ability of systemically administered clonidine to alter 3-hr food consumption in 21-hr food deprived male rats was investigated. Clonidine (12.5, 25, 50, and 100 mcg/kg) administered IP 10-min prior to feeding failed to affect this behavior. However, a dose of 200 mcg/kg significantly decreased feeding. This same dose when given for 7 consecutive days resulted in decreased feeding but only during the initial four sessions. This same dosage and treatment schedule also resulted in a reduction in locomotor activity, but only on the initial day of dosing. A comparison of these two results suggests that part of the depression in feeding resulted from a general decrease in activity. The acute effect of the 200 mcg/kg dose of clonidine was enhanced by morphine pretreatment, unaffected by treatment with naloxone or phenoxybenzamine and antagonized by treatment with tolazoline. This latter data suggests that the depressant action of clonidine on feeding results primarily from an action on noradrenergic systems, and in particular alpha 2 receptors.