The effects of the alpha 2-agonist clonidine (CLO), the serotonin (5-HT) precursor 5-hydroxy-L-tryptophan (5-HTP), the 5-HT2/histamine (H1) antagonist cyproheptadine (CYPRO), the muscarinic cholinergic antagonist atropine (ATR), and an affinity-purified polyclonal anti-rat growth hormone-releasing