Increased N‐Acetylserotonin and Melatonin Formation Induced by d‐Amphetamine in Rat Pineal Gland Organ Culture via a β‐Adrenergic Receptor Mechanism

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Abstract
Dextro‐amphetamine (10–5M) added to the medium of rat pineal glands in organ culture produces an eightfold increase of radiolabeled N‐acetylserotonin and melatonin when tryptophan or serotonin are used as labeled precursors. In concentration of 10–4M d‐amphetamine causes a decreased formation of 5‐hydroxyindoleacetic acid from tryptophan and serotonin. Addition of d‐amphetamine to pineal glands also resulted in an increase of N‐acetyltransferase activity as compared with untreated glands. The effect of d‐amphetamine and noradrenaline was blocked by propranolol, a β‐adrenergic blocking agent but not by the α‐adrenergic blocking agent phentolamine. In cervical ganglionectomized rats the addition of d‐amphetamine to the culture medium did not produce an increase in N‐acetylserotonin production. Conversely noradrenaline added to the medium gave a high formation of N‐acetylserotonin. This indicates that the major effects of d‐amphetamine on pineal N‐acetyl‐transferase activity are mediated by noradrenaline.