The nocturnal rise of melatonin in serum of humans is the result of endogenously released norepinephrine (NE) acting upon beta-adrenergic receptors of the pineal gland. As there is much interest in the possibility of there being changes in the function of beta-receptors in depressed patients, the nocturnal rise of melatonin was measured in depressives and healthy control subjects. In one study, multiple serum samples were taken between 4.30 p.m. to 7.30 a.m. in seven male depressed patients with melancholia and five healthy male control subjects. The melancholic patients had a significantly reduced nocturnal elevation of melatonin. In a separate study, serum samples were taken at 8 a.m. and 11 p.m. in melancholic depressives, non-melancholic depressives and healthy control subjects. The melancholic patients had a significantly lower concentration of melatonin at 11 p.m., but not at 9 a.m., than that measured in either the control subjects or the non-melancholic depressed patients. These results are similar to those found recently by several other groups of investigators. Further research is indicated to elucidate mechanism(s) responsible for this phenomenon.
