Adenosine analogs elevate N-acetylserotonin and melatonin in rat pineal gland.

Adenosine, S-adenosyl-L-homocysteine, adenosine analogs such as 5'-N-ethylcarboxamidoadenosine and mioflazine, a nucleoside transport inhibitor, injected intraperitoneally at 09.00 h during the light period increased melatonin levels in the pineal gland of the rat. The largest increase occurred with 1 mg/kg 5'-N-ethylcarboxamidoadenosine. A representative time-response curve with 5'-N-ethylcarboxamidoadenosine (1 mg/kg) showed a maximal peak of N-acetylserotonin and melatonin 2 and 4 h after injection, respectively. These results are discussed in relation with the possible modulation through A2 receptors of melatonin synthesis in the pineal gland.