Figure 3.

The nocturnal 5-HT content and release are elevated throughout the night period in the absence of melatonin production. (A) ActD treatment of night pineal gland effectively and specifically abolishes NAT transcription. Saline and ActD (1 mg/kg, i.p.) injected rats were killed 8 h after the injection at 8 p.m. during the day and at 8:30 a.m. at night, analyzed for their pineal RNA content of NAT, TPH, aromatic amino acid decarboxylase (not shown), hydroxyindole-O-methyltransferase (not shown), and glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Each lane contains 10% of total RNA pooled from five treated glands. (B) ActD treatment of night pineals resulted in increased 5-HT production and reduced melatonin formation. ActD-treated rats were killed identically as in A, and their pineals were analyzed for 5-HT and melatonin content by using HPLC-FD. Each bar represents the mean of five individual rats. (C) 5-HT release remains increased over the night period after i.p. ActD injection. ActD (1 mg/kg) was injected into adult rat 30 min before the lights were off. Open symbols represent profiles of 5-HT (○, Upper) and melatonin (▵, Lower) secretion before the ActD treatment, and the solid symbols indicate the release patterns of 5-HT (●, Upper) and melatonin (▴, Lower) after the ActD injection. 5-HT levels (Upper) are calculated as the percentage of basal daytime production (n = 4). (D) 5-HT secretion remains elevated after direct ActD treatment of the pineal in vivo. ActD (100 μg/ml) is infused through a microdialysis probe directly into the pineal from 11 p.m. to 1 p.m. 5-HT and melatonin release was monitored by using on-line microdialysis with HPLC-FD before (○ for 5 HT, Upper; ▵ for melatonin, Lower), and during (● for 5-HT, Upper; ▴ for melatonin, Lower) the drug treatments. Identical results were obtained with all of the animals treated (n = 5).