A theory is presented that explains the evolution of the pinealocyte from the common ancestral photoreceptor of both the pinealocyte and retinal photoreceptor. Central to the hypothesis is the previously unrecognized conflict between the two chemistries that define these cells-melatonin synthesis and retinoid recycling. At the core of the conflict is the formation of adducts composed of two mol...

Mammalian circadian rhythms are controlled by a master pacemaker located in the suprachiasmatic nuclei (SCN), which is synchronized to the environment by photic and nonphotic stimuli. One of the main functions of the SCN is to regulate peripheral oscillators to set temporal variations in the homeostatic control of physiology and metabolism. In this sense, the SCN coordinate the activity/rest an...

Melatonin production in the pineal gland is high at night and low during the day. This rhythm reflects circadian changes in the activity of serotonin N-acetyltransferase [arylalkylamine N-acetyltransferase (AA-NAT); EC 2.3.1.87], the penultimate enzyme in melatonin synthesis. The rhythm is generated by an endogenous circadian clock. In the chick, a clock is located in the pinealocyte, which als...

Serotonin N-acetyltransferase (arylalkylamine N-ace-tyltransferase (AANAT)) catalyzes the reaction of serotonin (or tryptamine) with acetyl-CoA to form N-acetylserotonin (or N-acetyltryptamine) and is responsible for the melatonin circadian rhythm in vertebrates. This study evaluates a series of indoleamine analogs as alternate substrates of AANAT. 3-Indolepropylamine and 3-indolebutylamine wer...

In mammals, light information received by the eyes is transmitted to the pineal gland via the circadian pacemaker, i.e., the suprachiasmatic nucleus (SCN). Melatonin secreted by the pineal gland at night decodes night length and regulates seasonal physiology and behavior. Melatonin regulates the expression of the β-subunit of thyroid-stimulating hormone (TSH; Tshb) in the pars tuberalis (PT) of...

The pineal organ (or pineal) of a teleost fish, the pike, contains typical (cone-like) and modified photoreceptor cells. Both are involved in indole metabolism, including melatonin production. How photoperiod controls melatonin biosynthesis in organs containing mainly photoreceptor cells, remains unclarified. To tackle this question we have used cultured pike pineal organs to investigate the va...

OBJECTIVE The study examined the effect of intravenous administration of bacterial endotoxin-lipopolysaccharide (LPS) -on the nocturnal secretion of melatonin and on the expression of enzymes of the melatonin biosynthetic pathway in the pineal gland of ewes, taking into account two different photoperiodic conditions: short-night (SN; n = 12) and long-night (LN; n = 12). METHODS In both experi...

Influence of the season of hatch on the functional characteristics of the pineal gland was examined in neonatal Hi-Line male chickens. The pineal glands from 2-day-old birds hatched in summer and winter, and kept from the day of hatch in artificial lighting conditions (12L:12D), were isolated under dim red light in the middle of the day or night. The pineal glands were analyzed to characterize ...

Melatonin has been suggested to play a role in fish osmoregulation, and in salmonids has been related to the timing of adaptive mechanisms during smolting. It has been described that acclimation to different environmental salinities alters levels of circulating melatonin in a number of fish species, including rainbow trout. However, nothing is known regarding salinity effects on melatonin synth...