A diurnal serotonin cycle in the pineal body of Japanese quail: photoperiod phasing and the effect of superior cervical ganglionectomy

Diurnal and circadian variations in indole contents in the goose pineal gland

The diurnal and circadian profiles of pineal indoles, except melatonin, are poorly characterized in birds. Moreover, there are no data on the effect of sudden changes in the light-dark cycle on these profiles. Therefore, we investigated the diurnal (Experiment I) and circadian variation (Experiment II) of nine pineal indoles (tryptophan, 5-hydroxytryptophan, serotonin, N-acetylserotonin, melatonin, 5-hydroxyindole acetic acid, 5-methoxytryptophol, 5-methoxyindole acetic acid, 5-methoxytryptamine) in geese, as well as the changes in the profiles of these substances in geese subjected to a reversed light-dark cycle (Experiment III). For the first 12 weeks of life, all geese were kept under a diurnal cycle of 12 h of light and 12 h of darkness (12L:12D). In Experiment I (n = 48), they were kept under these conditions for another 14 days before being sacrificed at 2-h intervals for sampling of the pineal glands. In Experiment II, the geese (n = 48) were divided into three groups (12L:12D, 24L:0D, 0L:24D) for 10 days before sampling at 6-h intervals. In Experiment III, 24 geese were exposed to a reversed light-dark cycle before sampling at 14:00 and 02:00 on the first, second and third days after light-dark cycle reversal. To determine the content of the indoles in the goose pineals, HPLC with fluorescence detection was used. We found that, with the exception of tryptophan, all the investigated indoles showed statistically significant diurnal variation. When geese were kept in constant darkness, most of the indoles continued to show this variation, but when geese were kept in constant light, the indoles did not show significant variation. When the light-dark cycle was reversed (12L:12D to 12D:12L), the profiles of NAS, melatonin, 5-MTAM and 5-MTOL reflected the new cycle within 2 days. The content of serotonin in geese in 12L:12D was higher than that observed in other birds under these conditions, which suggests that this compound may play a special role in the pineal physiology of this species. In conclusion, our results show that the daily variations in the metabolism of melatonin-synthesis-related indoles in the goose pineal gland are generated endogenously and controlled by environmental light conditions, as in other birds. However, comparison of the results obtained with the goose to those obtained with other species (chicken, duck) unambiguously shows that the profiles of pineal indoles differ markedly between species, in both the quantitative proportions of the compounds and the characteristics of the diurnal changes. These findings provide strong arguments for the need for comparative studies.

Diurnal profiles of melatonin synthesis-related indoles, catecholamines and their metabolites in the duck pineal organ

This study characterizes the diurnal profiles of ten melatonin synthesis-related indoles, the quantitative relations between these compounds, and daily variations in the contents of catecholamines and their metabolites in the domestic duck pineal organ. Fourteen-week-old birds, which were reared under a 12L:12D cycle, were killed at two-hour intervals. The indole contents were measured using HPLC with fluorescence detection, whereas the levels of catecholamines and their metabolites were measured using HPLC with electrochemical detection. All indole contents, except for tryptophan, showed significant diurnal variations. The 5-hydroxytryptophan level was approximately two-fold higher during the scotophase than during the photophase. The serotonin content increased during the first half of the photophase, remained elevated for approximately 10 h and then rapidly decreased in the middle of the scotophase. N-acetylserotonin showed the most prominent changes, with a more than 15-fold increase at night. The melatonin cycle demonstrated only an approximately 5-fold difference between the peak and nadir. The 5-methoxytryptamine content was markedly elevated during the scotophase. The 5-hydroxyindole acetic acid, 5-hydroxytryptophol, 5-methoxyindole acetic acid and 5-methoxytryptophol profiles were analogous to the serotonin rhythm. The norepinephrine and dopamine contents showed no significant changes. The DOPA, DOPAC and homovanillic acid levels were higher during the scotophase than during the photophase. Vanillylmandelic acid showed the opposite rhythm, with an elevated level during the daytime.

Description and surgical removal of the cranial cervical ganglia in 3- to 5-day-old chicks

The cranial cervical sympathetic ganglion (CCG) provides the primary innervation of the pineal gland in several gallinaceous species. The CCG is located at the base of the skull near the exoccipital bone, dorsal to the level of the vagus and glossopharyngeal nerves. It occupies a much larger volume and appears pinkish-gray, instead of white, when compared to the petrosal ganglion. To surgically remove the CCG, chicks were anesthetized with halothane vapor. Following a small skin incision, blunt dissection was used to expose the CCG lying adjacent to the internal carotid. The ganglion was grasped with small forceps and pinched free of its fine neural connections to adjacent nerves. The success of the surgery was confirmed visually and by complete adrenergic dennervation of the pineal gland. The entire surgical procedure required approximately 20 min per bird. Mortality was less than 20% overall.

Suppression of pineal multiunit response to flash after habenular lesion in quail

Habenular nuclei were completely destroyed in male photostimulated and nonphotostimulated quail (Coturnix coturnix japonica). Lesion of the nuclei habenulae led to a markedly increased pineal multiunit activity (MUA) pattern in both long and short daily photoperiods compared to control values. Intact, as well as habenular lesioned birds, showed a lower level of pineal MUA under long-day rearing than under short-day rearing. The decrease in pineal firing rates found in controls under repetitive flash-light stimulations was suppressed in quail bearing habenular lesions. Data are compared to results obtained in sympathectomized and blinded birds. It is suggested that some acute photic information might reach the pineal organ through retinal receptors and habenular pathways. However chronic influence of lighting on pineal MUA, mediated by the retina, does not seem to involve habenular or cervical sympathetic pathways in quail.

Pineal function and oviposition in Japanese quail: superior cervical ganglionectomy and photoperiod

Bilateral ablation of the superior cervical ganglia appears to deprive the pineal body of sympathetic innervation. Although this procedure presumably interrupts the neural circuit for transmission of optic information to the pineal, oviposition rates of ganglionectomized females exposed to stimulatory (15-hour) or to nonstimulatory (4-hour) daily photoperiods do not differ from those of the controls.