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The photosensory pineal complex of anurans comprises an extracranial part, the frontal organ, and an intracranial part, the pineal organ proper. Although the pineal organ functions mainly as a luminosity detector, the frontal organ may monitor the relative proportions of short and intermediate/long wavelengths in the ambient illumination. The major pathway of information processing in the pineal a

The timing of hatching in the Atlantic halibut (Hippoglossus hippoglossus) has been suggested to be regulated by environmental light conditions. However, the photosensory organ that perceives the triggering light has not been identified. In the present study, we investigated the morphogenesis of the pineal organ and the neurochemical differentiation of photoreceptors in the pineal organ and the re

Opsin-like immunoreactivity was observed in the retinae and pineal organs of the mouse, rat and guinea pig, and the pineal organ of the cat. In the retina the immunoreaction was restricted to photoreceptor cells, which displayed immunostaining in their perikarya and outer and inner segments. Distinct pinealocytes endowed with characteristic processes were labelled in the pineal organs of the mouse

Neural processes from mammalian pinealocytes have been discovered in several brain areas. These processes were visualized immunocytochemically in the Djungarian hamster, Phodopus sungorus, with an antiserum against bovine retinal S-antigen and traced as far as the region of the posterior commissure and habenular nuclei. This result indicates that pineal-to-brain connections exist in the mammal, an

Abstract Dark and light adaptation of pineal photoreceptors was studied in the isolated pineal organ of the rainbow trout, Salmo gairdneri. After intracellular recording, the photoreceptors were iontophoretically injected with Lucifer yellow CH or with horseradish peroxidase for morphological characterization. Pineal photoreceptor cells responded to light with a hyperpolarization whose amplitude w

Photoreceptor potentials were recorded intracellularly from the isolated pineal organ of the teleost, Salmo gairdneri, maintained in tissue culture medium for 2-20 h. After electrophysiological characterization the photoreceptor cells were iontophoretically injected with Lucifer Yellow or with horseradish peroxidase for subsequent morphological identification. A brief flash of light elicited a hyp

The effect of GABA (γ-aminobutyric acid), its agonists (muscimol, baclofen) and antagonist (bicuculline) on pineal ganglion cells of the luminosity type were studied in the isolated, superfused pineal organ of the rainbow trout, Oncorhynchus mykiss. Extracellular recordings revealed that GABA added through the superfusion medium caused a clear alteration of the actvity of projecting neurons, which

The development of photoreceptors and two putative neurotransmitter systems in the pineal organ and retina was studied during embryogenesis in the three-spined stickleback Gasterosteus aculeatus L. The investigation was performed by aid of immunocytochemistry using well characterized antisera to the retinal proteins α-transducin (TDα) and S-antigen (SA) (photoreceptor-markers), antisera against l-

We have examined the occurrence of acetylcholinesterase (AChE)-positive cells in the pineal organ of different developmental stages of the Pacific coho salmon. Large numbers of AChE cells were present in fresh-water living alevins, in all stages of presmolts (n=307-544), and in adult spawners (n=696-1774) whereas seawater-living postmolts displayed a total lack of labeled cells. The AChE-reactive

The distribution of the central neural connections of the pineal organ of the larval sea lamprey was investigated by means of anterograde and retrograde tracing with the fluorescent lipophilic dye. DiI (1,1′-dioctadecyl 3,3,3′,3′-tetramethylindocarbocyanine perchlorate). Pinealofugal projections are well developed in larvae, extending from the posterior commissure into the diencephalon and mesence

The relations of the central neural connections of the pineal organ to those of the retinae of the lateral eyes were investigated in the three‐spined stickleback, Gasterosteus aculeatus L. (Teleostei), by anterograde and retrograde transport of horseradish peroxidase (HRP). HRP was applied to the crushed pineal stalk and/or injected into the left or the right eye. Both pineal and retinal efferents

The morphology of intrapineal neurons that give rise to the pineal tract and project to the brain in the rainbow trout was visualized by the use of neuronal backfilling with horseradish peroxidase (HRP). The tracing was performed on excised pineal organs under in-vitro conditions at 4° C, with filling times ranging from 6 to 24 h. Large multipolar, bipolar and unipolar neurons were visualized in t

Putative cholinergic neurons in the photosensory pineal organ of a cyprinid teleost, the European minnow, were studied by use of choline acetyltransferase (ChAT) immunocytochemistry and acetylcholinesterase (AChE) histochemistry. Pinealofugally projecting neurons were visualized using retrograde HRP-filling through their cut axons. For comparison, the distribution of choline acetyltransferase immu

The directly photosensory pineal organ of the rainbow trout functions primarily as a luminance detector. Its neutral output reflects the level of ambient illumination in an almost linear fashion over several orders of magnitude. It may thus transmit information about the daily light-dark cycle to central projection targets in the brain, and exert an important control over putative central oscillat

The integrating circuitry and efferent pathways for neural signals evoked in the photosensory pineal organ by changes in ambient illumination have been investigated by a multidisciplinary approach. Intrapineal efferent neurons were identified by means of retrograde filling with horseradish peroxidase (HRP). In addition to several types of neurons, photoreceptor cells that emitted axons to the brai

Photoreceptor cells in the pineal complex of poikilothermic vertebrates are regarded as homologous with the neuroendocrine pinealocytes in the mammalian pineal organ. They possess an indolamine metabolism, and they contain a number of substances that are immunochemically similar to phototransduction‐related proteins otherwise found in photoreceptors of the lateral eye retina. Using correlative lig

The pineal complex of anuran amphibians is a directly photosensory organ, encompassing both an extracranial portion, the frontal organ, and an intracranial portion, the pineal organ proper. The projection neurons of the frontal organ respond differentially according to the wavelengths of the light stimuli. The pineal organ, on the other hand, functions mainly as a luminosity meter. Most of its cen