Neural elements in the pineal complex of the frog, Rana esculenta, II: GABA-immunoreactive neurons and FMRFamide-immunoreactive efferent axons

1990 ◽  
Vol 4 (05) ◽  
pp. 399-412 ◽  
Author(s):  
P. Ekström ◽  
T. östholm ◽  
H. Meissl ◽  
A. Bruun ◽  
J.G. Richards ◽  
...  

AbstractThe 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 monitor the relative proportions of short and intermediate/long wavelengths in the ambient illumination. The major pathway of information processing in the pineal and frontal organs is the photoreceptor to ganglion cell synapse. It is not known whether interneurons form part of the neural circuitry. In the present study, we demonstrate GABA-immunoreactive (GABA-IR) neurons in the pineal and frontal organs of the frog,Rana esculenta. No GABA-IR axons were observed in the pineal nerve between the frontal and pineal organs, or in the pineal tract that connects the pineal complex with the brain. The GABA-IR neurons differed in morphology from centrally projecting neurons visualized by retrograde labeling with horseradish peroxidase. Thus, we suggest that the GABA-IR neurons in the pineal and frontal organs represent local interneurons.Axons of central origin, immunoreactive with a sensitive antiserum against the tetrapeptide Phe-Met-Phe-Arg-NH2(FMRFamide), were observed in the intracranial portion of the photosensory pineal organ. The immunoreactive axons enter the caudal pole of the pineal organ via the posterior commissure. The largest density of axons was observed in the caudal part, while fewer axons were detected in the rostral portion. The uneven distribution of the FMRFamide-immunoreactive axons may be related to the distribution of different types of intrapineal neurons. FMRFamide-immunoreactive varicose axons were observed in the extracranial frontal organ. A central innervation of the pineal organ, previously known exclusively from amniotes, is probably notper selinked with the evolutionary transition of the pineal organ from a directly photosensory organ to a neuroendocrine organ. It could rather represent a centrifugal input to a sensory system which has been retained when the directly sensory functions have changed, during phylogency, to neuroendocrine functions.

1990 ◽  
Vol 4 (05) ◽  
pp. 389-397 ◽  
Author(s):  
Peter Ekström ◽  
Hilmar Meissl

AbstractThe pineal complex of anuran &hibians 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 centrally projecting neurons respond to all increases in ambient illumination with decreases in spontaneous firing of action potentials, although some neural units in the pineal organ may respond according to wavelength. This difference in responses to light stimulation may be reflected in the neural organization of the two parts of the pineal complex. In the present study, we have analyzed the morphology of the projection neurons of the frontal and pineal organs of the frog,Rana esculenta, by backfilling of the neurons with horseradish peroxidase through their cut axons. In the pineal organ, several types of centrally projecting neurons were observed: peripherally situated unipolar and multipolar neurons, the dendrites of which extend into a superficial axon plexus that surrounds the pineal epithelium; smaller unipolar, bipolar, or multipolar neurons situated close to the central pineal tract; and radially oriented bipolar neurons, with short dendritic processes oriented towards the lumen of the pineal organ. This latter type was strongly reminiscent of photoreceptor cells. The centrally projecting neurons of the frontal organ were multipolar, and situated in the ventral part of the organ. One photoreceptor-like bipolar neuron was observed in one frontal organ. The neurons of the frontal organ did not form a superficial plexus of neurites. This difference may relate to the different ratio of chromaticity/luminosity units in the frontal and pineal organs.


1967 ◽  
Vol 45 (1) ◽  
pp. 117-126 ◽  
Author(s):  
M. A. Hafeez ◽  
P. Ford

The morphohistology and some histochemical aspects of the pineal organ in the sockeye salmon were studied. The distal part of the organ lies in a pineal fossa in the cranial roof. Photosensory cells and two kinds of ependymal supporting cells are present throughout its epithelium, which is entirely devoid of either melanin or lipofuchsin. Besides sensory nerve fibers, efferent end-loops are present on the photosensory as well as the supporting cells. The dorsal pineal nerve tract probably contains both sensory and efferent fibers. The apocrine secretion of sensory as well as some supporting cells is probably associated with either the maintenance of a constant chemical composition of the cerebrospinal fluid or with supply of certain chemical substances to the brain tissue. The secretion in the pineal and the subcommissural organ consists of glycogen, mucopolysaccharides, mucoproteins, and aldehyde fuchsin positive granules.It is proposed that the pineal organ is photosensory as well as secretory and that its photosensitivity might be of some significance in the light-dependent behavior of this species in terms of intensity detection.


1988 ◽  
Vol 88 (3-6) ◽  
pp. 533-543
Author(s):  
I. Vigh-Teichmann ◽  
B. Vigh ◽  
A. Szél ◽  
P. Röhlich ◽  
G. H. Wirtz

1988 ◽  
Vol 134 (1) ◽  
pp. 27-41 ◽  
Author(s):  
C. Walcott ◽  
J. L. Gould ◽  
A. J. Lednor

Homing pigeons appear to use the earth's magnetic field as a compass and perhaps as part of their position-finding system or ‘map’. The sensory system they use to detect magnetic fields is unknown, but two current possibilities are some mode of response by the pineal organ or by the visual system, or it may be based on the magnetite crystals found in their heads. Three series of experiments to test the involvement of magnetite are reported here. The alignment of the permanent magnetic domains in the birds heads was altered by (a) demagnetizing the birds, (b) magnetizing them with a strong magnetic field and (c) exposing the birds to a strong magnetic gradient. None of these treatments had a marked effect on the pigeon's orientation or homing under sunny skies, but a few results obtained under overcast skies suggest that demagnetizing the birds may have increased the scatter of their vanishing bearings. Perhaps pigeons use one magnetic sensor for their magnetic compass and another for some component of the map.


Development ◽  
1990 ◽  
Vol 110 (1) ◽  
pp. 197-209
Author(s):  
B. Sadaghiani ◽  
J.R. Vielkind

Whole mounts and cross-sections of embryos from three species of teleost fish were immunostained with the HNK-1 monoclonal antibody, which recognizes an epitope on migrating neural crest cells. A similar distribution and migration was found in all three species. The crest cells in the head express the HNK-1 epitope after they have segregated from the neural keel. The truncal neural crest cells begin to express the epitope while they still reside in the dorsal region of the neural keel; this has not been observed in other vertebrates. The cephalic and anterior truncal neural crest cells migrate under the ectoderm; the cephalic cells then enter into the gill arches and the anterior truncal cells into the mesentery of the digestive tract where they cease migration. These cephalic and anterior trunk pathways are similar to those described in Xenopus and chick. The neural crest cells of the trunk, after segregation, accumulate in the dorsal wedges between the somites, however, unlike in chick and rat, they do not migrate in the anterior halves of the somites but predominantly between the neural tube and the somites, the major pathway observed in carp and amphibians; some cells migrate over the somites. The HNK-1 staining of whole-mount embryos revealed a structure resembling the Rohon-Beard and extramedullary cells, the primary sensory system in amphibians. Such a system has not been described in fish.


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