ABSTRACT
The advanced teleost Chelon labrosus shows a well-developed organum vasculosum laminae terminalis (OVLT). Together, the vascular organization and ultrastructure have many similarities with those found in mammals, though it is somewhat simpler. To date, the dense network of fenestrated capillaries in the nervous parenchyma of the OVLT observed in Chelon labrous has not been reported in other fishes, and resembles the porta system of mammals. However, the OVLT does not present intraventricular neuronal processes, as occurs in the corresponding organ of most vertebrates. Moreover, between the numerous neurons and the neuropil that surround these capillaries, terminal buttons with clear and dense-core vesicles can be appreciated. Most striking is the contact of neurons and even terminal buttons with the basal lamina of the external limiting membrane without interpose glial prolongations that separate the nervous parenchyma from the perivascular space; this represents windows in the blood brain barrier. The above characteristics and the absence of cilaited or chemorecptors structures suggest that neurohemal function of the OVLT, possibly under the control of neurotransmiters secreted by the terminal buttons dispersed throughout the whole organ.
Subject(s)
Capillaries/ultrastructure , Cerebral Ventricles/ultrastructure , Neurons/ultrastructure , Perciformes/anatomy & histology , Animals , Basement Membrane/ultrastructure , Capillaries/cytology , Cerebral Ventricles/blood supply , Cerebral Ventricles/cytology , Dendrites/ultrastructure , Intercellular Junctions/ultrastructure , Microscopy, Electron , Muscle, Smooth, Vascular/cytology , Muscle, Smooth, Vascular/ultrastructure , Neuroglia/ultrastructure , Neurons/cytology , Preoptic Area/cytology , Preoptic Area/ultrastructureABSTRACT
A comparative study of cholera toxin (CT) and wheat germ agglutinin (WGA) conjugated with horseradish peroxidase (HRP) was made on trigeminal central projections of the lower incisor gingiva afferent neurons in the guinea pig. Considerably more CT-HRP-labeled endings were observed in the trigeminal sensory nuclear complex (TSNC) and in the cervical spinal cord (C1-C8). The substantia gelatinosa (lamina II) of both the caudal nucleus of the TSNC and C1-C2 was the only area where WGA-HRP labeled more terminals. CT-HRP-labeled fibers and endings were traced up to C7-C8, whereas with WGA-HRP were rare caudal to C5. A comparison of the two methods currently in use, i.e. the 2-step glutaraldehyde and sodium periodate, showed that the latter yields conjugates which are more sensitive as neuroanatomical tracers.
Subject(s)
Trigeminal Nuclei/ultrastructure , Animals , Brain Stem/cytology , Brain Stem/ultrastructure , Cholera Toxin , Female , Gingiva/innervation , Glutaral , Guinea Pigs , Histocytochemistry , Horseradish Peroxidase , Neural Pathways/ultrastructure , Periodic Acid , Spinal Cord/cytology , Staining and Labeling , Synapses/ultrastructure , Trigeminal Nuclei/cytology , Wheat Germ Agglutinin-Horseradish Peroxidase Conjugate , Wheat Germ AgglutininsABSTRACT
Large groups of cilia are found on certain nucleus praeopticus magnocellularis (NPOM) and nucleus lateralis tuberis (NLT) neurons in the hypothalamus of a higher teleost, Chelon labrosus. They normally appear in an invaginated area of the perikaryon in the proximity of large numbers of synapsis buttons, and often close to unfenestrated capillaries. It is suggested that these ciliosynaptic groups act as osmoreceptors.
