The Journal of comparative neurology
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The lateral bed nucleus of the stria terminalis (BSTL) and central nucleus of the amygdala (Ce) are amygdaloid nuclei that have similar afferent and efferent connections within the brain. Previous studies have demonstrated that both regions send axonal projections to the dorsal vagal complex (dorsal motor nucleus and nucleus tractus solitarii). The present study used the combined retrograde fluorescence-immunofluorescence method to examine whether cells contributing to this pathway contained any of the following neuropeptides: corticotropin-releasing factor, neurotensin, somatostatin, substance P, enkephalin, or galanin. ⋯ However, it is also apparent that the majority of putative transmitter types within the amygdaloid vagal projection still are unknown. The results suggest that the dorsal and ventral BSTL and the lateral and medial Ce, respectively, are homologous zones with regard to chemoarchitecture and connections. The data is discussed considering the possible function of peptides within descending amygdaloid pathways to the brainstem.
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Efferent axons to the guinea pig cochlea were labeled by extracellular injections of horseradish peroxidase into the intraganglionic spiral bundle within the spiral ganglion. The terminal fibers formed by these axons were classified according to their patterns of termination within the basal turn of the cochlea. A class of terminal fibers designated "autonomic" forms a highly branched plexus in the osseous spiral lamina but does not enter the organ of Corti. ⋯ A second major class of olivocochlear fibers, OHC efferent fibers, forms large boutons on the outer hair cells, and although they sometimes spiral beneath the IHCs for some length, they do not give off terminals to this region. The OHC efferent axons are thick and myelinated as they enter the cochlea, and they branch near the spiral ganglion to form several terminal fibers. Some of these terminal fibers are thin as they travel from the intraganglionic spiral bundle across the osseous spiral lamina to the organ of Corti, whereas others are thick and obviously myelinated as far peripheral as the habenula.(ABSTRACT TRUNCATED AT 400 WORDS)
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The hypothalamus is closely involved in a wide variety of behavioral, autonomic, visceral, and endocrine functions. To find out which descending pathways are involved in these functions, we investigated them by horseradish peroxidase (HRP) and autoradiographic tracing techniques. HRP injections at various levels of the spinal cord resulted in a nearly uniform distribution of HRP-labeled neurons in most areas of the hypothalamus except for the anterior part. ⋯ A medial stream distributed labeled fibers to the NRM, rostral NRP, the upper thoracic intermediolateral cell group, and spinal lamina X. A second and well-defined fiber stream, probably derived from the PVN, distributed many fibers to specific parts of the lateral tegmental field, to the solitary and dorsal vagal nuclei, and, in the spinal cord, to lamina I and X, to the thoracolumbar and sacral intermediolateral cell column, and to the nucleus of Onuf. The lateral hypothalamic area sent many labeled fibers to the lateral part of the brainstem and many terminated in the caudal brainstem lateral tegmentum, including the parabrachial nuclei, locus coeruleus, nucleus subcoeruleus, and the solitary and dorsal vagal nuclei.(ABSTRACT TRUNCATED AT 400 WORDS)
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Afferent connections of the anterior thalamic nuclei (ATN) are classically thought to originate in the mammillary body and limbic cortex. This study explores nonlimbic sources of ATN afferents by using retrograde transport of horseradish peroxidase (HRP) to ascertain the relative contribution of these connections. Spread of HRP into adjacent regions was prevented either by removing the overlying cortex or by injecting through permanently implanted cannulas. ⋯ In conclusion, ATN receive afferents from several nonlimbic regions. Of these inputs, the pretectum may be the primary route through which sensory information reaches ATN. In addition, cholinergic input may modulate activity in projections from the mammillary body to ATN through presynaptic muscarinic receptors.
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A population of intersegmental interneurones with axons extending from the meso- to the metathoracic ganglion of the locust is described. They receive specific mechanosensory inputs from one mesothoracic leg. Their cell bodies are in group at the posterior of the mesothoracic ganglion, lying over the lateral base of each connective, and their primary neurites emerge in one of four bundles. ⋯ Some interneurones have one to three axonal branches with sparse and varicose side branches in the mesothoracic ganglion, which resemble the metathoracic axonal branches. The metathoracic axonal branches are mostly restricted to the dorsal neuropil and the dorsal part of the intermediate neuropil where local non-spiking interneurones and motor neurones controlling movements of the hind leg also project. The overlap between the branches of the sensory afferents and the intersegmental interneurones in the mesothoracic ganglion and between those of the nonspiking local interneurones or motor neurones and intersegmental interneurones in the metathoracic ganglion suggest that these interneurones are responsible for transferring information about the action of one leg to an adjacent leg.