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Wicht, Helmut; Northcutt, R. Glenn
doi: 10.1002/cne.903370402pmid: 8288769
The extent of the secondary olfactory projections shows great variation among different groups of craniates. Gnathostomes typically display restricted secondary olfactory projections, whereas lampreys have more extensive projections. Any attempt to determine the phylogenetic polarity of these characters, that is, to decide which is primitive and which is derived, requires an investigation of the secondary olfactory system in the sister group of lampreys and gnathostomes, the hagfishes. Therefore the secondary olfactory projections of the Pacific hagfish, Eptatretus stouti, were traced with the use of horseradish peroxidase and the lipophilic fluorescent tracing compound Dil. The projections are bilateral and massive to all pallial areas and the septum, moderate to the striatum, and relatively weak to the preoptic and infundibular regions of the hypothalamus, reaching caudally to the diencephalic‐mesencephalic boundary. Afferents to the olfactory bulb arise from the pallium, the preoptic area, and the ventral thalamus. We compare the secondary olfactory projections in hagfishes with those in lampreys and in gnathostomes, and we conclude that the presence of extensive secondary olfactory projections is a primitive character of craniate brains. © 1993 Wiley‐Liss,Inc.
Breder, Christopher D.; Tsujimoto, Masafumi; Terano, Yoshitake; Scott, Donald W.; Saper, Clifford B.
doi: 10.1002/cne.903370403pmid: 8288770
Tumor necrosis factor‐α (TNFα) is a protein released from macrophages during infection and inflammation. Recent studies suggest that it has several effects within the central nervous system, including generation of fever, enhancement of slow wave sleep, and stimulation of pituitary hormone secretion. We have proposed that TNFα may be synthesized by neurons in the CNS and used as a neuromodulator in the pathways involved in the central control of these activities. To test this hypothesis, we have used an antiserum raised against recombinant murine (rm) TNFα with an indirect immunoperoxidase technique to stain the murine CNS immunohistochemically. Western blot analysis of mouse brain homogenates revealed one band with electrophoretic mobility identical to that of rmTNFα. We identified TNFα‐like immunoreactive (ir) neurons in the hypothalamus, in the bed nucleus of the stria terminalis, in the caudal raphe nuclei, and along the ventral pontine and medullary surface. TNFαir innervation was widespread within the CNS, particularly in areas involved in autonomic and endocrine regulation, including the hypothalamus, amygdala, bed nucleus of the stria terminalis, parabrachial nucleus, dorsal vagal complex, nucleus ambiguus, and thoracic sympathetic preganglionic cell column. Our data suggest that TNFα may serve as a neuromodulator in central pathways involved in the regulation of the autonomic, endocrine and behavioral components of the acute‐phase response to inflammation and infection. © 1993 Wiley‐Liss,Inc.
Leprêtre, Emmanuel; Anglade, Isabelle; Williot, Patrick; Vandesande, Frans; Tramu, Gérard; Kah, Olivier
doi: 10.1002/cne.903370404pmid: 8288771
The brain of the sturgeon has recently been shown to contain at least two forms of GnRH (gonadotropin‐releasing hormone), mammalian GnRH (mGnRH) and chicken GnRH‐II (cGnRH‐II). In this study, we compared the distribution of immunoreactive (ir) mGnRH and cGnRH‐II in the brain of immature Siberian sturgeons (Acipenser baeri). The overall distribution of mGnRH was very similar to the distribution of sGnRH in teleosts such as salmonids or cyprinids. mGnRH‐ir perikarya were observed in the olfactory nerves and bulbs, the telencephalon, the preoptic region, and the mediobasal hypothalamus. All these cell bodies are located along a continuum of ir‐fibers that could be traced from the olfactory nerve to the nerve to the hypothalamopituitary interface. No ir‐fibers were observed in the anterior lobe of the pituitary, but a few were seen to enter the neurointermediate lobe. mGnRH‐ir fibers were detected in many parts of the brain, particularly in the forebrain. mGnRH‐ir cerebrospinal fluid‐containing cells were observed in the telencephalon, the preoptic region, and the mediobasal hypothalamus. In contrast, cGnRH‐II was present mainly in the posterior brain, although a few ir axons were seen in the above‐mentioned territories. In particular, cGnRH‐II‐ir cell bodies, negative for mGnRH, were consistently observed in the nucleus of the medial longitudinal fasciculus of the midbrain tegmentum. The cGnRH‐II innervation in the optic tectum, cerebellum, vagal lobe, and medulla oblongata was more abundant than the mGnRH innervation in the same areas. This study provides evidence that the organization of the GnRH systems in a primitive bony fish is, highly similar to that reported in teleosts and further documents the differential distribution of two forms of GnRH in the brain of vertebrates. © 1993 Wiley‐Liss,Inc.
Nagayama, Toshiki; Isogai, Yukihiro; Namba, Hisaaki
doi: 10.1002/cne.903370405pmid: 8288772
Not only nonspiking local interneurons but also spiking local interneurons in the terminal abdominal ganglion of the crayfish (Procambarus clarkii Girard) contribute to form the motor output of the uropod. In this study, 14 spiking local interneurons are identified by their gross morphology and physiological properties including the sensory inputs from the uropod and premotor output onto the uropod motor neurons on both sides. Morphologically, they are divided into three groups based on the position of their somata: anterior, medial, and posterior. The main branches of interneurons in each group are usually extended on the side contralateral to the soma, or they have profuse bilateral branches. Physiologically, all of them receive excitatory inputs from the afferents innervating the exopodite on the side ipsilateral their main branches. They are usually silent, and spike only in response to sensory stimulation. The majority of them (11 out of 14 neurons) have output effects on the uropod motor neurons that elicit reciprocally closing pattern. They increased the activity of the closer motor neurons and decreased the activity of the opener motor neurons. Only one interneuron inhibits the closer motor neurons. The remaining two interneurons coactivate both the antagonistic motor neurons. Since the reciprocal closing pattern of the uropod motor neurons is elicited in response to sensory stimulation of the uropod, spiking local interneurons may initiate this local reflex circuit. They detect the initiation of the stimulus and convey signals from the sensory to the motor side. © 1993 Wiley‐Liss,Inc.
doi: 10.1002/cne.903370406pmid: 8288773
Olivocochlear neurons have somata in the superior olivary complex in the brainstem and project fibers to the cochlea. The purpose of the present study was to demonstrate the fiber pathways and branching patterns of olivocochlear fibers within the brainstem. Olivocochlear fibers were labeled by extracellular injections of biocytin into the cochlea of mice. The injections labeled two populations of olivocochlear fibers. Thin olivocochlear fibers arose from small somata of the lateral olivocochlear group located ipsilaterally in the lateral superior olive. Thick olivocochlear fibers arose from larger somata of the medial olivocochlear group located bilaterally in the periolivary nuclei. The lateral olivocochlear and medial olivocochlear fibers had similar courses but differed in their branching patterns. Branches from lateral olivocochlear fibers terminated near their somata of origin in the lateral superior olive or in the lateral vestibular nucleus. Branches from medial olivocochlear fibers terminated in the inferior vestibular nucleus or in the cochlear nuclear complex. A few branches from medial olivocochlear fibers projected to the contralateral side. Although they project primarily to the cochlea, olivocochlear neurons also give off branches to a variety of nuclei in the brainstem, thus involving auditory and non‐auditory nuclei in the olivocochlear reflex system. © 1993 Wiley‐Liss,Inc.
Walker, Ruth H.; Arbuthnott, Gordon W.; Baughman, Robert W.; Graybiel, Ann M.
doi: 10.1002/cne.903370407pmid: 8288774
Medium spiny neurons are the projection neurons of the striatum. They receive the majority of striatal afferents, and they make up the vast majority of all neurons in the striatum. These densely spiny cells thus constitute a major substrate for input‐output processing in the striatum. In the experiments described here we analyzed the dendritic fields of spiny neurons in the squirrel monkey striatum and plotted their orientations with respect to the borders between striosomes and matrix. Medium‐sized spiny neurons in the caudate nucleus were filled intracellularly in a fixed‐slice preparation with the fluorescent dye Lucifer Yellow. Dendritic arbors were reconstructed following immunostaining of the injected neurons with antiserum to Lucifer Yellow and counterstaining for striosome/matrix compartments. A majority of the medium spiny neurons studied had dendritic arborizations that remained within their compartment of origin. Thus the striosome/matrix subdivision not only partitions neurotransmitter molecules and extrinsic striatal connections into two domains in the primate caudate nucleus, but also constrains the dendritic arbors of many projection neurons there. Other medium spiny neurons, however, in both striosomes and matrix, had dendrites that crossed from one compartment into the other. About a quarter of the spiny neurons reconstructed had at least one such crossing dendrite. These results suggest that compartmentalization of afferent and efferent processing by projection neurons in the primate striatum is not absolute. For a subpopulation of spiny neurons in striosomes and matrix, inputs to one compartment could have a direct influence on output cells of the other. © 1993 Wiley‐Liss,Inc.
Walker, Ruth H.; Graybiel, Ann M.
doi: 10.1002/cne.903370408pmid: 8288775
Despite the relatively unfeatured cytoarchitecture of the striatum, this large subcortical region has been found to have a modular macroscopic substructure comprising the neurochemically distinct striosomes and matrix, and, within the matrix, patchy input and output arrangements called matrisomes. In the study reported here, we explored the possibility that the cellular architecture of the striatum is also more specialized than previously suspected. We injected medium spiny neurons in lightly fixed slices of the squirrel monkey caudate nucleus, reconstructed their dendritic arbors, and analyzed the orientations of these arbors with respect to the cardinal planes of the striatum. The data were unequivocal in suggesting that many spiny neurons, whether near striosomes or not, have dendritic arbors with preferred orientations along a diagonal axis running from rostral, dorsal, and medial to caudal, ventral, and lateral. This axis corresponds to the orientations of many striosomes and matrisomes in the squirrel monkey's caudate nucleus. We therefore suggest that the primate striatum is characterized not only by a macroscopic organization dividing it into striosomes and matrisomes, but also by a microscopic architecture observed by the dendritic arbors of many of its projection neurons. We obtained comparable supplementary observations for the ferret caudate nucleus, suggesting that such spatial alignment of spiny dendritic arbors may be a general feature of striatal organization. These polarized dendritic arrangements could provide a cellular framework for compartmental input‐output processing within the striatum. © 1993 Wiley‐Liss,Inc.
Eaton, M. J.; Gudehithlu, K. P.; Quach, T.; Silvia, C. P.; Hadjiconstantinou, M.; Neff, N. H.
doi: 10.1002/cne.903370409pmid: 7904615
Aromatic L‐amino acid decarboxylase (AAAD) is the second enzyme in the sequence leading to the synthesis of catecholamines or serotonin. Antisense riboprobes for aromatic L‐amino acid decarboxylase mRNA were used to map the gene in mouse brain by in situ hybridization. The substantia nigra, the ventral tegmental nucleus, the dorsal raphe nucleus, the locus coeruleus, and the olfactory bulb contained the highest signal for AAAD mRNA. After treatment with the dopaminergic neurotoxin 1‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine (MPTP), the signal disappeared in the substantia nigra, decreased somewhat in the ventral tegmental area, and remained unchanged in the dorsal raphe nucleus. Hypothalamic and cerebellar Purkinje neurons known to contain histidine decarboxylase or glutamic acid decarboxylase, respectively, were unlabeled by the probes. However, neurons in the deep layers of the frontal cortex, many thalamic nuclei, and the pyramidal neurons of the hippocampus were lightly to moderately labeled for mouse AAAD mRNA. The presence of AAAD message in these neurons suggests that the enzyme has functions other than that for the synthesis of the classical biogenic amine neurotransmitters. © 1993 Wiley‐Liss,Inc.
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