bluuebunny/crossref_metadata_2025 huggingface dataset:
Retinotopic organization of central optic projections in Rana pipiens
Authors: Montgomery Neil , Fite Katherine V.
Published: January 2005

The retinotopic organization of the anuran visual system has been investigated with the method of selective anterograde transport of horseradish peroxidase (HRP) following retinal lesions. The course of optic axons to specific structures was also confirmed by retrograde transport in the optic tract following HRP injections in the tectum and pretectum. As the optic nerve reaches the optic chiasm, the fibers from each of the four retinal quadrants appear as bands with the nasal (n) quadrant entering the chiasmal anterior pole, followed by ventral (v), temporal (t), and dorsal (d) quadrants. The preoptic nucleus is the first structure to be innervated, followed by the suprachiasmatic nucleus; both are innervated directly from fibers in the dorsal part of the optic nerve, which contains fibers from all the retinal quadrants. Each quadrant expands across the dorsoventral extent of the chiasm at the point where it enters. At this level the quadrants are arrayed along the rostrocaudal axis (as they are later in the marginal optic tract) in the sequence n‐v‐t‐d. Optic fibers then spread across the chiasm, the nasal quadrant splits, taking up positions in the rostral and caudal margins of the optic radiation. Following the split in the nasal representation, the optic tract is transformed into topographically arranged sheets in the marginal optic tract.

In the other retinorecipient nuclei, the sheet of optic axons is transformed back into the shape of the retinal hemisphere. Topographic maps of this kind display one of two possible orientations: (1) in the tectum and the nucleus lentiformis mesencephali (nLM), the temporal retina is represented in the anterior portion of the nucleus, whereas the nasal quadrant is found in the posterior portion; (2) in the thalamus, the retinotopic map is organized as a mirror‐image reversal of that seen in the tectum and nLM (i.e., the nasal pole is anterior, whereas the temporal pole is in the posterior portion of the nucleus). Structures with this type of retinal map include the rostral visual nucleus, the corpus geniculatum, the nucleus of Bellonci, and the posterior thalamic nucleus. A third type of innervation occurs in the nucleus of the basal optic root (nBOR), which is the only mesencephalic visual nucleus not innervated by the marginal optic tract. The basal optic root is formed by the fibers exiting most caudally from the optic chiasm. All the retinal quadrants contribute to the basal optic root, but no evidence of retinotopy was found in nBOR.

Following HRP injections in the pretectum, the majority of retrogradely labelled fibers were found in the medial portions of the marginal optic tract and chiasm. Tectal injections labelled fibers primarily in the lateral portions of the marginal optic tract and chiasm. It is proposed that this difference is related to the sequential, ontogenetic development of the retina and its central target nuclei.
Ultrastructural analysis of gaba‐immunoreactive elements in the monkey thalamic ventrobasal complex
Authors: Ohara P. T. , Chazal G. , Ralston H. J.
Published: January 2005

This study describes the ventrobasal complex of the primate by using GABA immunocytochemistry at the electron microscopic level. The primate ventrobasal complex has a similar synaptic organization to sensory thalamic nuclei in other species. Two synaptic profiles within the ventrobasal complex contain flattened or pleomorphic synaptic vesicles and are GABA‐immunoreactive. F‐boutons (=F1 type, Guillery's classification; Guillery: Z. Zellforsch. 96: 1–38, '69) are located principally in the extraglomerular neuropil and contain densely packed flattened synaptic vesicles and several elongate mitochondria and establish symmetric (Gray's type II) synaptic contacts. These boutons are not found postsynaptic to any other element and are presynaptic principally to nonimmunoreactive elements that are thought to be thalamocortical relay cell dendrites. PSD‐boutons (=F2 type, Guillery's classification) contain a moderate number of flattened or pleomorphic synaptic vesicles and fewer mitochondria than F‐boutons. PSD‐boutons are found in glomerular and extraglomerular areas of neuropil and establish symmetric synaptic contacts. These boutons are considered to be appendages of interneuron dendrites and are postsynaptic to RL‐, RS (Guillery's classification)‐, F‐, and other PSD‐boutons. PSD‐boutons are presynaptic to thalamocortical relay neurons and interneuron dendrites including PSD‐boutons. Problems in distinguishing F‐ from PSD‐boutons are addressed by comparing immunostained and nonimmunostained material and by the use of serial sections. The majority of synaptic contacts between pleomorphic vesicle‐containing profiles appear to be between PSD‐boutons and other components of interneurons. Few contacts between F‐boutons and local circuit neurons are seen. These data suggest the principal GABAergic input to interneurons in the primate ventrobasal complex is derived from other interneurons.
Lumbar dorsal root ganglia of the cat: A quantitative study of peptide immunoreactivity and cell size
Authors: Garry M. G. , Miller K. E. , Seybold V. S.
Published: January 2005

The purpose of the present study was to quantify the extent to which several peptides and serotonin coexist with substance P or somatostatin in selected lumbar dorsal root ganglia of the cat. The technique for the simultaneous visualization of two antigens by immunofluorescence was used to investigate the coexistence of neuropeptides in the lumbar dorsal root ganglia of colchicine‐treated cats. Perikarya immunoreactive for calcitonin gene‐related peptide, galanin, leu‐enkephalin, somatostatin, and substance P were visualized in both the lumbar 5 and 6 dorsal root ganglia. In contrast, no immunoreactivity was observed for adipokinetic hormone, bombesin, dynorphin A, met‐enkephalin, oxytocin, tyrosine hydroxylase, thyrotropin‐releasing hormone, vasopressin, vasoactive intestinal peptide, or serotonin in either ganglion examined. Substance P coexisted with calcitonin‐gene‐related peptide, somatostatin, and leu‐enkephalin. Somatostatin was colocalized with calcitonin gene‐related peptide, leu‐enkephalin, and substance P but coexisted with galanin minimally. The cell area of immunoreactive perikarya was also examined. Data concerning the cross‐sectional area of immunoreactive cells indicated that somatostatin‐immunoreactive perikarya were generally the largest population observed (up to ∼6,000 μm2). Somatostatin and calcitonin gene‐related peptide, as well as substance P and calcitonin gene‐related peptide, coexisted in populations of cell bodies that had a smaller size (less than 2,000 μm2). These results suggest that certain peptides which coexist in the dorsal root ganglia may provide histochemical markers for functional groups of primary afferent neurons.
Organization of lateral geniculate‐hypothalamic connections in the rat
Authors: Card J. Patrick , Moore Robert Y.
Published: January 2005

The location and chemical identity of neurons interconnecting the lateral geniculate complex and the hypothalamus were analyzed in order to provide further information on the anatomical substrates for the entrainment of circadian rhythms. A particular objective of the study was to characterize the neurons projecting between the intergeniculate leaflet (IGL) of the lateral geniculate complex and the suprachiasmatic nucleus (SCN) and related anterior hypothalamic areas. The connectivity experiments employed five combinations of fluorescent tracer injection and were combined with immunohistochemical localization of either neuropeptide Y (NPY), met‐enkephalin (mENK) or the vasoactive intestinal polypeptide (VIP)/peptide histidine isoleucine (PHI) group. IGL efferents. Injection of tracer into the SCN results in retrograde labeling of NPY‐immunoreactive neurons in the IGL as would be expected from prior work. These neurons and their terminals also contain the C‐flanking peptide of the NPY precursor molecule (CPON). In addition, there are two additional groups of neurons in the IGL that project either to the SCN or the contralateral IGL but do not exhibit NPY immunoreactivity. These include a substantial population of cells that project to the SCN and an even larger group of neurons which project to the contralateral IGL and contain mENK immunoreactivity. Hypothalamic efferents. Injection of tracer into the IGL results in retrograde labeling of scattered neurons throughout the SCN and immediately adjacent anterior hypothalamus ipsilaterally and also in labeling of a small number of neurons in the same areas on the contralateral side of the brain. In rare instances, individual SCN neurons appear to project to both IGLs. However, the retrochiasmatic area (RCA) contains the largest number of retrogradely labeled neurons following tracer injections into the IGL. These neurons are concentrated along the midsagittal plane and in the lateral RCA ipsilateral to the injected IGL. None of the labeled neurons in the SCN or adjacent anterior hypothalamus exhibit VIP or PHI immunoreactivity.

These observations indicate that the anatomical relations between the geniculate complex and the anterior hypothalamus are more complex than previously shown. First, the geniculohypothalamic tract arises from two distinct groups of IGL neurons: one contains NPY/CPON immunoreactivity; the chemical content of the other is not characterized at the present time. Second, the commissural projection between the two IGLs is formed by a third group of neurons, and these cells contain mENK immunoreactivity. Finally, reciprocal projections from the hypothalamus to the IGL arise from neurons in the retrochiasmatic area, SCN, and adjacent anterior hypothalamus. These anatomical observations demonstrate that the neuronal circuitry involved in the entrainment of circadian rhythms consists of a complex series of projections that interconnect the SCN, anterior hypothalamus, and IGL.
Distribution of somatostatin‐like immunoreactivity in the monkey amygdala
Authors: Amaral David G. , Avendañto Carlos , Benoit Robert
Published: January 2005

The distribution of somatostatin‐like immunoreactivity was studied in the macaque monkey (Macaca fascicularis) by using primary antisera that recognize somatostatin‐28 (S309) or somatostatin‐281‐12 (S320). Somatostatin‐immunoreactive neuronal cell bodies were observed in all amygdaloid nuclei and cortical regions. The density of labeled cells varied substantially, however, both within and across the various amygdaloid subdivisions. The highest densities of labeled neurons were observed in layer III of the periamygdaloid cortex, in layers II and III of the medial nucleus, in the magnocellular division of the accessory basal nucleus, and in the medial portion of the lateral nucleus. Many labeled cells were also consistently observed in the caudoventral portion of the lateral division of the central nucleus. Labeled cells were heterogeneous in size and shape ranging from small and spherical to large and multipolar. The density of somatostatin‐immunoreactive fibers also varied greatly from region to region and was often inversely related to the density of immunoreactive cells. Highest densities of immunoreactive fibers were observed in the periamygdaloid cortex, medial nucleus, parvicellular division of the accessory basal nucleus, paralaminar nucleus, ventrolateral portion of the lateral nucleus, parvicellular division of the basal nucleus, and the lateral division of the central nucleus. Fibers and terminals in the central nucleus had a coarsely varicose appearance and this pattern of staining was continuous along the trajectory of the central nucleus projection to the bed nucleus of the stria terminalis. The large, immunoreactive varicosities located in this area often appeared to outline dendritic or vascular profiles within the substantia innominata. The lowest levels of somatostatin‐immunoreactive fibers were observed in the magnocellular division of the basal nucleus and in the ventromedial portion of the accessory basal nucleus.
Distribution of alpha2, alpha3, alpha4, and beta2 neuronal nicotinic receptor subunit mRNAs in the central nervous system: A hybridization histochemical study in the rat
Authors: Wada Etsuko , Wada Keiji , Boulter Jim , Deneris Evan , Heinemann Steve , Patrick Jim , Swanson Larry W.
Published: January 2005

Previous studies have revealed the existence of a gene family that encodes a group of neuronal nicotinic acetylcholine receptor (nAChR) subunits. Four members of this family have been characterized thus far; three of these subunits (alpha2, alpha3, and alpha4) are structurally related to the ligand binding subunit expressed in muscle and form functional nAChRs when combined with the beta2 gene product in Xenopus oocytes. In addition, the alpha4 gene appears to encode two different products (alpha4‐1 and alpha4‐2) that have been proposed to arise by alternative mRNA splicing. Nine different [35S]‐complementary ribonucleic acid (cRNA) probes were used in the present study to map the distribution of these nAChR subunit mRNAs throughout the central nervous system (CNS) of the rat.

It was found that the beta2 gene is expressed in most regions of the CNS, as are the alpha subunit genes as a group. However, each alpha gene is expressed in a unique, although partly overlapping, set of neuronal structures. Alpha4 is the most widely expressed alpha gene, and the evidence suggests that mRNAs for the alpha4‐1 and alpha4‐2 products are virtually always found in the same regions, in approximately the same ratios (alpha4‐2 greater than alpha4‐1). In addition, there are several examples of cell groups that express beta2 but none of the alpha subunit mRNAs examined here (particularly in the hypothalamus), as well as all groups that express the converse, thus suggesting that additional neuronal nAChR subunits remain to be characterized. Finally, the extensive expression of multiple alpha subunits in certain regions, particularly for alpha3 and alpha4 in the thalamus, suggests that there is microheterogeneity in a small population of cells or that some neurons may express more than one alpha subunit. This problem needs to be examined directly with double labeling methods but raises the possibility that some neuronal nAChRs may be composed of more than one kind of alpha subunit. The wide expression of these receptor genes suggests that nAChRs constitute major excitatory systems in the CNS.
“Necklace olfactory glomeruli” form unique components of the rat primary olfactory system
Authors: Shinoda Koh , Shiotani Yahe , Osawa Yoshio
Published: January 2005

A distinct subset of rat primary olfactory neurons was identified immunohistochemically by means of a polyclonal antibody against human placental antigen X‐P2 (hPAX‐P2), an incompletely characterized substance found in all estrogen‐biosynthetic organs. The subset of olfactory receptor cells was distributed widely over the olfactory epithelium with some degree of concentration on the dorsocaudal walls of nasal subcavities. The subset formed unique “necklace olfactory glomeruli,” which were composed of seven to nine solitary glomeruli located in the caudal end of the olfactory bulb. One of them was located in the “modified glomerular complex” reported to be involved in rat suckling behavior.

The projectional patterns of the necklace olfactory system, albeit diffuse, indicated some degree of spatial correspondence between zones of olfactory epithelium and specific glomeruli. Axons emanating from neighboring cells can project to several glomerular loci. From the necklace olfactory system, an average of 150‐200 receptor cells were estimated to converge onto a single necklace glomerulus.
Neuronal and glial changes in the rat phrenic nucleus occurring within hours after spinal cord injury
Authors: Goshgarian Harry G. , Yu Xiao‐Jun , Rafols Joséa A.
Published: January 2005

The present study describes specific morphological changes in the normal ultrastructure of the rat phrenic nucleus which occur within 4 hours after an ipsilateral spinal cord hemisection rostral to the nucleus. Phrenic neurons were identified at EM levels by retrograde HRP labeling. Ultrastructural features of the phrenic nucleus in uninjured animals and at 4 hours and 1, 2, and 4 days after injury were qualitatively analyzed and then quantitated with a computerized morphometric system. Our results indicated that by 4 hours posthemisection, there was a significant increase in the number of double synapses. Furthermore, the number of double synapses remained significantly higher than normal at all the other posthemisection periods. A significant increase in the length of dendrodendritic membrane appositions was also noted as early as 4 hours posthemisection. The mean normal appositional length of 1.42 ± 0.09 μm increased to 1.89 ± 0.12 μm at 4 hours and further increased to 2.20 ± 0.20 μm by 1 day posthemisection. The increase in the length of membrane appositions was most likely due to an active retraction of astroglial processes from their normal position in between the dendrites. Although there was an increase in the mean length of the dendrodendritic appositions, the mean percentage of the appositions (expressed as the total number of appositions divided by the total number of dendrites in each sample) was not increased significantly over normal values during the early posthemisection periods. By 2 and 4 days posthemisection, however, the percentage of dendrodendritic appositions increased to significantly higher values than normal. Normally, 4.68 ± 0.69% of the dendrites in the phrenic nucleus were found to be in apposition, and this number increased significantly to 7.27 ± 1.06% by 2 days and 7.46 ± 0.79% by 4 days posthemisection. At these later posthemisection periods, the mean length of the appositions decreased to levels which were no longer significantly higher than normal. A distribution analysis of the length of each dendrodendritic apposition in both the normal and spinal hemisected rats showed that there were more dendrodendritic appositions in the phrenic nucleus at the later posthemisection periods. It also showed that their mean length was decreased because many of the new appositions were relatively short. The above neuronal and glial alterations of the phrenic nucleus have never before been described as a response to injury of the mammalian spinal cord. Furthermore, the possibility that the above changes could represent the morphological substrate for the unmasking of functionally ineffective synapses in our spinal cord injury model is discussed.
Terminal field of cholecystokinin‐8‐like immunoreactive projection neurons of the rat main olfactory bulb
Authors: Matsutani Shinji , Senba Emiko , Tohyama Masaya
Published: January 2005

The terminal field of cholecystokinin‐8 (CCK)‐like immunoreactive (CCK‐IR) tufted cells in the rat main olfactory bulb was examined by means of immunohistochemistry combined with either an anterograde tracer or a degeneration method. CCK immunostaining was carried out in animals in which Phaseolus vulgaris agglutinin (PHA) had been injected into the main olfactory bulb. Pairs of adjacent sections were processed for CCK and PHA immunostaining, respectively. Dense CCK‐IR terminallike staining was noted in layer Ia of the anterior olfactory nucleus and lateral part of the olfactory tubercle; weaker staining was also observed in the transitional area between the anterior olfactory nucleus and the piriform cortex, in the medial part of the olfactory tubercle, and in the cortical amygdaloid nucleus. The CCK‐IR staining was limited to the area containing PHA‐labeled terminals and was diminished in these sites after unilateral olfactory bulbectomy. Immuno‐electron microscopic analysis showed that CCK‐IR profiles in such regions made asymmetric synaptic contacts, mainly with dendritic spines. These results suggest that CCK‐IR tufted cells project mainly to the anterior olfactory nucleus and lateral part of the olfactory tubercle, and act mainly via axospinous synapses.
Glucocorticoid receptor‐immunoreactivity in C1, C2, and C3 adrenergic neurons that project to the hypothalamus or to the spinal cord in the rat
Authors: Sawchenko P. E. , Bohn M. C.
Published: January 2005

A combined retrograde transport‐double immunohistochemical staining method was used to determine the extent to which rat liver glucocorticoid receptor‐immunoreactivity (GR‐ir) is contained within phenylethanolamine‐N‐methyltransferase (PNMT)‐ir neurons that project to the paraventricular nucleus of the hypothalamus (PVH) or the spinal cord. The results confirmed that cells in the C1, C2, and C3 adrenergic cell groups each contribute to the adrenergic innervation of the PVH, and indicated that the great majority of retrogradely labeled neurons in each group (80% overall) also express GR‐ir. Following injections in the upper thoracic segments of the spinal cord, the bulk of adrenergic neurons that were retrogradely labeled were found in the C1 cell group, though 31% of the total number PNMT‐ir cells that could be retrogradely labeled following spinal injections were localized in the C2 and C3 regions. Of these spinally projecting PNMT‐ir neurons, 62% displayed GR‐ir. The results suggest all three medullary adrenergic cell groups contribute projections to the spinal cord and/or the PVH, and that the capacity to express the GR phenotype is a common, though perhaps not universal, attribute of PNMT‐ir neurons. No pronounced differences in the expression GR‐ir were observed in adrenergic neurons as a function of their location or efferent projections. Brainstem adrenergic neurons may play a role in integrating neuronal and hormonal controls of adrenal function via ascending and descending projections.
Innervation of the guinea pig trachea: A quantitative morphological study of intrinsic neurons and extrinsic nerves
Authors: Baluk Peter , Gabella Giorgio
Published: January 2005

The innervation of the guinea pig trachea was studied in wholemount preparations stained for acetylcholinesterase, catecholamines, and substance P immunoreactivity and by electron microscopy. The majority of parasympathetic and afferent nerve fibres arrive from the vagus via branches of the recurrent laryngeal nerves. The recurrent laryngeal nerves are composed of several fascicles comprising 600–700 small myelinated fibres (2–5 μm diameter) and about 1,000–2,000 unmyelinated fibres; both components exit from the nerve and project in fine branches to the trachea. A separate component of 200–250 large myelinated fibres (more than 5 μm diameter) runs the full length of the nerve and innervates the striated muscles of the larynx. The recurrent laryngeal nerves are slightly asymmetric in their origin, length, number, and composition of fibres, with the right nerve being shorter but with more numerous and thinner myelinated fibres. At the distal end of the recurrent nerve, a fine branch called the ramus anastomoticus connects it to the superior laryngeal nerve. In the tracheal plexus, there are on average 222 ganglion cells (range 166–327), distributed mostly in small ganglia of 12 or fewer neurons. The ganglionated plexus is situated entirely outside the tracheal wall, overlying the smooth muscle. Ligation experiments show that sympathetic nerve fibres reach the trachea with the recurrent nerves via anastomoses between the sympathetic chain and vagus nerves, or occasionally with recurrent nerves directly, the largest being at the level of the ansa subclavia. There are also perivascular sympathetic nerve plexuses. Substance P immunoreactive fibres enter the trachea from the vagus nerves and by pathways similar to those of sympathetic nerves. There are also paraganglion cells within the recurrent laryngeal nerve that contain catecholamines and are surrounded by substance P immunoreactive fibres.

After cervical vagotomy, all the large myelinated fibres of the ipsilateral recurrent laryngeal nerve degenerate and so do all but 10 or 20 small myelinated fibres and all but a few unmyelinated fibres. Degenerating fibres are found within the entire tracheal plexus, indicating bilateral innervation. The small myelinated fibres that survive cervical vagotomy probably represent sympathetic or afferent nerves with their cell bodies located in sympathetic or dorsal root ganglia.
EM autoradiographic study of the projections from the dorsal nucleus of the lateral lemniscus: A possible source of inhibitory inputs to the inferior colliculus
Authors: Shneiderman Amiram , Oliver Douglas L.
Published: January 2005

The fine structure of the projection from the dorsal nucleus of the lateral lemniscus (DNLL) to the inferior colliculus is examined in the cat. Anterograde axonal transport of 3H‐leucine and EM autoradiographic techniques are used to label axonal endings from DNLL. The primary finding is that axonal endings from DNLL contain pleomorphic synaptic vesicles and make symmetrical synaptic contacts. This morphology is associated with inhibitory synapses. The projection from DNLL is the source of approximately one‐third of the axonal endings with pleomorphic vesicles in the central nucleus of the inferior colliculus. In the contralateral central nucleus, only labeled endings with pleomorphic vesicles are found. By comparison, on the ipsilateral side, both endings with pleomorphic vesicles and, to a lesser degree, endings with round vesicles are labeled. Endings from DNLL are more numerous per unit area on the contralateral side. About half of the labeled axonal endings from DNLL terminate upon small dendrites, and another third terminate upon more proximal dendrites and several types of cell bodies. Many axonal endings form multiple synaptic contacts, sometimes on more than one postsynaptic structure. Sites of termination for axonal endings include dendritic spines and branch points of dendrites.

These data support the hypothesis that the DNLL pathway to the inferior colliculus may have an inhibitory function. Previous studies show that DNLL neurons exhibit immunoreactivity to GAD and GABA antibodies. The crossed projection of DNLL to the inferior colliculus forms tonotopically organized bands that terminate as endings with pleomorphic vesicles. These endings may supply GABAergic inputs to the inferior colliculus. Thus, bands from DNLL could provide inhibitory inputs and overlap with bands from other sources that provide excitatory inputs. Overlapping bands may form unique synaptic domains in the inferior colliculus. The uncrossed projections from DNLL may provide the inferior colliculus with a more diffusely organized projection that could include excitatory and inhibitory inputs. Since the DNLL on one side may inhibit the opposite DNLL and the inferior colliculus, the DNLL pathway may regulate ascending inhibition to the midbrain. Presumed inhibitory inputs from DNLL to the inferior colliculus could be involved in binaural information processing and contralateral dominance.
Descending pathways to the spinal cord: II. Quantitative study of the tectospinal tract in 23 mammals
Authors: Nudo R. J. , Masterton R. B.
Published: January 2005

To study the early evolution of the mammalian motor systems, we have collected quantitative data on the nuclear origins of tracts descending into the spinal cord in 99 individuals representing 23 species of mammals and one species of reptile. In each individual, the spinal cord was hemisected at the C1‐C2 junction and raw HRP immediately applied to the cut fibers. After a 3‐day survival period, brain and spinal cord sections were treated with conventional tetramethylbenzidine procedures.

In every case, this procedure resulted in heavy retrograde labeling of neural somata throughout the neuraxis from coccygeal cord to cerebral neocortex. Many thousands of supraspinal neurons were vividly labeled within at least 27 discrete cell groups in every mammal (Nudo and Masterton, '88). Despite the vast number and wide diversity of heavily labeled neurons, however, relatively few labeled somata were found in the superior colliculus. The total number of labeled cells in the tectum contralateral to the hemisection was highest in the cat (909) and second highest in the raccoon (628). In the remaining animals, the number was considerably less—averaging only 243 in the 23 mammalian species, 193 in the 21 noncarnivores, and 95 in the iguana. In 7 species of primates the average was 220, and in 3 species of Old World monkeys the average was 142.

This wide variation in the number of tectospinal neurons is not related to body size, brain size, or absolute and relative tectum size.

Arranging the animals in order of their kinship or recency‐of‐last‐common‐ancestor with Man, the average number of labeled tectal cells tends to decrease slightly, whereas arranging the same animals in order of their kinship with the cat or raccoon shows a marked and statistically reliable increase. Neither the evolutionary increase in the tectospinal tract along the Carnivora lineage nor the slight decrease along Man's lineage is altered by mathematical corrections for allometric or scaling factors. Of an array of morphological, visual, motor, and ecological traits tested statistically as a possible source of the variation in size of the tectospinal tract, only a primarily carnivorous feeding preference was found to be reliably related.

The relatively small number of tectospinal fibers in most mammals in our sample, including the primates, suggests that the tectospinal tract in Man may be quite small, perhaps far too small to warrant continuing description as a “major descending tract”.
Sound‐generating (sonic) motor system in a teleost fish (Porichthys notatus): Sexual polymorphism in the ultrastructure of myofibrils
Authors: Bass Andrew H. , Marchaterre Margaret A.
Published: January 2005

One mechanism used by teleost fishes to produce acoustic communication signals involves the contraction of sonic “drum” muscles that appose the lateral walls of the swimbladder. In one marine species, the midshipman (Porichthys notatus), there is a sex difference in the overall size of the swimbladder as well as in the ultrastructural properties of its myofibrils. Additionally, there are two classes of sexually mature males referred to as Type I and Type II. The peripheral sonic motor system of Type I males differs from that of Type II males and females (which resemble each other) in a number of ways: 1) the mass of their swimbladder and associated sonic muscles is 50% greater, (2) their muscle fibers are several times larger and have a characteristically large volume of sarcoplasm that surrounds the myofibrils and is densely filled with mitochondria, (3) the length of z‐lines of their myofibrils is about 20‐fold greater, and (4) their sarcoplasmic reticulum is more highly branched. The ultrastructure of the myofibrils of Type II males and females resembles that found in the sonic muscle of males and females in other related species. The larger mass and specializations of the sonic muscle in Type I males are considered to be adaptations related to their known role in sound production and the unique long duration “humming” sounds that they generate during the breeding season. The similarity in the sonic motor system between females and Type II males is considered to be related to the utilization of an “alternative mating strategy” by Type II males. To our knowledge, this is the first documentation of a sex difference or, for that matter, a sexual polymorphism in the ultrastructural features of a vertebrate myofibril.
Axonal trajectory and terminal distribution of inspiratory neurons of the dorsal respiratory group in the cat's medulla
Authors: Otake Kazuyoshi , Sasaki Hiroshi , Ezure Kazuhisa , Manabe Motomu
Published: January 2005

In Nembutal‐anesthetized and artificially ventilated cats, we studied the morphological properties of the inspiratory neurons of the dorsal respiratory group (DRG) with HRP intracellular staining. A total of 37 neurons were stained and their axonal trajectories and terminal distribution in the medulla were analyzed. The somata were located predominantly in the ventrolateral region of the nucleus of the solitary tract and were distributed between 2,300 μm rostral and 700 μm caudal to the obex. Most (26/33) of the neurons tested were antidromically activated by the stimulation of the contralateral (n = 24) or ipsilateral (n = 2) cervical cord. To examine the existence of collateral branches in the brainstem, we traced axonal trajectories in 28 neurons. In most cases, the stem axons issuing from the cells of origin coursed ventrally and then turned medially to cross the midline without giving off any axon collaterals. However, six neurons had axonal collaterals in the brain stem ipsilateral to the somata. At least four types of collateralization were observed. The stem axon of the first type bifurcated at the area ipsilateral and ventral to the cell body. One branch crossed the midline to project to the spinal cord, and the other, thinner branch descended caudally in the ipsilateral medullary reticular formation without distributing any terminals. The axon of the second type projected to the contralateral spinal cord and distributed collateral branches with terminal boutons in the ipsilateral ventral respiratory group (VRG). The third type projected to the contralateral spinal cord and distributed terminal boutons in the medial part of the nucleus of the solitary tract (NTS) and its vicinity. The fourth type distributed numerous branches with terminal boutons in and around the ventral part of the NTS and the VRG area. This study indicates that some inspiratory neurons of the DRG influence not only spinal respiratory neurons but also medullary respiratory neurons in the vicinity of the DRG and the VRG.
Immunohistochemical distribution and partial characterization of FLFQPQRFamidelike peptides in the central nervous system of rats
Authors: Kivipelto L. , Majane E. A. , Yang H.‐Y. T. , Panula P.
Published: January 2005

Two peptides that are structurally related to the molluscan tetrapeptide Phe‐Met‐Arg‐Phe‐NH2 (FMRF‐NH2) were recently isolated from bovine brain extract (Yang et al.: Proc. Natl. Acad. Sci. USA 82:7757–7761, '85). These peptides have an attenuating effect on morphine‐induced analgesia when injected intracerebroventricularly in rats. Antisera against the two peptides–an octapeptide, Phe‐Leu‐Phe‐Gln‐Pro‐Gln‐Arg‐Phe‐NH2 (F8F‐NH2), and an octadecapeptide, Ala‐Gly‐Glu‐Gly‐Leu‐Ser‐Ser‐Pro‐Phe‐Trp‐Ser‐Leu‐Ala‐Ala‐Pro‐Gln‐Arg‐Phe‐NH2 (A18F‐NH2)—were raised in rabbits and characterized with standard radioimmunoassay and immunohistochemical blocking controls.

This study was aimed at localizing neurons in the rat brain that contain immunoreactivity for these peptides. Cryostat sections of normal and colchicine‐treated Sprague‐Dawley rat brains were incubated with the specific antisera and the immunoreactivity was visualized by the PAP or the FITC method. Immunoreactive neurons were detected in the hypothalamus and nucleus of the solitary tract. Relatively dense networks of fibers and terminals were observed in the lateral parabrachial nucleus and in the nucleus of the solitary tract. Fibers and terminals were also seen in the lateral septum, amygdala, hypothalamus, neurohypophysis, thalamus, periaqueductal gray, and several medullary nuclei.

In these areas the immunoreactivity was abolished when the antisera were incubated with the corresponding synthetic peptides F8F‐NH2 and A18F‐NH2. Preincubation of the antisera with neuropeptide Y (NPY) did not affect the staining. The results suggest that there are neurons in the rat brain that contain F8F‐NH2‐ and A18F‐NH2‐like peptides. The neuronal system described here may have a role in the regulation of autonomic functions, such as hypothalamic control and respiratory functions. The neuronal connections of the cells containing F8F‐NH2‐ and A18F‐NH2‐like peptides remain to be studied.
Mamillary body in the rat: Topography and synaptology of projections from the subicular complex, prefrontal cortex, and midbrain tegmentum
Authors: Allen Gary V. , Hopkins David A.
Published: January 2005

The retrograde and anterograde transport of horseradish peroxidase conjugated to wheat germ agglutinin (WGA‐HRP) has been used to trace afferent connections of the rat mamillary body (MB) at the light and electron microscopic levels. Injections of WGA‐HRP into different parts of the MB resulted in heavy retrograde labeling in the subicular complex, medial prefrontal cortex, and dorsal and ventral tegmental nuclei. Injections of WGA‐HRP into each of these brain regions, respectively, resulted in anterograde labeling with specific distributions and characteristic synaptic organizations in the MB. Projections from the rostrodorsal and caudoventral subiculum terminated in a topographically organized laminar fashion in the medial mamillary nucleus bilaterally, whereas afferent projections from the presubiculum and parasubiculum terminated only in the lateral mamillary nucleus. Labeled axon terminals which originated from the subicular complex were characterized by round vesicles and formed asymmetric synaptic junctions with small‐diameter dendrites and dendritic spines in the medial and lateral mamillary nuclei. Projections from the prefrontal cortex originated mainly in the infralimbic area and to a lesser degree in the prelimbic and anterior cingulate areas. Injections of tracer into these brain regions gave rise to dense labeling of axon terminals in the medial mamillary nucleus, pars medianus, and in the anterior dorsomedial portion of the pars medialis. The labeled terminals were characterized by round vesicles and formed asymmetric synaptic junctions with small‐diameter dendrites and dendritic spines. Projections from the dorsal tegmental nucleus terminated in the ipsilateral lateral mamillary nucleus, whereas afferent projections from the anterior and posterior subnuclei of the ventral tegmental nucleus terminated topographically in the medial mamillary nucleus. The ventral tegmental nucleus, pars anterior projected to the midline region of the medial nucleus and the dorsolateral and ventromedial subdivisions of the pars posterior projected to medial and lateral parts of the medial nucleus, respectively. In contrast to the synaptic morphology of subicular complex and medial prefrontal cortex axon terminals in the MB, labeled axon terminals in the MB which originated from the midbrain tegmentum were characterized by pleomorphic vesicles and formed symmetric synaptic junctions with neuronal somata and proximal dendrites as well as distal dendrites and dendritic spines. The morphological differences among axon terminals of afferent projections from the subicular complex and the medial prefrontal cortex compared to those from the midbrain tegmentum suggest that the inputs differ in terms of excitatory or inhibitory effects on MB neurons. It is proposed that cortical, subcortical, and brainstem connections of the MB form three distinct neural circuits which may represent anatomical substrates for different functional activities.
Location of forelimb motoneurons in the Japanese toad (Bufo japonicus): A horseradish peroxidase study
Authors: Oka Yoshitaka , Ohtani Ritsuko , Satou Masahiko , Ueda Kazuo
Published: January 2005

To label the spinal motoneurons innervating the forelimb muscles of the Japanese toad, horseradish peroxidase (HRP) was injected into these muscles or applied to the cut end of the branchial nerves (N. radialis and N. ulnaris). Spatial distribution of the HRP‐labeled motoneurons was reconstructed from serial frontal sections of the spinal cord and their location was examined.

Motoneurons innervating forelimb muscles were distributed in the lateral cell column from segment 3 to segment 5 of the ipsilateral brachial spinal cord. In the transverse plane of the spinal cord, motoneurons innervating the medial forearm muscles (innervated by N. ulnaris) were located in the more medial part of the lateral cell column, whereas those innervating the lateral forearm muscles and the upper arm muscle (innervated by N. radialis) were located in the more lateral part of the lateral cell column. Along the longitudinal axis of the spinal cord, motoneurons innervating the more anterior (flexor side) forearm muscles were located in the more rostral part of the spinal cord, whereas those innervating the more posterior (extensor side) forearm muscles were located in the more caudal part of the spinal cord.

Thus, motoneurons innervating forearm muscles were well organized somatotopically not only in the transverse plane, but also along the longitudinal axis of the spinal cord. Such a somatotopic organization of motoneurons along the longitudinal axis could also be regarded as a functional one; the flexor motoneurons were located rostrally to the extensor motoneurons.
Corticopontine projection in the rat: The distribution of labelled cortical cells after large injections of horseradish peroxidase in the pontine nuclei
Authors: Legg C. R. , Mercier B. , Glickstein M.
Published: January 2005

The distribution of cortical cells projecting to the pontine nuclei in rats was studied by making large injections of horseradish peroxidase that filled the basilar pons and measuring the density of labelled cells in each cortical area. All retrogradely labelled cells were layer V pyramidal cells. The highest densities of labelled cells were observed in the motor areas. The lowest densities were in temporal association cortex and perirhinal cortex. Visual cortical areas, including the primary visual cortex, provided a major source of pontine projections. The distribution of corticopontine cells within the primary visual cortex was studied in more detail. In all cases the highest density of labelled cells was observed in the region of cortex that represents the nasal visual field. Control injections into brainstem regions adjacent to the pontine nuclei produced a much lower absolute density of retrogradely labelled cortical cells and the distribution of those cells was different from that observed following pontine injections. We conclude that every area of the rat's cerebral cortex projects to the pontine nuclei and that there are consistent variations in the density of the projections both between and within areas.
Comparative study of glutamate decarboxylase immunoreactive boutons in the mammalian inferior olive
Authors: Nelson Barbara J. , Adams Joe C. , Barmack Neal H. , Mugnaini Enrico
Published: January 2005

An antiserum raised against rat glutamate decarboxylase was used to map GABAergic boutons in the inferior olive of rabbit, cat, rhesus monkey, and human. A description of the human periolivary region is also included. The inferior olive of each species contained a dense GABAergic innervation, but immunostaining intensities varied among regions. These intensities were evaluated visually and photomertrically, and the sizes and frequencies of occurence of boutons in various olivary subnuclei were measured. The beta nucleus in all species was intensely immunostained and contained the largest boutons. The caudal subdivision of the dorsal accessory olive stained with a lower intensity than the beta nucleus, but contained similarly large GABAergic boutons. By visual analysis, the rostral subdivision and the subnucleus a of the medial accessory olive and the principal olive were stained with an intermediate intensity, and these regions contained small GABAergic boutons. Photometric analysis of focal regions of the neuropil, however, revealed species differences in the staining intensity of the principal olive, which was lowest in rabbits and highest in primates. In all species, the lowest immunostaining intensity was observed in the subnucleus b of the medial accessory olive. Species variations in bouton sizes and regional staining intensities were observed in the dorsal cap and the dorsomedial cell column. The heterogeneous staining pattern and regional variation of bouton size argue for the existence of separate GABAergic projections to discrete regions of the inferior olive. Since glutamate decarboxylase immunostaining patterns in the olive are largely similar across species, the afferent projections producing these patterns may also be similar.
Distribution of phenylethanolamine N‐methyltransferase cell bodies, axons, and terminals in monkey brainstem: An immunohistochemical mapping study
Authors: Carlton Susan M. , Honda Christopher N. , Denoroy Luc
Published: January 2005

Adrenaline (epinephrine) is an important candidate transmitter in descending spinal control systems. To date intrinsic spinal adrenergic neurons have not been reported; thus adrenergic input is presumably derived from brainstem sites. In this regard, the localization of adrenergic neurons in the brainstem is an important consideration. Maps of adrenergic cell bodies and to a lesser axons and terminal fields have been made in various species, but not in monkeys. Thus, the present study concerns the organization of adrenergic systems in the brainstem of a monkey (Macaca fascicularis) immunohistochemically mapped by means of an antibody to the enzyme phenylethanolamine N‐methyltransferase (PNMT). PNMT‐immunostained cell bodies are distributed throughout the medulla in two principal locations. One concentration of labeled cells is in the dorsomedial medulla and includes the nucleus of the solitary tract (NTS), the dorsal motor nucleus of the vagus (X), and an area ventral to X in a region of the reticular formation (RF) known as the central nucleus dorsalis (CnD) of the medulla. A few scattered cells are observed in the periventricular gray just ventral to the IVth ventricle and on midline in the raphe. The second major concentration of PNMT‐immunostained cells is located in the ventrolateral RF, lateral and dorsolateral to the inferior olive (IO), including some cells in the rostral part of the lateral reticular nucleus (LRN). Terminal fields are located in the NTS, X, area postrema (AP), and the floor of the IVth ventricle in the medulla and pons. A light terminal field is also observed in the raphe, particularly raphe pallidus (RP). A heavy terminal field is present in locus coeruleus (LC). Fibers labeled for PNMT form two major fiber tracts. One is in the dorsomedial RF extending as a well‐organized bundle through the medulla, pons, and midbrain. A second tract is located on the ventrolateral edge of the medulla and caudal pons. Fibers in this tract appear to descend to the spinal cord. A comparison with maps of other catecholamine neurons in primates is discussed, confirming that the distribution of the adrenergic system in monkeys is similar to that described in the human.