bluuebunny/crossref_metadata_2025 huggingface dataset:
Microtubules and caliber of central and peripheral processes of sensory axons
Authors: Fadić R. , Vergara J. , Alvarez J.
Published: January 2005

The microtubular content and caliber of sensory axons were studied in the L7 dorsal root, at the distal pole of the L7 spinal ganglion, and in the sural nerve of cats. Calibers of myelinated axons were symmetrical about the ganglion. In contrast, nonmedullated axons were strikingly different; 80% of the population at the root were smaller than 0.4 μm2, whilst just across the ganglion the same group was less than 20%. The microtubule densities of myelinated axons of the root were 11.8 and 6.1 microtubules/μm2 for 3‐ and 10/μm diameter axons, respectively. Across the ganglion the densities of myelinated axons of equal sizes were 24.2 and 14.4 microtubules/μm2, respectively. These values represent an approximate ratio of 1:2 between central and peripheral microtubule densities. Microtubule densities for nonmedullated axons also decreased with the increase in the cross‐sectional area. The densities of root nonmedullated axons ranged between 90 and 10 microtubules/μm2; these were smaller, usually by a factor of three, than the densities of peripheral axons of a similar size (range: 367–44). Contrasting with the differences observed across the ganglion, the microtubular content and caliber of sensory axons seems to be quite uniform along their peripheral course. This is supported by the similar values found in the juxtaganglionic and sural nerves.

It is estimated that an axon that contains 90 microtubules/μm2 has 26.7 mg of tubulin per ml of axoplasm in its assembled form, and 3.0 mg/ml if it contains 10 microtubules/μm2; these values are the practical limits of assembled tubulin in axoplasms.

We conclude that the microtubule density of an axon is related to axonal size and location (central or peripheral), but is independent of axonal length, axoplasmic mass, distance to soma, and neuronal class. We propose that local exogenous factors contribute to the specification of the microtubular content of axons.
RNA content of normal and axotomized retinal ganglion cells of rat and goldfish
Authors: Barron Kevin D. , McGuinness Charlotte M. , Misantone Louis J. , Zanakis M. F. , Grafstein Bernice , Murray Marion
Published: January 2005

The responses of rat and goldfish retinal ganglion cells to axotomy were examined by a quantitative cytochemical method for RNA and by morphometric measurement 1–60 (rat) and 3–90 (goldfish) days after interruption of one optic nerve or tract intracranially. Unoperated control animals were studied also.

The RNA content of axotomized neurons of rat fell 7–60 days postoperatively. Additionally, atrophy of the axotomized somas occurred. Over time, neuronal atrophy approximately paralleled the loss of RNA, and mean cell area and RNA content were reduced by about 25% 60 days after axotomy. Incorporation of 3H‐uridine by axotomized neurons declined also.

Axotomized retinal ganglion cells of goldfish behaved differently from those of the rat and showed increases in RNA content, most conspicuously 14–60 days postoperatively. Enlargement of axotomized fish neurons occurred but was less proportionately than concomitant increases in RNA content.

The nonaxotomized ganglion cells of goldfish displayed statistically significant increases in size and RNA content 14–49 days after unilateral optic nerve or tract lesions. In contrast, alterations in rat retinal ganglion cells contralateral to interruption of one optic nerve were of limited and questionable significance.

The contrasting reactions to axotomy by the retinal ganglion cells of these two vertebrates, one of which regenerates optic axons and one of which does not, may support the proposition that the somal response to axon injury has an important bearing upon the success or failure of CNS regeneration.

Although mammalian intrinsic neurons commonly undergo regressive changes after axotomy, they may remain viable for long periods during which they may yet prove to be stimulable by pharmacologic or other means to the mounting of a restitutive response to axon injury.
Convergence of intra‐ and interhemispheric cortical afferents: Lack of collateralization and evidence for a subrhinal cell group projecting heterotopically
Authors: Sarter Martin , Markowitsch Hans J.
Published: January 2005

The distribution of corticocortical projecting neurons in the rat's brain was investigated with fluorescent dyes and the retrograde transport of horseradish peroxidase. Although the fluorescent techniques especially revealed the existence of a considerable number of neurons interconnecting the limbic areas (sub‐ and perirhinal cortex, prefrontal, cingulate, and retrosplenial cortex) both intra‐ and interhemispherically, only a negligibly small number of neurons with collateralized axons could be detected. In the rat's anterior dorsolateral cortex an area is described whose neurons are organized in a columnlike fashion and project intra‐ and interhemispherically to the limbic areas examined. The density of efferent connections differed between areas, with an especially high density found in a small region of the subrhinal cortex.

Injections of horseradish peroxidase into different regions of the cingulate and retrosplenial cortex confirmed the existence of widespread heterotopic interhemispheric connections originating from this defined subrhinal area, though the number of retrogradely labeled cells remained consistently smaller than that obtained following the injection of fluorescent dyes. Among the regions studied with horseradish peroxidase injections, those into the retrosplenial cortex showed the highest density of labeled cells within this subrhinal area.

A more detailed examination of the subrhinal region containing the densely labeled neurons (projecting to the contralateral hemisphere) made use of Nissl stains and revealed a morphologically separable area which was characterized by medium‐sized, dark‐staining neurons whose long axons were oriented mediolaterally. The region includes portions of the insular‐perirhinal, entorhinal, and piriform cortex.

It is suggested that the corticocortical projections are basically noncollateralized in the rat. However, there apparently is a dense interhemispheric interconnectivity between the limbic areas. Functional evidence for the defined subrhinal area suggests a prominent role of its neurons in cognitive information processing.

The present evidence for considerable interhemispheric cortical projections may provide a new impetus for studying the intercommunication of the two sides of the brain with both anatomical and behavioral methods.
AComparative analysis of the development of the primary somatosensory cortex: Interspecies similarities during barrel and laminar development
Authors: Rice Frank Lambert , Gomez Caroline , Barstow Chris , Burnet Ann , Sands Peter
Published: January 2005

The development of the barrels and layers II‐V was examined in Nissl‐stained preparations of the primary somatosensory cortex in six species‐ hamster, mouse, rat, gerbil, rabbit, and guinea pig–that have increasingly longer gestation periods. The barrels and layers II‐V begin to differentiate postnatally during the first week postpartum in the hamster, mouse, rat, and gerbil; perinatally in the rabbit; and ∼4 weeks prenatally in the guinea pig.

The structure of the barrels and layers II‐V is similar at the onset of their differentiation in each species, even though there are interspecies differences in the mature structure of the barrels and layer V. The rate of the initial differentiation of the barrels and layers II‐V is also similar in each species, even though there are considerable interspecies differences in the duration of the preceding period of development. In each species, layer V begins to differentiate first from the cortical plate and, within 1 or 2 days, contains sublayers that eventually disappear in the rabbit and guinea pig. About 3 days after the initial differentiation of layer V, layers II‐IV begin to differentiate, seemingly simultaneously, causing the cortical plate to have a trilaminar appearance.

Barrels are first evident just before the appearance of the trilaminar plate in hamsters; concomitant with the trilaminar plate in mice, rats, and guinea pigs; and just after the trilaminar plate in gerbils and rabbits. Septa appear 1 or 2 days after the barrels except in rabbits, which never have septa. Barrel maturation proceeds rapidly after the initial appearance in all species except the hamster, in which continued maturation seems to be delayed until the appearance of the trilaminar plate. The barrels in immature rats and rabbits become more prominent than they will eventually be in the adults.

Our results indicate a close and rapid developmental affilation between layers II‐V, especially layers II‐IV, that seems quite separate from the development of layers I and VI. However, barrel development and differentiation of layers II‐IV seem to be closely, but independently initiated. Secondary remodeling occurs in layer V and the barrels of some species.
Gradual changes in the structure of the barrels during maturation of the primary somatosensory cortex in the rat
Authors: Rice Frank Lambert
Published: January 2005

The maturation of the barrel field in the primary somatosensory cortex was observed in Nissl‐stained preparations from rats ranging in age from 12 days to 1.5 years postpartum. Prior to the 20th day, the barrels in the rat resemble those of the mouse and have distinct cell‐sparse hollows that are surrounded by cell‐dense sides. They span the full thickness of layer IV. Between the 20th and 34th days, the barrels in only the posteromedial part of the barrel field gradually change and the distinction between the hollows and sides is lost throughout all but the deepest part of layer IV. The resulting mature barrels are relatively indistinct and have a uniformly high cell density that extends well into the supragranular layers. In contrast, the barrels in the anterolateral part of the barrel field remain essentially unchanged. The remodeling apparently is not due passively to cortical growth because, by P20, the thicknesses of the cortical layers and the dimensions of the barrels are virtually the same as in the adult. Several mechanisms are considered that may account for the changes. These include a redistribution of the neurons that originally were in barrel sides; a reduction in the neuropil between the neurons that originally were within hollows; and differential growth of layer IV dendrites. The changes in the barrel structure may be related to the differentiation and quantity of innervation in the hairy skin between the vibrissae.
Time of origin of opioid peptide‐containing neurons in the rat hypothalamus
Authors: Khachaturian Henry , Lewis Michael E. , Alessi Norman E. , Watson Stanley J.
Published: January 2005

By using a combined technique of immunocytochemistry and [3H]thymidine autoradiography, we have determined the “birth date” of opioid pep‐tide‐containing neurons in several hypothalamic nuclei and regions. These include proopiomelanocortin (POMC) neurons (represented by ACTH immunoreactivity) in the arcuate nucleus; dynorphin A neurons in the supraoptic and paraventricular nuclei and the lateral hypothalamic area; and leuenkephalin neurons in the periventricular, ventromedial, and medial mammillary nuclei, as well as in preoptic and perifornical areas. Arcuate POMC neurons were born very early in embryonic development, with peak heavy [3H]thymidine nuclear labelling occurring on embryonic day E12. Supraoptic and paraventricular dynorphin A neurons were also labelled relatively early (peak at E13). The lateral hypothalamic dynorphin A neurons showed peak heavy labelling also on day E12, By contrast, leu‐enkephalin neurons in the periventricular nucleus and medial preoptic area exhibited peak heavy nuclear labelling on day E14. Furthermore, perifornical and ventromedial leu‐enkephalin neurons were also born relatively early (peak on days E12 and E13, respectively). However, the leu‐enkephalin neurons in the medial mammillary nucleus were born the latest of all cell groups studied (i.e., peak at E15). The results indicate a differential genesis of these opioid peptide‐containing neuronal groups in different hypothalamic nuclei and regions.
Adrenergic beta receptors are not uniformly distributed in the cerebellar cortex
Authors: Sutin Jerome , Minneman Kenneth P.
Published: January 2005

The noradrenergic (NE) innervation of the cerebellar cortex is sparse, forming a broad plexus of radially oriented axons distributing throughout the granular and molecular layers. Autoradiographic studies of beta‐adrenergic receptor distribution in the rat show the greatest density of silver grains in the molecular layer (Palacios and Kuhar, 1982). In the course of studies of NE hyperinnervated structures, we found that beta receptors are nonhomogeneously distributed in the Purkinje cell layer, where they occur in “patches” overlying small groups of Purkinje cell somata. Tissue sections were incubated in 10 pM 125iodocyanopindolol (ICYP), which binds equally to beta1 and beta2 adrenergic receptors. Nonspecific binding was determined in sections incubated in 125 ICYP and 1 μM dl‐propranolol. Beta‐adrenergic receptor patches are of irregular size and are most prominent in the vermis of lobules I‐IX, although the medial cerebellar hemispheres also show areas of increased silver grains over Purkinje cells. In order to determine the subtype of beta receptors, adjacent sections were incubated with either 125ICYP and the beta2‐selective antagonist IPS‐339, or 125ICYP and the beta1‐selective antagonist practolol. Patches were observed after each incubation procedure, indicating that they are composed of both beta1 and beta2 receptors. Patches are observed in normal animals and also in rats in which cerebellar NE content was increased 165% by neonatal treatment with 6‐hydroxydopamine. This treatment does not alter the density of beta receptors. The cerebellar elements in which the beta receptors are located is not known. While silver grains accumulate over small groups of Purkinje cell somata, they are not coextensive with these cell bodies. The distribution of beta‐adrenergic receptors does not parallel the arrangement of noradrenergic varicosities in the rat cerebellar cortex.
Glutamate decarboxylase‐immunoreactive structures in the rat neostriatum: A correlated light and electron microscopic study including a combination of Golgi impregnation with immunocytochemistry
Authors: Bolam J. P. , Powell J. F. , Wu J.‐Y. , Smith A. D.
Published: January 2005

An antibody to glutamate decarboxylase has been used in a light and electron microscopic study of the neostriatum of rats that had received intracerebral injections of colchicine. In the light microscope, neuronal perikarya and small punctate structures that displayed immunoreactivity were found. The perikarya could be divided into two classes based on their sizes: small‐to‐medium‐sized and large. Proximal dendrites, axon initial segments, and axon collaterals were occasionally stained. When the nuclei of the neurons were visible, they possessed indentations. The immunoreactive punctate structures were spread evenly throughout the neostriatum but occasionally were associated with immunoreactive and nonimmunoreactive perikarya.

When the same sections were examined in the electron microscope, the small‐to‐medium‐sized immunoreactive perikarya were found to be similar in morphology and synaptic input to a class of Golgi‐impregnated neuron that has been previously shown to accumulate locally administered, radiolabelled γ‐aminobutyric acid. Neurons with the ultrastructural characteristics of typical striatonigral neurons did not display immunoreactivity. As neurons in this pathway probably contain γ‐aminobutyric acid, it is possible that our procedure or our antibody does not stain all γ‐aminobutyric‐acid‐containing structures in the neostriatum.

A total of 404 immunoreactive punctate structures were examined by correlated light and electron microscopy or by electron microscopy alone. They were identified as immunoreactive axonal boutons and each of them, when examined in serial sections, displayed typical synaptic specialisations. Membrane specialisations were always of the symmetrical type. At least five distinct targets of the immunoreactive terminals were identified: (1) neurons that were themselves immunoreactive for glutamate decarboxylase; the immunoreactive terminals made synaptic contact with all parts of the neurons examined, i.e., perikarya, proximal dendrites, and axon initial segments. (2) Neurons identified by Golgi impregnation of the same sections as medium‐sized and densely spiny; the immunoreactive terminals made contact predominantly with the perikarya and dendritic shafts. (3) Large neurons found only in the ventral caudate‐putamen, whose somata and dendrites were ensheathed in immunoreactive terminals. (4) Medium‐sized nonimmunoreactive perikarya that possessed nuclear indentations. (5) Large nonimmunoreactive perikarya that had the typical structural features of striatal cholinergic neurons.

It is concluded that there is a diverse innervation of many types of striatal neuron by synaptic terminals that possess the ability to synthesize γ‐aminobutyric acid and that these terminals probably arise from neurons within the neostriatum.
Patterns of muscarinic cholinergic binding in the striatum and their relation to dopamine islands and striosomes
Authors: Nastuk Mary A. , Graybiel Ann M.
Published: January 2005

The distribution of muscarinic cholinergic binding sites in the striatum was studied in relation to the locations of other neurochemical markers in the developing rat, cat, ferret, and human. In addition, patterns of striatal muscarinic binding were studied in the adult cat. Receptor binding autoradiography was carried out with tritiated propylbenzilylcholine mustard ([3H]‐PrBCM), an irreversible muscarinic antagonist, and subsequent serial section analyses involved comparisons among patterns of muscarinic binding, catecholamine histofluorescence, acetylcholinesterase (AChE) staining, Nissl staining, and cell labeling with [3H]‐thymidine.

Muscarinic binding in the immature striatum was characterized by local patchiness as well as regional density gradients in all species, with the most complex patterns appearing in the human. Patches of dense muscarinic binding were shown to lie in register with fluorescent dopamine islands (rat, cat, ferret), with AChE‐positive patches (all species), and with clusters of neurons pulse‐labeled by exposure to [3H]‐thymidine on embryonic day 27 (ferret). At the developmental stages examined, the [3H]‐PrBCM‐positive patches were roughly aligned with regions of weak Nissl staining (cat, human).

Striatal [3H]‐PrBCM binding in the adult cat was dense, and though it usually appeared nearly homogeneous, in some sections patches of elevated binding were present. These had as counterparts, in neighboring sections, AChE‐poor striosomes. We conclude that during development muscarinic cholinergic function is compartmentalized in the striatum in association with dopamine‐containing afferents, and that this compartmentalization may persist to some degree in the adult.
A comparative analysis of glial and neuronal markers in the retina of fish: Variable character of horizontal cells
Authors: Linser P. J. , Smith K. , Angelides K.
Published: January 2005

The immunohistochemical localizations of the enzymes glutamine synthetase, carbonic anhydrase‐C, and the intermediate filament protein GFA were examined for potential neuroglial specificity in the retinas of several types offish. Both glutamine synthetase and carbonic anhydrase‐C appear to be characteristic markers for retinal Müller cells. However, the horizontal neurons of most fish examined also possess high levels of carbonic anhydrase. Furthermore, GFA, the characteristic marker for fibrous astroglia in higher vertebrates, was found specifically localized in the horizontal neurons of several teleost fish. The identity of the GFA antigens was qualified by immunochemical as well as cytological examinations. Furthermore, specific antisera to other intermediate filament proteins, including neurofilaments, validated and contrasted with the observations made with antisera to GFA. The presence of GFA in horizontal neurons of fish is widespread but not typical of all fish. These observations indicate an evolutionary constancy of retinal Müller glial cells. However, these results again focus attention on whether horizontal cells are truly neurons or rather represent an intermediate cell type that may prove useful in studying the evolution, ontogeny, and functional significance of the neuronal‐glial phenotypic dichotomy.
A study of postmortem autolysis in the human organ of corti
Authors: Nadol Joseph B. , Burgess Barbara
Published: January 2005

Forty‐six human temporal bones from 24 individuals were removed at autopsy and prepared for electron microscopy. The adequacy of histologic preservation was evaluated by light and electron microscopy. Characteristic autolytic changes included vacuolization of afferent neurons and neural poles of inner and outer hair cells, lysis of limiting membranes of hair and supporting cells, swelling of endoplasmic reticulum, and dissolution of mitochondrial cristae.

The rate of autolysis varied significantly within cellular components of the inner ear. The neural poles of hair cells demonstrated more rapid autolysis than apical poles and nerve terminals showed more autolysis than myelinated nerve fibers. Postmortem time and the cause of death affected the adequacy of histologic preservation. Fixation in patients dying of pneumonia, hypoxia, head injury, or malignancy tended to be poor, whereas the fixation achieved in patients dying of cardiac disease with postmortem time of under 140 minutes was generally good.
The midbrain periaqueductal gray in the rat. I. Nuclear volume, cell number, density, orientation, and regional subdivisions
Authors: Beitz Alvin J.
Published: January 2005

The midbrain periaqueductal gray is a functionally heterogeneous region which plays an important role in pain modulation. Despite the heterogeneity considerable controversy exists regarding the presence or absence of morphological subdivisions within the region. The present study was designed to evaluate the possibility of morphological subdivisions within the rat periaqueductal gray by using a statistical cluster analysis system. In addition both qualitative and quantitative data concerning neuronal size, shape, and density were obtained. On the basis of measurements of over 12,000 neurons in two planes of section, the mean neuronal length of cell bodies in this region was 14.82 μm and the mean neuronal area was 95.59 μm2. The mean neuronal density was found to be 16,284 cells per mm3. Neuronal density decreased from rostral to caudal in the periaqueductal gray. The data obtained from cluster maps suggest the presence of four subdivisions within this midbrain region. The medial subdivision contains the smallest neurons and exhibits the lowest cell density. The dorsolateral and ventrolateral divisions contain the largest neurons while the dorsal division displays the highest packing density. These results are discussed in light of recent receptor binding and immunohistochemical studies of this region.
Cholecystokinin‐immunoreactive cells form symmetrical synaptic contacts with pyramidal and nonpyramidal neurons in the hippocampus
Authors: Nunzi M. G. , Gorio A. , Milan F. , Freund T. F. , Somogyi P. , Smith A. D.
Published: January 2005

The ultrastructural features and synaptic relationships of cholecystokinin (CCK) Immunoreactive cells of rat and cat hippocampus were studied using the unlabeled antibody immunoperoxidase technique and correlated light and electron microscopy. CCK‐positive perikarya of variable shape and size were distributed in all layers and were particularly concentrated in stratum pyramidale and radiatum: the CCK‐immunoreactive neurons were nonpyramidal in shape and the three most common types had the morphological features of tufted, bipolar, and multipolar cells.

Electron microscopic examination revealed that all the CCK‐positive boutons established symmetrical (Gray's type II) synaptic contacts with perikarya and dendrites of pyramidal and nonpyramidal neurons. The origin of some of the boutons was established by tracing fine collaterals that arose from the main axon of two CCK‐immunostained cells and terminated in the stratum pyramidale; these collaterals were then examined in the electron microscope. The axon of one such neuron exhibited a course parallel to the pyramidal layer and formed pericellular nets of synaptic boutons upon the perikarya of pyramidal neurons. This pattern of axonal arborization is very similar to that of some of the basket cells, previously suggested to be the anatomical correlate for pyramidal cell inhibition. Typical dendrites of pyramidal cells also received symmetrical synaptic contacts from CCK‐immunoreactive boutons, and some of these boutons could be shown to originate from a local neuron in stratum radiatum. Many CCK‐immunoreactive cells received CCK‐labeled boutons upon their soma and dendritic shafts. Synaptic relationship, established by multiple Men passant boutons, was observed between CCK‐positive interneurons of the stratum lacunosum‐moleculare and radiatum. The soma and dendrites of the CCK‐immunostained neurons also received symmetrical and asymmetrical synapses from nonimmuno‐reactive boutons.

These results indicate that the CCK‐immunoreactive neurons participate in complex local synaptic interactions in the hippocampus.
Postnatal changes in the distribution of acetylcholinesterase in kitten striate cortex
Authors: Bear Mark F. , Carnes Kenneth M. , Ebner Ford F.
Published: January 2005

We have traced the postnatal development of axons and cells in kitten striate cortex that contain acetylcholinesterase (AChE) by using a modification of Koelle's histochemical method.

The maturation of AChE‐positive axons was not found to be fully complete until at least 3 months of age, and was characterized by several distinct developmental trends. AChE‐positive fibers in layers IVc–VI proliferate rapidly after birth until, by 4 weeks postnatal, they appear to exceed the adult density. They remain at this level as late as 8 weeks and then decrease to the adult density by 13 weeks. In contrast, the AChE‐positive fibers in layer I do not show a substantial increase in density until 6 weeks of age and the adult level is not achieved before 3 months postnatal. Finally, the density of AChE‐positive fibers in layers II and III appears to increase gradually from birth until the mature pattern is reached at about 6 weeks.

AChE could also be localized histochemically to cell bodies whose position and appearance depended on postnatal age. Stained cells first appeared in the white matter subjacent to layer VI shortly after birth. By 2 weeks of age, most cells in layer VI were also AChE positive. The staining of these cells gradually disappears over the next 2 months until, at 3 months of age, there are no AChE‐positive cells in cat striate cortex. However, a subpopulation of stained neurons appears in layer V by 1 year of age that persists throughout adulthood.

The possible contributions of acetylcholine and AChE to the postnatal development of kitten striate cortex are discussed.
Projections from the anterior ventral cochlear nucleus to the central nucleus of the inferior colliculus in young and aging C57BL/6 mice
Authors: Willott James F. , Pankow David , Hunter Kelly Paris , Kordyban Mary
Published: January 2005

Projections from the anterior ventral cochlear nucleus (AVCN) to the central nucleus of the inferior colliculus (ICC) were studied in young and aging C57BL/6 mice. The latter animals demonstrate progressive loss of hearing. Wheat germ agglutinin‐horseradish peroxidase (WGA‐HRP) was injected into the inferior colliculus and retrograde transport to the AVCN was evaluated. No age‐related differences were found in the area of AVCN sections, quality or labelling, number of labelled neurons adjusted for injection size, or topographic organization of projections. Thus, despite progressing loss of auditory sensitivity, chronic profound hearing loss (oldest animals), and aging, projections from AVCN to ICC remain stable.
Anatomical identification of neurons in selected brain regions associated with maternal behavior deficits induced by knife cuts of the lateral hypothalamus in rats
Authors: Numan Michael , Morrell Joan I. , Pfaff Donald W.
Published: January 2005

The present experiment identified neurons associated with maternal behavior deficits induced by damage to the lateral hypothalamus (LH) in rats. Fully maternal lactating rats received bilateral coronal knife cuts through either the dorsal or ventral LH at the level of the ventromedial nucleus. The blade of the wire knife used to make the cuts was coated with horseradish peroxidase (HRP). The maternal behavior of all females was studied for 4 days postoperatively and then the brains were processed for the localization of neurons retrogradely filled with HRP. The analysis focused on those brain regions thought to be important for maternal behavior.

The dorsal LH cuts severely disrupted maternal behavior while the ventral LH cuts did not. The ventral cuts labeled more medial preoptic area (MPOA) and septal‐diagonal band neurons with HRP than did the dorsal cuts. The dorsal LH cuts labeled more neurons with HRP in the lateral preoptic area (LPOA), magnocellular preoptic area, bed nucleus of the stria terminalis, ventral tegmental area (VTA), substantia nigra, and central gray than did the ventral cuts.

Previous research has suggested that the lateral efferents of the MPOA interact with the VTA in the control of maternal behavior. The results of the present experiment suggest that MPOA axons which descend directly to the brainstem via the ventral LH are not essential for maternal behavior. Our results are consistent with the view that an MPOA‐to‐LPOA‐to‐VTA circuit may be important for maternal behavior.
Inferior colliculus of the house mouse. I. A quantitative study of tonotopic organization, frequency representation, and tone‐threshold distribution
Authors: Stiebler Imme , Ehret Günter
Published: January 2005

Electrophysiological mapping was used to study frequency representation in the inferior colliculus (IC) of the mouse. In the lateral nucleus (LN) only part of the frequency range of hearing was represented and tonotopicity was separate from that in the rest of the IC. Highest frequencies occupied the medial part (M) of the central nucleus (CN). A single complete representation of the hearing range was present only if representations in the dorsal cortex (plus dorsomedial nucleus) and CN (including M) were combined. Continuous isofrequency planes making up these nuclei (without the lateral part of the CN) were reconstructed. They tilted from medial to lateral and from caudal to rostral. The steepness of the slopes increased from caudal to rostral and from dorsal to ventral (i.e., with increasing frequency). Isofrequency planes had similar angles of deviation from the horizontal plane as described for dendritic laminae in the CN. Differences of mapping in the lateral part of the CN from that in the rest of the CN could be explained by the different organization of laminae in this part.

The relative e mounts of IC depth and volume occupied by parts of the mouse audible frequency range were quantified. Frequency representation along IC depth wan not proportional to that along cochlear length. Compared with the relative density of afferent nerve fiber supply within given frequency ranges represented along the basilar membrane, there is a relative under‐representation in the IC up to 15–20 kHz and an over‐representation of higher frequencies.

Highest absolute tone sensitivity (lowest threshold) was found in neurons forming a column (running perpendicular to isofrequency planes) in the center of the IC.

Results are discussed with regard to frequency representation, intrinsic neuronal organization, and functional segregation in the IC of mammals.
Morphology of retinogeniculate terminals in the turtle, pseudemys scripta elegans
Authors: Sjöströum Anne M. , Ulinski Philip S.
Published: January 2005

The dorsal lateral geniculate complex in turtles receives a bilateral, topographic projection from the retina and projects to the telencephalon. This study examined the morphology of individual retinogeniculate terminals that were filled with horseradish peroxidase by injections in the optic tract or optic tectum.

A large number of retinogeniculate terminals were successfully filled and detailed drawings were prepared of 87 terminals. Terminals were classified into three types based on the size and number of varicosities in the terminal, and (if a terminal formed a spatially restricted arbor) the volume of the arbor. Type I retinogeniculate terminals form spatially restricted, large‐volume arbors with a low density of large varicosities. Type II retinogeniculate terminals form small volume arbors with a high density of small varicosities. Type III retinogeniculate terminals, in contrast to types I and II, do not form spatially restricted arbors. Rather, they consist of sparsely branched axons that parallel the optic tract and contain scattered en passant varicosities. Plots of the distribution of different terminal types throughout the geniculate complex show that all three terminal types occur throughout the rostrocaudal and mediolateral extents of the complex. However, each terminal type has a preferential distribution with type II terminals being concentrated in the outer half of the neuropile, type I terminals in the inner half of the neuropile, and type III terminals in the cell plate. All three types can arise from axons that continue caudally to terminate in the tectum.

These findings raise the possibility that various classes of retinal ganglion cells differ in their mode of termination within the geniculate complex, but the precise relation between the three types of retinogeniculate terminals and the classes of ganglion cells remains to be determined.
Specificity of motoneuron projection patterns during development of the bullfrog tadpole (Rana catesbeiana)
Authors: Farel Paul B. , Bemelmans Sibyl E.
Published: January 2005

The pattern of connectivity between motoneurons of the lumbar lateral motor column (LMC) and hindlimb regions was examined in bullfrog tadpoles (Rana catesbeiana) over the course of larval development. The purpose of this study was to determine if a period of relatively imprecise connectivity, such has been found in the toad Xenopus laevis (Lamb, '76), could be identified. Patterns of connectivity were assessed by placing small amounts of the retrogradely transported enzyme horseradish peroxidase (HRP) into discrete hindlimb regions and mapping the locations of labeled motoneuron somata along the transverse and longitudinal axes of the LMC. The distribution of labeled motoneurons was as circumscribed in the youngest animals studied (st. IV of Taylor and Kollros, '46), before mesenchymal condensation into distinct myotubes, as in metamorphic or adult animals. This finding that the pattern of neuromuscular connectivity is as precise early in development as in mature animals is consistent with previous studies of chick hindlimb (Landmesser, '78). The relevance of these results to the hypothesis that naturally occurring cell death plays a substantial part in molding the mature pattern of neuromuscular connectivity (Lamb, '77) is discussed.
The organization of the diencephalon and the pretectum in the cichlid fish, Haplochromis burtoni
Authors: Fernald Russell D. , Shelton Linda C.
Published: January 2005

Although teleost fish comprise the largest vertebrate radiation, surprisingly little is known about the structure and development of their central nervous systems. Since teleosts are being used much more frequently as model systems in neurobiological research, particularly in understanding visual function, detailed information is needed about central nervous system structures and interconnections. By using the Bodian method with Nissl counterstaining we have analyzed the major nuclei in the diencephalon and pretectum of a cichlid fish, Haplochromis burtoni, which is dependent on vision for its survival. Although our results are broadly comparable with those from other teleost species, there are clear differences, particularly among the visual nuclei. By using animals of a range of sizes to confirm our descriptions we were able to identify possible developmental relationships among several nuclei.
Multiple opioid peptides and the modulation of pain: Immunohistochemical analysis of dynorphin and enkephalin in the trigeminal nucleus caudalis and spinal cord of the cat
Authors: Cruz Lilia , Basbaum Allan I.
Published: January 2005

Using immunocytochemistry we have identified important differences in the distribution of immunoreactive dynorphin and enkephalin cells and terminals in the trigeminal nucleus caudalis and in the spinal dorsal horn of the cat. Dynorphin immunoreactive processes are more closely associated with those regions of cord that process nociceptive information, specifically laminae I and V. Enkephalin neurons and terminals are more widespread. Based on the staining pattern with an antiserum to the octapeptide‐met‐enkephalin‐arg‐gly‐leu, we suggest that the dense enkephalin terminal immunoreactivity in the inner part of the substantia gelatinosa derives from cells in lamina III. There are also significant differences in the anatomical relationship of the two opioid peptides with the organization of parasympatheic autonomic preganglionic neurons. The functional significance of these observations must await physiological analysis; nevertheless, it is almost certain that differences will be found and that these will be important in understanding the mechanisms through which exogenous opiates and a variety of descending control systems exert their effects on spinal cord neurons.
The avian somatosensory system. I. Primary spinal afferent input to the spinal cord and brainstem in the pigeon (Columba livia)
Authors: Wild J. Martin
Published: January 2005

The process of transganglionic transport was used to determine the pattern of primary afferent projections to the spinal cord and brainstem in the pigeon by (1) applying horseradish peroxidase (HRP) to various peripheral nerves in the leg or wing, (2) by injecting HRP‐lectin into feather follicles of the wing or tail, and (3) by injecting HRP‐lectin into various muscles of the leg or wing.

In the spinal cord major peripheral nerves were represented heavily throughout the dorsal horn laminae but sparsely in more ventral laminae. The representations of these different nerves tended to be located in different mediolateral regions of the dorsal horn. Cutaneous nerves and feather follicles were represented predominantly in laminae I and II, and different sets of follicles were represented in different mediolateral regions of these laminae. Afferent labelling from muscles of the leg and wing was located in the lateral portion of the dorsal horn, predominantly in laminae I, II, and IV.

In the caudal medulla the representation of the leg within the gracile nucleus was medial to and separate from that of the wing within the cuneate nucleus (Cu). The wing representation, however, extended laterally throughout the external cuneate nucleus (CuE) and lateral regions of the descending trigeminal tract. There was less evidence of separation of the limb representations at more rostral medullary levels where they both occupied predominantly CuE. Afferent labelling from cutaneous nerves and feather follicles was distributed lightly throughout Cu and CuE, and from muscles of both limbs primarily throughout CuE. There was also a small but specific projection from the limbs to the nucleus of the solitary tract, and from the wing to the principal sensory trigeminal nucleus.

These results are discussed within a comparative context with a view to highlighting the similarities and differences in the pattern of primary afferent central projections in different vertebrates.
Chemical and electrical synapses between photoreceptors in the retina of the turtle, Chelydra serpentina
Authors: Owen W. Geoffrey
Published: January 2005

Electron microscopic observation of the distal retina of the turtle, Chelydra serpentina revealed that photoreceptors contact each other by means of a variety of junctions. The synaptic terminals of the primary and accessory members of a double cone invariably make punctate contact with each other distal to the basal surfaces. This type of contact was only rarely seen between the synaptic terminals of single photoreceptors. Photoreceptor telodendria which emanate from the basal surface of the synaptic terminal and ramify laterally for up to 40 μm in the outer plexiform layer give off branchlets which contact the terminals of both rods and cones. These contacts resemble superficial basal junctions and can be of the “wide‐gap” or “narrow‐gap” type. In cones the branchlets of the telodendria sometimes make a “distal junction” with one of the lateral elements of a synaptic dyad. Gap junctions were not found between the fins radiating from the myoids of adjacent receptors but were seen to occur en passant between photoreceptor telodendria in the outer plexiform layer. These junctions, though small, are probably of sufficient size to account for the rod‐rod coupling observed physiologically in this retina.

A prominent organelle resembling a synaptic lamella was occasionally seen in processes making contact with photoreceptors. These processes were identified as bipolar cell dendrites.
Retinal neurochemistry of three elasmobranch species: An immunohistochemical approach
Authors: Brunken William J. , Witkovsky Paul , Karten Harvey J.
Published: January 2005

We surveyed retinas of Raja erinacea, Mustelus canis, and Squalus acanthias for neurotransmitter substances by using antisera directed against the substances themselves or against their synthesizing enzymes. Both the peroxidase‐antiperoxidase (PAP) and indirect fluorescent techniques were employed to visualize the primary antisera. In all three species positive results were obtained with antisera directed against tyrosine hydroxylase (TOH), glutamic acid decarboxylase (GAD), serotonin (5‐HT), and leucine enkephalin (Lenk). Antisera directed against glucagon, neurotensin, beta‐endorphin, vasoactive intestinal peptide, or bombesin failed to show any specific staining.

Immunoreactivity was located in amacrine, interplexiform, and horizontal cells as well as in axons of the optic fiber layer. The four antisera labelled different amacrine cell classes, distinguished on the bases of perikaryal morphology and the distribution of cell processes in the inner plexiform layer (IPL). Amacrine cells that labelled with the same marker were seen to have different morphologies in the species studied. Thus, TOH‐like immunoreactivity was distributed in layers 1, 3, and 5 of the IPL in Mustelus but only in layers 1 and 3 in Raja retina. GAD‐like immunoreactivity was found diffusely over all layers of the IPL in Raja, but in Mustelus it was confined primarily to layers 1, 3, and 5 of the IPL. Lenk‐ and 5‐HT‐like immunoreactivities showed similar species variations.

Two neurochemical classes of interplexiform cell were identified in this study. In Mustelus GAD‐like and Lenk‐like immunoreactive interplexiform cells were seen whereas in Raja only GAD‐positive interplexiform cells were detected. In Squalus no unequivocal demonstration of any interplexiform cell was made with these antisera.

The GAD antiserum also labelled a subset of the horizontal cells in the dorsal retina of Raja. TOH and 5‐HT‐antisera labelled axons in the optic fiber layer of all three species but reactive ganglion cell perikarya were not identified.
Anatomical studies on the nucleus reticularis tegmenti pontis in the pigmented rat. I. Cytoarchitecture, topography, and cerebral cortical afferents
Authors: Torigoe Yasuhiro , Blanks Robert H. I. , Precht Wolfgang
Published: January 2005

The nucleus reticularis tegmenti pontis (NRTP) is a precerebellar reticular nucleus that has been found to be related to cerebropontocerebellar pathways and, more recently, to eye movements. The present study investigates the cytoarchitecture, the topography, and the cerebral cortical projections to the NRTP in the pigmented rat. The cytoarchitecture and topography of the NRTP was determined by examination of Nissl‐stained material sectioned in the transverse and sagittal planes. Two cytoarchitectonically distinct portions of the NRTP are apparent; a central subdivision (NRTPc) composed of large multipolar, small spherical, and fusiform neurons, and a pericentral subdivision (NRTPp) composed of loosely packed small fusiform and spherical neurons. The NRTPc is located dorsal to the medial lemniscus and pyramidal tracts over the caudal two‐thirds of the pons. It extends caudodorsally to the region just rostral and ventral to the abducens nucleus. The NRTPp is adjacent to the lateral margins of the NRTPc, rostrally, and lies ventral to the caudal portions of the NRTPc. Large injections of horseradish peroxidase (HRP) were made into the cerebellum in order to determine the degree to which each subdivision of the NRTP contributes to the cerebellar projection. A high percentage of NRTPc neurons and a lower percentage of NRTPp neurons were labeled. These differences in labeling density and neuronal morphology noted above confirm the appropriateness of subdividing the NRTP into central and pericentral subdivisions.

The cerebral cortical afferents to the NRTP were examined by placing small iontophoretic injections of HRP into the NRTPc and NRTPp. A systematic examination of all cortical areas revealed that the HRP‐labeled neurons are entirely localized within pyramidal layer V of three major cortical areas: (1) the ipsilateral prefrontal cortex (Brodrnann areas 8, 8a, 11, and 32); (2) the ipsilateral motor and somatosensory cortices (Brodmann areas 2, 4, 6, and 10), and (3) the bilateral cingular cortex (Brodmann areas 24a, 24b, 29c, and 29d). By far, the heaviest cortical labeling with HRP injections into the medial NRTPc is within the cingular cortex that may, in the rat, be homologous to the frontal eye field of the cat and monkey. In contrast, injections involving the lateral NRTPc or the NRTPp produced labeling within wide regions of the cortex with the greatest number in the somatomotor cortex. A comparison of these data reveals a topographic organization for the cortical afferents to the NRTP in rat: Namely, the medial areas of the NRTP receive projections from phylogenetically older regions of the cerebral cortex, whereas the lateral areas of the NRTP are more closely related to neocortical regions.