bluuebunny/crossref_metadata_2025 huggingface dataset:
Fine structure of histaminergic neurons in the caudal magnocellular nucleus of the rat as demonstrated by immunocytochemistry using histidine decarboxylase as a marker
Authors: Hayashi Hideyuki , Takagi Hiroshi , Takeda Noriaki , Kubota Yoshiyuki , Tohyama Masaya , Watanabe Takehiko , Wada Hiroshi
Published: January 2005

The morphology of histamine‐containing neurons in the caudal magnocellular nucleus was light and electron microscopically examined by means of peroxidase‐antiperoxidase (PAP) immunocytochemistry with histidine decarboxylase (HDC) as a marker. HDC‐like immunoreactive (HDCI) neurons had large (25–30 μm in diameter) perikarya from which two to four primary dendrites arose. The perikarya had a nearly round nucleus and well‐developed Golgi apparatus in addition to a large number of mitochondria and rough endoplasmic reticulum. Immunoreactive endproducts were found diffusely throughout the perikarya, dendrites, and axons. HDCI neurons made synaptic contact with nonreactive axon termminals on the perikarya and dendrites. In addition, the HDCI neurons very frequently formed puncta adherentia with neuronal elements, either HDCI or nonreactive, or glial cells. Most of the HDCI axon terminals serially observed under electron microscopy did not exhibit typical synaptic contact in the caudal magnocellular nucleus. These findings suggest the nonsynaptic release of histamine in the caudal magnocellular nucleus.
The cortical projection of the basolateral amygdaloid nucleus in the rat: A retrograde fluorescent dye study
Authors: Sripanidkulchai K. , Sripanidkulchai B. , Wyss J. M.
Published: January 2005

The fluorescent dye, retrograde labeling technique was used to determine the extent of the projection from the basolateral nucleus of the amygdala to the neocortex in the rat. Each rat received a single cortical injection of fast blue, and in one‐half of the animals, a subsequent injection of nuclear yellow was placed in a different cortical region. An analysis of the results demonstrates that the projection to the midline cortex arises in the medial neurons within the caudal two‐thirds of the basolateral nucleus. This projection is directed to the anterior cingulate cortex, but not to the posterior cingulate cortex. The primary motor cortex receives a basolateral amygdala projection which originates from neurons in two areas, (1) the medial part of the anterior one‐third of the nucleus and (2) the center (in the lateral to medial axis) portion of the posterior two‐thirds of the nucleus. The latter neurons are situated lateral to the neurons projecting to the cingulate cortex. Somatosensory cortex injections label many fewer basolateral nucleus neurons than do motor cortex injections, but these neurons are located in a position similar to that of those labeled by motor cortex injections. Finally the gustatory cortex, which lies just dorsal to the rhinal sulcus, receives a basolateral projection from neurons in the lateroventral one‐half of the basolateral nucleus. These results demonstrate that the basolateral nucleus gives rise to a rather widespread and topographically organized projection to the anterior half of the neocortex of the rat.
The trajectory of mitral cell axons in the rabbit olfactory cortex revealed by intracellular HRP injection
Authors: Ojima Hisayuki , Mori Kensaku , Kishi Kiyoshi
Published: January 2005

The projection of the axon and axon collaterals of mitral cells to the olfactory cortex was studied in the rabbit by intracellular staining with horseradish peroxidase (HRP). The stained mitral cell axons were reconstructed from the soma to the most caudal portion of the anterior piriform cortex (aPC). Single mitral cells projected to cytoarchitectonically different areas of the olfactory cortex, i.e., the anterior olfactory nucleus (AON), and the aPC, the olfactory tubercle (OT). All the stained mitrall cells projected to both the AON and the aPC, and about one‐fourth of the mitral cells projected to the OT. At the surface of the AON and the aPC, the main axon running in the lateral olfactory tract (LOT) gave off several thin collaterals at various intervals. The collaterals did not project evenly in each area but typically formed patchy terminal arbors which tended to be elongated anteroposteriorly. In both the AON and the aPC, each single mitral cell formed several terminal arbors in layer Ia. The axon collaterals innervating the OT showed two types of projection patterns. One type of collateral was emitted from the main axon within the olfactory bulb, coursed through the ventromedial portion of the olfactory peduncle without joining the main mass of the LOT and terminated mainly in the medial portion of the OT. The other type of collateral emerged from the main axon in the LOT, coursed medioposteriorly, and projected to the lateral portion of the OT.

Although individual mitral cells projected to several parts of the olfactory cortex, the fact that they made dense terminal arbors in specific places in each area suggests that the bulbocortical connections are not diffuse but highly selective.
The neuronal endoplasmic reticulum: Its cytochemistry and contribution to the endomembrane system. II. Axons and terminals
Authors: Broadwell Richard D. , Cataldo Anne M.
Published: January 2005

The morphology and cytochemistry of the endoplasmic reticulum (ER) in axons and terminals of a number of different types of neurons in brains from mice were investigated ultrastructurally. The neurohypophysis received particular attention because the morphology and enzyme cytochemical activities of many of the preterminal swellings of hypothalamoneurohypophysial axons are altered by chronic salt‐stress. Membrane contrast and enzyme cytochemical staining techniques were employed to characterize the axonal reticulum and to determine if organelles representing the lysosomal system in the axon and the tubular profiles participating in the anterograde axonal transport of native horseradish peroxidase (HRP) are associated with the ER. Potential enzyme cytochemical markers for the axonal ER included glucose‐6‐phosphatase (G6Pase), thiamine pyrophosphatase, nucleoside diphosphatase, and acid hydroxylase activities. The anterograde transport of HRP was analyzed in undamaged hypothalamoneurohypophysial neurons and in facial and hypoglossal motoneurons of mice receiving the protein in the lateral cerebral ventricle.

The ER pervaded the axon and appeared as parallel, 20–40‐nm‐wide tubules interconnected by oblique anastomoses. Membrane thickness of the axonl reticulum measured 60–100 Å, which is similar to that of the perikaryal ER. Enzyme cytochemical activities associated with the ER or lysosomes were not conspicuous in axons and terminals under normal conditions but became prominent in some axons and preterminal swellings manifesting an autophagic appearance within neurohypophyses from salt‐stressed mice. Only G6Pase activity was a marker for the ER in these axons and preterminals. Many ER profiles in non‐incubated sections and in G6Pase cytochemical preparations of salt‐stressed neurohypophyses were wrapped around or interspersed among secretory granules, multilamellar bodies, and vacuoles that may represent forms of lysosomes involved in autophagy and crinophagy. Acid hydrolase activities were localized within the vacuoles as well as within 80–130‐nm‐wide, blunt‐ended tubules in pituitary stalk axons; similar reactive tubules were confluent with large secondary lysosomes in neurosecretory cell bodies and may be derived from these lysosomes. Morphologically identical tubules transporting HRP in the anterograde direction were observed only in the salt‐stressed hypothalamo‐neurohypophysial neuron. The HRP‐positive tubules very likely are affiliated with the lysosomal system.
Uptake of 3H‐glycine in the outer plexiform layer of the retina of the toad Bufo marinus
Authors: Kleinschmidt Jochen , Yazulla Stephen
Published: January 2005

The uptake of 3H‐glycine in the retina of the toad, Bufo marinus, was investigated by light and electron microscopical autoradiography. Uptake of 3H‐glycine was very prominent in large cell bodies in the inner nuclear layer as well as in discrete clusters in both the outer plexiform layer (OPL) and the inner plexiform layer. This pattern is similar to that described for 3H‐glycine‐aecumulating putative interplexiform cells in goldfish, frog, and Xenopus retinas. Electron microscopical autoradiography of the OPL revealed large, grain‐containing varicosities which had electron‐lucent cytoplasm and contained both small, agranular and large, dense‐core vesicles. The varicosities made extensive en passant and spine synapses in the OPL. Definitive identification of their postsynaptic targets was not achieved. However, autoradiographic analysis with 3H‐GABA uptake as well as electrophysiological evidence suggests that axons but not cell bodies or dendrites of 3H‐GABA‐accumulating horizontal cells (H1 cells) are postsynaptic targets of the varicosities. The presence of dense‐core vesicles in the varicosities suggested co‐occurrence of glycine and a biogenic amine or neuropeptide. The indirect immunofluorescence technique was used to determine whether any such substances were present in the OPL of the toad retina. However, no specific labeling was found in the OPL for any of 19 substances tested. The extensive synaptic output provided by glycine‐accumulating varicosities in the toad OPL may indicate an important role of glycine in the synaptic function of the distal toad retina. We suggest that these varicosities derive from a presumably glycinergic interplexiform cell.
Gangliosides stimulate protein synthesis, growth, and axon number of regenerating limb buds
Authors: Maier C. Eberhardt , Singer Marcus
Published: January 2005

When a newt limb is amputated and begins to regrow, regenerating axons exert a neurotrophic influence on the limb regeneration process. Previous studies have shown that direct manipulation of limb nerves, by electrical stimulation or a conditioning lesion, elevates protein synthesis, increases neurotization and accelerates growth of the limb bud. Since exogenously supplied gangliosides accelerate axonal sprouting in regenerating nerves, we wanted to know whether gangliosides would similarly affect limb regeneration. To test this, regrowing limb buds were either infused with or immersed into gangliosides, or animals were injected intraperitoneally with gangliosides. Infused gangliosides elevated protein synthesis in limb buds 15% and increased the number of axons in limb buds 45% by 6 hours after infusion. Regenerating limb bud morphogenesis was initiated 3–4 days earlier in animals receiving i.p. injections of gangliosides every 12 hours. Similarly, limbs immersed daily in gangliosides began regrowth sooner than contralateral controls and this advantage was maintained throughout the period of observation. These findings indicate that treatment with gangliosides has a salutary effect on limb regeneration.
A comparative study of neck muscle motor neurons in a cricket and a locust
Authors: Honegger Hans‐Willi , Altman Jennifer S. , Kien Jenny , Müller‐Tautz Rosemarie , Pollerberg Elisabeth
Published: January 2005

The gross morphology of the neck muscles of a cricket (Gryllus campestris) and their innervation are described and compared with a locust (Schistocerca gregaria) (Figs. 1,2). The motor neurons innervating the neck muscles were stained in crickets and locusts with cobalt chloride introduced via the nerve endings in the muscle. The two species show overall similarities, not only in position of the neck motor neurons in suboesophageal, prothoracic, and mesothoracic ganglia (Table 1) but also in motor neuron morphology (Figs. 4–12). However, muscle 60 in the cricket is innervated by a unique motor neuron with its axon in prothoracic nerve 3, instead of sharing motor neurons in suboesophageal nerve 8 and mesothoracic nerve 1 with muscle 59, as in locust. Muscle 62 has the same attachments and innervation with similar motor neurons in cricket and locust but a different mechanical function in the two species. The findings are discussed with respect to possible segmental homologies and to the origins of the muscles as either dorso‐ventral or longitudinal. As several muscles share the same motor neurons, we suggest that neck muscle function be described in terms of “behavioural units of action”.
Regional specializations in the eye of Aplysia, a neuronal circadian oscillator
Authors: Herman K. G. , Strumwasser F.
Published: January 2005

The eye of the opisthobranch mollusc, Aplysia californica, contains a neuronal circadian oscillator system as well as a photoreceptor system. The retina contains five classes of receptors, several of which are described for the first time in this paper, and two types of neurons. The most conspicuous photoreceptor has long microvilli and is densely packed with small vesicles. The other four receptor types bear both microvilli and cilia and lack densely packed vesicles. Because of their small size, these four receptors occupy only a small fraction of the retinal area, but numerically they account for about half of the receptors. There are marked differences between the dorsal and ventral portions of the eye of Aplysia. The optic nerve head and associated bundles of axons within the retina form a boundary between two anatomically distinct regions of the eye. The microvillous photoreceptor and one of the receptors bearing both microvilli and cilia are found throughout the eye. The other three receptor types are restricted to the region ventral to the optic nerve head. One type of neuron, which has been shown in other studies to produce compound action potentials whose frequency varies with a circadian rhythm, is also found only ventral to the optic nerve head and associated axon bundles. There are also marked regional variations in cellular dimensions. The rhabdom originating from the microvillous photoreceptors is thickest in the dorsal and central retina, and the cross‐sectional areas of these photoreceptors are largest dorsally. The pigmented layer is also much thicker in the dorsal retina. No other molluscan eye has been reported to have as many receptor types as Aplysia, nor has restriction of a receptor or neuronal type to a limited area been described. Regional variations in cellular dimensions have been reported previously primarily in the advanced cephalopod eyes. The significance of these unusual features is discussed in relation to both the visual properties of the eye and the circadian oscillator it contains.
A laminar analysis of the number of round‐asymmetrical and flat‐symmetrical synapses on spines, dendritic trunks, and cell bodies in area 17 of the cat
Authors: Beaulieu Clermont , Colonnier Marc
Published: January 2005

The number of synapses per unit volume of tissue (Nv) has been estimated in individual laminae of the binocular and monocular regions of area 17 in six adult cats by using a method of size‐frequency distribution. Separate estimates were obtained for RA synapses (containing round vesicles associated with asymmetric membrane differentiations) and for FS synapses (containing flat vesicles associated with symmetric membrane differentiations). For the total cortical thickness, the Nv of all synapses is not statistically different between binocular (286 million per mml3) and monocular (281 million) regions, nor is it different between the two regions for any of the laminae. Eighty‐four percent of synapses are of the RA type. of those, 79% are found on dendritic spines, 21% on dendritic trunks, 0.1% on somata. FS synapses represent 16% of the total, with 31% of them on spines, 62% on dendritic trunks, and 7% on somata. The ratio of RA to FS synapses is kept relatively constant throughout the layers. A two‐way analysis of variance shows no difference in the Nv of either RA or FS synapses in the two regions nor in the Nv of RA synapses between cats. It does, however, clearly demonstrate (p < 0.001) interindividual differences for FS synapses. These variations between individual cats may be due to differences in age, breed, or environmental factors. In contrast to the relative uniformity of the Nv of synapses between regions, the number of each type under 1 mm2 of cortical surface is 33% higher in the binocular region. This is due mainly to the greater thickness of the binocular region.
Anatomy of brain alpha1‐adrenergic receptors: In vitro autoradiography with [125I]‐heat
Authors: Jones Leslie Sargent , Gauger Lisa L. , Davis James N.
Published: January 2005

Much useful information on the localization of alpha1‐adrenergic binding sites has been gained by using tritiated radioligands for in vitro autoradiography. However, the iodinated alpha1‐adrenergic antagonist HEAT (([2‐β (4‐hydroxyphenyl)‐ethylaminomethyl)‐tetralone], BE 2254), a radioligand with high affinity and specificity, provides autoradiographs with a higher signal to noise ratio. This has allowed us to describe the anatomy of these binding sites in much greater detail than previously possible.

Regions showing the highest levels of binding include external plexiform layer of the olfactory bulb, layers Va and Vc of frontoparietal cortex, lateral and central amygdaloid nuclei, thalamus, and inferior olive. Other regions were generally less intensely labeled, with the least evidence of labeling in white matter, such as corpus callosum. Some regions (e.g., hippocampus) had only moderate labeling, but the binding appeared in a discrete pattern that reflected the functional organization of the structure.

Although the [125I]‐HEAT binding sites were distributed in a pattern similar to that previously reported for [3H]‐WB 4101 and [3H]‐prazosin, the anatomical detail seen with the iodinated ligand is greater. As a result, an association of alpha1‐adrenergic antagonist binding sites with specific layers in the cortex and with some catecholamine‐containing nuclei in the brainstem, such as the locus coeruleus, have been seen for the first time.
Afferent influences on brain stem auditory nuclei of the chicken: Neuron number and size following cochlea removal
Authors: Born Donald E. , Rubel Edwin W.
Published: January 2005

The consequences of cochlea removal on neuron number and soma cross‐sectional area were examined in the second order auditory nucleus (n. magnocellularis) of chickens. Both the age of the subjects at the time of cochlea (basilar papilla) removal (1–66 weeks) and the survival period (1–45 days) were varied. Neuron number and soma cross‐sectional area were determined from Nissl stained sections. Additional material was processed to examine the relationship of ganglion cell loss to changes in n. magnocellularis.

Neuron number decreased by 25–30% and soma cross‐sectional area decreased by 10–20% ipsilateral to the cochlea removal in chickens operated on during the first 6 weeks after hatching. In contrast, in chickens operated on at 66 weeks posthatch neuron number decreased less than 10% and there was no change in soma area. The changes were rapid, being nearly complete 2 days after cochlea removal. An initial change (1 and 2 days after surgery) observed in animals operated on up to 6 weeks posthatch was the presence of a large number of neurons in which no Nissl substance could be detected. These results demonstrate an age‐dependent change in the susceptibility of NM neurons to deafferentation. This change is not temporally related to other measures of functional maturation of the auditory system.
Autoradiographic localization of estrogen and androgen receptors in the sexually dimorphic area and other regions of the gerbil brain
Authors: Commins Deborah , Yahr Pauline
Published: January 2005

Autoradiography was used to localize sex hormone‐accumulating cells in the gerbil brain. Some areas had a high density of both androgen and estrogen receptors. These areas included the lateral septum, the bed nucleus of the stria terminalis, the medial and cortical amygdaloid nuclei, the medial preoptic area (MPOA), the arcuate nucleus, the ventromedial hypothalamus, and the periventricular central gray. This distribution of hormone receptors agrees closely with that seen in other mammals. In contrast to what has been reported for other species, the distribution of estradiol‐accumulating cells in the gerbil MPOA is different in males and females. Estradiol uptake in the posterior MPOA followed the morphology of a sexually dimorphic area (SDA) and was therefore sexually dimorphic. Moreover, the percentage of SDA cells that accumulated estradiol appeared to be higher in males than in females. The pattern of androgen accumulation also followed the morphology of the SDA but differed from the pattern of estrogen accumulation in one way. The uptake of 5α‐dihydrotestosterone in the SDA pars compacta (pc), a component of the SDA, was much greater than in the rest of the SDA. This was not true for estradiol. Since most females lack the SDApc, androgen uptake in the gerbil SDA may also be sexually dimorphic. Androgen uptake was more widespread than estrogen uptake in the brainstem. Brainstem nuclei that accumulated 5α‐dihydrotestosterone included the locus ceruleus, the dorsal raphe, the hypoglossal nucleus, the area postrema, the nucleus of the solitary tract, and the dorsal nucleus of the vagus.
Sensory innervation of periodontal ligament of rat molars consists of unencapsulated Ruffini‐like mechanoreceptors and free nerve endings
Authors: Byers Margaret R.
Published: January 2005

The trigeminal ganglion (TG) of adult rats was injected with 3H‐amino acids to label periodontal receptors by axonal transport; 20–24 hours after injection, samples of molar ligament were prepared for autoradiography and electron microscopy. Four types of neurites labeled from TG were found in the avascular ligament fiber regions: (1) large, complex, Ruffini‐like endings, lacking a capsule, but with finger extensions touching ligament collagen; (2) smaller Ruffini‐like endings, lacking a capsule and neural fingers; (3) free bundles of unmyelinated axons; and (4) free, small, myelinated axons. The vascular channels plus associated loose connective tissue that perforate the ligament contained labeled preterminal ensheathed axons, small Ruffini endings, and free unmyelinated or small myelinated axons. The incidence of labeled endings was about 5 × greater next to the lower third of the root than in the upper two‐thirds or beneath the root The TG myelinated axons (diameter range 2–15 μm) entered the ligament in sheathed nerve bundles; these branched to form numerous small preterminal axons that were surrounded by a periaxonal fluid space and a perineurial sheath. Terminal axons branched from nodes of Ranvier, left the preterminal chamber, and followed an extended branching course through the collagen fibers. Large, complex Ruffini‐like endings had numerous mitochondria and were partially covered by special lamellar Schwann cells and complex basal lamina; vesicles and multivesicular bodies were found near exposed regions of the receptor. Smaller Ruffini‐like endings lacked neural fingers and had a simpler structure and less elaborate Schwann cells. The structure of Ruffini‐like endings was highly varied; thus a structural continuum may exist from the largest, most complex to the smallest, simplest Ruffini‐like receptor. The TG unmyelinated axons entered the ligament in ensheathed bundles; they then branched into free bundles that were found in the avascular ligament or near blood vessels. No encapsulated receptors were found.
Reflex connections of the facial and vagal gustatory systems in the brainstem of the bullhead catfish, Ictalurus nebulosus
Authors: Morita Yasuhiro , Finger Thomas E.
Published: January 2005

The primary gustatory sensory nuclei in catfish are grossly divisible into a vagal lobe and a facial lobe. In this study, the reflex connections of each gustatory lobe were determined with horseradish peroxidase (HRP) tracing methods. In addition, in order to determine the loci and morphology of the other brainstem cranial nerve nuclei, HRP was applied to the trigeminal, facial, glossopharyngeal, or vagus nerve.

The sensory fibers of the facial nerve terminate in the facial lobe. The facial lobe projects bilaterally to the posterior thalamic nucleus, superior secondary gustatory nucleus, and medial reticular formation of the rostral medulla. The facial lobe has reciprocal connections with the lobobulbaris, medial reticular formation of the rostral medulla, descending trigeminal nucleus, medial and lateral funicular nuclei, and the vagal lobe, ipsilaterally; and with the facial lobe contralaterally. In addition, the facial lobe receives inputs from the raphe nuclei, from a pretectal nucleus, and from perilemniscal neurons located immediately adjacent to the ascending gustatory lemniscal tract at the level of the trigeminal motor nucleus.

The gustatory fibers of the vagus nerve terminate in the vagal lobe, while the general visceral sensory fibers terminate in a distinct general visceral nucleus. The vagal lobe projects ipsilaterally to the superior secondary gustatory nucleus, lateral reticular formation, and n. ambiguus; and bilaterally to the commissural nucleus of Cajal. The vagal lobe has reciprocal connections with the ipsilateral lobobulbar nucleus and facial lobe, In addition, the vagal lobe receives input from neurons of the medullary reticular formation and perilemniscal neurons of the pontine tegmentum.

In summary, the facial gustatory system has connections consonant with its role as an exteroceptive system which works in correlation with trigeminal and spinal afferent systems. In contrast, the vagal gustatory system has connections (e.g., with the n. ambiguus) more appropriate to a system involved in control of swallowing. These differences in central connectivity mirror the reports on behavioral dissociation of the facial and vagal gustatory systems.
Innervation of the complexus (“hatching”) muscle of the chick
Authors: Gross Gayle H.
Published: January 2005

The complexus muscle of avians, also known as the “hatching” muscle, is notable for the dramatic, transient pseudohypertrophy which it undergoes around the time of hatching. The muscle is believed to be involved in specific dorsal and lateral head movements used for hatching. Innervation of the complexus muscle was studied in the hatchling chick by using horseradish peroxidase (HRP). HRP injections of the muscle showed that motor innervation arose, as expected, from the cervical motor column (C1–C6). However, additional innervation was also discovered; the spinal accessory nucleus (column of von Lenhossek), the nucleus supraspinalis, and the dorsal and ventral facial motor nuclei all contributed efferents to the hatching muscle. This observation constitutes the first description or dual innervation of a neck muscle by nuclei in both the brain and spinal cord. In addition, transganglionic transport of HRP revealed labelled primary afferent fibers from the hatching muscle ascending in the dorsal columns and terminating extensively within the vestibular complex, especially on the principal cells of the tangential nucleus. The tangential nucleus itself undergoes synaptic changes at the time of hatching. Possible functional relations between the tangential nucleus and the hatching muscle are discussed.
Acoustic chiasm II: Anatomical basis of binaurality in lateral superior olive of cat
Authors: Glendenning K. K. , Hutson K. A. , Nudo R. J. , Masterton R. B.
Published: January 2005

The afferent projections to the lateral superior olive (LSO) were examined with horseradish peroxidase, horseradish peroxidase‐wheat germ agglutinin conjugate, 125I‐wheat germ agglutinin and tritiated leucine autoradiography, anterograde axonal degeneration, and 14C‐2‐deoxyglucose methods.

The pathway to the ipsilateral LSO orginates in the spherical cells in anteroventral cochlear nucleus. Although some of the fibers pass above the lateral nucleus of the trapezoid body, most pass below it and turn at right angles to enter the LSO either directly through its ventral, lateral, or dorsal borders, or through its ventral or dorsal hilus. They end in unpolarized terminal fields throughout the LSO. Most if not all of these fibers are true collaterals of axons continuing across the midline in the trapezoid body.

Verifying Held's (1893) finding of a major direct projection from the cochlear nucleus to the contralateral medial nucleus of the trapezoid body (MTB) and Rasmussen's ('46) finding of a major projection from the MTB to the LSO, the present results illustrate that this two‐neuron pathway probably supplies all but a very small component of the relatively direct input to the LSO from the contralateral ear. This pathway originates in the globular cells of the ventral cochlear nucleus and relays mostly though not exclusively through the “principal cells” in the more rostral parts of the MTB. It terminates mostly in perisomal endings in unpolarized fields throughout the LSO, though most heavily within the (high frequency) medial and middle limbs and less heavily in the LSO's (low frequency) lateral limb.

In addition to this indirect pathway, there is a small direct pathway to the contralateral LSO as suggested by Goldberg and Brown ('69) and Warr ('72, '82). This direct pathway to the contralateral LSO, like the direct ipsilateral pathway, probably originates in the spherical cell region of the ventral cochlear nucleus, crosses the midline in the trapezoid body, and terminates in a small circumscribed area within the LSO's ventromedial (high frequency) area.

The 2‐deoxyglucose method applied to cats in which the ipsilateral and contralateral pathways have been surgically isolated shows that each of the pathways converging on the LSO is topographically and tonotopically organized with the ipsilateral and the combined contralateral terminations in strict tonotopic register.
Rat medulla oblongata. II. Dopaminergic, noradrenergic (A1 and A2) and adrenergic neurons, nerve fibers, and presumptive terminal processes
Authors: Kalia Madhu , Fuxe Kjell , Goldstein Menek
Published: January 2005

The aim of this study was to determine the anatomical relationships between catecholaminergic neurons and cytoarchitectonically defined nuclei in the caudal medulla oblongata. Previous studies have demonstrated the existence of noradrenergic cell bodies (designated as the A1 and A2 cell groups) in the caudal medulla oblongata of the rat (Dahlström and Fuxe, '64), including the nTS. There, is no information currently available with regard to details of the distribution of these noradrenergic neurons in the functionally distinct subnuclei of the medulla oblongata. In this study the location of catecholamine‐synthesizing enzymes was examined in the serial sections of the caudal medulla oblongata of the rat: tyrosine hydroxylase (TH), dopamine‐beta‐hydroxylase (DBH), and phenylethanolamine N‐methyl transferase (PNMT). The immunoperoxidase method of Sternberger ('79) was used to demonstrate the location of immunoreactive neurons, nerve fibers, and presumptive terminal processes. This was followed by Nissl staining of the same sections to localize accurately the immunoreactivity.

Noradrenergic neurons (TH‐ and DBH‐positive and PNMT‐negative) were localized in a number of subnuclei of the nucleus of the tractus solitarius (nTS), the area postrema (ap), and in the dorsal motor nucleus of the vagus (dmnX). The distribution of these noradrenergic cells was different at different rostrocaudal levels. In addition, adrenergic neurone (TH‐, DBH‐, and PMNT‐positive) were identified dorsal to the tractus solitarius (TS), in the dorsal strip region (ds), the periventricular region (PVR), the dorsal parasolitarius region (dPSR), and the dmnX (rostral to obex). In addition, dopaminergic neurons (TH‐positive and DBH‐ and PNMT‐negative) were found in the ap and dmnX. The A1 cell group in the ventrolateral medulla consisted almost exclusively of noradrenergic neurons (TH‐ and DBH‐positive and PNMT‐negative).

These results indicate that in the rat the A2 cell group is a mixed population of catecholaminergic neurons that are localized in well‐defined regions of the dorsal medulla oblongata. The distribution of these neurons is very specific both in terms of rostrocaudal levels and cytoarchitectonic subdivisions of regions of the medulla known to be involved in central autonomic control. This supports the hypothesis that monoaminergic neurons in the dorsal medulla play important roles in the central regulation of visceral function.
Mapping increased glycogen phosphorylase activity in dorsal root ganglia and in the spinal cord following peripheral stimuli
Authors: Woolf Clifford J. , Chong Mun Seng , Rashdi Tabassam A.
Published: January 2005

A histochemical technique has been used to map the distribution and the relative proportion of the active and inactive form of the enzyme glycogen phosphorylase in the primary afferent cell bodies of lumbar dorsal root ganglia and within the lumbar spinal cord of the rat. The glycogen phosphorylase was found to be present in large and small diameter primary afferent cell bodies and in the grey matter of the spinal cord, except in lamina 2. Most of the glycogen phosphorylase in control rats was in the inactive form. Peripheral innocuous mechanical and thermal stimuli failed to alter the activity of glycogon phosphorylase in the lumbar spinal cord, but noxious mechanical, chemical, and thermal stimuli when applied to the hindlimb of decerebrate rats increased the enzyme activity in the ipsilateral dorsal horn within 10 minutes. The number of primary afferent cell bodies with active glycogen phosphorylase also increased. These changes are likely to be due to the conversion of the inactive “b” form of the enzyme to the active “a” form under the influence of a calcium or cyclic AMP activated phosphorylase b kinase. Pentobarbitone anaesthesia diminished but did not completely suppress the noxious stimulus‐evoked glycogen phosphorylase activity changes.

Graded electrical stimulation of the sciatic nerve was performed to simulate the effects of the peripheral noxious stimuli in a controlled fashion. Stimulation at a strength that activated only large myelinated afferents produced no greater effect on the distribution of the active form of the enzyme in the dorsal horn than that produced by exposure of the nerve, but stimulation of the thin myelinated A‐delta afferents and unmyelinated C‐fibres produced a widespread increase in glycogen phosphorylase activity in the spinal cord and in the L4 dorsal root ganglion. The increased activity could be detected after stimulation for as short a period of time as 5 minutes.

The mechanisms underlying the stimulus‐evoked increase in glycogen phosphorylase activity in the spinal cord and dorsal root ganglia are not yet known, nor have we positively established which elements in the spinal cord, neurones, or glia are responsible for the changes in the glycogen phosphorylase activity. Nevertheless, it is clear that the neural activity generated by certain types of high threshold input is associated with the activation of glycogen phosphorylase, and this may be a useful tool for studying the spatial distribution of some activity‐related changes in the nervous system. The technique may also help elucidate those circumstances where glycogen reserves are used as an energy source by nervous tissue.
Sensory nerve endings of the incisive papilla of rat hard palate studied by peroxidase cytochemical methods
Authors: Chan Kwan Y. , Byers Margaret R.
Published: January 2005

This study utilized peroxidase cytochemical methods to survey and analyze the distribution, morphology, and functional relationship of the various components of sensory nerve endings in a focal region of the anterior hard palate (incisive papilla) of the rat. The studies included an anatomical survey of this relatively unknown oral structure, confirmation of the trigeminal origin (labeled by retrograde axonal transport of WGA‐HRP injected into the incisive papilla) of the sensory nerve endings, and a complete analysis of the distribution of these nerve endings (labeled by anterograde axonal transport of HRP or WGA‐HRP injected into the trigeminal ganglion). Three methods of fixation and two methods of cytochemical reaction were used for selection of an optimal technique for these studies. The results showed distinct patterns of peroxidase‐labeled sensory nerve endings at three regions of the incisive papilla: (a) dome region (ventral), where labeled nerve endings formed three parallel channels in association with three surface ridges; (b) chemosensory corpuscle enriched region (medial to incisive canal), where 82% of the 30–40 chemosensory corpuscles were labeled; and (c) lateral labium (lateral to incisive canal), where labeled nerve endings formed a circumscribed network guarding the orifice of incisive canal. The discrete organization of multiple sensory nerve endings in the incisive papilla of the rat may provide an easily accessible model system for various studies in sensory physiology.
The central neural connections of the area postrema of the rat
Authors: Shapiro Robert E. , Miselis Richard R.
Published: January 2005

We applied the neuroanatomical tracers cholera toxin‐horseradish peroxidase and wheat germ agglutinin‐horseradish peroxidase to investigate the neural connections of the area postrema (AP) in the rat. We find that the AP projects to the nucleus of the solitary tract (NTS) and dorsal motor nucleus of the vagus bilaterally both rostral and caudal to obex; the nucleus ambiguus; the dorsal aspect of the spinal trigeminal tract and nucelus and the paratrigeminal nucleus; the region of the ventrolateral medullary catecholaminergic column; the cerebellar vermis; and a cluster of structures in the dorsolateral pons which prominently include a discrete set of subnuclei in the lateral parabrachial nucleus. The major central afferent input to the area postrema is provided by a group of neurons in the paraventricular and dorsomedial hypothalamic nuclei whose collective dendrites describe a horizontally oriented plexus which encircles the parvocellular nucleus of the hypothalamus bilaterally. In addition, the caudal NTS may project lightly to the AP. The lateral parabrachial nucleus provides a very light input as well. These connections, when considered in the context of the known vagal afferent input and reduced blood‐brain barrier of AP, place this structure in a unique position to receive and modulate ascending interoceptive information and to influence autonomic outflow as well.
Connections of the lobus inferior hypothalami of the clearnose skate Raja eglanteria (chondrichthyes)
Authors: Smeets Wilhelmus J. A. J. , Boord Robert L.
Published: January 2005

The afferent and efferent connections of the lobus inferior hypothalami of the clearnose skate were demonstrated by the anterograde and retrograde transport of horseradish peroxidase. The main source of afferents is from the midbrain tegmentum and telencephalon. The major midbrain input is from cells of the ipsilateral nucleus tegmentalis laterals and the caudal tegmental area. Another prominent, mostly ipsilateral, projection arises from nucleus F of the isthmic region. A few labeled cells also occur in the nucleus interpeduncularis, nucleus raphes superior, and lateral reticular formation. Afferents from the telencephalon arise from cells of the area preoptica, area superficialis basalis, striatum, nucleus septalis lateralis, and area subpallialis 1. Of the pallial structures, the pallium mediale and anterior as well as posterior subdivisions of the pallium dorsale pars centralis appear to have strong projections to the inferior lobe.

Efferent connections of the inferior lobe consist of ascending and descending pathways. Fibers of the main ascending efferent pathway course within the basal forebrain bundle and distribute to subpallial areas. The descending efferent pathways course within the tractus lobobulbaris and tractus lobocerebellaris. Of these, the former is traceable to the level of the facial motor nucleus, issuing fibers enroute to the midbrain tegmentum and to the lateral reticular formation. The lobocerebellar tract courses dorsolateral to the lobobulbar tract, and its fibers terminate within the ipsilateral granular ridge of the rostral pole of the cerebellar corpus.

There appears to be a topological organization of the inferior lobe connections. In general, pallial areas project mainly to the lateral subdivision of the inferior lobe nucleus at midlobic levels, whereas connections with the brainstem arise from or terminate within the dorsal and intermediate subdivisions at midlobic as well as caudal levels. The widespread ascending and descending connections indicate that the hypothalamic inferior lobe of the clearnose skate is a major relay center between the telencephalon and brainstem.
Multiple vibrissae sensory regions in rat cerebellum: A (14C) 2‐deoxyglucose study
Authors: Sharp Frank R. , Gonzalez Manuel F.
Published: January 2005

Repetitive tactile sensory stimulation of the right mystacial vibrissae (whiskers) was performed in awake, adult rats. Regions of increased (14C) 2‐deoxyglucose (2DG) uptake were mapped autoradiographically in cerebellum. Predominantly ipsilateral activation of multiple discrete granule cell regions occurred in paramedian lobule, crus 2, crus 1, lobulus simplex, and anterior lobe hemisphere. Bilateral and contralateral activation of cerebellum did occur. Multiple small patches, as well as large granule cell regions, were activated. Mossy fiber afferents from the spinal trigeminal nuclei (particularly interpolates), principal trigeminal sensory nucleus, and superior colliculus could account for metabolic activation of the granular layer. The slight metabolic activation of the molecular layer could have occurred from climbing or parallel fibers.

Comparisons of the paramedian lobule granule cell regions activated during repetitive sensory stimulation of the vibrissae (RSSV) to those activated during vibrissae motor cortex stimulation (VMIS) showed regions only activated by RSSV, regions only activated by VMIS, and regions activated by both RSSV and VMIS. The granule cell regions activated during RSSV and VMIS were usually adjacent to or overlapping each other. Regions only activated during RSSV or only during VMIS could represent technical problems in trying to compare vibrissae motor and sensory pathways in two different groups of animals. Alternatively, cerebellar regions activated only during RSSV could process vibrissae tactile inputs. Regions activated only during VMIS could process vibrissae motor and perhaps proprioceptive sensory input. Regions activated during both RSSV and VMIS might process vibrissae proprioceptive sensory input and/or might represent loci where vibrissae motor, proprioceptive sensory, and tactile sensory convergence occur. The results raise the possibility that vibrissae motor, proprioceptive sensory, and tactile sensory pathways could be processed in separate granule cell patches in p arts of cerebellum and in the same granule cell patches in other parts of cerebellum.
Ultrastructure of mouse vallate taste buds. I. Taste cells and their associated synapses
Authors: Kinnamon John C. , Taylor Barbara J. , Delay Rona J. , Roper Stephen D.
Published: January 2005

The ultrastructural features of murine vallate taste bud cells and their associated synapses have been examined in thin and thick sections with conventional transmission electron microscopy and high‐voltage electron microscopy. Computer‐assisted reconstructions from serial sections were utilized to aid in visualization of taste bud cell‐nerve fiber synapses.

We have classified taste bud cells on the basis of previously established criteria‐namely, size of the nucleus, shape and density of chromatin, density of cytoplasm, and presence or absence of dense‐cored or clear vesicles, other cytoplasmic organelles, and synaptic foci. Both dark cells and light cells are present, as well as cells with intermediate morphological characteristics.

Synapses were observed from taste bud cells onto nerve fiber processes. In virtually all instances, synapses are associated with the nuclear region of the taste cell. These synapses are characterized by the presence of 40–70 nm clear vesicles embedded in a thickened presynaptic membrane separated from the postsynaptic membrane by a 16–30 nm cleft. Synapses are not unique to any particular cell type. Dark, intermediate, and light cells all synapse onto nerve fibers. Two general types of synapses exist: spot (or macular) and fingerlike. In the latter, the postsynaptic region of the neuronal process protrudes into an invagination of the taste cell membrane. Differences in synaptic morphology are not correlated with taste cell type. In some cases a single taste cell was observed to possess both macular and fingerlike synapses adjacent to one another, forming a synaptic complex onto a single neuronal process. On the basis of the presence of synaptic contacts, we conclude that both “dark” and “light” cells are gustatory receptors.
Functional organization in cortical barrels of normal and vibrissae‐damaged mice: A (3H) 2‐deoxyglucose study
Authors: Durham Dianne , Woolsey Thomas A.
Published: January 2005

The large mystacial vibrissae on the faces of rodents have punctate representations in all stations in the central trigeminal pathway, including layer IV of the somatosensory cortex (SmI). The cortical whisker correlates, multicellular units termed barrels, are not present at birth, and damage to the vibrissae during the first postnatal week results in altered adult cytoarchitectonics The anatomical effects of vibrissae damage in the cortex have been well documented; here, we investigated the functional organization of altered SmI barrels with a high‐resolution 2‐deoxyglucose (2‐DG) technique (Durham et al., '81, J. Neurosci. 1:519). The middle row of vibrissae was cauterized in 1‐, 2‐, 3‐, 4‐, or 5‐day‐old mice, and the animals were allowed to survive to sexual maturity. Various combinations of vibrissae were clipped acutely 24 hours prior to injection of 2–4 mCi of (3H)2‐DG. Mice actively explored an empty cage for 60 minutes, stimulating the remaining vibrissae. The mice then were perfused and their brains prepared for paraffin histology and emulsion autoradiography.

In tangential sections through layer IV, patterns of neuropil and cell body labeling were analyzed with respect to barrel cytoarchitecture in normal and vibrissae‐damaged mice. In both control and experimental animals, patterns of neuropil and cell somata label corresponded exactly to barrel boundaries, whether normal or altered by vibrissae damage. Only those barrels for which vibrissae were intact had high levels of label, with anterior barrels more heavily labeled. Many neurons in the septa between these barrels and the adjacent barrels were labeled also. We found slightly higher neuropil label in the cortical zone corresponding to the damaged zone on the face in animals lesioned at any time. These data indicate that physiological somatotopy in vibrissae‐damaged animals matches the anatomical cytoarchitecture.