bluuebunny/crossref_metadata_2025 huggingface dataset:
Synaptic connections between primary trigeminal afferents and acccessory abducens motoneurons in the monitor lizard, Varanus exanthematicus
Authors: Barbas‐Henry Heleen A. , Wouterlood Floris G.
Published: January 2005

We studied the anatomical pathway underlying the nictitating reflex in the monitor lizard Varanus exanthematicus by the anterograde degeneration technique combined with retrograde transport of horseradish peroxidase (HRP) and electron microscopy.

After application of HRP to the abducens nerve, retrogradely labeled neurons were observed in the ipsilateral principal and accessory abducens motor nuclei. The transection, in the same experiments, of the root of the trigeminal nerve resulted in massive degeneration of myelinated fibers in the descending trigeminal tract. In the ipsilateral accessory abducens nucleus, we observed electron‐dense degenerating axon terminals that formed asymmetric synaptic contacts with the primary and secondary dendrites of large neurons retrogradely labeled with HRP. A few of the degenerating terminals could be traced in serial sections to myelinated axons. No terminal degeneration was found in the contralateral accessory abducens nucleus or in the ipsilateral and contralateral principal abducens nuclei. The present results are complementary with the findings of previous light microscopic experimental tracing studies (Barbas‐Henry, H.A., and A.H.M. Lohman, J. Comp. Neurol. 1986, 254:314–329; see also J. Comp. Neurol. 1988, 267:370–386), and strongly suggest the existence in Varanus of a monosynaptic, unilateral reflex pathway in which trigeminal fibers, presumably originating from the cornea, synapse with motoneurons of the bursalis and retractor bulbi muscles, which are located in the accessory abducens nucleus. This monosynaptic pathway may mediate a rapid unilateral eyeball retraction and nictitating membrane extension.
Intracortical connections and their physiological correlates in the primary auditory cortex (AI) of the cat
Authors: Matsubara Joanne A. , Phillips D. P.
Published: January 2005

We studied the functional and anatomical properties of the intrinsic connections in the primary auditory cortex (AI) of the cat by using physiological mapping and retrograde tracing methods. Our results revealed that a focal micro inject ion of tracer labeled as many as five intracortical patches in AI. The patches contained labeled pyramidal and non‐pyramidal cell types, most of which were clustered in the middle layers. A densely distributed anterograde‐like reaction product was present in the superficial layers above the labeled cells. The distribution of the patches was anisotropic, with most patches occurring dorsal, ventral, and anterior to the injection site. We examined the correlation between the characteristic frequency (CF) and binaural response properties of the injected and labeled regions. We found local labeling in regions possessing CFs equivalent to or slightly greater than that of the injected area. This appears to be a specific connection since we were able to predict the general location of many of the patches on the basis of the organization of the isofrequency domains. Patches were more numerous dorsoposterior to the injection site when the isofrequency contours ran obliquely (i.e., dorsoposterior to ventroanterior) across AI. The binaural response properties of the injected and labelled regions, however, were unrelated.
Differences in synaptic inputs to preganglionic neurons in the dorsal and lateral band subdivisions of the cat sacral parasympathetic nucleus
Authors: Leedy Mitzi G. , Bresnahan Jacqueline C. , Mawe Gary M. , Beattie Michael S.
Published: January 2005

In the cat, preganglionic neurons (PGNs) found in the dorsal portion of the sacral parasympathetic nucleus (dorsal band or DB cells) participate in bowel control, while those found along the lateral edge (lateral band or LB cells) influence bladder function. In order to determine whether differences in the synaptic inputs exist between these two populations, HRP was applied to the sacral ventral rootlets of cats, and the S2 cord segment was prepared for sequential light and electron microscopy. When measured with light microscope, the LB somata had greater cross‐sectional areas than did the DB cells. Ultrastructurally, the LB cells had a significantly greater percentage of their membrane apposed by synaptic active sites than did the DB cells. Also, the proximal dendrities of the labelled neurons received greater synaptic input than did the somata. No difference was found in the proportion of terminals containing dense cored vesicles (DCVs) when comparing LB and DB somata; however, the LB proximal dendrites had a higher proportion of their surface contacted by DCV‐containing terminals than did the DB dendrites. These ultrastructural results offer evidence that these two populations of preganglionic neurons differ with respect to their synaptic input as well as their peripheral targets.
Distribution of D1 and D2 dopamine receptors in the basal ganglia of the cat determined by quantitative autoradiography
Authors: Beckstead R. M. , Wooten G. F. , Trugman J. M.
Published: January 2005

The patterns of dopamine D1 and D2 receptors were examined in the corpus striatum and related structures in the cat brain by quantitative autoradiography after in vitro radioligand binding with [3H]SCH23390 (D1 antagonist) and [3H]spiperone (D2 antagonist). Highly specific binding for both radioligands occurs in striatal structures known to receive dopaminergic input: the caudate nucleus, putamen, nucleus accumbens, and olfactory tubercle. However, the density of binding varies from one structure to another, and the density distribution within striatal nuclei is heterogeneous. In all but one portion of the striatum, the concentration of bound D1 radioligand ranges from 46 to 230% more than that of the D2 radioligand. The exception to this difference occurs at caudal putamenal levels where the two radioligands bind in equal concentrations. (≈︁ 220 fmol/mg tissue wet‐weight). The highest density of both D1 and D2 radioligand binding occurs in irregular zones in the head and body of the caudate nucleus. Such high‐density zones of D2 radioligand binding appear mainly in the dorsolateral part of the caudate's head. For the D1 radioligand, the high‐density zones are more widespread throughout the caudate nucleus, nucleus accumbens, and putamen. The D2 radioligand binding (but not the D1) also exhibits low‐density zones at more caudal levels of the caudate nucleus, and these are often in register with the high‐density zones of D1 radioligand binding. In the putamen, inverted concentration gradients, exist for the two radioligands: the [3H]SCH23390 gradient runs from higher levels rostrally to lower levels caudally. The lowest levels of bound [3H]spiperone in the striatum occur in the nucleus accumbens‐olfactory tubercle area, whereas the lowest binding of [3H]SCH23390 occurs in the caudal putamen.

Pallidal and nigral structures show marked disparities in binding of the two different radioligands. The D2 radioligand binding in the globus pallidus (80 ± 8 fmol/mg tissue wet‐weight) is about twice that in the entopeduncular nucleus and pars reticulata of the substantia nigra, the latter two having equal levels (35 ± 3 fmol/mg). No specific binding of the D2 radioligand occurs in the ventral pallidum. In contrast, D1 radioligand binding is highest in the entopeduncular nucleus (217 ± 6 fmol/mg) and in the pars reticulata of the substantia nigra (198 ± 2 fmol/mg) and moderate in the ventral pallidum (135 ± 15 fmol/mg). In the globus pallidus, no detectable D1 radioligand binding occurs. The binding density of [3H]SCH23390 is comparable in both subdivisions of the substantia nigra, but [3H]spiperone binding is four times greater in the pars compacta (154 ± 12 fmol/mg) than in the pars reticulata. The heterogeneity of dopamine receptors is discussed with respect to other evidence for compartmentation in the striatum and the neurochemical organization of the striatopallidal projection system.
Corticothalamic connections of paralimbic regions in the rhesus monkey
Authors: Yeterian Edward H. , Pandya Deepak N.
Published: January 2005

This study addressed the issue of whether paralimbic regions of the cerebral cortex share common thalamic projections. The corticothalamic connections of the paralimbic regions of the orbital frontal, medial prefrontal, cingulate, parahippocampal, and temporal polar cortices were studied with the autoradiographic method in the rhesus monkey. The results revealed that the orbital frontal, medial prefrontal, and temporal polar proisocortices have substantial projections to both the dorsomedial and medial pulvinar nuclei, whereas the anterior cingulate proisocortex (area 24) projects exclusively to the dorsomedial nucleus. These proisocortical areas also have thalamic connections with the intralaminar and midline nuclei. The cortical areas between the proisocortical regions on the one hand and the isocortical areas on the other, that is, the posterior cingulate region (area 23) and the posterior parahippocampal gyrus (areas TF and TH), project predominantly to the dorsal portion of the medial pulvinar nucleus, the anterior nuclear group (AV, AM), and the lateral dorsal (LD) nucleus. Additionally, the posterior cingulate and medial parahippocampal gyri (area TH) have projections to the lateral posterior (LP) nucleus.

Thus, it appears that the proisocortical areas, which are characterized by a predominance of infragranular layers and an absence of layer IV, have common thalamic relationships. Likewise, the intermediate paralimbic areas between the proisocortex and isocortical regions, which also have a predominance of infragranular layers but in addition have evidence of a fourth layer, project to the medial pulvinar and to the so‐called limbic nuclei, AV, AM, LD, as well as a modality‐specific nucleus, LP.
Morphology of the caudal spinal cord in Rana (ranidae) and Xenopus (pipidae) tadpoles
Authors: Nishikawa Kiisa , Wassersug Richard
Published: January 2005

Using a variety of neuroanatomical and histological techniques, we compare the spinal cord and peripheral nerve distribution in the tails of larvae from Xenopus laevis and three species of Rana.

The relatively large, postsacral spinal, cord of Xenopus contains abundant motoneurons and their axons. Spinal nerves exit from the spinal cord in a regular array, one nerve per myotome, from the cervical region to near the end of the tail. Somata of motoneurons innervating caudal myotomes are found along the entire length of the tail. In contrast, the caudal cord of Rana is reduced to a filum terminate consisting of little more than an ependymal tube; spinal nerves to all caudal myotomes leave the cord in the sacral region and reach their motor targets via a cauda equina and caudal plexus. Motoneuron cell bodies innervating caudal myotomes are found only in the sacral region.

The Rana larval pattern is similar to that of adult frogs and mammals, whereas the Xenopus larval pattern is more like that of salamanders and reptiles. These gross neuroanatomical differences are not due to differences in the size or developmental stage of the tadpoles, but instead are associated with differences in the swimming behavior of the larvae.

The presence of motoneurons in the caudal spinal cord of Xenopus may provide local intermyotomal control within the tail; the elongated topography of the cord appears to permit finer, rostral‐to‐caudal regulation of neuromuscular activity. The Rana spinal cord, on the other hand‐with motoneurons clustered anteriorly‐may produce concurrent firing of adjacent ipsilateral myotomes, but at the expense of fine intermyotomal regulation. The fact that nerves in the tail of Xenopus enter and exit from the spinal cord locally, as opposed to far anteriorly as in Rana, means that for tadpoles of the same size, reflex arc lengths are many times shorter in Xenopus.
Sexual differences in the development of accessory olfactory bulbs in the rat
Authors: Roos J. , Roos M. , Schaeffer C. , Aron C.
Published: January 2005

The aim of this investigation was (1) to compare the development of AOB in male and female rats before birth, early after birth, and at later stages of sexual immaturity and maturity (2) to examine the effects of early and delayed castration after birth on AOB development in the male rat. A significant increase of the surface area of AOB was observed in both sexes from birth until postnatal day 7, but AOB was found to be larger in males than in females. From the end of the first postnatal week AOB stopped growing until day 40 in both males and females. After this time AOB resumed its development until day 60 in males, while no changes occurred in females over the same period. Castration of males at birth or six hours later impaired development of AOB. Castration of males on postnatal days 20 or 30 also impaired AOB development until day 60.

The results strongly suggest that the development of AOB in the male rat is dependent on the two well known “perinatal” and “adult” phases of the endocrine activity of the testes.
Ultrastructural visualization of primate cone photoreceptor matrix sheaths
Authors: Blanks Janet C. , Hageman Gregory S. , Johnson Lincoln V. , Spee Christine
Published: January 2005

Glycoconjugates, including glycolipids, glycoproteins, and proteoglycans, are present in the plasma membrane of photoreceptor cells and in the interphotoreceptor matrix surrounding photoreceptor cell ellipsoids and outer segments. Although the precise function of these molecules is unknown, they may be important in mediating photoreceptor–pigment epithelial cell interactions, outer segment membrane assembly, and/or disc shedding. Lectins, affinity ligands for defined carbohydrate sequences, have proven particularly useful in studying the glycoconjugate composition of the interphotoreceptor matrix. The peanut lectin selectively binds to domains of the interphotoreceptor matrix surrounding cone (“cone matrix sheaths”), but not rod inner and outer segments. This is evidence for the existence of chemical and structural heterogeneity within the interphotoreceptor matrix.

The studies described herein utilized ultrastructural pre‐embedding histochemical labeling to assess whether, in addition to the surrounding interphotoreceptor matrix, peanut lectin binding is associated directly with the plasma membrane of cone inner and outer segments. This study confirms that ferritin‐conjugated peanut agglutinin binds to cone matrix sheaths, and, in addition, provides ultrastructural evidence for the presence of binding to the plasma membrane surrounding cone inner and outer segments. The data suggest that cone membrane–associated peanut agglutinin–binding molecules may differ from those located within cone matrix sheaths.
Origin of ascending projections to an isofrequency region of the mustache bat's inferior colliculus
Authors: Ross Linda S. , Pollak George D. , Zook John M.
Published: January 2005

The inferior colliculus of the mustache bat is similar in most respects to the inferior colliculus of more commonly studied mammals, but one isofrequency contour, the dorsoposterior division, is greatly overrepresented. The present study utilizes this specialization of the auditory system in the mustache bat to determine the total set of ascending projections to a single isofrequency contour of the inferior colliculus. Within the dorsoposterior division, neurons are all very narrowly tuned to 60 kHz, the major component of this bat's echolocation call. The afferent projections to this isofrequency contour were identified by making deposits of horseradish peroxidase (HRP) within the dorsoposterior division after physiologically defining its borders. Two other frequency representations are present in the central nucleus of the inferior colliculus of the mustache bat, the anterolateral division in which there is an orderly progression of frequencies from 59 down to 20 kHz, and the medial division in which frequencies from 63–120 kHz are represented. In additional experiments, the afferent projections to the medial and anterolateral divisions were examined, providing an anatomical description of the tonotopicity of the lower auditory nuclei.

Deposits of HRP in the DPD labeled cells in each of the lower brainstem auditory nuclei that have previously been shown to project to the entire central nucleus of the inferior colliculus. The ascending projections to the dorsoposterior division include contralateral projections from the cochlear nucleus and inferior colliculus, ipsilateral projections from the medial superior olive, ventral and intermediate nuclei of the lateral lemniscus, and bilateral projections from the lateral superior olive and dorsal nucleus of the lateral lemniscus. In most of the nuclei, labeled cells were confined to specific portions of the nuclei, often forming “slabs” of labeled cells across the rostrocaudal extent of most nuclei. These slabs presumably represent the 60 kHz representation in each of the lower nuclei. When deposits of HRP were made into other frequency band representations of the inferior colliculus, in either the medial or anterolateral division, labeled cells again formed slabs in each lower nucleus. However, the location of the slab varied as a function of the best frequency of neurons at the deposit site, and labeled cells were not present within the 60 kHz representation. These results show the general tonotopy of the mustache bat's brainstem auditory nuclei, and with respect to the dorsoposterior division, clearly reveal the total set of projections to a single isofrequency region. In addition, results are presented that suggest that some nuclei project to restricted areas of the dorsoposterior division.
Topographical relationship between the entorhinal cortex and the septotemporal axis of the dentate gyrus in rats: II. Cells projecting from lateral entorhinal subdivision
Authors: Ruth Russell E. , Collier Timothy J. , Routtenberg Aryeh
Published: January 2005

Projections from the rat lateral entorhinal cortex (area 28‐l) to the dentate gyrus were traced and then interpreted according to a parcellation scheme that recognized four cytoarchitectonic subdivisions of area 28‐1: areas dorsolateral (dl), ventrolateral (vl), ventromedial (vm), and TR. Following lesions of area 28‐l, anterograde degeneration was traced with the Fink‐Heimer method. In parallel experiments iontophoretic injections of horseradish peroxidase (HRP) were made in the lateral perforant path terminal zone of the dentate molecular layer. Retrograde neuronal labeling patterns within area 28‐l were charted following dorsal, midseptotemporal (mid ST), and ventral dentate injections. In two additional cases HRP was deposited in the ventral subiculum.

Lesions of area dl (which lies entirely on the posterolateral cortex) produced terminal degeneration that was confined to the dorsal one‐half of the dentate gyrus. Lesions involving primarily areas vl and vm (which lie on the posteroinferior cortex) caused a complementary pattern of degeneration; silver grains predominated in the ventral dentate gyrus.

Injections of HRP into the outer dentate molecular layer labeled layer II neurons within area 28‐l. Deposits of HRP in the dorsal one‐third of the dentate gyrus labeled a rostrocaudal strip of neurons within the dorsal one‐third of area dl; no other subdivisions of area 28vl contained labeling. After mid‐ST deposits of HRP, a rostrocaudally oriented strip of labeled cells appeared in the ventral one‐third of area dl. Mid‐ST injections also labeled neurons in the caudolateral quadrant of area vl. Injection of HRP into the ventral dentate gyrus labeled neurons in the caudomedial quadrant of area vl as well as a few neurons in caudal area vm. No labeled cells were ever found in area dl following ventral dentate HRP deposits. Neurons within area TR were never retrogradely labeled from injections of HRP into the dentate perforant path zone. However, ventral subicular injections of HRP labeled a few cells in the posterior part of area TR, as well as hundreds of neurons throughout the rostrocaudal extent of area vl.

The results indicate a highly organized innervation of the dentate gyrus by several subdivisions of area 28‐l. In area dl, rostrocaudal strips of layer II neurons innervate distinct segments of the dorsal ST axis. The posterior half of areas vl and vm innervates the ventral half of the ST axis; a lateromedial gradient there corresponds to increasingly ventral terminations along the dentate ST axis. Finally, in contrast to the other lateral entorhinal subdivisions area TR does not appear to innervate the distal dendrites of dentate granule cells. The implications of this organization for the study of functional diversity along the ST axis are considered.
Afferent connections of the sexually dimorphic area of the hypothalamus of male and female gerbils
Authors: De Vries Geert J. , Gonzales Cathleen L. , Yahr Pauline
Published: January 2005

We studied neural inputs to the sexually dimorphic area (SDA) of the gerbil hypothalamus by injecting wheat‐germ agglutinin‐horseradish peroxidase into its medial or lateral components in males and females. To confirm the topography of SDA afferents, we injected Phaseolus vulgaris‐leucoagglutinin into areas where retrograde labeling from the medial and lateral SDA differed. Both methods indicated that the medial SDA received stronger inputs from the medial part of the bed nucleus of the stria terminalis, the ventral part of the lateral septal nucleus, the medial amygdaloid nucleus, and the amygdalohippocampal area, than the lateral SDA does. In contrast, the rostrodorsal part of the lateral septum, the lateral part of the bed nucleus of the stria terminalis, the anterior and posterior hypothalamic areas, and the dorsomedial hypothalamic nucleus project more heavily to the lateral than to the medial SDA. In addition, retrograde labeling suggested that the ventral part of the premammillary nucleus projects more strongly to the medial than to the lateral SDA, whereas the infralimbic area of the cortex and the lateral preoptic area project more strongly to the lateral than to the medial SDA. The densities of cells in the bed nucleus of the stria terminalis and medial amygdaloid nucleus that could be retrogradely labeled from the medial SDA were greater in males than in females. This was not true of labeling in the arcuate nucleus or in the ventral part of the lateral septal nucleus. Since the medial SDA receives strong inputs from areas with many steroid‐accumulating cells, it could respond to steroids directly and via these afferents. In contrast, hormonal effects on the lateral SDA are more likely to occur locally.
Distribution of dopamine immunoreactivity in the forebrain and midbrain of the snake Python regius: A study with antibodies against dopamine
Authors: Smeets Wilhelmus J. A. J.
Published: January 2005

The distribution of dopamine (DA) immunoreactivity in the forebrain and midbrain of the ball python, Python regius, was studied by using recently developed antibodies against DA. In order to determine general and species‐specific features of the DA system in reptiles, we have selected the ball python as a representative of a reptilian radiation that hitherto has not been the subject of (immuno)histochemical studies.

Dopamine‐containing cell bodies were found around the glomeruli and in the external plexiform layer of both the main and accessory olfactory bulb, but not in the telencephalon proper. In the diencephalon, DA cells were observed in several parts of the periventricular hypothalamic nucleus, in the periventricular organ, the ependymal wall of the infundibular recess, the lateral hypothalamic area, the magnocellular ventrolateral thalamic nucleus, and the pretectal posterodorsal nucleus. In the midbrain, DA cells were found in the ventral tegmental area, the substantia nigra, and the presumed reptilian homologue of the mammalian A8 cell group.

Dopaminergic fibers and varicosities were observed throughout the whole brain, particularly in the telencephalon and diencephalon. The nucleus accumbens, striatum, olfactory tubercle, and nucleus of the accessory olfactory tract appear to have the most dense innervation, but the lateral septal nucleus, the dorsal ventricular ridge, and the nucleus sphericus also show numerous DA‐containing fibers and varicosities. Except for the lateral cortex, cortical areas are not densely innervated by DA fibers.

The DA system of the snake Python regius shares many features with that of lizards and turtles as determined with the same antibodies. The taxonomically close relationship between lizards and snakes, which together constitute the Squamata, is reflected in a similar distribution of DA fibers and varicosities to the dorsal ventricular ridge and the lateral cortex, and in the limited number of CSF‐contacting DA neurons in the hypothalamus.
Cerebral arterial innervation by nerve fibers containing calcitonin gene‐related peptide (CGRP): I. Distribution and origin of CGRP perivascular innervation in rat
Authors: Tsai Shin‐Han. , Tew John M. , McLean John H. , Shipley Michael T.
Published: January 2005

The origin, density and distribution of calcitonin gene‐related peptide (CGRP) immunoreactivity in cerebral perivascular nerves and the trigeminal ganglion of rats were examined in this study. CGRP immunoreactive axons were abundant on the walls of the rostral circulation of the major cerebral arteries in the circle of Willis. The fibers form a grid‐ or meshwork of longitudinal and circumferential axons studded with numerous varicose swellings. The density of CGRP fibers was particularly high at the bifurcation of major arteries. A few CGRP fibers cross the midline to innervate arteries on the contralateral side of the arterial tree. The arteries of the caudal circulation were sparsely innervated by CGRP fibers.

In the trigeminal ganglion, about 30% of the ganglion cells had CGRP immunoreactivity. The cell size of most (75%) of CGRP neurons was less than 30 μm in diameter. There was no significant difference in staining density between small and large CGRP neurons. Unilateral transection of the maxillary and mandibular divisions of the trieminal nerve caused a substantial decrease of CGRP immunoreactivity in the ipsilateral dorsal two‐thirds of te trigeminal nucleus and cervical spinal cord but did not noticeably change the diameter of the vascular lumen or the densities of CGRP fibers in the walls of te cerebral arteries. In contrast, unilateral on the ipsilateral cerebral arteries and eliminated CGRP immunoreactivity throughout the trigeminal nucleus in the brainstem and rostral cervical cord. In addition, tese lesions caused a significant reduction in the diameter of the denervated arteries.

The present study demonstrates that CGRP, a putative neurotransmitter/neuromodulator, is especially abundant in the rostral cerebral circulation and is derived from the ipsilateral ophthalmic division of the trigeminal nerve. In addition, the loss of CGRP perivascular nerves is associated with a reduction of the arterial lumen. This suggests that CGRP is a strong candidate as a nerve‐derived trophic factor at trigeminal terminals and provides additional evidence that CGRP is a component in te trigeminovascular system influenceing vascular diameter.
Early development of serotonin‐containing neurons and pathways as seen in wholemount preparations of the fetal rat brain
Authors: Aitken Adrian R. , Törk Istvan
Published: January 2005

The early development of serotonin‐containing neurons was studied in wholemounts of the fetal rat brain (E12–E18). The wholemounts were treated immunocytochemically according to an immunoperoxidase technique to reveal a panorama of developing serotoninergic neurons. Serotoninergic neurons were localized to two discrete groups or clusters within the brainstem. Serotonin‐containing neurons were identified first at E12 forming a rostral cluster of cells just caudal to the mesencephalic flexure. The more caudal cluster of cells first appeared at E14 in the medulla. During the period from E12 to E18, the immunoreactive cells increased in number and acquired a more complex dendritic tree while migrating to their permanent position. At E16, cells of the rostral group exhibited remarkably uniform mediolateral orientation.

The rostral group of immunoreactive neurons gave rise to almost all ascending fibers, whereas the caudal group gave rise to the majority of descending fibers. Growing serotoninergic fibers were tipped by prominent growth cones, which were strongly immunoreactive. The fibers demonstrated prominent orientational selectivity with an almost total separation into ascending and descending bundles. Some of the ascending immunoreactive fibers displayed acute changes in their direction of growth, suggesting that the orientation of serotininergic fibers is mediated by directional cues that are specific to particular populations of serotoninergic fibers. Serotoninergic axons within the medial forebrain bundle were demonstrated particularly well and their ascent and rate of growth toward the forebrain could be easily followed. Immunoreactive fibers entered the telencephalon at E17 two portals, one along the lateral border of the hypothalamus and one rostrally, adjacent to the olfactory tubercle. In wholemounts at E18, fibers arising from this latter location could be followed as two distinct bands within the pallium; a basal band located ventrolaterally, adjacent to the lateral olfactory tract, and a dorsal band located at the medial edge of the telencephalon. Both fascicles were directed toward the occipital pole and contained unbranched fibers. At E18, serotoninergic axons arising from these two loosely organized fascicles covered most of the frontal telencephalon.

The results of the present study indicate that wholemounts of embryonic brain can provide novel spaciotemporal data on the development of neuro‐transmitter systems and may in the future prove to be useful experimental preparations in developmental neurobiology.
Neonatal infraorbital nerve transection in rat results in peripheral trigeminal sprouting
Authors: Chiaia Nicolas L. , Allen Zebetta , Carlson Eric , MacDonald Gordon , Rhoades Robert W.
Published: January 2005

Retrograde tracing techniques were employed to determine whether transection of the infraorbital (IO) nerve in either newborn or adult rats resulted in peripheral sprouting by undamaged trigeminal (V) axons. The IO nerve was sectioned just behind the vibrissa pad, either on the day of birth or when animals reached at least 60 days of age. After an additional 60 days, the same nerve was retransected in the orbit; horseradish peroxidase (HRP) or diamidino yellow (DY) was injected into the central portion of the vibrissa pad; and animals were killed 2–3 days later. In the neonatally nerve‐damaged rats, this procedure invariably labelled primary afferent neurons in both the ipsilateral and contralateral V ganglia. On the ipsilateral side, these cells were located in the caudal portion of the ophthalmicmaxillary region and, less often, in the mandibular division. Their average diameter was 22.6 μm (s.d.=5.6). On the contralateral side, most labelled ganglion cells were visible in the anteromedial part of the ophthalmicmaxillary region but a few could also be seen in the mandibular division. Their average diameter was 21.1 μm (s.d.=5.5). No labelled ganglion cells were observed in adult rats subjected to the same series of manipulations.

In a separate series of neonatally nerve‐damaged animals, the above‐described procedures were combined with neonatal injection of capsaicin in an effort to determine whether the observed sprouting was dependent upon the presence of large numbers of unmyelinated axons. The addition of this treatment reduced the number of labelled cells in both the ipsilateral and contralateral ganglia, but it did not alter either their distribution or average soma diameter.

In a final experiment, sequential double‐labelling techniques were used to determine whether the V axons that projected to the vibrissa pad via non‐IO nerve branches were the result of sprouting by undamaged ganglion cells or arose from neurons that had originally projected into the IO nerve, were axotomized by our lesions, and regenerated to the vibrissa pad via another V branch. Here, the long‐lived retrograde tracer true blue (TB) was injected into the vibrissa pad 6–8 hours before the neonatal nerve cut and DY was deposited into the pad after transection of the regenerate IO nerve in adulthood. Double‐labelled cells in this experiment would have projected to the vibrissa pad via the IO nerve at birth and regenerated to it via another V branch in adulthood. Nearly 55% of the DY‐labelled cells in this experiment also contained TB. This result indicated that about one‐half of the innervation of the vibrissa pad by non‐IO V branches was the result of axonal sprouting by undamaged ganglion cells.
Quantitative study of granule and Purkinje cells in the cerebellar cortex of the rat
Authors: Harvey R. J. , Napper R. M. A.
Published: January 2005

The numerical densities of granule and Purkinje cells in the cerebellar cortex of the rat were determined by stereological methods. The density of Purkinje cells in our fixed material was 1,018 ± 39 per mm2 (mean ± s.e.m.) of Purkinje cell layer and that of granule cells 1.92 ± 0.03 × 106 per μl of granular layer. The total area of Purkinje cell layer was 332 mm2 and the volume of granular layer was 48 μl. The rat cerebellum therefore contains 3.38 × 105 Purkinje cells and 9.2 × 107 granule cells, from which there are 274 granule cells for each Purkinje cell. The density of granule cells and the density of parallel fibers in the molecular layer observed in a companion study indicate that the average length of a parallel fiber is around 5 mm.
Projections of nucleus angularis and nucleus laminaris to the lateral lemniscal nuclear complex of the barn owl
Authors: Takahashi Terry T. , Konishi Masakazu
Published: January 2005

Interaural phase and intensity are cues by which the barn owl determines, respectively, the azimuth and elevation of a sound source. Physiological studies indicate that phase and intensity are processed independently in the auditory brainstem of the barn owl. The phases of spectral components of a sound are encoded in nucleus magnocellularis (NM), one of the two cochlear nuclei. NM projects solely and bilaterally to nucleus laminaris (NL), wherein interaural phase difference is computed. The other cochlear nucleus, nucleus angularis (NA), encodes the amplitudes of spectral components of sounds. We report here the projections of NA and NL to the lateral lemniscal nuclei of the barn owl.

The lateral lemniscal complex comprises nucleus olivaris superior (SO); nucleus lemnisci lateralis, pars ventralis (LLv); and nucleus ventralis lemnisci lateralis (VLV). At caudal levels, VLV may be divided into a posterior (VLVp) and an anterior (VLVa) subdivision on cytoarchitectonic grounds. At rostral levels, the cytoarchitectural differences diminish and the boundaries between the two subdivisions become obscured. Likewise, our data from anterograde tracing studies suggest that at caudal levels the terminal fields of NA and NL remain confined to VLVp and VLVa, respectively. They merge, however, at rostral levels. The data also suggest that NL projects to the medial portion of the ipsilateral SO and that NA projects bilaterally to all parts of SO and LLv. Studies with the retrograde transport of horseradish peroxidase confirm these projections.
Spinocerebellar projections from the lowest lumbar and sacral‐caudal segments in the cat, as studied by anterograde transport of wheat germ agglutinin‐horseradish peroxidase
Authors: Matsushita Matsuo
Published: January 2005

The projection fields of spinocerebellar tracts arising from the lowest lumbar and sacral‐caudal segments were studied by the anterograde transport of wheat germ agglutinin conjugated to horseradish peroxidase (WGA‐HRP) in the cat.

Injections of WGA‐HRP into these segments labeled mossy fiber terminals mainly in sublobules Ia‐Vf, lobule VI, and sublobules VIIb‐VIIIb. In the sagittal plane the labeled terminals were distributed in the apical part of the lobules. MOre than 90% of the total number were in the anterior lobe, of which 50–80% were in sublobules IIa and IIb. The labeled terminals were concentrated between 1.0 and 2.0 mm lateral to the midline. The results of injections following hemisections revealed that the projections are bilateral and that their quantity does not differ between the two sides. The projection fields in the horizontal plane were reconstructed from a series of cross sections through lobules I–III. The labeled terminals were distributed in two areas localized to the apical part of the lobules: area 1 located between 0.75 and 1.5 mm lateral to the midline in zone B of Voogd (the lateral part of the vermis) and area 2 located 2.0 mm lateral to the midline in zones C1–C3 (the intermediate region of the hemisphere).

The present anterograde and previous retrograde HRP studies show that the spinocerebellar tract neurons in the medial part of lamina VII caudal to the L7 segment and in laminae V and VIII of sacral‐caudal segments project mainly to lobules I–V of the anterior lobe and to lobule VI, sublobule VIIb, and lobule VIII of the posterior lobe. The projections were most abundant in sublobules IIa and IIb.
Ascending projections from the pedunculopontine tegmental nucleus and the adjacent mesopontine tegmentum in the rat
Authors: Hallanger Ann E. , Wainer Bruce H.
Published: January 2005

Ascending projections from the pedunculopontine tegmental nucleus (PPT) and the surrounding mesopontine tegmentum to the forebrain in the rat are here examined by using both retrograde and anterograde tracing techniques combined with choline acetyltransferase (ChAT) immunohistochemistry. The anterogradely transported lectin Phaseolus vulgaris‐leukoagglutinin (PHA‐L) was iontophoretically injected into the PPT in 12 rats. Anterogradely labelled fibers and varicosities were observed in the thalamic nuclei, confirming the findings of our previous retrograde studies (Hallanger et al: J. Comp. Neurol. 262:105–124, ′87). In addition, PHA‐L‐labelled fibers and varicosities suggestive of terminal fields were observed in the anterior, tuberal, and posterior lateral hypothalamic regions, the ventral pallidum in the region of the nucleus basalis of Meynert, the dorsal and intermediate lateral septal nuclei, and in the central and medial nuclei of the amygdala.

To determine whether these were cholinergic projections, the retrograde tracer WGA‐HRP was injected into terminal fields in the hypothalamus, septum, ventral pallidum, and amygdala. Numerous ChAT‐immunoreactive neurons in the PPT and laterodorsal tegmental nucleus (LDT) were retrogradely labelled from the lateral hypothalamus. These cholinergic neurons constituted over 20% of those retrogradely labelled in the dorsolateral mesopontine tegmentum; the balance consisted of noncholinergic neurons of the central tegmental field, retrorubral field, and cuneiform nucleus. Following placement of WGA‐HRP into dorsal and intermediate lateral septal regions, the vast majority (> 90%) of retrogradely labelled neurons were cholinergic neurons of the PPT and LDT, with few noncholinergic retrogradely labelled neurons in the adjacent tegmentum. In contrast, fewer cholinergic neurons were retrogradely labelled following placement of tracer into the nucleus basalis of Meynert or into the central, medial, and basolateral nuclei of the amygdala, while numerous noncholinergic neurons of the central tegmental field rostral to the PPT and of the retrorubral field adjacent to the PPT were retrogradely labelled in these cases. These anterograde and retrograde studies demonstrate that cholinergic PPT and LDT neurons provide a substantial proportion of mesopontine tegmental afferents to the hypothalamus and lateral septum, while projections to the nucleus basalis and the amygdala are minimal.
Immunohistochemical localization of substance P, somatostatin, enkephalin, and serotonin in the spinal cord of the northern leopard frog, Rana pipiens
Authors: Adli Durriyyah S. H. , Rosenthal Bennett M. , Yuen Geoffrey L. , Ho Raymond H. , Cruce William L. R.
Published: January 2005

Using the indirect antibody peroxidase‐antiperoxidase method of Sternberger, we localized substance P (SP), somatostatin (SOM), enkephalin (ENK), and serotonin (5HT, 5‐hydroxytryptamine) in the spinal cord of Rana pipiens. This is the first study to demonstrate all four substances in adjacent sections of frog spinal cord. The distribution patterns of ENK, SP, SOM, and 5HT in our study differ from that described for laminae I and II in amniotes. A high density of ENK, SP, and SOM fibers is present in a band ventral to the dorsal terminal field of cutaneous primary afferent fibers and slightly overlapping the ventral terminal field of muscle primary afferent fibers. However, a high density of 5HT fibers is present in the dorsal terminal field.
Acute and chronic effects of the neurolytic agent ricin on dorsal root ganglia, spinal cord, and nerves
Authors: Pubols Lillian M. , Foglesong Mark E.
Published: January 2005

The short– and long–term effects of ricin injections into nerves have been evaluated with light microscopy in the dorsal root ganglia, spinal cord, and peripheral nerves in rats and cats. Dorsal root ganglion cells initially exhibited chromatolysis, followed by gliosis and cell death. These changes were associated with Fink‐Heimer degeneration in the somatotopically appropriate region of the dorsalhorn. There were no signs of chromatolysis in dorsal horn neurons in ricin‐injected animals, but chromatolytic motoneurons were observed. Ricin produced acute necrosis of injected nerves and dissolution of axoplasm. At long survival times (4 weeks) some apparently regenerating axons were seen in the injection sites of rats. Cell counts indicated that a substantial percentage of dorsal root ganglion neurons associated with the injected nerves were killed, but the presence of regenerating axons suggested that some cells survived the ricin treatment. Although the lesion may not always be complete, even with maximum sublethal doses, this method appears to be useful for specifically destroying afferent fibers associated with a particular nerve without transynaptic destruction of dorsal horn neurons.
Cholinergic vs. noncholinergic efferents from the mesopontine tegmentum to the extrapyramidal motor system nuclei
Authors: Lee Henry J. , Rye David B. , Hallanger Ann E. , Levey Allan I. , Wainer Bruce H.
Published: January 2005

Previous studies have suggested that the pedunculopontine tegmental nucleus (PPTn) is reciprocally connected with extrapyramidal motor system nuclei (EPMS) whereas other studies have implicated the PPTn in behavioral state control phenomena such as sleep‐wakefulness cycles. Many of these studies define the nonprimate PPTn as an area of mesopontine tegmentum which is labeled from injections of anterograde tracers into the basal ganglia. Recently, we have defined the rat PPTn as a large‐celled, cholinergic nucleus. The rat PPTn is cytologically distinct from a group of smaller, noncholinergic neurons that are medially adjacent to the PPTn. This noncholinergic group is further distinguished from the PPTn by its afferent input from the globus pallidus, entopeduncular nucleus, and substantia nigra. We refer to the latter area as the midbrain extrapyramidal area (MEA).

Using combined choline acetyltransferase immunohistochemistry of the PPTn and WGA‐HRP retrograde tracing from the EPMS, we investigated the efferent connections of the MEA and PPTn to the EPMS in the rat. The noncholinergic MEA, rather than the PPTn, is the major source of tegmental innervation to the globus pallidus, caudate‐putamen, subthalamic nucleus, entopeduncular nucleus, substantia nigra, and motor cortex. In contrast, the cholinergic PPTn is the major source of tegmental innervation to the ventrolateral thalamic nucleus. This finding is in contradistinction to thalamic projections from the surrounding reticular formation, which are identified only after WGA‐HRP injections into “nonspecific” thalamic nuclei. This body of evidence suggests that the noncholinergic MEA represents an additional component of the EPMS and may correspond to the “mesencephalic locomotor region.” The cholinergic PPTn may play a role in more global thalamic functions such as the “reticular activating system” rather than a primary role in motor function.
Feline islands of calleja complex: II. Cholinergic and cholinesterasic features
Authors: Talbot Konrad , Woolf Nancy J. , Butcher Larry L.
Published: January 2005

Histochemical analyses demonstrated that the islands of Calleja complex (ICC) in the cat is exceptionally rich in choline acetyltransferase (ChAT) and acetylcholinesterase (AChE). Both enzymes are found in neuropil throughout the complex, as well as in a subset of the satellite neurons accompanying Callejal islands. Lateromedial changes in these cholinergic and cholinesterasic tissue elements were consistent with our previous finding that the feline ICC is cytoarchitecturally divided into five successively more medial types of island‐satellite cell ensembles or units. In particular, satellite neurons reactive for ChAT and AChE diminished progressively in size and increased steadily in number from the most lateral to the most medial units. A concomitant increase in neuropil levels of both enzymes suggested that the strong cholinergic innervation of the feline ICC is at least partially derived from satellite cells. This possibility gained further credibility from the additional observation that very fine processes from some ChAT and AChE satellite neurons projected into the terminal‐like cholinergic field permeating the granular Callejal islands. The granule cells themselves lacked ChAT and (apart from potentially artifactual cases) AChE, as did adjoining groups of dwarf cells and small pyramidal like neurons.

The cholinergic and cholinesterasic satellite neurons were preferentially located above tubercular Callejal islands and in otherwise cell‐poor spaces within the isla magna. Such neurons appeared to be isodendritic: they commonly had ovoidal somata with one or two processes lacking enzyme‐reactive spines. Depending on the type of ICC unit involved, their mean soma length ranged from 15 to 24 μm, all but the largest of which was distinctly smaller than that of ChAT and AChE cells in striatal or basal nuclear structures. Not all the cholinesterase neurons in the feline ICC are cholinergic, judging from the finding that there are a significantly greater number of satellite neurons containing AChE than ChAT.

Three cholinergic features of the feline ICC are especially noteworthy. First, each of the island‐satellite cell ensembles in the complex is unified by AChE neuropil often denser than that of adjacent striatal areas. Second, cholinergic neuropil is exceptionally dense in the isla magna and in a subpial band under medial Callejal islands. Third, ChAT neurons in the isla magna are among the smallest cholinergic cells found in the brain.