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At least 955 records · Page 53Linked to original sources
PubMed2002

The minimum number of neurons in the central olfactory pathway in relation to its function: a retrograde fiber tracing study.

The present study was aimed at determining the functionally essential size of the neuronal population in the central olfactory nervous system. Using conditioned rats who had learnt to avoid repellent (cycloheximide) solution by olfaction, varying degrees of injuries were made to the lateral olfactory tract, a major central olfactory pathway connecting the olfactory bulb to the olfactory cortex. After examining their olfactory ability to discriminate cycloheximide solution from water, intact bulbar projection neurons (mitral cells) with fiber connections to the olfactory cortex were quantified using a retrograde fiber tracing technique. The numbers of retrogradely labeled mitral cells from the rats with normal olfaction ranged between 20 and 92% of the control value, while those numbers from the anosmic rats ranged between 0 and 22%. We conclude that the functionally essential neuronal population is approximately one-fifth of the total in the central olfactory pathway, a presumed threshold value in terms of the ability to avoid cycloheximide solution by olfactory discrimination.

Animals↗
PubMed2004

Motor recovery and anatomical evidence of axonal regrowth in spinal cord-repaired adult rats.

Behavioral assessments of hindlimb motor recovery and anatomical assessments of extended axons of long spinal tracts were conducted in adult rats following complete spinal cord transection. Rats were randomly divided into 3 groups: 1) sham control group (laminectomy only; n = 12); 2) transection-only group, spinal cord transection at T8 (n = 20); and 3) experimental treatment group, spinal cord transection at T8, with peripheral nerve grafts (PNG) and application of acidic fibroblast growth factor (aFGF) (n = 14). The locomotor behavior and stepping of all rats were analyzed over a 6-month survival time using the Basso, Beattie, Bresnahan (BBB) open field locomotor test and the contact placing test. Immunohistochemistry for serotonin (5-HT), anterograde tracing with biotinylated dextran amine (BDA), and retrograde tracing with fluoro-gold were used to evaluate the presence of axons below the damage site following treatment. When compared with the transection-only group, the nerve graft with the aFGF group showed 1) significant improvement in hindlimb locomotion and stepping, 2) the presence of 5-HT-labeled axons below the lesion site at lumbar cord level (these were interpreted as regenerated axons from the raphe nuclei), 3) the presence of anterograde BDA labeling of corticospinal tract axons at the graft site and below, and 4) fluoro-gold retrograde labeling of neuron populations in motor cortex and in red nucleus, reticulospinal nuclei, raphe nuclei, and vestibular nuclei. We conclude that peripheral nerve grafts and aFGF treatments facilitate the regrowth of the spinal axons and improve hindlimb function in a T-8 spinal cord-transected rat model.

Animals↗
PubMed2002

Neuronal inputs from the hypothalamus and brain stem to the medial preoptic area of the ram: neurochemical correlates and comparison to the ewe.

The retrograde tracer, FluoroGold, was used to trace the neuronal inputs from the septum, hypothalamus, and brain stem to the region of the GnRH neurons in the rostral preoptic area of the ram and to compare these imputs with those in the ewe. Sex differences were found in the number of retrogradely labeled cells in the dorsomedial and ventromedial nuclei. Retrogradely labeled cells were also observed in the lateral septum, preoptic area, organum vasculosum of the lamina terminalis, bed nucleus of the stria terminalis, stria terminalis, subfornical organ, periventricular nucleus, anterior hypothalamic area, lateral hypothalamus, arcuate nucleus, and posterior hypothalamus. These sex differences may partially explain sex differences in how GnRH secretion is regulated. Fluorescence immunohistochemistry was used to determine the neurochemical identity of some of these cells in the ram. Very few tyrosine hydroxylase-containing neurons in the A14 group (<1%), ACTH-containing neurons (<1%), and neuropeptide Y-containing neurons (1-5%) in the arcuate nucleus contained FluoroGold. The ventrolateral medulla and parabrachial nucleus contained the main populations of FluoroGold-containing neurons in the brain stem. Retrogradely labeled neurons were also observed in the nucleus of the solitary tract, dorsal raphe nucleus, and periaqueductal gray matter. Virtually all FluoroGold-containing cells in the ventrolateral medulla and about half of these cells in the nucleus of the solitary tract also stained for dopamine beta-hydroxylase. No other retrogradely labeled cells in the brain stem were noradrenergic. Although dopamine, beta-endorphin, and neuropeptide Y have been implicated in the regulation of GnRH secretion in males, it is unlikely that these neurotransmitters regulate GnRH secretion via direct inputs to GnRH neurons.

Adrenocorticotropic Hormone↗
PubMed2005

Expression of a dominant negative FGF receptor in developing GNRH1 neurons disrupts axon outgrowth and targeting to the median eminence.

During development, neurons that synthesize and release gonadotropin-releasing hormone (GNRH1) extend their axons to the median eminence (ME) to establish neurosecretory contacts necessary for hormone secretion. Signals that coordinate this process are not known, but could involve the activation of fibroblast growth factor receptors (FGFRs) expressed on developing GNRH1 neurons. Using both whole-animal and cell culture approaches, this study examines the direct role of FGFR signaling in the extension and guidance of GNRH1 axons to the ME. In vivo retrograde labeling with fluorogold (FG) first showed a significant reduction in the projections of GNRH1 axons to the circumventricular organs (including the ME) in transgenic mice expressing a dominant negative FGF receptor (dnFGFR) in GNRH1 neurons. Using a primary GNRH1 neuronal culture system, we examined if compromised axon extension and directional growth led to the reduced axon targeting efficiency seen in vivo. Primary cultures of GNRH1 neurons were established from Embryonic Day 15.5 embryos, an age when GNRH1 neurons are actively targeting the ME. Cultured GNRH1 neurons expressing dnFGFR (dnFGFR neurons) exhibited attenuated activation of signaling pathways and reduced neurite outgrowth in response to FGF2. Further, dnFGFR neurons failed to preferentially target neurites toward cocultured ME explant and FGF2-coated beads, suggesting a defect in axon pathfinding. Together, these findings describe a direct role of FGFR signaling in the elongation and guidance of GNRH1 axons to the ME.

Animals↗
PubMed1997

Gonadotropin-releasing hormone neural projections to the systemic vasculature during sexual maturation and delayed puberty in the male Djungarian hamster.

To study GnRH neuron projections to the systemic circulation during sexual maturation and in photoperiod-induced delayed puberty, we injected fluorogold (i.p.) into long- or short-day-reared male Djungarian hamsters. Five days after fluorogold treatment, at 15, 25, or 40 days of age, most GnRH neurons were found to access the systemic vasculature from terminal fields in the median eminence and organum vasculosum of the lamina terminalis. More than 80% of GnRH cell bodies in the medial preoptic area and diagonal band of Broca contained fluorogold, the locus for the majority of the GnRH neuron system in this species. GnRH cell numbers (approximately 180) and percentages with fluorogold were the same in 15- and 25-day-old males in long days, respectively pre-and peripubertal, and were not different from that in short-day hamsters with delayed puberty. Neither the number of fluorogold-labeled GnRH somata nor intensity of the fluorogold per cell was altered in hamsters during the critical period for initiation of reproductive maturation. Only later, at age 40 days, was the percentage of GnRH somata with fluorogold increased in long-day hamsters or reduced in 40-day-old males in short days relative to that in males at 15 days of age (same day length). The findings indicate that GnRH neuron projections to regions outside the blood-brain barrier are established before puberty and are independent of photoperiod control of reproductive development.

Animals↗
PubMed1997

Location, immunohistochemical features, and spinal connections of autonomic neurons innervating the rat seminal vesicles.

With the use of retrograde tracing techniques, selective spinal nerve transections, and immunohistochemistry to label noradrenergic and peptidergic pathways, this study has for the first time defined in detail the autonomic innervation to the rat seminal vesicles. The majority of this innervation originates from the bilateral major pelvic ganglia, whereas very few neurons are located in the accessory, inferior mesenteric, or paravertebral chain ganglia. Neuropeptide Y was the most abundant marker, followed by tyrosine hydroxylase (an enzyme involved in noradrenaline synthesis), and then vasoactive intestinal peptide. Sympathetic axons with tyrosine hydroxylase and neuropeptide Y supplied vascular and nonvascular smooth muscle whereas parasympathetic, cholinergic neuropeptide Y terminals were associated with the glandular epithelium. In contrast, vasoactive intestinal peptide was found only in cholinergic neurons, which may have either parasympathetic or sympathetic spinal connections. The latter were far more prevalent, demonstrating a substantial sympathetic cholinergic innervation to the seminal vesicles. Vasoactive intestinal peptide axons were associated with the glandular epithelia, as well as vascular and nonvascular smooth muscle. Axons associated with the secretory epithelia may regulate secretion or perhaps provide trophic support. Finally, acute damage to preganglionic sacral and lumbar nerves caused a transient increase in glandular weight.

Animals↗
PubMed2000

Cocaine- and amphetamine-regulated transcript peptide in the rat epididymis: an immunohistochemical and electrophysiological study.

Cocaine- and amphetamine-regulated transcript (CART) is a novel family of peptides, of which CART peptide fragments 55-102 and 62-102 are reported to be the endogenous, physiologically active peptides. Immunohistochemical studies with an antiserum directed against the CART peptide fragment 55-102 revealed CART-like immunoreactive (CART-LI) nerve fibers in the rat epididymis. The number was highest in the cauda epididymis and became progressively fewer toward the caput epididymis; the vas deferens exhibited an abundance of CART-LI fibers. Injection of the retrograde tracer Fluorogold (Fluorochrome, Inc., Englewood, CO) to the junction between the vas deferens and cauda epididymis labeled a large number of neurons in the major pelvic ganglion, some of which were CART-positive. Double-labeling the ganglion sections with tyrosine hydroxylase (TH) and CART antisera revealed that CART-LI and TH-LI were expressed in two distinct populations of ganglion cells. Some of the TH-LI cells in the ganglia, however, were covered with web-like CART-LI endings. The effects of CART peptide 55-102, referred to herein as CART, on anion secretion in the form of short circuit currents (Isc) were assessed in cultured epithelia. The CART (1 to 5 microM) applied to the basolateral or apical side of the cultured epithelia caused no significant responses on Isc, whereas lys-bradykinin (1 microM) produced a large Isc response in the same preparations. Our results show that CART-LI is present in a population of rat pelvic ganglion cells, which may give rise to CART-LI nerve fibers as observed in the vas deferens and the epididymis. The biological function of CART in the rat epididymis is not known, but it apparently is not involved in ion secretion across the epithelium.

Amphetamine↗
PubMed1988

Pyloroplasty divides vagus nerve fibers to the greater curvature of the stomach. An axonal tracing study.

Recent studies have demonstrated the location in the dorsal motor nucleus of the vagus nerve (dmnX) of nerve cells that project preganglionic efferent vagus nerve fibers to the greater curvature of the stomach. Although it is clear that these fibers are contained within the vagus nerve trunks, the intra-abdominal pathways of these fibers are unknown. When a neurotracer was applied to the right gastroepiploic pedicle, nerve cells in the bilateral dmnX were labeled. If a preliminary anterior or posterior pyloroplasty was performed before the application of the neurotracer, cellular labeling was seen on the right or left side of the dmnX, respectively. Furthermore, division of the anterior Latarjet nerve eliminated labeling in cells of the left dmnX. This study demonstrates that the preganglionic vagus nerve fibers within the right gastroepiploic pedicle traverse an intramural course across the pylorus and are contained in the Latarjet nerve.

Animals↗
PubMedDate not supplied

Locomotor projections from the pedunculopontine nucleus to the spinal cord.

Following injections of retrograde tracers into the spinal cord enlargements, the mesencephalic locomotor region (MLR) was electrically stimulated to induce locomotion in decerebrate rats. MLR sites coincided with cholinergic pedunculopontine nucleus (PPN) neurons, which were selectively labelled using NADPH diaphorase histochemistry. Retrogradely labelled (spinal-projecting) PPN neurons were scattered among cholinergic PPN neurons. The absence of retrogradely labelled, NADPH diaphorase positive PPN neurons indicates that spinal enlargement projections are non-cholinergic.

Animals↗
PubMedDate not supplied

Locomotor projections from the pedunculopontine nucleus to the medioventral medulla.

Retrograde tracers were injected into the rat medioventral medulla (MED) and the injection site was identified as a locomotion- inducing area by electrical stimulation in the decerebrate preparation. Histological reconstructions showed that about 10% of cholinergic pedunculopontine (PPN) and laterodorsal tegmental (LDT) neurons project to the MED. Also, large numbers of non-cholinergic cells in and around the PPN and LDT were found to project to the MED.

Animals↗
PubMed1991

Commissural neurons in the cat upper cervical spinal cord.

We have begun a study of the intrinsic circuitry of the cat's upper cervical cord, in part to elucidate the role of spinal interneurons in vestibulocollic reflexes. Using retrograde labelling with Fluoro-Gold and intraspinal microstimulation, we have identified commissural neurons projecting to the contralateral ventral horn. Neurons tended to be in the medial half of lamina VIII. Approximately half of the neurons were propriospinal neurons that could be activated antidromically from the rostral border of the cervical enlargement. Most of the tested, spontaneously active neurons were driven by stimulation of the ipsi- and/or contralateral vestibular nerve, in some cases disynaptically.

Animals↗
PubMed1993

Neuronal subpopulations in a reptilian thalamic reticular nucleus.

In reptiles, Caiman crocodilus, some neurons in the thalamic reticular nucleus are immunoreactive for parvalbumin. Utilizing double-labeling experiments with fluorescent tracers and indirect fluorescence immunocytochemistry, some of these parvalbumin immunoreactive neurons were found to project to the dorsal thalamus. Other thalamic reticular neurons not immunoreactive for parvalbumin were also found to terminate in the dorsal thalamus. These findings suggest that the thalamic reticular nucleus in Caiman contains at least two chemically, and perhaps functionally, distinct neuronal subpopulations.

Animals↗
PubMed1994

Cerebellar injury induces NOS in Purkinje cells and cerebellar afferent neurons.

Purkinje cells of the cerebellar cortex and neurons of most precerebellar nuclei are conspicuous by the absence of constitutive (neuronal) nitrix oxide synthase (nNOS). Here we show that following mechanical, chemical or thermal injury to the cerebellar cortex there is an induction of nNOS in Purkinje cells as identified with NADPH-diaphorase (NADPH-d) histochemistry and nNOS immunocytochemistry. Induced nNOS and NADPH-d (inNOS/NADPH-d) first appeared 72 hours post-treatment and persisted in excess of 8 weeks. Precerebellar neurons throughout the brain stem also exhibited induced nNOS and NADPH-d with a similar time course. These results indicate that brain lesions can induce nNOS in local neurons and in neurons which are afferent to the leasioned area.

Amino Acid Oxidoreductases↗
PubMed1995

CGRP in peripherally axotomized mesencephalic trigeminal neurones of the rat.

Immunoreactivities for substance P (SP-ir) and calcitonin gene-related peptide (CGRP-ir) were examined in neurones in the mesencephalic trigeminal tract nucleus of nerve-injured rats. One week following unilateral transection of the trigeminal root, the masseteric nerve (MN) or the inferior alveolar nerve (IAN), CGRP-ir but not SP-ir was detected in these neurones bilaterally with ipsilateral dominance. Most of the CGRP-ir (immunoreactive) neurones were retrogradely labelled when fluorogold (FG) had been applied to the proximal stump of the MN or the IAN. Sham surgery including insult to the masseter muscle induced CGRP-ir while skin incision did not.

Animals↗
PubMed1998

Sensory neurons regenerate more dominantly than motoneurons during the initial stage of the regenerating process after peripheral axotomy.

This study was designed to determine whether sensory neurons or motoneurons were dominant during the earlier stage of the regeneration process after peripheral axotomy. After transection of the right sciatic nerves of rats, epineurial end neurorrhaphy was performed. At 5, 7 and 14 days postoperatively, the nerves were re-transected at the positive pinch site, and their proximal stumps were exposed to the retrograde neurotracer, Fluoro-Gold (F-G). Seventy-two hours later, the lumbar spinal cords and the L4 and L5 dorsal root ganglia (DRG) were harvested and evaluated. The incidence and the intensity of F-G labelling in DRG were significantly higher than in anterior horns (AH). These results demonstrated that sensory neurons were more dominant than motoneurons in nerve regeneration.

Animals↗
PubMed1999

Focal hippocampal gain of NGF function elicits specific septal cholinergic reorganization.

The influence of NGF on the neuroanatomic substrate(s) subserving learning and memory was probed by somatic mosaic analysis. NGF XAT mice underwent unilateral hippocampal delivery of virus vector expressing cre recombinase to produce focal NGF gain of function mosaics. Activated mice expressing increased NGF, but not control mice transduced with the lacZ gene showed reorganization of the septohippocampal projection assessed by retrograde labeling with Fluorogold (FG). Mice mosaic for NGF function demonstrated in ipsilateral medial septum and diagonal band significant increases in FG-labeled cell bodies (94%), ChAT-labeled cells (55%), double-positive cells (190%) and increased somal size of double-positive cells (56%) than did non-activated mice. These results indicate that reorganization of the cholinergic septal input to a specific hippocampal region is promoted by gain of NGF function.

Animals↗
PubMed1999

First and second order maternal behavior related afferents of the lateral habenula.

We demonstrated previously that the lateral habenula (Lhb) mediates maternal behavior. Our present goal was to identify the first and second order afferent connections of the Lhb, particularly those relevant for maternal behavior. Using pseudorabies virus (PRV) as a retrograde transneuronal tracer and the retrograde tracer Fluoro-Gold, we identified first order Lhb afferent projections from the lateral preoptic area, bed nucleus of the stria terminalis, nucleus accumbens and ventral tegmental area, each important for the display of maternal behavior. Maternally relevant second order neurons originated from the medial preoptic area and amygdala. Additional regions with first and second order neurons afferent to the Lhb were also identified.

Afferent Pathways↗
PubMed1999

Laminar-selective noradrenergic and serotoninergic modulation includes spinoparabrachial cells after inflammation.

We evaluated the effects of chemical lesions on hindpaw inflammation-induced Fos protein expression in spinoparabrachial neurons that were retrogradely labeled by Fluoro-Gold. The descending serotoninergic and noradrenergic pathways were destroyed by the selective neurotoxins, 5,7-DHT and DSP-4, respectively. After 5,7-DHT treatment there was a significant increase in double-labeled neurons only in the lateral reticulated neck of the dorsal horn 24h after inflammation compared with vehicle-injected controls. In contrast, the DSP-4 treatment resulted in a more robust increase in double-labeled neurons in the ipsilateral superficial dorsal horn than in the neck of the dorsal horn. These results indicate that after inflammation the enhanced modulation from descending serotoninergic and noradrenergic pathways targets supraspinally projecting neurons to dampen increased ascending nociceptive input. Further, these pathways differentially suppress the responses of spinoparabrachial neurons in the deep and superficial dorsal horn.

5,7-Dihydroxytryptamine↗