Transganglionic transport of the lectin Soybean agglutinin (Glycine max) following injection into the sciatic nerve of the adult rat

The lectin soybean agglutinin (SBA) from Glycine max binds to small-sized dorsal root ganglion cells and their central terminals in the superficial dorsal horn of the spinal cord. Here we investigated the ability of SBA and SBA conjugated to horseradish peroxidase(SBA-HRP) to trace thin calibre afferents into the spinal cord from a peripheral nerve. Following injection into the sciatic nerve, labelled cells in the dorsal root ganglion were predominantly small-sized but some medium-sized cells were also labelled. Colocalisation studies of transported SBA with various neuronal markers showed that all neurons that transported SBA-HRP showed SBA binding, indicating high uptake specificity for the conjugate. 15% were immunoreactive for RT97 indicating that some axons were myelinated, and 54% also expressed binding sites for isolectin B4 from Griffonia simplicifolia, a selective marker for a subpopulation of unmyelinated afferents. With regard to neurotransmitter content, 43% of the SBA cells contained calcitonin gene-related peptide, 33% contained substance P and 2.5% somatostatin. In addition, 3% contained carbonic anhydrase. Centrally, injection of SBA in the sciatic nerve resulted in labelled terminals in somatotopically appropriate regions of laminae I–II of the dorsal horn, and in the gracile nucleus. A few neurons in the dorsal horn were labelled indicating that some transneuronal transport of SBA had occurred. The results show that SBA can be used as a transganglionic tracer to label fine calibre primary afferents that project to laminae I–II of the spinal cord and the gracile nucleus. It appears to label more afferents than isolectin B4, including also a subpopulation of myelinated afferents.     

Ulex europaeus agglutinin-I binding to dental primary afferent projections in the spinal trigeminal complex combined with double immunolabeling of substance P and GABA elements using peroxidase and colloidal gold

Ulex europaeus agglutinin I (UEA-I) is a plant lectin with an affinity for L-fucosyl residues in the chains of lactoseries oligosaccharides associated with medium- and smaller-diameter dorsal root ganglion neurons and their axonal processes. These enter Lissauer's tract and terminate within the superficial laminae of the spinal cord overlapping projections known to have a nociceptive function. This implies that the surface coatings of neuronal membranes may have a relationship with functional modalities. The present investigation further examined this concept by studying a neuronal projection with a nociceptive function to determine whether fucosyl-lactoseries residues were incorporated in its primary afferent terminals. Transganglionic transport of horseradish peroxidase (HRP) following injection into tooth pulp chambers was employed to demonstrate dental pulp terminals in the trigeminal spinal complex, while peroxidase and fluorescent tags were used concomitantly to stain for UEA-I. Double immunolabeling for substance P (SP) and gamma-aminobutyric acid (GABA) using peroxidase and colloidal gold allowed a comparison of the distribution of a known excitatory nociceptive transmitter with that of UEA-I binding in specific subnuclei. Synaptic interrelationships between UEA-I positive dental pulp primary afferent inputs and specific inhibitory terminals were also examined. SP immunoreactivity occurred in laminae I and outer lamina II (IIo) of subnucleus caudalis (Vc) and in the ventrolateral and lateral marginal region of the caudal half of subnucleus interpolaris (Vi), including the periobex area in which Vi is slightly overlapped on its lateral aspect by cellular elements of Vc. The adjacent interstitial nucleus (IN) also showed an intense immunoreactivity for this peptide antibody. UEA-I binding displayed a similar distribution pattern in both Vc and Vi, but extended into lamina IIi and the superficial part of Lamina III in Vc. Dental pulp terminals were found to have a comparable distribution; however, many extended into the dorsal portion of the caudal half of Vi and the ventromedial quadrant of rostral Vi. Electron-microscopic analysis showed that transganglionically labeled dental pulp terminals contained ovoid, complex membrane-bound vacuoles laden with transported HRP. The preterminal axon and synaptic membranes of those dental pulp terminals located in zones of Vc and Vi displaying an affinity for UEA-I were usually characterized by a patchy, electron-dense coating of the peroxidase tag. SP was demonstrated ultrastructurally with Protein-A colloidal gold (3-nm particles), whereas GABA immunoreactivity was revealed by the avidin-biotin-peroxidase method.(ABSTRACT TRUNCATED AT 400 WORDS)     

Modulation of sensory input to the spinal cord by presynaptic ionotropic glutamate receptors

Sensory input from peripheral nerves to the dorsal horn of the spinal cord is mediated by a variety of agents released by the central terminals of dorsal root ganglion (DRG) neurons. These include, but are not limited to, amino acids, especially glutamate, peptides and purines. The unraveling of the mechanisms of synaptic transmission by central terminals of DRG neurons has to take into account various ways in which the message from the periphery can be modulated at the level of the first central synapse. These include postsynaptic and presynaptic mechanisms. Homomeric and heteromeric complexes of receptor subunits for the different transmitters released by DRG neurons and interneurons, clustered at the postsynaptic site of central synapses, can be expressed in different combinations and their rate of insertion into the postsynaptic membrane is activity-regulated. Inhibitory mechanisms are an important part of central modulation, especially via presynaptic inhibition, currently believed to involve GABA released by inhibitory intrinsic neurons. Recent work has established the occurrence of another way by which sensory input can be modulated, i.e. the expression of presynaptic ionotropic and metabotropic receptors in central terminals of DRG neurons. Microscopic evidence for the expression, in these terminals, of various subunits of ionotropic glutamate receptors documents the selective expression of glutamate receptors in functionally different DRG afferents. Electrophysiological and pharmacological data suggest that activation of presynaptic ionotropic glutamate receptors in central terminals of DRG neurons may result in inhibition of release of glutamate by the same terminals. Glutamate activating presynaptic receptors may spill over from the same or adjacent synapses, or may be released by processes of astroglial cells surrounding synaptic terminals. The wide expression of presynaptic ionotropic glutamate receptors, especially in superficial laminae of the dorsal horn, where Adelta- and C fibers terminate, provides an additional or alternative mechanism, besides GABA-mediated presynaptic inhibition, for the modulation of glutamate release by these fibers. Since, however, presynaptic ionotropic glutamate receptors are also expressed in terminals of GABAergic intrinsic interneurons, a decrease of GABA release resulting from activation of these receptors in the same laminae, may also play a role in central sensitization and hyperalgesia.     

Synaptic organization of substance P, glutamate and GABA-immunoreactive boutons on functionally identified neurons in cat spinal deeper dorsal horn

In order to determine how nociceptive input conveyed by the C-fibers terminating in superficial lam-inae of the spinal cord reaches the wide dynamic range (WDR) cells in deeper dorsal horn, which functions as ascend-ing projection pathway, the morphological features of some WDR cells in the deeper dorsal horn of the cat lumbar spinal cord were studied by intracellular injection of horseradish peroxidase and physiological characterization. One of the fully stained neurons with somata in lamina V and dendrites that entered lamina Ⅱ were examined by electron mi-croscopy. Immunogold staining of ultrathin sections through the labeled proximal dendrites in lamina Ⅱ revealed that these dendrites received numerous synapses from substance P and glutamate immunoreactive (IR) axons, which were considered originating from C-fibers. In addition, many GABA-IR terminals were found presynaptic to the labeled dendrites. The results, therefore, suggest that the information carried by primary afferent can be sent from t     

Ulex europaeus Agglutinin-I Binding to Dental Primary Afferent Projections in the Spinal Trigeminal Complex Combined with Double Immunolabeling of Substance P and GABA Elements Using Peroxidase and Colloidal Gold

Ulex europaeus agglutinin I (UEA-I) is a plant lectin with an affinity for L-fucosyl residues in the chains of lactoseries oligosaccharides associated with medium and smaller-diameter dorsal root ganglion neurons and their axonal processes. These enter Lissauer's tract and terminate within the superficial laminae of the spinal cord overlapping projections known to have a nociceptive function. This implies that the surface coatings of neuronal membranes may have a relationship with functional modalities. The present investigation further examined this concept by studying a neuronal projection with a nociceptive function to determine whether fucosyl-lactoseries residues were incorporated in its primary afferent terminals. Transganglionic transport of horseradish peroxidase (HRP) following injection into tooth pulp chambers was employed to demonstrate dental pulp terminals in the trigeminal spinal complex, while peroxidase and fluorescent tags were used concomitantly to stain for UEA-I. Double immunolabeling for substance P (SP) and γ-aminobutyric acid (GABA) using peroxidase and colloidal gold allowed a comparison of the distribution of a known excitatory nociceptive transmitter with that of UEA-I binding in specific subnuclei. Synaptic interrelationships between UEA-I positive dental pulp primary afferent inputs and specific inhibitory terminals were also examined.

SP immunoreactivity occurred in laminae I and outer lamina II (II_o) of subnucleus caudalis (Vc) and in the ventrolateral and lateral marginal region of the caudal half of subnucleus interpolaris (Vi), including the periobex area in which Vi is slightly overlapped on its lateral aspect by cellular elements of Vc. The adjacent interstitial nucleus (IN) also showed an intense immunoreactivity for this peptide antibody. UEA-I binding displayed a similar distribution pattern in both Vc and Vi, but extended into lamina II; and the superficial part of Lamina III in Vc. Dental pulp terminals were found to have a comparable distribution; however, many extended into the dorsal portion of the caudal half of Vi and the ventromedial quadrant of rostral Vi.

Electron-microscopic analysis showed that transganglionically labeled dental pulp terminals contained ovoid, complex membrane-bound vacuoles laden with transported HRP. The preterminal axon and synaptic membranes of those dental pulp terminals located in zones of Vc and Vi displaying an affinity for UEA-I were usually characterized by a patchy, electron-dense coating of the peroxidase tag. SP was demonstrated ultrastructurally with Protein-A colloidal gold (3-nm particles), whereas GABA immunoreactivity was revealed by the avidin—biotin—peroxidase method. This combined approach labeled a variety of simple axodendritic to large complex scalloped dental terminals which contained SP and were shown to have a UEA-I affinity. In addition, many of the larger terminals formed contacts with GABA-ergic dendrites and received inputs from GABA-ergic synapses. These complexes were most concentrated in lamina II_o of Vc and the ventrolateral zone of Vi. Many terminals in laminae II_i; and III with a UEA-I-positive surface coating failed to bind with the antiserum for SP, indicating that other transmitters may colocalize with UEA-I and suggesting that absolute correlations between specific oligosaccharide plasmalemmal coatings and functional modalities should be approached with caution. Further studies employing antisera to different transmitters are currently underway to better define the relationship between transmitter localization and anatomical substrates within this circuitry. These studies should eventually provide additional clues about relationships between functional properties and oligosaccharide coatings of primary afferent projections.     

Interferon-γ receptors are expressed at synapses in the rat superficial dorsal horn and lateral spinal nucleus

Summary Interferon-γ can facilitate the spinal nociceptive flexor reflex and elicit neuropathic pain-related behavior in rats and mice. Immunoreactivity for the interferon-γ receptor (IFN-γR) occurs in the superficial layers of the dorsal horn and the lateral spinal nucleus in the rat and mouse spinal cord, as well as in subsets of neurons in the dorsal root ganglia. The aim of the present study was to examine the cellular localization and origin of the IFN-γR in the spinal cord. As viewed by confocal microscopy, the immunopositivity for the IFN-γR was co-localized with that of the presynaptic marker synaptophysin and with neuronal nitric oxide synthase in the lateral spinal nucleus, whereas only a minor overlap with these molecules was observed in laminae I and II of the dorsal horn. There was no co-localization of the IFN-γR with markers for astrocytes and microglial cells. Ultrastructurally, the IFN-γR was found predominantly in axon terminals in the lateral spinal nucleus but also at postsynaptic sites in dendrites in laminae I and II. The IFN-γR expressed in neurons in dorsal root ganglia was transported in axons both centrally and peripherally. Hemisection of the spinal cord caused no reduction in immunolabelling of the IFN-γR in the dorsal horn or the lateral spinal nucleus. Since rhizotomy does not effect the immunolabelling in the lateral spinal nucleus, our observation indicates that the presynaptic receptors in this nucleus are derived from intrinsic neurons. The localization of the IFN-γR in the spinal cord differed from that of the AMPA glutamate receptor subunits 2 and 3 and the substance P receptor (NK1). Our results, showing localization of IFN-γR to pre- and postsynaptic sites in the dorsal horn and lateral spinal nucleus indicate that IFN-γ can modulate nociception at the spinal cord level.     

Immunocytochemical identification of axons containing coexistent serotonin and substance P in the cat lumbar spinal cord

Axons containing both serotonin-like (5-HT)-LI and substance P-like (SP)-LI immunoreactivity were identified in all laminae of the cat spinal cord at the level of the lumbar enlargement. Using an immunologically-specific, double immunofluorescence method, coexistent 5-HT-LI and SP-LI immunoreactivity could be visualized in the same tissue section with appropriate FITC and rhodamine fluorescent filter sets. The fewest number of coexistent axons were observed in the superficial laminae of the dorsal horn, while their number increased in the more ventral dorsal horn laminae. Numerous coexistent axons were observed in the area adjacent to the central canal. The greatest number of coexistent axons was found in the ventral horn, especially in the motoneuronal cell groups. This study demonstrates that axons containing coexistent 5-HT-LI and SP-LI immunoreactivity are found in all laminae of the cat lumbar spinal cord and are thus involved in both sensory and motor functions. Their more frequent occurrence in the ventral horn suggests a greater role for coexistent 5-HT and SP in motor function. Since axons containing coexistent 5-HT and SP, and those containing only 5-HT, likely originate from different populations of neurons, our observations provide evidence for a diverse origin of descending 5-HT afferents to the different spinal laminae.     

Modulation of cardiac ischemia-sensitive afferent neuron signaling by preemptive C2 spinal cord stimulation: effect on substance P release from rat spinal cord

The upper cervical spinal region functions as an intraspinal controller of thoracic spinal reflexes and contributes to neuronal regulation of the ischemic myocardium. Our objective was to determine whether stimulation of the C2 cervical spinal cord (SCS) of rats modified the input signal at the thoracic spinal cord when cardiac ischemia-sensitive (sympathetic) afferents were activated by transient occlusion of the left anterior descending coronary artery (CoAO). Changes in c-Fos expression were used as an index of neuronal activation within the spinal cord and brain stem. The pattern of substance P (SP) release, a putative nociceptive transmitter, was measured using antibody-coated microprobes. Two SCS protocols were used: reactive SCS, applied concurrently with intermittent CoAO and preemptive, sustained SCS starting 15 min before and continuing during the repeated intermittent CoAO. CoAO increased SP release from laminae I and II in the T4 spinal cord above resting levels. Intermittent SCS with CoAO resulted in greater levels of SP release from deeper laminae IV-VII in T4 than CoAO alone. In contrast, SP release from laminae I and II was inhibited when CoAO was applied during preemptive, sustained SCS. Preemptive SCS likewise reduced c-Fos expression in the T4 spinal cord (laminae I-V) and nucleus tractus solitarius but increased expression in the intermediolateral cell column of T4 compared with CoAO alone. These results suggest that preemptive SCS from the high cervical region modulates sensory afferent signaling from the ischemic myocardium.     

Experimental morphological study of primary afferent terminals at the base of the dorsal horn of the cat spinal cord

The distribution and ultrastructure of primary afferent terminals in the gray matter of the cervical and lumbar regions of the cat spinal cord were studied by the experimental degeneration method of Fink and Heimer. Most preterminals of primary afferents were shown to be concentrated in the region of the intermediate nucleus of Cajal (central part of Rexed's laminae VI–VII), in the substantial gelatinosa (laminae II–III), and in the nucleus proprius of the dorsal horn (central and medial parts of lamina IV). Fewer are found in the region of the motor nuclei. The number of degenerating axon terminals in the lateral parts of laminae IV and V differed: 31.5 and 0.4% respectively of all axon terminals. Many terminals of primary afferents in lamina IV contribute to the formation of glomerular structures in which they exist as terminals of S-type forming axo-axonal connections with other terminals. These results are in agreement with electrophysiological data to show that interneurons in different parts of the base of the dorsal horn differ significantly in the relative numbers of synaptic inputs formed by peripheral afferents and descending systems.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 5, No. 4, pp. 406–414, July–August, 1973.     

Projection of cervical dorsal root fibers to the medulla oblongata in the brush-tailed possum, Trichosurus vulpecula

This study describes the projection of cervical spinal afferent nerve fibers to the medulla in the brush-tailed possum, a marsupial mammal. After single dorsal roots (between C2 and T1) were cut in a series of animals, the Fink-Heimer method was used to demonstrate the projection fields of fibers entering the CNS via specific dorsal roots. In the high cervical spinal cord, afferent fibers from each dorsal root form a discrete layer in the dorsal funiculus. The flattened laminae from upper cervical levels are lateral and those from lower cervical levels are medial within the dorsal columns. All afferent fibers at this level are separated from gray matter by the corticospinal fibers in the dorsal funiculus. All cervical roots project throughout most of the length of the well-developed main cuneate nucleus in a loosely segmentotopic fashion. Fibers from rostral roots enter more lateral parts of the nucleus, and fibers from lower levels pass to more medial areas; but terminal projection fields are typically large and overlap extensively. At more rostral medullary levels, fibers from all cervical dorsal roots also reach the external cuneate nucleus. The spatial arrangement here is more complex and more extensively overlapped than in the cuneate nucleus. Rostral cervical root fibers reach ventral and ventrolateral areas of the external cuneate nucleus and continue to its rostral pole; more caudal root fibers project to more dorsal and medial regions within the nucleus. These results demonstrate that projection patterns of spinal afferents in this marsupial are similar to those seen in the few placental species for which detailed data concerning this system are available.     

Neuroanatomy of morphine-modulating peptides

Antisera against two mammalian peptides related to the molluscan cardioexcitatory peptide Phe-Met-Arg-Phe-NH2 were used to locate immunoreactive neurons in the rat brain, nerve fibres and terminals in the spinal cord, sympathetic ganglion cells and adrenal chromaffin cells. Immunoreactivity for the newly characterised octa- and octadecapeptide was detected in nerve cell bodies in the hypothalamic area, including parts of the dorsomedial, periventricular and paraventricular nuclei, and in the nucleus tractus solitarii. Nerve terminals in the superficial laminae of the spinal cord were also immunoreactive for these peptides, while the sensory ganglia were nonreactive. Some principal ganglion cells in the superior cervical ganglia exhibited bright immunofluorescence for the peptides, and a few adrenal medullary cells were immunoreactive. The presence of these peptides in the substantia gelatinosa of the spinal cord suggests that they may be involved in sensory neurotransmission, especially in the mechanisms mediating pain. In the hypothalamo-hypophysial system these peptides may be involved in the regulation of hormonal systems. They may also act as co-transmitters in the sympathetic nervous system.     

Sustained neurochemical plasticity in central terminals of mouse DRG neurons following colitis

Sensitization of dorsal root ganglia (DRG) neurons is an important mechanism underlying the expression of chronic abdominal pain caused by intestinal inflammation. Most studies have focused on changes in the peripheral terminals of DRG neurons in the inflamed intestine but recent evidence suggests that the sprouting of central nerve terminals in the dorsal horn is also important. Therefore, we examine the time course and reversibility of changes in the distribution of immunoreactivity for substance P (SP), a marker of the central terminals of DRG neurons, in the spinal cord during and following dextran sulphate sodium (DSS)-induced colitis in mice. Acute and chronic treatment with DSS significantly increased SP immunoreactivity in thoracic and lumbosacral spinal cord segments. This increase developed over several weeks and was evident in both the superficial laminae of the dorsal horn and in lamina X. These increases persisted for 5 weeks following cessation of both the acute and chronic models. The increase in SP immunoreactivity was not observed in segments of the cervical spinal cord, which were not innervated by the axons of colonic afferent neurons. DRG neurons dissociated following acute DSS-colitis exhibited increased neurite sprouting compared with neurons dissociated from control mice. These data suggest significant colitis-induced enhancements in neuropeptide expression in DRG neuron central terminals. Such neurotransmitter plasticity persists beyond the period of active inflammation and might contribute to a sustained increase in nociceptive signaling following the resolution of inflammation.     

Endomorphin-2 is an endogenous opioid in primary sensory afferent fibers

Evidence is presented that the recently discovered endogenous mu-selective agonist, endomorphin-2, is localized in primary sensory afferents. Endomorphin-2-like immunoreactivity was found to be colocalized in a subset of substance P- and mu opiate receptor-containing fibers in the superficial laminae of the spinal cord and spinal trigeminal nucleus. Disruption of primary sensory afferents by mechanical (deafferentation by dorsal rhizotomy) or chemical (exposure to the primary afferent neurotoxin, capsaicin) methods virtually abolished endomorphin-2-like immunoreactivity in the dorsal horn. These results indicate that endomorphin-2 is present in primary afferent fibers where it can serve as the endogenous ligand for pre- and postsynaptic mu receptors and as a major modulator of pain perception.     

大鼠脑内代谢型谷氨酸受体5亚型(mGluR5)定位分布的免疫细胞化学研究

本研究用免疫细胞化学技术观察了大鼠脑内参与兴奋性突触传递的代谢型谷氨酸受体5亚型(mGluR5)的精确定位分布.mGluR5阳性浓染的神经元胞体和纤维密集地分布于大脑皮质浅层、嗅球、伏核、尾壳核、前脑基底部、隔区、苍白球、腹侧苍白球、海马CA1和CA2区、下丘中央核、被盖背侧核和三叉神经脊束核尾侧亚核浅层;淡染而稀疏的mGluR5阳性神经元胞体和纤维见于屏状核、终纹床核、杏仁中央核、丘脑部分核团、上丘浅灰质层、外侧丘系背侧核和延髓中央灰质.     

吗啡耐受增加福尔马林致痛大鼠脊髓Fos和NADPH-d阳性神经元的表达

运用Ｆｏｓ免疫组织化学、ＮＡＤＰＨ－ｄ组织化学及Ｆｏｓ／ＮＡＤＰＨ－ｄ双标技术,研究了吗啡耐受对福尔马林致痛大鼠脊髓Ｆｏｓ、ＮＡＤＰＨ－ｄ阳性及Ｆｏｓ／ＮＡＤＰＨ－ｄ双标神经元表达的影响。结果观察到：在非吗啡耐受大鼠,福尔马林诱发的Ｆｏｓ－ｌｉｋｅ ｉｍｍｕｎｏｒｅａｃｔｉｖｉｔｙ（Ｆｏｓ－ＬＩ）主要分布在同侧脊髓背角浅层和颈部,急性静注吗啡可减少Ｆｏｓ－ＬＩ表达;长时间应用吗啡导致福尔马林诱发的     

The effects of long-standing limb loss on anatomical reorganization of the somatosensory afferents in the brainstem and spinal cord

We examined the terminations of sensory afferents in the brainstem and spinal cord of squirrel monkeys and prosimian galagos 4-8 years after a therapeutic forelimb or hindlimb amputation within 2 months of birth. In each animal, the distributions of labeled sensory afferent terminations from remaining body parts proximal to the limb stump were much more extensive than in normal animals. These sprouted afferents extended into the portions of the dorsal horn of the spinal cord as well as the cuneate and external cuneate nuclei of the brainstem (forelimb amputees) or spinal Clarke's column (hindlimb amputee) related to the amputated limb. Such reorganization in sensory afferents along with reorganization of the motor efferents to muscles (Wu and Kaas, J Neurosci 19: 7679-7697, 1999, Neuron 28: 967-978, 2000) may provide a basis for mislocated phantom sensations of missing forelimb movements accompanying actual shoulder movements during cortical stimulation or movement imagery in patients with amputations.     

Postnatal developmental expressions of neurotransmitters and receptors in various brain stem nuclei of rats.

Previously, we reported that the expression of cytochrome oxidase in a number of brain stem nuclei exhibited a plateau or reduction at postnatal day (P) 3-4 and a dramatic decrease at P12, against a general increase with age. The present study examined the expression of glutamate, N-methyl-D-aspartate receptor subunit 1 (NMDAR1), GABA, GABAB receptors, glycine receptors, and glutamate receptor subunit 2 (GluR2) in the ventrolateral subnucleus of the solitary tract nucleus, nucleus ambiguus, hypoglossal nucleus, medial accessory olivary nucleus, dorsal motor nucleus of the vagus, and cuneate nucleus, from P2 to P21 in rats. Results showed that 1) the expression of glutamate increased with age in a majority of the nuclei, whereas that of NMDAR1 showed heterogeneity among the nuclei; 2) GABA and GABAB expressions decreased with age, whereas that of glycine receptors increased with age; 3) GluR2 showed two peaks, at P3-4 and P12; and 4) glutamate and NMDAR1 showed a significant reduction, whereas GABA, GABAB receptors, glycine receptors, and GluR2 exhibited a concomitant increase at P12. These features were present but less pronounced in hypoglossal nucleus and dorsal motor nucleus of the vagus and were absent in the cuneate nucleus. These data suggest that brain stem nuclei, directly or indirectly related to respiratory control, share a common developmental trend with the pre-Botzinger complex in having a transient period of imbalance between inhibitory and excitatory drives at P12. During this critical period, the respiratory system may be more vulnerable to excessive exogenous stressors.     

The effects of long-standing limb loss on anatomical reorganization of the somatosensory afferents in the brainstem and spinal cord

We examined the terminations of sensory afferents in the brainstem and spinal cord of squirrel monkeys and prosimian galagos 4-8 years after a therapeutic forelimb or hindlimb amputation within 2 months of birth. In each animal, the distributions of labeled sensory afferent terminations from remaining body parts proximal to the limb stump were much more extensive than in normal animals. These sprouted afferents extended into the portions of the dorsal horn of the spinal cord as well as the cuneate and external cuneate nuclei of the brainstem (forelimb amputees) or spinal Clarke's column (hindlimb amputee) related to the amputated limb. Such reorganization in sensory afferents along with reorganization of the motor efferents to muscles (Wu and Kaas, J Neurosci 19 : 7679-7697, 1999, Neuron 28 : 967-978, 2000) may provide a basis for mislocated phantom sensations of missing forelimb movements accompanying actual shoulder movements during cortical stimulation or movement imagery in patients with amputations.     

Distribution and origin of bombesin,substance P and somatostatin in cat spinal cord

Bombesin (BN), substance P-(SP) and somatostatin (SRIF) were measured in individual laminae of the cervical, thoracic and lumbar (L) spinal cord of control cats, and in the L6 segment of cats receiving a spinal hemisection (L2) or deafferentation via dorsal rhizotomy at L6, 7, S1. The interlaminar distribution of BN, SP, and SRIF was remarkably similar. Highest concentrations were found in the superficial dorsal horn, and progressively less was found proceeding ventrally. Some intersegmental variations in peptide concentration within a single lamina were found. Dorsal rhizotomy caused a significant decline in BN, SP and SRIF in lamina I-III, therefore all three peptides appear to be contained in dorsal root ganglion cells. Evidence is presented for the existence of ascending BN and SP projections originating in lamina I-III and VII, for a descending SRIF pathway terminating in lamina VIII, and for an ascending BN path in lamina VIII. Dorsal root afferents to lamina VIII influence levels of BN, SP and SRIF.