Immunohistochemical evidence for separate populations of somatostatin-containing and substance P-containing primary afferent neurons in the rat

Further studies on the actions of endothelin-1 on blood flow in human skin

When injected into human skin, endothelin-1 produces intense vasoconstriction localized to the site of the injection, but this area of vasoconstriction is surrounded by vasodilatation which spreads several centimetres from the injection site. The vasodilatation induced by intradermal injection of endothelin-1 (63 pmol) into human skin is prevented by local anaesthetic. Pretreatment of human skin with capsaicin also inhibits this response. Pretreatment of subjects with the selective histamine H1-receptor antagonist cetirizine, 10 mg orally 4 h before intradermal injections, inhibited vasodilatation caused by the intradermal injection of histamine (750 pmol), endothelin-1 (63 pmol), and carbachol (750 pmol). Endothelin-1 (0.3-10 microM) and carbachol (1-30 microM) failed to induce histamine release from rat peritoneal mast cells. We conclude that the vasodilatation caused by intradermal injection of endothelin-1 into human skin is neurogenic and is probably mediated by neuropeptide-containing primary afferent neurones. Because neither carbachol nor endothelin-1 cause histamine release from mast cells, our data suggest that histamine release from mast cells at the effector end of the axon reflex is responsible for the carbachol- and endothelin-induced vasodilatation in human skin.

Neurogenic inflammation and asthma

The release of neurotransmitters may exacerbate the inflammatory response. Such neurogenic inflammation has been documented in a number of inflammatory diseases. Neurogenic inflammation due to release of neuropeptides from sensory nerves has been demonstrated in airways of several species, particularly rodents, and may contribute to the inflammatory response in asthmatic airways. Tachykinins (substance P and neurokinin A) released from airway sensory nerves may cause bronchoconstriction, vasodilatation, plasma exudation, and mucus secretion, whereas another sensory neuropeptide, calcitonin generelated peptide, may contribute to hyperemia of inflammation. Airway epithelial damage in asthma exposes sensory nerves which may become sensitized by inflammatory products (including prostaglandins and cytokines) so that neuropeptides are released via a local reflex trigger such as bradykinin, resulting in exaggerated inflammation. The effects of tachykinins may be amplified further by loss of the major degrading enzyme, neutral endopeptidase, from epithelial cells. Direct evidence for neurogenic inflammation in asthma is still awaited, however. Several strategies for reducing neurogenic inflammation are possible, particularly inhibition of neuropeptide release from sensory nerves by stimulating prejunctional receptors such as mu-opioid receptors.

Intravenously infused substance P enhances basal and growth hormone (GH) releasing hormone-stimulated GH secretion in normal men

The effect of synthetic substance P (SP), infused intravenously (IV) in doses of 0.5, 1, or 1.5 pmol/kg-1/min-1 over 60 min, on GH secretion was evaluated in seven healthy men. Substance P tests and a control test with normal saline were randomly performed at weekly intervals. No untoward side effects or changes in blood pressure were observed during SP infusions. Serum GH concentrations did not change when normal saline, the lowest dose, or the middle dose of SP were infused. In contrast, GH levels rose significantly when the highest dose of SP was given, with a mean peak two times higher than baseline. Further studies were performed to test the possible influence of SP on the GH response to GH-RH. For this purpose, seven other healthy men were tested with GH-RH (1 micrograms/kg body weight in an IV bolus) during saline or SP (1.5 pmol/Kg-1/min-1 x 60 min) infusion. The GH-RH induced a significant GH rise, with a mean peak seven times higher than baseline. When subjects were infused with SP, the GH response to GH-RH was greatly enhanced, with a mean peak 12 times higher than baseline. These results demonstrate for the first time in humans that the systemic infusion of SP stimulates GH secretion, and suggest that SP might interact with GH-RH in the stimulation of GH secretion.

Intrathecal administration of substance P in the rat: the effect on bladder and urethral sphincteric activity

At the lumbosacral spinal cord level in the rat, substance P-positive neurons are present in dense concentration in the dorsal horn and the sacral parasympathetic nucleus. We undertook the present study to investigate the effect of intrathecal substance P (10 micrograms at the L6-S1 level) on urinary bladder and urethral sphincteric activity and to compare these effects with those of intravenous and intra-arterial administration. Three different bladder pressure responses were triggered by intrathecal substance P: (A) an immediate, strong bladder contraction (n = 5); (B) augmentation of the micturition reflex, as indicated by strong detrusor contractions in response to intravesical saline perfusion (n = 4); and (C) a slow, gradual increase to a high, steady peak (n = 8). The sphincteric electromyographic (EMG) activity was consistently increased. When substance P was given intravenously (n = 10) and intra-arterially (n = 3), the form, duration, and maximal amplitude of bladder contractions (owing to a direct smooth-muscle action) were comparable with those of Group A. The effects in intrathecal Groups B and C suggest that substance P provides a tonic influence on motor horn cells and on the preganglionic neurons in the sacral parasympathetic nucleus at the lumbosacral spinal cord level, where neuronal circuits controlling bladder and sphincteric activity are located.

Blood vessels and immunoreactive substance P-containing nerve fibers in rat skin treated topically with clobetasol propionate, a corticosteroid

After applying topically a cream (0.1 ml) containing corticosteroid (clobetasol propionate), on rat back skin, we examined the morphological alterations of blood vessels, substance P-containing nerve fibers, and cutaneous mast cells. After 3, 6, 10, 15, 30, and 60 min and 4 h, the skin treated was cut out with a sharp knife after killing the animals. The skin pieces were processed into conventional histological sections cut vertically and examined by staining immunohistochemically with anti-substance P serum, by staining with toluidine blue for mast cell granules, and by estimating morphometrically the average areas of vascular cavity and the number of substance P fibers in the dermis. In the dermis and subcutaneous tissue of untreated skin, we found many immunoreactive SP-containing nerve fibers and mast cells in close association. Three to ten min after the treatment, the average area of the vascular cavities steadily increased, and SP-positive fibers became less frequent in the dermis. In concomitant with those events, cutaneous mast cells discharged their granules. Thereafter, the average area of vascular cavities gradually decreased to a minimum at 4 h after the treatment. In contrast, both SP-containing fibers and mast cells reestablished their initial states after the same duration.

Segmental distribution and peptide content of primary afferent neurons innervating the urogenital organs and colon of male rats

Many visceral afferent neurons contain peptides, which have been proposed as histochemical markers for nerve pathways of particular targets or as transmitter candidates. The former possibility was investigated in the present study. Primary afferent neurons which project to the urinary bladder, distal colon or penis of rats, and the colon of cats were labelled with retrogradely transported fluorescent dyes (Fast Blue, True Blue, or Fluoro Gold). One to six weeks after dye injection into the organs, lumbosacral dorsal root ganglia were removed, treated with colchicine, and processed for immunohistochemical identification of five peptides. Dye-labelled neurons were distributed in an organ-specific manner in the lower lumbosacral ganglia, where colon afferent neurons were almost exclusively found in S1 ganglia, penis neurons primarily in L6, and bladder neurons at both levels. Substance P- (SP), calcitonin gene-related peptide-(CGRP), vasoactive intestinal peptide- (VIP), enkephalin- (ENK), and somatostatin- (SOM) immunoreactivity (IR) were detected in neurons in all lumbosacral ganglia but only some of these peptides were present in a large percentage of labelled neurons. The numbers of peptide-containing neurons innervating each organ were CGRP greater than SP greater than VIP greater than ENK greater than SOM; however some differences were observed in the relative proportions of these neuronal populations between upper lumbar and lower lumbosacral ganglia and between different organs. The major difference seen at the upper lumbar level was amongst the SP-IR neurons, which were common (25-30%) amongst bladder and colon afferent neurons but absent in penis neurons.(ABSTRACT TRUNCATED AT 250 WORDS)

Screening of adrenal medullary neuropeptides for putative neurotrophic effects

Chromaffin granules, the secretory organelles of the neuron-like adrenal medullary chromaffin cells, have previously been shown to store and liberate neurotrophic activities that support in vitro survival of several neuron populations including those innervating the adrenal medulla. Molecules resembling fibroblast growth factor and ciliary neurotrophic factor have been identified among these activities. Since chromaffin granules store a variety of neuropeptides and many neuropeptides can have pleiotropic effects on neuronal growth and maintenance we have tested 24 different neuropeptides for their capacities to promote survival of embryonic chick ciliary, dorsal root and sympathetic ganglionic neurons. Peptides tested included several derivatives of proenkephalin (Leu- and met-enkephalin, fragments BAM 22, B, F and E), somatostatin, substance P, neuropeptide Y, neurotensin, VIP, bombesin, secretin, pancreastatin, dynorphin B, dynorphin 1-13, beta-endorphin, alpha-, beta-, and gamma-MSH. Control cultures received saturating concentrations of ciliary neurotrophic or nerve growth factor (CNTF; NGF), or no trophic supplements. At 1 x 10(-5) M leu- and met-enkephalin as well as somatostatin supported sympathetic neurons to the same extent as NGF. At the same concentrations, leu-enkephalin, the proenkephalin fragments BAM 22 and E, and somatostatin maintained about half of the dorsal root ganglionic neurons supported by NGF, but were not effective on ciliary neurons. VIP promoted the survival of approximately 50% of the ciliary and embryonic day 10 dorsal root ganglionic neurons as compared to saturating amounts of CNTF, but required the presence of non-neuronal cells in the cultures to be effective. Neurotensin (1 x 10(-5) M had a small effect on ciliary neurons.(ABSTRACT TRUNCATED AT 250 WORDS)

Interferon-gamma-like immunoreactivity in sensory neurons may influence the replication of Sendai and mumps viruses

Rat dorsal root ganglia in tissue culture, which contain an interferon-gamma (IFN-gamma)-like immunoreactive subpopulation of neurons, were infected with paramyxoviruses. Sendai virus caused a substantial neuronal lysis, while the RW strain of mumps virus caused a much less pronounced nerve cell loss. Early during infection, the subpopulation of IFN-gamma-like immunoreactive neurons was less susceptible to mumps virus. Virus antigen was rapidly lost from surviving IFN-gamma-like positive neurons infected with Sendai virus, while this remarkable self-curing effect occurred in both nerve cell populations at later time points after mumps virus infection. By quantitative enzyme-linked immunosorbent assay (ELISA) technique, increased levels of "neuronal IFN-gamma" were recorded at 10 hr and 30 hr after infection with Sendai and mumps virus, respectively. This study indicates a role for the neuronal IFN-gamma-like molecule in determining the outcome of a viral infection in sensory ganglia.

Effect of spinal microinjections of an antagonist to substance P or somatostatin on the exercise pressor reflex

The purpose of this study was to determine the heart rate and arterial blood pressure changes to isometric skeletal muscle contraction and muscle stretch before and after microinjecting an antagonist to substance P (SP) or somatostatin (SOM) into the L-7 dorsal horn region of the spinal cord of anesthetized cats. Anesthesia was induced by administering an anesthetic gas mixture and was subsequently maintained with alpha-chloralose. Triceps surae contraction was induced by electrically stimulating the L-7 ventral root. Three muscle manipulations (all 1 minute in duration) were performed: 1) continuous tetanic contraction, 2) intermittent tetanic contractions (1 second of contraction, 1 second of relaxation), and 3) passive muscle stretch. Saline microinjections had no effect on the cardiovascular responses to these muscle manipulations. However, both peptide antagonists blunted the pressor response to a continuous tetanic contraction as mean arterial pressure increased 47 +/- 4 and 44 +/- 4 mm Hg before and 28 +/- 3 and 28 +/- 4 mm Hg after microinjecting the SP or SOM antagonist, respectively. In contrast, neither antagonist influenced the increase in mean arterial pressure produced by passive stretch; values were 43 +/- 6 versus 41 +/- 6 mm Hg (SP antagonist) and 39 +/- 7 versus 42 +/- 7 mm Hg (SOM antagonist) before and after injections, respectively. Microinjecting the SOM antagonist attenuated the pressor response to intermittent tetanic contractions (44 +/- 4 mm Hg before SOM antagonist versus 26 +/- 4 mm Hg after SOM antagonist), whereas the SP antagonist had no effect (35 +/- 3 mm Hg before SP antagonist versus 32 +/- 4 mm Hg after SP antagonist).(ABSTRACT TRUNCATED AT 250 WORDS)

Ultrastructural localization of somatostatin- and substance P-immunoreactive nerve fibers in the feline liver

The distribution and the possible source of somatostatin- and substance P-immunoreactive nerve fibers were studied in the liver of the cat by immunocytochemical techniques. Abundant substance P-immunoreactive and a moderate number of somatostatin-immunoreactive nerve fibers were found running around the blood vessels in the perilobular connective tissue. Some somatostatin-immunoreactive nerve cell bodies were also observed in the liver. A moderate number of somatostatin-immunoreactive nerve profiles were found inside the hepatic lobules along the sinusoid endothelial cells and the hepatocytes. The interspace between the axon and hepatocyte and endothelial cells membranes was about 20 nm. Cutting the extrinsic hepatic nerves resulted in marked reduction of substance P-immunoreactive nerves but only a slight reduction of somatostatin-immunoreactive nerves in the liver. These findings provide a morphological basis for the possibility that somatostatin and substance P may act as transmitters or neuromodulators on the neighboring smooth muscle cells of vessels and may regulate the function of the hepatocytes. It is also possible that some of these fibers serve sensory function along the blood vessels.

Localization of basic fibroblast growth factor in a subpopulation of rat sensory neurons

The distribution of basic fibroblast growth factor (bFGF)-immunoreactivity (IR) was studied in rat sensory and autonomic ganglia. In postnatal and adult sympathetic superior cervical ganglia and in adult parasympathetic otic ganglia no bFGF-staining was found. Postnatal and adult neural crest- and placode-derived sensory ganglia displayed intensive bFGF-IR in a neuronal subpopulation. This subpopulation was characterized by use of consecutive sections of adult dorsal root ganglia stained with antibodies against substance P, somatostatin, bombesin, and bFGF. Basic FGF was colocalized with the somatostatin/bombesin subpopulation but not with substance P.

Non-endocrine applications of somatostatin and octreotide acetate: facts and flights of fancy

Somatostatin, originally detected by Krulich and ultimately isolated by Brazeau, was initially described as a growth hormone release-inhibiting factor. Subsequent investigation into the use of native somatostatin and the development of long-acting somatostatin analogues, especially octreotide acetate, have fostered increasing uses of these compounds. Though the clinical and investigational uses of somatostatin and its analogues are varied, one central theme remains constant: the ability of these agents to suppress circulating peptide levels. This article, a review of the current non-endocrine applications of somatostatin and its analogues, covers a wide range of potential applications for somatostatin-like compounds. These include use in cirrhosis and variceal bleeding, peptic ulcer disease, pancreatic fistulas, acute and chronic pancreatitis, dumping syndrome, cancer therapy, small bowel fistulas, psoriasis, pain control, and autonomic hypotension. Somatostatin may also play a role in the development and potential treatment of neurologic disease and may have profound found influence on behavior.

Effect of adrenalectomy and dexamethasone on neuropeptide content of dorsal root ganglia in the rat

Neuropeptides, including substance P (SP), calcitonin gene-related peptide (CGRP) and somatostatin (SS) in dorsal root ganglia (DRG) may play a role in neurogenic inflammation and pain transmission. Adrenal corticosteroids regulate neuropeptide synthesis in some areas of the CNS and may modulate neurogenic inflammation and sensory perception. We have investigated the effects of adrenalectomy and dexamethasone (0.2 mg/kg/day) treatment on neuropeptide content of rat cervical DRG using specific and sensitive radioimmunoassays. In control animals, a differential distribution of neuropeptide was found; SP and CGRP content increased from C4 to C7 in contrast to SS content, which decreased from C4 to C7. Ten days following adrenalectomy, the mean SS content of cervical DRG decreased significantly to 79.6 +/- 4.5% of sham-operated controls. In contrast, SP and CGRP content increased significantly 10 days after adrenalectomy to 134.6 +/- 6.9% and 132.0 +/- 11.6% of sham-operated controls, respectively. The effects of adrenalectomy on CGRP and SS were reversed by administration of dexamethasone. These results suggest that glucocorticoids affect the neuropeptide content of DRG in the adult rat.

Localization of beta pre-protachykinin mRNA in nodose ganglion

The neurons which synthesize tachykinins in the capsaicin-sensitive afferent nerves of the respiratory tract are largely localized to the nodose ganglia. Using a radiolabelled antisense cRNA probe constructed from cDNA for the major precursor of substance P and neurokinin A (beta-preprotachykinin: beta-PPT), we have localized specific mRNA for this peptide in neurons of the nodose ganglion of rat using in situ hybridization. 26% of neurons gave a positive hybridization signal, which was in agreement with the same proportion of cell bodies showing substance P-like immunoreactivity. The specificity of the hybridization was confirmed by the absence of labelling using RNase pre-treatment and a sense probe having the same sequence as beta-PPT mRNA. This approach may now allow the investigation of factors which regulate synthesis of tachykinins at a gene transcriptional level.

Relationships between capsaicin sensitivity of mammalian sensory neurons, cell size and type of voltage gated Ca-currents

(1) The relationships between capsaicin sensitivity, cell size and the expression of voltage-dependent high-threshold (L- and N-type) and low-threshold (T-type) Ca-currents were investigated in cultured adult rat dorsal root ganglion neurons using the whole-cell patch-clamp technique. (2) The capsaicin (10 microM) evoked inward current was used to identify the capsaicin-sensitive population. To identify the voltage-dependent Ca-currents, the activation threshold and the inactivation kinetic were used. (3) In cultured dorsal root ganglion cells the capsaicin sensitivity is not restricted to the small cell population. About 28% of cells with large cross sectional areas (greater than or equal to 1001 microns 2) responded with about the same amplitude per micron2 cross sectional area as small cells. (4) The amplitude of the capsaicin evoked inward current depended on the length of time the cells were maintained in culture. (5) All cells exhibited the high-threshold Ca-currents. About 45% of the capsaicin-insensitive cells also had low-threshold Ca-currents. None of the capsaicin-sensitive cells had the low-threshold type. (6) Most of the cells which expressed the low-threshold type were in the upper size range.

Herpes simplex virus infection in populations of mouse dorsal root ganglion neurons: effects of inoculation route and virus strain

To investigate whether herpes simplex virus type-2 (HSV-2) infection of sensory ganglion neurons is restricted to a particular neuronal class, we unilaterally inoculated either the footpad, leg muscle or sciatic nerve of mice with strains of HSV-2 that differ in virulence and examined the soma sizes of lumbar dorsal root ganglion (DRG) neurons containing viral antigen near the peak of acute infection. Each inoculation route appeared relatively selective for a different portion of the neuronal size spectrum. Footpad inoculation primarily infected the smaller population of DRG neurons, by comparison, muscle inoculation tended to spare the smallest neurons while infecting medium and larger cells. Sciatic nerve inoculation infected the entire spectrum of DRG neurons. These results indicate that HSV-2 infection is not restricted to a specific subclass of sensory neurons. With any particular inoculation route, the least virulent strain infected fewer neurons than did those of greater virulence.

Localization of substance P-like immunoreactivity in guinea pig vestibular endorgans and the vestibular ganglion

The immunocytochemical distribution of substance P (SP) in guinea pig vestibular endorgans and the vestibular ganglion was investigated. Two kinds of SP-immunoreactive fibers were distinguished. Most were thick, and found around or beneath sensory hair cells. These SP-immunoreactive fibers were distributed predominantly on the slope of the crista and the peripheral region of the macula. By electron microscopy, we confirmed this type of SP-like immunoreactivity to be restricted within primary afferent neurons. Some vestibular ganglion cells also showed SP-like immunoreactivity, suggesting that SP is present in some primary afferent neurons, and is involved in afferent neurotransmission. The characteristic distribution of SP may indicate functional differences within each endorgan. The other group of immunoreactive nerve fibers, varicous thin fibers, could be found in the stroma of vestibular endorgans, nerve trunk, vestibular ganglion, and along blood vessels of the vestibular ganglion. These fibers may have a different origin, and have an influence on blood flow and certain other functions.

An electron microscopic description of glutamate-like immunoreactive axon terminals in the rat principal sensory and spinal trigeminal nuclei

The spinal and principal sensory trigeminal nuclei relay noxious and nonnoxious stimuli from the orofacial region to the thalamus. Physiological studies have implicated glutamate as an important neurotransmitter in this region. Despite its importance as a potential transmitter, few studies have examined the anatomical distribution of glutamate within these nuclei. We therefore chose to use a monoclonal antibody raised against glutamate conjugated to a carrier protein to identify and describe glutamate-like immunoreactive processes at the electron microscopic level. Glutamate-like immunoreactive axon terminals were identified throughout the spinal trigeminal and principal sensory trigeminal nucleus. In subnucleus caudalis glutamate-like immunoreactive terminals occurred frequently in all laminae and were morphologically heterogeneous. In lamina I, glutamate-like immunoreactive terminals were primarily ovoid, contained spherical synaptic vesicles, and participated in synaptic complexes with both dendritic and axonal profiles. In laminae II and III many glutamate-like immunoreactive axon terminals were identified as the central element in synaptic glomeruli. Within discrete patches of lamina II, large numbers of glutamate-like immunoreactive terminals contained dense core vesicles. The majority of glutamate-like immunoreactive terminals in subnucleus interpolaris, subnucleus oralis, and principal sensory trigeminal nucleus were similar in morphology and synaptic interaction to the glutamate-like immunoreactive terminals found in subnucleus caudalis. Glutamate-like immunoreactive terminals that were the central presynaptic element in glomerular complexes were seen in all subnuclei. In sections from subnucleus interpolaris and subnucleus oralis central glutamate-like immunoreactive terminations within glomerular complexes had much smoother profiles, and in subnucleus interpolaris participated primarily in axodendritic synaptic junctions. In the principal sensory trigeminal nucleus central glutamate-like immunoreactive terminations were highly scalloped and participated in numerous axoaxonic synaptic junctions. The above observations are consistent with the hypothesis that glutamate-like immunoreactivity is present in some primary afferent terminations and functions as an important excitatory transmitter involved in the relay of sensory information to the spinal trigeminal and principal sensory trigeminal nucleus.

An anatomical study of the origin of sympathetic and sensory innervation of the elbow and knee joint in the monkey

The origin of sympathetic and sensory innervation of the elbow and knee joint was studied by the intra-axonal transport method. After injection of WGA-HRP into the elbow and knee joint unilaterally in adult monkeys (macaca fascicularis), labelled cells were observed ipsilaterally in both the sympathetic and dorsal root ganglia. Following injection in the elbow joint the neurons were concentrated in the stellate and third to fourth thoracic (T3-T4) sympathetic ganglia, and in the fourth cervical to second thoracic spinal sensory ganglia. The knee joint injection resulted in labelling of sympathetic and spinal sensory ganglia, preferentially at the lumbo-sacral junction--the third lumbar to third sacral (L3-S3) ganglia. The functional implications are discussed in relation to pain mechanisms of joints and to an earlier hypothesis that the nervous system might be involved in the pathogenesis of chronic joint inflammation.

Streptozotocin-induced diabetes in mice reduces the nociceptive threshold, as recognized after application of noxious mechanical stimuli but not of thermal stimuli

We report herein that streptozotocin (STZ)-induced diabetes selectively alters the nociceptive threshold with respect to noxious mechanical stimuli. Mice were rendered diabetic by an injection of STZ (200 mg/kg, IV). In the tail-pinch test, the latency of the biting response to forceps was significantly decreased in animals with diabetes of 2 weeks and 8 weeks duration as compared to that in age-matched controls. However, the nociceptive threshold, as determined by the tail-flick test, was not significantly altered. The level of substance P in the spinal cord was significantly increased in mice that has been diabetic for 2 weeks, while, there was a significant decrease, as compared to control levels, in level of substance P in mice diabetic for 8 weeks. However, the level of somatostatin was not significantly altered in mice diabetic for either 2 weeks or 8 weeks. These data suggest that STZ-induced diabetes selectively alters a neuronal system that involves substance P but not somatostatin in the spinal cord.

Distribution of five peptides, three general neuroendocrine markers, and two synaptic-vesicle-associated proteins in the spinal cord and dorsal root ganglia of the adult and newborn dog: an immunocytochemical study

This study describes the immunocytochemical distribution of five neuropeptides (calcitonin gene-related peptide [CGRP], enkephalin, galanin, somatostatin, and substance P), three neuronal markers (neurofilament triplet proteins, neuron-specific enolase [NSE], and protein gene product 9.5), and two synaptic-vesicle-associated proteins (synapsin I and synaptophysin) in the spinal cord and dorsal root ganglia of adult and newborn dogs. CGRP and substance P were the only peptides detectable at birth in the spinal cord; they were present within a small number of immunoreactive fibers concentrated in laminae I-II. CGRP immunoreactivity was also observed in motoneurons and in dorsal root ganglion cells. In adult animals, all peptides under study were localized to varicose fibers forming rich plexuses within laminae I-III and, to a lesser extent, lamina X and the intermediolateral cell columns. Some dorsal root ganglion neurons were CGRP- and/or substance P-immunoreactive. The other antigens were present in the spinal cord and dorsal root ganglia of both adult and newborn animals, with the exception of NSE, which, at birth, was not detectable in spinal cord neurons. Moreover, synapsin I/synaptophysin immunoreactivity, at birth, was restricted to laminae I-II, while in adult dogs, immunostaining was observed in terminal-like elements throughout the spinal neuropil. These results suggest that in the dog spinal cord and dorsal root ganglia, peptide-containing pathways complete their development during postnatal life, together with the full expression of NSE and synapsin I/synaptophysin immunoreactivities. In adulthood, peptide distribution is similar to that described in other mammals, although a relative absence of immunoreactive cell bodies was observed in the spinal cord.

Descending projections to the rat sacrocaudal spinal cord

Descending supraspinal and propriospinal neurons projecting to the female rat sacrocaudal spinal cord, the portion of the spinal cord that innervates the tail, were identified following injection of Fluoro-Gold into the S1-Ca2 spinal cord segments. This study attempted to determine anatomical substrates for propriospinal and supraspinal control of the tail. Propriospinal neurons were identified throughout laminae V-VIII and X at all levels of the spinal cord. The greatest density of labeling was in the lumbar enlargement, followed by the cervical enlargement, with least in the thoracic spinal cord. Within a given cord level, labeling was greatest within the intermediate zone. In addition, other prominent spinal cord collections included neurons in 1) lamina V of the lumbar enlargement, 2) dorsal lamina X of the cervical enlargement, and 3) the lateral spinal nucleus within the cervical enlargement. Supraspinal cells were identified within raphe nuclei, reticular formation nuclei, dorsal column nuclei, vestibular nuclei, noradrenergic groups, the red nucleus, the periaqueductal gray, the hypothalamus, and the motor cortex. These data indicate that there are significant descending projections to the sacrocaudal spinal cord, with distributions similar to those of other cord levels. Functionally, important supraspinal and propriospinal influences on tail, pelvic viscera and limbs, such as with locomotion, balance, defense, micturition, defecation, and sexual functions, may be mediated by these connections.

Substance P-containing sensory neurons in the rat dorsal root ganglia innervate the adrenal medulla

The adrenal medulla is innervated by both cholinergic and substance P (SP)-containing fibres via the splanchnic nerve. SP has been shown to modulate catecholamine (CA) secretion in isolated chromaffin cells and in the perfused rat adrenal gland, however, the origin of SP-containing fibres is not known. In the present study, we have combined the techniques of SP immunohistochemistry and retrograde tracing with Fast blue injected into the left adrenal medulla of the rat in order to study whether SP-containing sensory neurons in the dorsal root ganglia innervate the adrenal medulla. The results showed that there were on average 281 +/- 31 SP-like immunoreactive cells in each left dorsal root ganglion, T3-T13 (range, 234 +/- 19 in T4 to 372 +/- 43 in T13, n = 8). The average total number of Fast blue-labelled cells (T3-T13) in 8 experiments was 172 +/- 26, distributed normally about a peak at T8 (33.8 +/- 6.3 cells) and T9 (33.3 +/- 6.8 cells) with the least at T3 (1.5 +/- 0.8) and T13 (5.2 +/- 2.0). No Fast blue-labelled cells were found in the right DRG. In the left DRG, the average number of cells exhibiting both SP and Fast blue labelled cells were distributed from T7 to T9. These results demonstrate that SP-containing sensory neurons in the dorsal root ganglia provide an ipsilateral innervation of the adrenal medulla in rats.

Somatostatin modulates vascular sympathetic neurotransmission in the rabbit ear artery

Somatostatin-like immunoreactivity was localised immunohistochemically in perivascular nerves in the rabbit central ear artery. Whilst somatostatin had no direct action on this vessel, it significantly inhibited noradrenaline-induced, but not alpha, beta-methylene ATP-induced, vasoconstriction. Somatostatin also inhibited contractions elicited by electrical field stimulation showing greater effect at low (16 Hz) compared with high (64 Hz) frequencies, and inhibited the release of tritiated noradrenaline in a concentration-dependent manner. These results confirm that somatostatin is a neuroregulatory peptide, and suggest that it is modulating vascular sympathetic cotransmission of the rabbit central ear artery by acting both prejunctionally to inhibit transmitter release, and postjunctionally to reduce the action of noradrenaline.

Localization of NADPH-diaphorase-containing neurons in sensory ganglia of the rat

The presence of reduced nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase activity was studied histochemically in the sensory ganglia of the rat. Supraspinally, the trigeminal ganglion possessed only a few cells positively stained for NADPH-diaphorase, while a large number of positive neurons was found in the nodose ganglion. In the dorsal root ganglia, the distribution of positive cells showed a peculiar pattern in relation to spinal levels. Very minor populations (less than 2% of the total ganglionic cells) exhibited positive reaction in ganglia at levels ranging from the first cervical (C1) to fourth thoracic (T4) and from the second lumber (L2) through the entire sacral levels. In the middle to lower thoracic levels (from T5 to L1), however, abundant diaphorase-positive cells were observed. From these positive neurons it was possible to trace intensely stained nerve fibers. In the lower thoracic level, for example, dense positive fibers were seen in the ramus communicans. Retrograde tracing studies revealed that diaphorase-containing neurons in the lower thoracic level project at least partly to the gastric wall and the celiac ganglion. These results indicate that the diaphorase-positive ganglionic neurons in the thoracicolumbar levels may carry autonomic visceral afferent information. Double staining with NADPH-diaphorase histochemistry and peptide immunohistochemistry revealed that NADPH-diaphorase colocalizes with calcitonin gene-related peptide and substance P in many of these visceral afferent neurons.

Ultrastructural localization of substance P, met-enkephalin, and somatostatin immunoreactivity in lamina X of the primate spinal cord

The ultrastructural localization of substance P (SP), met-enkephalin (MENK), and somatostatin (SS) in the lamina X area surrounding the central canal of the macaque monkey was examined by the indirect peroxidase-antiperoxidase method. The most common synaptic terminals in lamina X were simple terminals (S) with small rounded or pleomorphic clear vesicles; one to two dense-core vesicles were occasionally also present. These were found on soma, dendrites, and dendritic spines, in all regions of lamina X. A second class of terminal with round or oval clear vesicles was glomerular (G) in shape, with scalloped edges, and contained many mitochondria. These large terminals had several synaptic contacts onto dendrites, spines, and small terminals and were found mainly in the lateral region. The third class (L) contained small clear vesicles and several vesicles with large, dense cores (100-125 nm), and also contacted dendrites, mainly lateral to the canal. The fourth class of terminal (D) contained small clear vesicles and several vesicles with small, dense cores (75-100 nm); these contacted dendrites and somata in all areas. Very few terminals with flat vesicles were identified. There was an unequal distribution of immunoreactivity among the several terminal classes identified in lamina X. Most SP terminals were S terminals, but SP L terminals were also common; few were D terminals. MENK terminals were usually either S terminals or D terminals; L terminals were rarely MENK positive. SS terminals were commonly D terminals or S terminals; L terminals were also rarely SS positive. Only SP terminals were identified as G terminals. Synaptic targets of SP, MENK, and SS terminals were most commonly dendrites. In addition to unlabelled neurons, peptidergic neurons and their processes were also synaptic targets of terminals containing the same peptide. The distributions of these peptides in primate lamina X differ from that of the same peptides in primate superficial dorsal horn. These differences are important, in consideration of some of the parallels that may be drawn between the lamina X area and the superficial dorsal horn; both areas have high concentrations of the same peptides, receive nociceptive primary afferents, and contain spinothalamic and other projection neurons. Nevertheless, comparison of the distribution of immunoreactivity among terminal classes indicates that neurochemical organization at the ultrastructural level is quite distinct in each of the two areas. This may also reflect other roles of the lamina X area, including its involvement in visceral functions, although it would be expected that this element might be less prominent at the cervical levels we investigated.

Marked improvement of a substance P radioimmunoassay by reduction of 125I-labelled [Tyr8]-substance P prepared by the chloramine-T method with mercaptoethanol and subsequent purification by reversed-phase liquid chromatography

[Tyr8]-substance P was radiolabelled with 125I by the application of the chloramine-T method. Due to the high oxidative potential of the 125I-chloramine-T system the purified reaction product was converted into a derivative, which presumably had been oxidized to the corresponding sulphoxide at Met11. This conversion was shown by reversed-phase high-performance liquid chromatography after consecutive reduction-oxidation experiments of the freshly prepared radiopeptide. The oxidized derivative exhibited only negligible binding to substance P receptors isolated from rat brain homogenates. However, in contrast, it showed marked cross-reaction to the antibody raised in rabbits against synthetic SP(1-11). The variance in the quantification of identical samples was marked, and the measurement of concentrations in the lower pg/ml range was not sensitive enough to determine levels of substance P-like immunoreactivity in human cerebrospinal fluid. Assay sensitivity could be substantially improved and variance significantly decreased by the use of a radiopeptide, which had been labelled by the chloramine-T method and which had been subsequently reduced with mercaptoethanol and purified by liquid chromatography.

Ultrastructure and distribution of somatostatin-like immunoreactive neurons and nerve fibres in the coeliac ganglion of cats

Somatostatin-like immunoreactivity was localized in nerve cell bodies and nerve terminals in the cat coeliac ganglion. Two types of somatostatin-immunoreactive cell bodies were revealed, the first being large (diameter 35 microns), numerous and weakly labelled, whereas the second was considerably smaller (diameter 10.4 microns), sparsely distributed and heavily stained. The immunoreactive nerve terminals were in synaptic contact with many immunonegative large neurons and dendrites. However, in a few cases, somatostatin-immunoreactive nerve terminals could also be observed on the surface of lightly stained neurons. Transection of vagal or mesenteric nerves failed to affect the distribution or density of somatostatin-like immunoreactive nerve terminals. These results demonstrate the existence of a synaptic input to the principal neurons of the coeliac ganglion of the cat by somatostatin-containing nerve terminals and suggest that this peptide may act as a neuromodulator or neurotransmitter. It is proposed that somatostatin-positive neurons provide intrinsic projections to other somatostatin-positive and to somatostatin-negative neurons throughout the coeliac ganglion, thereby creating a complex interneuronal system.

Detection and characterization of a sensory microganglion associated with the spinal accessory nerve: a scanning laser confocal microscopic study of the neurons and their processes

The spinal accessory nerve has been generally thought to be a cranial nerve with purely motor function, innervating the trapezius and sternocleidomastoid muscles. The present study identified clusters of sensory neurons consistently associated with this cranial nerve in adult rats. Either a single microganglion or several dispersed microganglia were found that adhered to the spinal root of the nerve, to small vessels, or were free within the subarachnoid space. The neurons of the ganglion had axons that joined the spinal root of the nerve proximal to its exit from the skull. Additional branches appeared to have an intracranial distribution within the arachnoid of the brainstem and along its vessels. Several findings suggest that the function of the ganglion is sensory and not autonomic. First, the architectural features of neurons within the ganglion (including their size, pseudounipolar morphology, and the lack of synaptic contacts) are similar to those of neurons in other sensory ganglia. Second, substance P and calcitonin gene-related peptide coexist within neurons of the microganglion, whereas markers for the major transmitters found in autonomic ganglia in rats are absent. Third, the expression of peptides in neurons of the ganglion was sensitive to neonatal capsaicin treatment. Finally, neurons within the ganglion were filled with a retrogradely transported dye after injection of the dye into the cervical spinal cord. Although the function of the ganglion is not known, its features are consistent with a role in nociception from the muscles of the spinal accessory complex, and it may be involved in headaches that have an occipital distribution.

Interferon-gamma-like immunoreactivity in developing rat spinal ganglia neurons in vivo and in vitro

Interferon-gamma-like immunoreactivity was observed in a subpopulation of 16-day-old embryonic rat spinal ganglion neurons using two monoclonal antibodies directed against different epitopes of recombinant interferon-gamma. During ontogenesis both in vivo and in vitro, it was found that the strong immunoreactivity was confined to small neurons when neurons become morphologically distinct on the basis of size. In vivo, the interferon-gamma-immunoreactive neurons started to express major histocompatibility complex class I antigens after the first postnatal week, while in vitro no such antigen could be detected. A quantitative Elisa method was developed to determine the levels of major histocompatibility complex class I and interferon-gamma in vitro, whereby increased amounts of major histocompatibility complex class I antigen was detected after exposing the cultures to recombinant interferon-gamma and Sendai virus. Sendai virus also caused a small increase in interferon-gamma with a peak about 12 hours after infection. The in vitro system will be used to study further the role of the putative neuronal interferon-gamma-like molecule in the regulation of cell growth, for induction of major histocompatibility complex antigens and in virus infection of sensory neurons.

Regulatory peptide and serotonin content and brush-border enzyme activity in the rat gastrointestinal tract following neonatal treatment with capsaicin; lack of effect on epithelial markers

The possible trophic influence of the capsaicin-sensitive extrinsic innervation of the gastrointestinal mucosa was investigated. Rats were treated neonatally with capsaicin. The gastrointestinal content of serotonin and glucagon-like immunoreactivity were used as a measure of the effect on the endocrine gut mucosa and gastrointestinal aminopeptidase and alkaline phosphatase activities were used as a measure of the effect on the gut brush-border. The gastrointestinal content of the neuropeptides substance P, VIP and CGRP were used to monitor effects on the innervation of the gut. The depletion of substance P-immunoreactivity(-IR) and calcitonin gene-related peptide(CGRP)-IR in extracts of urinary bladder and lung from the capsaicin-treated rats is evidence of the efficacy of capsaicin treatment in affecting a loss of C-fibre sensory nerves. The significant depletion of CGRP-IR measured in the stomach and duodenum of capsaicin-treated rats indicated the loss of the C-fibre sensory innervation to the gastrointestinal tract. The gastrointestinal content of VIP and substance P, which are predominantly within intrinsic gut neurones, were unaffected by capsaicin treatment. In all regions of the gastrointestinal tract of capsaicin-treated rats, the serotonin and glucagon-IR levels were not significantly different from those in controls. Similarly the levels of activity of the brush-border enzymes were not significantly effected by capsaicin treatment. This suggest the absence of any major trophic influence of capsaicin-sensitive sensory nerves on the gut endocrine mucosa and the brush border.

Immunocytochemical evidence for the presence of somatostatin-like immunoreactive nerves in human dental pulp

Specific antiserum to somatostatin was used for the immunocytochemical detection of this neuropeptide in human dental pulp. Immunoreactive axon varicosities were observed in the radicular as well as coronal pulp. Fibers displaying somatostatin-like immunoreactivity were detectable within radicular nerve trunks and were found to be associated mainly with blood vessels. Nevertheless, positive fibers with no apparent relation to blood vessels were also observed. No pulp cell was found to be immunoreactive. Previous physiological studies demonstrated that somatostatin may function as a regulatory peptide in feline dental pulp via a pre-synaptic inhibition of substance P release from sensory nerve terminals. It is tempting to speculate that such a mechanism may also be effective in human teeth and may be of value in the regulation of pulpal blood flow and in situations when sensory nerve fibers are activated, e.g., during pulpal inflammation.

Substance P- and calcitonin gene-related peptide immunoreactivity in primary afferent neurons of the cat's knee joint

The distribution of substance P and calcitonin gene-related peptide was determined in primary afferent neurons of the medial and posterior articular nerve of the cat's knee joint. Perikarya of articular afferents were visualized by retrograde labelling with the fluorescent dye Fast Blue which was applied at the transected end of the peripheral nerves. Substance P was found in about 17% of labelled medial articular afferents and in about 16% of labelled posterior articular afferents, respectively, whereas calcitonin gene-related peptide was present in about 35 and 32% of the medial and posterior articular nerve cells, respectively. Taking into account that these neuropeptides are known to be co-localized, probably not more than one-third of the joint afferents contain substance P and/or calcitonin gene-related peptide. Quantification of cell diameters revealed that substance P was found only in small- or intermediate-sized perikarya (less than 50 microns) indicating that this peptide is predominantly found in unmyelinated neurons. Calcitonin gene-related peptide was present mainly in small- and intermediate- but also in some large-sized neurons (greater than 50 microns) providing evidence that this peptide is found in unmyelinated and to a lesser extent in myelinated neurons. This is consistent with previous studies that show that substance P and calcitonin gene-related peptide are present primarily in unmyelinated and thinly myelinated primary afferents. When the portion of substance P-positive neurons of the medial articular nerve is compared to the number of articular afferents displaying a nociceptive function as determined in earlier electrophysiological studies, it can be calculated that at most 30% of the nociceptive-specific articular afferents contain this neuropeptide.(ABSTRACT TRUNCATED AT 250 WORDS)

Cell size and cell type analysis of calcitonin gene-related peptide-containing cutaneous and splanchnic sensory neurons in the rat

Cell size, cell type and calcitonin gene-related peptide (CGRP)-like immunoreactivity were compared between cutaneous and splanchnic sensory neurons by means of a combination of fluorescent tracer and immunohistochemistry. Nineteen percent of cutaneous sensory neurons and 88% of splanchnic sensory neurons were shown to contain CGRP. The former cells were larger than the latter ones, which was also confirmed by the finding that about a half of the former cells contained 200 kDa subunit of neurofilament protein, while only 8% of the latter ones were positively stained. These findings suggest that most of the visceral CGRP-IR sensory neurons are small type B.

Nicotinic acetylcholine receptor mRNA in dorsal root ganglion neurons

Nicotinic acetylcholine receptor (AChR) genes are expressed in subpopulations of chick dorsal root ganglion (DRG) neurons. In 18-day embryonic ganglia, 19% of the neurons have material homologous to neuronal AChR alpha 3 gene mRNA, and 8% have material homologous to alpha 4 mRNA as seen with in situ hybridization. RNAase protection experiments confirm that DRG RNA contains alpha 3 and alpha 4 transcripts, and Northern blot analysis establishes the size of the transcripts as being 3.5 and 3.3 kb, respectively. The proportion of DRG neurons containing alpha 3 mRNA does not decline up through 1 year post-hatch, indicating that alpha 3 gene expression is not a developmentally transient event in the ganglion. An antiAChR monoclonal antibody detects cross-reacting material in 16% of the DRG neurons from 18-day embryos, indicating that AChR mRNA is translated into protein. Electrophysiological measurements confirm the presence of functional AChRs on DRG neurons freshly isolated from 18-day embryos: 24% of the neurons have substantial ACh sensitivities, whereas another 23% have small but detectable responses. Staining dorsal root ganglion sections with an anticholine acetyltransferase antiserum reveals cross-reactive material localized in axons in the ganglion; no evidence suggests the presence of cholinergic synaptic structures or AChR clusters on neuronal somata in the ganglion. It is possible that AChRs on DRG neurons participate in a diffuse form of transmission between the cholinergic fibers and a subpopulation of neuronal somata in the ganglion. Alternatively, AChRs on the somata may represent an ectopic distribution of receptors whose primary function is at the terminals of central or peripheral DRG processes.

Serotonin, but neither noradrenaline nor GABA, inhibits capsaicin-evoked release of immunoreactive somatostatin from slices of rat spinal cord

It has been suggested that somatostatin is involved in nociceptive transmission in the dorsal horn and that it is contained in small primary afferent neurons. In the present experiments, to elucidate neural systems inhibiting the release of somatostatin from the primary afferent terminals, we examined the effects of serotonin, noradrenaline and gamma-aminobutyric acid on the capsaicin-evoked, dorsal-rhizotomy-sensitive and tetrodotoxin-insensitive release of immunoreactive somatostatin, 98.7% of which was somatostatin itself, from the dorsal-half slices of lumbar and cervical enlargements of rat spinal cord. Serotonin (30-100 microM) suppressed the evoked release in a concentration-dependent manner, and the suppression was antagonized by methysergide (100 microM). The evoked release of immunoreactive somatostatin was not inhibited by noradrenaline (100 microM) or gamma-aminobutyric acid (100 microM). The present results suggest that the serotonergic systems exert an inhibitory effect on the release of somatostatin from the central terminals of primary sensory neurons.

Immunohistochemical studies on the spinal dorsal horn of the turtle Chrysemys d'orbigny

Immunohistochemical methods were used to characterize some of the systems of nerve fibers occurring in the spinal dorsal horns of the turtle Chrysemys d'orbigny. Substance P (SP), calcitonin gene-related peptide (CGRP) and leuenkephalin (Enk) immunoreactive fibers were found concentrated in the superficial horn region, termed here synaptic field Ia. From this zone the immunoreactive fibers project to deeper dorsal horn regions. Comparison with histological images obtained after HRP labeling of dorsal root axons indicates that SP-, CGRP- and Enk-immunoreactive fibers are small-diameter primary sensory fibers entering the cord via synaptic field Ia. It is posulated here that these three substances may coexist in the same fibers. Enk-positive fibers also occur randomly scattered in the lateral funiculi, showing a conspicuous increase in density at the perimedullary plexus level. Tyrosine hydroxylase (TH) immunoreactive fibers were found in the more compact dorsal horn neuropil (synaptic field II) and also forming bilateral conspicuous bundles in the lateral funiculi. TH-immunoreactive cell bodies were found in the epithelium lining the central canal. Taking into account data derived from Golgi impregnated material it is proposed that they represent epithelial cells undergoing neural differentiation.

Intrathecal and epidural somatostatin in rats: can antinociception, motor effects and neurotoxicity be separated?

In the present investigation, the antinociceptive, motor blocking and neurotoxic effects of intrathecal and epidural somatostatin (SST) were assessed in rats implanted with lumbar intrathecal and epidural catheters. The doses studied were 5, 7.5, 10, 12.5 and 15 micrograms intrathecally and 100, 250, 400 and 500 micrograms epidurally. It appears that if the intrathecal doses of SST are kept below 15 micrograms and the epidural doses below 250 micrograms, the prolonged tail-flick latency can be separated from the transient motor blockade. The antinociception appears not to be attributable to neurotoxicity by the histological evidence available.

Amino acid-mediated EPSPs at primary afferent synapses with substantia gelatinosa neurones in the rat spinal cord

1. Fast excitatory postsynaptic potentials (EPSPs) evoked by stimulation of A delta and C fibres were examined by intracellular recording from substantia gelatinosa (SG) neurones in a transverse slice preparation of adult rat spinal cord. 2. Single low-intensity stimuli applied to the dorsal root activated A delta fibres and evoked monosynaptic EPSPs in 70% of SG neurones. In 5% of SG neurones, increasing the intensity and duration of stimulation evoked solely C fibre-mediated EPSPs. About 20% of neurones received both A delta and C fibre input from primary afferents. 3. Low concentrations of tetrodotoxin (TTX, approximately 50 nM) blocked EPSPs evoked by stimulation of A delta fibres without affecting those evoked by C fibre stimulation. Higher concentrations of TTX (500 nM) also blocked C fibre-evoked responses. 4. EPSPs evoked by A delta and C fibre stimulation reversed in polarity at membrane potentials near 0 mV, similar to the reversal potential of spontaneous EPSPs and of the potential change evoked by exogenous glutamate. 5. A delta and C fibre-evoked EPSPs were depressed by kynurenate and 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX); C fibre-evoked EPSPs appeared to be less sensitive. 6. In the presence of TTX, only 50% of SG neurones were depolarized by L-glutamate. However, neurones which exhibited no direct response to L-glutamate received afferent-evoked EPSPs which were sensitive to CNQX. In sensitive neurones, the depolarization evoked by L-glutamate was depressed by only approximately 15% in the presence of CNQX, whereas afferent-evoked EPSPs recorded from the same neurone were almost completely suppressed. Combined application of DL-2-amino-5-phosphonovaleric acid (APV) and CNQX depressed the response to L-glutamate by only approximately 25%. 7. These findings suggest that A delta and C fibres use L-glutamate or a related amino acid as a transmitter at synapses with substantia gelatinosa neurones. The postsynaptic actions of this transmitter are mediated predominantly by non N-methyl-D-aspartic acid (NMDA) receptors. The failure of CNQX and APV to completely block the L-glutamate-evoked depolarization of substantia gelatinosa neurones raises the possibility that exogenously applied L-glutamate activates a non-NMDA receptor distinct from that which mediates the actions of the synaptically released afferent transmitter.

Selective neuronal glycoconjugate expression in sensory and autonomic ganglia: relation of lectin reactivity to peptide and enzyme markers

Several plant lectins were used to characterize the cell-surface carbohydrates expressed on sensory ganglion cells and their central terminals in the spinal cord dorsal horn. In the rat, galactose-terminal glycoconjugates on a large subpopulation of small neurons whose central axons project to the substantia gelatinosa were demonstrated with the alpha-D-galactose-specific Griffonia Simplicifolia I-B4 (GSA) lectin. This neuron subset was labelled by alternative D-galactose-, N-Acetylgalactosamine-, and beta Gal(1,3)NAcGal-binding lectins. Similar GSA lectin reactivity was also illustrated in selected peripheral autonomic, gustatory and visceral sensory and enteric neurons, and the accessory olfactory bulb. The sensory neuron-specific isoenzyme, fluoride-resistant acid phosphatase (FRAP) co-localized with the GSA lectin, as did the monoclonal antibody (MAb) 2C5, which is directed against a lactoseries carbohydrate constituting a backbone structure of ABH human blood group antigens. In contrast, calcitonin gene-related peptide-immunoreactivity (CGRP-IR), used as a representative marker of peptidergic neurons, exhibited limited co-localization with GSA. A polyclonal anti-rat red blood cell (RBC) antibody co-localized with GSA, suggesting that lectin-reactive carbohydrates on rat sensory neurons are related to rat RBC antigens. In the human spinal cord, the L-fucose-binding Ulex europaeus-I (UEA) lectin also labelled the substantia gelatinosa; in rabbit, a small sensory ganglion cell subset and the spinal cord substantial gelatinosa was co-labelled by both the GSA and UEA lectins. These studies illustrate significant lectin-reactive cell surface carbohydrate expression by non-peptidergic, FRAP(+) sensory ganglion cells in the rat, and provide a means for visualizing the extensive, non-peptidergic, small sensory ganglion cell subpopulations, probably including a substantial proportion of nociceptive and unmyelinated peripheral axons.

Evidence that substance P selectively modulates C-fiber-evoked discharges of dorsal horn nociceptive neurons

Previous studies suggest that the undecapeptide substance P (SP) functions as a primary afferent neurotransmitter or neuromodulator of nociception which may mediate the slow temporal summation ('windup') of discharges of dorsal horn nociceptive neurons elicited by repetitive stimulation of C-afferents. The present study tested this hypothesis by investigating the effects of local spinal application of SP and an SP antagonist. [D-Pro2,D-Trp7,9]-SP (DPDT), on A- and C-fiber-evoked firing of dorsal horn neurons in an intact, urethane-anesthetized rat preparation. Extracellular single unit recordings from both wide dynamic range and nociceptive specific neurons during controlled repetitive electrical stimulation of the ipsilateral hind paw indicated that SP enhanced C-evoked firing in an apparent dose-related manner (100 greater than 20 = 4 nmol), whereas DPDT inhibited C-evoked discharges with an apparent bell-shaped dose-response (20 greater than 100 = 4 nmol). Neither agent significantly altered either A-evoked or spontaneous activity. In agreement with previous investigators, morphine sulfate also selectively inhibited C-fiber-evoked firing without altering A-fiber-mediated activity, validating the selectivity of our system. These findings provide additional evidence that SP functions as a neuromodulator of primary afferent nociception, and further suggest that the effects of SP are selective to nociceptive transmission mediated by C-fibers.

Immunohistochemical evidence for the selective involvement of dorsal root fibres in Friedreich's ataxia

An immunohistochemical study was carried out in order to elucidate the selective involvement of the dorsal root fibres from two patients with Friedreich's ataxia in comparison with those of 10 neurologically normal control individuals. For this purpose, antibodies to substance P and to synaptophysin were used. Substance P-immunoreactive unmyelinated fibres forming a dense network in the normal substantia gelatinosa of the spinal dorsal horn predominantly originate from a subpopulation of small cells of the dorsal root ganglia, while synaptophysin is present in virtually all nerve cell axon terminals and is useful for visualizing axon terminals in the nervous system. Strong substance P-like immunoreactivity was seen in the substantia gelatinosa of patients with Friedreich's ataxia. By contrast, there was marked depletion of synaptophysin immunoreactivity in the posterior column nuclei, with the gracile nucleus showing greater loss of positive puncta than the cuneate nucleus.

Primary afferent origin of substance P-containing axons in the superficial dorsal horn of the rat spinal cord: depletion, regeneration and replenishment of presumed nociceptive central terminals

Substance P-like immunoreactivity (SPLI) was localized in the superficial spinal dorsal horn of the rat by means of light and electron microscopic immunocytochemical techniques. Serial immunocytochemical sections were subjected to densitometric measurements with an electronic Image Analyser, and with aid of a computer program, a two-dimensional reconstruction of the fine neuroanatomical structure of the SPLI-active regions of the lumbosacral upper superficial spinal dorsal horn was obtained. SPLI activity in the superficial dorsal horn outlines four well-marked and distinctly differing regions, called, in the mediolateral sequence, areas A, B, C, and D, plus Cajal's noyeau interstitiel ("lateral spinal nucleus" = "nucleus of the dorsolateral fascicle," L). Lumbosacral dorsal rhizotomy results in an almost complete depletion of SPLI from ipsilateral areas A, B, C, and D; it induces decreased SPLI in the area of the lateral spinal nucleus (L), ipsi- or contralaterally in an alternating fashion. Transection of the segmentally related, ipsilateral peripheral nerve induces a marked depletion of SPLI from areas A, B, and C but only a slight decrease in area D and virtually none in the area of L. Whereas a simple crush of the peripheral nerve (axocompression) induces only a slight depletion of SPLI, if any, semiautomatic densitometric analysis of serial immunocytochemical sections proves that a controlled crush injury (axocontusion) results in depletion of SPLI from the upper dorsal horn, similar to transection of the peripheral nerve. Following regeneration of the ipsilateral, segmentally related peripheral nerve, the original immunocytochemical structure of the superficial dorsal horn is re-established by SPLI-positive axonal sprouts originating from previously damaged dorsal root axons.

Somatostatin is increased in the dorsal root ganglia of adjuvant-inflamed rat

To determine whether biosynthesis of somatostatin is enhanced in the primary sensory neurons by inflammatory pain, we examined the effects of adjuvant inoculation on the content of immunoreactive somatostatin, mainly composed of somatostatin-14 and somatostatin-28, in the dorsal root ganglia and the spinal cord of the rat. The adjuvant inoculation, which produced long-lasting inflammation and hyperalgesia, increased the content of immunoreactive somatostatin, especially somatostatin-14, in the dorsal root ganglia at L4-L6 levels with no change in the dorsal and ventral horns of lumbar enlargement. Such an increase was enhanced by an intrathecal injection of colchicine (0.2 mg) that inhibits axonal flow of somatostatin. Chronic administration of the anti-inflammatory analgesic, sodium diclofenac (3 mg.kg-1.d-1), abolished an adjuvant-induced increase in the content of immunoreactive somatostatin in the dorsal root ganglia. These results suggest that the turnover (biosynthesis and axonal flow) of somatostatin in the primary sensory neurons is enhanced in the presence of persisting inflammatory pain, and support the idea that somatostatin-containing primary afferents are involved in the transmission of pain in the spinal dorsal horn.

Antinociceptive and substance P antagonistic effects of intrathecally injected spantide II in rat: no signs of motor impairment or neurotoxicity

The effect of intrathecally (i.t.) applied substance P (SP) analogue, (D-NicLys1,3-Pal3,D-Cl2Phe5,Asn6,D-Trp7,9,Nle 11)-SP (Spantide II), was examined in rats. Spantide II even at a high dose (10 micrograms) did not evoke any behavioural responses and caused no motor disturbances, but it did have a brief antinociceptive effect on the hot-plate test. Spantide II dose-dependently reduced the caudally directed scratching/biting behaviour, evoked by 1 microgram i.t. SP for over 30 min, but did not block the caudally directed scratching behaviour evoked by i.t. somatostatin. Histological examination revealed no pathological changes in the spinal cord after treatment with Spantide II. The results indicate that Spantide II is an effective tachykinin antagonist in the central nervous system and that it causes no neural damage.