A quantitative correlation of substance P-, calcitonin gene-related peptide- and cholecystokinin-like immunoreactivity with retrogradely labeled trigeminal ganglion cells innervating the eye

Neuroanatomy and Neurochemistry of Mouse Cornea

Purpose

To investigate the entire nerve architecture and content of the two main sensory neuropeptides in mouse cornea to determine if it is a good model with similarities to human corneal innervation.

Methods

Mice aged 1 to 24 weeks were used. The corneas were stained with neuronal-class βIII-tubulin, calcitonin gene–related peptide (CGRP), and substance P (SP) antibodies; whole-mount images were acquired to build an entire view of corneal innervation. To test the origin of CGRP and SP, trigeminal ganglia (TG) were processed for immunofluorescence. Relative corneal nerve fiber densities or neuron numbers were assessed by computer-assisted analysis.

Results

Between 1 and 3 weeks after birth, mouse cornea was mainly composed of a stromal nerve network. At 4 weeks, a whorl-like structure (or vortex) appeared that gradually became more defined. By 8 weeks, anatomy of corneal nerves had reached maturity. Epithelial bundles converged into the central area to form the vortex. The number and pattern of whorl-like structures were different. Subbasal nerve density and nerve terminals were greater in the center than the periphery. Nerve fibers and terminals that were CGRP-positive were more abundant than SP-positive nerves and terminals. In trigeminal ganglia, the number of CGRP-positive neurons significantly outnumbered those positive for SP.

Conclusions

This is the first study to show a complete map of the entire corneal nerves and CGRP and SP sensory neuropeptide distribution in the mouse cornea. This finding shows mouse corneal innervation has many similarities to human cornea and makes the mouse an appropriate model to study pathologies involving corneal nerves.

Morphological and immunohistochemical characterization of the trigeminal ganglion neurons innervating the cornea and upper eyelid of the rat

The cornea is sensitive to nociceptive stimuli and receives dense sensory innervations from the trigeminal ganglion, which also innervates the upper eyelid. We investigated the morphological and immunohistochemical characterization of the trigeminal ganglion neurons innervating the cornea and upper eyelid. We injected the retrograde tracer Fluoro-Gold (FG) into the cornea and the retrograde tracer cholera toxin subunit b (CTb) into the upper eyelid of the same animal. Less than 10% of the FG-labeled neurons were also labeled with CTb. The FG-labeled neurons were small (29.6+/-0.6microm), while the CTb-labeled neurons were large (36.1+/-0.5microm). We also characterized the neurons in the trigeminal ganglion with the retrograde tracer FG following its injection into the cornea or the upper eyelid, and immunohistochemical double-labeling with nociception-related neuronal markers, such as calcitonin gene-related peptides (CGRP), transient receptor potentiated vanilloid 1 (TRPV1), and substance P (SP). About 27% of the neurons innervating the cornea were double-labeled with CGRP, about 23% with TRPV1, and about 8% with SP. About 4% of the neurons innervating the upper eyelid were double-labeled for CGRP, about 11% for TRPV1, and 3% for SP. Thus, the percentages of double-labeled neurons for the neurons innervating the cornea were higher than those for the neurons innervating the upper eyelid. These results indicate that the cornea and the upper eyelid receive innervations mainly from different neurons of the trigeminal ganglia. The cornea is innervated by many characteristic sensory neurons containing nociception-related neuronal markers.

Immunohistochemical localization of substance P, calcitonin gene-related peptide, galanin and calcium-binding proteins in trigeminal ganglia of goat (Capra hircus)

The objectives of this study was to provide a quantitative analysis of calcium-binding proteins, calbindin (CB), parvalbumin (PA), substance P (SP), calcitonin gene-related peptide (CGRP) and galanin (GAL), in trigeminal ganglia of goats, to establish whether they exhibit coexistence relationships between each other, and to examine possible colocalization with SP, CGRP and GAL, which have been well characterized according to their distributions in an abundance of large and/or small neurones. CB (12.78%), PA (31.91%), SP (24.63%), CGRP (44.44%) and GAL (3.29%) immunoreactive (IR) cells were observed. About 38.37, 8.7 and 0.73% of CGRP-IR neurones in the trigeminal ganglion were also immunoreacted with SP, GAL and CB, respectively. Almost all SP-IR cells are labelled with CGRP (approximately 92.52%), whereas only 16.02 and 0.44% of SP-IR neurones colocalized with GAL and CB. Approximately 4.65 and 1.10% of the CB-IR cells were found to contain CGRP and SP immunoreactivity, respectively. Conversely, no CB-IR cell exhibited GAL immunoreactivity. In addition, all the GAL-IR cells showed CGRP and SP immunoreactivity. The number of CB-, PA-, SP-, CGRP- and GAL-IR neurones in goat trigeminal ganglion are abundant than that of other animals. These results elucidate that the goat differs from other mammalian species in the distribution and localization of neurochemical substances in trigeminal ganglia, and suggest that this difference may be relevant to the morphological characteristics of cerebral vasculatures such as epidural rete mirabile of goat.

Comparative analysis of the chemical neuroanatomy of the mammalian trigeminal ganglion and mesencephalic trigeminal nucleus

A characteristic peculiarity of the trigeminal sensory system is the presence of two distinct populations of primary afferent neurons. Most of their cell bodies are located in the trigeminal ganglion (TG) but part of them lie in the mesencephalic trigeminal nucleus (MTN). This review compares the neurochemical content of central versus peripheral trigeminal primary afferent neurons. In the TG, two subpopulations of primary sensory neurons, containing immunoreactive (IR) material, are identified: a number of glutamate (Glu)-, substance P (SP)-, neurokinin A (NKA)-, calcitonin gene-related peptide (CGRP)-, cholecystokinin (CCK)-, somatostatin (SOM)-, vasoactive intestinal polypeptide (VIP)- and galanin (GAL)-IR ganglion cells with small and medium-sized somata, and relatively less numerous larger-sized neuropeptide Y (NPY)- and peptide 19 (PEP 19)-IR trigeminal neurons. In addition, many nitric oxide synthase (NOS)- and parvalbumin (PV)-IR cells of all sizes as well as fewer, mostly large, calbindin D-28k (CB)-containing neurons are seen. The majority of the large ganglion cells are surrounded by SP-, CGRP-, SOM-, CCK-, VIP-, NOS- and serotonin (SER)-IR perisomatic networks. In the MTN, the main subpopulation of large-sized neurons display Glu-immunoreactivity. Additionally, numerous large MTN neurons exhibit PV- and CB-immunostaining. On the other hand, certain small MTN neurons, most likely interneurons, are found to be GABAergic. Furthermore, NOS-containing neurons can be detected in the caudal and the mesencephalic-pontine junction portions of the nucleus. Conversely, no immunoreactivity to any of the examined neuropeptides is observed in the cell bodies of MTN neurons but these are encircled by peptidergic, catecholaminergic, serotonergic and nitrergic perineuronal arborizations in a basket-like manner. Such a discrepancy in the neurochemical features suggests that the differently fated embryonic migration, synaptogenesis, and peripheral and central target field innervation can possibly affect the individual neurochemical phenotypes of trigeminal primary afferent neurons.

Sensory innervation of the guinea pig extraocular muscles: a 1,1'-dioctadecyl-3,3,3'3'-tetramethylindocarbocyanine perchlorate tracing and calcitonin gene-related peptide immunohistochemical study

The sensory apparatus of the extraocular muscles attains special interest because of the great variation among different species with respect to the proprioceptors. The sensory innervation of the guinea pig extraocular muscles, lacking both muscle spindles and tendon organs, was investigated with a fluorescence double-labelling method. Primary sensory perikarya were assessed by postmortem application of 1,1'-dioctadecyl-3,3,3'3'-tetramethylindocarbocyanine perchlorate (Di-I) to the extraocular muscle nerves. Traced neurons were found in the ipsilateral ophthalmic part of the trigeminal ganglion. This is in line with findings in other species. Calcitonin gene-related peptide (CGRP) was detected immunohistochemically within the trigeminal ganglion. No somatotopic organization was observed for CGRP-like immunoreactive perikarya. Small (maximal diameter below 30 microm), medium (maximal diameter between 30 and 50 microm), and large (maximal diameter larger than 50 microm) trigeminal ganglion cells were found among the primary afferent perikarya from extraocular muscles. Among CGRP-like immunoreactive cells, only small and medium cells were observed. Double-labelling experiments indicated the CGRP content of primary afferents of the guinea pig extraocular muscles. The relationship to former morphological categories of ganglion cells is discussed. Primary afferent neurons with CGRP-like immunoreactivity might have efferent functions and might also be involved in inflammatory processes of extraocular muscles.

Central projection of calcitonin gene-related peptide (CGRP)- and substance P (SP)-immunoreactive trigeminal primary neurons in the rat

Substance P (SP) is implicated in transmission of primary afferent nociceptive signals. In primary neurons, SP is colocalized with calcitonin gene-related peptide (CGRP), which is another neuropeptide marker for small to medium primary neurons. CGRP coreleased with SP augments the postsynaptic effect of SP and thereby modulates the nociceptive transmission. This study demonstrates the distribution of CGRP-like immunoreactivity (-ir) and SP-ir in the lower brainstem of normal rats and after trigeminal rhizotomy or tractotomy at the level of subnucleus interpolaris (Vi). By comparing the results obtained from normal and deafferented rats, we analyzed the central projection of trigeminal primary nociceptors. The CGRP-immunoreactive (-ir) trigeminal primaries projected to the entire rostrocaudal extent of the spinal trigeminal nucleus, the principal nucleus (PrV), the paratrigeminal nucleus (paraV), and the lateral subnucleus of solitary tract nucleus (STN) on the ipsilateral side. The trigeminal primaries projecting to the spinal trigeminal nucleus, paraV and STN also contained SP-ir. The ipsilateral trigeminal primaries were the exclusive source of CGRP-ir terminals in the PrV, the Vi and the dorsomedial nucleus within the subnucleus oralis (Vo). The medullary dorsal horn (MDH) and the lateral edge of Vo received convergent CGRP-ir projection from the ipsilateral trigeminal primaries and other neurons. The glossopharyngeal and vagal primaries are candidates for the source of CGRP-ir projection to the Vo and the MDH, while the dorsal root axons supply the MDH with CGRP-ir terminals. In addition, contralateral primary neurons crossing the midline appear to contain CGRP and to terminate in the MDH.

Light microscopic localization of calcitonin gene-related peptide in the normal feline trigeminal system and following retrogasserian rhizotomy

Calcitonin gene-related peptide (CGRP) is a neuropeptide that has been implicated in the transmission and modulation of primary afferent nociceptive stimuli. In this study, we describe the light microscopic distribution of CGRP immunoreactivity (IR) within the feline trigeminal ganglion and trigeminal nucleus of normal adult subjects and in subjects 10 and 30 days following complete retrogasserian rhizotomy. Within the trigeminal ganglion of normal subjects, cell bodies and fibers showed CGRP-IR, whereas immunoreactive fibers were rare in the central root region. Within the normal spinal trigeminal and main sensory nuclei, CGRP-IR was seen to form a reproducible pattern that varied between the different nuclei. Following rhizotomy, most, but not all, of the CGRP-IR was lost from the spinal trigeminal and main sensory nuclei, except in regions where the upper cervical roots and cranial nerves VII, IX and X project into the trigeminal nucleus. The pattern seen at 10 days contained more CGRP-IR than that seen at 30 days and suggests that degenerating fibers still show CGRP-IR. In contrast to the decrease seen in the nuclei after rhizotomy, examination of the central root that was still attached to the trigeminal ganglion showed an increase in CGRP-IR within fibers, some of which ended in growth conelike enlargements. Rhizotomy induced a dramatic increase in CGRP-IR within trigeminal motoneurons and their fibers, which was strongest 10 days after rhizotomy and weaker at 30 days, which was still stronger than normal. These results indicate that the majority of CGRP-IR found in the trigeminal nucleus originates from trigeminal primary afferents and that an upregulation of CGRP-IR occurs in trigeminal motoneurons and in regenerating fibers in the part of the central root that was still attached to the ganglion. In addition, the persistence of CGRP-IR fibers in the trigeminal nucleus provides one possible explanation for the preservation of pain in humans following trigeminal rhizotomy.

Increased release of immunoreactive calcitonin gene-related peptide (CGRP) in tears after excimer laser keratectomy

The purpose of the study was to quantify the neuropeptide calcitonin gene-related peptide (CGRP) in normal human tear fluid and to determine the effect of photorefractive excimer laser keratectomy (PRK) on its release in tears. CGRP was assayed in tear fluid samples using an enzyme immunoassay (detection limit 0.2 micrograms ml-1). Tear-fluid samples were collected preoperatively, 1, 2 and 7 days after PRK and analysed for CGRP. The changes in tear-fluid secretion were also monitored. The intra-assay variation was 3.0-7.0%. Despite the marked hypersecretion of tears, the concentration of CGRP did not decrease following PRK indicating a concomitant increase in CGRP release by sensory nerves and/or lacrimal gland(s). Consequently, the release of CGRP in tears increased from 197.9 +/- 36.6 ng min-1 (mean +/- S.E.M.) to 1723.0 +/- 402.4 ng min-1 (P < 0.01) on day 1, and to 2304.2 +/- 561.1 ng min-1 (P < 0.01) on day 2. On day 7, only minor elevation (377.02 +/- 83.24 ng min-1) was observed. It is concluded that CGRP is a component of normal human tear fluid. The ocular irritation response related to the photoablation induces an enhanced release of CGRP in tears. As a compound present in corneal sensory nerves CGRP may have a role in wound-healing.

Immunohistochemical localization of neuropeptides in the human ciliary ganglion

In human ciliary ganglia, 18% of neurons were in contact with substance P (SP) and 12% with calcitonin gene-related peptide (CGRP) like-immunoreactive (LI) varicose axons. CGRP was colocalized with SP. Numerous SP-LI and CGRP-LI non-varicose nerve fibers were found between the ganglion cells and in nerve trunks that entered the ganglia. Axons immunoreactive for neuropeptide Y (NPY), vasoactive intestinal polypeptide (VIP), tyrosine hydroxylase (TH) or dopamine-beta-hydroxylase (DBH) never contacted neuronal cell bodies. Perikarya of ciliary neurons neither stained for any of the neuropeptides nor for DBH. 23% of ciliary perikarya were TH-immunoreactive. These observations suggest an innervation of human ciliary ganglion neurons by peptidergic primary afferent collaterals presumably of trigeminal origin.

Distribution of calcitonin gene-related peptide- and neuropeptide Y-like immunoreactivity in the trigeminal ganglion and mesencephalic trigeminal nucleus of the cat

The distribution of calcitonin gene-related peptide (CGRP)- and neuropeptide Y (NPY)-like immunoreactivity (LI) in the cat trigeminal ganglion (TrG) and mesencephalic trigeminal nucleus (MTN) was studied by the indirect immunofluorescent technique and unlabelled peroxidase-antiperoxidase method. A positive reaction for both CGRP and NPY was found only in the TrG primary afferent neurons. Between 40% and 50% of the perikarya displayed CGRP-LI whereas few of the trigeminal principal neurons (approximately 1%) showed NPY-LI. Most of the CGRP-immunoreactive cells were small to medium-sized (20-40 microns in diameter) and were distributed throughout the ganglion. NPY appeared specifically in medium-sized to large-sized trigeminal neurons (up to 60 microns). CGRP and NPY also occurred in varicose nerve fibres running among the cell bodies and in pericellular baskets around a small number of large unstained ganglion cells. In contrast, CGRP- and NPY-LI were present only in the nerve fibres and terminals of the cat MTN. The immunoreactive varicosities travelled towards the negative MTN neurons and formed basket-like arborizations around their cell bodies. Synaptic contact between the immunolabelled axonal profiles and perikarya of trigeminal primary afferent neurons could not be seen in the TrG and MTN of the cat. The results provide further evidence for the interrelation between sensory and autonomic systems.

Comparative efficacy of expression of genes delivered to mouse sensory neurons with herpes virus vectors

To achieve gene delivery to sensory neurons of the trigeminal ganglion, thymidine kinase-negative (TK-) herpes simplex viruses (HSV) containing the reporter gene lacZ (the gene for E. coli beta-galactosidase) downstream of viral (in vectors RH116 and tkLTRZ1) or mammalian (in vector NSE-lacZ-tk) promoters were inoculated onto mouse cornea and snout. Trigeminal ganglia were removed 4, 14, 30, and 60 days after inoculation with vectors and histochemically processed with 5-bromo-4-chloro-3 indolyl-beta-galactoside (X-Gal). With vector tkLTRZ1, large numbers of labeled neurons were observed in rostromedial and central trigeminal ganglion at 4 days after inoculation. A gradual decline in the number of labeled neurons was observed with this vector at subsequent time points. With vectors RH116 and NSE-lacZ-tk, smaller numbers of labeled neurons were seen at 4 days following inoculation than were observed with vector tkLTRZ1. No labeled neurons could be observed at 14 days after inoculation with vectors RH116 and NSE-lacZ-tk. Immunocytochemistry for E. coli beta-galactosidase and in situ hybridization to HSV latency-associated transcripts revealed labeled neurons in regions of the trigeminal ganglion similar to that observed with X-Gal staining. A comparable distribution of labeled neurons in trigeminal ganglion was also observed after application of the retrograde tracer Fluoro-Gold to mouse cornea and snout. These data provide evidence that retrogradely transported tk- herpes virus vectors can be used to deliver a functional gene to sensory neurons in vivo in an anatomically predictable fashion.

Immunohistochemical identification of trigeminal ganglion neurons that innervate the mouse cornea: relevance to intercellular spread of herpes simplex virus

Inoculation of the scarified cornea with herpes simplex virus (type 1) leads to herpetic infection of trigeminal ganglion cells. A recent study of the susceptibility of ganglion cells revealed that there may be at least four populations of trigeminal ganglion cells that are infectable by herpes. Two classes were identified by their neuropeptide content: Substance P or calcitonin gene-related peptide. One class was identified by its affinity for a monoclonal antibody, SSEA-3. The fourth class was recognized by its common affinity for both the monoclonal antibody LD2 and for the lectin Bandeiraea simplicifolia isolectin. However, there has been no direct evidence of which types are infected directly as a result of retrograde transport from the corneal site and which may be infected by cell-to-cell spread. The aim of this study was to determine which classes of neurons, which are known to become infected with HSV after ocular inoculation, supply corneal innervation. We have identified four classes of trigeminal ganglion neurons that supply axons to the central cornea of the mouse, on the basis of their ability to transport Fluoro-Gold retrograde from axons in the central corneal epithelium and stroma. About 40% of the neurons that innervate the cornea contain Substance P or calcitonin gene-related peptide; about 60% of the neurons that innervate the cornea react with the monoclonal antibody SSEA-3. About 36% of all neurons in the whole ophthalmic division react with the LD2 or Bandeiraea simplicifolia isolectin, and Fluoro-Gold labels only 2% of them.(ABSTRACT TRUNCATED AT 250 WORDS)

Substance P augments the rate of vasodilation induced by calcitonin gene-related peptide in porcine ophthalmic artery in vitro

Peptides may function as neurotransmitters liberated antidromically by sensory nerve fibres, provoking vascular responses having potential importance in some neurological disorders. Dose-response relaxation curves induced by substance P (SP) and calcitonin gene related peptide (CGRP) have been studied in porcine ophthalmic arteries in vitro. Both peptides induced vasodilation when tested separately (CGRP much greater than SP). Because of the putative interactions between such peptides in this vascular territory, a computerised system was also used for analysing over time the response to a single addition of either 10(-8) M CGRP, 10(-8) M SP or a combination of 10(-8) M SP + 10(-8) M CGRP. SP did not augment the maximum relaxation induced by CGRP alone, but increased significantly the rate of relaxation during the initial phase of the response. The effect induced by the SP+CGRP combination was stronger than the sum of the individual SP and CGRP-induced relaxations during the first 4 min of the response, which suggests a SP-CGRP synergism in this artery.

Calcitonin gene-related peptide in the human trigeminal sensory system at developmental and adult life stages: immunohistochemistry, neuronal morphometry and coexistence with substance P

The distribution of calcitonin gene-related peptide (CGRP) has been examined by the indirect immunofluorescence technique in the Gasserian ganglion and spinal nucleus of the human trigeminal nerve. In the ganglion CGRP is present in almost 50% of primary sensory neurons, in varicose and non-varicose nerve fibres and in pericellular basket-like plexuses around non-immunoreactive ganglionic perikarya. Morphometric analysis reveals that the CGRP-positive neuronal population is heterogeneous in cell size. Observation of specimens from subjects at fetal, perinatal and adult life stages reveals that the percentage of CGRP-immunoreactive cells reaches a maximum at perinatal stages and then remains constant, declining only in old age. Pericellular basket-like nerve fibres are detectable only in fetal and pre-term and full-term newborn tissue. Coexistence between CGRP and substance P (SP) occurs, SP being present in about one quarter of the CGRP-immunoreactive neurons and CGRP being localized in a little more than half of the SP-immunoreactive neurons. However, perikarya, nerve fibres and pericellular fibres containing only one or other peptide are also present. Bundles of immunoreactive fibres and dot-like nerve terminals occur in the spinal tract and superficial and deep regions of the spinal trigeminal nucleus. A particularly dense plexus is present in the peripheral nuclear layers. Double immunostaining shows a similar regional distribution for SP. However, in inner substantia gelatinosa the density of CGRP-immunoreactive fibres is much higher than that of SP-immunoreactive ones. The results obtained add information to our knowledge of the organization of neurochemically identified neurons in the human trigeminal sensory system.

Localization of gastrin-releasing peptide (GRP)-like immunoreactivity in the lysosomal compartment of the trigeminal ganglion cells of the rat

Cellular and subcellular localizations of gastrin-releasing peptide-like immunoreactivity (GRP-LI) were examined in the perikarya of trigeminal ganglion cells. By immunolight microscopy using semi-thin sections, GRP-LI was observed in almost all the neuronal somata with various intensity as granular profiles distributing widely in the cytoplasm. By immunoelectron microscopy using ultrathin frozen sections and protein A-gold, GRP-LI was found predominantly in rounded or oval membrane-bound structures which were 300-800 nm in diameter and displayed various electron-density and heterogenous contents. Double-labeling immunoelectron microscopy using antibodies for GRP and cathepsin L, a well-characterized lysosomal proteinase, clearly demonstrated that these GRP-immunoreactive intracytoplasmic structures were lysosomes. In contrast, GRP-LI was detected only occasionally in the large granular vesicles (100-200 nm in diameter). These findings strongly suggest that considerable amount of GRP or GRP-like peptide is subject to intracellular degradation in the lysosome rather than to the regulatory secretion pathway, and this is the reason why no fibers immunoreactive for GRP have been detected in the peripheral sensory field.

Cholecystokinin contracts isolated human and monkey iris sphincters; a study with CCK receptor antagonists

The contractile effects of cholecystokinin (CCK) on iris sphincter and ciliary muscles from monkey and human eyes were studied using an isolated smooth muscle bath. The ability of the CCKA receptor antagonists, lorglumide and loxiglumide, to inhibit CCK-8s-induced contraction was also examined. Various neuropeptides reported to be present in capsaicin-sensitive sensory neurons were also screened for contractile effect. CCK contracted isolated human and monkey iris sphincters at nM concentrations. Both antagonists caused a rightward shift of the dose-response curve for CCK-8s on the monkey iris sphincter. The ciliary muscle from both species failed to contract in response to CCK-8s. Of the eight other neuropeptides screened on the monkey iris sphincter, only [Arg8]vasopressin elicited a weak contraction when used in microM concentrations. These results indicate that the primate iridial sphincter muscle exhibits a high sensitivity to CCK, and that CCKA receptor antagonists effectively block the CCK-induced contraction.

Facilitatory role of calcitonin gene-related peptide (CGRP) on excitation induced by substance P (SP) and noxious stimuli in rat spinal dorsal horn neurons. An iontophoretic study in vivo

The effects of iontophoretically applied calcitonin gene-related peptide (CGRP) and/or substance P (SP) onto physiologically identified neurons in the rat lumbar dorsal horn were studied. The consistent excitatory effects of SP found on the spontaneous and the noxious evoked activity were significantly potentiated by CGRP application. This peptide facilitated the noxious evoked activity and did not affect the spontaneous activity of the neurons. The responses to non-noxious stimuli were unaffected in all cases.

SP-like immunoreactivity in the primary trigeminal neurons projecting to the nucleus tractus solitarii

Using the double-labeling method of retrograde transport of HRP combined with PAP immunocytochemistry, the neurons containing SP-like immunoreactivity (SPLI) of the trigeminal nerve projecting to the nucleus tractus solitarii (NTS) were examined. HRP-SP double-labeled neurons in the trigeminal ganglion, mainly small or middle-sized, were found after the NTS or the lingual nerve was injected with HRP followed by SP-immunoreaction. These findings demonstrate that the projection of the trigeminal nerve to the NTS contains SPLI.

Ultrastructural identification of trigeminal nerve terminals in the pterygopalatine ganglion of rats: an anterograde tracing and immunohistochemical study

Trigeminal nerve terminals in the rat pterygopalatine ganglion (PPG) were ultrastructurally identified using anterograde tracing with Phaseolus vulgaris-leucoagglutinin (PHA-L). Electron microscopic immunohistochemistry was used to demonstrate the presence of substance P (SP) and calcitonin gene-related peptide (CGRP) in nerve terminals of the PPG. Adjacent to the rostral part of the PPG an additional minor area was described. Perikarya in this minor rostral part were more spherical and had irregular outlines. Ultrastructurally, the glial enwrapment of the nerve terminals seemed to be more loosely arranged in comparison to that in the major rostral part of the PPG. With PHA-L, numerous labelled nerve fibres and terminals were found in all parts of the PPG. The ultrastructure of these terminals was uniform, many of them showing synaptic contacts. Numerous terminals in the PPG were SP-positive, whereas only a few were CGRP-positive. Fibres stained positive for both neuropeptides. The PPG is shown to be synaptically innervated by sensory fibres arising in the trigeminal ganglion, with the strong suggestion of SP and CGRP acting as neurotransmitters. A modulatory interaction between the autonomic and sensory system, resembling an axon reflex mechanism in the peripheral nervous system is endorsed.

Ultrastructural immunocytochemical localization of herpes simplex virus (type 1) in trigeminal ganglion neurons

Four days after corneal inoculation of mice with herpes simplex (type 1) virus (HSV), infected trigeminal ganglion cells with and without calcitonin gene-related peptide (CGRP) antigenicity were examined by electron microscopy in sections treated with colloidal gold labeled antibodies. Cells that contain CGRP were identified by the dense gold labeling of small vesicles about 100 nm in diameter. Adjacent thin sections were stained using an indirect colloidal gold immunocytochemical technique to reveal HSV-1 antigens. In CGRP-positive neurons, HSV antigens were located over both nuclear and cytoplasmic compartments. HSV label was found over cytoplasmic vesicles that were significantly larger than those labeled with anti-CGRP antisera; the HSV-containing vesicles ranged in profile diameter from less than 170 to greater than 400 nm. There was no overlap in the distribution of the two labels. Thus, for this time period, the organelles involved in transport of the endogenous neuropeptide and HSV appear to remain discrete. Furthermore, there was no significant difference in the distribution of HSV in CGRP-reactive and CGRP-negative trigeminal ganglion cells. Thus, there is no indication of a preferential distribution or limited replication of HSV in CGRP-positive neurons.

Coexistence and plasticity of neurotransmitters and neuropeptides in the rat iris

The presence, distribution and origin of substance P (SP), neuropeptide Y (NPY), and CGRP-immunoreactive axons in rat iris were investigated in whole mount preparations, with special respect to the localization of the "classical" adrenergic and cholinergic ground plexuses. SP-IR fibres are distributed parallel to the pupillary margin in the sphincter muscle, and in an irregular plexus in the dilator muscle. The distribution of CGRP-IR fibres was similar to this. Both SP- and CGRP-IR elements originated from the Gasserian ganglion. Following electrocoagulation of the ophthalmic nerve, both SP- and CGRP-IR nerves completely disappeared, while in the caudal nucleus of the trigeminal nerve a substantial decrease of the immunoreactivity was found. NPY-IR fibres have also been demonstrated in the anterior uvea, displaying a pattern similar to that of the adrenergic nerves. In the sympathectomized iris, there was a marked decreased in the density of NPY-IR fibres indicating that NPY most likely coexists with the classical sympathetic neurotransmitter, noradrenalin in the sympathetic nerve supply deriving from the superior cervical ganglion. 1 month after sympathectomy, there was an increase in the density (and possibly also in the number) of both SP- and CGRP-IR fibres in the denervated iris. Subsequent immuno-electron microscopic analysis has demonstrated that both SP- and CGRP-IR fibres are unmyelinated axons, embedded in a common Schwann cell cytoplasm together with a number of axons devoid of immunoreactivity.(ABSTRACT TRUNCATED AT 250 WORDS)

Peptidergic nerves in human dental pulp. An immunocytochemical study

The peptidergic innervation of human dental pulp was studied with indirect immunofluorescence and immunoperoxidase techniques. Pulpal nerve fibres displaying immunoreactivity for cholecystokinin, calcitonin gene-related peptide, C-terminal flanking peptide of neuropeptide tyrosine, leucine-enkephalin, methionine-enkephalin, neuropeptide K, neuropeptide tyrosine, peptide with N-terminal histidine and C-terminal isoleucine, somatostatin-28, substance P and vasoactive intestinal polypeptide were observed. Immunoreactive axon varicosities were detectable within radicular and coronal nerve trunks and within the nerve plexus of Raschkow in the para-odontoblastic region. Many peptidergic nerve fibres were observed in association with blood vessels of various sizes. Substance P- and calcitonin-gene-related peptide-immunoreactive axons were visible in the odontoblastic layer. The occurrence of VIP- and PHI-immunoreactive fibres lends support to the hypothesis that human tooth may be supplied by parasympathetic nerves. The immunocytochemical results here shown provide a morphological basis to previous experimental studies concerning the possible roles of neuropeptides in nociception mechanisms, control of the blood flow and modulation of the inflammatory response in dental tissues.

Cholecystokinin causes contraction of the pupillary sphincter in monkeys but not in cats, rabbits, rats and guinea-pigs: antagonism by lorglumide

The effects of intracameral injections of cholecystokinin (CCK) on the pupil size were determined in monkeys, cats, rabbits, rats and guinea-pigs. In animals under muscarinic cholinergic blockade, CCK caused miosis in monkeys but not in the other species investigated. In monkeys CCK-8 was more potent than CCK-33, which was, however, much more potent than non-sulphated CCK-8. These observations indicate that peripheral type A receptors mediated the miotic response. The effect of CCK-8 was not appreciably influenced by pretreatment with indomethacin, 3 mg kg-1 body wt, indicating that prostaglandins were not involved in the response. Nerve blockade with 0.9 micrograms tetrodotoxin intracamerally had no clear effect on the dose-response relationship for CCK-8. The effect of the peptide thus seems to be directly on receptors on the pupillary sphincter muscle. Pretreatment with lorglumide caused a dose-dependent rightward shift of the dose-response curve, indicating competitive antagonism. The results indicate that in monkeys, but not in rabbit, cats, rats and guinea-pigs, CCK is a potent miotic with a direct effect on the pupillary sphincter mediated by type A CCK receptors on the muscle.

Substance P-like immunoreactivity in the human trigeminal ganglion

Presence of substance P-like immunoreactive neurons and nerve fibers is demonstrated in the trigeminal ganglion of newborn and adult human subjects by the indirect immunofluorescence technique. Two populations of neurons containing high and low densities of immunoreactive material, respectively, are identified. Morphometric analyses indicate that (i) most of positive neurons are medium and small sized; (ii) immunoreactive perikarya grow in size from newborns to adults, with up to a 50% increase in diameter. Percent frequency of positive perikarya, on the other hand, is higher in newborns (23.6%) and decreases in adults (16.7%).

Cell type and conduction velocity of rat primary sensory neurons with calcitonin gene-related peptide-like immunoreactivity

An immunocytochemical double labelling study of L4 dorsal root ganglia from rats aged seven to 10 weeks was made with an antibody to calcitonin gene-related peptide and with RT97, an anti-neurofilament antibody which specifically labels the light neuron population. Peptide immunoreactivity was found in an average of 46.5% of all neurons. Sixty-two per cent of the small dark (RT97-negative) and 30% of the light (RT97-positive) neuron populations contained the peptide. About one-third (32%) of the cells with peptide immunoreactivity were light cells and about two-thirds (68%) were small dark cells. Intracellular electrophysiological recordings were made in vitro from neurons in lumbar (L4, L5 and L6) dorsal root ganglia from six- to eight-week-old rats, followed by dye-injection and immunocytochemistry. This showed that conduction velocities of neurons with calcitonin gene-related peptide-like immunoreactivity ranged from 0.5 to 28.6 m/s. Seventy-three neurons were successfully processed. Of these, calcitonin gene-related peptide-like immunoreactivity was found in 46% of C-fibre neurons, 33% of A delta-fibre neurons and in 17% of the A alpha/beta-fibre neurons. The peptide-like immunoreactivity was found in approximately 25% of all A-fibre neurons sampled.

The allocation of nerve fibres to the anterior eye segment and peripheral ganglia of rats. I. The sensory innervation

The distribution of sensory trigeminal nerve fibres in the anterior eye segment and the autonomic eye related ganglia, i.e. the parasympathetic ciliary and pterygopalatine ganglia and the sympathetic superior cervical ganglion, was studied in rats. For this the trigeminal ganglion was injected with tritiated leucine and wheat germ agglutinin coupled to horseradish peroxidase (WGA-HRP). After injection of WGA-HRP into the trigeminal ganglion, ganglion cell somata in the superior cervical and the pterygopalatine ganglion were labelled. As labelling of these cell bodies with WGA-HRP is the result of retrograde transport it must be assumed that cell bodies in these ganglia project to the trigeminal ganglion. [3H]Leucine injection into the trigeminal ganglion revealed the presence of labelled nerve fibres in the pterygopalatine ganglion and the nodose ganglion i.e. the sensory ganglion of the vagus nerve. Labelled nerve fibres were absent in the ciliary and superior cervical ganglion. As [3H]leucine labelling of nerve fibres is the result of anterograde transport exclusively, it can be concluded that trigeminal nerve fibres project to the nodose ganglion and the pterygopalatine ganglion, but not to the ciliary and superior cervical ganglion. In the retrobulbar structures, sensory nerve fibres occurred between the inferior oblique and the lateral rectus muscle and were present medial to the medial rectus muscle. Within the anterior eye segment, sensory nerve fibres were found in the cornea epithelium, stroma and adjacent to the endothelium. In addition, labelled fibres were found in the anterior stroma of the ciliary body, throughout the iris up to the pupillary border and in the conjunctiva. Most sensory nerve fibres which innervate the cornea, the iris and the ciliary body traverse the ciliary cleft.

Calcitonin-gene-related-peptide-immunoreactive innervation of the rat head with emphasis on specialized sensory structures

The distribution of calcitonin-gene-related peptide-like immunoreactivity (CGRP-IR) was studied in sections of decalcified rat head and selected whole-mount preparations in order to address the complex peptidergic innervation patterns in peripheral cephalic specialized zones and to examine neuronal ganglia in situ. Labeled neuron somata in trigeminal, glossopharyngeal, and vagal ganglia comprised a large proportion of small to medium size type B ganglion cells. Parasympathetic ganglia (ciliary, otic, sphenopalatine, submandibular) revealed a small population of labeled somata and numerous perisomatic IR axons, whereas sympathetic ganglion cells (superior cervical) were devoid of label though richly innervated by perisomatic IR axons. The gustatory geniculate ganglion contained only a few labeled neurons and axons. Coarse peripheral CGRP-IR axons were traced to skeletal muscle motor end plates (e.g., lingual, tensor tympani, etc.), and thin sensory axons most densely innervated the cornea, iris, general integument, all mucosal epithelia lining the tympanic, nasal, sinus and oropharyngeal cavities, and the cerebral meninges. Blood vessels, glands, ducts, and their orifices were often heavily innervated, and specific specializations and exceptions are discussed. Distinctive patterns of IR innervation characterized the various specialized sensory systems, including 1) cochlear and vestibular hair cells; 2) lingual, palatal, oropharyngeal, and laryngoepiglottal taste buds; 3) main olfactory epithelium and axons projecting to glomeruli in specific sectors of main olfactory bulb; 4) septal-olfactory organ; 5) vomeronasal organ; and 6) the nervus terminalis system. Secretory epithelia (ciliary body, choroid plexus, and stria vascularis) were notably lacking in CGRP-IR. Despite the multiplicity of functionally distinct CGRP neuronal and axonal populations, certain generalizations merit consideration. The extensive innervation of chemosensory nasal and oral epithelia may contribute to specific chemical sensitivities (e.g., relating to olfactory and gustatory senses) as well as evoking "nociceptive" responses to chemical irritants as part of a "common chemical sense." An efferent role for some of these peptidergic afferent axons may also be inferred from their specific distributions. Sites involved in regulating access to and sensitivity of sense organs to external stimuli (e.g., cochlear and vestibular hair cells, taste bud orifices, and main olfactory epithelium) are heavily innervated. Other IR axons are in position to exert control over airflow through nasal turbinates, glandular secretion, blood circulation, and duct transport systems.(ABSTRACT TRUNCATED AT 400 WORDS)

CGRP in relation to neurogenic inflammation and cAMP in the rabbit eye

The effects of topical application of neutral formaldehyde (1%) and intracameral administration of calcitonin gene-related peptide (CGRP, 0.5- or 2.0 micrograms) on the intraocular pressure (IOP), blood-aqueous barrier, pupil size, blood pressure and cyclic AMP (cAMP) content in the aqueous humour of a rabbit were studied. Topical chemical irritation with 1% formaldehyde caused a typical irritative response in the eye with a rise in the IOP, breakdown of the blood-aqueous barrier and miosis. The cAMP content in the aqueous humour was also increased (88.5 +/- 35.0 pmol ml-1, P less than 0.05) when compared with the control group (16.3 +/- 3.6 pmol ml-1). Intracameral administration of CGRP caused a rise in the IOP, breakdown of the blood-aqueous barrier and also systemic hypotension. Miosis was not observed after intracameral CGRP but an increase in the cAMP content in the aqueous humour was seen (130.5 +/- 30.3- and 158.7 +/- 48.1 pmol ml-1, both P less than 0.01, after 0.5 or 2.0 micrograms, respectively). The cAMP concentration in the aqueous humour after topical chemical irritation and intracameral CGRP correlated with the intensity of the breakdown of the blood-aqueous barrier. CGRP seems to cause most, but not all, of the ocular changes after sensory nerve stimulation elicited by topical neutral formaldehyde. Of these CGRP-induced changes, only the breakdown of the blood-aqueous barrier is related to an increase in the cAMP content in the aqueous humour. Contralateral responses after sensory nerve stimulation were similar to contralateral responses to intracameral CGRP.