Distribution of calcitonin gene-related peptide in the rat peripheral nervous system with reference to its coexistence with substance P

Subpopulations of primary sensory neurons show coexistence of neuropeptides and glucocorticoid receptors in the rat spinal and trigeminal ganglia

The coexistence of the neuropeptides substance P, calcitonin gene-related peptide, galanin, somatostatin and neuropeptide Y with glucocorticoid receptors was studied in neurons of the rat lumbar dorsal root and trigeminal ganglia by means of the double immunofluorescence technique. Based on analysis of microphotographs, about one-third of the populations of nerve cells (small and large) containing substance P or calcitonin gene-related peptide immunoreactivity (IR) showed nuclear glucocorticoid receptor IR. A similar pattern was observed within the dorsal root and trigeminal ganglia. Furthermore, within the lumbar dorsal root ganglia 50% of the small neurons, containing galanin IR, possessed nuclear glucocorticoid receptor IR of moderate intensity. Glucocorticoid receptor IR was not observed in the galanin immunoreactive neurons of the trigeminal ganglion neither in the somatostatin and NPY immunoreactive neurons of both the dorsal root and the trigeminal ganglia. The results provide a chemical anatomical basis for a direct regulation by glucocorticoids of distinct populations of substance P and calcitonin gene-related peptide immunoreactive nerve cells in the lumbar spinal and trigeminal ganglia and of galanin immunoreactive nerve cells of the spinal but not of the trigeminal ganglia.

Calcitonin gene-related peptide (CGRP)-like immunoreactivity in motoneurons of the human spinal cord following injury

Changes that occur in the localization of calcitonin gene-related peptide-like-immunoreactivity (CGRP-LI) in motoneurons, following injury to the human spinal cord, were examined. CGRP-LI above and below the level of injury was compared to normal human spinal cord. Vibratome sections were cut and processed for immunostaining using the avidin-biotin immunoperoxidase method. Whereas motoneurons above the lesion contained CGRP-LI, below the lesion the CGRP-LI was reduced. In 3 spinal cords from patients who had survived between 1 and 8 years after injury, CGRP-LI in motoneurons of lumbar spinal cord was absent or considerably diminished. In the spinal cord from one patient who had died several years after injury, there was a unilateral augmentation of CGRP immunostaining. The results suggest that CGRP levels in motoneurons are affected by spinal cord injury in humans and that CGRP levels in motoneurons may be regulated either by supraspinal afferent inputs or by muscle activity.

Role of spinal afferents and calcitonin gene-related peptide in the postoperative gastric ileus in anesthetized rats

OBJECTIVE

The object of this study was to investigate the mechanisms of postoperative gastric ileus in an experimental model of abdominal surgery in anesthetized rats.

SUMMARY BACKGROUND DATA

Sensory neurons partly mediate postoperative gastric ileus. Among other neuropeptides, sensory neurons contain calcitonin gene-related peptide (CGRP) and release CGRP in response to noxious stimulation. Because CGRP inhibits gastric motility, it was hypothesized that abdominal surgery stimulates sensory neurons, which then releases CGRP, thereby inhibiting gastric motility.

METHODS

Postoperative ileus was induced by abdominal surgery. Gastric corpus motility was measured by an intragastric catheter. CGRP action was blocked by CGRP immunoneutralization or by a CGRP receptor antagonist. Spinal sensory neurons were ablated by application of a sensory neurotoxin (capsaicin) to the celiac and superior mesenteric ganglia.

RESULTS

Abdominal surgery decreased gastric corpus motility in the first 5 minutes after abdominal surgery by 59 +/- 5% and by 24 +/- 4% during the 1st postoperative hour. Capsaicin pretreatment of the celiac and superior mesenteric ganglia, CGRP immunoneutralization, or CGRP receptor antagonism reversed the postoperative decrease in gastric corpus motility during the 1st postoperative hour by 50%, 100%, and 59%, respectively.

CONCLUSIONS

These data indicate that spinal sensory neurons and CGRP partly mediate postoperative gastric ileus. CGRP may be released from spinal sensory neuron terminals in the celiac and superior mesenteric ganglia as part of an extraspinal intestinogastric inhibitory reflex activated by abdominal surgery.

Calcitonin gene-related peptide and substance P immunoreactivity in the monkey trigeminal ganglion, an electron microscopic study

Calcitonin gene-related peptide (CGRP) and substance P (SP) immunoreactivity was examined in neurons of the monkey trigeminal ganglion. Moreover, CGRP- and SP-positive varicose nerve fibers were found, occasionally forming pericellular arborizations around trigeminal somata, which, at light microscopic level, suggested the existence of synaptic contacts. Electron microscopic investigation however, revealed that although these varicose fibers ran in close range of somata and were containing accumulations of CGRP- and SP-positive vesicles, classical synaptic contacts were not present.

Sparse substance P-like immunoreactivity in intervertebral discs. Nerve fibers and endings in the rat

I studied rat lumbar intervertebral discs using a monoclonal antibody to substance P, which revealed immunoreactivity in the periosteum and ligaments adjacent to the intervertebral disc. Fibers containing substance P-like immunoreactivity were also found penetrating and terminating within the annulus fibrosus of both the anterior and posterior intervertebral disc. The maximum depth of penetration was 5 lamellae (annular rings) or approximately one sixth of the depth of the annulus. The terminal structures were not encapsulated (free-nerve endings) and were either branched, looped or both. The majority of fibers were varicose in appearance. Substance P-like immunoreactivity was very minor.

Distinct subsets of neuropeptide Y-negative principal neurons receive basket-like innervation from enkephalinergic and gabaergic axons in the superior cervical ganglion of adult rats

The distributions of axons immunoreactive for [Leu]- or [Met]enkephalin and GABA were studied in the superior cervical ganglion of adult rats. The antigens were visualized separately and in combination with neuropeptide Y by the immunoperoxidase technique, using reaction end-products of different colors. Similarities and differences were found in the light-microscopic innervation patterns of enkephalin- and GABA-immunoreactive nerve fibers. Both fiber systems were heterogeneously distributed within the superior cervical ganglion, forming denser networks in its rostral part than elsewhere in the ganglion. The appearance of labeled nerve fibers differed in the two systems. Enkephalin-immunoreactive axons exhibited dotted profiles due to a strong immunoreaction in the axonal varicosities as compared with that in the intervaricose segments, whereas GABA-positive fibers were evenly labeled in both parts of the axons. The most marked difference between the innervation patterns from enkephalin- and GABA-immunoreactive axons was the presence of bundles of varicose axons in conjunction with the basket-like aggregation of enkephalin-immunoreactive nerve terminals. The possibility that enkephalins and GABA are co-localized in certain axons was excluded in double-labeling studies, silver intensification being used for the first antigen and the nickel-enhanced diaminobenzidine reaction for the second antigen. Different subsets of principal neurons were richly innervated in a basket-like manner by axons immunoreactive for enkephalins and GABA. Additionally, combined staining with antisera against either enkephalin and neuropeptide Y or GABA and neuropeptide Y revealed that both subsets of principal neurons richly innervated either by enkephalin-immunoreactive or by GABA-immunoreactive axons were devoid of neuropeptide Y immunoreactivity. Thus, the enkephalinergic and GABAergic axons have different subpopulations of neuropeptide Y-negative principal neurons as targets in the superior cervical ganglion. These results provide further evidence that sympathetic ganglion cells can be classified on the basis of their receiving input from different sources.

Characterization of a calcitonin gene-related peptide (CGRP) receptor on mouse bone marrow cells

Calcitonin gene-related peptide, (CGRP), a vasoactive neuropeptide, is found throughout the peripheral nervous system, and CGRP receptors are present on mature lymphocytes. The current studies describe a CGRP receptor on isolated mouse bone marrow cells. The affinity, distribution and specificity of CGRP receptors were analyzed using radioligand binding assays. [125I]CGRP binding in mouse bone marrow cells was dependent on cell concentration and was stable from 5 to 60 min at room temperature. The average Kd is 3.29 +/- 1.24 nM and the average receptor density is 2796 +/- 365 sites/cell. Competition binding analysis found rat alpha and beta CGRP to be the most inhibitory, (Ki values 0.899 and 0.711 nM, respectively), followed by human alpha CGRP and the antagonist human CGRP8-37. The neuropeptides human and salmon calcitonin did not inhibit [125I]CGRP binding to bone marrow cells. The presence of CGRP receptors on mouse bone marrow cells provides further evidence for a direct role for CGRP in modulating the function and differentiation of cellular components of the immune and inflammatory systems.

Structure, vascularization, and innervation of the mystacial pad of the rat as revealed by the lectin Griffonia simplicifolia

The mystacial pad of the rat is endowed with rows of vibrissal follicle-sinus complexes (F-SCs) that receive a dense and rich variety of innervation, much of which is C fibers. Each F-SC consists of a follicle at the core of a spindle-shaped, encapsulated vascular sinus. Previous studies have shown that the B subunit of the lectin Griffonia simplicifolia (GSA I-B4) binds selectively to a subset of small neurons in the trigeminal ganglion and to a subset of C fibers preferentially distributed to inner lamina II and outer lamina III of nucleus caudalis in the brainstem trigeminal complex in the rat. These laminae are also a major site of termination for afferents in superficial vibrissal nerves (SVNs) that innervate the upper portion of F-SCs. To determine the peripheral distribution of the afferents that bind GSA I-B4, mystacial pads from rats were prepared for fluorescence microscopy with GSA I-B4 conjugated to rhodamine. At the neck of each F-SC, numerous circumferentially oriented bundles of fine-caliber axonal profiles were labeled in the inner conical body, which receives nearly all of its innervation from the SVNs. A sparse, random distribution of fine-caliber profiles from deep vibrissal nerves was labeled at the level of the cavernous sinus in the deep half of the F-SCs. GSA I-B4 also labeled a variety of nonneural structures. By binding to vascular linings, GSA I-B4 revealed a dense, highly organized capillary system within the mesenchymal sheath that forms the inner lining of the vascular sinuses. Thus each F-SC appears to have a closed capillary system within the open vascular sinus. Trabeculae within the lumen of the cavernous sinus were also revealed to span between the sinus capsule and the mesenchymal sheath only about midway along the length of the follicle instead of the entire deeper half, as was previously believed. in addition, GSA I-B4 bound to the surface of follicular cells preferentially in the superficial half of the F-SCs. Sweat glands within the intervibrissal fur and some cells within sebaceous glands in F-SCs were also labeled as well as their ducts. The potential functional implications of these various features are discussed.

Ultrastructural studies on peptides in the dorsal horn of the spinal cord--I. Co-existence of galanin with other peptides in primary afferents in normal rats

The aim of the present study was to investigate galanin-like immunoreactivity in primary afferent terminals and its relationship to other neuropeptides in laminae I and II of the fourth and fifth lumbar segments of normal rat spinal cord using immunofluorescence and pre- and post-embedding electron-microscopic immunocytochemistry. Triple-immunofluorescence staining showed that galanin-like immunoreactivity co-localized with substance P- and calcitonin gene-related peptide-like immunoreactivities in many nerve fibres and terminals in laminae I and II of the dorsal horn. At the ultrastructural level, using pre-embedding immunocytochemistry, galanin-like immunoreactivity was found in type I glomeruli with an electron-dense central terminal containing many densely packed synaptic vesicles and several large dense-core vesicles. Both the cytoplasm and the core of the large vesicles were immunoreactive. In type II glomeruli with an electron-lucent central terminal and loosely packed synaptic vesicles the large dense-core vesicles and the cytoplasm were only weakly galanin-positive. Post-embedding immunocytochemistry revealed that galanin-like immunoreactivity co-existed with substance P- and calcitonin gene-related peptide-like immunoreactivities in many terminals and in individual large dense-core vesicles in lamina II. These terminals were considered to represent primary afferents, since there is evidence that calcitonin gene-related peptide in the dorsal horn only occurs in nerve endings originating in dorsal root ganglia. Evidence was also unexpectedly obtained for the occurrence of several other peptides in calcitonin gene-related peptide-positive terminals, i.e. in presumably primary afferents. Thus galanin-like immunoreactivity sometimes also co-localized with cholecystokinin- and neuropeptide tyrosine-like immunoreactivities in calcitonin gene-related peptide-immunoreactive terminals and in some large dense-core vesicles in such terminals. A small number of calcitonin gene-related peptide immunoreactive, presumably primary afferent terminals contained enkephalin-, neurotensin- (and galanin-)like immunoreactivities. These results indicated that galanin can be co-stored with several other neuropeptides in large dense-core vesicles in primary afferent terminals and may presumably be released together with them in the superficial layer of the dorsal horn. Since various combinations of peptides, presumably at varying concentrations, occur in the large dense-core vesicles in a given nerve ending, it is likely that the individual large dense-core vesicles produced in a neuron are heterogenous with regard to peptide content and thus to the message that they transmit upon release.

Transitory noradrenergic and peptidergic nerves in the cat kidney

Indirect immunohistochemical methods were used to visualize nerves immunoreactive for tyrosine hydroxylase (TH), dopamine beta hydroxylase (DBH), neuropeptide Y, (NPY) and calcitonin gene-related peptide (CGRP) in sections of the kidneys of cats of different ages. Nerve terminals immunoreactive for TH, DBH and NPY innervated interlobar veins and the renal arterial tree including medullary vascular bundles of cats of each age studied. Most nerve terminals immunoreactive for CGRP innervated interlobar arteries. In kidneys of cats 2 to 10 weeks old, TH- and DBH-immunoreactive axons formed elaborate plexuses that were distributed throughout much of the outer two thirds of the inner medulla. Inner medullary NPY-immunoreactive nerve terminals formed sparse plexuses by comparison, thus suggesting a large population of TH-immunoreactive nerve terminals not immunoreactive for NPY. Plexuses immunoreactive for CGRP also innervated the inner medullae of young cats. Some inner medullary axons appeared degenerate in 8 and 10 week old cats, and no inner medullary nerve terminal plexuses were visualized in 12 week old or adult cats. Cell death or paring of axons resulting from mechanisms intrinsic to the neuronal population or from a change in trophic factors secreted or expressed by cells in the medulla may effect the loss of inner medullary nerve terminals in the kidneys of young cats.

Localization of nitric oxide synthase-immunoreactive neurons in the solitary nucleus and ventrolateral medulla oblongata of the rat: their relation to catecholaminergic neurons

The morphological relationship between nitric oxide (NO) and catecholamines in the solitary nucleus (SOL) and ventrolateral medulla oblongata (VLM) was studied by a double immunostaining method with antibodies against NO synthase (NOS), an NO-synthesizing enzyme, and tyrosine hydroxylase (TH), a catecholamine-synthesizing enzyme. Although NOS- and TH-immunoreactive neurons were widely distributed in the SOL and VLM, these immunoreactivities did not coexist in any single neurons. NOS-immunoreactive neurons formed clusters in some restricted regions, i.e. in the medial subnucleus of the SOL, where both NOS- and TH-immunoreactive neurons showed a complementary distribution. These findings suggest that NO-producing neurons constitute a subclass that is distinct from that of catecholaminergic neurons.

Monoaminergic control of the release of calcitonin gene-related peptide- and substance P-like materials from rat spinal cord slices

The possible control by monoamines of the spinal release of substance P- and calcitonin gene-related peptide-like materials (SPLM and CGRPLM, respectively) was investigated in vitro, using slices of the dorsal half of the rat lumbar enlargement superfused with an artificial cerebrospinal fluid. Whereas the spontaneous outflow of SPLM and CGRPLM was changed by none of the agonists/antagonists of monoamine receptors tested, the overflow of both peptide-like materials due to 30 mM K+ was differentially affected by alpha 2-adrenoreceptor and dopamine D-1 receptor ligands. Noradrenaline (10 microM to 0.1 mM) and clonidine (0.1 mM) significantly reduced the K(+)-evoked overflow of SPLM, and both effects could be prevented by idazoxan (10 microM) and prazosin (10 microM) as expected from their mediation through the stimulation of alpha 2B-adrenoreceptors. In contrast, CGRPLM overflow remained unaffected by alpha 2-adrenoreceptor ligands. Dopamine D-1 receptor stimulation by SKF 82958 (10-100 nM) significantly increased the K(+)-evoked overflow of both SPLM and CGRPLM, and this effect could be prevented by the selective D-1 antagonist SCH 39166 (1 microM). Further studies with selective ligands of other monoamine receptors indicated that neither alpha 1- and beta-adrenergic receptors, dopamine D-2, nor serotonin 5-HT1A and 5-HT3 receptors are apparently involved in some control of the spinal release of CGRPLM and SPLM. These data are discussed in line with the postulated presynaptic control by monoamines of primary afferent fibres conveying nociceptive messages within the dorsal horn of the spinal cord.

Immunohistochemical evidence for different pathways immunoreactive to substance P and calcitonin gene-related peptide (CGRP) in the guinea-pig stellate ganglion

The colocalization of immunoreactivities to substance P and calcitonin gene-related peptide (CGRP) in nervous structures and their correlation with other peptidergic structures were studied in the stellate ganglion of the guinea pig by the application of double-labelling immunofluorescence. Three types of fibre were distinguished. (1) Substance P+/CGRP+ fibres, which sometimes displayed additional immunoreactivity for enkephalin, constituted a small fibre population of sensory origin, as deduced from retrograde labelling of substance P+/CGRP+ dorsal root ganglion cells. (2) Substance P+/CGRP- fibres were more frequent; some formed baskets around non-catecholaminergic perikarya that were immunoreactive to vasoactive intestinal polypeptide (VIP). (3) CGRP+/substance P- fibres were most frequent and were mainly distributed among tyrosine hydroxylase (TH)-immunoreactive cell bodies. The peptide content of fibre populations (2) and (3) did not correspond to that of sensory ganglion cells retrogradely labelled by tracer injection into the stellate ganglion. Therefore, these fibres are thought to arise from retrogradely labelled preganglionic sympathetic neurons of the spinal cord, in which transmitter levels may have been too low for immunohistochemical detection of substance P or CGRP. CGRP-immunoreactivity but no substance P-immunolabelling was observed in VIP-immunoreactive postganglionic neurons. Such cell bodies were TH-negative and were spared by substance P-immunolabelled fibre baskets. Retrograde tracing with Fast Blue indicated that the sweat glands in the glabrous skin of the forepaw were the targets of these neurons. The streptavidin-biotin-peroxidase method at the electron-microscope level demonstrated that immunoreactivity to substance P and CGRP was present in dense-cored vesicles of 50-130 nm diameter in varicosities of non-myelinated nerve fibres in the stellate ganglion. No statistically significant difference in size was observed between vesicles immunolabelled for substance P and CGRP. Immunoreactive varicosities formed axodendritic and axosomatic synaptic contacts, and unspecialized appositions to non-reactive neuronal dendrites, somata, and axon terminals. Many varicosities were partly exposed to the interstitial space. The findings provide evidence for different pathways utilizing substance P and/or CGRP in the guinea-pig stellate ganglion.

Development of immunoreactivity for calcitonin gene-related peptide, substance P and glutamate in primary sensory neurons, and for serotonin in the spinal cord of fetal sheep

In this study we have described the ontogeny of immunoreactivity for calcitonin gene-related peptide, substance P and glutamate in primary sensory neurons, and for serotonin in the sacral spin cord, of fetal sheep (n = 37) from 56 to 140 days of gestation (term = 146 days). A few fine, varicose fibres immunoreactive for calcitonin gene-related peptide were present in Lissauer's tract, the dorsolateral funiculus and in laminae I and V in the dorsal horn of the spinal cord at 56-61 days of gestation. At this age, two groups of intensely staining immunoreactive cells were present in the motoneuron pool in laminae VIII and IX in the ventral horn of the spinal cord. By 77 days, immunoreactive fibres were also present in laminae II and X. With advancing gestational age, an increase in the intensity of staining was observed throughout the cord to term, with the exception of laminae VIII and IX, where a decrease was seen. Intense staining of cells in the motoneuron pool was evident until c. 128 days, after which time staining became very faint. Fine fibers immunoreactive for substance P were present in Lissauer's tract and lamina I of the spinal cord at 56-61 days of gestation. They were also present throughout laminae IV-VI and X as well as throughout the entire ventral horn. Immunoreactive fibres in lamina II were evident by 77 days. The staining increased in density but remained similar in distribution with increasing gestational age to term in the dorsal horn, but decreased markedly in the ventral horn. Cells immunoreactive for substance P were evident from 56 days, particularly on the border of laminae II and III, until late in gestation. Ultrastructural studies showed that axon terminals immunoreactive for calcitonin gene-related peptide and for substance P were present in lamina I by 61 days. Immunoreactivity for glutamate was evident at 83 days in dorsal root fibers and also in lamina I and II, where it was more prominent in cells than in fibres. At all ages examined, the dorsal horn stained more intensely than the ventral horn. Immunoreactivity for glutamate and neuropeptides appeared in the cells and fibres of dorsal root ganglia at 97-100 days. In the skin, immunoreactivity for calcitonin gene-related peptide and substance P was present at 85 days, some time after its appearance in the cord. Fibres immunoreactive for serotonin appeared in lamina I, at the neck of the dorsal horn and in the ventral horn at 83 days of gestation.(ABSTRACT TRUNCATED AT 400 WORDS)

Opioid control of the release of calcitonin gene-related peptide-like material from the rat spinal cord in vivo

The possible control by opioids of the spinal release of calcitonin gene-related peptide-like material (CGRPLM) was investigated in halothane-anaesthetized rats whose intrathecal space was perfused with an artificial cerebrospinal fluid. Morphine (20 mg/kg i.v.; or at 10-100 microM added to the perfusing fluid), the mu selective agonist DAGO (10 microM) and the kappa selective agonist U 50488 H (10 microM) did not affect the spontaneous outflow of the CGRPLM. In contrast, the selective delta agonist DTLET (10 microM) significantly increased CGRPLM release. The latter effect could be prevented by the selective delta antagonist naltrindole (10 microM) as expected from the involvement of this class of opioid receptors. However, the addition of naltrindole alone to the perfusing fluid did not modify CGRPLM outflow, indicating that endogenous opioids do not exert a tonic control of CGRP-containing fibers through the stimulation of delta receptors. In contrast, intrathecal perfusion with naloxone (10 microM) or nor-binaltorphimine (10 microM), a selective antagonist of kappa receptors, produced a marked increase in spinal CGRPLM release, suggesting that endogenous opioids acting at mu and kappa receptors, respectively, exert a tonic inhibitory control of CGRP-containing fibers. Indeed, a significant decrease in the spinal release of CGRPLM release could be evoked by the combined addition of U 50488 H (10 microM) plus DAGO (10 microM) to the perfusing medium, indicating that the simultaneous stimulation of both kappa and mu receptors is required for this negative control to occur. This could notably be achieved with morphine (10 microM) in the presence of naltrindole (10 microM) which also produced a significant reduction in the spinal release of CGRPLM. In conclusion, morphine per se did not change CGRPLM release because this drug triggers opposite positive (through the stimulation of delta receptors) and negative (through the concomitant stimulation of both kappa and mu receptors) control mechanisms within the rat spinal cord.

Distribution of substance P and calcitonin gene-related peptide-like immunoreactive nerve fibers in the rat temporomandibular joint

The density and distribution of substance P-like immunoreactive (SP-LI) and calcitonin gene-related peptide-like immunoreactive (CGRP-LI) nerve fibers in rat temporomandibular joint (TMJ) were investigated in whole-mount preparations and frozen sections by immunohistochemistry with the avidin-biotin-peroxidase complex method. Both types of immunoreactive nerves were observed primarily in the joint capsule, the peripheral articular disc, the synovial membrane, and the periosteum. The distribution of CGRP-LI nerves was similar to that of SP-LI nerves. The anterior portion of the joint capsule and disc was most densely innervated, followed by the posterior, lateral, and medial portions. In addition, CGRP-LI nerves were more numerous and more dense in immuno-intensity than SP-LI nerves. In the synovial membrane, many SP- and CGRP-LI nerves terminated in the subsynovial layer, but some branches extended into the superficial synovial lining layer close to the joint cavity. Immunolabeled nerves were prominently located in the disc attachment and peripheral portion of the disc, and occasional nerves were located in the dense collagenous disc band as an actual disc. However, no fibers were detected in the central disc band. Thus, most of the disc was not innervated by any nerves. The present study provides a morphological basis for the possible roles of neuropeptides in endocytosis by synoviocytes, regulation of blood flow in the synovial membrane, nociception mechanisms of the TMJ, and modulation of the inflammatory response in the TMJ.

Release of calcitonin gene-related peptide (CGRP), substance P (SP), and vasoactive intestinal polypeptide (VIP) from rat spinal cord: modulation by alpha 2 agonists

Release of calcitonin gene-related peptide (CGRP) and substance P (SP) from the rat lumbar dorsal spinal cord and vasoactive intestinal polypeptide (VIP) from the sacral spinal cord was examined under resting conditions (baseline release) and in the presence of capsaicin (CAP). Baseline rates of CGRP, SP, and VIP release were 1.71 +/- 0.19, 0.12 +/- 0.01, and 0.097 +/- 0.029 pg/mg/min, respectively. The addition of CAP (10 microM) to the perfusate had no effect upon resting VIP release, but elevated CGRP and SP release significantly by 11.1 +/- 0.8 and 0.19 +/- 0.03 pg/mg/min over baseline release rate, respectively. Addition of dexmedetomidine (10 microM), an alpha 2-adrenergic agonist, did not change the baseline release of either CGRP or SP, but significantly decreased the CAP-evoked release of both peptides. The attenuation of the CAP-evoked release by the agonists was antagonized by the concurrent administration of yohimbine (10 microM) or atipamezole (10 microM), but not by prazosin. ST-91 (10 microM) did not alter the release of CGRP but decreased the CAP-evoked release of SP. This inhibition was antagonized by yohimbine and prazosin, but not by atipamezole. These data suggest that the afferent-evoked release of SP and CGRP from CAP-sensitive terminals (presumably those associated with small primary afferents) is modulated by local alpha 2 receptors. The common sensitivity of the agonists to yohimbine and the differential effects of atipamezole and prazosin are consistent with the hypothesis that dexmedetomidine and ST-91 may interact with different subpopulations of spinal alpha 2 receptors, both of which may modulate afferent terminal release.(ABSTRACT TRUNCATED AT 250 WORDS)

Neuropeptides in the human celiac/superior mesenteric ganglionic complex: an immunohistochemical study

The occurrence of vasoactive intestinal polypeptide (VIP), peptide histidine-isoleucine (PHI), calcitonin gene-related peptide (CGRP), substance P (SP), somatostatin (SOM), galanin (GAL) and enkephalins (ENK) is studied in the human celiac/superior mesenteric ganglionic complex of pre- and full-term newborns, and adult subjects by means of immunohistochemistry. The antisera used labelled nerve fibres and terminal-like networks for each examined peptide, as well as VIP- and SOM-positive postganglionic neurons. Differences in the relative amount and density of the structures immunoreactive to the various peptides were observed. Moreover, variations in the amount and type of labelled elements were appreciable for each peptide when specimens from subjects at perinatal and adult ages were compared. Double-labelling immunofluorescence for SP and each other peptide showed that co-localization with SP is very frequent for CGRP, moderate to scarce for GAL and SOM, and rare to absent for PHI, VIP and ENK. VIP-, ENK- and CGRP-immunolabeled perikarya bearing the morphological features of the small intensely fluorescent (SIF) cells occurred in the organ. The presence of a paraganglion in one of the specimens examined allowed the detection of VIP- and ENK-positive cell bodies and VIP-, ENK-, SP- and GAL-like immunoreactive varicose nerve fibres in it. The results obtained provide substantial morphological data in support of the involvement of the examined peptides in the chemical interneuronal signalling in the human celiac/superior mesenteric ganglia.

Effects of calcitonin gene-related peptide on the rabbit electroretinogram

In order to better understand the role of Calcitonin gene-related peptide (CGRP) in mammalian retina, the dose related effects of human CGRP (hCGRP) on rabbit electroretinogram (ERG) were examined in the present study. CGRP was administered intraocularly in doses of 0.1, 1.0 and 10.0 micrograms. ERG A- and B-wave as well as oscillatory potentials (P1, P2, P3 and P4) were recorded. The highest dose of CGRP (10.0 micrograms) significantly increased the amplitudes of the A-wave and OP components (P1, P2, P3 and P4) produced by relatively high stimulus intensity. The same dose of the peptide also enhanced B-wave amplitude at all intensities studied. The effects of the intermediate dose of CGRP (1.0 microgram) on the B-wave amplitudes were dependent on stimulus intensities. B-wave amplitudes at high stimulus intensities were not affected by 1.0 microgram of CGRP but were significantly increased with relatively lower stimulus intensities. The amplitudes of P3, one of OP components, were significantly increased. However, amplitudes of A-wave and other OP components (P1, P2 and P4) were not affected by 1.0 microgram CGRP. The lowest dose of the peptide (0.1 microgram) did not affect any amplitudes of ERG components. Implicit times of A-wave, B-wave and OP components were not significantly affected by the different doses of CGRP. Taken together, these results indicate that CGRP may play a functional role in modulating retinal responses to photic stimulation.

Neural and non-neural origin of calcitonin gene-related peptide (CGRP) in the gastric mucosa

We have used immunohistochemistry and in situ hybridization histochemistry to visualize CGRP and the mRNA encoding the CGRP precursor in the stomach. CGRP is present in nerve fibers in the mucosa. CGRP mRNA and CGRP itself are also found in non-neural cells in the lamina propria. These cells are likely to be macrophages or B-lymphocytes.

Mutual modification of vasoactivity by calcitonin gene-related peptide and endothelin-1 in isolated porcine ophthalmic artery

Vasodilation has been implicated in the pathophysiology of some headaches, but the mechanisms behind such abnormalities remain unknown. Calcitonin gene related peptide (CGRP), a peptide present in sensory trigeminal fibres, induces strong and long lasting vasodilation in cranial vessels, and has been found to be increased in jugular blood during migraine attacks. Endothelin (ET) is a recently identified potent vasoconstrictor peptide, which also induces long-lasting responses. ET-CGRP interactions may be of importance in vascular beds putatively involved in pain development in the head, and were therefore studied in isolated porcine ophthalmic arteries. Both peptides were found to induce strong and long-lasting reactions in this artery. CGRP decreased ET-induced contractions and ET decreased CGRP-induced relaxations. These effects were additive rather than synergistic.

Trigeminal ganglion neurons which project by way of axon collaterals to both the caudal spinal trigeminal and the principal sensory trigeminal nuclei

Employing a combination of fluorescent retrograde double labeling and immunofluorescence histochemistry, we found that some single neurons in the trigeminal ganglion of the rat projected by way of axon collaterals both to the caudal spinal trigeminal nucleus and to the principal sensory trigeminal nucleus, and that about 40% or 57% of these neurons showed respectively substance P- or calcitonin gene-related peptide-like immunoreactivity.

Normal development and effects of neonatal infraorbital nerve damage upon the innervation of the trigeminal brainstem complex by primary afferent fibers containing calcitonin gene-related peptide

Immunocytochemistry was used to study the normal development and response to infraorbital nerve (ION) damage of the innervation of the trigeminal (V) brainstem complex by axons recognized by an antibody directed against calcitonin gene-related peptide (CGRP). CGRP-like immunoreactivity (CGRPLI) was present in axons that occupied the outer V spinal tract (TrV) at all levels of the V brainstem complex. Almost no fibers terminated within V nucleus principalis (PrV), but there was dense CGRPLI in the supratrigeminal nucleus. There was also very little CGRPLI within rostral V subnucleus oralis (SpO). However, in the caudal one-half of the nucleus, a dense elongated patch of immunoreactivity was consistently present just medial to TrV. Only occasional CGRP-positive axons could be seen within V subnucleus interpolaris (SpI), but the paratrigeminal nucleus contained dense immunoreactivity. Trigeminal subnucleus caudalis (SpC) also contained CGRPLI that was very dense in lamina I and the outer portion of lamina II. Scattered terminals were also present in layers III and IV and dense terminal clusters were in lamina V. CGRP-immunoreactive neurons were present in the V ganglion by embryonic (E-) day 16 and immunoreactive axons could be seen in the V brainstem complex on E-17. At birth, CGRP-positive axons in the V brainstem complex had achieved a distribution very similar to that in adult rats. The major difference between the patterns of labelling in neonates and adults was the presence of relatively large numbers of CGRP-positive fibers in ventral PrV and SpO of the former animals. The disappearance of these fibers was completed by the middle of the third postnatal week. Transection of the ION on the day of birth had little effect upon CGRP in SpO, SpI, and SpC, but it did result in an increase in CGRP-positive fibers in PrV ipsilateral to the damaged nerve. When considered together with previous findings, these results suggest that CGRP-positive axons express this peptide well after they have entered the V brainstem complex and that the central terminal field of these fibers is not substantially altered by a manipulation which results in the death of nearly 60% of all V primary afferent neurons.

Distribution of calcitonin gene-related peptide in rat and rabbit spinal cords: effect of intrathecal 5,7-dihydroxytryptamine

Calcitonin gene-related peptide-like immunoreactivity (CGRP-LI) was measured in selected regions of the cervical, thoracic, and lumbar spinal cord of untreated rabbits and, following intrathecal injection of the serotonergic neurotoxin 5,7-dihydroxytryptamine (5,7-DHT), in the thoracolumbar cord in rats using a sheep antiserum raised against tyrosine0 calcitonin gene-related peptide28-37. In the cervical, thoracic, and lumbar segments of the rabbit spinal cord, CGRP-LI levels were 15-50-fold higher in the dorsal than in the ventral grey region in the same segment. The only segmental variation in CGRP-LI levels was in the dorsal white region, where levels in the thoracic cord were lower than those in cervical or lumbar segments. Within individual spinal segments, the pattern of distribution of CGRP-LI in the rabbit spinal cord was analogous to that in other species previously examined, including rat, human, and cat spinal cord. Intrathecal injection of 5,7-DHT, which caused 85-91% depletion of 5-hydroxytryptamine and 5-hydroxyindoleacetic acid from the thoracolumbar ventral spinal cord, did not affect choline acetyltransferase activity, which is colocalized with CGRP in motoneurones in this spinal cord region. In contrast, intrathecal 5,7-DHT produced a threefold increase in CGRP-LI in the ventral thoracolumbar cord, suggesting that spinal motoneurones selectively increase production of CGRP 10 days after neurotoxin-induced denervation of bulbospinal raphe neuronal input.

In vivo release of calcitonin gene-related peptide-like material from the cervicotrigeminal area in the rat. Effects of electrical and noxious stimulations of the muzzle

The continuous perfusion with an artificial cerebrospinal fluid of the cervicotrigeminal area of the spinal cord in halothane-anaesthetized rats allowed the collection of calcitonin gene-related peptide-like material with the same immunological and chromatographic characteristics as authentic rat alpha-calcitonin gene-related peptide. The spinal release of calcitonin gene-related peptide-like material could be significantly increased by the local application of 60 mM K+ (approximately +100%), high-intensity percutaneous electrical stimulation (approximately +200%) and noxious heat (by immersion in water at 52 degrees C; approximately +150%) applied to the muzzle. By contrast, noxious mechanical (pinches) and chemical (subcutaneous formalin injection) stimulations and deep cooling (by immersion in water at 0 degrees C) of the muzzle did not alter the spinal release of calcitonin gene-related peptide-like material. In addition, low-intensity electrical stimulation, recruiting only the A alpha/beta primary afferent fibres, significantly reduced (approximately -30%) the release of calcitonin gene-related peptide-like material from the cervicotrigeminal area. These data suggest that among the various types of natural noxious stimuli, noxious heat may selectively excite calcitonin gene-related peptide-containing A delta and C primary afferent fibres projecting within the dorsal horn of the spinal cord, and that activation of A alpha/beta fibres reduces spontaneous calcitonin gene-related peptide-like material release possibly through an inhibitory presynaptic control of calcitonin gene-related peptide-containing A delta/C fibres.

Distribution and origin of extrinsic nerve fibers containing calcitonin gene-related peptide, substance P and galanin in the rat upper rectum

The distributions of nerve fibers containing calcitonin gene-related peptide (CGRP), substance P (SP) and galanin (GAL) were examined in the rat rectum of mutants rats, aganglionic rats (AGRs), which completely lack the intramural nerve cells in the large intestine, and of their normal littermates. The origin of extrinsic peptide-containing nerve fibers was examined using retrograde tracing combined with immunohistochemistry in normal rats. In the rectum of normal rats, CGRP-, SP- and GAL-immunoreactive varicose fibers were observed throughout all layers of the rectal wall, and immunoreactive nerve cells were present in the enteric ganglia of colchicine-treated rats. In the aganglionic rectum of AGR, a rich supply of CGRP-immunoreactive fibers was observed in the mucosa, around the blood vessels, and in the submucous and intermuscular spaces. SP- and GAL-immunoreactive fibers in the aganglionic rectum showed a similar distribution to CGRP-immunoreactive fibers but were less dense. These results suggest that most of CGRP-positive fibers in the rectum are extrinsic whereas a large part of SP- or GAL-positive fibers are intrinsic. Fluoro-gold injected into the upper rectum of normal rat labelled nerve cells (less than 10% of total ganglion cells) in the lumbar (L1 and L2) and lumbosacral (L6 and S1) dorsal root ganglia. More than half of nerve cells in the dorsal root ganglia (L6 and S1) projecting to the rectum were immunoreactive for CGRP, and less than 10% were immunoreactive for SP or GAL. Comparison of serial sections of the dorsal root ganglion revealed that about half of the CGRP-immunoreactive cells were also positive for SP or GAL. These results indicate that SP- or GAL-positive neurons projecting to the rectum are scarce in the dorsal root ganglia. The present investigation suggests that CGRP-containing nerves are visceral afferents forming a major component of the sensory innervation of the rat rectum, and SP- and GAL-containing nerves which share their extrinsic origins appear to form a lesser proportion of the sensory innervation.

Immunohistochemical localization of calcitonin gene-related peptide and cotransmitters in a subpopulation of post-ganglionic neurons in the porcine inferior mesenteric ganglion

Applying double-fluorescence immunohistochemistry, adrenergic and non-adrenergic postganglionic sympathetic neurons, in the porcine inferior mesenteric ganglion (IMG) are subdivided according to size and cotransmitter content. Calcitonin gene related peptide (CGRP)-immunoreactive (IR) neurons are demonstrated to belong to the non-adrenergic, i.e. tyrosine hydroxylase- and DOPAmine-beta-hydroxylase-(D beta H)-negative subpopulation of postganglionic perikarya. Virtually all of the CGRP-IR postganglionic neurons exhibit colocalization with somatostatin (SOM), and, some of them with neuropeptide tyrosine (NPY). Additionally, NPY-, SOM-, and NPY/SOM-IR subpopulations of adrenergic and non-adrenergic neurons are observed. CGRP-immunoreactivity is seen in dense networks of intraganglionic varicose nerve fibres, adjacent to the TH- and SOM-IR neurons. NPY-IR perikarya are sparsely supplied by CGRP-IR fibres. SOM- and NPY-IR nerve fibres also exist in the inferior mesenteric ganglion. The functional relevance of CGRP-IR postganglionic neurons, as well as target organs of these neurons remain to be elucidated.

Development of calcitonin-gene-related peptide, chromogranin A, and synaptic vesicle markers in rat motor endplates, studied using immunofluorescence and confocal laser scanning

The presence of calcitonin-gene-related peptide (CGRP) and chromogranin A was investigated in the developing rat (E18-adult) motor system, using immunofluorescence and confocal laser scanning, and compared with synaptic vesicle markers, synaptophysin and synapsin I. In lumbar motor perikarya CGRP-LI and Chr A-LI were present in high intensities in E18 and P1 perikarya in the anterior horn. With increasing age immunoreactivity decreased. Chr A-LI was sparse in the adult. In peroneal endplates, p38-LI and SYN I-LI were present in all stages, including E18. Peptide-LI was very weak or absent in early stages (E18 and P1), but abundant in P8 and P18, especially CGRP-LI, and decreased again in P32 and adult animals. These observations indicate that the peptides have precise functions during certain developmental stages, possibly related to synapse maturation, receptor concentration, and reduction of supernumerary endplates. Both peptides are rapidly transported anterogradely in adult motor axons, and may serve physiological functions also in the adult.

Effect of capsaicin and resiniferatoxin on peptidergic neurons in cultured dorsal root ganglion

The neurotoxic effect of capsaicin has been shown to be selective on a subpopulation of small dorsal root ganglion neurons in newborn animals. The aim of this study was to provide evidence of the long lasting effect of capsaicin and its ultrapotent analog resiniferatoxin (RTX) on sensory peptidergic neurons maintained in organotypic cultures. The effects of the two irritants were examined on neurons that contained substance P (SP) and calcitonin gene-related peptide (CGRP). Exposure of the cultures to 10 microM capsaicin and 100 nM RTX for periods of 2 days or longer resulted in almost complete elimination of SP-immunoreactive (IR) neurites and reduction, but not elimination, of CGRP-IR neurites. In addition, both 10 microM capsaicin and 100 nM RTX significantly reduced the number of SP- and CGRP-IR cell bodies within DRG explants. Capsaicin in 100 microM concentration produced complete elimination of SP-IR fibers and a greater decrease in the number of CGRP-IR fibers, but failed to completely eliminate IR cell bodies. Exposure of the cultures to the irritants in the same concentrations for 90 min did not produce a measurable effect on SP- or CGRP-IR in neurites or cell bodies. It is important to establish that the effect of capsaicin and RTX on cultured neurons was of long duration (longer than 4 days) and is therefore different from depletion of peptides. These findings demonstrate that processes of cultured sensory neurons are much more sensitive to capsaicin and RTX than cell bodies. Furthermore, our results show that SP-IR neuronal elements are more sensitive to capsaicin than CGRP-IR elements. These data suggest that cultured sensory neurons express the functional properties of differentiated sensory neurons in vivo.

Studies on the distribution of calcitonin gene-related peptide-like and substance P-like immunoreactivities in rat hind limb muscles

The tibialis anterior, extensor digitorum longus and soleus muscles in the rat were examined with respect to the presence of calcitonin gene-related peptide-like as well as substance P-like immunoreactivity. In some of the motor endplates in these muscles, identified by staining for acetylcholinesterase activity, calcitonin gene-related peptide-like immunoreactivity was detected, but in others it was not. Calcitonin gene-related peptide-like immunoreactivity was found to coexist with substance-P-like immunoreactivity in nerve fibres located outside and inside the capsule of the muscle spindles, as well as in nerve fibres located in nerve fascicles. These fibres presumably represent sensory nerve fibres. Calcitonin gene-related peptide-like immunoreactivity, but not substance P-like immunoreactivity, was also detected in cap-like structures located on the surface of the intrafusal muscle fibres in the polar regions of the spindles, structures which are likely to correspond to motor plate endings. The observations suggest that calcitonin gene-related peptide is heterogeneously present in the endplates of rat hind limb muscles, and gives for the first time immunohistochemical evidence for the presence of calcitonin gene-related peptide and substance P in the innervation of muscle spindles.

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.

Guanethidine sympathectomy of mature rats leads to increases in calcitonin gene-related peptide and vasoactive intestinal polypeptide-containing nerves

Changes in the innervation of the heart (right atrium), mesenteric blood vessels, vas deferens and superior cervical ganglia have been examined following long-term sympathectomy of the mature rat. Patterns of innervation were investigated by histochemical and immunohistochemical techniques, while levels of noradrenaline and neuropeptides were measured by neurochemical assays. Large doses of guanethidine (80 mg/kg) were given daily for four weeks to 12-14 week-old male rats which were killed at 18-20 weeks of age. Catecholamine-containing nerves were severely depleted or absent in all tissues, together with a reduction in noradrenaline content. Neuropeptide Y levels were depleted by 97% in vas deferens, 78% in mesenteric vein and 50% in right atrium and superior cervical ganglion. Increases in levels of calcitonin gene-related peptide were seen in the mesenteric vein (up seven-fold), superior cervical ganglia (up 11-fold) and vas deferens (prostatic portion up three-fold), which were also evident by assessment of immunolabelling of nerve fibres. Calcitonin gene-related peptide levels were not increased in the right atrium. In addition, an increase in vasoactive intestinal polypeptide-immunoreactive nerve fibre density was seen in the mesenteric artery and vas deferens, although no significant differences were observed in assays of vasoactive intestinal peptide levels in any tissue. No changes were seen in the innervation of any of the tissues by substance P-immunoreactive nerve fibres either by immunohistochemical or immunochemical assay assessment. This study indicates that there are selective changes in the mature nervous system in response to the loss of sympathetic nerves. Differences between these changes and the response of the developing nervous system to long-term sympathectomy are discussed.

Vasoactive intestinal polypeptide and acetylcholine coexist with neuropeptide Y, dopamine-?-hydroxylase, tyrosine hydroxylase, substance P or calcitonin gene-related peptide in neuronal subpopulations in cranial parasympathetic ganglia of rat

Immunohistochemistry has been used to demonstrate that neuropeptide Y, dopamine-beta-hydroxylase, calcitonin gene-related peptide or substance P are colocalized with vasoactive intestinal polypeptide and choline acetyltransferase in subpopulations of neurons in cranial parasympathetic ganglia of rat. These comprise the ciliary, sphenopalatine, otic, glossopharyngeal-vagal and internal carotid ganglia. In the ciliary and glossopharyngeal-vagal ganglia tyrosine hydroxylase is also found in such neurons. The findings emphasize that the combined localization of dopamine-beta-hydroxylase and neuropeptide Y or the presence of tyrosine hydroxylase is not exclusively a marker for peripheral adrenergic neurons. Further, the co-localization of calcitonin gene-related peptide and substance P is not a decisive indication that a neuron is sensory in nature. It is discussed whether the presence of the enzymes and peptides other than vasoactive intestinal polypeptide is a remnant of a different expression during ontogenesis or indicates target-specific functions in the adult.

Neuropeptides in the human superior cervical ganglion

Superior cervical ganglia from 7 human cadavers (3-7 h post mortem) were immunostained for tyrosine hydroxylase (TH), dopamine-beta-hydroxylase (DBH) and 14 different neuropeptides. The results show that ganglionic cells contain TH, DBH, neuropeptide Y (NPY), somatostatin, vasoactive intestinal polypeptide (VIP) and calcitonin gene-related peptide (CGRP). These substances were present predominantly within large ganglionic cells. Inside the ganglion, the number and topographical distribution of various types of immunoreactive cells differed from one another. NPY and CGRP immunoreactivities were found in some TH-positive cells, but that co-localization never exceeded the 30% of the TH cells. Leu-enkephalin showed a weak immunoreactivity, which was restricted to fibers or varicosities. Neuropeptides like substance P, dynorphin A and B, cholecystokinin, galanin, corticotropin-releasing factor, thyrotropin-releasing hormone, angiotensin II and neurotensin showed no immunoreactivity in the human superior cervical ganglion.

Immunohistochemical observations on spinal tissue innervation. A review of hypothetical mechanisms of back pain

Immunohistochemical studies support earlier reports of a rich nerve supply to the posterior longitudinal ligament, a less developed innervation of the anterior ligament and the outermost annular ring, and a total lack of innervation in deeper parts of the intervertebral disc. Whether this pattern of innervation is altered when the disc becomes severely degenerated is presently uncertain. Recent studies have also revealed neuropeptide-immunoreactive nerves in the outermost parts of the annulus and adjacent peridiscal ligaments. These nerves are probably involved in discogenic back pain, and may become sensitized when disc tissue is injured. This sensitization appears to be coupled to an alteration of neuropeptide pools in the nearby dorsal root ganglion, the important site of neuropeptide production. Direct influences on the dorsal root ganglion, mechanical and/or chemical, may also be important, and may be involved in spinal segment degeneration.

Calcitonin and calcitonin gene-related peptide immunoreactivity and colocalization in newborn cat lung

Calcitonin (CT) and calcitonin gene-related peptide (CGRP) are generated by alternate RNA processing from alpha and beta CT/CGRP genes. In this report, an immunocytochemical investigation was undertaken on the occurrence and distribution of immunoreactive CT as well as its colocalization with CGRP in newborn cat bronchopulmonary endocrine cells. A widespread distribution of solitary endocrine cells and neuroepithelial bodies immunostained for CT was recorded within the lung. In all animals studied, CT immunoreactivity represents a subpopulation of CGRP positive cells, while the intrapulmonary nerve fibers contain only CGRP. To the best of our knowledge, this is the first time that CT and its colocalization with CGRP have been demonstrated immunocytochemically in the cat lung. Our results indicate, that different molecular processing of both CT/CGRP genes may be represented by different patterns in the cellular immunoreactivity of the synthetized peptides.

NF-L and peripherin immunoreactivities define distinct classes of rat sensory ganglion cells

Double immunofluorescence studies using antibodies against NF-L and peripherin revealed three distinct subpopulations of neurons in rat dorsal root ganglia (DRG). In the adult rat, 46% of the DRG neurons were small and peripherin-positive (NF-L-negative), and 48% were large and NF-L-positive (peripherin-negative). About 6% were both peripherin- and NF-L-positive. All of the DRG neurons reacted with antibodies to NF-M and nonphosphorylation-dependent or phosphorylation-independent antibodies to NF-H. The neuropeptides were predominantly found in the peripherin-positive small cell population. Eighty-seven percent of the peripherin-positive small cell population contained substance P immunoreactivity, while 43% of this cell population contained CGRP. In contrast, only 18-24% of the NF-L-positive large-cell population contained neuropeptides, and these were primarily in a smaller sized subpopulation. Similar patterns of antigen representation were observed in neonatal (PN2) DRG cell populations. Tissue cultures of sensory ganglion cells from PN2 DRG, in serum-free medium, stably maintained exclusively peripherin-positive neurons, with about 5% of these containing coexistent NF-L immunoreactivity. Very high levels of neuropeptide gene expression were exhibited by these postnatal neurons in culture.

A quantitative study of neuropeptide immunoreactive cell bodies of primary afferent sensory neurons following rat sciatic nerve peripheral axotomy

Following peripheral axotomy, fluoride resistant acid phosphatase (FRAP) and most neuropeptides are depleted in the central terminals of axotomised nerves and reduced in their corresponding cell bodies (DRG) but vasoactive intestinal polypeptide (VIP) increases. The increase in VIP probably results from a change in gene expression in other ganglion cells which do not normally express VIP. A quantitative study was performed to investigate the proportion of DRG cells immunoreactive for different peptides at increasing times after sciatic nerve section. Retrograde fluorescent neuronal labelling of sciatic nerve cell bodies by injection of fast blue into the proximal stump was combined with unlabelled antibody immunohistochemistry for CGRP and VIP. The proportion of cells immunoreactive for these peptides was quantified between two and fourteen days post-axotomy. The number of VIP immunoreactive profiles increased significantly in the first 4 days post-axotomy, followed by a slight decrease before rising again. In contrast, the number of and CGRP-immunoreactive cell profiles declined to zero by 14 days post-axotomy. 4 days post-axotomy 50% of VIP positive cells were also immunoreactive for CGRP. There was neither colocalisation between VIP and FRAP nor between CGRP and FRAP. It is concluded that many peptidergic DRG cell bodies switch their expression of peptide to VIP after injury, whereas non-peptide-containing subpopulations do not.

Distribution of axons showing calcitonin gene-related peptide- and/or substance P-like immunoreactivity in the sensory trigeminal nuclei of the cat

Distribution of axons with calcitonin gene-related peptide (CGRP)-like and/or substance P (SP)-like immunoreactivity (LI) within the sensory trigeminal nuclei was examined in the cat before and after trigeminal rhizotomy. Axons with CGRP-LI or SP-LI were seen throughout the principal sensory trigeminal nucleus (Vp) and spinal trigeminal nuclei, including the medullary dorsal horn (MDH). They were densely distributed particularly in the dorsolateral part of the dorsal subnucleus of the Vp, ventromedial marginal zone of the ventral subnucleus of the Vp, dorsomedial and ventromedial parts of the oral spinal trigeminal nucleus, ventromedial and lateral marginal zones of the interpolar spinal trigeminal nucleus, and lamina I, outer part of lamina II and lamina V of the MDH. Most of the CGRP-LI axons exhibited SP-LI, while many SP-LI axons did not show CGRP-LI. After trigeminal rhizotomy, almost all CGRP-LI axons disappeared from the ipsilateral sensory trigeminal nuclei, while a considerable number of SP-LI axons remained intact throughout the nuclei; these SP-LI axons did not show CGRP-LI. The results indicate that CGRP-LI axons within the sensory trigeminal nuclei exhibit SP-LI and are of peripheral origin, and that SP-LI axons without CGRP-LI are of central origin.

Increases in NPY in non-sympathetic nerve fibres supplying rat mesenteric vessels after immunosympathectomy

The effect of nerve growth factor (NGF) deprivation on developing peripheral peptide-containing nerves has been examined in Wistar rats. Animals were treated from birth for 7 days with antibodies to NGF (10 microliters/g body weight) and killed at 4 or 8 weeks of age. The nerves of the mesenteric and femoral blood vessels, vas deferns and bladder were viewed with histochemical and immunohistochemical techniques. The effectiveness of anti-NGF treatment was monitored by viewing catecholamine (CA)-containing nerves, which were virtually absent from the blood vessels, but were little affected in the vas deferens and bladder in both age groups. Immunoreactivity for substance P and calcitonin gene-related peptide was slightly reduced in the blood vessels. Immunoreactivity for neuropeptide Y (NPY) was reduced in the femoral blood vessels by 88% at both ages, but reductions in NPY immunoreactivity (NPY-IR) in the mesenteric vessels varied with age. In the mesenteric artery at 4 weeks, NPY-IR was reduced by 96% from control values, but at 8 weeks it was reduced by only 37%. Acute sympathectomy with 6-OHDA treatment reduced NPY-IR in the mesenteric artery by 98% at 4 weeks and 93% at 8 weeks. It is proposed that the increase in NPY-IR but not CA-containing nerves in the mesenteric artery between 4 and 8 weeks after immunosympathectomy is due to compensatory innervation from a non-sympathetic source (probably enteric neurons) that is available to mesenteric, but not to femoral blood vessels.

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.

Immunohistochemical analysis of the ontogeny of calcitonin gene-related peptide-like immunoreactivity in the rat central nervous system

The ontogeny of calcitonin gene-related peptide-like immunoreactivity (CGRP-LI) in the rat central nervous system was examined using the indirect immunofluorescence technique. Caudally located neurons displayed CGRP-LI relatively early in development. For instance, CGRP-immunoreactive (CGRP-IR) cells were first visualized in the hypoglossal nucleus and dorsal nucleus of the lateral lemniscus at day 19 of gestation, while by day 1 postnatal the facial and ambiguus nuclei possessed their full complement of immunoreactive neurons relative to that observed in the adult. By contrast, CGRP-IR somata in more rostral regions such as the lateral septal nucleus were not visualized until much later in development, i.e. day 12 postnatal. By day 15 postnatal, however, CGRP-LI was at a maximum in almost all areas scrutinized. This pattern of immunostaining persisted up to the oldest age studied (day 28 postnatal), except in the lateral septal and parabrachial nuclei, along the dorsal border of the medial lemniscus, and in the inferior olive, where many of the previously immunopositive cells could no longer be detected. In summary, CGRP-IR somata in the rat central nervous system appear in a principally caudal to rostal direction, beginning in late gestation. In some regions, CGRP is present only ephemerally. The ontogeny of CGRP during maturation of the rat brain is consistent with its suggested neurotrophic and neurotransmitter roles.

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.

Regulation of calcitonin gene-related peptide mRNA expression in the hearts of spontaneously hypertensive rats by testosterone

Previous studies have demonstrated the existence of calcitonin gene-related peptide (CGRP)-immunoreactive nerve fibres and nerve cell bodies in the rat heart. Using polymerase chain reaction we have investigated whether CGRP messenger RNA (mRNA) could be detected in heart tissue of spontaneously hypertensive rats, and whether CGRP-mRNA levels are affected by gonadectomy and testosterone substitution. Two weeks after castration CGRP-mRNA levels decreased to 65.2 +/- 6.4% of control values, whereas daily dihydrotestosterone substitution reversed this effect (88.0 +/- 1.2% of control). Our results indicate that steroid hormones control the expression of intracardiac CGRP on a pretranslational level.

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.