Substance P-containing sensory nerves in the rat iris. Normal distribution, ontogeny and innervation of intraocular iris grafts

Trigeminal, substance P-containing nerves have been studied in the stretch-prepared rat iris with immunohistochemical techniques. The normal iris exhibited a slightly irregular plexus of individual fibres in the dilator, intermingled with thin, meandering axon bundles. The sphincter contained more circumferentially oriented fibres. Occasional free nerve endings were present in all parts of the iris; no obvious association with blood vessels was detected. All substance P-positive nerves in the iris disappeared after lesioning the trigeminal nerve. Irides of neonates showed scattered, smooth fibres in a sparse plexus, without visible axon bundles. Over the first two postnatal weeks, the density of innervation developed rapidly, reaching a transiently supranormal level and fluorescence intensity, compared to adulthood. From 3 weeks on, the pattern and density of substance P-containing fibres approached the normal adult appearance. In irides grafted to the anterior eye chamber, the intrinsic substance P nerves degenerated, disappearing completely after 5 days. Reinnervation from the host irides transpired over the next few weeks, approximating normal density after 3 weeks, and organotypic density and distribution from 4 weeks on. No obvious hyperinnervation was encountered after longer postoperative times (3 months). In the host iris, many substance P fibres disappear or exhibit low fluorescence intensity during the first postoperative week, recovering fully during the next 2 weeks. Over longer postoperative periods irregular, moderate hyperinnervation developed with increased numbers of axons in bundles. In conclusion, we show normal distribution and plasticity during ontogeny and maturity of substance P-containing iris nerves in the rat, with a sensitive immunohistochemical technique in iris whole mounts.     

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)     

Innervation of rabbit fetal lungs

Nerve fibers, autonomic ganglia, and neuroepithelial bodies of the lungs of rabbit fetuses, 17 to 31 days gestational age, were studied with neurohistological techniques including silver impregnation, acetylcholinesterase histochemistry, and glyoxylic-1acid-induced histofluorescence for monoamines. The silver impregnation method showed that nerve fibers and ganglia accompanied the bronchi and large pulmonary blood vessels to enter the developing lungs by the 17th day of gestation. Cholinergic and adrenergic nerves began to appear in the walls of the bronchi on the 21st day. The developing pulmonary arteries had accompanying adrenergic nerves on the 25th day. Acetylcholinesterase-positive parasympathetic ganglia were seen on the 27th day. Silver-impregnated nerve fibers in the developing alveolar walls and pleura were found on the 25th day. Neuroepithelial bodies and specialized single cells which were argyrophilic, acetylcholinesterase-positive, and fluorescent could be demonstrated in 19–21-day-old and older fetuses; and some of these structures were innervated by sensory and autonomic motor fibers. These observations indicated that nervous tissue and neuroepithelial bodies appeared in the lungs during the glandular stage of the lung development and that differentiation of adrenergic and cholinergic nerves began in the late glandular stage.     

Developmental pattern and distribution of nerve growth factor low-affinity receptor immunoreactivity in human spinal cord and dorsal root ganglia: comparison with synaptophysin, neurofilament and neuropeptide immunoreactivities.

Immunocytochemical expression of the low-affinity nerve growth factor receptor was studied in human fetal and adult tissues using the monoclonal antibody ME20.4. In dorsal root ganglia, a few immunoreactive neurons were first detected in nine-week-old fetuses and many more were found in the following weeks of gestation. However, none was present in adult ganglia. The ME20.4-positive cells were larger than neurons immunostained by substance P, calcitonin gene-related peptide or galanin antibodies. In the spinal cord, fibres immunostained by ME20.4 appeared in a characteristic pattern that differed from the spatial and temporal distributions of synaptophysin- and neurofilament-immunoreactive fibres. Those expressing the low-affinity nerve growth factor receptor were only detected in regions containing collaterals of primary sensory axons: (i) in the dorsal funiculus between seven and 18 weeks of gestation; (ii) in a ventrodorsal bundle reaching the ventral horn from weeks 12-14; (iii) in the medial region of the dorsal horn between weeks 12 and 20; (iv) in the superficial layers and lateral portion of the dorsal horn after the 14th week of gestation and also in adult spinal cord. During the fetal period, ME20.4 immunoreactivity was also found in motoneurons and peripheral nerve fibres in the skin, myotomes and gut. Sheaths of peripheral nerves and the adventitia of blood vessels were stained both in fetal and adult tissues. Thus, the low-affinity nerve growth factor receptor is: (i) strongly expressed in the developing human nervous system; (ii) transiently associated with a subset of large primary sensory neurons and with motoneurons; (iii) transiently and sequentially expressed by various groups of sensory afferents to the spinal cord; (iv) permanently expressed by fibres in the superficial layers of the dorsal horn, Clarke's column, nerve sheaths and the adventitia of blood vessels.     

Ultrastructural and histochemical evidence for differentiation of intraocular locus coeruleus grafts and invasion of the host iris by central neurites and glia

Summary Intraocular grafts of dorso-lateral pons, including the noradrenaline-containing cell group locus coeruleus, have been studied with ultrastructural and histochemical techniques. Also, the invasion of neuronal and glial constituents from the grafts into the iris of the host animal is described. In mature brain grafts, aggregates of locus coeruleus neurons were easily discernible with monoamine histofluorescence. These cells had an ultrastructural appearance very similar to thatin situ. Numerous somatic spines were frequently associated with synaptic specializations, and monoamine-containing vesicles could be found scattered in the cytoplasm of the locus coeruleus cells. Large neurons of the nucleus tractus mesencephalici nervi trigemini were also found. These cells were neurofilament-immunoreactive just asin situ, and were ultrastructurally characterized by size, distribution of the granular endoplasmic reticulum and abundant large terminals in synaptic contact with their somata and processes. All grafts showed a vigorous astroglial proliferation, evidenced both with immunohistochemistry of glial fibrillary acidic protein and electron microscopy. The astroglial cells were more numerous, larger and with more processes than in adultin situ counterparts.At the attachment site of the brain stem grafts, the iris dilator plate was entirely changed ultrastructurally by a vigorous invasion of neuronal and astrocytic processes. The normal, loose connective tissue stroma of the iris was replaced by layers of almost exclusively central nerve fibres and astrocytes respectively. Monoamine histofluorescence demonstrated an extreme adrenergic hyperinnervation of the iris at the attachment site of the graft, compared to the normal sympathetic ground plexus, whereas neurofilament immunohistochemistry did not visualize any substantial ingrowth of such positive central nerve fibres. Immunohistochemistry of glial fibrillary acidic protein strongly supported the ultrastructural evaluation, showing profound astroglial invasion deep into the iris stroma. Electron microscopic identification of central nerve fibres in the iris showed numerous adrenergic locus coeruleus fibres with small dense-core vesicles. Also, bundles of thin, central, unmyelinated axons were found deep in the iris as well as occasional dendrites. Both large dense-cored and small clear vesicles were encountered in the iris fibres of brain graft origin. Axo-dendritic synaptic specializations formed by locus coeruleus-derived adrenergic fibres were found in the iris.The present results show that there is a profound and intimate contact established between the iris and an immature brain stem area upon intraocular transplantation. The detailed interactions between peripheral iris nerves and supportive glia on one hand, and corresponding central nerves and glia of the grafts on the other hand, can hereby be scrutinized with further histochemical and ultrastructural investigations.     

Heterogeneous visceral nerve changes in acrylamide intoxication

Summary A variety of visceral nerves were studied by intermediate filament immunocytochemistry in rats intoxicated with acrylamide. In such animals, oesophageal and diaphragmatic motor end-plates were invaded and deformed by neurofilament protein-like material, while afferent fibres of diaphragmatic neuromuscular spindles and myelinated sensory fibres of the iris showed striking terminal accumulation of similar material. Conversely, the rich population of thin afferent fibres of the iris showed no obvious abnormality, while pre-terminal changes were seen along the extrinsic nerve fibres supplying the cornea and myenteric ganglia. Multiple lesions were demonstrated in gut nerves of acrylamide-treated rats, while scattered enteric glial cells showed abnormally coarse morphology and a striking increase in glial fibrillary acidic protein immunoreactivity. A distinct, delicately varicose appearence was revealed by neurofilament protein-immunostaining in bladder nerve fibres of normal rats, which was changed to one of coarse dilations by acrylamide. In conclusion, apparently selective changes were found along different types of axons, in dicating marked heterogeneity in cytoskeletal organisation among visceral nerves. Taken together with the proposed inhibition by acrylamide of neurofilament proteins degradation, the above findings may suggest a non-uniform distribution of neurofilament degradation sites along distal regions of different axons.     

Long-term chemical sympathectomy leads to an increase of neuropeptide Y immunoreactivity in cerebrovascular nerves and iris of the developing rat

Short-term (surgical) and long-term (chemical) sympathectomy have revealed the presence of a population of neuropeptide Y-like immunoreactive nerve fibres which do not degenerate in parallel with noradrenaline-containing nerves supplying cerebral vessels and the iris of the rat. Two days after bilateral removal of the superior and middle cervical ganglia of 7-week-old rats, noradrenaline-containing nerves could not be detected along any of the arteries of the rat circle of Willis or of the iris, but 18-32% of neuropeptide Y-like immunoreactive nerves remained. Long-term treatment (6 weeks) with guanethidine commencing in developing 1-week-old rats caused degeneration of the sympathetic neurons in cervical ganglia and disappearance of 5-hydroxydopamine-labelled nerves (that showed dense-cored vesicles at the electron microscope level) from rat cerebral vessels, but did not significantly change the density of neuropeptide Y-like immunoreactive axons on the vessels. Furthermore, whilst in control rats neuropeptide Y-like immunoreactivity was localized largely within 5-hydroxydopamine-labelled cerebrovascular nerves, after long-term sympathectomy with guanethidine, neuropeptide Y-like immunoreactivity was seen only in nerves lacking small dense-cored vesicles. A small number of catecholamine-containing nerves appeared along the internal carotid and anterior cerebral arteries after long-term sympathectomy; these may arise from neurons of central origin. These results suggest that as a consequence of long-term sympathectomy with guanethidine, compensatory changes occur, involving an increase in the expression of neuropeptide Y-like immunoreactivity in non-sympathetic axons in cerebrovascular nerves and iris of the rat. In contrast, the neuropeptide Y-like immunoreactive nerves in the dura mater appear to be entirely sympathetic, since none were present after short-term sympathectomy and none appeared after long-term sympathectomy.     

Re-evaluation and quantification of the different sources of nerve fibres supplying the rat eye

The denervation and/or the removal of peripheral nerve ganglia are useful surgical techniques for studying the source and distribution of peripheral nerves in all organs, including the eye. The amount and distribution of the remaining nerve fibres supplying the eye (after sectioning of various types of nervous fibres and/or removal of nerve ganglia) were evaluated in the rat. Male Sprague-Dawley rats were anaesthetized and one or more of the following nervous tissues were removed: superior cervical ganglion, main ciliary ganglion, pterygopalatine ganglion, trigeminal ganglion and the ophthalmic-maxillary nerve. In some animals, chemical sympathectomy was performed by administration of 6-OH dopamine. The eyes were cut in serial sections, but only three regions (cornea, iris and choroid) were harvested and submitted for various nerve fibre staining techniques. The results were quantified and statistically analysed. Superior cervical ganglionectomy and/or chemical sympathectomy induced the destruction of almost all the catecholaminergic nerve fibres in the three examined regions of the rat eye. Removal of the ciliary ganglion (partial parasympathectomy) caused the destruction of about 60% of the cholinergic nerve fibres of the same regions of the rat eye, while subtotal parasympathectomy destroyed about 80% of the cholinergic nerve fibres. Surgical transsection of the ophthalmo-maxillary nerve or the removal of the trigeminal ganglion led to a degeneration of almost all sensitive nerve fibres of the three examined regions of the rat eye. The denervation experiments confirmed the presence of the different types of nerve fibres (sympathetic, parasympathetic and sensitive) in the three studied structures of the rat eye.     

Connections between Adrenergic Nerves and other Tissue Components in the Eye

The connections between adrenergic nerve fibres and other ocular structures were studied in normal embryonic material (man, dogs, cats, guinea-pigs, and rats) as well as with a special vessel injection technique (adult rats, guinea-pigs, and rabbits). It was established that adrenergic fibres are a normal constituent of the cornea. The adrenergic nerves were more numerous in the embryo than in the adult, and also occurred within the embryonic corneal epithelium. These intraepithelial fibres disappear shortly after birth. Adrenergic fibres running in the connective tissue without connection to vessels were further found in the iris, the limbus region, the chamber angle (of the guinea-pig predominantly) and in the chorioid. It cannot be excluded that these fibres innervate some connective tissue component. In the sphincter pupillae, only a few adrenergic fibres were connected to the vessels, such as was the case also in the ciliary muscle of the guinea-pig. Under the ciliary epithelium of the ciliary body and the ciliary processes there was a thick and dense plexus of adrenergic fibres. Only a restricted number of them was associated with the vessels. The “capillaries” of the ciliary processes were remarkable in that they seemed to possess adrenergic fibres. No adrenergic innervation to the melanophores was apparent.     

Occurrence, distribution and ontogeny of CGRP immunoreactivity in the rat lower respiratory tract: effect of capsaicin treatment and surgical denervations

The occurrence and distribution of calcitonin gene-related peptide (CGRP) immunoreactivity in the rat respiratory tract were investigated by means of immunocytochemistry and radioimmunoassay using antibodies raised in rabbits to synthetic rat CGRP. Substantial amounts of CGRP immunoreactivity (range 5-37 pmol/g) were detected in all parts of the respiratory tract, the highest being in the stem bronchus. Gel filtration chromatography of extractable CGRP immunoreactivity revealed one single peak, eluting at the position of synthetic rat CGRP. CGRP immunoreactivity was localized both in mucosal endocrine cells and nerve fibres from the larynx down to the peripheral lung. CGRP-immunoreactive endocrine cells were found singly in trachea and stem bronchi and in groups in intrapulmonary airways. They appeared at a late stage of gestation (17 days), reached a maximum number near term and decreased after birth to maintain a population similar to that of the adult animals by postnatal day 21. Similarly, CGRP-immunoreactive nerve fibres were first identified by day 18 of the gestation period and reached the adult distribution by postnatal day 21. CGRP-immunoreactive nerve fibres were localized among smooth muscle, seromucous glands, beneath and within the epithelium of the airways and around blood vessels. CGRP was also found in sensory ganglia and in motor end plates of the larynx musculature. Neonatal pretreatment with capsaicin caused a marked reduction in CGRP immunoreactivity of nerve fibres in the respiratory tracts as well as a less marked decrease in the population of CGRP-containing endocrine cells of the lung. No change was seen in motor end plates immunostaining. Vagal ligation experiments revealed that CGRP-immunoreactive nerve fibres travelling in the vagus originate mainly from neurons located in the jugular ganglion. Infranodosal right vagal ligation induced a marked loss in CGRP-immunoreactive nerves of the trachea, and of the ipsilateral stem bronchus, but no changes were observed in peripheral lung. By contrast infranodosal left side vagal ligation caused a decrease in CGRP-immunoreactive nerves of the ipsilateral lung and bronchus without affecting the peptide content in the trachea. Left vagal ligation also induced a marked increase in both the intensity of staining and number of CGRP-immunoreactive endocrine cells in the lung. We conclude that CGRP immunoreactivity is localized in both nerve fibres and endocrine cells and is associated principally with the afferent (sensory) innervation of the respiratory tract.(ABSTRACT TRUNCATED AT 400 WORDS)     

Quantitation of noradrenaline nerve density in mouse iris by computer-assisted image analysis

The density of noradrenaline (NA)-containing nerve fibres in mouse iris was measured with computer-assisted image analysis techniques both under normal conditions and during regeneration. Noradrenaline nerves were visualized by Falck-Hillarp formaldehyde condensation technique in whole-mount spread preparations of mouse irides. The samples were analysed in a fluorescence microscope connected to a commercially available image analysis system (IBAS/Kontron). A software program was developed for specific detection of fluorescence and the nerve density was determined by calculating the area covered by fluorescence in percentage of total measuring field. The method showed good reproducibility as observed both when repeated measurements were performed in the same measuring field or when consecutive measurements on the same set of irides were performed. Also the inter-assay variation between control values in the different experiments was low. Loading of the adrenergic nerves by incubation in alpha-methyl-NA or conditions leading to partial diffusion of the fluorophore had minor effects on the nerve density values. The regeneration of the NA nerve fibres after a selective toxic sympathectomy with 6-hydroxydopamine was also studied. The nerve fibre density values measured by image analysis correlated well with the uptake of [3H]NA; the endogenous NA levels recovered much more slowly, however. It thus seems that endogenous transmitter levels might be a somewhat insensitive index of nerve terminal regrowth, at least in early stages of regeneration. The results indicate that image analysis is a powerful tool to quantitate a transmitter-identified nerve terminal network in a histological preparation.     

Origins of spinal noradrenergic pathways demonstrated by retrograde transport of antibody to dopamine-beta-hydroxylase

The presence, distribution and origin of substance P immunoreactive axons in the rat iris and cornea were investigated in whole mount preparations. A dense network of substance P immunoreactive axons was found throughout the iris but not in the ciliary body. In the cornea, substance P immunoreactive axons were found in the substantia propria, in the subepithelial layer and in the corneal epithelium. Following electrocoagulation of the ophthalmic nerve, most of the substance P immunoreactive axons in the iris and cornea disappeared. No changes in the substance P immunoreactive axons occurred after removal of the superior cervical ganglion. It is concluded that the iris and the cornea are supplied by sensory nerves containing substance P immunoreactivity.     

Coexistence of adrenergic and cholinergic nerves in the inferior hypogastric plexus: anatomical and immunohistochemical study with 3D reconstruction in human male fetus

Classic anatomical methods have failed to determine the precise location, origin and nature of nerve fibres in the inferior hypogastric plexus (IHP). The purpose of this study was to identify the location and nature (adrenergic and/or cholinergic) of IHP nerve fibres and to provide a three-dimensional (3D) representation of pelvic nerves and their relationship to other anatomical structures. Serial transverse sections of the pelvic portion of two human male fetuses (16 and 17 weeks' gestation) were studied histologically and immunohistochemically, digitized and reconstructed three-dimensionally. 3D reconstruction allowed a 'computer-assisted dissection', identifying the precise location and distribution of the pelvic nerve elements. Proximal (supra-levator) and distal (infra-levator) communications between the pudendal nerve and IHP were observed. By determining the nature of the nerve fibres using immunostaining, we were able to demonstrate that the hypogastric nerves and pelvic splanchnic nerves, which are classically considered purely sympathetic and parasympathetic, respectively, contain both adrenergic and cholinergic nerve fibres. The pelvic autonomic nervous system is more complex than previously thought, as adrenergic and cholinergic fibres were found to co-exist in both 'sympathetic' and 'parasympathetic' nerves. This study is the first step to a 3D cartography of neurotransmitter distribution which could help in the selection of molecules to be used in the treatment of incontinence, erectile dysfunction and ejaculatory disorders.     

大鼠消化道神经激肽A的发育研究

应用免疫细胞化学ＰＡＰ法系统研究了大鼠胚胎１３天至成年食道及胃神经激肽Ａ发生发育过程。结果如下：（１）在食道，直至出生前，即胚胎２１天才于环肌层及粘膜肌层出现阳性膨体纤维，出生后，随幼鼠的生长发育相继在上皮内、纵肌层、肌间丛、粘膜下丛出现神经激肽Ａ免疫反应阳性物，其纤维的密度、粗细和着色也逐渐增加，３０天时已具备成年的分布特征，其发育主要在生后４周；（２）在胃，于胚胎１４天，首先在肌间丛处呈现阳性     

The distribution of sensory and motor axons of the intercostal nerves and their branches (author's transl)]

As it is well established that motor axons in general display a higher acetylcholinesterase-activity than sensory axons do, the histochemical method of KARNOVSKY and ROOTS (1964) was used for the differentiation of motor and sensory fibres in the intercostal nerves and their branches. In the paravertebral sections of the intercostal nerves of the upper segments 30--35% of the nerve fibres show a high enzyme activity and therefore were classified as motoric. The percentage of the motor fibres in comparable zones of the lower segments increases to 45%. Only 15% of the nerve fibres proved to be motoric in the parasternal sections of the intercostal nerves. In a histogram of the acetylcholinesterase-positive intercostal nerve fibres 2 peaks can be seen: one in the alpha-calibre class, the second in the gamma-class. There are more motor axons in the lateral cutaneous branch of the lower intercostal nerve than in upper ones. This may be explained by the participation of these nerve branches in the innervation of the abdominal muscles. In 2 cases nerve branches of the intercostal nerve to the diaphragm were found containing 15--25% motor axons.     

Fine structure of the rat carotid body transplanted into the anterior chamber of the eye

Summary Rat carotid bodies transplanted into the anterior chamber of the eye were studied by electron microscopy. Chief and sustentacular cells and a few ganglion cells survived for 3 months and maintained cytological characteristics similar to those in the intact carotid body. The transplant contained many fenestrated capillaries. Chief cells at the periphery of the cell cluster had long cytoplasmic processes which projected into the stroma of the iris. The cell processes became incorporated into bundles containing nerve fibres, which were enveloped by a perineurial sheath. Three types of nerve fibres were identified in the explant. Type I and type II nerve fibres (presumptive cholinergic and adrenergic, respectively) were enclosed by sustentacular and satellite cells. Most of the nerve fibres were completely separated from chief cells and ganglion cells by sustentacular and satellite cells. A few nerve fibres made direct apposition to chief cells and ganglion cells, where some nerves were presynaptic to them. Type III nerve fibres derived from myelinated nerve fibres were also enclosed by sustentacular and satellite cells.     

Motor unit numbers,motor unit sizes and innervation of single muscle fibres in hyperinnervated adult mouse soleus muscle

The sural and the lateral plantar nerves were implanted simultaneously into the denervated soleus muscle of adult mice. Each of these nerves contained approximately the normal number of soleus motor axons. This procedure therefore allowed a study of how an initial excessive number of motor axons provided by two different, foreign nerves and terminating into the soleus muscle affected the final pattern of muscle innervation. In muscles examined two months or more after the implantation of the foreign nerves all muscle fibres were innervated. The fraction of the muscle innervated by either nerve varied widely from one preparation to another. However, all the motor axons which were implanted into the muscle appeared to make permanent synapses. Moreover, the distribution of motor unit sizes of each foreign nerve relative to the total number of muscle fibres innervated by that nerve was similar to the distribution of motor unit sizes in muscles cross-innervated by that nerve alone, although the absolute motor unit sizes were reduced. Estimated by intracellular recording, 20–30% of the muscle fibres were polyneuronally innervated. A similar fraction of teased muscle fibres stained for acetylcholinesterase had more than one endplate.     

Distribution of histamine in the developing peripheral nervous system

The presence and ontogenetic distribution of histamine was studied in the developing peripheral nervous system of the rat by using an indirect immunofluorescence technique and a specific rabbit anti-histamine antiserum. Histamine immunoreactivity (IR) first appeared in peripheral nerves on embryonic day 14. The number and intensity of histamine-immunoreactive nerves was highest on embryonic days 16–18. During development starting from embryonic day 14, motoneurones in ventral horns of the spinal cord at cervical, thoracic and lumbar levels contained histamine IR. A subpopulation of sensory neurones in dorsal root ganglia exhibited histamine IR. Histamine IR was also present in nerve fibres of ventral and dorsal roots of spinal cord, as well as in spinal nerves. Population of neurones and nerve fibres in sympathetic and pelvic ganglia as well as in myenteric ganglia of the intestine were also labelled with the histamine antiserum. In peripheral target organs, histamine IR was observed in nerve fibres around bronchi of the lungs, in the atria of the heart, in the adrenal gland, in the intestinal wall, in muscular tissues and in subepithelial tissue of the skin.The results of this study indicate that histamine is widely distributed in different types of neurones and nerve fibres of the developing peripheral nervous system.     

GAP-43 immunoreactivity is widespread in the autonomic neurons and sensory neurons of the rat.

GAP-43 is a membrane-bound phosphoprotein generally associated with axon growth during development and regeneration. Using immunohistochemical and immunoblotting techniques this study shows that GAP-43 is expressed extensively in the unperturbed adult autonomic nervous system. Strong immunoreactivity was seen in the developing and mature enteric subdivision of the autonomic nervous system and in nerves of the iris and various blood vessels. The presence of GAP-43 immunoreactivity in varicose nerve fibres, and a comparison of the labelling pattern of GAP-43 with the nerve associated marker PGP 9.5 suggests that GAP-43 is present in most or all autonomic nerve fibres in these organs. Immunoblotting of gut samples on 10% polyacrylamide gels revealed a single band of approximately 45,000 mol. wt that co-migrated with pure central nervous system GAP-43. Surgical sympathectomy experiments resulting in almost complete elimination of sympathetic fibres did not markedly affect the pattern of GAP-43 immunoreactivity in the iris, indicating that GAP-43 is expressed not only in sympathetic nerves but also in parasympathetic and sensory fibres. These findings show that GAP-43 is expressed extensively in autonomic nerves of the adult rat, at levels comparable to those seen during development. High levels of GAP-43 are not therefore restricted to development and regeneration in this part of the nervous system.