A large proportion of pelvic neurons innervating the corpora cavernosa of the rat penis exhibit NADPH-diaphorase activity

Nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase histochemistry, which indicates the presence of neural nitric oxide synthase, the enzyme responsible for the generation of nitric oxide, was used in combination with retrograde labelling methods to determine, in whole-mounts and sections of rat major pelvic ganglia, whether neurons destined for the penile corpora cavernosa were able to produce nitric oxide. In whole-mount preparations of pelvic ganglia, among the 607±106 retrogradely labelled neurons innervating the penile corpora cavernosa, 84±7% were NADPH-diaphorase-positive, 30±7% of which were intensely histochemically stained. In serial sections of pelvic ganglia, out of a mean count of 451 retrogradely labelled neurons, 65% stained positively for NADPH-diaphorase. An average of 1879±363 NADPH-diaphorase positive cell bodies was counted in the pelvic ganglion. In the major pelvic ganglion, neurons both fluorescent for Fluorogold or Fast Blue and intensely stained for NADPH-diaphorase were consistently observed in the dorso-caudal part of the ganglia in the area close to the exit of the cavernous nerve and within this nerve. This co-existence was much less constant in other parts of the ganglion. In the rat penis, many NADPH-diaphorase-positive fibres and varicose terminals were observed surrounding the penile arteries and running within the wall of the cavernous spaces. This distribution of NADPH-diaphorase-positive nerve cells and terminals is consistent with the idea that the relaxation of the smooth muscles of the corpora cavernosa and the dilation of the penile arterial bed mediated by postganglionic parasympathetic neurons is attributable to the release of nitric oxide and that nitric oxide plays a crucial role in penile erection. Moreover, the existence in the pelvic ganglion of a large number of NADPH-diaphorase-positive neurons that are not destined for the corpora cavernosa suggests that nitric oxide is probably also involved in the function of other pelvic tissues.     

Distribution of neurons in the major pelvic ganglion of the rat which supply the bladder,colon or penis

Summary In male rats a large number of the postganglionic neurons which innervate the pelvic organs are located in the major pelvic ganglion. In the present study we have identified the location within this ganglion of neurons which project to either of three pelvic organs, the penis, colon or urinary bladder. Two fluorescent retrogradely-transported dyes, Fast Blue and Fluoro-Gold, were used. For most animals one dye was injected into the cavernous space of the penis, the wall of the distal colon or the wall of the urinary bladder. In a small number of animals two organs were injected, each with a different dye. One to six weeks after injection the major pelvic ganglia were fixed in buffered formaldehyde. The distribution of fluorescent dye-labelled cells was observed in whole mounts of complete ganglia and, in most cases, also in small accessory ganglia located between the ureter and the prostate. The studies showed a unique pattern of distribution for each organ-specific group of neurons. Most of the colon neurons are located in the major pelvic ganglion near the entrance of the pelvic nerve, whereas almost all of the penis neurons are near or within the penile nerve. Bladder neurons are relatively evenly distributed throughout the ganglion. These results demonstrate a distinct topographical organization of organ-specific neurons of the major pelvic ganglion of the male rat, a phenomenon which has also been observed in other peripheral ganglia.     

Coexistence of NADPH-diaphorase with vasopressin and oxytocin in the hypothalamic magnocellular neurosecretory nuclei of the rat

Coexistence of NADPH-diaphorase with vasopressin and oxytocin was studied in the magnocellular neurosecretory nuclei of the rat hypothalamus by use of sequential histochemical and immunocytochemical techniques in the same sections. Coexistence was found in all the nuclei examined (supraoptic, paraventricular, circular, fornical, and in some isolated neurons located in the hypothalamic area between the paraventricular and supraoptic nuclei). The ratios of neurons expressing both markers (NADPH-diaphorase and vasopressin, NADPH-diaphorase and oxytocin) in each of the nuclei were very similar. Although further studies must be carried out, the partial coexistence found in all nuclei suggests that NADPH-diaphorase is probably not related to general mechanisms involving vasopressin and oxytocin, but rather in specific functions shared by certain hypothalamic neuronal cell populations.     

Structures with GABA-like and GAD-like immunoreactivity in the cervical sympathetic ganglion complex of adult rats

Summary The distribution of gamma-aminobutyric acid (GABA)-like and glutamate decarboxylase (GAD)-like immunoreactivity was studied in the cervical sympathetic ganglion complex of rats, including the intermediate and inferior cervical ganglia and the uppermost thoracic ganglion. GABA-positive axons may enter the ganglion complex via its caudal end. Others apparently arise from small GABA-positive cell bodies which are scattered among principal neurons, within clusters of SIF cells and in bundles of GABA-negative axons. The majority of these cells is located in the lower half of the ganglion complex. Principal neurons did not react with antibodies against GABA or GAD. An unevenly distributed meshwork of GABA-immunoreactive axons was seen in each of the ganglia. Immunoreactive axons formed numerous varicosities. Some of them were aggregated in a basket-like form around a subpopulation of GABA-negative principal ganglion cell bodies. Electron-microscopic immunocytochemistry revealed that GABA-positive nerve fibers establish asymmetric synaptic junctions with dendritic and somatic spines of principal neurons, whereas postsynaptic densities are inconspicous or absent on dendritic shafts and somata. The results suggest that in the cervical sympathetic ganglion complex principal neurons are not GABAergic, but are innervated by axons which react with both antibodies against GAD and/ or GABA antibodies and originate from a subpopulation of small neurons.     

Nitric oxide nerves in the uterus are parasympathetic,sensory, and contain neuropeptides

Nitric oxide (NO) is synthesized in neurons and is a potent relaxor of vascular and nonvascular smooth muscle. The uterus contains abundant NO-synthesizing nerves which could be autonomic and/or sensory. This study was undertaken to determine: 1) the source(s) of NO-synthesizing nerves in the rat uterus and 2) what other neuropeptides or transmitter markers might coexist with NO in these nerves. Retrograde axonal tracing, utilizing Fluorogold injected into the uterine cervix, was employed for identifying sources of uterine-projecting neurons. NO-synthesizing nerves were visualized by staining for nicotinamide adenine dinucleotide phosphate (reduced)-diaphorase (NADPH-d) and immunostaining with an antibody against neuronal/type I NO synthase (NOS). NADPH-d-positive perikarya and terminal fibers were NOS-immunoreactive (-I). Some NOS-I/NADPH-d-positive nerves in the uterus are parasympathetic and originate from neurons in the pelvic paracervical ganglia (PG) and some are sensory and originate from neurons in thoracic, lumbar, and sacral dorsal root ganglia. No evidence for NOS-I/NADPH-d-positive sympathetic nerves in the uterus was obtained. Furthermore, double immunostaining revealed that in parasympathetic neurons, NO-I/NADPH-d-reactivity coexists with vasoactive intestinal polypeptide, neuropeptide Y, and acetylcholinesterase and in sensory nerves, NOS-I/NADPH-d-reactivity coexists with calcitonin generelated peptide and substance P. In addition, tyrosine hydroxylase(TH)-I neurons of the PG do not contain NOS-I/NADPH-d-reactivity, but some TH-I neurons are apposed by NOS-I varicosities. These results suggest NO-synthesizing nerves in the uterus are autonomic and sensory, and could play significant roles, possibly in conjunction with other putative transmitter agents, in the control of uterine myometrium and vasculature.     

Plasticity in expression of calcitonin gene-related peptide and substance P immunoreactivity in ganglia and fibres following guanethidine and/or capsaicin denervation

Summary This study was designed to investigate the effects of multiple denervation procedures on calcitonin gene-related peptide- and substance P-immunoreactive neurons in sympathetic and sensory cranial ganglia and in selected targets. Sympathectomy by long-term guanethidine treatment induced a pronounced increase in calcitonin gene-related peptide-immunoreactive and substance P-immunoreactive nerve fibres in all the tissues investigated, in contrast to a significant reduction of immunoreactive cell bodies. Neonatal capasaicin treatment abolished substance P immunoreactivity in many targets and caused a dramatic reduction of substance P-immunoreactive sensory nerve cell bodies; calcitonin gene-related peptide-immunoreactive nerve density was decreased, but the number of immunoreactive nerve cell bodies was unchanged. Guanethidine treatment of capsaicin-injected rats reversed the loss of calcitonin gene-related peptide-immunoreactive nerves, but not that of substance P-immunoreactive neurons. In the iris, capsaicin treatment had little effect on calcitonin gene-related peptide- and substance P-immunoreactive nerves, suggesting that in rats the majority of these fibres originate from capsaicin-insensitive neurons. The results suggest that the denervation procedures used in this study alter the synthesis and transport of neuropeptides in sensory neurons in conjunction with changes in the number of nerve fibres.     

Immunohistochemical analysis of intracardiac ganglia of the rat heart

The neurochemistry of intracardiac neurons in whole-mount preparations of the intrinsic ganglia was investigated. This technique allowed the study of the morphology of the ganglionated nerve plexus found within the atria as well as of individual neurons. Intracardiac ganglia formed a ring-like plexus around the entry of the pulmonary veins and were interconnected by a series of fine nerve fibres. All intracardiac neurons contained immunoreactivity to PGP-9.5, choline acetyl transferase (ChAT) and neuropeptide Y (NPY). Two smaller subpopulations were immunoreactive to calbindin or nitric oxide synthase. Furthermore, a subpopulation (approximately 6%) of PGP-9.5/ChAT/NPY-immunoreactive cells lacking both calbindin and nitric oxide synthase (NOS) was surrounded by pericellular baskets immunoreactive to ChAT and calbindin. Vasoactive intestinal peptide (VIP), calcitonin gene-related peptide (CGRP), pituitary adenylate cyclase-activated peptide (PACAP), substance P and tyrosine hydroxylase (TH) immunoreactivity was observed in nerve fibres within the ganglion, but never in neuronal somata. Furthermore, immunoreactivity for NPY was not observed in pericellular baskets surrounding intracardiac neurons, despite being present in all intrinsic neuronal cell bodies. Taken together, the results of this study indicate a moderate level of chemical diversity within the intracardiac neurons of the rat. Such chemical diversity may reflect functional specialisation of neurons in the intracardiac ganglia.This work was supported by a grant-in-aid (G00M0670) from the National Heart Foundation of Australia     

Expression and colocalization of NADPH-diaphorase and heme oxygenase-2 in trigeminal ganglion and mesencephalic trigeminal nucleus of the rat

Carbon monoxide (CO) and nitric oxide (NO) are two endogenously produced gases that can function as second messenger molecules in the nervous system. The enzyme systems responsible for CO and NO biosynthesis are heme oxygenase (HO) and nitric oxide synthase (NOS), respectively. The present study was undertaken to examine the distribution of HO-2 and NOS of the trigeminal primary afferent neurons of the rat, located in the trigeminal ganglion (TG) and mesencephalic trigeminal nucleus (MTN), using histochemistry and immunohistochemistry. NADPH-d staining was found in most neurons in TG. The intensely NADPH-d-stained neurons were small- or medium-sized, while the large-sized neurons were less intensely stained. Immunocytochemistry for HO-2 revealed that almost all neurons in TG expressed HO-2, but they did not appear cell size-specific pattern. NADPH-d and HO-2 positive neurons appeared the same pattern, which was NADPH-d activity and HO-2 expression progressively declined from the caudal to rostral part of the MTN. A double staining revealed that the colocalization of NADPH-d/HO-2 neurons was 97.3% in TG and 97.6% in MTN. The remarkable parallels between NADPH-d and HO-2 suggest that NO and CO are likely neurotransmitters and mediate the orofacial nociception and sensory feedback of the masticatory reflex arc together.     

NADPH-diaphorase activity in the nodose ganglion of normal and vagotomized guinea-pigs

The activity and distribution of reduced nico-tinamide adenine dinucleotide phosphate diaphorase (NADPH-diaphorase) in the nodose ganglion of normal and vagotomized guinea-pigs were examined by light and electron microscopy. Light microscopy confirmed a remarkable increase in the number of NADPH-diaphorase-reactive neurons in the nodose ganglion following unilateral cervical vagotomy. The increase was present at 5 days but became more prominent at 10 days and was sustained until at least 30 days after vagotomy when compared with the non-lesioned side. The NADPH-diaphorase reaction product was associated with the membrane of the rough endoplasmic reticulum, Golgi apparatus, mitochondria and nucleus of the nodose neurons. In animals killed 5 days post-operation, there was no noticeable degeneration in the nodose neurons. However, at 10 days, the mitochondria in some neurons appeared swollen and vacuolated with disrupted cristae. These changes were accentuated in some nodose neurons 20 and 30 days after vagotomy but there was no evidence of cell death. All the degenerating neurons exhibited NADPH-diaphorase activity. The increase in NADPH-diaphorase activity in the neuronal somata after vagotomy suggests that the enzyme is involved in either the retrograde degeneration or the recovery of the lesioned neurons. Received: 15 June 1995 / Accepted: 15 February 1996     

Distribution of activity of alkaline phosphatase and Mg-dependent adenosine triphosphatase in the cranial dura mater-arachnoid interface zone of the rat

Summary The distribution of the activity of alkaline phosphatase and Mg-dependent adenosine triphosphatase was studied in the encephalic dura mater-arachnoid borderline (interface) zone of albino Wistar rats. Intense clustering of electron-dense granules that indicated alkaline phosphatase activity was observed in the inner dural cells, the neurothelial cells, the outermost row of the outer arachnoidal cells and in the intercellular cleft between the latter two (the so-called electron-dense band). The remainder of the outer arachnoidal cells contained almost no reaction product. Mg-adenosine triphosphatase activity was distributed differently; a lack of reaction product was observed not only in the outer arachnoidal cells, but also in the zone occupied by the electron-dense band. The data confirm histochemically the barrier properties of the dura mater-arachnoid interface zone.     

Formation of contacts between mast cells and sympathetic neurons in vitro

Summary Functional interactions between mast cells and peripheral nerves may occur at sites of association seen in vivo. To study the interactions, we developed a tissue culture model of murine sympathetic neurons co-cultured with rat basophilic leukaemia (RBL-2H3) cells (homologues of mucosal mast cells) or rat peritoneal mast cells. In co-cultures of up to 3 days, light microscopy identified neurite contacts with peritoneal mast cells or RBL-2H3 cells, but not with glial cells or fibroblasts. Electron microscopy confirmed membrane-membrane contact between neurites and RBL-2H3 cells. Time-lapse analysis of interactions between neurons and RBL-2H3 cells showed that 60–100% of the cells in a given field acquired neurite contact within 17 h. In matching control studies, there was no increase in the frequency of neurite contact with cells of the rat plasmacytoma line (YB2/0): these were not selected as targets, and contacts were broken if formed. Time-lapse records of the derivation of neurites from their path suggested a neurotropic effect of mast cells, with neurite contact ensuing when the intervening distance was less than 36±4 m. Once formed, contacts were invariably maintained throughout the period of examination (up to 72 h), in contrast to YB2/0 or fibroblast contacts. We conclude that neurons selectively form and maintain connections with cells representative of rat connective tissue-type and mucosal mast cells in vitro. Similar interactions in vivo could promote nerve/mast cell contacts, which may allow bidirectional communication between the nervous and immune systems.     

Role of neurotrophin signalling in the differentiation of neurons from dorsal root ganglia and sympathetic ganglia

Manipulation of neurotrophin (NT) signalling by administration or depletion of NTs, by transgenic overexpression or by deletion of genes coding for NTs and their receptors has demonstrated the importance of NT signalling for the survival and differentiation of neurons in sympathetic and dorsal root ganglia (DRG). Combination with mutation of the proapoptotic Bax gene allows the separation of survival and differentiation effects. These studies together with cell culture analysis suggest that NT signalling directly regulates the differentiation of neuron subpopulations and their integration into neural networks. The high-affinity NT receptors trkA, trkB and trkC are restricted to subpopulations of mature neurons, whereas their expression at early developmental stages largely overlaps. trkC is expressed throughout sympathetic ganglia and DRG early after ganglion formation but becomes restricted to small neuron subpopulations during embryogenesis when trkA is turned on. The temporal relationship between trkA and trkC expression is conserved between sympathetic ganglia and DRG. In DRG, NGF signalling is required not only for survival, but also for the differentiation of nociceptors. Expression of neuropeptides calcitonin gene-related peptide and substance P, which specify peptidergic nociceptors, depends on nerve growth factor (NGF) signalling. ret expression indicative of non-peptidergic nociceptors is also promoted by the NGF-signalling pathway. Regulation of TRP channels by NGF signalling might specify the temperature sensitivity of afferent neurons embryonically. The manipulation of NGF levels “tunes” heat sensitivity in nociceptors at postnatal and adult stages. Brain-derived neurotrophic factor signalling is required for subpopulations of DRG neurons that are not fully characterized; it affects mechanical sensitivity in slowly adapting, low-threshold mechanoreceptors and might involve the regulation of DEG/ENaC ion channels. NT3 signalling is required for the generation and survival of various DRG neuron classes, in particular proprioceptors. Its importance for peripheral projections and central connectivity of proprioceptors demonstrates the significance of NT signalling for integrating responsive neurons in neural networks. The molecular targets of NT3 signalling in proprioceptor differentiation remain to be characterized. In sympathetic ganglia, NGF signalling regulates dendritic development and axonal projections. Its role in the specification of other neuronal properties is less well analysed. In vitro analysis suggests the involvement of NT signalling in the choice between the noradrenergic and cholinergic transmitter phenotype, in the expression of various classes of ion channels and for target connectivity. In vivo analysis is required to show the degree to which NT signalling regulates these sympathetic neuron properties in developing embryos and postnatally. U.E. is supported by the DFG (Er145-4) and the Gemeinnützige Hertie-Stiftung.     

NADPH-diaphorase-positive nerve fibers associated with motor endplates in the rat esophagus: new evidence for co-innervation of striated muscle by enteric neurons

NADPH-diaphorase histochemistry was combined with demonstration of acetylcholinesterase and immunocytochemistry for calcitonin gene-related peptide to study esophageal innervation in the rat. Most of the myenteric neurons stained positively for NADPH-diaphorase, as did numerous varicose nerve fibers in the myenteric plexus, among striated muscle fibers, around arterial blood vessels, and in the muscularis mucosae. A majority of motor endplates (as demonstrated by acetylcholinesterase histochemistry or calcitonin gene-related peptide immunocytochemistry) were associated with fine varicose NADPH-diaphorase-positive nerve fibers. Analysis of brainstem nuclei, sensory vagal, spinal, and sympathetic ganglia in normal and neonatally capsaicin-treated rats, and comparison with anterogradely labeled vagal branchiomotor, preganglionic and sensory fibers led to the conclusion that NADPH-diaphorase-positive fibers on motor endplates originate in esophageal myenteric neurons. No association of NADPH-diaphorasepositive nerve fibers with motor endplates was found in other organs containing striated muscle. These results suggest extensive, presumably nitrergic, co-innervation of esophageal striated muscle fibers by enteric neurons. Thus, control of peristalsis in the esophagus of the rat may be more complex than hitherto assumed.     

CGRP immunoreactivity and NADPH-diaphorase in afferent nerves of the rat penis

Calcitonin gene-related peptide (CGRP)-immunoreactive afferent nerve fibers are abundant in the rat penis. In addition, NADPH-diaphorase, which stains for nitric oxide synthase, has been localized within both autonomic and sensory dorsal root ganglia (DRG) and may be part of an important biochemical pathway involved in penile tumescence. The purpose of this study was: 1) to examine the circuitry of afferent nerves that are CGRP immunoreactive from the L6 DRG, 2) to examine the possibility that there are NADPH-diaphorase-positive afferent fibers from the L6 DRG to the rat penis, and 3) to examine the localization and colocalization of CGRP and NADPH-diaphorase within L6 DRG afferent perikarya. Calcitonin gene-related peptide immunostaining in the penis was eliminated following a bilateral transection of the pudendal nerves, but was unchanged following a bilateral transection of the pelvic splanchnic or hypogastric nerves. The NADPH-diaphorase staining was not altered by any of the nerve transections. Injection of the retrograde axonal tracer fluorogold (FG) into the dorsum penis labeled perikarya in the L6 DRG. Although the majority of FG-labeled perikarya contained neither CGRP nor NADPH-diaphorase, small subpopulations of perikarya contained either CGRP immunoreactivity, NADPH-diaphorase, or both. A unilateral pudendal nerve transection virtually eliminated (>99%) FG labeling in the ipsilateral L6 DRG. These data suggest that NADPH-diaphorase and CGRP are present, either together or separately, within a subpopulation of penile afferent perikarya. In addition, CGRP-immunoreactive afferent nerve fibers reach the penis primarily via the pudendal nerves. Finally, NADPH-diaphorase-positive penile afferents may be another important source of nitric oxide (NO) for penile tumescence.     

Gene expression and localization of diacylglycerol kinase isozymes in the rat spinal cord and dorsal root ganglia

The dorsal root ganglion (DRG) and dorsal horn of the spinal cord are areas through which primary afferent information passes enroute to the brain. Previous studies have reported that, during normal neuronal activity, the regional distribution of a second messenger, diacylglycerol (DG), which is derived from phosphoinositide turnover, is diverse in these areas. However, the way that DG is regulated in these organs remains unknown. The present study was performed to investigate mRNA expression and protein localization of DG kinase (DGK) isozymes, which play a central role in DG metabolism. Gene expression for DGK isozymes was detected with variable regional distributions and intensities in the spinal cord. Among the isozymes, most intense signals were found for DGKζ and DGKι in the DRG. By immunohistochemical analysis, DGKζ immunoreactivity was detected heterogeneously in the nucleus and cytoplasm of small DRG neurons with variable levels of distribution, whereas it was detected exclusively in the cytoplasm of large neurons. On the other hand, DGKι immunoreactivity was distributed solely in the cytoplasm of most of the DRG neurons. Double-immunofluorescent imaging of these isozymes showed that they coexisted in a large population of DRG neurons at distinct subcellular sites, i.e., DGKζ in the nucleus and DGKι in the cytoplasm. Thus, DGK isozymes may have different functional roles at distinct subcellular sites. Furthermore, the heterogeneous subcellular localization of DGKζ between the nucleus and cytoplasm implies the possible translocation of this isozyme in small DRG neurons under various conditions.The work was supported by grants-in-aid from the Ministry of Education, Science, Culture, and Sports of Japan (M.T., K.G.) and from the Ono Medical Research Foundation, Kato Memorial Bioscience Foundation, and Janssen Pharmaceutical (K.G.) and by the 21st Century Center of Excellence Program of the Ministry of Education, Culture, Sports, Science and Technology of Japan.     

In vivo secretory responses of submandibular glands in streptozotocin-diabetic rats to sympathetic and parasympathetic nerve stimulation

Submandibular gland responses to sympathetic and parasympathetic nerve stimulation were studied in streptozotocin-diabetic rats. Morphologically, the acinar cells in control glands were relatively uniform in size and contained electron-lucent granules. The granular ducts were distinguished by the presence of electron-dense granules. With the exception of intracellular lipid droplets and the presence of a few autophagosomes in diabetic glands, no consistent differences in acinar cell structure were observed. In contrast, the diameter of the granular ducts and the granule content of their cells were less in diabetic glands. At 3 weeks sympathetic flow rate, salivary protein concentration, and total protein output were unaffected by diabetes. Sympathetic flow rate was greater at 3 months, and the concentration of protein in the saliva was lower. In 6-month diabetic rats flow rate remained increased, but protein concentration and total protein output were reduced. The decrease in salivary protein concentration at 3 and 6 months was accompanied by a reduction in secretory granule release from acinar and granular duct cells. No consistent differences in flow rate, protein concentration, protein output, or secretory granule release were observed following parasympathetic stimulation. We conclude that the effects of diabetes on nerve-stimulated flow rate and protein release depend on the duration of diabetes and the type of stimulation, and are independent of one another.     

Nitric oxide synthase in the rat carotid body and carotid sinus

The participation of nitric oxide synthase (NOS) in the innervation of the rat carotid body and carotid sinus was investigated by means of NADPH-diaphorase histochemistry and NOS immunohistochemistry using antisera raised against purified neuronal NOS and a synthetic tridecapeptide. NOS was detected in 23% of neurons at the periphery of the carotid bodies. Some negative neurons were surrounded by NOS-positive terminals. NOS-containing varicose nerve fibres innervated the arterial vascular bed and, to a lesser extent, the islands of glomus cells. These fibres persisted after transection of the carotid sinus nerve and are probably derived from intrinsic neurons. Large NOS-positive axonal swellings in the wall of the carotid sinus were absent after transection of the sinus nerve, indicating their sensory origin. The results suggest a neuronal nitrergic control of blood flow, neuronal activity and chemoreception in the carotid body, and an intrinsic role of NO in the process of arterial baroreception.     

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

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