Target-related patterns of co-existence of neuropeptide Y, vasoactive intestinal peptide, enkephalin and substance P in cranial parasympathetic neurons innervating the facial skin and exocrine glands of guinea-pigs

The human major sublingual gland and its neuropeptidergic and nitrergic innervations

BACKGROUND

What textbooks usually call the sublingual gland in humans is in reality a tissue mass of two types of salivary glands, the anteriorly located consisting of a cluster of minor sublingual glands and the posteriorly located major sublingual gland with its outlet via Bartholin's duct. Only recently, the adrenergic and cholinergic innervations of the major sublingual gland was reported, while information regarding the neuropeptidergic and nitrergic innervations is still lacking.

METHODS

Bioptic and autoptic specimens of the human major sublingual gland were examined by means of immunohistochemistry for the presence of vasoactive intestinal peptide (VIP)-, neuropeptide Y (NPY)-, substance P (SP)-, calcitonin gene related-peptide (CGRP)-, and neuronal nitric oxide synthase (nNOS)-labeled neuronal structures.

RESULTS

As to the neuropeptidergic innervation of secretory cells (here in the form of mucous tubular and seromucous cells), the findings showed many VIP-containing nerves, few NPY- and SP-containing nerves and a lack of CGRP-labeled nerves. As to the neuropeptidergic innervation of vessels, the number of VIP-containing nerves was modest, while, of the other neuropeptide-containing nerves under study, only few (SP and CGRP) to very few (NPY) nerves were observed. As to the nitrergic innervation, nNOS-containing nerves were very few close to secretory cells and even absent around vessels.

CONCLUSION

The various innervation patterns may suggest potential transmission mechanisms involved in secretory and vascular responses of the major sublingual gland.

Skin neuropathy and immunomodulation in diseases

Skin is a vital barrier tissue of the body. Immune responses in the skin must be precisely controlled, which would otherwise cause severe disease conditions such as psoriasis, atopic dermatitis, or pathogenic infection. Research evidence has increasingly demonstrated the essential roles of neural innervations, i.e., sensory and sympathetic signals, in modulating skin immunity. Notably, neuropathic changes of such neural structures have been observed in skin disease conditions, implicating their direct involvement in various pathological processes. An in-depth understanding of the mechanism underlying skin neuropathy and its immunomodulatory effects could help reveal novel entry points for therapeutic interventions. Here, we summarize the neuroimmune interactions between neuropathic events and skin immunity, highlighting the current knowledge and future perspectives of this emerging research frontier.

Parasympathetic neurons in the human submandibular ganglion

The submandibular ganglion (SMG) contains parasympathetic neurons which innervate the submandibular gland. In this study, immunohistochemistry for vasoactive intestinal polypeptide (VIP), neuropeptide Y (NPY), choline acetyltransferase (ChAT), dopamine β-hydroxylase (DBH), tyrosine hydroxylase (TH), and the transient receptor potential cation channel subfamily V members 1 (TRPV1) and 2 (TRPV2) was performed on the human SMG. In the SMG, 17.5 % and 8.9 % of parasympathetic neurons were immunoreactive for VIP and TRPV2, respectively. SMG neurons mostly contained ChAT- and DBH-immunoreactivity. In addition, subpopulations of SMG neurons were surrounded by VIP (69.6 %)-, TRPV2 (54.4 %)- and DBH (9.5 %)-immunoreactive (-ir) nerve fibers. SMG neurons with pericellular VIP- and TRPV2-ir nerve fibers were significantly larger than VIP- and TRPV2-ir SMG neurons, respectively. Other neurochemical substances were rare in the SMG. In the human submandibular gland, TRPV1- and TRPV2-ir nerve fiber profiles were seen around blood vessels. Double fluorescence method also demonstrated that TRPV2-ir nerve fiber profiles were located around myoepithelial and acinar cells in the submandibular gland. VIP and TRPV2 are probably expressed by both pre- and post-ganglionic neurons innervating the submandibular and sublingual glands. VIP, DBH and TRPV2 may have functions about regulation of salivary components in the salivary glands and neuronal activity in the SMG.

Pre- and postnatal development of the otic ganglion in humans

Only a few papers exist dealing with the development and aging of the autonomic nervous system - and even rarer are studies that investigated the otic ganglion. Using a special trepan, we removed and investigated 172 samples from 86 corpses, ranging from 20 weeks of gestational age (GA) to 95 years of age. The aim of the study was to measure different morphometric parameters of the ganglionic neurons in order to study age-related changes from early development until old age. Fetuses show the highest numerical density of neurons. Then, in the first years of life, a rapid growth of the cytoplasm takes place, which is the main reason for the neuronal growth and the increase of the general size of the otic ganglion at this age. Also, the number of satellite cells increases till puberty. In adults, the parameters are relatively stable over decades and decrease slowly, in contrast to the steep increase in the first years of life. Moreover, neuronal degeneration, storage of pigments, neuro-axonal dystrophy, and lymphocytic infiltrates increase with age.

Overview of the Anatomy, Physiology, and Pharmacology of the Autonomic Nervous System

Comprised of the sympathetic nervous system, parasympathetic nervous system, and enteric nervous system, the autonomic nervous system (ANS) provides the neural control of all parts of the body except for skeletal muscles. The ANS has the major responsibility to ensure that the physiological integrity of cells, tissues, and organs throughout the entire body is maintained (homeostasis) in the face of perturbations exerted by both the external and internal environments. Many commonly prescribed drugs, over-the-counter drugs, toxins, and toxicants function by altering transmission within the ANS. Autonomic dysfunction is a signature of many neurological diseases or disorders. Despite the physiological relevance of the ANS, most neuroscience textbooks offer very limited coverage of this portion of the nervous system. This review article provides both historical and current information about the anatomy, physiology, and pharmacology of the sympathetic and parasympathetic divisions of the ANS. The ultimate aim is for this article to be a valuable resource for those interested in learning the basics of these two components of the ANS and to appreciate its importance in both health and disease. Other resources should be consulted for a thorough understanding of the third division of the ANS, the enteric nervous system. © 2016 American Physiological Society. Compr Physiol 6:1239-1278, 2016.

Primary afferent neurons containing calcitonin gene-related peptide but not substance P in forepaw skin, dorsal root ganglia, and spinal cord of mice

In mice dorsal root ganglia (DRG), some neurons express calcitonin gene-related peptide (CGRP) without substance P (SP; CGRP(+) SP(-) ). The projections and functions of these neurons are unknown. Therefore, we combined in vitro axonal tracing with multiple-labeling immunohistochemistry to neurochemically define these neurons and characterize their peripheral and central projections. Cervical spinal cord, DRG, and forepaw skin were removed from C57Bl/6 mice and multiple-labeled for CGRP, SP, and either marker for the sensory neuron subpopulations transient receptor potential vanilloid type 1 (TRPV1), neurofilament 200 (NF200), or vesicular glutamate transporter 2 (VGluT1). To determine central projections of CGRP(+) SP(-) neurons, Neurobiotin (NB) was applied to the C7 ventral ramus and visualized in DRG and spinal cord sections colabeled for CGRP and SP. Half (50%) of the CGRP-immunoreactive DRG neurons lacked detectable SP and had a mean soma size of 473 ± 14 μm(2) (n = 5); 89% of the CGRP(+) SP(-) neurons expressed NF200 (n = 5), but only 32% expressed TRPV1 (n = 5). Cutaneous CGRP(+) SP(-) fibers were numerous within dermal papillae and around hair shafts (n = 4). CGRP(+) SP(-) boutons were prevalent in lateral lamina I and in lamina IV/V of the dorsal horn (n = 5). NB predominantly labeled fibers penetrating lamina IV/V, 6 ± 3% contained CGRP (n = 5), and 21 ± 2% contained VGluT1 (n = 3). CGRP(+) SP(-) afferent neurons are likely to be non-nociceptive. Their soma size, neurochemical profile, and peripheral and central targets suggest that CGRP(+) SP(-) neurons are polymodal mechanoceptors.

Functional organization of autonomic neural pathways

There is now abundant functional and anatomical evidence that autonomic motor pathways represent a highly organized output of the central nervous system. Simplistic notions of antagonistic all-or-none activation of sympathetic or parasympathetic pathways are clearly wrong. Sympathetic or parasympathetic pathways to specific target tissues generally can be activated tonically or phasically, depending on current physiological requirements. For example, at rest, many sympathetic pathways are tonically active, such as those limiting blood flow to the skin, inhibiting gastrointestinal tract motility and secretion, or allowing continence in the urinary bladder. Phasic parasympathetic activity can be seen in lacrimation, salivation or urination. Activity in autonomic motor pathways can be modulated by diverse sensory inputs, including the visual, auditory and vestibular systems, in addition to various functional populations of visceral afferents. Identifying the central pathways responsible for coordinated autonomic activity has made considerable progress, but much more needs to be done.

Significant increase in salivary substance p level after a single oral dose of cevimeline in humans

Cevimeline is a novel muscarinic acetylcholine receptor agonist currently being developed as a therapeutic agent for xerostomia. We examined the effects of cevimeline on salivary and plasma levels of substance-P- (SP-), calcitonin-gene-related-peptide- (CGRP-), and vasoactive-intestinal-polypeptide- (VIP-) like immunoreactive substances (ISs) in humans. An open-labeled crossover study was conducted on seven healthy volunteers. Saliva volume was measured, and saliva and venous blood samples were collected before and 30–240 min after a single oral dose of cevimeline or placebo. Salivary and plasma levels of SP-, CGRP-, and VIP-IS were measured using a highly sensitive enzyme immunoassay. A single oral dose of cevimeline resulted in significant increases in salivary but not plasma SP-IS level compared to placebo. Cevimeline administration did not alter the salivary or plasma levels of CGRP-IS or VIP-IS compared to placebo. Significant increases in salivary volume were observed after cevimeline administration compared to placebo. A significant correlation was observed between the total release of SP-IS and that of salivary volume. These findings suggest an association of SP with the enhancement of salivary secretion by cevimeline.

Effect of pilocarpine on substance P and calcitonin gene-related peptide releases correlate with salivary secretion in human saliva and plasma

WHAT IS KNOWN AND OBJECTIVE

Pilocarpine, a muscarinic receptor agonist, has been used for the treatment of dry mouth. Salivary glands are supplied with nerve fibres that contain neuropeptides, such as substance P, calcitonin gene-related peptide (CGRP) and vasoactive intestinal polypeptide (VIP), which are important modulators of salivation. It is known that measurement of salivary and plasma levels of neuropeptides is useful for assessing the dose-pharmacological effect relationship of drugs. The relationship between the action of pilocarpine and neuropeptides in humans has not been studied. Moreover, studies evaluate the usefulness of drug salivary levels in the pharmacological evaluation of drugs are scarce. The aim of this study was to examine the effects of pilocarpine on the levels of substance P-, CGRP- and VIP-like immunoreactive substances (IS) in saliva and plasma taken in healthy humans.

METHODS

Five healthy male subjects participated in this study. Pilocarpine tablet (10 mg) or placebo tablet was orally administered with 100 mL of water. Each subject was administered placebo and drug with an interval of 4 weeks in between. Saliva was sampled before and at 20, 40, 60, 90, 120, 180 and 240 min after administration of the test substances. Venous blood samples (10 mL) were also taken from a forearm vein at each time interval. The samples were then enzyme immunoassayed using a highly sensitive system for substance P-, CGRP- and VIP-IS. The amount of saliva was measured by the Saxon test.

RESULTS

A single oral administration of pilocarpine increased the release of salivary substance P-IS (the area under the concentration-time curve: AUC(0→240 min)) compared with the placebo. Pilocarpine also significantly increased the release of salivary CGRP-IS (AUC(0→240 min)). Pilocarpine significantly increased the release of plasma CGRP-IS. The salivary volume correlated with the salivary level of substance P and CGRP-IS (r = 0·84, P < 0·05 and r = 0·59, P < 0·05, respectively). AUC(0→240 min) for substance P-IS in saliva correlated with that for plasma (r = 0·78, P < 0·05).

WHAT IS NEW AND CONCLUSION

Pilocarpine increases the release of salivary substance P and CGRP-IS. This suggests that one mechanism by which pilocarpine improves dry mouth is by local stimulation of neuropeptidergic nerves. Moreover, saliva levels of substance P showed good correlation with the plasma levels. The substance P levels in saliva and plasma may be good indicators of the effects of drugs used in dry mouth/xerostomic patients.

Neurochemical classification and projection targets of CART peptide immunoreactive neurons in sensory and parasympathetic ganglia of the head

The aims of the present study were to determine if there is neuronal Cocaine and amphetamine regulated transcripts (CART) peptide expression (CART+) in parasympathetic (sphenopalatine (SPG); otic (OG)) and sensory (trigeminal (TG)) ganglia of the head and to examine the neurochemical phenotype (calcitonin gene-related peptide (CGRP), neurofilament 200 (NF200), isolectin B4 (IB4) binding, vasoactive intestinal peptide (VIP), neuropeptide Y (NPY) and enkephalin (ENK) immunoreactivity) and projection targets (lacrimal gland (LG), parotid gland (PG), nasal mucosa (NM), temporomandibular joint (TMJ), middle cerebral artery (MCA) and middle meningeal artery (MMA)) of CART expressing neurons in these ganglia. We found CART+ neurons in both the SPG (5.25±0.07%) and OG (4.32±0.66). A significant proportion of these CART+ neurons contained VIP, NPY or ENK (34%, 26% and 11%, respectively). SPG neurons retrogradely labelled from the lacrimal gland (29%) were CART+, but we were unable to demonstrate CART+ labelling in any of the SPG or OG neurons labelled from other targets. This supports a role for CART peptides in lacrimation or regulation of vascular tone in the lacrimal gland, but not in salivation or nasal congestion. CART+ neurons were also present in the trigeminal ganglion (1.26±0.38%), where their size distribution was confined almost completely to neurons smaller than 800 μm2 (mean=410 μm2; 98%<800 μm2), and were almost always CGRP+, but did not bind IB4. This is consistent with a role for CART peptides in trigeminal pain. However, there were few CART+ neurons amongst any of the trigeminal neurons retrogradely labelled from the targets we investigated and thus we cannot comment on the tissue type where such pain may have originated. Our study shows that some specialization of CART peptide expression (based on neurochemical phenotype and target projection) is evident in sensory and parasympathetic ganglia of the head.

Muscarinic acetylcholine receptor modulation of mu (mu) opioid receptors in adult rat sphenopalatine ganglion neurons

The sphenopalatine ganglion (SPG) neurons represent the parasympathetic branch of the autonomic nervous system involved in controlling cerebral blood flow. In the present study, we examined the coupling mechanism between mu (mu) opioid receptors (MOR) and muscarinic acetylcholine receptors (mAChR) with Ca(2+) channels in acutely dissociated adult rat SPG neurons. Successful MOR activation was recorded in approximately 40-45% of SPG neurons employing the whole cell variant of the patch-clamp technique. In addition, immunofluorescence assays indicated that MOR are not expressed in all SPG neurons while M(2) mAChR staining was evident in all neurons. The concentration-response relationships generated with morphine and [d-Ala2-N-Me-Phe4-Glycol5]-enkephalin (DAMGO) showed IC(50) values of 15.2 and 56.1 nM and maximal Ca(2+) current inhibition of 26.0 and 38.7%, respectively. Activation of MOR or M(2) mAChR with morphine or oxotremorine-methiodide (Oxo-M), respectively, resulted in voltage-dependent inhibition of Ca(2+) currents via coupling with Galpha(i/o) protein subunits. The acute prolonged exposure (10 min) of neurons to morphine or Oxo-M led to the homologous desensitization of MOR and M(2) mAChR, respectively. The prolonged stimulation of M(2) mAChR with Oxo-M resulted in heterologous desensitization of morphine-mediated Ca(2+) current inhibition, and was sensitive to the M(2) mAChR blocker methoctramine. On the other hand, when the neurons were exposed to morphine or DAMGO for 10 min, heterologous desensitization of M(2) mAChR was not observed. These results suggest that in rat SPG neurons activation of M(2) mAChR likely modulates opioid transmission in the brain vasculature to adequately maintain cerebral blood flow.

Skin and hair follicle innervation in experimental models: a guide for the exact and reproducible evaluation of neuronal plasticity

The remodelling of skin innervation is an instructive example of neuronal plasticity in the peripheral nervous system. Cutaneous innervation displays dramatic plasticity during morphogenesis, adult remodelling, skin diseases and after skin nerve lesions. To recognize even subtle changes or abnormalities of cutaneous innervation under different experimental conditions, it is critically important to use a quantitative approach. Here, we introduce a simple, fast and reproducible quantitative method based on immunofluorescence histochemistry for the exact quantification of peripheral nerve fibres. Computer-generated schematic representations of cutaneous innervation in defined skin compartments are presented with the aim of standardizing reports on gene and protein expression patterns. This guide should become a useful tool when screening new mouse mutants, disease models affecting innervation or mice treated with pharmaceuticals for discrete morphologic abnormalities of skin innervation in a highly reproducible and quantifiable manner. Moreover, this method can be easily transferred to other densely innervated peripheral organs.

Neurotransmitter localization in the neuroepithelial cells and unipolar neurons of the respiratory tract in the bichir, Polypterus bichir bichir G. ST-HIL

Immunohistochemical localisation of neurotransmitters was used to determine the distribution of unipolar neurons and neuroepithelial cells (NECs) in the respiratory tract of the bichir, Polypterus bichir bichir. NECs were commonly encountered in the mucociliated epithelium of the lung. Unipolar neurons were located in the submucosal and muscle layers of the glottis. The results suggest the presence of tyrosine hydroxylase (TH) and nNOS immunoreactivities in NECs. In addition, ACh-E/nNOS and TH/nNOS nerve fibers were also found associated with these cells. Unipolar neuronal cells showed a chemical code including the presence of 5-HT, ACh-E, peptides and P2x2 receptors. The present findings indicate that nitric oxide (NO) is a primitive transmitter of neuroepithelial oxygen-sensitive chemoreceptor cells together with acetylcholine. The coexistence of ACh-E with other substances in the unipolar neurons, but not with NO, may be a property of vagal postganglionic neurons since the emergence of the cranial autonomic pathways in the earliest vertebrates. It would be interesting to know about the provenance of the nerves in contact with NECs, which appear to have a complex innervation pattern.

Age-related structural and neurochemical changes of the human superior cervical ganglion

The aim of this study was to investigate age-related morphological and neurochemical changes in the human superior cervical ganglion (SCG). Thirty-seven superior sympathetic human cervical ganglia of young, adult, and aged subjects were examined using morphometric analysis, biotin-streptavidin immunohistochemistry for detecting neurofilament, myelin protein, protein gene product 9.5, nerve growth factor receptor p75 in sympathetic neurons and nerve fibers. Morphometric parameters of neurons (area, long and short axis, shape factor of the neuron body, nucleus, cytoplasm, and lipofuscin) were investigated in every sixth serial section of the ganglion. Seven hundred neurons with clearly visible nuclei were measured in each studied group. The present study showed that human SCG of older subjects had larger areas of neuron body, cytoplasm and nucleus, a lower shape factor, an increased amount of lipofuscin, and a greater number of large-size neurons, as compared to SCG obtained from young subjects. Neuronal cytoskeletal alterations manifested themselves through a decreased number of neurofilament-positive neurons were detected in old human SCG. The amount of myelinated fibers decreased with age, although the amount of myelinated fibers in the young and the adult subjects varied from few to a moderate number. PGP 9.5 immunoreactivity varied in different age groups. A marked reduction of nerve growth factor receptor p75 in old human sympathetic neurons was detected. In conclusion, the findings of this study confirm age-related morphological changes in the human SCG. Structural neuronal changes may influence the deterioration of neuronal functional capacity, neuronal plasticity, and regenerative characteristics.

Immunohistochemical study of cutaneous nerves in the emu

The distribution and chemical content of cutaneous nerves in 3- to 13-day-old emu chicks (Dromaius novaehollandiae) were examined by using double-labelling immunohistochemistry. Seven different subpopulations of cutaneous nerves were identified based on their neurochemistry. No intraepidermal nerve fibres were found. However, axons were located within the dermis and were often associated with blood vessels, pennamotor muscles and feather follicles or innervated Herbst corpuscles. Both similarities and differences exist between subpopulations of cutaneous nerves in the emu and volant birds. As in volant birds, a subpopulation of cutaneous axons innervates the superficial skin layers and contains immunoreactivity to both substance P and calcitonin gene-related peptide (CGRP). This suggests that the neuropeptide content of these presumptive free nerve endings is conserved throughout the evolution of birds. In contrast, Herbst corpuscles in the emu are innervated by axons that contain immunoreactivity for CGRP or neuropeptide Y (NPY) but that lack the calbindin D-28k immunoreactivity found in fibres innervating Herbst corpuscles of volant birds. Herbst corpuscles therefore may have a different chemical content in a flightless species from that in volant birds.

Quantitative immunohistochemical investigation of the intrinsic vasodilator innervation of the guinea pig lingual artery

The vasculature of the guinea pig tongue is supplied by parasympathetic vasodilator nerve fibres of intrinsic origin. Here, we investigated first to what extent neuropeptides and the synthesizing enzymes of NO, CO and acetylcholine are contained and colocalized within periarterial lingual vasodilator axons of intrinsic origin. Then it was determined whether perivascular innervation by these fibre types changes with vascular diameter, in particular in comparison with the sensory substance P (SP)-positive and sympathetic noradrenergic vascular innervation. To this end, single, double and triple labelling histochemical techniques were performed on control tongues and tongues kept in short-term organotypic culture to induce degeneration of extrinsically originating nerve fibres. Cell bodies of intrinsic microganglia and their periarterial axons contained, simultaneously, NO synthase, vasoactive intestinal peptide and the acetylcholine-synthesizing enzyme choline acetyltransferase. Additionally, neuropeptide Y (NPY) was observed in a small percentage (12%) of neurons that increased to 39% after 36 h of organotypic culture. The CO synthesizing enzyme heme oxygenase-2 was detected only in perikarya but not in periarterial axons. Intrinsic vasodilator fibres were invariably present at arteries down to a luminal diameter of 150 microm, and reached 65% of section profiles of smallest arterioles, while noradrenergic and substance P-positive axons reached 80% of arteriolar profiles. These findings show that the intrinsic lingual vasodilator innervation of the guinea pig is far extending although slightly less developed than that by sensory and sympathetic axons, and differs both in this aspect and in patterns of colocalization from that reported for other organs, e.g. lung and pelvic organs.

Expression of immunoreactivity to neurokinin-1 receptor by subsets of cranial parasympathetic neurons: correlation with neuropeptides, nitric oxide synthase, and pathways

We examined the patterns of coexistence of immunoreactivity to the neurokinin-1 (NK(1)) tachykinin receptor, nitric oxide synthase, and neuropeptides in the sphenopalatine and otic ganglia of guinea pigs using a combination of multiple-labeling immunohistochemistry and pathway tracing in vitro. Most neurons had immunoreactivity to vasoactive intestinal peptide (85-96%) and neuropeptide Y (60%). Subpopulations of vasoactive intestinal peptide-immunoreactive neurons also had immunoreactivity to nitric oxide synthase (37-48%) or enkephalin (25-35%), but these formed mutually exclusive populations. Almost all neurons expressing NK(1) receptor immunoreactivity contained immunoreactivity to enkephalin, vasoactive intestinal peptide, and neuropeptide Y, but not nitric oxide synthase. Using a combination of retrograde axonal tracing and axonal crushing, we found that most neurons with immunoreactivity to nitric oxide synthase projected along the nasopalatine and ethmoidal nerves to the nasal mucosa. In contrast, most neurons with immunoreactivity to enkephalin followed the zygomatic nerve to the facial skin and lacrimal gland. Based on their peptide content, we conclude that the neurons with immunoreactivity to enkephalin and NK(1) receptor projected selectively to the skin. In both the sphenopalatine and the otic ganglia, about half of the neurons with NK(1) receptor immunoreactivity were surrounded by varicose nerve fibers with substance P immunoreactivity. Many of these fibers are likely to have originated in the trigeminal ganglion. Taken together, these observations establish a strong anatomical basis for a range of interactions between trigeminal and cranial parasympathetic pathways that may underlie pathophysiological conditions such as trigeminal neuralgia.

Selective projections of cholecystokinin-8 immunoreactive fibers to galanin immunoreactive sympathetic preganglionic neurons in a teleost, Stephanolepis cirrhifer

In the cellular column of sympathetic preganglionic neurons (SPNs) of the filefish Stephanolepis cirrhifer, neurons containing galanin (GAL) form a distinct population projecting specifically to non-adrenergic postganglionic neurons in the celiac and cranial sympathetic ganglia. The present study showed that virtually all of the GAL-immunopositive SPNs made contact with many nerve terminals immunopositive for cholecystokinin octapeptide (CCK-8). GAL-negative preganglionic neurons made contact with only 26% of this type of nerve terminal; CCK-8-immunopositive nerve fibers appeared to project selectively to GAL-immunopositive SPNs with projections to specific targets. The CCK-8-positive nerve fibers might be of primary sensory origin, and participate in the visceral reflexes.

Changes in the expression of neuropeptide Y (NPY) during maturation of human sympathetic ganglionic neurons: correlations with tyrosine hydroxylase immunoreactivity

Developmental patterns of neuropeptide Y (NPY) and tyrosine hydroxylase (TH)-immunoreactivities (IR) were investigated using the method of indirect immunohistochemistry in the stellate and thoracic sympathetic ganglia of human neonates ranging in gestational age from 24 to 27 weeks (premature group) and from 38 to 41 weeks (mature group). In the paravertebral ganglia of premature neonates a small (up to 7%) population of NPY-IR nerve cells was revealed. With the gestational age increase (a mature group), a marked elevation of the number of NPY-IR ganglionic neurons (up to 41%) was noted. In contrast, in the sympathetic ganglia of premature neonates almost all the neurons were tyrosine hydroxylase immunoreactive and any change in pattern during maturation was insignificant. The results demonstrate an age-related increase of neuropeptide Y-immunoreactivity in human paravertebral ganglia during maturation, and suggest that peptidergic co-transmission arises later in development than do the classical autonomic messengers. Adaptability of the fetus to a new external environment at birth demands a qualitatively new activity level of the autonomic nervous system, and this is provided side by side with the classical messengers noradrenaline and acetylcholine by the co-transmitter and modulating role of the neuropeptides. The appearance of neuropeptide Y in the principal sympathetic ganglionic neurons defines not only a qualitatively new level in the functional regulation of target organs at birth, but serves as an index of neonatal maturity.

Pathway specific expression of neuropeptides and autonomic control of the vasculature

In this article, we review the immunohistochemical evidence for the pathway-specific expression of co-existing neuropeptides in autonomic vasomotor neurons, and examine the functional significance of these expression patterns for the autonomic regulation of the vasculature. Most final motor neurons in autonomic vasomotor pathways contain neuropeptides in addition to non-peptide co-transmitters such as catecholamines, acetylcholine and nitric oxide. Neuropeptides also occur in preganglionic vasomotor neurons. The precise combinations of neuropeptides expressed by neurons in vasomotor pathways vary with species, vascular bed, and the level within the vascular bed. This applies to both vasoconstrictor and vasodilator pathways. There is a similar degree of variation in the expression of neuropeptide receptors in the vasculature. Consequently, the contributions of different peptides to autonomic vasomotor control are closely matched to the functional requirements of specific vascular beds. This arrangement allows for a high degree of precision in vascular control in normal conditions and has the potential for considerable plasticity under pathophysiological conditions.

Hair cycle-dependent changes in adrenergic skin innervation, and hair growth modulation by adrenergic drugs

Skin nerves may exert "trophic" functions during hair follicle development, growth, and/or cycling. Here, we demonstrate hair cycle-related plasticity in the sympathetic innervation of skin and hair follicle in C57BL/6 mice. Compared with telogen skin, the number of nerve fibers containing norepinephrine or immunoreactive for tyrosine hydroxylase increased during the early growth phase of the hair cycle (anagen) in dermis and subcutis. The number of these fibers declined again during late anagen. beta2-adrenoreceptor-positive keratinocytes were transiently detectable in the noncycling hair follicle epithelium, especially in the isthmus and bulge region, but only during early anagen. In early anagen skin organ culture, the beta2-adrenoreceptor agonist isoproterenol promoted hair cycle progression from anagen III to anagen IV. The observed hair cycle-dependent changes in adrenergic skin innervation on the one hand, and hair growth modulation by isoproterenol, accompanied by changes in beta2-adrenoreceptor expression of selected regions of the hair follicle epithelium on the other, further support the concept that bi-directional interactions between the hair follicle and its innervation play a part in hair growth control. This invites one to systematically explore the neuropharmacologic manipulation of follicular neuroepithelial interactions as a novel therapeutic strategy for managing hair growth disorders.

Immunohistochemical demonstration of neuropeptides in the articular disk of the human temporomandibular joint

The distribution of calcitonin gene-related peptide (CGRP), substance P (SP), vasoactive intestinal polypeptide (VIP) and neuropeptide Y (NPY) was examined in the human temporomandibular articular disk using an indirect immunofluorescent method. All examined neuropeptides were observed in nerve fibers in the disk. These fibers were mostly located in the loose fibrous tissue of the posterior part (posterior attachment) and in the lateral region of the anterior part (anterolateral loose fibrous tissue) of the disk. The posterior attachment and anterolateral loose fibrous tissue occasionally contained isolated nerve fibers which usually showed immunoreactivity (IR) for CGRP or SP. In this tissue, perivascular fibers contained VIP or NPY, whereas isolated fibers and free nerve endings showed the IR for CGRP or SP. These neuropeptides may be involved in the regulation of blood flow and/or pain sensation in the human articular disk of the temporomandibular joint.

Vasoactive intestinal polypeptide (VIP) innervation of the human eyelid glands

This study was conducted to obtain morphological proof of innervating nerve fibres in the glands of the human eyelid (accessory lacrimal glands of Wolfring, meibomian glands, goblet cells, glands of Zeis, glands of Moll, sweat glands, glands of lanugo hair follicles) and identification of the secretomotorically active neuropeptide vasoactive intestinal polypeptide (VIP) as a common transmitter. Epoxy-embedded ultrathin sections of tissue samples from human eyelids were studied using electron microscopy. Paraffin sections fixed in Bouin-Hollande solution were immunostained with rabbit antiserum against VIP. With the electron microscope we were able to identify nerves in the glandular stroma of all the glands examined with the exception of goblet cells. Intraepithelial single axons were only seen in the parenchyma of Wolfring glands. The morphological findings corresponded with the immunological finding of VIP-positive, nerve-like structures in the same locations, with the exception of lanugo hair follicle glands, and goblet cells. Our findings indicate that the glands of the eyelids and main lacrimal gland represent a functional unit with VIP as a possible common stimulating factor.

The influence of sensory stimulation (acupuncture) on the release of neuropeptides in the saliva of healthy subjects

In recent studies we have shown that xerostomia (dry mouth) can be treated successfully with sensory stimulation (acupuncture). The increase of saliva secretion lasted often for at least one year. Some neuropeptides have been found to influence the secretion of saliva. The aim of this study was to investigate the mechanisms behind the effect of acupuncture on salivary secretion by measuring the release of neuropeptides in saliva under the influence of sensory stimulation. VIP-like immunoreactivity (VIP-LI), NPY-LI, SP-LI, CGRP-LI and NKA-LI were analysed in the saliva of eight healthy subjects. Manual acupuncture and acupuncture with low-frequency electrical stimulation (2 Hz) were used. The saliva was collected during 20 minutes before the start of acupuncture stimulation, then during 20 minutes while the needles were in situ and then for another 20 minutes after the needles were removed. Four different saliva sampling techniques were used: whole resting saliva, whole saliva stimulated by paraffin-chewing, whole saliva stimulated by citric acid (1%), and parotid saliva, also stimulated with citric acid (1%). The results showed significant increases in the release of CGRP, NPY and VIP both during and after acupuncture stimulation, especially in connection with electro-acupuncture. SP showed only few increases, mainly in connection with electro-acupuncture, whereas NKA generally was unaffected by the acupuncture stimulation. The sensory stimulation-induced increase in the release of CGRP, NPY and VIP in the saliva could be an indication of their role in the improvement of salivary flow rates in xerostomic patients who had been treated with acupuncture.

Differential distribution of substance P binding sites in guinea-pig sympathetic ganglia

We have used a combination of autoradiographic and immunohistochemical techniques to investigate the distribution of binding sites for substance P in relation to the distribution of substance P-immunoreactive nerve fibres and specific functional populations of neurons in the sympathetic ganglia of guinea-pigs. There was considerable heterogeneity in the density of binding sites for Bolton Hunter labelled 125I - substance P (BHSP). Binding sites were more dense in the prevertebral ganglia, such as the coeliac and inferior mesenteric ganglia, than in the paravertebral ganglia, such as the superior cervical or lumbar chain ganglia. The binding sites tended to be clumped within the ganglia. Within the prevertebral ganglia, they were associated predominantly with neurons projecting to the enteric plexuses. Many of these neurons contained somatostatin immunoreactivity. In the lumbar sympathetic chain ganglia, there was a weak association of binding sites with neurons containing immunoreactivity to vasoactive intestinal peptide. Overall, the density of binding sites matched the density of nerve fibres containing immunoreactivity to substance P in different ganglia. However, within particular ganglia, there was little, if any, correlation between the distribution of binding sites and nerve fibres containing substance P. Most of the binding sites in the ganglia had the pharmacological characteristics of NK1 receptors. Our results show that there is considerable heterogeneity in the expression of NK1 receptors in the sympathetic ganglia of guinea-pigs. However, given the relatively poor spatial correlation between the distribution of binding sites and potential sites of substance P release from intraganglionic nerve fibres, we suggest that substance P may diffuse for relatively large distances through the ganglia, with actions only on those neurons selectively expressing NK1 receptors.

Plasticity in adult and ageing sympathetic neurons

The nature of neural plasticity and the factors that influence it vary throughout life. Adult neurons undergo extensive and continual adaptation in response to demands that are quite different from those of early development. We review the main influences on the survival, growth and neurotransmitter expression in adult and ageing sympathetic neurons, comparing these influences to those at work in early development. This "developmental" approach is proposed because, despite the contrasting needs of different phases of development, each phase has a profound influence on the mechanisms of plasticity available to its successors. Interactions between neurons and their targets, whether effector cells or other neurons, are vital to all of these aspects of neural plasticity. Sympathetic neurons require access to target-derived diffusible neurotrophic factors such as NGF, NT3 and GDNF, as well as to bound elements of the extracellular matrix such as laminin. These factors probably influence plasticity throughout life. In adult life, and even in old age, sympathetic neurons are relatively resistant to cell death. However, they continue to require target-derived diffusible and bound factors for their maintenance, growth and neurotransmitter expression. Failure to maintain appropriate neuronal function in old age, for example in the breakdown of homeostasis, may result partly from a disturbance of the dynamic, trophic relationship between neurons and their targets. However, there is no clear evidence that this is due to a failure of targets to synthesize neurotrophic factors. On the neural side of the equation, altered responsiveness of sympathetic neurons to neurotrophic factors suggests that expression of the trk and p75 neurotrophin receptors contributes to neuronal survival, maintenance and growth in adulthood and old age. Altered receptor expression may therefore underlie the selective vulnerability of some sympathetic neurons in old age. The role of neural connectivity and activity in the regulation of synthesis of target-derived factors, as well as in neurotransmitter dynamics, is reviewed.

Histamine-induced internalization of substance P receptors in myoepithelial cells of the guinea pig nasal glands

Numerous substance P (SP) immunoreactive nerve fibers were located around submucosal glands in the guinea pig nasal mucosa. Since these SP positive nerve fibers were also positive for vasoactive intestinal polypeptide, and to a lessor extent for neuropeptide Y, they were presumed to be parasympathetic fibers. SP receptor positive structures were observed exclusively on the membrane of myoepithelial cells in normal nasal mucosa, suggesting that myoepithelial cells are targets of SP positive fibers. SP receptor-like immunoreactivity was observed associated with intracellular organella of myoepithelial cells 5 min after intranasal histamine challenge, which may indicate the molecular basis for histamine-induced nasal discharge.

Parasympathetic innervation of cephalic arteries in rabbits: comparison with sympathetic and sensory innervation

We investigated the distribution of parasympathetic, sympathetic, and sensory perivascular nerve fibers in rabbit cephalic arteries supplying the brain, exocrine glands, nasal mucosa, masseter muscles, tongue, and skin in the face and also examined cranial autonomic and sensory ganglia. NADPH diaphorase (NADPHd)-positive and vasoactive intestinal peptide-like immunoreactive (VIP-LI) neurons were located in the cranial parasympathetic ganglia. Neuropeptide Y (NPY)-LI neurons occurred mainly, and dopamine beta-hydroxylase (DBH)-LI neurons occurred exclusively, in the superior cervical (sympathetic) ganglion. Substance P (SP)-LI and calcitonin gene-related peptide (CGRP)-LI neurons occurred only in the trigeminal (sensory) ganglion. Therefore, it was assumed that NADPHd-positive and VIP-LI perivascular nerve fibers in cephalic arteries were parasympathetic, all DBH-LI and most NPY-LI fibers were sympathetic, and SP-LI and CGRP-LI fibers were sensory in nature. In the cerebral arteries, NADPHd-positive and VIP-LI varicose fibers were more numerous in the rostral than in the caudal half of the Circle of Willis. In the extracranial arteries, NADPHd-positive and VIP-LI fibers were most abundant in the lingual, lacrimal, and supraorbital arteries; sparse in the parotid and submandibular arteries; and absent in the ear artery. There was an obvious proximal-to-distal density gradient along individual cephalic arterial trees. In contrast, DBH-LI, NPY-LI, SP-LI, and CGRP-LI varicose nerve fibers were similar in density in all cephalic arteries and their branches. These neuroanatomical findings suggest that differential parasympathetic innervation in cephalic arteries may play a role in the partitioning of blood flow between different cephalic tissues.

Selective innervation of different target tissues in guinea-pig cranial exocrine glands by sub-populations of parasympathetic and sympathetic neurons

This study has used multiple-labelling immunohistochemistry and quantitative analysis to examine the projections of subpopulations of parasympathetic and sympathetic neurons to different vascular and secretory structures in five cranial exocrine glands of guinea-pigs. Multiple subpopulations of parasympathetic axons, identified by immunoreactivity (IR) for various combinations of peptides, innervated arteries, arterioles, ducts and acini in sublingual, submandibular, parotid, lacrimal and zygomatic glands, although axons were absent from ducts in the parotid gland. Most parasympathetic axons contained IR for vasoactive intestinal peptide (VIP) and neuropeptide Y (NPY), with or without enkephalin (Enk). The proportion of parasympathetic axons that contained Enk-IR varied greatly between target tissues and glands: Enk-IR was more common in axons supplying secretory ducts, acini and arterioles than in axons innervating more proximal arteries; Enk-IR was less common in axons supplying the lacrimal gland than axons supplying the submandibular, lacrimal and zygomatic glands. Sympathetic axons with IR for tyrosine hydroxylase (TH) innervated arterial vessels in all glands, but innervated secretory structures only in the salivary glands. Sympathetic axons supplying proximal arterial segments often contained NPY-IR and sometimes also contained IR for dynorphin. Dynorphin-IR was more common in axons in the parotid, lacrimal and zygomatic glands than in the sublingual and submandibular glands. In contrast, axons supplying arterioles, ducts and acini lacked peptide IR. These results indicate that neuronal pathways regulating proximal arteries in cranial exocrine glands are different from the neuronal pathways regulating arterioles and acini, and may be different from neurons projecting to proximal secretory ducts. Furthermore, the peptides enkephalin, NPY and dynorphin are likely to make variable contributions to autonomic neurotransmission in different arterial segments and in different cranial exocrine glands.

Adenovirus infection of the cornea causes histopathologic changes in the lacrimal gland

PURPOSE

To explore the effects on the lacrimal gland of adenovirus infection of the cornea.

METHODS

Rabbit corneas were inoculated with human adenoviruses Ad5, Ad14, or a rabbit adapted form of Ad 5, and in some instances booster inoculations were given. Sections of lacrimal glands removed 21-59 days post-inoculation were immunostained using antibodies against rabbit Class I and Class II MHC molecules, CD4, CD8, CD18, and rabbit thymic lymphocyte antigen (RTLA). Relative numbers of positively stained cells were quantified with a Metamorph image analysis system.

RESULTS

RTLA and CD18 antigens were expressed on many interstitial cells in the normal lacrimal gland, but few expressed CD4 or CD8. The number of RTLA+ cells increased by 60-100% after inoculation of Ad5 and after boosting, and CD18+ cells increased from 33-100% after inoculation of Ad5 and after boosting. Booster inoculations also caused focal lymphocytic infiltration. MHC Class I was expressed on interstitial cells and duct epithelium, but not acinar cells, and there was no detectable difference after viral infection. In controls, MHC Class II was localized to a population of interstitial cells and a few acinar cells. A single inoculation of the Ad5 virus did not result in an increase in the total number of MHC Class II-positive cells at 21 days, but inoculation with the rabbit-adapted Ad 5 and booster inoculations caused a 30% increase.

CONCLUSIONS

Ad5 and rabbit-adapted Ad5 infection of the cornea induce lymphocytic infiltration in the lacrimal gland, and the effect is enhanced by boosting. There is also an increase in expression of MHC Class II after inoculation with rabbit-adapted Ad5 and with booster inoculations.

Distribution pattern of nervous tissue and peptidergic nerve fibers in accessory lacrimal glands

PURPOSE

Demonstration of the distribution pattern of nervous tissue and the occurrence of neuropept human accessory lacrimal glands by means of immunohistochemical methods.

METHODS

Paraffin sections of tissue samples were incubated with antisera against protein gene product (PGP), S-100 protein (S-100), calcitonin gene-related peptide (CGRP) and substance P (SP). The immunoreactions were visualized using both species-specific secondary antibodies and a streptavidin-biotin-peroxidase complex (ABC method).

RESULTS

PGP- and S-100-immunoreactive nerve fibers were distributed in the entire intertubular stroma. In addition, myoepithelial cells, a few clusters of tubulus cells, groups of wandering cells, and scattered cells of the excretory duct system were S-100-immunoreactive. CGRP- and SP-immunoreactivity was found in a few nerve fibers in the intertubular glandular stroma with an association to secretory tubules, blood vessels, intralobular ducts and excretory duct.

CONCLUSIONS

These observations are in agreement with findings in the main lacrimal gland.

Neuropeptides in the saliva of healthy subjects

Five neuropeptides: Substance P (SP), Neurokinin A (NKA), Calcitonin Gene-Related Peptide (CGRP), Neuropeptide Y (NPY) and Vasoactive Intestinal Polypeptide (VIP), were measured in the saliva of eight subjects. The saliva was collected using different stimulation techniques: whole resting saliva, whole paraffin stimulated saliva, whole citric acid stimulated saliva and parotid saliva of different secretion rates -0.25 mL/min, 0.50 mL/min and 1.00 mL/min, also stimulated by citric acid. The neuropeptides were analysed by radioimmunoassay. The results showed that the concentration of all neuropeptides decreased significantly, two- to four-fold (CGRP up to 16-fold) in whole saliva, when the salivary secretion rates increased six- to eight-fold due to stimulation. However, the amounts of all neuropeptides released over time into the whole saliva increased two- to five-fold (ten-fold for CGRP) as the volumes of saliva increased due to chewing-stimulation as compared to resting saliva or citric acid stimulated saliva. There was also more CGRP in the resting saliva than in the citric acid stimulated saliva. The concentration of CGRP in the parotid saliva decreased three- to ten-fold when the salivary flow increased, whereas the concentration of NKA increased three- to four-fold and that of NPY almost two-fold under the same conditions. The concentrations of SP and VIP did not change in the different flows of parotid saliva. The release of all neuropeptides in the parotid saliva over time showed significant increases (3-14-fold) when the secretion rates increased except CGRP, which showed no changes at all. We concluded that neuropeptides are continuously released into the saliva. Their amounts increase with stimulation, but they are diluted by the increased volume of saliva, and they are also affected by the mode of stimulation-muscular activity leads to a greater release than citric acid stimulation. As the neuropeptides play an important role in the control of salivary secretory mechanisms, their normal occurrence and release are of fundamental importance for the understanding of the function of the salivary glands.

Tachykinins in the gut. Part II. Roles in neural excitation, secretion and inflammation

The preprotachykinin-A gene-derived peptides substance (substance P; SP) and neurokinin (NK) A are expressed in intrinsic enteric neurons, which supply all layers of the gut, and extrinsic primary afferent nerve fibers, which innervate primarily the arterial vascular system. The actions of tachykinins on the digestive effector systems are mediated by three different types of tachykinin receptor, termed NK1, NK2 and NK3 receptors. Within the enteric nervous system, SP and NKA are likely to mediate, or comediate, slow synaptic transmission and to modulate neuronal excitability via stimulation of NK3 and NK1 receptors. In the intestinal mucosa, tachykinins cause net secretion of fluid and electrolytes, and it appears as if SP and NKA play a messenger role in intramural secretory reflex pathways. Secretory processes in the salivary glands and pancreas are likewise influenced by tachykinins. The gastrointestinal arterial system may be dilated or constricted by tachykinins, whereas constriction and an increase in the vascular permeability are the only effects seen in the venous system. Various gastrointestinal disorders are associated with distinct changes in the tachykinin system, and there is increasing evidence that tachykinins participate in the hypersecretory, vascular and immunological disturbances associated with infection and inflammatory bowel disease. In a therapeutic perspective, it would seem conceivable that tachykinin antagonists could be exploited as antidiarrheal, antiinflammatory and antinociceptive drugs.

Autonomic and sensory innervation of cat molar gland and blood vessels in the lower lip, gingiva and cheek

Innervation of the molar gland and blood vessels in the lower lip, gingiva and cheek mucous membrane was investigated in the cat with the aid of whole mount acetylthiocholinesterase (WATChE) histochemistry and retrograde neuronal tracing methods with horseradish peroxidase (HRP) and HRP-conjugated wheat germ agglutinin (WGA-HRP). The molar gland was found to be supplied from the buccal nerve and branches of the mylohyoid nerve on the basis of microdissection of WATChE-stained mandibular preparations under a dissecting microscope. The rostral half of the lower lip-gingiva was innervated by mental branches from the inferior alveolar nerve. The caudal half of the lower lip-gingiva and cheek mucous membrane were observed to be supplied from the buccal nerve. Following injections of HRP/WGA-HRP into the molar gland, lower lip-gingiva and cheek, many retrogradely labeled ganglion neurons were observed in the ipsilateral main and accessory otic ganglia, superior cervical ganglion and mandibular division of the trigeminal ganglion. In the pterygopalatine ganglion, a small number of positive neurons were found, but in a few cases in which the injected tracer was restricted to the lower lip-gingiva and anterior half of the molar gland, labeled neurons were not detected in the main ganglion nor in its accessory microganglia. These findings indicate that the cat molar gland receives a postganglionic parasympathetic supply from the otic ganglia, postganglionic sympathetic input from the superior cervical ganglion and sensory innervation from the trigeminal ganglion by way of the buccal nerve and mylohyoid nerve. Vessels in the rostral half of the lower lip-gingiva receive the same inputs from the inferior alveolar nerve, and vessels in the caudal half receive inputs from the buccal nerve. The vessels in the cheek mucous membrane receive dual parasympathetic supplies from the otic ganglia and the pterygopalatine ganglion by way of the buccal nerve.

Direct evidence of parasympathetic vasodilatation in cat periodontal ligament

Sympathetic regulation of periodontal ligament blood flow (PLBF) is well-attested; however, vasodilator responses mediated by parasympathetic nerve fibers have yet to be conclusively demonstrated in the periodontal ligament (PL). The present study was designed to determine whether parasympathetic vasodilator mechanisms do or do not exist in the cat PL. In our cats, the cervical sympathetic trunks were sectioned bilaterally prior to any stimulation in order to eliminate sympathetic effects on the vascular beds under study. Dynamic changes in PLBF, with mandibular lip blood flow (LBF) recorded for comparison, were investigated in cat mandibular canine teeth using laser Doppler flowmetry. The peripheral cut ends of the facial and glossopharyngeal nerve roots, which have been reported to contain parasympathetic nerve fibers to the oral tissues, were electrically stimulated intracranially. Such stimulation caused blood flow to increase in the ipsilateral PL and lip, without an increase in systemic blood pressure. These vasodilator responses in the PL and lip were sensitive to ganglion blockade (with hexamethonium), indicating vasodilation via activation of parasympathetic vasodilator fibers. In contrast, although intracranial stimulation of the trigeminal nerve root also induced increases in both PLBF and LBF, these were unaffected by hexamethonium, but reduced by tripelennamine, indicating antidromic vasodilatation via the trigeminal sensory nerve. These results suggest that parasympathetic vasodilator mechanisms do exist in feline PL.

Protein gene product 9.5-immunoreactive nerves and cells in human oral mucosa

BACKGROUND

Current conflicting information on the innervation of the human oral cavity indicates technical problems such as different detectability of the neural structures according to the various staining methods used and difficulties in reproducibility. The possibility of intraoral regional differences has not been properly considered.

METHODS

Human biopsies of mucosa from different intraoral regions were prepared for immunohistochemistry using protein gene product 9.5 (PGP 9.5; a marker for neuronal structures).

RESULTS

Nerves were found consistently in all the biopsies. The neural pattern showed clear regional differences. Intraepithelial nerve fibers were found in the gingiva, labia, palate, within certain fungiform papillae, and in some salivary excretory ducts. Organized nerve endings were found in varying frequencies in all but one (sublingual) region, appearing as lamellar (Meissner-like), coiled or glomerular neural structures. Merkel cell-neurite complexes were observed in the buccal, gingival, and palatal epithelia. Immunoreactive cells with many similarities to Merkel cells but without a neural connection were also encountered.

CONCLUSIONS

Conflicting results from earlier innervation studies of the oral cavity could be attributed to regional innervation differences. The distribution of the nerves also casts doubt on some of the present theories concerning the function(s) of intraoral nerves, such as the free nerve endings and the Merkel cell-neurite complexes.

Differential distribution of neuronal markers and neuropeptides in the human lacrimal gland

BACKGROUND

The present study was undertaken in an attempt to broaden the spectrum of known neuronal markers and neuropeptides in the main lacrimal gland of the human by light-microscopic immunohistochemistry.

METHODS

Using antisera against the neuronal markers protein gene product (PGP) and S-100 protein (S-100), the distribution of nerve fibers in the human main lacrimal gland was studied. Vasoactive intestinal polypeptide (VIP), calcitonin gene-related peptide (CGRP), neuropeptide Y (NPY) and tyrosine hydroxylase (TH) were identified by their specific antisera.

RESULTS

The nerve fibers are distributed throughout the interstice between the glandular tubules. Associations were also found between nerve fibers and both the interlobular ductal system and blood vessels (mainly arterioles). Within the glandular lobules isolated groups of secretory cells stained positive for S-100 protein. Nerve fibers situated in the glandular interstice between the tubules showed predominantly positive immunoreactions for the neuropeptide VIP, while only very few fibers stained positive for CGRP, NPY and the catecholamine marker TH. Nerve fibers associated with interlobular blood vessels were mainly CGRP and NPY positive and stained only very rarely for VIP. The epithelia of interlobular ducts and excretory ducts were associated with CGRP-immunoreactive nerve fibers.

CONCLUSION

The neuropeptides identified in the lacrimal gland indicate the complexity with which a variety of biologic signals regulate and modulate the lacrimal gland.

Projections of intrinsic cardiac neurons to different targets in the guinea-pig heart

We set out to determine the projections of the major immunohistochemically-defined populations of intrinsic cardiac neurons to different target tissues within the guinea-pig heart. Ultrastructural studies, and immunoreactivity to the neuronal marker, neuron-specific enolase, suggested that the number of axons of intrinsic neurons in most regions of the heart was low when compared with the populations of axons projecting from extrinsic sensory and sympathetic ganglia. Multiple-labelling immunofluorescence was used to demonstrate the terminals of the major populations of peptide-containing intrinsic neurons. The intrinsic nature of peptide-containing axons was confirmed by long-term organotypic culture of cardiac tissue, which resulted in degeneration of axons of extrinsic neurons. The relative density and peptide content of intrinsic axons throughout the heart was not consistent with the relative proportions of peptide-containing intracardiac nerve cell bodies observed previously. The most commonly-encountered axons contained immunoreactivity (IR) to vasoactive intestinal peptide (VIP) alone, although nerve cell bodies with VIP constituted less than 5% of the total population of intrinsic neurons. Populations of axons containing IR to somatostatin alone, somatostatin and substance P, neuropeptide Y (NPY) alone, somatostatin and NPY, or VIP and NPY, also were observed. Intrinsic axons containing substance P-IR were very rare, much more so than would be predicted from the peptide content of intrinsic nerve cell bodies. The regions of the heart with the most dense innervation by axons of intrinsic neurons were the cardiac valves, the atrio-ventricular node and the sino-atrial node. Each of these targets was innervated by several populations of peptide-containing axons. Thus, each population of peptide-containing intrinsic neurons projected to a variety of target tissues within the heart. One possible interpretation of these results is that immunohistochemically-distinct populations of intrinsic neurons belong to different functional classes of neurons (sensory neurons, interneurons, final motor neurons), each of which innervates many regions of the heart.

Absence of parasympathetic vasodilatation in cat dental pulp

The existence and nature of parasympathetic nerve fibers in the dental pulp have long been a subject for discussion; indeed, vasodilator responses mediated by such nerve fibers have yet to be conclusively demonstrated in the dental pulp. This study was designed to determine whether parasympathetic vasodilator mechanisms do or do not exist in the cat dental pulp. Dynamic changes in pulpal blood flow (PBF), with mandibular lip blood flow (LBF) recorded as a control, were investigated in cat mandibular canine teeth by means of laser Doppler velocimetry. Peripheral trigeminal afferents (see below) were stimulated electrically to confirm that somato-parasympathetic reflex vasodilatation could be induced. The peripheral cut ends of the facial and glossopharyngeal nerve roots, which have been reported to contain parasympathetic nerve fibers to the oral tissues, were then stimulated intracranially. Electrical stimulation of trigeminal afferents (in the infraorbital nerve or the maxillary buccal gingiva) caused no change in PBF but did increase ipsilateral LBF. Neither facial nor glossopharyngeal nerve root stimulation caused a PBF increase, though both elicited increases in ipsilateral LBF. The vasodilator responses in the lip were sensitive to ganglion blockade (with hexamethonium), indicating vasodilatation via activation of parasympathetic vasodilator fibers. In contrast, intracranial stimulation of the trigeminal nerve root induced increases in both PBF and LBF which were reduced by pre-treatment with tripelennamine, indicating antidromic vasodilatation via the trigeminal sensory nerve. These results suggest that a parasympathetic vasodilator mechanism is not present in feline dental pulp.

Immunohistochemical correlation of human adrenal nerve fibres and thoracic dorsal root neurons with special reference to substance P

Applying a double-labelling immunofluorescence technique, six types of substance P-containing nerve fibres were distinguished in the human adrenal gland according to the immunohistochemical colocalization of (I) calcitonin gene-related peptide (CGRP), (II) cholecystokinin, (III) nitric oxide synthase, (IV) dynorphin, (V) somatostatin, and (VI) vasoactive intestinal polypeptide. Fibre populations I to IV in their mediator content resembled the respective subpopulations of primary sensory neurons in human thoracic dorsal root ganglia, while populations V and VI revealed no correspondence with dorsal root neurochemical coding. Nerve fibres with the combination substance P/nitric oxide synthase occurred only in the adrenal cortex, whereas all other fibre types were present in both cortex and medulla. As revealed by immuno-electron microscopy, substance P-immunolabelled axon varicosities (a) exhibited synaptic contacts with medullary chromaffin cells or with neuronal dendrites, (b) were directly apposed to cortical steroid cells and (c) were separated from fenestrated capillaries only by the interstitial space. These findings provide immunochemical support for an assumed sensory innervation of the human adrenal gland, and additionally suggest participation of substance P in efferent autonomic pathways. Furthermore, the results are indicative for a differentiated involvement of substance P in the direct and indirect regulation of neuroneuronal and neuroendocrine interactions.

Distribution of neurons reactive for NADPH-diaphorase in the branchial nerves of a teleost fish, Gadus morhua

The NADPH-diaphorase reaction was used to determine the distribution of postganglionic autonomic neurons in the branches of the glossopharyngeal and vagus nerves supplying the gill arches of the cod fish, Gadus morhua. Neurons were common in major nerve trunks in all gill arches, especially in the post-trematic rami of the branchial nerves. From about 55% to more than 85% of the neurons in any branchial nerve were reactive for NADPH-diaphorase. The results suggest that the presence of NADPH-diaphorase, and presumably the ability to synthesise nitric oxide, have been a property of cranial parasympathetic neurons from early in the evolution of the vertebrates.

Innervation of cutaneous structures in the mouse hind paw: a confocal microscopy immunohistochemical study

The normal innervation of structures in mouse foot pads was investigated with immunohistochemistry and confocal microscopy. Nerves were visualized by incubating Zamboni fixed, thick, frozen sections with antibodies to protein gene product 9.5 (PGP 9.5), vasoactive intestinal peptide, substance P, calcitonin gene-related peptide, and protein zero. The antibodies were localized using cyanine 3.18 labeled anti-rabbit gamma globulin. PGP 9.5 immunolocalization showed dense nerve bundles at the base of the foot pad with branches to larger blood vessels, sweat glands and epidermis. Sweat gland tubules were surrounded by numerous sudomotor axons; single fibers accompanied the sweat duct toward the skin's surface. Nerve bundles containing myelinated and unmyelinated axons ran through and around the centrally located sweat gland cluster to end in free nerve endings and Meissner's-like corpuscles at the apex of the foot pad. Other bundles running parallel to the epidermis gave arcuate branches that supplied epidermis on the sides of the pads with a rich nerve network, principally with free nerve endings that often reached the most superficial cell layers of epidermis. Calcitonin gene-related peptide-immunoreactive (-ir) nerves were distributed to dermis and epidermis in lower density than PGP 9.5-ir fibers. Substance P-ir fibers were less numerous; most terminated as free endings in deeper layers of epidermis. Vasoactive intestinal peptide-ir nerves almost exclusively innervated sweat glands, ducts and blood vessels, but not epidermis. The mouse hind paw has potential to serve as a model system for investigations of functional and morphological changes that affect peripheral and autonomic nerves under diverse experimental conditions.

Reflex parasympathetic vasodilatation in facial skin

1. The present report summarizes data from recent studies dealing with parasympathetic innervation of blood vessels in the lower lips (gingiva) of cats. 2. A study using the HRP tracing technique shows that blood vessels in the lower lip are innervated by postganglionic fibres originating in the otic ganglion, but not in the pterygopalatine ganglion. 3. There is a dual innervation of the cat lower lip by two groups of parasympathetic vasodilator fibres; in one case, fibres originating from the facial nerve root are distributed to the lower lip via chorda tympani nerve and in the other, fibres emanating from the glossopharyngeal nerve root project to the lower lip via the otic ganglion. 4. Parasympathetic reflex vasodilatation can be elicited by activation of the trigeminal (somatic), vagus (visceral), chorda tympani (gustatory) and nasal (chemical and mechanical) stimulation in the lower lips of cat. 5. Parasympathetic reflex vasodilatation elicited by somatic stimulation is mediated via the otic ganglion but not via the pterygopalatine ganglion, indicating that parasympathetic neurons, particularly those running as efferents in the glossopharyngeal nerve, are involved in the vasodilatation elicited by somatic, visceral and nasal stimulation.