First evidence of neurons in the male copulatory organ of a spider (Arachnida, Araneae)

Spider males have evolved a remarkable way of transferring sperm by using a modified part of their pedipalps, the so-called palpal organ. The palpal organ is ontogenetically derived from tarsal claws; however, no nerves, sensory organs or muscles have been detected in the palpal bulb so far, suggesting that the spider male copulatory organ is numb and sensorily blind. Here, we document the presence of neurons and a nerve inside the male palpal organ of a spider for the first time. Several neurons that are located in the embolus are attached to the surrounding cuticle where stresses and strains lead to a deformation (stretching) of the palpal cuticle on a local scale, suggesting a putative proprioreceptive function. Consequently, the male copulatory organ of this species is not just a numb structure but likely able to directly perceive sensory input during sperm transfer. In addition, we identified two glands in the palpal organ, one of which is located in the embolus (embolus gland). The embolus gland appears to be directly innervated, which could allow for rapid modulation of secretory activity. Thus, we hypothesize that the transferred seminal fluid can be modulated to influence female processes.

Alleged silk spigots on tarantula feet: electron microscopy reveals sensory innervation, no silk

Several studies on tarantulas have claimed that their tarsi could secrete fine silk threads which would provide additional safety lines for maintaining a secure foot-hold on smooth vertical surfaces. This interpretation was seriously questioned by behavioral experiments, and more recently morphological evidence indicated that the alleged spigots ("ribbed hairs") were not secretory but most likely sensory hairs (chemoreceptors). However, since fine structural studies were lacking, the sensory nature was not proven convincingly. By using transmission electron microscopy we here present clear evidence that these "ribbed hairs" contain many dendrites inside the hair lumen - as is the case in the well-known contact chemoreceptors of spiders and insects. For comparison, we also studied the fine structure of regular silk spigots on the spinnerets and found them distinctly different from sensory hairs. Finally, histological studies of a tarantula tarsus did not reveal any silk glands, which, by contrast, are easily found within the spinnerets. In conclusion, the alleged presence of silk spigots on tarantula feet is refuted.

Morphology and histology of Lyonet's gland of the tropical tasar silkworm, Antheraea mylitta

The morphology and histology of Lyonet's gland in the second to fifth instar larvae of Antheraea mylitta Drury (Lepidoptera: Saturniidae) are described. Each of the paired silk glands of this silk worm were associated with a Lyonet's gland. The paired Lyonet's glands were located on the ventrolateral sides of the esophagus, close to the subesophageal ganglion. Whole mount and SEM observations revealed that each Lyonet's gland consisted of a rosette of glandular mass, and a short narrow tubular duct opening into the anterior part of the silk gland (ASG), close to the common excretory duct. In each instar, these glands were unequal in size. The glandular mass was innervated by fine nerves from the subesophageal ganglion, suggesting a neural control for the glandular activity. The glandular mass was made up of clustered long cells wrapped by a thin basal lamina, which was continuous over the non-secretory low columnar cells of the Lyonet's gland duct and ASG. The narrow bases of long cells of each glandular mass led into the lumen of the duct of the gland. Histochemical analysis of fully developed Lyonet's gland showed clustered lipid granules in the gland cells.

Regulation of Na+ and Cl- transport and mucous gland secretion in airway epithelium

Ussing's short-circuit technique was applied to canine airway epithelium in vitrol and a net flux of Cl- towards the airway lumen was demonstrated, with a smaller net flux of Na+ in the opposite direction. Furosemide decreased and acetylcholine, terbutaline, and histamine increased net ion transport towards the airway lumen. Associated changes in water content in the airway lumen could affect mucociliary clearance, and therefore inhibition of ion transport may play a role in disease states. To study secretions from submucosal glands in vivo, two techniques were used to identify the duct openings in the exposed canine tracheal epithelium. (a) The exposed mucosal surface was coated with powdered tantalum; accumulated secretions produced elevations under which the duct openings were located. (b) A vital dye (0.1% Neutral red) was placed on the exposed mucosal surface; the dye stained the duct openings. With these techniques, the innervation of the submucosal glands and the autonomic regulation of their secretions were studied. Micropuncture techniques were used to sample the secretions from the glands and ducts.

BDNF promotes target innervation of Xenopus mandibular trigeminal axons in vivo

BACKGROUND

Trigeminal nerves consist of ophthalmic, maxillary, and mandibular branches that project to distinct regions of the facial epidermis. In Xenopus embryos, the mandibular branch of the trigeminal nerve extends toward and innervates the cement gland in the anterior facial epithelium. The cement gland has previously been proposed to provide a short-range chemoattractive signal to promote target innervation by mandibular trigeminal axons. Brain derived neurotrophic factor, BDNF is known to stimulate axon outgrowth and branching. The goal of this study is to determine whether BDNF functions as the proposed target recognition signal in the Xenopus cement gland.

RESULTS

We found that the cement gland is enriched in BDNF mRNA transcripts compared to the other neurotrophins NT3 and NT4 during mandibular trigeminal nerve innervation. BDNF knockdown in Xenopus embryos or specifically in cement glands resulted in the failure of mandibular trigeminal axons to arborise or grow into the cement gland. BDNF expressed ectodermal grafts, when positioned in place of the cement gland, promoted local trigeminal axon arborisation in vivo.

CONCLUSION

BDNF is necessary locally to promote end stage target innervation of trigeminal axons in vivo, suggesting that BDNF functions as a short-range signal that stimulates mandibular trigeminal axon arborisation and growth into the cement gland.

Neurturin signalling via GFRα2 is essential for innervation of glandular but not muscle targets of sacral parasympathetic ganglion neurons

Neurturin, a member of the glial cell-derived neurotrophic factor familys of ligands, is important for development of many cranial parasympathetic ganglion neurons. We have investigated the sacral component of the parasympathetic nervous system in mice with gene deletions for neurturin or its preferred receptor, GFRalpha2. Disruption of neurturin signalling decreased cholinergic VIP innervation to the mucosa of the reproductive organs, but not to the smooth muscle layers of these organs or to the urinary bladder. Thus, neurturin and its receptor are involved in parasympathetic innervation of a select group of pelvic visceral tissues. In contrast, noradrenergic innervation was not affected by the gene ablations. The epithelium of reproductive organs from knockout animals was atrophied, indicating that cholinergic innervation may be important for the maintenance of normal structure. Cholinergic neurons express GFRalpha2 on their terminals and somata, indicating they can respond to neurotrophic support, and their somata are smaller when neurturin signalling is disrupted. Colocalisation studies showed that many peripheral glia express GFRalpha2 although its role in these cells is yet to be determined. Our results indicate that neurturin, acting through GFRalpha2, is essential for parasympathetic innervation of the mucosae of reproductive organs, as well as for maintenance of a broader group of sacral parasympathetic neurons.

Motor control of airway goblet cells and glands

Activation of nerves increases airway mucus secretion. The mucus derives from submucosal glands and epithelial goblet cells. Depending upon species and airway level, innervation comprises parasympathetic (cholinergic), sympathetic (adrenergic) and 'sensory-efferent' pathways. In all species studied, cholinergic mechanisms predominate, particularly in human airways. Muscarinic M3 receptors on the secretory cells mediate the cholinergic response. Tachykinins (substance P and neurokinin A) mediate the sensory-efferent response, acting via tachykinin NK1 receptors. Endogenous mechanisms regulate the magnitude of neurogenic secretion, including enzymes (degrade neurotransmitters), nitric oxide (NO) and vasoactive intestinal peptide (VIP) (regulate stimulated secretion), and muscarinic M2 autoreceptors (inhibit acetylcholine release). Exogenous opioids also inhibit neurogenic secretion prejunctionally. Both VIP and opioids act by opening large conductance, calcium-activated potassium (BK(Ca)) channels. Present understanding of neural control of mucus secretion in animal airways requires translation into human data. This information should lead to rational development of drugs for bronchial diseases in which neurogenic mucus hypersecretion contributes to pathophysiology, including chronic bronchitis and asthma.

The foam production system of the male Japanese quail: characterization of structure and function

The research described here characterizes a unique neuromuscular system involved in reproductive behavior--the foam production system of the male Japanese quail (Coturnix japonica). Male quail produce a large amount of foam that is transferred to the female during copulation, enhancing male fertilization success. The source is the foam gland complex, a large sexually dimorphic, androgen sensitive, external protuberance of the dorsal cloaca, consisting of glandular units interdigitated with striated muscle fibers of the sphincter cloacae muscle (mSC). Electromyographic (EMG) analysis of mSC activity in freely moving males interacting with females revealed different characteristics of the EMG signal during copulation, voiding of excreta, and other mSC movement. The amount of mSC activity and also the amount of foam produced were greatly increased by the presence of a female behind a screen. Denervation of mSC eliminated normal mSC movement and also abolished foam production, confirming that mSC activity is the mechanism for foam production. The spinal cord locations of the motoneurons innervating the major cloacal muscles, including mSC, were determined by injecting cholera-toxin conjugated horseradish peroxidase into each muscle. Labelled somata with multiple primary dendrites were located in Area IX of the lateral motor column of synsacral segments 7, 8, or 9 or 8, 9, and 10. The motoneurons serving mSC were intermingled with those projecting to the other cloacal muscles, but there were differences in the rostralcaudal placement of these neural populations. Thus mSC activity is an integral part of the male's reproductive behavior, mSC activity can be socially stimulated, and mSC activity occurring in anticipation of copulation is likely to be functionally significant. Continued investigation of this highly accessible system has the potential to shed light on the mechanisms by which complex motor acts are produced and hormonally regulated.

[Electron microscopy studies of innervation of nasal mucosa glands in humans]

BACKGROUND

Seromucous glands are one of the main components of human nasal mucosa. The innervation pattern is important to understand the control of the different physiological glandular functions. In addition to light-microscopical findings electronmicroscopic investigations were performed to get more detailed information on the innervation of nasal glands.

PATIENTS AND METHODS

Tissue samples of 16 human inferior turbinates were taken during nasal surgery and preserved in Unicryl or 3.5% phosphate-buffered glutaraldehyde. After fixation ultrathin sections were cut. Electron microscopical structures were photodocumented by using a transmission-electron microscope (EM 902 A Zeiss).

RESULTS

Few axons were found in the periglandular tissue. No myo- or glandular-neural tight junctions could be identified. Unmyelinated nerve fibers showed typical components such as neurofilaments, neurotubules and mitochondria in their cytoplasm. An additional control of the glandular secretion by the vascular tone of the fenestrated capillary vessels will be discussed.

CONCLUSIONS

Based on these ultramorphological findings further immunoelectron microscopical investigations will follow to demonstrate the various neurotransmitters and their distribution in periglandular axons.

A calcium/calmodulin-dependent nitric oxide synthase, NMDAR2/3 receptor subunits, and glutamate in the CNS of the cuttlefish Sepia officinalis: localization in specific neural pathways controlling the inking system

Chemical, biochemical, and immunohistochemical evidence is reported demonstrating the presence in the brain of the cuttlefish Sepia officinalis of a Ca2+-dependent nitric oxide synthase, NMDAR2/3 receptor subunits, and glutamate, occurring in neurons and fibers functionally related to the inking system. Nitric oxide synthase activity was concentrated for the most part in the cytosolic fraction and was masked by other citrulline-forming enzyme(s). The labile nitric oxide synthase could be partially purified by ammonium sulfate precipitation of tissue extracts, followed by affinity chromatography on 2',5'-ADP-agarose and calmodulin-agarose. The resulting activity, immunolabeled at 150 kDa on sodium dodecyl sulfate-polyacrylamide gel electrophoresis by antibodies to rat neuronal nitric oxide synthase, depended on NADPH and tetrahydro-L-biopterin, and was inhibited by N(G)-nitro-L-arginine. NMDAR2/3 subunit-immunoreactive proteins migrating at 170 kDa could also be detected in brain extracts, along with glutamate (whole brain: 0.32 +/- 0.03 micromol of glutamate/mg of protein; optic lobes: 0.22 +/- 0.04; vertical complex: 0.65 +/- 0.06; basal lobes: 0.58 +/- 0.04; brachial lobe: 0.77 +/- 0.06; pedal lobe: 1.04 +/- 0.08; palliovisceral lobe: 0.86 +/- 0.05). Incubation of intact brains with 1.5 mM glutamate or NMDA or the nitric oxide donor 2-(N,N-diethylamino)diazenolate-2-oxide caused a fivefold rise in the levels of cyclic GMP, indicating operation of the glutamate-nitric oxide-cyclic GMP signaling pathway. Immunohistochemical mapping of Sepia CNS showed specific localization of nitric oxide synthase-like and NMDAR2/3-like immunoreactivities in the lateroventral palliovisceral lobe, the visceral lobe, and the pallial and visceral nerves, as well as in the sphincters and wall of the ink sac.

Immunohistochemical localization of delta opioid receptors in peripheral tissues

The distribution of delta opioid receptor (DOR) immunoreactivity (ir) was examined in various peripheral tissues of Sprague-Dawley rats and macaque monkeys, including glabrous and hairy skin, corneas, eyelids, and the lip. DOR-ir was observed in all tissues examined. In addition to the presence of DOR-immunoreactive fibers in subcutaneous nerve bundles and the papillary dermis, we report the existence of positively labeled fibers and terminals in close association with peripheral structures not traditionally assigned a primarily nociceptive function, such as hair follicles, glandular apparatus, and blood vessels. In every case, staining was restricted to small-diameter axons that appeared to terminate as free nerve endings. To further classify DOR-immunoreactive fibers, we examined the extent of colocalization between DOR and three commonly used neuronal subtype markers; tyrosine hydroxylase (TH), calcitonin gene-related peptide (CGRP), and RT-97, a monoclonal antibody which preferentially labels neurons with myelinated axons. Additional double-labeling experiments using the nonspecific neuronal marker Protein Gene Product 9.5 were performed in glabrous skin to determine the percentage of total fiber count that displayed DOR-ir. No colocalization was observed between DOR and RT-97, indicating that DOR-ir is localized to unmyelinated axons. In addition, DOR colocalized with CGRP, but did not colocalize with TH. Taken together, these data support the hypothesis that delta opioid receptors in peripheral tissues are associated with sensory fibers, but not with the terminals of postganglionic sympathetic neurons.

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.

Increased VIP-positive nerve fibers in the mucous glands of subjects with chronic bronchitis

The presence and distribution of neuropeptide-containing nerves within bronchial surgical specimens has been investigated in bronchitic (n = 12) and in nonbronchitic subjects (n = 7). Lung tissue, obtained from patients undergoing thoracotomy for limited lung lesions, was processed immediately and analyzed for nerves using the streptavidin-biotin complex peroxidase method with antisera to the neural marker protein gene product 9.5 (PGP 9.5) and the neuropeptides vasoactive intestinal peptide (VIP), substance P (SP), calcitonin-gene related peptide (CGRP). There were no significant differences between the two groups with respect to the density of PGP 9.5-, SP-, or CGRP-positive nerves in both the locations assessed (smooth muscle layer and glands). The density of VIP-positive nerves was significantly higher in the glands of bronchitic than in nonbronchitic subjects. A negative relationship was found between the presence of airway inflammation, as indexed by mononuclear cell tissue infiltration, and the density of PGP 9.5-positive nerves in both smooth muscle and glands. Likewise, a relationship was found between the smoking history (packs/yr and age of onset of smoking) and the density of VIP-positive nerves in glands. These findings support a role for VIP in the hallmark of chronic bronchitis, i.e., sputum production.

Control of venom production and secretion by sympathetic outflow in the snake Bothrops jararaca

Many studies have examined the morphological and biochemical changes in the secretory epithelium of snake venom glands after a bite or milking. However, the mechanisms of venom production and secretion are not yet well understood. The present study was undertaken to evaluate the role of the sympathetic nervous system in the control of venom production and secretion. Venom glands were obtained from Bothrops jararaca (Viperidae) snakes, either unmilked previously or milked 4, 7 or 15 days before they were killed. Levels of tyrosine-hydroxylase-like immunoreactivity were higher in venom glands collected 4 days after milking, coinciding with the maximal synthetic activity of the secretory cells. The only catecholamine detected by high-performance liquid chromatography was noradrenaline, indicating the presence of noradrenergic fibres in these glands. In reserpine-treated milked snakes, no venom could be collected, and electron microscopic analysis showed narrow rough endoplasmic reticulum cisternae, instead of wide cisternae, and less well-developed Golgi apparatus compared with milked untreated snakes, indicating impairment of protein synthesis and secretion. The administration of isoprenaline or phenylephrine (beta- and alpha-adrenoceptor agonists, respectively) to reserpine-treated milked snakes promoted the widening of the rough endoplasmic reticulum and restored venom production, but only phenylephrine restored the development of the Golgi apparatus and the formation of many secretory vesicles. These results provide the first evidence that the sympathetic nervous system plays an important role in venom production and secretion in the venom glands of Bothrops jararaca. Understanding the importance of noradrenergic stimulation in venom production may provide new insights for research into the treatment of snakebites.

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.

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.

Neuroendocrine cell-axonal complexes in the minor vestibular gland

OBJECTIVE

To study neuroendocrine cells and nerves in vestibular glands of patients with vestibulitis.

STUDY DESIGN

Substance P chromogranin, serotonin and neuron-specific enolase immunoreactivity was studied in vestibular gland tissue. Electron microscopic analysis was performed on vestibular duct tissue.

RESULTS

Neuroendocrine cells containing immunoreactive serotonin and chromogranin were demonstrated in a vestibular gland duct of a patient with vestibulitis. Substance P immunoreactive axons were found in submucosal nerves, and rare, positively staining axons were seen in the duct epithelium. In another patient neuroendocrine cells with closely applied intraepithelial axons were demonstrated by electron microscopy in the duct of a vestibular gland.

CONCLUSION

Intraepithelial axons are present in ducts of vestibular glands, where they are closely applied to serotonin-containing neuroendocrine cells. This close association and the presence of substance P immunoreactivity in local nerves may play a role in the symptomatology of vestibulitis.

Regulation of mucous acinar exocrine secretion with age

Denny and co-workers (Navazesh et al., 1992) recently reported decreased concentrations of MG1 and MG2 mucins in resting and stimulated whole human saliva with age. The current study was therefore conducted to examine whether there is a corresponding attenuation with age in stimulus secretion coupling regulating mucous cell exocrine secretion. We utilized an in vitro model system, isolated rat sublingual acini, to evaluate the regulation of mucous cell exocrine secretion. Rat sublingual glands are similar to human sublingual and minor mucous glands, both histologically and in terms of their pattern of innervation, which is predominantly parasympathetic. Mucin secretion is thus activated primarily by muscarinic cholinergic agonist and to a lesser extent by vasoactive intestinal peptide (VIP), which is co-localized with acetylcholine in parasympathetic nerve terminals. We isolated sublingual mucous acini from five-month-old and 24-month-old rats and compared the concentration responses for mucin secretion induced by VIP and the muscarinic agonist, arecaidine propargyl ester (APE). Concentration-response curves for VIP were nearly identical for mucous acini from the five-month-old and 24-month-old animals. Values for basal secretion, maximal secretion, and EC50 (approximately equal to 200 nmol/L VIP) were statistically equivalent between both age groups. Concentration-response curves for APE were also very similar between age groups, with no statistically significant difference in basal secretion or EC50 values (approximately equal to 50 nmol/L APE). Maximal secretion was slightly less but statistically different for 24-month-old vs. five-month-old animals, 158% vs. 169% above basal secretion, respectively. Collectively, we found no substantial age-related changes in the secretory responsiveness of salivary mucous cells.

Cellular mechanisms in activation of Na-K-Cl cotransport in nasal gland acinar cells of guinea pigs

The cellular regulation mechanism of Na-K-Cl cotransport was studied in dispersed acinar cells of the guinea pig nasal gland by a microfluorimetric imaging method using the Na(+)-sensitive dye sodium-binding benzofuran isophthalate. Addition of 1 micron acetylcholine (ACh) induced an immediate increase in intracellular Na+ concentration ([Na+]i) by 36.7 +/- 9.9 mM, which was almost completely abolished by the addition of atropine. The increased [Na+]i after cholinergic stimulation was due to the external (Cl-)-dependent cotransport system (about 80% of the total Na+ influx) and the dimethyl amiloride-sensitive (Na+)-H+ exchange system (of about 20%). The ACh-induced increase in [Na+]i was dependent on extracellular Ca2+ and was prevented by pretreatment with 8-(N, N-diethylamino)octyl-3,4,5-trimethoxybenzoate or O-O'-bis(2-aminophenyl)ethyleneglycol-N, N, N', N'-tetraacetic acid tetraacetoxymethylester. Addition of 1 microns ionomycin mimicked the ACh-induced increase in [Na+]i which was dependent on external Cl-. Moreover, both a calmodulin antagonist trifluoperazine and a myosin light chain kinase inhibitor ML-7 reduced the ACh-induced response in [Na+]i. However, the following treatment did not affect the basal [Na+]i nor the ACh-induced increase in [Na+]i: (i) addition of dibutyryl cAMP, 8-Br-cGMP, or phorbol 12-myristate 13-acetate, (ii) pretreatment of protein kinase inhibitors, H-89, H-8, H-7 or chelerythrine, (iii) prevention of cytosolic Cl- efflux by the addition of diphenylamine-2-carboxylic acid or, (iv) prevention of cytosolic K+ efflux by the addition of charybdotoxin.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of hypoxia on reflex responses of tracheal submucosal glands

The effects of moderate sustained normocapnic hypoxia on tracheal submucosal gland reflex responses were studied. Experiments were performed in anesthetized, paralyzed, and mechanically ventilated dogs. The changes in the number of secreting glands and volume of secreted fluid in the subsequent period of time were recorded after 15-30 min of controlled ventilation with room air [arterial PO2 (PaO2) 86 +/- 3 Torr], hypoxic gas mixture (PaO2 49 +/- 4 Torr), or 100% O2 (PaO2 339 +/- 39 Torr), under isocapnic and isohydric conditions. The hillocks method was used to quantify the changes in submucosal gland secretion. The changes in secretion 30 s after stimulation of pulmonary C-fiber receptors by right atrial injection of capsaicin (10 micrograms/kg; n = 10) were markedly lower during moderate hypoxia than in normoxia or hyperoxia. Differences in the number of liquid droplets and the volume of secreted fluid were statistically significant (P < 0.05 and P < 0.001, respectively). Stimulation of airway rapidly adapting receptors by lung deflation increased airway secretion; the number of "hillocks" and the volume of secreted fluid were lower in hypoxic than in hyperoxic state. Differences between response curves for the number of glands activated and secreted volume were statistically significant (P < 0.05 and P < 0.001). The number of glands activated by substance P given locally by arterial infusion was not affected by the state of oxygenation, but the calculated volume of secreted fluid was lower during the hypoxic state than under hyperoxic condition (P = 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Pathways and mechanisms involved in neural control of laryngeal submucosal gland secretion

The purpose of this study was to define the pathways and mechanisms involved in the neural regulation of laryngeal mucosal gland functions. In anesthetized, paralyzed, and artificially ventilated dogs, the responses of laryngeal submucosal glands to stimulation of laryngeal mechanoreceptors and peripheral chemoreceptors were examined by measuring the number of hillocks and volume of secreted fluid before and after activation of sensory nerve endings. Compared with a control period, the number of hillocks and volume of secreted fluid significantly increased (P < 0.05) with mechanical stimulation of the vocal folds (n = 13) and with chemical activation of peripheral chemoreceptors by systemic administration of sodium cyanide (100 micrograms/kg; n = 11). The reflex responses induced by vocal fold stimulation and activation of peripheral chemoreceptors were slightly decreased by interrupting transmission in the recurrent laryngeal nerves (P > 0.05) and were abolished by subsequent sectioning of superior laryngeal nerves or prior intravenous administration of atropine methylnitrate (P < 0.05). In denervated animals, topical application of nicotine on laryngeal epithelium caused significant activation of submucosal glands (P < 0.05). We conclude that laryngeal secretion can be significantly altered reflexly by stimulation of laryngeal sensory nerve endings and peripheral chemoreceptors, that both superior and recurrent laryngeal nerves convey cholinergic outflow to laryngeal submucosal glands, and that nicotine acting locally activates laryngeal submucosal glands.

Peripheral projections of nervus terminalis LHRH-containing neurons in the tiger salamander, Ambystoma tigrinum

The peripheral projections of the nervus terminalis (NT) have been difficult to examine due to the weak immunoreactivity of the processes to various antibodies. We performed two experimental manipulations in the tiger salamander in an attempt to increase the luteinizing hormone-releasing hormone-immunoreactive (LHRH-ir) labelling in the peripheral processes of the NT:1) the NT was sectioned centrally, or 2) a 100 mg melatonin pellet was embedded subcutaneously for 3 days prior to sacrifice. Following these manipulations, animals were sacrificed and tissue was processed with standard immunocytochemical techniques for the analysis of the distribution of LHRH-ir processes. In the nasal cavity, LHRH-ir fibers were observed projecting 1) into the rostral olfactory epithelium, 2) to Bowman's glands in the lamina propria of the rostromedial olfactory mucosa and ventrolateral mucosa between the main nasal cavity and Jacobson's organ, 3) into the naris constrictor muscle, and 4) along the palatine nerves and ganglia. These lesion and hormone manipulations have enabled the detection of peripheral projections of the NT not observed previously with immunocytochemical procedures alone. The wide distribution of LHRH-ir NT processes in the nasal cavity and cranium suggests that this nerve may influence many different cranial structures during appropriate pheromonal or neuroendocrine events.

Secretomotor rhinopathy after Le Fort I maxillary osteotomy. Case report

Severe secretomotor (vasomotor) rhinopathy is a very uncommon nasal condition which is believed to result from marked autonomic neural imbalance to the nasal and lacrimal glands. It has not, to our knowledge, been reported after trauma or elective surgery. A patient is described who developed this condition after a Le Fort maxillary osteotomy. The clinical difficulties of establishing this diagnosis are highlighted, and contemporary management options are discussed.

Immunohistochemical and electron microscopic studies of substance P in guinea pig nasal glands

The distribution of substance P-like immunoreactive (SP-IR) nerve endings in the nasal gland of the guinea pig was studied by using histochemical techniques to detect mucous glycoprotein and immunohistochemical techniques for SP, in combination with electron microscopy. Most nasal glands were negative for both AB and periodic acid-Schiff (PAS) staining. The SP-IR nerve fibers were found to form a network around these glands. The SP-IR nerve endings were located in the region between interdigitated cytoplasmic folds of acinar cells and along the cell surface, as well as in the intercellular spaces of proximal ducts. The acini which closely contacted with SP-IR nerve endings were serous in type. Our results suggest that substance P may contribute to the regulation of serous gland secretion in the guinea pig nasal mucosa.

The stopping response of Xenopus laevis embryos: pharmacology and intracellular physiology of rhythmic spinal neurones and hindbrain neurones

1. Xenopus laevis embryos stop swimming in response to pressure on the cement gland. This behaviour and ‘fictive’ stopping are blocked by bicuculline (10 mumol 1(−1)), tubocurarine (110 mumol 1(−1)) and kynurenic acid (0.5 mmol 1(−1)). 2. Intracellular recordings from spinal neurones active during swimming have shown that pressure on the cement gland evokes compound, chloride-dependent inhibitory postsynaptic potentials (IPSPs). These are blocked by bicuculline, tubocurarine and kynurenic acid, but are unaffected by strychnine (2 mumol 1(−1)). 3. When the cement gland is pressed, trigeminal ganglion activity precedes both the IPSPs and the termination of ‘fictive’ swimming activity recorded in rhythmic spinal neurones. The trigeminal discharge is unaffected by the antagonists bicuculline, tubocurarine, kynurenic acid and strychnine. 4. Intracellular recordings from the hindbrain have revealed neurones that are normally silent, but rhythmically inhibited during ‘fictive’ swimming. In these neurones pressure on the cement gland evokes depolarising potentials, often with one or more spikes. 5. We propose that the stopping response depends on the excitation of pressure-sensitive trigeminal receptors which innervate the cement gland. These release an excitatory amino acid to excite brainstem GABAergic reticulospinal neurones, which inhibit spinal neurones to turn off the central pattern generator for swimming. There may also be a less direct pathway.

Reflex responses of laryngeal and pharyngeal submucosal glands in dogs

In dogs tracheal secretion is enhanced reflexly and by locally acting mediators such as substance P (SP). To evaluate the role of these mechanisms on submucosal gland secretion in the larynx (L) and pharynx (Ph), we compared the effects of mechanical stimulation of intrapulmonary irritant receptors and stimulation of pulmonary C-fiber receptors by capsaicin (20 micrograms/kg iv) with the response produced by intravenous SP. In six alpha-chloralose-anesthetized, paralyzed, and artificially ventilated dogs, submucosal gland secretion was monitored by analyzing the areas covered by hillocks of liquid and calculating the volume of secreted liquid (microliter) in the L and Ph. Mechanical stimulation of the carina increased both the number of hillocks and the volume of secreted liquid in the L. Excitation of pulmonary C-fiber receptors also increased the number of hillocks, and total volume of secreted liquid was elevated from 1.9 +/- 0.5 to 8.3 +/- 1.4 microliters (P less than 0.01). These responses were significantly reduced by prior cervical vagotomy and intravenous administration of atropine. Neither stimulation of irritant receptors nor stimulation of pulmonary C-fiber receptors caused discernible effects on Ph submucosal gland secretion. However, intravenous SP increased the number of Ph hillocks and elevated the volume of secreted Ph liquid from 1.0 +/- 0.6 to 10.2 +/- 1 microliters (P less than 0.01); similar responses to intravenous SP were observed in the L. Prior intravenous administration of atropine methylnitrate or bilateral vagotomy did not alter Ph or L secretory responses to intravenous SP.(ABSTRACT TRUNCATED AT 250 WORDS)

An electron microscopic study of acetylcholinesterase-activity and vasoactive intestinal peptide- and neuro-peptide Y-immunoreactivity of the intraepithelial nerve fibers in the nasal gland of the guinea pig

In combination with transmission electron microscopy (TEM), histochemistry for acetylcholinesterase (AChE) and immunohistochemistry for vasoactive intestinal peptide (VIP) and neuropeptide Y (NPY) were carried out on the intraepithelial nerve fibers of the guinea-pig nasal gland. AChE-positive nerve profiles and VIP-immunoreactive nerve profiles were detected in abundance within the epithelium of the glandular acini and within the epithelium of intralobular excretory ducts including the intercalated and striated ducts. Intraepithelial NPY-immunoreactive nerve profiles were also considerably large in number in the nasal gland, but less frequent than the other two types of nerve profiles; furthermore, the NPY-immunoreactive nerve profiles appeared absent within the epithelium of the striated duct. All the intraepithelial nerve varicosities were in close spatial contact with the epithelial cells of the acinus and the duct and also with the myoepithelial cells, which were commonly seen in the acinus and the intercalated duct. Throughout the present study, however, no membranous specializations could be found between the nerve varicosities and the epithelial cells or the myoepithelial cells. The present results suggest an intense and delicate regulation through the collaboration among ACh, VIP and NPY of the secretory activity of the guinea-pig nasal gland, including the emission of acinar secretions into the duct through contraction of the myoepithelium and modification of the secretion contents by the duct epithelium.

Distribution of vasoactive intestinal peptide- and substance P-containing nerves originating from neurons of airway ganglia in cat bronchi

This study examined the possibility that vasoactive intestinal peptide (VIP)- and substance P (SP)-containing nerve fibers in bronchial smooth muscle, glands, epithelium, and blood vessels originate from neurons of airway ganglia. Explants of airway walls were maintained in culture with the expectation that nerve fibers from neurons of airway ganglia would remain viable, whereas fibers originating from neurons not present in the airway walls would degenerate. Airways were dissected and placed into culture dishes containing CMRL 1066 medium for 3, 5, and 7 days. In controls (noncultured), VIP- and SP-like immunoreactivity was observed in nerve fibers associated with bronchial smooth muscle, glands, and blood vessel walls and in nerve cell bodies of airway ganglia. Nerve fibers containing SP were also observed within the bronchial epithelium. After 3, 5, and 7 days in culture, VIP- and SP-containing fibers were identified in all of the same locations except in the airway epithelium where SP-containing fibers could not be demonstrated. VIP and SP were frequently colocalized in the same nerve fibers of bronchial smooth muscle and glands in controls and cultured airways. There were no statistically significant differences in nerve fiber density for either VIP- or SP-containing fibers in bronchial smooth muscle between controlled and cultured airways. VIP concentrations in cultured airways were significantly less than in controls. The results suggest that a large proportion of VIP- and SP-containing nerve fibers supplying bronchial smooth muscle, glands, and blood vessels in the airways originate from neurons of airway ganglia.

Cholinergic manipulation of digestive function in ruminants and other domestic livestock: a review

Exocrine secretions in the digestive tract of domestic livestock are controlled by a combination of neural and endocrine inputs. The parasympathetic domain of the autonomic nervous system is responsible for efferent signals that regulate most exocrine secretory processes. Exocrine tissues possess cholinergic muscarinic receptor subtypes that are different from those found in brain, heart and muscle tissues. Cholinergic stimulation of specific muscarinic receptor subtypes has enhanced secretions of the salivary glands and pancreas. These changes in output of exocrine glands can alter digestive function that may benefit production of cattle and swine.

[Stimulation of mucous glands of the respiratory tract by neuropeptides: comparison of exogenous administration and endogenous liberation]

Exogenous substance P is a powerful stimulant of tracheal gland secretion but the contribution of endogenous neuropeptides to neurogenic gland secretion is unknown. Using the Ussing chamber technique, we measured the secretion of radiolabeled macromolecules from submucosal glands in the ferret. Neurokinins caused gland secretion through a neurokinin-1 (NK-1) receptor. Gland secretion caused by electric field stimulation of postganglionic nerve endings was not inhibited by a substance P antagonist and was not augmented by agents known to prevent neurokinin degradation in the tissue. We conclude that the release of endogenous neurokinins plays no rôle in neurally evoked gland secretion. This is despite the fact that endogenous neurokinins have been shown to be involved in vagally induced airway smooth muscle contraction and increased capillary permeability in the same species.

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 patterns of co-existence of neuropeptides in cranial autonomic neurons of guinea-pigs have been examined with quantitative double-labelling immunofluorescence and retrograde axonal tracing using Fast Blue. Within the sphenopalatine, otic, sublingual and submandibular ganglia, and a prominent intracranial ganglion associated with the glossopharyngeal nerve, most neurons contained immunoreactivity of vasoactive intestinal peptide, neuropeptide Y, enkephalin and substance P in combinations that were correlated with their projections. Hair follicles in the facial skin formed a major target of sphenopalatine ganglion cells. The combinations of peptides co-existing in these neurons depended upon the region of the skin where the follicles were located. The parotid gland was innervated by neurons with cell bodies in the otic ganglion or the intracranial ganglion. Most of these neurons contained immunoreactivity to all four peptides. The sublingual gland was innervated by local ganglion cells usually containing immunoreactivity to neuropeptide Y, vasoactive intestinal peptide and substance P. The submandibular gland was innervated by local ganglion cells containing enkephalin immunoreactivity and low levels of immunoreactivity to neuropeptide Y. Presumptive vasodilator neurons, containing immunoreactivity to vasoactive intestinal peptide but no other peptide examined here, comprised less than 10% of cranial autonomic ganglion cells. These results demonstrate that the patterns of co-existence of neuropeptides in cranial autonomic neurons show a high degree of target specificity. The discovery that hair follicles form a major parasympathetic target implies a broader range of actions of cranial autonomic neurons than has been suspected until now.

The functional significance of the sympathetic innervation of mucous glands in the bronchi of man

1. Pieces of human bronchi, from lung resected for carcinoma of the bronchus, were mounted in Ussing chambers and given [35S]sulphate as radiolabelled precursor of mucous glycoproteins (mucins). The release of 35S, bound to macromolecules, into the luminal half-chamber was used as an index of mucin secretion. 2. Noradrenaline, at concentrations of 1, 10 and 100 microM, was given into both halves of the Ussing chamber. At the lowest concentration, noradrenaline failed to change mucin output, but at the two higher concentrations it stimulated output. 3. In other experiments the sympathetic nerves in the bronchial wall were labelled with 5-hydroxydopamine and examined under the electron microscope. The distances between adrenergic nerve varicosities and submucosal glands were measured; some sympathetic nerve varicosities were seen within 1 microns of gland cells. 4. A simple mathematical model for the diffusion of noradrenaline was used to predict the concentrations of the transmitter likely to result at different distances from a nerve if one or more vesicles of noradrenaline were released. 5. The model predicts that the release of a single large vesicle of noradrenaline is likely to generate an effective concentration of transmitter provided that the nerve is within 1 micron of the target cell.

Analysis of ionic conductance mechanisms in motor cells mediating inking behavior in Aplysia californica

1. The release of ink in response to a noxious stimulus is a relatively stereotyped behavior produced by strong and long-lasting stimuli. The purpose of this series of papers is to determine the quantitative extent to which the known voltage- and time-dependent ionic conductance mechanisms and synaptic influences can account for the ink gland motor neurons' firing pattern and, thus, the features of the behavior. 2. Four voltage- and time-dependent ionic currents have been analyzed. These include a fast transiet Na+-mediated inward current, a slower Ca2+-mediated inward current, a fast transient K+-mediated outward current, and a slower delayed outward current also mediated by K+ ions. 3. The current-voltage (I-V) relationships, equilibrium potentials, and steady-state activation and inactivation characteristics appear qualitatively similar to comparable currents observed in other gastropod neurons. 4. The recovery from inactivation of the delayed outward current has two time constants, one comparable to the inactivation time constant and the other more than an order of magnitude larger. The fast transient K+ current also appears to have a similar slow recovery from inactivation. 5. The synaptic current contributing to the firing pattern of the ink motor cells is a complex function of time. Initially, the synaptic conductance is high and the equilibrium potential near 0 mV. But, with time there is a gradual decrease in synaptic conductance and shift in the equilibrium potential to more depolarized levels.

Motor controls of opaline secretion in Aplysia californica

1. Using combined morphological and electrophysiological techniques, we have identified motor neurons in the right pleural ganglion of Aplysia californica that contribute to the release of opaline from the opaline gland. 2. Three pleural ganglion neurons were found to meet the requirements for identification as opaline gland motor neurons by a) sending processes in nerve P5, which innervates the gland; b) producing contractions of the gland in the absence of central synaptic activity; and c) producing excitatory junctional potentials (EJPs) in cells making up the opaline gland itself. The neurons can be reliably located and have been designated PLR1, PLR2, and PLR3. 3. When gland contraction is measured by the change in luminal pressure, the gland response is a graded function of low-frequency spike activity in the motor neurons. 4. Presumptive EJPs recorded from opaline gland cells are reversibly decreased in size by high extracellular Mg2+ and reversibly increased in size by raising the concentration of extracellular Ca2+. These results suggest that the presumptive EJPs are chemically mediated. The presumptive EJPs show facilitation and posttetanic potentiation. 5. The identified opaline motor neurons may constitute a significant portion of the motor input to the opaline gland via nerve P5 since hyperpolarization of the cells prevents the opaline gland response elicited by right connective stimulation in vitro. 6. We have compared the properties of the opaline motor neurons with the previously identified properties of the ink motor neurons (6--9, 19). Like the ink motor neurons, the opaline motor neurons have high resting potentials, are electrically coupled, and have no spontaneous spike activity. They also receive a slow and long-lasting evoked depolarizing synaptic input, which appears to be mediated by a decreased conductance mechanism. The firing pattern of the opaline motor neurons produced by synaptic input shows the same delayed bursting pattern previously described for the ink motor neurons. 7. The biophysical properties and synaptic input to the ink motor neurons have been shown to affect the features of inking behavior (4, 6--9, 19). The opaline motor neurons share some of these biophysical characteristics and mediate a defensive behavior similar to ink release. Further comparisons of these behaviors and their underlying neural circuits may provide a better understanding of the extent to which cellular biophysical properties and patterns of synaptic input influence the features of the behaviors that individual neurons mediate.

Aplysia ink release: central locus for selective sensitivity to long-duration stimuli

1. A behavioral and electrophysiological analysis of defensive ink release in Aplysia californica was performed to examine the response of this behavior and its underlying neural circuit to various-duration noxious stimuli. 2. Three separate behavioral protocols were employed using electrical shocks to the head as noxious stimuli to elicit ink release. Ink release was found to be selectively responsive to longer duration stimuli, and to increase in a steeply graded fashion as duration is increased. 3. Intracellular stimulation of ink motor neurons revealed that ink release is a linear function of motor neuron spike train duration, indicating that the selective sensitivity of the behavior to long-duration stimuli is not due to a nonlinearity in the glandular secretory process. 4. In contrast, electrophysiological examination of ink motor neuron activity in response to sustained head shock revealed an accelerating spike train. During the later part of the spike train, compound excitatory synaptic potentials show a positive shift in reversal potential. 5. Our results suggest a central locus for the mechanisms that determine sensitivity of inking behavior to stimulus duration. 6. In contrast to ink release, defensive gill withdrawal was found to be extremely sensitive to short-duration stimuli.

Biophysical mechanisms contributing to inking behavior in Aplysia

1. The release of ink from the ink gland of Aplysia californica in response to noxious stimuli is mediated by three electrically coupled motor neurons, L14A, L14B, L14C, whose cell bodies are located in the abdominal ganglion. The initial synaptic input to the ink motor neurons is relatively ineffective in firing the cells. As a result, a pause of 1--3 s often occurs before the cells attain their maximum firing frequency and cause the release of ink. Using current and voltage-clamp techniques we have analyzed the mechanisms underlying the firing pattern of these cells. 2. The presence of a fast transient K+ current appears to play an important role in mediating the firing pattern of the ink motor neurons. Their high resting potential (-75 mV) ensures that the steady-state level of inactivation of the conductance channels for the fast K+ current will normally be low. Thus a train of EPSPs or a depolarizing current pulse can activate this current maximally, thereby reducing the initial effectiveness of the excitatory input. 3. In addition to the fast transient K+ current, four other currents were identified: 1) a fast transient tetrodotoxin-sensitive inward current, presumed to be carried by Na+; 2) a slower tetrodotoxin-insensitive inward current, presumed to be carried by Ca2+; 3) a slow transient outward tetraethylammonium- (TEA) sensitive current; and 4) a very slow TEA-insensitive outward current. 4. A decreased conductance EPSP, which turns on over a several-second period, contributes to a late acceleration of spike discharge in the L14 cells. 5. The results suggest that a unique combination of biophysical properties of the L14 cells and the features of the synaptic input cause them to act as a low-pass filter in the reflex pathway for inking. Their high resting potential, which ensures minimal inactivation of the fast transient K+ current channel, makes these cells preferentially responsive to strong and long-lasting stimuli. The delayed recruitment of a decreased conductance EPSP augments the tendency of the L14 cells to fire in an accelerating burst pattern.

In vitro studies of frog mucous glands

The ionic outflow, mainly consisting of Na+ and Cl-, from the mucous glands in an excised nerve-skin preparation of frog has been determined by recording the conductance changes occurring in a fluid layer covering a small area of the skin surface. In the main series of experiments the glands were activated by stimulation of sympathetic nerve fibers in the skin nerve. The relationship between the ionic outflow and the number of nerve volleys was studied over a wide range. The outflow per impulse was found to be fairly constant during the first tens of impulses but diminished gradually with increasing number of stimuli up to a certain maximum value--varying in different preparations--after which the outflow ceased completely. During the initial phase of stimulation the outflow is most likely caused by an ejection of performed secretion due to the contractions of the glandular myoepithelium. The continued outflow in the later stages of the stimulation periods must be due to production of new secretion. Since the glandular epithelium is devoid of nerve terminals a nervous control of the ionic secretion can only be explained by an indirect influence mediated either by transmitter diffusion from the myoepithelial nerve endings or by a close electric coupling between the contractile and the secretory gland cells. Adrenaline and noradrenaline induce ionic outflows which like those evoked by nerve stimulation are inhibited by the beta-adrenoreceptor blocker propranolol, alpha-adrenoreceptor blockers being without effect. A serendipitous finding of tonus changes in the frog skin during nerve stimulation is also described.

In vivo studies of individual mucous glands in the frog

Individual mucous glands in the toe web were studied in curarized decerebrate frogs using vital microscopy in combination with still or motion photomicrography. By changing the focus position to different levels various structures in the gland could be identified and their changes during glandular activation studied. The first visible effect of nerve stimulation was a contraction of the myoepithelium and probably also structural changes of the secretory epithelium resulting in a narrowing of the glandular lumen. Following this, tricuspid valve opened and secretion was ejected. The latency and time course of the contractile response to nerve stimulation were determined and the influence of the number of stimuli on the duration of the contraction and relaxation phases was analyzed. Comparisons were made with reflex activation of the gland as well as with neurohormonal stimulation. The myoepithelial contraction was found to be under adrenergic control. Of the smooth-muscle stimulants tested only Substance P induced contractions. The time course of the ionic outflow from the toe web was determined by conductance measurements in the fluid surrounding the web and compared with the visually observed phenomena. The initial outflow was concomitant with the phasic myoepithelial contraction but a continued secretion could also be observed and recorded from glands kept in a steady state of contraction by iterative nerve stimulation. The functions of the toe web glands were found to be critically dependent on a maintained circulation in the surrounding capillary network.

Monoaminergic fluorescence in frog skin

The Falck-Hillarp fluorescence technique was employed in an attempt to determine the distribution of sympathetic innervation in frog skin. No evidence was found of a direct monoaminergic nerve supply to the cells of the non-glandular epithelium in the epidermis. Instead, specific fluorescence was mainly confined to the vicinity of the skin glands. Fluorescent fibers were observed surrounding the mucous type of gland. The secretory content of this gland was not fluorescent. In the granular type of gland the main source of fluorescence was the secretory granules filling the lumen. These developed a fluorescence in the spectral range of 5-hydroxytryptamine. The brightness of the fluorescence indicated a very high content of this amine. Fluorimetric analysis showed that no catecholamines were present in the secretion. In glands devoid of secretory granules there were some indications of a monoaminergic innervation of the secretory epithelium, but this was hard to determine because of the abundant nonspecific fluorescence. Sparse dots of specific fluorescence were found close to the surrounding smooth muscle cells. -- These findings rule out the possibility of a direct sympathetic nervous control of the non-glandular epithelium in frog skin but indicate that this is instead confined to the skin glands.

Innervation of skin glands in the frog

A comparative study was undertaken on the innervation of mucous and granular glands in frog skin. Results obtained by the Falck-Hillarp fluorescence technique and cholinesterase staining indicated that both types of glands receive exclusively adrenergic innervation. Electron microscopy was used to investigate the innervation pattern at the ultrastructural level. The distribution of nerve terminals was found to differ in the two types of glands. In the mucous gland, terminals were found at a distance of about 0.5 mum from the basement membrane but never within the gland parenchyma. In the granular gland, the terminals were located between smooth muscle cells and also in direct contact with the secretory epithelium but never outside the basement membrane.