Characterization of superior cervical ganglion neurons that project to the submandibular glands, the eyes, and the pineal gland in rats

Immune-mediated denervation of the pineal gland underlies sleep disturbance in cardiac disease

Disruption of the physiologic sleep-wake cycle and low melatonin levels frequently accompany cardiac disease, yet the underlying mechanism has remained enigmatic. Immunostaining of sympathetic axons in optically cleared pineal glands from humans and mice with cardiac disease revealed their substantial denervation compared with controls. Spatial, single-cell, nuclear, and bulk RNA sequencing traced this defect back to the superior cervical ganglia (SCG), which responded to cardiac disease with accumulation of inflammatory macrophages, fibrosis, and the selective loss of pineal gland-innervating neurons. Depletion of macrophages in the SCG prevented disease-associated denervation of the pineal gland and restored physiological melatonin secretion. Our data identify the mechanism by which diurnal rhythmicity in cardiac disease is disturbed and suggest a target for therapeutic intervention.

Curcumin prevents neuronal loss and structural changes in the superior cervical (sympathetic) ganglion induced by chronic sleep deprivation, in the rat model

Background

In modern societies, sleep deprivation is a serious health problem. This problem could be induced by a variety of reasons, including lifestyle habits or neurological disorders. Chronic sleep deprivation (CSD) could have complex biological consequences, such as changes in neural autonomic control, increased oxidative stress, and inflammatory responses. The superior cervical ganglion (SCG) is an important sympathetic component of the autonomic nervous system. CSD can lead to a wide range of neurological consequences in SCG, which mainly supply innervations to circadian system and other structures. As the active component of Curcuma longa, curcumin possesses many therapeutic properties; including neuroprotective. This study aimed to evaluate the effect of CSD on the SCG histomorphometrical changes and the protective effect of curcumin in preventing these changes.

Methods

Thirty-six male rats were randomly assigned to the control, curcumin, CSD, CSD + curcumin, grid floor control, and grid floor + curcumin groups. The CSD was induced by a modified multiple platform apparatus for 21 days and animals were sacrificed at the end of CSD or treatment, and their SCGs removed for stereological and TUNEL evaluations and also spatial arrangement of neurons in this structure.

Results

Concerning stereological findings, CSD significantly reduced the volume of SCG and its total number of neurons and satellite glial cells in comparison with the control animals (P < 0.05). Treatment of CSD with curcumin prevented these decreases. Furthermore, TUNEL evaluation showed significant apoptosis in the SCG cells in the CSD group, and treatment with curcumin significantly decreased this apoptosis (P < 0.01). This decrease in apoptosis was observed in all control groups that received curcumin. CSD also changed the spatial arrangement of ganglionic neurons into a random pattern, whereas treatment with curcumin preserved its regular pattern.

Conclusions

CSD could potentially induce neuronal loss and structural changes including random spatial distribution in the SCG neurons. Deleterious effects of sleep deprivation could be prevented by the oral administration of curcumin. Furthermore, the consumption of curcumin in a healthy person might lead to a reduction of cell death.

Long-term potentiation is differentially expressed in rostral and caudal neurons in the superior cervical ganglion of normal and hypertensive rats

Neurons in the superior cervical ganglia (SCG) are classified as rostral and caudal according to their regional locations. Although diverse phenotypes have been reported for these two subpopulations, differences in neuroplasticity, like long-term potentiation (LTP), have not been characterized. Here, we explored possible regional differences of LTP expression in rostral and caudal neurons of the SCG in control rats, Wistar and Wistar Kyoto (WKy), and in the spontaneously hypertensive rats (SHR) as a model of hypertension. We characterized the expression of gLTP evoked by a tetanic train (40 Hz, 3 s) in an in vitro SCG preparation. gLTP was recorded in rostral and caudal neurons at 8-weeks-old (wo) in Wistar rats, 6-wo and 12-wo in SHR and WKy rats. We found that gLTP was differentially expressed; gLTP was larger in caudal neurons in Wistar and adult WKy rats. In adult 12-wo hypertensive SHR, gLTP was expressed in caudal but not in rostral neurons. In contrast, in 6-wo pre-hypertensive SHR, gLTP was expressed in rostral but not in caudal neurons; while in 6-wo WKy, gLTP was expressed in caudal but not in rostral neurons. The lack of gLTP expression in caudal neurons of 6-wo SHR was not due to a GABAergic modulation because several GABA-A receptor antagonists failed to unmask gLTP. Data show that neuroplasticity, particularly gLTP expression, varied according to the ganglionic region. We propose that differential regional expression of gLTP may be correlated with selective innervation on different target organs.

Localization of peripheral autonomic neurons innervating the boar urinary bladder trigone and neurochemical features of the sympathetic component

The urinary bladder trigone (UBT) is a limited area through which the majority of vessels and nerve fibers penetrate into the urinary bladder and where nerve fibers and intramural neurons are more concentrated. We localized the extramural post-ganglionic autonomic neurons supplying the porcine UBT by means of retrograde tracing (Fast Blue, FB). Moreover, we investigated the phenotype of sympathetic trunk ganglia (STG) and caudal mesenteric ganglia (CMG) neurons positive to FB (FB+) by coupling retrograde tracing and double-labeling immunofluorescence methods. A mean number of 1845.1±259.3 FB+ neurons were localized bilaterally in the L1-S3 STG, which appeared as small pericarya (465.6±82.7 µm²) mainly localized along an edge of the ganglion. A large number (4287.5±1450.6) of small (476.1±103.9 µm²) FB+ neurons were localized mainly along a border of both CMG. The largest number (4793.3±1990.8) of FB+ neurons was observed in the pelvic plexus (PP), where labeled neurons were often clustered within different microganglia and had smaller soma cross-sectional area (374.9±85.4 µm²). STG and CMG FB+ neurons were immunoreactive (IR) for tyrosine hydroxylase (TH) (66±10.1% and 52.7±8.2%, respectively), dopamine beta-hydroxylase (DβH) (62±6.2% and 52±6.2%, respectively), neuropeptide Y (NPY) (59±8.2% and 65.8±7.3%, respectively), calcitonin-gene-related peptide (CGRP) (24.1±3.3% and 22.1±3.3%, respectively), substance P (SP) (21.6±2.4% and 37.7±7.5%, respectively), vasoactive intestinal polypeptide (VIP) (18.9±2.3% and 35.4±4.4%, respectively), neuronal nitric oxide synthase (nNOS) (15.3±2% and 32.9±7.7%, respectively), vesicular acetylcholine transporter (VAChT) (15±2% and 34.7±4.5%, respectively), leuenkephalin (LENK) (14.3±7.1% and 25.9±8.9%, respectively), and somatostatin (SOM) (12.4±3% and 31.8±7.3%, respectively). UBT-projecting neurons were also surrounded by VAChT-, CGRP-, LENK-, and nNOSIR fibers. The possible role of these neurons and fibers in the neural pathways of the UBT is discussed.

Phenotypic alterations of neuropeptide Y and calcitonin gene-related peptide-containing neurons innervating the rat temporomandibular joint during carrageenan-induced arthritis

The aim of this study was to identify immunoreactive neuropeptide Y (NPY) and calcitonin gene-related peptide (CGRP) neurons in the autonomic and sensory ganglia, specifically neurons that innervate the rat temporomandibular joint (TMJ). A possible variation between the percentages of these neurons in acute and chronic phases of carrageenan-induced arthritis was examined. Retrograde neuronal tracing was combined with indirect immunofluorescence to identify NPY-immunoreactive (NPY-IR) and CGRP- immunoreactive (CGRP-IR) neurons that send nerve fibers to the normal and arthritic temporomandibular joint. In normal joints, NPY-IR neurons constitute 78±3%, 77±6% and 10±4% of double-labeled nucleated neuronal profile originated from the superior cervical, stellate and otic ganglia, respectively. These percentages in the sympathetic ganglia were significantly decreased in acute (58±2% for superior cervical ganglion and 58±8% for stellate ganglion) and chronic (60±2% for superior cervical ganglion and 59±15% for stellate ganglion) phases of arthritis, while in the otic ganglion these percentages were significantly increased to 19±5% and 13±3%, respectively. In the trigeminal ganglion, CGRP-IR neurons innervating the joint significantly increased from 31±3% in normal animals to 54±2% and 49±3% in the acute and chronic phases of arthritis, respectively. It can be concluded that NPY neurons that send nerve fibers to the rat temporomandibular joint are located mainly in the superior cervical, stellate and otic ganglia. Acute and chronic phases of carrageenan-induced arthritis lead to an increase in the percentage of NPY-IR parasympathetic and CGRP-IR sensory neurons and to a decrease in the percentage of NPY-IR sympathetic neurons related to TMJ innervation.

Sympathetic nerve activity in the superior cervical ganglia increases in response to imposed increases in arterial pressure

Sympathetic vasoconstriction of cerebral vessels has been proposed to be a protective mechanism for the brain, limiting cerebral perfusion and microcirculatory pressure during transient increases in arterial pressure. To furnish direct neural evidence for this proposition, we aimed to develop a method for recording cerebral sympathetic nerve activity (SNA) from the superior cervical ganglion (SCG). We hypothesized that SNA recorded from the SCG increases during imposed hypertension, but not during hypotension. Lambs (n = 11) were anesthetized (alpha-chloralose, 20 mg.kg(-1).h(-1)) and ventilated. SNA was measured using 25-microm tungsten microelectrodes inserted into the SCG. Arterial blood pressure (AP) was pharmacologically raised (adrenaline, phenylephrine, or ANG II, 1-50 microg/kg iv), mechanically raised (intravascular balloon in the thoracic aorta), or lowered (sodium nitroprusside, 1-50 microg/kg iv). In response to adrenaline (n = 10), mean AP increased 135 +/- 10% from baseline (mean +/- SE), and the RMS value of SNA (Square Root of the Mean of the Squares, SNA(RMS)) increased 255 +/- 120%. In response to mechanically induced hypertension, mean AP increased 43 +/- 3%, and SNA(RMS) increased 53 +/- 13%. Generally, (9 of 10 animals), SNA(RMS) did not increase, as AP was lowered with sodium nitroprusside. Using a new model for direct recording of cerebral SNA from the SCG, we have demonstrated that SNA increases in response to large induced rises, but not falls, in AP. These findings furnish direct support for the proposed protective role for sympathetic nerves in the cerebral circulation.

Macro- and Microstructure of the Superior Cervical Ganglion in Dogs, Cats and Horses during Maturation

The superior cervical ganglion (SCG) provides sympathetic input to the head and neck, its relation with mandible, submandibular glands, eyes (second and third order control) and pineal gland being demonstrated in laboratory animals. In addition, the SCG's role in some neuropathies can be clearly seen in Horner's syndrome. In spite of several studies published involving rats and mice, there is little morphological descriptive and comparative data of SCG from large mammals. Thus, we investigated the SCG's macro- and microstructural organization in medium (dogs and cats) and large animals (horses) during a very specific period of the post-natal development, namely maturation (from young to adults). The SCG of dogs, cats and horses were spindle shaped and located deeply into the bifurcation of the common carotid artery, close to the distal vagus ganglion and more related to the internal carotid artery in dogs and horses, and to the occipital artery in cats. As to macromorphometrical data, that is ganglion length, there was a 23.6% increase from young to adult dogs, a 1.8% increase from young to adult cats and finally a 34% increase from young to adult horses. Histologically, the SCG's microstructure was quite similar between young and adult animals and among the 3 species. The SCG was divided into distinct compartments (ganglion units) by capsular septa of connective tissue. Inside each ganglion unit the most prominent cellular elements were ganglion neurons, glial cells and small intensely fluorescent cells, comprising the ganglion's morphological triad. Given this morphological arrangement, that is a summation of all ganglion units, SCG from dogs, cats and horses are better characterized as a ganglion complex rather than following the classical ganglion concept. During maturation (from young to adults) there was a 32.7% increase in the SCG's connective capsule in dogs, a 25.8% increase in cats and a 33.2% increase in horses. There was an age-related increase in the neuronal profile size in the SCG from young to adult animals, that is a 1.6-fold, 1.9-fold and 1.6-fold increase in dogs, cats and horses, respectively. On the other hand, there was an age-related decrease in the nuclear profile size of SCG neurons from young to adult animals (0.9-fold, 0.7-fold and 0.8-fold in dogs, cats and horses, respectively). Ganglion connective capsule is composed of 2 or 3 layers of collagen fibres in juxtaposition and, as observed in light microscopy and independently of the animal's age, ganglion neurons were organised in ganglionic units containing the same morphological triad seen in light microscopy.

Comparison of target innervation by sympathetic axons in adult wild type and heterozygous mice for nerve growth factor or its receptor trkA

Nerve growth factor (NGF), a neurotrophin required for the survival and maintenance of postganglionic sympathetic neurons, mediates its trophic effects by activation of its high-affinity receptor trkA. Null mutant mice lacking either NGF or trkA have profound sympathetic deficits, thus revealing the vital importance of NGF synthesis in target tissues and trkA expression by sympathetic neurons. In this study, we sought to assess whether sympathetic neurons of the superior cervical ganglion (SCG) display alterations in their neurochemical phenotype in adult mice carrying one mutated allele for either NGF or trkA, and whether such differences result in altered patterns of innervation to the submandibular salivary gland and pineal gland. In comparison with adult siblings, levels of trkA protein in the SCG were reduced in age-matched NGF(+/-) and trkA(+/-) mice. While NGF(+/-) mice also had significantly fewer sympathetic axons innervating both the submandibular salivary gland and pineal gland, densities of sympathetic axons in both tissues reached normal levels in trkA(+/-) mice. These findings reveal that while levels of trkA are reduced in SCG neurons of adult NGF(+/-) and trkA(+/-) mice (compared with their wild type counterparts), sympathetic axons are capable of achieving normal patterns of target innervation in trkA(+/-) mice but not in NGF(+/-) mice. As NGF protein levels are not depleted in the submandibular salivary gland and pineal gland of NGF(+/-) mice, a loss of sympathetic neurons [Nat Neurosci 1999; 2:699-705], in combination with reduced levels of trkA protein, may account for perturbed patterns of sympathetic innervation to peripheral tissues.

Heterogeneous requirement of NGF for sympathetic target innervation in vivo

The neurotrophin nerve growth factor (NGF) plays a crucial role in the development of the sympathetic nervous system. In addition to being required for sympathetic neuron survival in vivo and in vitro, NGF has been shown to mediate axon growth in vitro. The role of NGF in sympathetic axon growth in vivo, however, is not clear because of its requirement for survival. This requirement can be circumvented by a concomitant deletion of Bax, a pro-apoptotic Bcl-2 family member, thus allowing an examination of the role of neurotrophins in axon growth independently of their function in cell survival. Here, we analyzed peripheral sympathetic target organ innervation in mice deficient for both NGF and Bax. In neonatal NGF-/-; Bax-/- mice, sympathetic target innervation was absent in certain organs (such as salivary glands), greatly reduced in others (such as heart), somewhat diminished in a few (such as stomach and kidneys), but not significantly different from control in some (such as trachea). At embryonic day 16.5, peripheral target sympathetic innervation was also reduced in NGF-/-; Bax-/- mice, with analogous variability for different organs. Interestingly, in some organs such as the spleen the precise location at which sympathetic axons become NGF-dependent for growth was evident. We thus show that NGF is required for complete peripheral innervation of both paravertebral and prevertebral sympathetic ganglia targets in vivo independently of its requirement for cell survival. Remarkably, target organs vary widely in their individual NGF requirements for sympathetic innervation.

Distribution of sympathetic and afferent neurones innervating the submandibular gland in the sheep

The distribution of sympathetic and sensory neurones innervating the submandibular gland (SMG) in sheep was studied using retrograde tracing technique. The retrograde tracer Fast Blue (FB) was unilaterally injected into the SMG in five juvenile male sheep under general anaesthesia. After a 4-week survival period, all the animals were reanaesthetized, perfused transcardially with 4% buffered paraformaldehyde and ganglia, which could be considered as a potential sources of sympathetic, and afferent innervation of the gland were bilaterally collected. The FB-labelled sympathetic neurones were found in the ipsilateral superior and middle cervical ganglion. Many labelled neurones were distributed in the ipsilateral jugular and nodose ganglia of the vagus nerve and smaller numbers of the nerve cells were also found in ipsilateral C1-C3 dorsal root ganglia (DRG). No labelled neurones were observed in the ipsilateral stellate ganglion, trigeminal ganglion, C4-C8 DRG and in all contralateral ganglia. The present study revealed that the majority of sympathetic neurones projecting to the sheep SMG are found in the superior cervical ganglion but some of them are also distributed in the middle cervical ganglion. Most of the afferent neurones are located in the jugular and nodose ganglia of vagus nerve but C1-C3 DRG also comprise some of these nerve cells.

Modulation by somatostatin of rat submandibular salivary secretion

Although somatostatin (somatotrophin release inhibitory factor; SRIF) is a well-known inhibitory peptide, there are only a few reports of it acting as a positive modulator. In this work, the action of somatostatin upon rat submandibular protein secretion was studied. In vivo somatostatin infusion (35 microg/(kg h)) raised protein secretion stimulated by adrenergic and peptidergic agents. To rule out possible systemic effects of somatostatin, in vitro experiments were performed. Somatostatin (90 nmol/l) augmented protein release stimulated by noradrenaline (19 micromol/l) and substance P (10 micromol/l), but it did not affect isoprenaline (400 micromol/l)-induced protein release. Phenoxybenzamine (20 micromol/l) reduced the effect of somatostatin on noradrenaline-stimulated protein release. Propranolol (20 micromol/l) increased the noradrenaline-stimulated protein release and this effect was synergistic with the action of somatostatin. The absence of extracellular calcium did not significantly reduce somatostatin enhancement of agonist-induced secretion. Fluorescence measurements of the Ca(2+)-sensitive dye fluo3 showed that cytosolic calcium in acinar cells remained elevated during stimuli when somatostatin was present in the medium. It was concluded that somatostatin modulates rat submandibular protein secretion by prolonging the time that the cytosolic calcium signal remains high after stimulus.

Nicotinic mechanisms in the autonomic control of organ systems

Most visceral organs are under the control of the autonomic nervous system (ANS). Information on the state and function of these organs is constantly relayed to the central nervous system (CNS) by sensory afferent fibers. The CNS integrates the sensory inputs and sends neural commands back to the organ through the ANS. The autonomic ganglia are the final site for the integration of the message traveling from the CNS. Nicotinic acetylcholine receptors (nAChRs) are the main mediators of fast synaptic transmission in ganglia, and therefore, are key molecules for the processing of neural information in the ANS. This review focuses on the role of nAChRs in the control of organ systems such as heart, gut, and bladder. The autonomic control of these organ systems is discussed in the light of the results obtained from the analysis of mice carrying mutations targeted to nAChR subunits expressed in the ANS.

Innervation of the uvea by galanin and somatostatin immunoreactive axons in macaques and baboons

The neuropeptide galanin has not been localized previously in the primate uvea, and the neuropeptide somatostatin has not been localized in the uvea of any mammal. Here, the distribution of galanin-like and somatostatin-like immunoreactive axons in the iris, ciliary body and choroid of macaques and baboons using double and triple immunofluorescence labeling techniques and confocal microscopy was reported. In the ciliary body, galanin-like immunoreactive axons innervated blood vessels and the ciliary processes, particularly at their bases. In the iris, the majority of these axons was associated with the loose connective tissue in the stroma. Somatostatin-like immunoreactive axons were found in many of the same areas of the uvea supplied by cholinergic nerves. In the ciliary body, there were labelled axons within the ciliary processes and ciliary muscle. They were also found alongside blood vessels in the ciliary stroma. In the iris, somatostatin-like immunoreactive axons were abundant in the sphincter muscle and less so in the dilator muscle. A unilateral sympathectomy had no effect on the distribution of somatostatin-like or galanin-like immunoreactive axons, and these axons did not contain the sympathetic marker tyrosine hydroxylase. They did not contain the parasympathetic marker choline acetyltransferase, either. The galanin-like immunoreactive axons contained other neuropeptides found in sensory nerves, including calcitonin gene-related peptide, substance P and cholecystokinin. Somatostatin-like immunoreactive axons did not contain any of these sensory neuropeptides or galanin-like immunoreactivity, and they were neither labelled with an antibody to 200kDa neurofilament protein, nor did they bind isolectin-IB(4). Nevertheless, they are likely to be of sensory origin because somatostatin-like immunoreactive perikarya have previously been localized in the trigeminal ganglion of primates. Taken together, these findings indicate galanin and somatostatin are present in two different subsets of sensory axons in primate uvea.

Evidence for nodose ganglion as the source of innervation to the anterior lobe of the pituitary gland

Recent studies have provided convincing evidence for the presence of peptidergic nerve fibers in the pituitary anterior lobe in several animal species. This study was aimed at elucidating the origin of this innervation by neuroanatomical tracing, denervation experiments, and immunohistochemistry. Immunohistochemistry against substance P and growth-associated protein 43 revealed a dense fiber plexus within the anterior lobe, and these markers were mostly colocalized. Retrograde tracing with Fluorogold from the pituitary gland stained neurons in the hypothalamus, superior cervical ganglia and the nodose ganglia. None of the Fluorogold-labelled neurons in the hypothalamus or superior cervical ganglion were substance P-immunoreactive, while many of the neuronal cell bodies in the nodose ganglion exhibited substance P immunoreactivity. There were no Fluorogold-labelled neurons in the trigeminal, otic or cervical dorsal root ganglia. Surgical transection of the pituitary stalk or bilateral removal of the superior cervical ganglion did not abolish the anterior lobe nerve fibers, and anterograde tracing with 1,1'-dioctadecyl-3,3,3',3'-tetramethylindo-carbocyanine perchlorate from the pituitary stalk failed to stain any nerve fibers within the anterior lobe. Our findings suggest that the nodose ganglion neurons likely innervate the pituitary anterior lobe, while neither hypothalamus nor sympathetic superior cervical ganglion may be a source of this innervation. By showing a distinct neuronal system in the pituitary anterior lobe our findings (i) support the previous functional studies demonstrating a distinct regulation of the morphology of the anterior lobe innervation by hormonal changes, and (ii) suggest that the innervation of the pituitary anterior lobe is a part of the visceral innervation by the vagus nerve rather than a part of the other intracranial innervation. These findings provide a neuroanatomic basis for the reported observations about the neural regulation of the pituitary anterior lobe.

Neuronal organization and cell interactions of the cat stellate ganglion

The functional structure of the cat stellate ganglion (SG) and, in particular, its extra- and intraganglionic connections and neuronal organization, were investigated using histochemical, immunohistochemical, morphological and histological methods. Retrograde axonal transport of horseradish peroxidase was used to determine most of the extraganglionic interactions. Of the targets tested, the most extensive efferent connections of the SG were with the stemocleidomastoid muscle, trachea, esophagus and heart. Neurons of the SG also send a small number of postganglionic efferents to the thyroid and stomach. Furthermore, ganglion cells send axons to the spinal ganglia. Several afferent connections of the SG were determined. Sympathetic preganglionic neurons of segments C8-T10 of the spinal cord, sensory neurons of C8-T9 spinal ganglia, intramural ganglia of the thoracic viscera and the reticular formation of the medulla oblongata send their axons to the SG. Intraganglionic interactions of intemeurons with principal ganglionic cells were assumed to occur, based on the presence of interneurons immunoreactive to GABA and substance P. GABA- and substance P-immunoreactive fibers located around a small number of postganglionic neurons were also identified. Morphological study revealed asymmetry between the left and right ganglia: the right ganglion is larger than the left and contains more cells. This asymmetry was also reflected in basic structural parameters of neurons, such as average neuronal area and average diameter of cell somata. The present data has been used to develop a scheme for the basic inter- and intraneuronal connections of the cat SG. This ganglion is a true nervous center, with postganglionic neurons, some of which might be performing sensory functions, and interneurons. The ganglion is connected not only with the spinal cord and spinal ganglia, but also with neurons of the intramural ganglia and, by direct links, with efferent neurons of the medulla oblongata. Thus, the SG may play an essential role in viscera-visceral reflexes.

Differential control of sympathetic outflow

With advances in experimental techniques, the early views of the sympathetic nervous system as a monolithic effector activated globally in situations requiring a rapid and aggressive response to life-threatening danger have been eclipsed by an organizational model featuring an extensive array of functionally specific output channels that can be simultaneously activated or inhibited in combinations that result in the patterns of autonomic activity supporting behavior and mediating homeostatic reflexes. With this perspective, the defense response is but one of the many activational states of the central autonomic network. This review summarizes evidence for the existence of tissue-specific sympathetic output pathways, which are likely to include distinct populations of premotor neurons whose target specificity could be assessed using the functional fingerprints developed from characterizations of postganglionic efferents to known targets. The differential responses in sympathetic outflows to stimulation of reflex inputs suggest that the circuits regulating the activity of sympathetic premotor neurons must have parallel access to groups of premotor neurons controlling different functions but that these connections vary in their ability to influence different sympathetic outputs. Understanding the structural and physiological substrates antecedent to premotor neurons that mediate the differential control of sympathetic outflows, including those to noncardiovascular targets, represents a challenge to our current technical and analytic approaches.

Reflex patterns in preganglionic sympathetic neurons projecting to the superior cervical ganglion in the rat

Reflex patterns in preganglionic neurons projecting in the cervical sympathetic trunk (CST) were analyzed in response to stimulation of various afferent systems. We focused on the question whether these preganglionic neurons can be classified into functionally distinct subpopulations. Reflex responses were elicited by stimulation of trigeminal and spinal nociceptive, thermoreceptive as well as baroreceptor and chemoreceptor afferents. Multi- and single fiber preparations were studied in baroreceptor intact and sino-aortically denervated animals. Spontaneous activity of 36 preganglionic single neurons ranged from 0.2 to 3.5 imp/s (median= 1.11 imp/s). The degree of cardiac rhythmicity (CR) in the activity of sympathetic neurons was 69.5+/-13% (mean+/-S.D.; N=52; range=39-95%). Noxious stimulation of acral skin activated the majority (67%) of sympathetic preparations by 37+/-25% (N=35) above pre-stimulus activity; 15% were inhibited. In these neurons the response to noxious stimulation of acral skin was significantly correlated with the degree of CR (P<0.001, N=52) in that neurons showing the strongest excitation to noxious stimulation displayed the strongest CR. Noxious mechanical stimulation of body trunk skin (N=60) inhibited the majority (80%) of fiber preparations tested (by 34+/-18% of pre-stimulus activity, N=48); an activation was not observed. Cold stimulation of acral (N=9) and body trunk skin (N=42) activated most fiber preparations. Trigeminal stimulation evoked a uniform reflex activation of preganglionic neurons (+79+/-73% of pre-stimulus activity, N=32). Chemoreceptor stimulation by systemic hypercapnia elicited inhibitory (-31+/-19%, N=8) as well as excitatory (+59+/-5%, N=4) responses. These results show that preganglionic sympathetic neurons projecting to target organs in the head exhibit distinct reflex patterns to stimulation of various afferent systems; however, a clear classification into different functional subgroups did not emerge. Furthermore, reflex patterns showed a segmental organization to noxious cutaneous stimulation of acral parts and body trunk reflecting a differential central integration of spinal afferent input. Compared with the cat the reflex organization of sympathetic neurons projecting to the head seems to be less differentiated in the anesthetized rat.

Remodeling of adult sensory axons in the superior cervical ganglion in response to exogenous nerve growth factor

In previous studies, we found that a 2-week in vivo intracerebroventricular infusion of nerve growth factor (NGF) elicited a sprouting response by sympathetic perivascular axons associated with the intradural segment of the internal carotid artery. We hypothesized that NGF infused into the ventricular system would be internalized by responsive sympathetic cerebrovascular axons, retrogradely transported to parent cell bodies in the superior cervical ganglion (SCG), and subsequently released into the local ganglionic environment. Because fibers exhibiting immunoreactivity for calcitonin gene related peptide (CGRP) have been localized in the SCG, we used immunohistochemical methods to investigate whether a response by CGRP-immunoreactive axons in the SCG occurred following the proposed transport to and release of exogenous NGF in the ganglion. In consecutive tissue sections of the SCG stained for either CGRP or NGF, we found CGRP pericellular 'baskets' surrounding identified NGF-immunoreactive cell bodies. Nerve growth factor infusion resulted in a significant increase both in the number of CGRP pericellular baskets and in NGF-immunoreactive cell bodies. A significant positive correlation (r=0.95, P<0.05) between the pericellular baskets and NGF-immunoreactive cell bodies was observed, suggesting that intracranial projection neurons in the SCG released infused NGF (or possibly a converted signal) into the local ganglionic environment to elicit remodeling of CGRP fibers to form pericellular baskets. These findings were confirmed in sections double labeled for NGF and CGRP immunoreactivity. This remodeling suggests that exogenous NGF may mediate retrograde transneuronal plasticity, allowing for future in vivo examinations of the mechanisms involved in neurotrophin transport and release.

Quantitative differences between kinetic properties of Na(+) currents in postganglionic sympathetic neurones projecting to muscular and cutaneous effectors

The activity of muscular and cutaneous sympathetic neurones has been shown to be differentially regulated. The differences may partially stem from the different ionic channel expression and current kinetics in these neurones, particularly that of Na(+) channels, which play a critical role in action potential generation and modulation of neuronal excitability. The whole cell patch-clamp technique was used to compare the kinetic properties of Na(+) currents in two groups of sympathetic neurones identified by the fluorescent tracer Fast Blue: putative muscular sympathetic neurones (PMSN) and putative cutaneous sympathetic neurones (PSSN). The tracer was injected into the muscular part of the diaphragm (to mark PMSN) and into the skin of the ear (to mark PSSN). Both kinds of neurones expressed fast activating, fast inactivating, voltage dependent and TTX sensitive Na(+) currents. However, the electrical characteristics of the cells were markedly different: (1) The capacitance of PMSN (21.7 pF) was larger than PSSN (12.7 pF). Maximum current in PMSN (3.1 nA) was also larger than in PSSN (2.0 nA). Calculated current density was smaller in PMSN (148.0 pA/pF) than in PSSN (181.1 pA/pF). Slope conductance was larger in PMSN compared to PSSN (102.7 nS and 73.6 nS respectively). (2) V(1/2) of activation for PMSN (-20.9 mV) was more negative than the potential recorded for PSSN (-16.7 mV); the slope factors were not different. (3) V(1/2) for inactivation was more negative for PMSN than for PSSN (-66.3 vs. -60.8 mV); again, the slope factors for inactivation were not different. (4) The rate of recovery from inactivation could be described by the sum of two exponential functions. In PMSN the fast and slow recovery exponential factors tau(f) and tau(s) were 12.6 (66%) and 83.9 (34%) ms, while in PSSN they were shorter and equalled 8.2 (62%) and 41.9 (38%) ms, respectively. We conclude that the Na(+) currents of PMSN and PSSN have different kinetic properties.

Tracing autonomic innervation of the rat pineal gland using viral transneuronal tracing

We have used the neurotropic Bartha strain of pseudorabies virus (PRV) to characterise the pathway linking the endogenous circadian pacemaker of the suprachiasmatic nucleus (SCN) to the pineal gland. This low virulent strain of virus replicates within synaptically linked neurones and is ideally suited to visualise the multisynaptic pathways through which the SCN modulates the activity of the rat pineal gland. Using specific antibodies against PRV, we could follow the immunohistochemical pattern of the spatiotemporal passage of virus through the sympathetic trunk and the neuraxis. The time course of virus infection indicated that the most prominent pathway from the SCN to the pineal gland is via a final sympathetic innervation from the superior cervical ganglion (SCG). The pathway arises in the dorsomedial portion of the SCN from where neurones project to the dorsal parvicellular subdivision of the hypothalamic paraventricular nucleus (PVN) to form synaptic contact with neurones descending to the intermediolateral nucleus (IML) of the upper thoracic spinal cord. The neurones of the IML constitute the presynaptic sympathetic input synaptically connected to postsynaptic sympathetic neurones in the SCG which constitute the final input to the pineal gland. Removal of the superior cervical ganglion (SCGX) prior to viral infection completely abolished infection of neurones in this circuit. However, an additional parasympathetic projection from the superior salivatory nucleus via the sphenopalatine ganglion to the pineal gland was observed in SCGX animals.

Modulation by somatostatin of rat parotid salivary secretion stimulated by cholinergic, adrenergic and peptidergic agents

Although it is well known that somatostatin (SRIF) modulates several digestive functions, there are only a few reports about its effect on the salivary glands. Here, the action of SRIF parotid secretion was studied, in vivo and in vitro, in male Wistar rats. In vivo SRIF infusion (35 microg/kg per hr) inhibited the parotid flow rate stimulated by methacholine, substance P and noradrenaline. The isoprenaline-stimulated flow rate was also decreased by SRIF, but only at highest dose of the secretory agent. Total protein and amylase secretion were studied. SRIF inhibited the total protein secretion stimulated by the above-mentioned agents, except that by isoprenaline. SRIF did not inhibit in vivo amylase secretion. In order to avoid flow-rate interference with total protein and amylase measurements, in vitro experiments were performed. SRIF (25 nM) strongly inhibited the total protein release stimulated by methacholine (5.1 microM), noradrenaline (19 microM), and substance P (10 microM). The inhibitory effect was not raised by the absence of calcium in the incubation medium. However, in vitro amylase release was not affected by SRIF. It was concluded that SRIF modulates rat parotid secretion stimulated by cholinergic, adrenergic and peptidergic agents, acting on any step in the calcium pathway.

Retrogradely transported CTB-saporin kills sympathetic preganglionic neurons

Aiming to ablate sympathetic preganglionic neurons (SPN) innervating a defined target, we injected saporin conjugated to cholera toxin B subunit (CTB) unilaterally into the superior cervical ganglion of rats. In spinal cord segments T1-T3, the numbers of cholinergic neurons in the intermediolateral cell column ipsilateral and contralateral to the injected ganglion were significantly different by 3 days post-injection. By day 14, 77% of ipsilateral cholinergic neurons had disappeared. A higher percentage of neurons were killed in T1-T2 than in T3. Comparing SPN counts from CTB-saporin injected rats and counts from rats receiving unconjugated CTB into the superior cervical ganglion indicated that 84% of SPN supplying the ganglion had died by 14 days. Retrogradely transported CTB-saporin kills sympathetic preganglionic neurons and may also eliminate other types of neurons that transport CTB.

Properties of Na+ currents in putative submandibular and cardiac sympathetic postganglionic neurones

This study was performed to compare the kinetic properties of Na+ currents in putative salivary and cardiac postganglionic sympathetic neurones isolated from the superior cervical and stellate ganglia, respectively. Neurones were labelled with a fluorescent tracer-Fast Blue, injected into the submandibular gland (in the case of salivary neurones) and into the pericardial cavity or left ventricular wall (in the case of cardiac neurones). Voltage-dependent Na+ current was then isolated and recorded from labelled cells. The major findings of this study were: (1) Peak Na+ current was larger in salivary than in cardiac neurones (5.7 nA vs. 2.4 nA; for 30 mM Na+ in extra- and 15 mM in the intracellular solution). (2) The somata of salivary neurones were twice as large as those of cardiac neurones, as indicated by the values of their membrane capacitance (36 pF vs. 18 pF). (3) There was a greater Na+ current density (169 pA/pF vs. 128 pA/pF) in salivary than in cardiac neurones. (4) Recovery from inactivation was faster in salivary neurones with 90% recovery time being 93 ms for salivary and 144 ms in cardiac neurones. (5) Half-activation times were voltage-dependent and consistently longer for salivary than for cardiac neurones. (6) Remaining parameters, such as current threshold, maximum current voltage and kinetics of steady-state inactivation did not significantly differ in salivary compared to cardiac neurones.

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.

Characterization of the multisynaptic neuronal control of the rat pineal gland using viral transneuronal tracing

Knowledge of the polysynaptic pathway conveying photic information to the pineal gland is based upon studies employing lesions, knife cuts and classical tracers. In the present investigation we used viral transneuronal tracing to re-examine the organization of this circuitry. This was accomplished by injecting a neurotropic alpha herpesvirus (pseudorabies virus) into the gland and localizing viral antigen in infected neurones at various postinoculation intervals. This approach is based upon the demonstrated ability of this virus to invade axon terminals, replicate in neurones and pass retrogradely through a multisynaptic circuit. Immunohistochemical localization of viral antigen revealed the progressive appearance of infected neurones in the superior cervical ganglion (SCG), intermediolateral nucleus of the upper thoracic spinal cord (IML), parvicellular subdivisions of the hypothalamic paraventricular nucleus (PVN), and the suprachiasmatic nucleus (SCN). Other infected cell groups known to project to the IML also became infected. Infection of the PVN reproducibly involved neurones in the dorsal, medial and lateral parvicellular subdivisions and preceded the appearance of infected neurones in the SCN and other regions of hypothalamus. Topographic analysis of virus infected neurones within the SCN revealed differential infection of SCN subdivisions that suggested topography in the projection of the SCN to the PVN. Removal of the SCG eliminated infection within the aforementioned circuitry and revealed a parasympathetic innervation from the sphenopalatine ganglion. The data provide further detail on the cellular identity and synaptology of neural circuitry controlling the rhythmic secretion of melatonin by the rat pineal gland.

Neurotrophin receptor and tyrosine hydroxylase gene expression in aged sympathetic neurons

Ribonuclease protection measurements revealed decreases of 26% in p75 neurotrophin receptor mRNA and 30% in trkA mRNA in superior cervical ganglia (SCG) of aged Long-Evans rats. These declines were not related to the presence of a spatial memory impairment, whose presence is known to strongly predict increased hypothalamic-pituitary-adrenal axis activity in these aged animals. A similar decrease with age was observed in p75, but not cyclophilin mRNA levels in SCG from F-344 inbred rats. In situ hybridization with paired sections from mature and aged F-344 rats revealed a 25% decline in the mean neuronal labeling index (LI) for p75 mRNA. In other paired sections, mean trkA LI decreased 16%, tyrosine hydroxylase (TH) LI increased 74% and cyclophilin LI did not change. Neuronal hypertrophy, p75 decreases and TH increases all occurred to a greatest extent in intermediate-sized neurons, resembling those innervating the pineal and cerebral vessels. In contrast to other SCG targets, this innervation is known to decline nearly 50% with aging. Retrograde tracer/in situ hybridization studies will be required to establish whether decreased p75 represents a marker for selective axonal regression and also to determine the significance of increased TH and neuronal hypertrophy.

Cardiac neurones of autonomic ganglia

The properties of the postganglionic sympathetic neurones supplying the heart and arising in the stellate and adjacent paravertebral ganglia of various species are discussed with respect to their location, morphology, synaptic input and membrane characteristics. Results from our laboratory on the morphology of rat stellate neurones projecting to the heart were obtained either by intracellular injection of hexammine cobaltic (III) chloride or by retrograde labelling of cells using cobalt-lysine complex. Intracellular recordings were made from cells using electrodes filled either with potassium chloride plus hexammine cobaltic chloride or potassium acetate. Neurones which projected axons into cardiac nerve branches arising from the stellate ganglion were termed putative cardiac neurones, because of the possibility that some supply pulmonary targets. Putative cardiac neurones had unbranched axons and were ovoid or polygonal in shape, but showed considerable variation in soma size and in the complexity of dendritic trees. The mean two-dimensional surface area was 463 microns2 and the mean number of primary dendrites was seven. Other studies have found that the morphology of rat stellate ganglion neurones is similar to that of superior cervical ganglion cells. However, in strains of rat displaying spontaneous hypertension, dendritic length may be increased. Histochemical studies do not, as yet, seem to have demonstrated a distinctive neurochemical profile for stellate cardiac neurones, but various types of peptide-containing intraganglionic nerve fibres have been identified in the guinea pig. In our electrophysiological studies, putative cardiac neurones were found to receive a complex presynaptic input arising from the caudal sympathetic trunk and from T1 and T2 thoracic rami. In addition, 16% of cardiac neurones received a synaptic input from the cardiac nerve. The properties of postganglionic parasympathetic neurones distributed in the cardiac plexus and termed intrinsic cardiac neurones are discussed, including the results of studies on cultures of these neurones.

Localization, regulation and functions of neurotransmitters and neuromodulators in cervical sympathetic ganglia

Cervical sympathetic ganglia represent a suitable model for studying the establishment and plasticity of neurochemical organization in the nervous system since sympathetic postganglionic neurons: (1) express several neuromediators, i.e., short acting transmitters, neuropeptide modulators and radicals, in different combinations; (2) receive synaptic input from a limited number of morphologically and neurochemically well-defined neuron populations in the central and peripheral nervous systems (anterograde influence on phenotype); (3) can be classified morphologically and neurochemically by the target they innervate (retrograde influence on phenotype); (4) regenerate readily, making it possible to study changes in neuromediator content after axonal lesion and their possible influence on peripheral nerve regeneration; (5) can be maintained in vitro in order to investigate effects of soluble factors as well as of membrane bound molecules on neuromediator expression; and (6) are easily accessible. Acetylcholine and noradrenaline, as well as neuropeptides and the recently discovered radical, nitric oxide, are discussed with respect to their localization and possible functions in the mammalian superior cervical and cervicothoracic (stellate) paravertebral ganglia. Furthermore, mechanisms regulating transmitter synthesis in sympathetic neurons in vivo and in vitro, such as soluble factors, cell contact or electrical activity, are summarized, since modulation of transmitter synthesis, release and metabolism plays a key role in the neuronal response to environmental influences.

Autonomic nervous system as a model of neuronal aging: the role of target tissues and neurotrophic factors

The aim of this study was to determine the role of target tissues and neurotrophic factors in the growth and atrophy of autonomic neurons during development and aging. Using quantitative neuroanatomical techniques, it is shown that, although axonal and dendritic growth is apparent throughout postnatal development, different patterns of growth are found in autonomic neurons innervating different target tissues. For example, sympathetic neurons innervating the submandibular gland continue to grow well into maturity, but those innervating the iris cease net growth early in postnatal development. Similarly, although neuronal atrophy was observed in aged autonomic ganglia, this was not a general phenomenon but was specific to neurons innervating particular target tissues. Sympathetic neurons innervating the middle cerebral artery showed significant axonal and dendritic atrophy in old age, whereas neurons innervating the iris were morphologically unchanged. The trophic influence of peripheral target tissues on their innervating neurons has been shown to decline in old age possibly as a result of decreased availability of target-derived neurotrophic factors such as nerve growth factor (NGF) [Gavazzi et al. (1992) Neuroreport, 3:717-720]. Therefore, in an attempt to reverse neuronal atrophy where it occurred, NGF was infused via miniosmotic pumps over the peripheral axons of aged neurons. NGF induced increases in soma size, dendritic length and axonal arborization. However, in contrast to young adult neurons, no increase in the number of dendritic branch points or primary dendrites was observed, suggesting that some aspects of neuronal plasticity are impaired in old age. In sum, these results show a range of age- and target-specific differences in the axonal and dendritic morphology of autonomic neurons that may result from differing trophic interactions with their target tissues.

Target-dependent plasticity of galanin and vasoactive intestinal peptide in the rat superior cervical ganglion after nerve lesion and re-innervation

The expression of the neuropeptides galanin and vasoactive intestinal peptide (VIP) is increased in subpopulations of sympathetic neurons after axotomy of the rat superior cervical ganglion. We investigated whether postganglionic neurons innervating different targets show a prevalence for any of the two peptides in response to carotid nerve lesion. Before the respective postganglionic axons were crushed close to the ganglion, postganglionic neurons projecting either to the iris (through the internal carotid nerve) or to the submandibular gland (through both carotid branches) were identified by the retrograde tracer Fast Blue. Galanin and VIP immunoreactivities were demonstrated two and 30 days after crush and after successful regeneration of the lesioned neurons (60 days). In control ganglia, both peptides were detected in a few gland- but not in iris-projecting neurons. However, two days after crush of the respective carotid nerves, 14% of neurons within the iris and 46% within the gland population were immunoreactive for galanin. The percentage of neurons immunoreactive for VIP was significantly lower in both populations: only 3.5% of neurons projecting to the iris and 23% of the gland-projecting neuron population exhibited this peptide. After 30 days, the percentage of galanin- and VIP-positive neurons projecting to the submandibular gland was reduced (24% and 5.7%, respectively), whereas the proportion of galanin-immunoreactive neurons further increased within the iris population (55%), indicating that some neurons express galanin at later stages after the lesion. At 60 days after the crush, the percentage of galanin- or VIP-immunoreactive neurons had decreased to control levels within those neuron populations that re-innervated the iris or submandibular gland, although the total number of neurons exhibiting galanin or VIP was still increased within the ganglion, suggesting that re-establishment of target contact may play a role in down-regulation of both peptides.

Target-specific differences in the dendritic morphology and neuropeptide content of neurons in the rat SCG during development and aging

Our purpose in this work was to investigate the role of target tissues in the regulation of dendritic morphology from sympathetic neurons during development and aging. Neurons were retrogradely labeled from three targets, the iris, the submandibular gland (SMG), and the middle cerebral artery (MCA). They were then fixed and intracellularly injected to demonstrate their dendritic arborizations. Dendritic geometry varied quantitatively in sympathetic neurons innervating different target tissues at all stages of development. Neurons innervating the iris had the largest cell bodies and most extensive dendritic arborizations, whereas the vasomotor neurons were the smallest. The number of primary dendrites, however, did not vary significantly between the different neuronal populations. The growth of dendritic arborizations during postnatal development and their atrophy in old age were not concordant in the different neuron populations we studied. Neurons innervating the MCA and the iris ceased dendritic growth early in postnatal development, whereas the dendritic complexity of neurons supplying the SMG increased well into adulthood. By contrast, dendritic atrophy was seen in aged MCA- and SMG-projecting neurons but not in those innervating the iris, suggesting, with other evidence, correlated and distinct patterns of growth and atrophy in axons and dendrites of mature sympathetic neurons projecting to different targets. Swollen dendrites and protuberances on cell soma were a prominent feature of aged neurons. In addition to the target-specific variation in neuronal morphology, we observed diversity in neurotransmitter phenotype. For example, neuropeptide Y was expressed in iridial but not SMG-projecting neurons. These results show a range of age- and target-specific differences in the dendritic morphology and neuropeptide content of sympathetic neurons that may be a result of differing trophic interactions with their target tissues.

The ratio of pre- to postganglionic neurons and related issues in the autonomic nervous system

The motor outflow of the autonomic nervous system (ANS) is differentiated into two major divisions, parasympathetic (PSNS) and sympathetic (SNS). Both are organized hierarchically into pre- and postganglionic levels, but classically the two divisions have been assumed to differ in their ratios of pre- to postganglionic neurons. The PSNS been characterized as having lower ('one-to-few') ratios, whereas the SNS has been described as possessing higher ('one-to-many') ratios. These patterns have been assumed to measure differing divergences of the outflows. In this review, a ratio of pre- to postganglionic neurons is called a ratio index, and the idea that the PSNS and SNS have characteristically different ratio indexes and divergences is called the ratio rule. The putative differences in the ratio indexes of the two divisions - as well as Fulton's influential proposal that they form one of the bases of contrasting functional capacities of the PSNS and SNS - have been widely accepted for nearly for nearly three quarters of a century. A survey of the original observations yielding the concept of the ratio rule as well as the more recent estimates of pre- and postganglionic numbers, however, challenges both the generality and the adequacy of the ratio rule and indexes. The originally formulated differences between the PSNS and SNS represent an overgeneralization since they were based on observations of only two ganglia, the ciliary ganglion in the PSNS and the superior cervical ganglion in the SNS. Furthermore, these original estimates were based on limited samples and were subject to a number of counting artifacts. A survey of the literature suggests that ratio indexes vary much more within each ANS division than they do between the two divisions. When ganglia other than the ciliary and superior cervical are examined, the two divisions of the ANS have broad, largely overlapping ranges of ratio indexes. Additionally, other PSNS-SNS pairs can be found in which the relative sizes of their respective indexes are completely contrary to the ratio rule. For a given ganglion, there are substantial differences in the ratio index between species, between individuals of the same species, and between stages of development in the same species. Furthermore, both divisions of the ANS have wide and largely overlapping ranges of physiological effects varying from specific to diffuse, from local to widespread. Finally, the ratio index measure ignores the degree of convergence found in different ganglia, and it is insensitive to the fact that many ganglia have multiple functionally distinct motor neuron pools, each with separate inputs varying in their degrees of divergence and/or convergence. Thus ratio indexes do not differentiate the PSNS from the SNS, and conclusions based on such putative distinctions are questionable.

In vivo activity of B- and C-neurones in the paravertebral sympathetic ganglia of the bullfrog

1. Spontaneous, in vivo synaptic activity was recorded from 146 B-cells and 60 C-cells in the IXth and Xth paravertebral sympathetic ganglia of the urethane-anaesthetized bullfrog. Sympathetic outflow to the blood vessels, which are innervated by C-cells, is different from that received by targets in the skin, which are innervated by B-cells. 2. B-cells were divided into three groups: the first (61 cells) exhibited only action potentials (APs) at 0.01-0.3 s-1; the second (59 cells) exhibited APs and EPSPs and the third (26 cells) were silent. In addition to their usual suprathreshold input from the ipsilateral sympathetic chain, 53% of B-cells received subthreshold input which probably arose from fibres in the contralateral chain. 'Slow' B-cells exhibited less subthreshold activity and a slightly higher AP frequency than 'fast' B-cells. All B-cells are involved in a sympathetic reflex which is activated by tactile stimulation of the skin of the hindlimb. Activation of this reflex increased AP frequency without promoting long-lasting depolarization. 3. Sixty-seven per cent of C-cells exhibited rhythmic bursting activity with or without small intraburst EPSPs. Bursts tended to correlate with electrocardiographic (ECG) activity. The remainder exhibited an irregular pattern of activity which was not correlated with ECG activity and which included one to three APs and EPSPs interspersed between the bursts. Activity of both types of C-cell was inhibited following stimulation of the skin. 4. An average of twenty-three B-cells and twenty-one C-cells discharge simultaneously in vivo. This reflects branching of preganglionic fibres and results in synchrony of discharge in both postganglionic B- and C-fibres.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of anti-nerve growth factor on retrograde labelling of superior cervical ganglion neurones projecting to the molar pulp in the rat

The aims were to demonstrate sympathetic ganglion neurones projecting to the rat molar pulp and to determine whether deprivation of nerve growth factor (NGF) in neonatal rats eliminates this source of pulpal innervation. Newborn Sprague-Dawley rats were given subcutaneous injections of rabbit anti-mouse-NGF serum for 1 month. Control animals included litter mates treated with preimmune serum and untreated, age-matched rats. AT 4 months of age, Fluoro-gold (FG) was applied to the pulp chamber of the right first maxillary molar. One week later, the animals were perfusion fixed, and the superior cervical ganglia (SCG) were removed, embedded in paraffin, and serially sectioned at 10 microns. FG-labelled cells were detected by epifluorescence microscopy with a u.v. filter set. Control animals had 5-10 FG-labelled neurones widely distributed throughout the SCG ipsilateral to the injection site and no labelled cells in the contralateral SCG. NGF-deprived animals had either no FG-labelled cells or a single labelled cell in the ipsilateral SCG. These results indicate that, in rats, (1) the number of SCG neurones projecting to the molar pulp is rather low, (2) SCG neurones that innervate the dental pulp of the maxillary molar pulp are dispersed throughout the ganglion, (3) the projection from SCG to the molar is exclusively ipsilateral, and (4) neonatal NGF deprivation induces a permanent, almost total, loss of sympathetic neurones projecting to the dental pulp.

Plasticity of postganglionic sympathetic neurons in the rat superior cervical ganglion after axotomy

The neuropeptides galanin (GAL) and vasoactive intestinal polypeptide (VIP) are upregulated in spinal and vagal sensory as well as in cranial motor neurons after axonal transection. In this study an increase of both peptides is demonstrated in axotomized principal ganglionic neurons (PGN) of the rat sympathetic superior cervical ganglion by use of double-labeling immunofluorescence. Compared to control ganglia that do not contain more than 1% GAL- or VIP-positive cells, about 26% of all PGN exhibit GAL immunoreactivity by day 1 after transection of the major postganglionic branches. The proportion of immunoreactive neurons reaches its maximum after 30 days (40%) and decreases to about 27% within the second month after axotomy. The percentage of VIP-positive neurons is much lower than for GAL: 2% of the PGN exhibit VIP immunoreactivity at day 1 and about 7% are observed 30 and 60 days after axotomy. In order to further characterize newly GAL- and VIP-positive PGN, their cell diameters were determined 12 days after axotomy. Compared to the mean overall neuron diameter of 24.8 microns, GAL-immunoreactive neurons are predominantly of small and intermediate size (22.2 microns), whereas VIP occurs mainly in larger neurons (26.1 microns). Besides cell bodies, many intraganglionic nerve fibers stain positive for GAL or VIP, particularly at day 6. Most likely, these fibers represent axons, as indicated by the absence of MAP2, a cytoskeletal protein found in neuronal somata and dendrites. They establish direct membrane contacts with postganglionic perikarya, as revealed by pre-embedding immuno-electron microscopy. Some cell bodies and fibers contain both peptides. Colocalization of GAL or VIP with tyrosine hydroxylase (TH), the rate-limiting enzyme of catecholamine synthesis, reveals a reduced immunoreactivity for TH in intensely GAL- or VIP-positive cells, and vice versa at day 6. However, no difference in staining intensity for VIP or GAL, and TH, is observed after 30 and 60 days. Possible implications of GAL and VIP for peripheral nerve regeneration and their regulation by target-derived factors are discussed.

Sweating and vascular responses in the face: normal regulation and dysfunction in migraine, cluster headache and harlequin syndrome

At least four neural mechanisms influence facial blood flow. Firstly, sympathetic vasoconstrictor fibres exert a tonic constrictor influence on the vasculature of the ears, lips and nose, and sparsely supply other parts of the face. Secondly, the sympathetic nervous system actively dilates the cutaneous vasculature of the face during heat stress and emotion. Thirdly, parasympathetic vasodilator reflexes in the facial and glossopharyngeal nerves increase blood flow to the exocrine glands and tissues of the eyes, nose and mouth when these tissues are irritated. Fourthly, axon reflexes release vasoactive peptides from sensory fibres, which participate in local inflammatory responses. The sympathetic nervous system normally controls facial sweating. However, after injury to postganglionic sympathetic fibres, parasympathetic fibres sometimes make functional connections with sweat glands, so that parasympathetic reflexes provoke pathological sweating. In this review, new information about the neural pathways and stimuli which influence facial sweating and blood flow is summarized, and this is followed by a discussion of the pathophysiology of extracranial vascular disturbances and facial sweating in migraine, cluster headache and harlequin syndrome.

Sensory and autonomic innervation of the rat eyelid: neuronal origins and peptide phenotypes

Neuronal origins, peptide phenotypes and target distributions were determined for sensory and autonomic nerves projecting to the eyelid. The retrograde tracer, Fluoro-Ruby, was injected into the superior tarsal muscle and meibomian gland of Sprague-Dawley rats. Labelled neurons were observed within the pterygopalatine (31 +/- 6 of a total of 8238 +/- 1610 ganglion neurons), trigeminal (173 +/- 43 of 62,082 +/- 5869) and superior cervical ganglia (184 +/- 35 of 21,900 +/- 1741). Immunostaining revealed vasoactive intestinal polypeptide immunoreactivity (VIP-ir) in nearly all Fluoro-Ruby-labelled pterygopalatine ganglion neurons (86 +/- 5%) but only rarely in trigeminal (0.3 +/- 0.3%) or superior cervical (1.4 +/- 1.4%) ganglion neurons. Calcitonin gene-related peptide (CGRP)-ir was not observed in pterygopalatine or superior cervical ganglion somata, but was present in 24 +/- 4% of trigeminal neurons. Bright dopamine beta-hydroxylase (DBH) immunofluorescence was observed in the majority of eyelid-projecting neurons within the superior cervical ganglia (65 +/- 5%) and lighter staining was detected in pterygopalatine neurons (63 +/- 3%), but no DBH-ir was observed in trigeminal neurons. Examination of eyelid sections revealed dense VIP-ir innervation of meibomian gland acini and vasculature and modest distribution within tarsal muscle. CGRP-ir fibers surrounded ductal and vascular elements of the meibomian gland and the perimeter of tarsal muscle. DBH-ir fibers were associated with meibomian gland blood vessels and acini, and were more densely distributed within tarsal muscle. This study provides evidence for prominent meibomian gland innervation by parasympathetic pterygopalatine ganglion VIP-ir neurons, with more restricted innervation by sensory trigeminal CGRP-ir and sympathetic neurons. Tarsal muscle receives abundant sympathetic innervation, as well as moderate parasympathetic and sensory CGRP-ir projections. The eyelid contains substantial non-CGRP-ir sensory innervation, the targets of which remain undetermined. The distribution of identified autonomic and sensory fibers is consistent with the idea that meibomian gland function, as well as that of the tarsal muscle, is regulated by peripheral innervation.

Properties of putative cardiac and non-cardiac neurones in the rat stellate ganglion

Intracellular recordings were made from isolated left or right stellate ganglia of Wistar rats and the morphology of neurones studied after intracellular injection of hexammine cobaltic chloride or back-filling from the post-ganglionic nerve with cobalt lysine complex. The experiments attempted to identify the location, electrophysiological properties, morphology and chemosensitivity of putative cardiac neurones in the ganglion. These were identified by antidromic activation of the axon in a cardiac nerve and compared with neurones projecting towards the brachial plexus (non-cardiac neurones). Putative cardiac neurones were localized in the ganglion around the postganglionic nerve entry zone and showed considerable morphological diversity. They had complex dendritic trees with, on average, seven dendrites. They included both phasic and tonic neurones and were depolarized by muscarinic agonists, angiotensin and substance P; they invariably had a synaptic input from the sympathetic trunk and from a T1 or T2 ramus and, in 16% of cells, from a cardiac nerve. Non-cardiac neurones were more widely scattered through the stellate ganglion but were not clearly different in morphology, resting membrane potential or the proportion of phasic and tonic cells from putative cardiac neurones. They also showed depolarizing responses to muscarinic agonists, angiotensin and substance P. Angiotensin responses of stellate ganglion cells were blocked by the peptide antagonist, saralasin (1 microM).

Daily changes in presynaptic cholinergic activity of rat sympathetic superior cervical ganglion

The in vitro capacity of sympathetic superior cervical ganglia (SCG) to take up [3H]choline from the extracellular medium, to synthesize acetylcholine from [3H]choline, and to release [3H]acetylcholine in response to a high K+ concentration, were examined in rats throughout a 24-h cycle. Both the release of [3H]acetylcholine and the synthesis of [3H]acetylcholine from [3H]choline exhibited significant diurnal variations, showing maxima during the first half of the night. After these maxima, nocturnal acetylcholine release and synthesis decayed to daytime levels and remained low until the end of the night. [3H]Choline uptake by rat SCG did not vary significantly throughout a 24-h period. A 1.5-h exposure of rats to darkness at the 5th hour of light phase of the daily photoperiod did not change significantly any parameter studied. A 20-min, 5-Hz, electrical stimulation of the preganglionic trunk of SCG excised from rats at noon increased significantly subsequent K(+)-induced [3H]acetylcholine release but did not change [3H]acetylcholine synthesis. In decentralized SCG of rats subjected to a unilateral SCG decentralization and a contralateral sham-operation 7 days earlier, [3H]acetylcholine release and synthesis were highly reduced or abolished at the decentralized side, while [3H]choline uptake remained unaltered. The present results suggest that an activation of preganglionic rat SCG neurons takes place during the first half of the scotophase.