Sympathetic noradrenergic neurons containing dynorphin but not neuropeptide Y innervate small cutaneous blood vessels of guinea-pigs

Detailed Characterization of Sympathetic Chain Ganglia (SChG) Neurons Supplying the Skin of the Porcine Hindlimb

It is generally known that in the skin sympathetic fibers innervate various dermal structures, including sweat glands, blood vessels, arrectores pilorum muscles and hair follicles. However, there is a lack of data about the distribution and chemical phenotyping of the sympathetic chain ganglia (SChG) neurons projecting to the skin of the pig, a model that is physiologically and anatomically very representative for humans. Thus, the present study was designed to establish the origin of the sympathetic fibers supplying the porcine skin of the hind leg, and the pattern(s) of putative co-incidence of dopamine-β-hydroxylase (DβH) with pituitary adenylate cyclase-activating polypeptide (PACAP), somatostatin (SOM), neuronal nitric oxide synthase, substance P, vasoactive intestinal peptide, neuropeptide Y (NPY), leu5-enkephalin and galanin (GAL) using combined retrograde tracing and double-labeling immunohistochemistry. The Fast Blue-positive neurons were found in the L₂-S₂ ganglia. Most of them were small-sized and contained DβH with PACAP, SOM, NPY or GAL. The findings of the present study provide a detailed description of the distribution and chemical coding of the SChG neurons projecting to the skin of the porcine hind leg. Such data may be the basis for further studies concerning the plasticity of these ganglia under experimental or pathological conditions.

Visceral motor neuron diversity delineates a cellular basis for nipple- and pilo-erection muscle control

Despite the variety of physiological and target-related functions, little is known regarding the cellular complexity in the sympathetic ganglion. We explored the heterogeneity of mouse stellate and thoracic ganglia and found an unexpected variety of cell types. We identified specialized populations of nipple- and pilo-erector muscle neurons. These neurons extended axonal projections and were born among other neurons during embryogenesis, but remained unspecialized until target organogenesis occurred postnatally. Target innervation and cell-type specification was coordinated by an intricate acquisition of unique combinations of growth factor receptors and the initiation of expression of concomitant ligands by the nascent erector muscles. Overall, our results provide compelling evidence for a highly sophisticated organization of the sympathetic nervous system into discrete outflow channels that project to well-defined target tissues and offer mechanistic insight into how diversity and connectivity are established during development.

Study on the dynamic compound structure composed of mast cells, blood vessels, and nerves in rat acupoint

Background. Circulation system, immunity system, and nervous system have a close relationship with meridian phenomen. However, there is still lack of the results of dynamic changes of these structures in acupoint. The aim of this study is to explore the interrelationship by composite staining techniques. Methodology/Principal Findings. Twenty rats were separated into electroacupuncture group (EA) and control group (Con) randomly. In EA group, the Zusanli and Weishu were stimulated with the 0.1 mA for 25 min. The tissue of these acupoints was double-stained with acetylcholinesterase and Toluidine blue. The compound structure of mast cells, nervous fibers, and mast cells in the acupoint was observed. Conclusions/Significance. The blood vessels, mast cells and acetylcholinesterase responded nerves were clearly observed in acupoint tissues. EA can result in the mast cell recruitment and migration along the blood vessels and nervous bundle, which conformed the dynamic compound structure and played important roles in acupuncture.

Generating diversity: Mechanisms regulating the differentiation of autonomic neuron phenotypes

Sympathetic and parasympathetic postganglionic neurons innervate a wide range of target tissues. The subpopulation of neurons innervating each target tissue can express unique combinations of neurotransmitters, neuropeptides, ion channels and receptors, which together comprise the chemical phenotype of the neurons. The target-specific chemical phenotype shown by autonomic postganglionic neurons arises during development. In this review, we examine the different mechanisms that generate such a diversity of neuronal phenotypes from the pool of apparently homogenous neural crest progenitor cells that form the sympathetic ganglia. There is evidence that the final chemical phenotype of autonomic postganglionic neurons is generated by both signals at the level of the cell body that trigger cell-autonomous programs, as well as signals from the target tissues they innervate.

Atrial and ventricular rat coronary arteries are differently supplied by noradrenergic, cholinergic and nitrergic, but not sensory nerve fibres

The present immunohistochemical study set out to determine the extent of perivascular innervation in the rat heart, using markers for noradrenergic sympathetic fibres (tyrosine hydroxylase = TH), cholinergic parasympathetic fibres (vesicular acetylcholine transporter = VAChT), nitrergic fibres (neuronal NO synthase = nNOS), and peptidergic sensory fibres (calcitonin gene-related peptide = CGRP). For each of these antigens, the vascular innervation density was assessed separately in the atria, the basal and the apical parts of the ventricles, and was correlated to the inner vascular diameter. The four major findings are: (1) Each of these neurochemically defined populations shows an individual distribution pattern significantly different from the others with respect to correlation with vascular diameter and occurrence along atrial versus ventricular vessels. (2) Among autonomic efferent axons, nNOS-containing fibres are far less numerous than cholinergic and noradrenergic fibres. (3) Autonomic efferent axons (noradrenergic, cholinergic, nitrergic) are much more abundant around atrial than ventricular vessels, whereas perivascular CGRP-immunoreactive sensory nerve fibres are equally distributed in the various parts of the heart. (4) Noradrenergic and cholinergic axons preferentially innervate small-diameter vessels (negative linear correlation between index of innervation and vascular diameter), whereas the supply with CGRP-immunoreactive sensory nerve fibres does not change with vascular diameter. Collectively, the present study shows individual distribution patterns for each of the neurochemically defined populations of perivascular axons along the atrial and ventricular coronary arteries, indicating a highly differentiated nervous regulation of atrial versus ventricular, and large-diameter versus resistance vessels.

Functional organization of peripheral vasomotor pathways

AIM

In this article, we review the functional organization of the peripheral autonomic pathways regulating the vasculature.

RESULTS

The final motor neurones in vasomotor pathways tend to be smaller than neurones in other autonomic pathways. This suggests that they have relatively smaller target territories and receive fewer pre-ganglionic inputs than non-vasomotor neurones. Nevertheless, single vasomotor neurones project to large areas of the vasculature separated by up to 7 mm. Different functional pools of vasomotor neurones project to specific segments of the vasculature, allowing for the selective neural control of resistance in vessels in proximal or distal regions of the vascular bed. In many cases, each functional pool of vasomotor neurones utilizes a characteristic combination of cotransmitters. The various pools of final motor neurones in vasomotor pathways receive convergent synaptic input from different pools of pre-ganglionic neurones, many of which also contain neuropeptides which enhance the excitability of the final motor neurones. The excitability of vasomotor neurones regulating gastrointestinal and mesenteric blood flow, also can be increased by the actions of peptides such as substance P that are released from visceral nociceptors.

CONCLUSIONS

We propose that autonomic pathways regulating the vasculature are organized into 'vasomotor units'. Each vasomotor unit consists of a pre-ganglionic neurone, the final motor neurones it innervates, and the blood vessels that they regulate. The vasomotor units are likely to be grouped into functional pools that can be recruited as necessary to provide highly specific, graded control of blood flow both within and between vascular beds.

Neuropeptide Y immunoreactivity in cutaneous sympathetic and sensory neurons during development of the guinea pig

Different levels of the cutaneous vasculature are innervated selectively by subpopulations of sympathetic neurons distinguished by the presence or absence of immunoreactivity (-IR) for neuropeptide Y (NPY). This study used multiple-labelling immunohistochemistry to examine the appearance of NPY-IR in neurons innervating cutaneous vessels in the ear pinna of embryonic, fetal, and neonatal guinea pigs. NPY-immunoreactive axons were detected in the ear bud at embryonic day 25. However, these axons lacked IR for tyrosine hydroxylase (TH) and often ran in bundles with substance P (SP)-immunoreactive axons close to the epidermis. Many neuronal somata in the cervical dorsal root ganglia (DRG) at late embryonic stages contained NPY-IR with or without SP-IR, but no NPY-IR was detected in DRG or subepidermal axons by late fetal stages. IR for calcitonin gene-related peptide increased in DRG neurons from midfetal to late fetal stages, after the decrease in NPY-IR. Populations of TH-IR neurons with or without NPY-IR were present in the superior cervical ganglion (SCG) from midembryonic stages. TH-immunoreactive axons were not detected in the ear pinna until midfetal stages, when axons with TH-IR and NPY-IR innervated proximal arteries and TH-immunoreactive axons without NPY-IR innervated distal vessels. Vasoactive intestinal peptide-IR was detected transiently in most fetal SCG neurons with TH-IR and NPY-IR but was not detected in cutaneous axons. These results demonstrate that selective expression of NPY by subpopulations of sympathetic neurons occurs prior to innervation of their targets. This suggests that target contact is not required to establish appropriate patterns of expression of peptide neurotransmitters by cutaneous sympathetic neurons.

Heterogeneous control of blood flow amongst different vascular beds

The control and maintenance of vascular tone is due to a balance between vasoconstrictor and vasodilator pathways. Vasomotor responses to neural, metabolic and physical factors vary between vessels in different vascular beds, as well as along the same bed, particularly as vessels become smaller. These differences result from variation in the composition of neurotransmitters released by perivascular nerves, variation in the array and activation of receptor subtypes expressed in different vascular beds and variation in the signal transduction pathways activated in either the vascular smooth muscle or endothelial cells. As the study of vasomotor responses often requires pre-existing tone, some of the reported heterogeneity in the relative contributions of different vasodilator mechanisms may be compounded by different experimental conditions. Biochemical variations, such as the expression of ion channels, connexin subtypes and other important components of second messenger cascades, have been documented in the smooth muscle and endothelial cells in different parts of the body. Anatomical variations, in the presence and prevalence of gap junctions between smooth muscle cells, between endothelial cells and at myoendothelial gap junctions, between the two cell layers, have also been described. These factors will contribute further to the heterogeneity in local and conducted responses.

Pathway specific expression of neuropeptides and autonomic control of the vasculature

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

Kinetic and pharmacological properties of Ca(2+) currents in postganglionic sympathetic neurones projecting to muscular and cutaneous effectors

Voltage-gated Ca(2+) channels are expressed in neurones and greatly influence neuronal activity by activating Ca(2+)-dependent K(+) channels. The whole cell patch-clamp technique was used to compare the kinetic and pharmacological properties of voltage-dependent Ca(2+) currents in two groups of sympathetic neurones identified by the fluorescent tracer Fast Blue: putative muscular sympathetic neurones (MSN) and putative cutaneous sympathetic neurones (CSN). The tracer was injected into the muscular part of the diaphragm (to mark MSN) and into the skin of the ear (to mark CSN). The capacitance of MSN (23.0 pF) was larger than the capacitance of CSN (12.6 pF). The maximum current in MSN (1.3 nA) was also larger than in CSN (0.93 nA). However, the current density was larger in CSN (77. 3 pA/pF) than in MSN (57.7 pA/pF) and the current activation rate was faster in CSN (0.27 nA/ms) than in MSN (0.19 nA/ms). V(1/2) and slope factors of activation and inactivation were not significantly different for MSN and CSN. The majority of Ca(2+) current was available for activation in both categories of neurones at resting membrane potential. Ca(2+) currents in MSN and CSN were blocked by nifedipine (7.0 and 3.6%, respectively), omega-Agatoxin-IVA (23.0 and 25.6%, respectively) and omega-conotoxin-GVIA (67.0 and 65.1%, respectively). We found that CSN are twice as small, have higher Ca(2+) current density and their Ca(2+) activation rate is faster in comparison to MSN. Such properties may lead to faster rise of Ca(2+) concentration in the cytoplasm of the CSN comparing to MSN and more effectively dampen their activity due to more effective activation of Ca(2+)-dependent K(+) current. Both kinds of neurones express high proportion of N and P/Q Ca(2+) current.

Neuronal morphology and the synaptic organisation of sympathetic ganglia

In this article, we provide a short review of the structure and synaptic organisation of the final motor neurons in the sympathetic ganglia of mammals. Combinations of pathway tracing, multiple-labelling immunofluorescence and intracellular dye injection have shown that neurons in different functional pathways differ not only in their patterns of neuropeptide expression, but also in the size of their cell bodies and dendritic fields. Thus, vasoconstrictor neurons consistently are smaller than any other major functional class of neurons. Serial section ultrastructural analysis of dye filled neurons, together with electron microscopic and confocal microscopic analysis of immunolabelled synaptic inputs to sympathetic final motor neurons indicate that synapses are rare and randomly distributed over the surface of the neurons. The total number of synapses is simply proportional to the total surface area of the neurons. Many terminal boutons of peptide-containing preganglionic neurons do not make conventional synapses with target neurons. Furthermore, there is a spatial mismatch in the distribution of peptide-containing terminals and neurons expressing receptors for the corresponding peptides. Together, these results suggest that there are likely to be significant differences in the ways that the final sympathetic motor neurons in distinct functional pathways integrate their synaptic inputs. In at least some pathways, heterosynaptic actions of neuropeptides probably contribute to subtle modulation of ganglionic transmission.

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.

Heterogeneity of vascular innervation in hamster cheek pouch and retractor muscle

The hamster cheek pouch and its retractor muscle have provided valuable insights into microvascular physiology of an epithelial tissue and striated muscle, respectively. Nevertheless, the innervation of these vascular beds has not been resolved. This study has investigated the nature of autonomic and sensory innervation of these vascular beds and has tested whether it varies within or between tissues. Multiple-labelling immunohistochemistry identified autonomic and peptide-containing sensory nerve fibres. Presumptive sympathetic vasoconstrictor axons with immunoreactivity (IR) for tyrosine hydroxylase (TH) and neuropeptide Y (NPY) innervated feed arteries and arterioles (but not veins or venules) of the retractor and anterior (muscular) cheek pouch; these axons were absent from the posterior (epithelial) region of the cheek pouch, as confirmed by catecholamine fluorescence. Presumptive autonomic vasodilator axons with IR for vasoactive intestinal peptide (VIP) consistently innervated feed arteries and proximal arterioles of the cheek pouch, but generally not those of the retractor muscle nor distal arterioles of either tissue. Sparse presumptive sensory axons with IR for calcitonin gene-related peptide (CGRP) and substance P were found near arterial and venous vessels in all regions of the cheek pouch and retractor muscle; CGRP-IR was also located in motor end plates associated with striated muscle fibres. Such regional differences in vascular innervation by autonomic and sensory neurons may selectively effect local and regional control of blood flow between and within vascular beds.

Cotransmission from sympathetic vasoconstrictor neurons to small cutaneous arteries in vivo

This study has characterized constrictions of small cutaneous arteries in the guinea pig ear in response to electrical stimulation of the cervical sympathetic nerve (SNS) in vivo. Video microscopy and on-line image analysis were used to examine diameter changes of ear arteries (80-140 micrometers resting diameter) in anesthetized guinea pigs. Trains of 50-300 impulses, but not single pulses or short trains, produced frequency-dependent (2-20 Hz) constrictions. The purinoceptor antagonist suramin (30 microM) greatly reduced constrictions produced by exogenous ATP but did not affect constrictions produced by SNS at 10 Hz or exogenous norepinephrine. The alpha(2)-adrenoceptor antagonist yohimbine (1 microM) enhanced the peak amplitude of sympathetic constrictions at lower stimulation frequencies (1-5 Hz). The amplitude of constrictions to SNS at 10 Hz was reduced, and the latency of constrictions was increased by the alpha(1)-adrenoceptor antagonist prazosin (1 microM). Constrictions to SNS at 10 Hz remaining after prazosin treatment were reduced in amplitude by dihydroergotamine (2 microM) and were attenuated further by the neuropeptide Y Y(1)-receptor antagonist 1229U91 (0.3 microM). Thus norepinephrine and neuropeptide Y act as cotransmitters to mediate sympathetic constriction of small ear arteries at higher stimulation frequencies (10 Hz), but ATP does not seem to contribute directly to these constrictions.

Two populations of sympathetic neurons project selectively to mesenteric artery or vein

The objective of this study was to determine whether sympathetic neurons of the inferior mesenteric ganglion (IMG) projecting to mesenteric arteries could be distinguished by their localization, neurochemical phenotype, and electrophysiological properties from neurons projecting to mesenteric veins. In an in vitro intact vasculature-IMG preparation, neurons were labeled following intraluminal injection of Fluoro-Gold or rhodamine beads into the inferior mesenteric artery (IMA) or vein (IMV). The somata of neurons projecting to IMA were localized in the central part of the IMG, whereas those projecting to IMV were localized more peripherally. None of the labeled neurons was doubly labeled. Neuropeptide Y immunoreactivity was found in 18.9% of neurons innervating the IMA, but not in neurons innervating the IMV. Identified neurons were dissociated and characterized using whole cell patch-clamp recording. After direct soma depolarization, all of the labeled arterial and venous neurons were classified as tonic firing, compared with only 40% of unlabeled neurons; the remaining 60% of unlabeled neurons were phasic firing. The results indicate that IMG neurons projecting to mesenteric arteries are distinct from neurons projecting to mesenteric veins.

Nervous control of blood flow in the orofacial region

The blood vessels of orofacial tissues are innervated by cranial parasympathetic, superior cervical sympathetic, and trigeminal nerves, a situation somewhat different from that seen in body skin. This review summarizes our current knowledge of the nervous control of blood flow in the orofacial region, and focuses on what we know of the respective roles of sympathetic, parasympathetic, and trigeminal sensory nerves in the regulation of blood flow in this region, with particular attention being paid to the mutual interaction between them.

Regional differences in sympathetic neurotransmission to cutaneous arteries in the guinea-pig isolated ear

The effects of sympathetic nerve stimulation on different cutaneous arteries were examined in arteries isolated from guinea-pig ears, by measuring membrane potential changes in smooth muscle cells in response to electrical field stimulation. Resting membrane potential (RMP) was similar in proximal (main ear artery) and distal (3rd or 4th branch order) cutaneous arteries (mean -71 mV). Single stimuli evoked excitatory junction potentials (EJPs) in all arteries. The EJPs in proximal arteries were twice the amplitude, and the time constant of EJP decay was almost half the value, compared with distal cutaneous arteries. EJP amplitude was reduced by > 90% by suramin (30 microM) or alpha,beta,methylene-ATP (alpha,beta,m-ATP)(1 microM) in all proximal, and most distal arteries. Residual responses in distal arteries were resistant to tetrodotoxin. The N-type calcium channel blocker, omega-conotoxin GVIA (30 nM), reduced EJP amplitude by 70-100% in both proximal and distal arteries. Successive EJPs evoked by trains of stimuli at 1 to 5 Hz were depressed in amplitude in proximal arteries, but showed facilitation in distal arteries. EJP depression in proximal arteries was reversed to facilitation by the alpha2-adrenoceptor antagonist, yohimbine (30 nM). Trains of stimuli delivered at 10-20 Hz produced summation of EJPs and active membrane responses in 30% of proximal arteries. Active responses were never detected in distal arteries. Slow depolarizations following the EJPs were detected in most arteries after trains of stimuli, and were abolished by prazosin (0.3 microM) or omega-conotoxin GVIA (30 nM). The density of the perivascular plexus of axons innervating proximal arteries, demonstrated with catecholamine fluorescence histochemistry, was twice that in distal cutaneous arteries. These regional differences in sympathetic neurotransmission suggest that cutaneous vasoconstriction in response to thermoregulatory stimuli, which occurs predominantly in distal cutaneous segments, is likely to be qualitatively different from cutaneous vasoconstriction of proximal arteries in response to other physiological stimuli.

Coexistence of enkephalin- and tyrosine hydroxylase-like immunoreactivities in nerve fibers of the temporomandibular joint capsule of the guinea pig

BACKGROUND

The innervation of joints has been suggested to play an important role for their normal function as well as for the pathogenesis of chronic arthritic conditions. It is therefore important to elucidate the functional anatomy of this innervation.

METHODS

The expression of methionine enkephalin-like immunoreactivity (ENK-LI) and tyrosine hydroxylase (TH)-LI as well as their possible colocalization were examined in the temporomandibular joint of the guinea pig:

RESULTS

Nerve fibers with ENK-LI were demonstrated in the synovium of the guinea pig temporomandibular joint capsule with the use of indirect immunofluorescence. The ENK+ fibers were found close to the surface of the synovial membrane, deeper in the synovium, and at the walls of blood vessels. Coexistence of ENK- and TH-LI was observed frequently in the synovial nerve fibers. After removal of the superior cervical ganglion (SCG), the ENK-containing nerve fibers were reduced substantially in number on the operated side or were completely absent if the cervical sympathetic trunk was also excised.

CONCLUSIONS

The findings indicate that the majority of fibers with ENK-LI derive from the SCG ENK may act as a neuromodulator on the catecholaminergic nerves and may also have an analgesic effect in the joint.

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

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

Carotid bifurcation pressure modulation of spontaneous activity in external and internal carotid nerves can occur in the superior cervical ganglion

Previous reports have suggested that a peripheral pressure-modulated reflex operates at the level of the superior cervical ganglion to alter evoked activity in the postganglionic nerves of the ganglion in both the cat and rabbit. In the present study we have examined if spontaneous activity of the external and internal carotid nerves of the rabbit superior cervical ganglion can be modulated during changes of the carotid bifurcation pressure (CBP), independent of central nervous system (CNS) integration. For external carotid nerve recordings increases in CBP resulted in a reduction in spontaneous activity while decreases in CBP were associated with an increase in spontaneous activity. For internal carotid nerve recordings similar effects were observed in the majority of recordings although a subset of recordings showed opposite effects or were not responsive to changes in pressure. To determine if vagus nerve afferents contribute to the observed pressure-modulated spontaneous activity effects, the influence of CBP on external carotid nerve recordings was examined before and after section of the vagus nerve rostral to the nodose ganglion. We found that even following section of the vagus nerve the external carotid nerve response to an increase in pressure remained intact. These results demonstrate that, after section of centrally-projecting afferent pathways from the carotid bifurcation to the CNS, changes in CBP can still modify spontaneous sympathetic activity of the rabbit superior cervical ganglion. The data reinforce previous findings related to evoked responses in the postganglionic nerves and also suggest that a pressure-modulated reflex, integrated at the level of the superior cervical ganglion, can influence ongoing sympathetic nervous outflow from the superior cervical ganglion in the rabbit.

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.

Sympathetic vasoconstrictor neurons projecting from the guinea-pig superior cervical ganglion to cutaneous or skeletal muscle vascular beds can be distinguished by soma size

We have used a combination of retrograde axonal tracing and intracellular dye injections to determine the soma size of sympathetic vasoconstrictor neurons projecting from the superior cervical ganglion to the cutaneous vascular bed of the eartips, or to the vascular beds of the masseter muscle, of guinea-pigs. Neurons projecting to vasculature of the masseter muscle had a cross-sectional area of 956 +/- 295 microns2 (mean +/- SD; n = 45 cells) and were significantly larger than neurons projecting to the vasculature of the eartip skin (mean cross-sectional area +/- SD, 604 +/- 251 microns2; n = 39 cells). These results are consistent with physiological observations showing that muscle vasoconstrictor neurons have faster conduction velocities than cutaneous vasoconstrictor neurons. Furthermore, they suggest that muscle vasoconstrictor neurons may innervate a larger volume of vasculature compared with cutaneous vasoconstrictor neurons.

Peptides as neurotransmitters in vascular autonomic neurons

1. Neuropeptides are present in the majority of autonomic neurons projecting to blood vessels, where they are co-localized with non-peptide transmitters and sometimes with other peptides. 2. Neuropeptides are released from vasoconstrictor and vasodilator nerve terminals after high frequency stimulation ( > 2-5Hz) with trains of impulses. 3. Neuropeptides can have potent post-synaptic effects on vascular tone, but often these effects are restricted to selected regions of the vasculature. 4. Post-synaptic effects of neuropeptides tend to be more slowly-developing and more long-lasting than those of non-peptide transmitters. 5. Autonomic vasoconstrictor and vasodilator responses often have multiple phases, with the faster phases being mediated by non-peptide transmitters and the slower phases medicated predominantly by one or more neuropeptides. 6. Some neuropeptides do not seem to have post-synaptic effects in a particular vascular bed, but can have presynaptic actions on neurotransmitter release. 7. Neuropeptides form an important component of the repertoire of neurotransmitters used by vascular autonomic neurons to regulate regional blood flow in response to a range of physiological stimuli.

Existence and co-existence of vasoactive substances in nerve fibres supplying the abdomino-pelvic arterial tree of the female pig and cow

The occurrence and co-localization of several presumed vasoactive neuropeptides, serotonin, and catecholamine-synthesising enzymes--tyrosine hydroxylase (TH), dopamine-beta-hydroxylase (D beta H) and phenylethanolamine-N-methyltransferase (PNMT)--were investigated in perivascular nerves supplying the systemic and distributing arteries of the abdomino-pelvic arterial tree of the female pig and certain arteries supplying female reproductive organs in the cow. As revealed by single immunofluorescence, perivascular axons immunoreactive for TH, D beta H, neuropeptide Y (NPY), vasoactive intestinal polypeptide (VIP), substance P (SP), calcitonin gene-related peptide (CGRP) and Leu-enkephalin (LENK) occurred in both species examined, whereas galanin-immunoreactive (GAL-IR) nerve fibres were found exclusively in the pig. PNMT-, serotonin-, dynorphin A-, alpha-neoendorphin-, bombesin- or cholecystokinin-IR nerve terminals were not observed. The following classes of perivascular nerve fibres might be distinguished in the present study: 1) noradrenergic (i.e. TH/D beta H-IR), 2) NPY-, 3) GAL- (pig only), 4) LENK-, 5) VIP-, 6) SP-, 7) VIP/NPY-, 8) SP/CGRP-, 9) SP/GAL- (pig only), 10) SP/VIP- (cow only), 11) TH/D beta H/NPY- and 12) TH/D beta H/NPY/LENK-IR. Distinct differences in the distribution of LENK- and SP-IR axons around particular parts of the studied arterial tree in individual species were also observed. The present data indicate that the abdomino-pelvic arterial tree of the pig and cow receive perivascular nerve fibres that exhibit diverse chemical codes, and that different chemical coding of perivascular nerve fibres in individual species may depend on the target organ of the particular artery.

Plurichemical transmission and chemical coding of neurons in the digestive tract

The enteric nervous system contains neurons with well-defined functions. However, when neurons of the same function are examined in different regions or species, they are found to show subtle differences in their pharmacologies of transmission and different chemical coding. Individual enteric neurons use more than one transmitter, i.e., transmission is plurichemical. For example, enteric inhibitory neurons have three or more primary transmitters, including nitric oxide, vasoactive intestinal peptide, and possibly adenosine triphosphate and pituitary adenylyl cyclase activating peptide. Primary transmitters are highly conserved, although their relative roles vary considerably between gut regions. Multiple substances, including transmitters and their synthesizing enzymes and nontransmitters (such as neurofilament proteins), provide neurons with a chemical coding through which their functions and projections can be identified. Although equivalent neurons in different regions have the same primary transmitters, other chemical markers differ substantially. Caution must be taken in extrapolating pharmacological and neurochemical observations between species or even between regions in the one species. On the other hand, careful interregion and interspecies comparisons lead to an understanding of the features of enteric neurons that are highly conserved and can be used in valid extrapolation.

New insights into the local regulation of blood flow by perivascular nerves and endothelium

Blood flow, particularly in the skin, is essential for the success of plastic surgical operations. This review describes recent studies of the perivascular nerves and vascular endothelial cells which regulate blood flow. Perivascular nerves, once considered simply adrenergic or cholinergic, release many types of neurotransmitters, including peptides, purines and nitric oxide. Cotransmission (synthesis, storage and release of more than one transmitter by a single nerve) commonly takes place. Some afferent nerves have an efferent (motor) function and axon reflex control of vascular tone by these "sensory-motor" nerves is more widespread than once thought. Endothelial cells mediate both vasodilatation and vasoconstriction. The endothelial cells can store and release vasoactive substances such as acetylcholine (vasodilator) and endothelin (vasoconstrictor). The origins and functions of such vasoactive substances are discussed. Endothelial vasoactive substances may be of greater significance in the response of blood vessels to local changes while perivascular nerves may be concerned with integration of blood flow in the whole organism. The dual regulation of vascular tone by perivascular nerves and endothelial cells is altered by aging and conditions such as hypertension, as well as by trauma and surgery. Studies of vascular tone in disease and after denervation or mechanical injury suggest possible trophic interactions between perivascular nerves and endothelial cells. Such trophic interactions may be important for growth and development of the two control systems, particularly in the microvasculature where neural-endothelial separation is small.

Blockade of noradrenaline-induced constrictions by yohimbine and prazosin differs between consecutive segments of cutaneous arteries in guinea-pig ears

1. The study has examined the receptors mediating constriction produced by brief local application of noradrenaline (NA) to cutaneous arteries and arterioles in the ear vasculature of anaesthetized guinea-pigs. The innervation of the corresponding vascular segments has been examined immunohistochemically at the conclusion of the pharmacological experiments. 2. Small arteries of branch order 4 (4 degrees, 40-110 microns internal diameter) were more sensitive to the vasoconstrictor action of NA than were more proximal arteries of branch order 3 (3 degrees, 60-150 microns internal diameter), or more distal arteries and arterioles of branch orders 5 to 7 (5 degrees-7 degrees, 18-85 microns internal diameter). This higher sensitivity of 4 degrees arteries was maintained after blockade of neuronal uptake with desipramine (1 microM), and after blockade of beta-adrenoceptors with propranolol (1 microM). 3. NA-induced vasoconstrictions of distal arterioles (5 degrees-7 degrees) were abolished or greatly reduced by yohimbine (1 microM). The blockade by yohimbine decreased progressively with increasing vessel diameter of proximal arteries, while the blockade by prazosin (1 microM) increased progressively in arteries > 40 microns diameter. 4. In 3 degrees and 4 degrees arteries, a substantial component (approximately 50%) of NA-induced vasoconstrictions remained after combined treatment with yohimbine and prazosin, in the presence or absence of desipramine. These constrictions were not further reduced by benextramine (1-10 microM), but were abolished by dihydroergotamine (1-10 microM). Constrictions induced by ATP (0.1-1 mM) were not affected by dihydroergotamine. 5. 5-Hydroxytryptamine (3-100 microM) had a variable effect on 3 degree and 4 degree arteries including: concentration dependent constrictions (n = 3); small constrictions at some concentrations, and dilatations or no change in diameter at other concentrations (n = 6); concentration-dependent dilatations only (n = 3). The 5-HT2 receptor antagonist, ketanserin (0.1-0.3 micro M), did not affect NA-induced constrictions.6. In 16 arterial segments ranging from 3 degree arteries to 60 arterioles, there was a significant correlation between the presence of neuropeptide Y-immunoreactive (NPY-IR) sympathetic axons and the degree of blockade of NA-induced constrictions by yohimbine, prazosin and dihydroergotamine.7. These results demonstrate marked differences in the postsynaptic adrenoceptors mediating vasoconstriction to a bolus of NA applied briefly to the adventitial surface of different segments of the cutaneous vasculature of the guinea-pig ear. Furthermore, the presence or absence of adrenoceptors sensitive to blockade by yohimbine or prazosin is related to the proportion of sympathetic axons innervating each vascular segment which contain NPY-IR.

Roles of noradrenaline and ATP in sympathetic vasoconstriction of the guinea-pig main ear artery

This study has investigated the roles of noradrenaline (NA) and adenosine 5'-triphosphate (ATP) in sympathetic vasoconstriction of the main ear artery from guinea-pigs. A range of agents which interact with adrenoceptors or purinoceptors was tested on contractions produced by exogenous NA or ATP, and on contractions produced by transmural stimulation of sympathetic axons. Contractions produced by NA were antagonized competitively by prazosin (Schild plot slope 0.88 +/- 0.13, not significantly different from 1.0). Dihydroergotamine (10 microM) produced significant depression of contractions produced by all concentrations of NA. Yohimbine (1 microM) caused a small rightward shift in the NA concentration-response curves (0.34 log units), whereas propranolol had no effect. alpha,beta,m-ATP (6 microM) enhanced contractions produced by low concentrations of NA (0.1-1 microM), whereas suramin (30 microM) produced a slight depression in the maximum NA-induced contraction in all experiments. Contractions produced by ATP (0.1 mM) were greatly reduced by suramin (30 microM; 59% reduction) and by alpha,beta,m-ATP (6 microM); 96% reduction), and were slightly depressed by dihydroergotamine (10 microM; 12% reduction). Transmural electrical stimulation with trains of 200-300 pulses produced contractions which were rapid in onset and recovery, and sometimes were biphasic. Contractions at both 5 Hz and 20 Hz were reduced by 50-70% after treatment with prazosin (0.1-1 microM). The remaining contractions were enhanced significantly by yohimbine (1 microM), were reduced very slightly by dihydroergotamine, and were largely abolished by guanethidine (1 microM). alpha,beta,m-ATP (1-100 microM) alone often enhanced neurogenic contractions (by 100-200%), whereas suramin (30 microM) alone reduced contractions by 48%.(ABSTRACT TRUNCATED AT 250 WORDS)

Intracellular recording from sympathetic preganglionic neurons in cat lumbar spinal cord

Sympathetic preganglionic neurons (SPN) are responsible for the control of many autonomic targets including the heart and blood vessels. Previous intracellular studies have examined the morphology of SPN in the thoracic spinal cord, but there are no intracellular studies of SPN in the lumbar spinal cord. In this study we identified lumbar SPN using intracellular recording and dye-filling so that we could study their entire soma-dendritic tree, as well as their axons. At the same time, axonal conduction velocity was measured, and any evidence of an input in phase with phrenic nerve discharge was noted. Intracellular recordings were made from SPN in the L3 (n = 125) and T3 (n = 17) segments of the cat spinal cord. Axonal conduction velocities ranged from 0.6-8.4 m/s. In 85 lumbar SPN, the recordings lasted long enough to assess respiratory-related modulation. A respiratory-related modulation of the membrane potential was seen in 7 of these 85 neurons. All 7 respiratory-related neurons had a conduction velocity of 2.0 m/s or less, while none of the SPN with conduction velocities of more than 2.0 m/s had a respiratory rhythmicity. Histological analysis of 50 biocytin-filled SPN, including 3 with a respiratory-related modulation of their membrane potential, revealed that they occurred mostly in the principal part of the intermediolateral cell column and tended to be elongated in the rostro-caudal direction. Dendrites ramified in the intermediolateral cell column, the dorsolateral white matter and the ventral and medial gray matter. Axons arose either from cell bodies or from primary dendrites and did not bifurcate or have varicose intraspinal collaterals. This is the first report of the morphology of intracellularly filled SPN in the lumbar spinal cord.

Selective constriction of small cutaneous arteries by NPY matches distribution of NPY in sympathetic axons

This study has begun to investigate some functional implications of the differential localization of neuropeptide Y (NPY) in sympathetic neurons supplying different arterial segments in the cutaneous circulation of the guinea-pig ear. Responses of the main ear artery to exogenous NPY and norepinephrine (NE) were examined in vitro by measuring isometric tension. Responses of smaller arterial vessels to application of exogenous NPY or NE to the adventitial surface were examined in anaesthetized, ventilated guinea-pigs, by measuring changes in internal vessel diameter using video microscopy. Some arterial segments subsequently were examined for the presence of immunoreactivity (IR) to tyrosine hydroxylase (TH) and NPY. NPY (1 nM-10 microM) contracted the main ear artery (EC50 = 10 nM; max. contraction = 30% KCl), and 1 nM NPY produced slight potentiation of contractions produced by NE. In vivo, local applications of NPY (1-10 microM) constricted only a subpopulation of arterial vessels (23 of 41). All vessels constricted by NPY were innervated by axons containing IR to both TH and NPY, and as a population, were more proximal in the arterial tree (branch orders 3 to 6) than were vessels insensitive to NPY (branch orders 4 to 8). Most vessels insensitive to NPY were arterioles and arterio-venous anastomoses < 40 microns in diameter, which were innervated by axons containing TH-IR but not NPY-IR. In contrast, local application of NE (1-30 microM) constricted all vessels examined in vivo. When present, NPY constrictions had a longer latency (15-45 s) and duration (3-4 min) than NE constrictions of the same vessel segments. In vivo, NPY sometimes potentiated the peak amplitude of NE constrictions (2 of 7 vessels), but only in vessels where NPY also produced direct constriction. These results reveal an excellent correlation between the localization of NPY in sympathetic axons, and the location of postsynaptic NPY receptors throughout the cutaneous arterial system. Any NPY released in response to strong activation of cutaneous sympathetic neurons is likely to act preferentially on the proximal cutaneous arteries, and to lead to a more prolonged constriction of these arteries than of more distal arterioles and arterio-venous anastomoses.

Peptide-immunoreactive neurons and nerve fibres in lumbosacral sympathetic ganglia: selective elimination of a pathway-specific expression of immunoreactivities following sciatic nerve resection in kittens

The distributions of peptide-immunoreactive nerve fibres and cell bodies in lumbosacral paravertebral sympathetic ganglia of young cats were analysed with antibodies to calcitonin gene-related peptide, enkephalin, neurotensin, somatostatin, substance P, galanin, neuropeptide Y and vasoactive intestinal polypeptide. Fairly dense networks of nerve fibres showing enkephalin-, neurotensin-, somatostatin- or substance P-like immunoreactivity were observed in the ganglia. Double-staining experiments revealed that enkephalin- and somatostatin-immunoreactive nerve fibres preferentially surrounded calcitonin gene-related peptide- and/or vasoactive intestinal polypeptide-immunoreactive cell bodies. Neurotensin- and substance P-immunoreactive nerve fibres were mainly associated with neurons showing neuropeptide Y and/or galanin-like immunoreactivity. Occasional nerves containing calcitonin gene-related peptide-, galanin-, neuropeptide Y- or vasoactive intestinal polypeptide-like immunoreactivity were observed. These fibres did not seem to have any direct regional distribution within the ganglia. In kittens surviving for three months after early postnatal sciatic nerve resection, no calcitonin gene-related peptide-immunoreactive cell bodies could be detected in ganglia ipsilateral to the operation. In contrast, vasoactive intestinal polypeptide-like immunoreactivity, which partly co-exists with calcitonin gene-related peptide, was observed to the same extent as in control ganglia. Furthermore, almost all of the somatostatin-immunoreactive varicose nerve fibres had disappeared, whereas a fairly dense network of calcitonin gene-related peptide-immunoreactive nerve fibres could be observed. This change was paralleled by an increased content of nerve fibres that were immunoreactive to antibodies against the growth-associated protein GAP-43 (also known as B-50). The present findings suggest that experimental perturbations where postganglionic neurons are separated from their target areas by axotomy, not only induce differential changes in neurotransmitter expression in the principal ganglion cells, but also in preganglionic sympathetic neurons projecting to the ganglia. One possible explanation for the occurrence of an axotomy-induced network of calcitonin gene-related peptide-immunoreactive nerve fibres, is that extrinsic sensory nerve fibres grow into the ganglia after the sciatic nerve lesion. Thus, these findings seem to suggest one additional possibility with regard to the question of a possible interaction between sympathetic and sensory neurons after peripheral nerve injury.

Neuropeptides and a neuronal marker in cutaneous innervation during human foetal development

There is evidence that foetal body movements first occur at 6 weeks gestation, and that the reflex arc is functional at 8 weeks. This correlates with the detection of the sensory neuropeptides calcitonin gene-related peptide (CGRP) and substance P (SP) in spinal cord at 10 weeks gestation. However, the development of cutaneous neuropeptide-containing nerves is not well documented in humans. We have investigated the early appearance and distribution pattern of CGRP, SP, vasoactive intestinal peptide (VIP) and neuropeptide Y (NPY), as well as those of the general neuronal marker protein gene product 9.5 (PGP) in various areas of foetal skin at different gestational ages. PGP-immunoreactive nerves were first seen in the subepidermal plexus at 6 weeks gestational age. Initially, the immunoreactive nerves are thick, club-shaped and distributed in the superficial dermis. Beaded adult-like fibres become more numerous only at later ages (10-12 weeks), and extend from this plexus to penetrate the epidermis. Histologically, the skin of the hand develops faster than that of other body areas and at 9 weeks, more PGP-immunoreactive nerves were seen in the palm than in the dorsum. Primitive sweat glands were first noted in axillary skin at 17 weeks, accompanied by a few PGP-immunoreactive nerves. Occasional, small CGRP-immunoreactive fibres were first noticed in the dermis at 7 weeks, but it was at 17 weeks that the presence of this neuropeptide was unequivocal in the subepidermal plexus. Sparse VIP-, SP- and NPY-immunoreactive fibres were not found until 16-17 weeks gestation, when they were seen in the dermis and around small blood vessels.(ABSTRACT TRUNCATED AT 250 WORDS)

Brainstem peptidergic neurons projecting to the medial and lateral thalamus and zona incerta in the rat

The presence of neuropeptides in brainstem neurons that project to the medial and lateral thalamus and zona incerta has been studied in the rat. Brainstem neurons were retrogradely labeled from the medial and lateral thalamus and the zona incerta by colloidal gold-WGA-HRP and, after silver intensification of the retrograde label, their content of immunoreactivity for nine different neuropeptides was determined after colchicine administration. The medial thalamus and zona incerta both received a large peptidergic input and the lateral thalamus a smaller input from neurons in several brainstem nuclei. These were principally from the locus coeruleus, parabrachial nucleus, the dorsal raphe and the dorsal tegmentum. The principal input to the medial thalamus arose from neurotensin, neuropeptide Y and galanin neurons in the locus coeruleus, neurotensin neurons in the dorsal tegmentum, dynorphin neurons in the parabrachial nucleus and dorsal tegmentum, galanin neurons in the dorsal raphe, substance P neurons in the lateral and dorsal periaqueductal grey and calcitonin gene-related peptide neurons in the nucleus paragigantocellularis. The principal peptidergic input to the zona incerta was from dynorphin neurons in the nucleus of the solitary tract, bombesin neurons in the lateral reticular nucleus, calcitonin gene-related peptide and cholecystokinin neurons in the dorsal tegmentum, substance P, bombesin and galanin neurons in the locus coeruleus, dynorphin and substance P neurons in the lateral periaqueductal grey and cholecystokinin neurons in the substantia nigra, ventral tegmental nucleus and raphe linearis. The principal peptidergic input to the lateral thalamus came from calcitonin gene-related peptide and cholecystokinin neurons in the dorsal tegmentum, calcitonin gene-related peptide and galanin neurons in the locus coeruleus; substance P, neuropeptide Y, galanin and calcitonin gene-related peptide neurons in the dorsal raphe, substance P neurons in the lateral periaqueductal gray, galanin neurons in the nucleus interpedunculus and cholecystokinin neurons in the raphe linearis. In all these cases, from 25% to virtually all of the projection neurons in the brainstem nucleus could contain immunoreactivity to the neuropeptide. A lesser, but significant peptidergic input to the thalamus and zona incerta also arose from the trigeminal nucleus, the substantia nigra, the nucleus of the solitary tract, the lateral reticular nucleus, the interpeduncular nucleus, the raphe linearis, the paragigantocellularis, the inferior olive and ventral tegmental area. Overall, the neuropeptides most frequently present in the projection neurons were substance P, calcitonin gene-related peptide, galanin and cholecystokinin. Bombesin, neuropeptide Y, neurotensin and dynorphin were less common; and enkephalin was present in only a small percentage of projection neurons.(ABSTRACT TRUNCATED AT 400 WORDS)

Neuronal specificity and plasticity in the autonomic nervous system

The autonomic nervous system is divided into the sympathetic, parasympathetic and enteric subdivisions. The present review is focussed upon the highly specialized reflex organization and neurochemistry of sympathetic parasympathetic neurons. The currently available informations allow to conclude that autonomic control of each peripheral target tissue is specifically regulated under normal conditions but nevertheless able to respond to altered conditions by changes in neural activity and mediator expression.

The sensory and sympathetic innervation of guinea-pig lung and trachea as studied by retrograde neuronal tracing and double-labelling immunohistochemistry

The sympathetic and sensory innervation of guinea-pig trachea and lung were studied by means of retrograde neuronal tracing using fluorescent dyes, and double-labelling immunofluorescence. Sympathetic neurons supplying the lung were located in stellate ganglia and in thoracic sympathetic chain ganglia T2-T4; those supplying the trachea resided in the superior cervical and stellate ganglia. Retrogradely labelled sympathetic neurons were usually immunoreactive to tyrosine hydroxylase; the majority also contained neuropeptide Y immunoreactivity. However, a small number were non-catecholaminergic (i.e. tyrosine hydroxylase negative), but neuropeptide Y immunoreactive. Within the airways, tyrosine hydroxylase/neuropeptide Y-immunoreactive axons were found in the smooth muscle layer, around blood vessels including the pulmonary artery and vein, and to a lesser extent in the lamina propria. Periarterial axons contained in addition dynorphin immunoreactivity. Sensory neurons supplying the lung were located in jugular and nodose vagal ganglia as well as in upper thoracic dorsal root ganglia; those supplying the trachea were most frequently found bilaterally in the nodose ganglia and less frequently in the jugular ganglia. A spinal origin of tracheal sensory fibres could not be consistently demonstrated. With regard to their immunoreactivity to peptides, three types of sensory neurons projecting to the airways could be distinguished: (i) substance P/dynorphin immunoreactive; (ii) substance P immunoreactive but dynorphin negative; and (iii) negative to all peptides tested. Substance P-immunoreactive neurons innervating the airways invariably contained immunoreactivity to neurokinin A and calcitonin gene-related peptide. Retrogradely labelled neurons located in the nodose ganglia belonged almost exclusively (greater than or equal to 99%) to the peptide-negative group, whereas the three neuron types each represented about one-third of retrogradely labelled neurons in jugular and dorsal root ganglia. Within the airways, axons immunoreactive to substance P/neurokinin A and substance P/calcitonin gene-related peptide were distributed within the respiratory epithelium of trachea and large bronchi, in the lamina propria and smooth muscle from the trachea down to the smallest bronchioli (highest density at the bronchial level), in the alveolar walls, around systemic and pulmonary blood vessels, and within airway ganglia. Those axons also containing dynorphin immunoreactivity were restricted to the lamina propria and smooth muscle. The origin of nerve fibres immunoreactive for vasoactive intestinal polypeptide, of which a part were also neuropeptide Y immunoreactive, could not be determined by retrograde tracing experiments. Vasoactive intestinal polypeptide-immunoreactive fibres terminating within airway ganglia may be of preganglionic parasympathetic origin, whereas others (e.g. those found in smooth muscle) may arise from intrinsic ganglia.(ABSTRACT TRUNCATED AT 400 WORDS)

Comparison of locations and peptide content of postganglionic neurons innervating veins and arteries of the rat hindlimb

The ganglionic location of hindlimb vasoconstrictor sympathetic neurons in several species is known but the locations of neurons innervating limb arteries or veins, specifically, have not been compared and neurochemical differences between them have not been examined in detail. This study was designed to determine whether neurons innervating arteries and veins are organized as distinct populations and whether neurons innervating arteries, veins or footpads contain the same peptides. Retrograde transport of fluorescent dyes was used to identify, separately, paravertebral postganglionic neurons in the 13th thoracic to 6th lumbar (T13-L6) chain ganglia that innervate the femoral arteries, femoral veins and footpads of the rat hindlimb. The proportions of venous and arterial vasomotor neurons and footpad neurons containing neuropeptide Y- and vasoactive intestinal polypeptide-immunoreactivity (NPY-Ir, VIP-Ir) were then compared. Venous vasomotor neurons were found mostly (62%) in the L1 and L2 ganglia. The majority of arterial vasomotor neurons (81%) were distributed slightly more caudally in L1-L3. Veins and arteries were not innervated by the same cells. Footpad neurons were located mostly in L4-L6. NPY-Ir was identified in 17% of the venomotor neurons, in 94% of arterial neurons and in 24% of footpad neurons. VIP-Ir was found in 3% of the venomotor neurons, 8% of the arterial neurons and in 44% of the footpad neurons. In conclusion, hindlimb venous and arterial vasomotor neurons are anatomically distinct, are mixed randomly within the chain ganglia and differ markedly in their content of NPY, consistent with reported differences in neuromuscular transmission to arteries and veins. The most likely hindlimb postganglionic neurons to contain VIP were those innervating footpads, probably controlling sweat gland function.

Rostrocaudal differences in morphology and neurotransmitter content of cells in the subretrofacial vasomotor nucleus

The rostral ventrolateral medulla (RVLM) contains sympathoexcitatory neurons that exert a powerful control over the sympathetic outflow to the cardiovascular system. In the cat there is a concentration of such neurons (but not neurons subserving other functions) within a narrow longitudinal column in the RVLM termed the subretrofacial (SRF) nucleus. Furthermore, it has been suggested that there are subgroups of cells, located at different rostrocaudal levels of the SRF nucleus, that preferentially or exclusively control different vascular beds (e.g. in the kidney and hindlimb). The aim of this study was to map quantitatively the rostrocaudal distribution within the nucleus of different cell types, defined according to morphological and/or chemical criteria, and to correlate this with the regional vasomotor effects (in hindlimb and kidney) evoked by stimulation of SRF cells at the corresponding rostrocaudal levels. SRF cells were highly heterogeneous with respect to both their morphology and chemical properties. They varied greatly in size (equivalent diameter ranging from 10-40 microns) as well as in shape and orientation. An immunohistochemical examination using the avidin-biotin procedure revealed that many SRF cells (estimated 57% of all SRF cells) were immunoreactive for tyrosine hydroxylase (TH, a marker of catecholamine cells). In addition, there were SRF cells immunoreactive for neuropeptide Y (NPY, 11% of total), enkephalin (ENK, 16% of total), and serotonin (5HT, 10% of total), but not for substance P, galanin or somatostatin. Different cell types, defined according to their morphology and/or chemical properties, were unevenly distributed throughout the nucleus. In the most caudal part of the SRF nucleus, virtually all cells were TH-positive, and the large majority (estimated 80%) were NPY-positive, suggesting that many cells at this level contained both TH and NPY. In contrast, in the most rostral part of the SRF nucleus, only 30% of cells were TH-positive, and no NPY-positive cells were observed. Both 5HT- and ENK-positive cells were found throughout the rostrocaudal extent of the nucleus, but predominantly within its rostral part. Furthermore, TH-positive cells in the rostral SRF nucleus were on average significantly larger (mean equivalent diameter 18-43% greater) than TH/NPY-positive cells in the caudal part of the nucleus, but smaller than 5HT- or ENK-positive cells at the same level. Overall, rostral cells (regardless of their chemical type) were larger than caudal cells within the SRF nucleus (mean equivalent diameter 13-28% greater).(ABSTRACT TRUNCATED AT 400 WORDS)

Vasoconstrictor, vasodilator and pilomotor pathways in sympathetic ganglia of guinea-pigs

Triple-labelling immunofluorescence and retrograde axonal tracing with fluorescent dyes have been combined to identify and characterize the neuropeptide content of vasoconstrictor, vasodilator and pilomotor neurons in the lumbar sympathetic ganglia of guinea-pigs. Postganglionic noradrenergic pilomotor neurons lacked immunoreactivity to neuropeptide Y and comprised up to about 30% of postganglionic neurons. Most post-ganglionic noradrenergic neurons that contained neuropeptide Y immunoreactivity were likely to be vasoconstrictor neurons, although some noradrenergic neurons containing neuropeptide Y projected to pelvic viscera. Vasoconstrictor neurons comprised up to about 60% of postganglionic neurons. About 15% of postganglionic neurons were non-noradrenergic and contained immunoreactivity to vasoactive intestinal peptide, neuropeptide Y and dynorphin. They mostly innervated blood vessels supplying skeletal muscles and were likely to be vasodilator neurons. Endings of presumed preganglionic neurons containing immunoreactivity to substance P were exclusively associated with vasodilator neurons. Conversely, presumed preganglionic endings containing immunoreactivity to calcitonin gene-related peptide were exclusively associated with vasoconstrictor neurons, although not all vasoconstrictor neurons had such endings associated with them. Presumed preganglionic terminals containing immunoreactivity to enkephalin were associated with some postganglionic neurons in each functional class. These results show that preganglionic and postganglionic sympathetic neurons lying in different functional pathways can be distinguished by their neuropeptide content as well as their projections. The identification of neurochemically distinct functional pathways begins to explain how the sympathetic nervous system is organized to allow the precise control of discrete target tissues.

Galanin is more common than NPY in vascular sympathetic neurons of the brush-tailed possum

The distribution of galanin (Gal) in sympathetic vascular neurons of adult and juvenile brush-tailed possums (Trichosurus vulpecula), was examined using double-labelling immunohistochemistry. This was compared with the distribution of neuropeptide Y (NPY) in the same tissues. Immunoreactivity (IR) to galanin was present in the majority (64-99%) of nerve cell bodies in paravertebral sympathetic ganglia, where it mostly co-existed with IR to the catecholamine-synthesizing enzyme, tyrosine hydroxylase (TH). Gal-IR also was present in most, if not all, TH-IR perivascular axons supplying systemic arteries and veins. NPY-IR was less common than Gal-IR in all sympathetic ganglia and perivascular axons examined. Some sympathetic, TH-IR axons supplying the abdominal aorta and renal artery contained both Gal-IR and NPY-IR, while TH-IR axons supplying cephalic and thoracic vessels contained Gal-IR but not NPY-IR. Limited observations on sympathetic neurons in two species of wallabies indicated that Gal-IR also was more common than NPY-IR in other marsupial species, but the incidence of NPY-IR was higher in these wallabies than in the brush-tailed possum. Together with previous studies, this work suggests that the coexistence of galanin and NPY may be the primitive condition for sympathetic neurons in tetrapods. The differential expression of these peptides in specific populations of sympathetic neurons may have important functional consequences in the autonomic control of the circulation.

Receptor binding sites for cholecystokinin, galanin, somatostatin, substance P and vasoactive intestinal polypeptide in sympathetic ganglia

Sympathetic ganglia are innervated by neuropeptide-containing fibers originating from pre- and postganglionic sympathetic neurons, dorsal root ganglion neurons, and in some cases, myenteric neurons. In the present report receptor autoradiography was used to determine whether sympathetic ganglia express receptor binding sites for several of these neuropeptides including bombesin, calcitonin gene-related peptide-alpha, cholecystokinin, galanin, neurokinin A, somatostatin, substance P, and vasoactive intestinal polypeptide. The sympathetic ganglia examined included the rat and rabbit superior cervical ganglia and the rabbit superior mesenteric ganglion. High levels of receptor binding sites for cholecystokinin, galanin, somatostatin, substance P, and vasoactive intestinal polypeptide were observed in all sympathetic ganglia examined, although only discrete neuronal populations within each ganglion appeared to express receptor binding sites for any particular neuropeptide. These data suggest that discrete populations of postganglionic sympathetic neurons may be regulated by neuropeptides released from pre- and postganglionic sympathetic neurons, dorsal root ganglion neurons, and myenteric neurons.

Classification of preganglionic neurones projecting into the cat cervical sympathetic trunk

1. The spontaneous and reflex activity patterns of 167 single preganglionic axons dissected from the cervical sympathetic trunk were examined in chloralose-anaesthetized cats. Each neurone was classified into one of four major groups, on the basis of three principal criteria: the presence or absence of significant cardiac rhythmicity of the activity, the response to noxious stimulation of the skin, and the coupling of its activity to central inspiratory drive (phrenic nerve activity). Most neurones were also subjected to additional tests, which included carotid chemoreceptor stimulation, nasopharyngeal probing, systemic hypercapnia (ventilation with 8% CO2), hyperventilation, adrenaline-induced blood pressure rises and retinal illumination. 2. Group I neurones (n = 69; 41%) showed significant cardiac rhythmicity, indicating strong baroreceptor control. Most (54/69) were excited by noxious stimuli, the rest being unaffected. Their activity showed variable degrees of excitatory coupling to the central inspiratory drive, and was enhanced by hypercapnia (35/39). Their responses to stimulation of arterial chemoreceptors (12/15) and nasopharyngeal receptors (24/35) were excitatory. 3. Group II neurones (n = 39; 23%) were inhibited by noxious stimulation of skin. With nine exceptions, they showed no significant cardiac rhythmicity, although they were weakly inhibited by an adrenaline-induced blood pressure rise. Their coupling to central inspiratory drive was weak or absent, and their responses to hypercapnia and hyperventilation were variable. By contrast to other groups, they were inhibited by both chemoreceptor stimulation (9/10) and nasopharyngeal stimulation (17/18). 4. Group III neurones (n = 33; 20%) showed no significant cardiac rhythmicity, but their activity was closely coupled to central inspiratory drive. They were inhibited by hyperventilation (9/9) and excited by hypercapnia (20/21), but only fired during the central inspiratory phase and sometimes during late expiration. Their responses to noxious stimulation (28/33), chemoreceptor stimulation (8/11) and nasopharyngeal probing (24/24) were excitatory, but the induced activity was 'gated' by the respiratory cycle, occurring primarily during inspiration and avoiding the postinspiratory phase. 5. Group IV neurones (n = 26; 16%) showed no significant cardiac or respiratory related activity and were either excited (n = 22) or unaffected (n = 4) by noxious stimuli. One of the latter and three group II neurones were inhibited by retinal illumination; thirty-one other neurones of all classes were unaffected. 6. Approximately 45% of thoracic sympathetic neurones were silent under the experimental conditions. About 25% of these could be recruited by systemic hypercapnia leaving 34% without spontaneous and reflex activity.(ABSTRACT TRUNCATED AT 400 WORDS)

The time course of the development of the sympathetic innervation of the vasculature of the rat tail

The development of the sympathetic innervation of the tail vasculature in the rat has been examined using catecholamine fluorescence and immunohistochemical techniques to demonstrate tyrosine hydroxylase (TH) and neuropeptide Y (NPY). The tail was found to be largely devoid of noradrenergic terminals at birth. At the earliest ages, axons within nerve trunks and paravascular axon bundles showed high levels of catecholamine fluorescence, but this virtually disappeared as the innervation of the effectors was achieved. The perivascular plexus on the caudal artery was established over the first six postnatal weeks along a rostrocaudal gradient which was retained in the adult, i.e. proximal regions were more densely innervated than distal ones. The innervation of the rest of the vasculature developed relatively late during this period, with the exception of the arteriovenous anastomoses present in the distal half of the tail. These became innervated about 10 days earlier than the adjacent caudal artery at the same levels, and received a much denser innervation in the adult. At all developmental stages, distributions of TH- and NPY-immunoreactive nerve fibres were identical to those seen with catecholamine fluorescence. The sequence of development suggests that the different vascular targets are innervated by subsets of sympathetic neurons having the same neurochemistry but developing independently.

Image analysis quantification of peptide-immunoreactive nerves in the skin of patients with Raynaud's phenomenon and systemic sclerosis

Image analysis quantification was used to assess the results of immunocytochemistry for a neuronal marker and neuropeptides in digital skin biopsies from Raynaud's phenomenon (RP) and systemic sclerosis (SS) patients, to verify the possibility of a selective quantitative abnormality of immunoreactive nerves. The field area of specific immunostaining and nerve counts were evaluated on coded specimens, and the data compared by statistical analysis. Nerves immunoreactive for protein gene product 9.5 (PGP), a marker for neuronal elements, were decreased significantly in epidermal and subepidermal layers of digital skin in RP patients (P less than 0.0001). This change was paralleled by a decrease of calcitonin gene-related peptide (CGRP) immunoreactive nerves in the epidermis and around capillaries in the dermal papillae (P = 0.005). In the skin of RP patients, these changes were readily demonstrated by image analysis, although they were not always apparent on visual screening. In digital skin of SS patients, there was a generalized and very significant decrease of PGP, CGRP, and VIP immunoreactivities in all areas (P less than 0.0001). These results demonstrate that neuropeptide-containing nerves are involved in the digital pathology of RP and SS, and that image analysis quantification is an accurate and sensitive method for assessing morphological changes in pathological samples.

Vasomotor, pilomotor and secretomotor neurons distinguished by size and neuropeptide content in superior cervical ganglia of mice

Populations of postganglionic sympathetic neurons projecting to cranial targets from the superior cervical ganglia of mice were identified by retrograde axonal tracing with Fast blue combined with double-labelling immunofluorescence to detect immunoreactivity to tyrosine hydroxylase and neuropeptide Y. Nearly all neurons in the ganglion contained tyrosine hydroxylase immunoreactivity, but only about 50% of them also contained immunoreactivity to neuropeptide Y. The maximum diameter of cells with immunoreactivity to neuropeptide Y was significantly smaller than that of cells without it. Terminal axons containing immunoreactivity to both neuropeptide Y and tyrosine hydroxylase occurred around blood vessels supplying most cranial tissues, including the skin. Axons with immunoreactivity to tyrosine hydroxylase but not to neuropeptide Y innervated the piloerector muscles and the acini of the salivary glands. After injection of Fast blue into the skin or the submandibular salivary gland, populations of vasomotor, pilomotor and secretomotor neurons could be distinguished by soma size and by neuropeptide Y immunoreactivity. Neurons projecting to the salivary glands were the largest (mean diameter: 32 microns) and lacked immunoreactivity to neuropeptide Y; neurons projecting to cutaneous blood vessels were the smallest (mean diameter: 19 microns) and contained immunoreactivity to neuropeptide Y; neurons projecting to piloerector muscles were intermediate in size (mean diameter: 23 microns) and lacked neuropeptide Y immunoreactivity. A cluster analysis procedure confirmed that soma size and peptide content together identify major functional populations of neurons in the superior cervical ganglia of mice.

Distribution of Met-enkephalyl-Arg-Gly-Leu in rat larynx: partial coexistence with vasoactive intestinal polypeptide, peptide histidine isoleucine and neuropeptide Y

Using light microscopic (LM) enzyme-immunohistochemistry on deparaffinized adjacent sections Met-enkephalyl-Arg-Gly-Leu (ME-RGL) immunoreactivity was found to partially coexist with immunoreactive neuropeptide Y (NPY), vasoactive intestinal polypeptide (VIP) and peptide histidine isoleucine (PHI) in intrinsic laryngeal neurons of the rat. Further ME-RGL-immunoreactive (ir) fibres were found around glands in the subepithelium, in connective tissue of striated muscle and in the perichondrium, as well as around arterial and venous blood vessels. They frequently contacted mast cells and macrophages. The presence of ME-RGL indicates pro-enkephalin-related origin of this novel laryngeal opioid system. From the specific target relations and close interrelations of fibres staining for opioids with those staining for the other peptides--which are known to be more or less characteristic of the sympathetic (NPY), parasympathetic (VIP, PHI) and sensory (calcitonin gene-related peptide; CGRP) subdivisions of the peripheral nervous system--we deduce that opioid/non-opioid interactions might co-control various laryngeal functions, e.g. glandular secretion, blood flow, immune and inflammatory responses and/or might be of relevance in trophic mechanisms.