Nitrergic and peptidergic innervation in the developing rat heart

The phenotypic expression and anatomic distribution of nitrergic and peptidergic innervation in the developing rat heart was localized by reduced nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) histochemistry and immunohistochemistry using antibodies against neuronal isoform of nitric oxide synthase (nNOS), neuropeptide Y (NPY) and calcitonin-gene-related peptide (CGRP). NPY-immunoreactive nerve fibers showed the earliest expression by 16 days of gestation, with preferential innervation of the nodal and perinodal areas, followed by the innervation of the valves and ventricles by postnatal day 7. NPY immunoreactivity was also localized to a large proportion of the intrinsic cardiac ganglia from 16 days of gestation onwards with a progressive increase in the number of neuronal cell bodies per ganglia with age. CGRP-positive nerve fibers appeared by 19 days of gestation and were less dense during the gestational and early postnatal periods, and showed a quantitative increase in density by 7 days, followed by a decrease by 3 weeks postnatal. None of the intrinsic ganglia were stained positive for CGRP, indicating the extrinsic sensory origin of these stained fibers. Nitrergic innervation paralleled the sensory innervation, with the cardiac ganglia and nerve fibers showing a positive labeling from 19 days of gestation onwards. NADPH-d and nNOS were partially co-localized. Double-label immunohistochemistry showed that a considerable proportion of sensory CGRP-immunopositive fibers were also immunoreactive for NOS. The results of the present study show that neuropeptides and nitric oxide are expressed by the late gestational period and that autonomic efferent innervation precedes sensory and nitrergic innervation in the developing heart. Accepted: 4 January 2000     

Nervous control of photophores in luminescent fishes

Functional studies of the autonomic innervation in the photophores of luminescent fishes are scarce. The majority of studies have involved either the stimulation of isolated photophores or the modulatory effects of adrenaline-induced light emission. The fish skin is a highly complex organ that performs a wide variety of physiological processes and receives extensive nervous innervations. The latter includes autonomic nerve fibers of spinal sympathetic origin having a secretomotor function. More recent evidence indicates that neuropeptide-containing nerve fibers, such as those that express tachykinin and its NK1 receptor, neuropeptide Y, or nitric oxide, may also play an important role in the nervous control of photophores. There is no anatomical evidence that shows that nNOS positive (nitrergic) neurons form a population distinct from the secretomotor neurons with perikarya in the sympathetic ganglia. The distribution and function of the nitrergic nerves in the luminous cells, however, is less clear. It is likely that the chemical properties of the sympathetic postganglionic neurons in the ganglia of luminescent fishes are target-specific, such as observed in mammals.     

Immunolocalization of neurotransmitter-synthesizing enzymes and neuropeptides with associated receptors in the photophores of the hatchetfish, Argyropelecus hemigymnus Cocco, 1829

Anatomical and functional studies of the autonomic innervation of the photophores of luminescent fishes are scarce. The present immunohistochemical study demonstrated the presence of nerve fibers in the luminous epithelium and lens epithelium of the photophores of the hatchet fish, Argyropelecus hemigymnus and identified the immunoreactive elements of this innervation. Phenylethanolanine N-methyltransferase (PNMT) and catecholamine (CA)-synthesizing enzymes were detected in nerve varicosities inside the two epithelia. Neuropeptides were localized in neuropeptide Y (NPY) and substance P (SP)- and its NK11 receptor-immunopositive nerves in the lens epithelium. Neuropeptides were also localized in non-neural cell types such as the lens cells, which displayed immunoreactivities for pituitary adenylate cyclase activating peptide (PACAP) and their receptors R-12 and 93093-3. This reflects the ability of the neuropeptide-containing nerves and lens cells to turn on and off the expression of selected messengers. It appears that the neuropeptide-containing nerves demonstrated in this study may be sensory. Furthermore, neuronal nitric oxide synthase-immunopositive axons associated with photocytes in the luminous epithelium have previously been described in this species. Whereas it is clear that the photophores receive efferent (motor) fibers of spinal sympathetic origin, the origin of the neuropeptide sensory innervation remains to be determined. The functional roles of the above neuropeptides or their effects on the bioluminescence or the chemical nature of the terminals, either sensory or postganglionic neurons innervating the photophores, are still not known.     

Neuropeptide Y mRNA regulation in rat sympathetic ganglia: effect of reserpine.

To study the mechanism underlying trans-synaptic neuropeptide regulation, mRNA levels of neuropeptide Y were examined in the rat stellate and superior cervical ganglia using a specific neuropeptide Y cRNA probe. Basal levels of neuropeptide Y mRNA were detectable in total RNA extracts from single ganglia. Reserpine induced a large rise in ganglion neuropeptide Y mRNA. Decentralization prevented the increase of neuropeptide Y mRNA content in the ganglia. This suggests that the reserpine induced increase in neuropeptide Y mRNA was dependent on transsynaptic stimulation. Consequently, neuropeptide mRNA levels in sympathetic ganglia may be under the control of preganglionic impulse flow.     

Transient expression of neuropeptide Y and its C-flanking peptide immunoreactivities in the spinal cord and ganglia of human embryos and fetuses.

An immunohistochemical study of spinal cord, dorsal root and sympathetic ganglia of human embryos and fetuses demonstrated that neuropeptide Y and its C-flanking peptide could be detected in seven-week-old embryos but were absent or difficult to demonstrate after the 17th week of gestation. The peptides were found in several structures of the spinal cord, e.g. fibres in the dorsal portion of the lateral funiculus, cell bodies and fibres in the dorsal horn, and motoneurons, and also in numerous primary sensory neurons of dorsal root ganglia. They were also present in sympathetic neurons and since these are the only structures expressing neuropeptide Y and its C-flanking peptide in the adult, it must be concluded that their presence in other neurons is a transient developmental feature. To assist in understanding the relationship of these transient structures with other spinal and sensory neurons, a comparison was made with other neuronal structures showing immunoreactivity for two general neuronal markers, neurofilaments and protein gene product 9.5, and two neuropeptides present in primary sensory afferents, somatostatin and substance P. In the dorsal root ganglia, numerous neuropeptide Y- and C-flanking peptide-immunoreactive neurons were observed before substance P- or somatostatin-immunoreactive cells could be detected. Therefore, neuropeptide Y and its C-flanking peptide could represent a primitive peptidergic system appearing before primary sensory neurons express their characteristic adult phenotype. The fibres of the lateral funiculus showing immunoreactivity for neuropeptide Y and its C-flanking peptide were longitudinally orientated and could be detected at all cephalocaudal levels of the spinal cord. Comparison with the other immunohistochemical markers indicated that they were not primary sensory afferents. At least some of them probably originated from neuropeptide Y- and C-flanking peptide-immunoreactive neurons of the dorsal horn, that may be considered to be a subset of early-appearing interneurons.     

Contribution of the cervical sympathetic ganglia to the innervation of the pharyngeal arch arteries and the heart in the chick embryo

In the chick heart, sympathetic innervation is derived from the sympathetic neural crest (trunk neural crest arising from somite level 10–20). Since the trunk neural crest gives rise to sympathetic ganglia of their corresponding level, it suggests that the sympathetic neural crest develops into cervical ganglia 4–14. We therefore tested the hypothesis that, in addition to the first thoracic ganglia, the cervical ganglia might contribute to cardiac innervation as well. Putative sympathetic nerve connections between the cervical ganglia and the heart were demonstrated using the differentiation markers tyrosine hydroxylase and HNK‐1. In addition, heterospecific transplantation (quail to chick) of the cardiac and trunk neural crest was used to study the relation between the sympathetic neural crest and the cervical ganglia. Quail cells were visualized using the quail nuclear antibody QCPN. The results by immunohistochemical study show that the superior and the middle cervical ganglia and possibly the carotid paraganglia contribute to the carotid nerve. This nerve subsequently joins the nodose ganglion of the vagal nerve via which it contributes to nerve fibers in cardiac vagal branches entering the arterial and venous pole of the heart. In addition, the carotid nerve contributes to nerve fibers connected to putative baro‐ and chemoreceptors in and near the wall of pharyngeal arch arteries suggesting a role of the superior and middle cervical ganglia and the paraganglia of the carotid plexus in sensory afferent innervation. The lower cervical ganglia 13 and 14 contribute predominantly to nerve branches entering the venous pole via the anterior cardinal veins. We did not observe a thoracic contribution. Heterospecific transplantation shows that the cervical ganglia 4–14 as well as the carotid paraganglia are derived from the sympathetic neural crest. The cardiac neural crest does not contribute to the neurons of the cervical ganglia. We conclude that the cervical ganglia contribute to cardiac innervation which explains the contribution of the sympathetic neural crest to the innervation of the chick heart. Anat Rec 255:407–419, 1999. © 1999 Wiley‐Liss, Inc.     

Contribution of the cervical sympathetic ganglia to the innervation of the pharyngeal arch arteries and the heart in the chick embryo.

In the chick heart, sympathetic innervation is derived from the sympathetic neural crest (trunk neural crest arising from somite level 10-20). Since the trunk neural crest gives rise to sympathetic ganglia of their corresponding level, it suggests that the sympathetic neural crest develops into cervical ganglia 4-14. We therefore tested the hypothesis that, in addition to the first thoracic ganglia, the cervical ganglia might contribute to cardiac innervation as well. Putative sympathetic nerve connections between the cervical ganglia and the heart were demonstrated using the differentiation markers tyrosine hydroxylase and HNK-1. In addition, heterospecific transplantation (quail to chick) of the cardiac and trunk neural crest was used to study the relation between the sympathetic neural crest and the cervical ganglia. Quail cells were visualized using the quail nuclear antibody QCPN. The results by immunohistochemical study show that the superior and the middle cervical ganglia and possibly the carotid paraganglia contribute to the carotid nerve. This nerve subsequently joins the nodose ganglion of the vagal nerve via which it contributes to nerve fibers in cardiac vagal branches entering the arterial and venous pole of the heart. In addition, the carotid nerve contributes to nerve fibers connected to putative baro- and chemoreceptors in and near the wall of pharyngeal arch arteries suggesting a role of the superior and middle cervical ganglia and the paraganglia of the carotid plexus in sensory afferent innervation. The lower cervical ganglia 13 and 14 contribute predominantly to nerve branches entering the venous pole via the anterior cardinal veins. We did not observe a thoracic contribution. Heterospecific transplantation shows that the cervical ganglia 4-14 as well as the carotid paraganglia are derived from the sympathetic neural crest. The cardiac neural crest does not contribute to the neurons of the cervical ganglia. We conclude that the cervical ganglia contribute to cardiac innervation which explains the contribution of the sympathetic neural crest to the innervation of the chick heart.     

Nerve injury increases an excitatory action of neuropeptide Y and Y2-agonists on dorsal root ganglion neurons

Damage to sensory nerves invokes the expression of neuropeptide Y in the cell bodies of sensory neurons in dorsal root ganglia. We therefore compared the action of this peptide on control dorsal root ganglia neurons with its action on neurons from animals in which the sciatic nerve had been cut. Neuropeptide Y (0.1-1.0 microM) increased the excitability of 24% of control neurons and its effect was stronger and more cells (56%) were affected after axotomy. Increased excitability was mediated via a Y2-receptor and resulted from attenuation of Ca2+-sensitive K+-conductance(s) secondary to suppression of N-type Ca2+ channel current. Y1-agonists potentiated L-type Ca2+ channel current in control neurons without altering excitability. This Y1-effect was attenuated whereas effects mediated via Y2-receptors were enhanced after axotomy. No evidence was found for involvement of Y4- or Y5-receptor subtypes in the actions of neuropeptide Y either on control or on axotomized dorsal root ganglion neurons. It is concluded that neuropeptide Y increases the excitability of sensory neurons by interacting with a Y2-receptor and thereby decreasing N-type Ca2+ channel current and Ca2+-sensitive K+-conductance(s). When peripheral nerves are damaged, dorsal root ganglion neurons start to express neuropeptide Y and its excitatory Y2-excitatory effects are enhanced. The peptide may therefore contribute to the generation of aberrant sensory activity and perhaps to the etiology of injury-induced neuropathic pain.     

Presynaptic inhibition of cardiac vagal postganglionic nerves by neuropeptide Y

Stimulation of cardiac sympathetic nerves evokes prolonged non-adrenergic, non-cholinergic attenuation of the action of the vagus nerve on heart rate-an effect mimicked by, and proposed to be due to neuropeptide Y (NPY), a peptide released from sympathetic nerve terminals. In anaesthetised dogs, the effects on heart rate of the cholinomimetic bethanechol were unaltered by sympathetic stimulation or administration of NPY sufficient to cause prolonged inhibition of cardiac vagal action. In isolated guinea pig atria, during effective ganglion blockade, the effects on heart rate of the cholinomimetic methacholine were unaltered by exogenous NPY which inhibited cardiac slowing induced by stimulation of vagal nerve terminals. It is suggested that NPY released from sympathetic nerves inhibits cardiac vagal effectiveness by an action on postganglionic nerve terminals.     

Tyrosine hydroxylase and neuropeptide Y are increased in ciliary ganglia of sympathectomized rats.

We have examined the expression of tyrosine hydroxylase and neuropeptide Y in ciliary ganglia of normal adult rats and of adult rats in which the environment of these neurons was altered by sympathectomy at birth. Following neonatal 6-hydroxydopamine treatment, the proportion of tyrosine hydroxylase-immunoreactive and neuropeptide Y-immunoreactive neurons in ciliary ganglia was significantly increased. In ciliary neurons of both control and sympathectomized rats, neuropeptide Y immunoreactivity was preferentially co-localized with tyrosine hydroxylase. Immunoblot analysis confirmed the presence of tyrosine hydroxylase and its increase following sympathectomy. In situ hybridization studies revealed that many ciliary neurons contain mRNA for tyrosine hydroxylase and for neuropeptide Y. Like tyrosine hydroxylase immunoreactivity, the number of ciliary neurons containing tyrosine hydroxylase mRNA and the amount of mRNA per cell were increased in 6-hydroxydopamine-treated rats. In contrast, neuropeptide Y mRNA levels were the same in control and 6-hydroxydopamine-treated rats. Nerve growth factor is a candidate for mediating the effects of sympathectomy and most ciliary neurons in control and sympathectomized rats expressed immunoreactivity for the low-affinity nerve growth factor receptor. In addition, ciliary neurons from 6-hydroxydopamine-treated animals possessed increased nerve growth factor receptor immunoreactivity. These studies indicate that both tyrosine hydroxylase and neuropeptide Y in the ciliary ganglion are regulated by alterations in their environment. Their expression was enhanced by chemical sympathectomy which does not affect ciliary neurons directly but, rather, removes sympathetic innervation of shared targets, including the iris. In situ hybridization analysis suggests that the increased tyrosine hydroxylase and neuropeptide Y levels result from different mechanisms and provides evidence that neuropeptide levels can be regulated without changes in mRNA levels.     

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 β-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.     

Neuropeptide Y co-exists with vasoactive intestinal polypeptide and acetylcholine in parasympathetic cerebrovascular nerves originating in the sphenopalatine, otic, and internal carotid ganglia of the rat

Neuropeptide Y co-exists with noradrenaline in the majority of the sympathetic nerves supplying cerebral blood vessels. However, after sympathectomy in the rat the number of cerebrovascular neuropeptide Y nerve fibers are only reduced in number despite a complete disappearance of the adrenergic markers. The origin of these non-sympathetic neuropeptide Y fibers was studied by nerve transections and retrograde axonal tracing utilizing True Blue. Three days after bilateral superior cervical sympathectomy, the number of neuropeptide Y-containing nerve fibers decreased to about 40% of that in non-treated animals. One week after True Blue application on the proximal portion of the middle cerebral artery, the tracer accumulated in neurons of the sphenopalatine, otic, and internal carotid ganglia. Of these cells 80%, 95% and 5%, respectively, were neuropeptide Y-positive. Some of the True Blue/neuropeptide Y-positive cells displayed immunoreactivity for vasoactive intestinal polypeptide and some were positive for choline acetyltransferase. Two weeks after bilateral removal of the sphenopalatine ganglion or transection of postganglionic fibers from the ganglion reaching the pial vessels through the ethmoidal foramen, together with subsequent sympathectomy, no neuropeptide Y-containing nerve fibers could be observed on the anterior cerebral and internal ethmoidal artery or the distal portion of the middle cerebral artery, whereas a few nerve fibers remained on the proximal portion of the middle cerebral artery, internal carotid artery, and the rostral portion of the basilar artery. In conclusion, neuropeptide Y in cerebrovascular nerves is co-stored not only with noradrenaline in sympathetic nerves from the superior cervical ganglion, but also with acetylcholine (reflected in the presence of choline acetyltransferase) and vasoactive intestinal polypeptide in parasympathetic nerves originating in the sphenopalatine, otic, and internal carotid ganglia.     

Calbindin immunoreactivity in sensory and autonomic ganglia in the guinea pig

Immunoreactivity (IR) for the calcium binding protein, calbindin, was localized in sensory ganglia (nodose, trigeminal and dorsal root), in parasympathetic ganglia (otic and sphenopalatine) in sympathetic chain ganglia and in sympathetic pre-vertebral ganglia of guinea pig. In sensory ganglia, fine nerve fibres with calbindin-IR surrounded the majority of cell bodies, a low proportion of which were themselves reactive. In cranial parasympathetic and in sympathetic chain ganglia, a small proportion of nerve cells was surrounded with baskets of calbindin-IR nerve fibres, but very few cell bodies were reactive. In prevertebral sympathetic ganglia, dense networks of terminals surrounded many cell bodies, but few somata were themselves reactive. In the coeliac and inferior mesenteric ganglia, the calbindin-IR nerve fibres surrounded somatostatin-IR cell bodies, but not those with neuropeptide Y-IR. It is concluded that specific subgroups of peripheral autonomic and sensory neurones have calbindin-IR.     

Distributions of neuropeptide Y, vasoactive intestinal peptide and somatostatin in populations of postganglionic neurons innervating the rat kidney, spleen and intestine.

Some peripheral peptidergic nerves selectively innervate different types of tissue in abdominal organs. Neuropeptide Y- and vasoactive intestinal peptide-immunoreactive nerve terminals have been identified in the kidney, spleen and intestine and these peptides may have important physiological actions. Somatostatin has been found in sympathetic ganglia, and nerve terminals containing this peptide have been identified in the intestine. We have used fluorescent retrograde tracers to identify renal, splenic and mesenteric postganglionic neurons in rat sympathetic ganglia and then used immunocytochemistry to determine the proportions of these three identified groups of neurons displaying immunoreactivity for neuropeptide Y, vasoactive intestinal peptide and somatostatin. Most renal, splenic and mesenteric neurons were immunoreactive for neuropeptide Y and less than 1% of cells innervating these organs were immunoreactive for vasoactive intestinal peptide. Somatostatin immunoreactivity was present only in a small percentage of mesenteric neurons and not in renal or splenic neurons. The present study demonstrates that (i) the rat kidney, spleen and intestine do not differ in the proportion of innervation by neuropeptide Y-immunoreactive neurons, (ii) the solar plexus, splanchnic ganglion and chain ganglia (T12 and T13) provide very little vasoactive intestinal peptide-immunoreactive inputs to these organs, and (iii) somatostatin-immunoreactive neurons innervate the intestine but not the kidney or spleen.     

Topography and time course of changes in spinal neuropeptide Y immunoreactivity after spared nerve injury

We used a new computer-assisted method to precisely localize and efficiently quantify increases in neuropeptide Y immunoreactivity (NPY-ir) along the mediolateral axis of the L4 dorsal horn (DH) following transection of either the tibial and common peroneal nerves (thus sparing the sural branch, spared nerve injury (SNI)), the tibial nerve, or the common peroneal and sural nerves. Two weeks after SNI, NPY-ir increased within the tibial and peroneal innervation territories; however, NPY-ir in the central-lateral region (innervated by the spared sural nerve) was indistinguishable from that of sham. Conversely, transection of the sural and common peroneal nerves induced an increase in NPY-ir in the central-lateral region, while leaving the medial region (innervated by the tibial nerve) unaffected. All nerve injuries increased NPY-ir in dorsal root ganglia (DRG) and nucleus gracilis (NG). By 24 weeks, both NPY-ir upregulation in the DH and hyper-responsivity to cold and noxious mechanical stimuli had resolved. Conversely, NPY-ir in DRG and NG, and hypersensitivity to non-noxious static mechanical stimuli, did not resolve within 24 weeks. Over this time course, the average cross-sectional area of NPY-immunoreactive DRG neurons increased by 151 μm². We conclude that the upregulation of NPY after SNI is restricted to medial zones of the DH, and therefore cannot act directly upon synapses within the more lateral (sural) zones to control sural nerve hypersensitivity. Instead, we suggest that NPY in the medial DH tonically inhibits hypersensitivity by interrupting mechanisms of central sensitization and integration of sensory signals at the spinal and supraspinal levels.     

Multiple neuropeptides in nerves supplying mammalian lymph nodes: messenger candidates for sensory and autonomic neuroimmunomodulation?

By the use of light microscopic (LM) immunohistochemistry, the presence of peptides and of dopamine beta-hydroxylase (DBH) in nerves supplying mammalian (guinea pig, rat, cat, pig, mouse, human) lymph nodes were examined. In all species, lymph nodes of various somatic and visceral regions were found to contain nerve fibers which stained for neuropeptide Y (NPY), vasoactive intestinal polypeptide (VIP), peptide histidine isoleucine (PHI), substance P (SP), calcitonin gene-related peptide (CGRP) or DBH. SP- and CGRP-immunoreactive (ir) fibers completely overlapped and exhibited the widest distribution. They were present in perivascular, paravascular and many non-vascular fibers travelling in close contact with lymphoid cells. In contrast, NPY-ir fibers coincided with those staining for DBH, prevailed in perivascular plexus and only rarely branched off into lymphoid parenchyma. Alternate staining of adjacent sections revealed that SP/CGRP-ir fibers were different from NPY/DBH-ir fibers. The distribution of VIP-ir fibers was identical to that of PHI-ir fibers and partially overlapped with that of ir-NPY/DBH or ir-SP/CGRP fibers. We conclude that the NPY innervation of lymph nodes is sympathetic noradrenergic while nerves coding for co-existing SP and CGRP are most likely of sensory origin. The nerves containing co-existing VIP and PHI may be of heterogenous origin (sensory, cholinergic sympathetic, and/or parasympathetic). We suggest that these distinct sensory and autonomic peptidergic pathways linking the nervous system with the lymph nodes may play a differential role in bidirectional neuroimmunomodulation.     

Neuropeptide Y in non-sympathetic nerves of the rat: changes during maturation but not after guanethidine sympathectomy

Non-sympathetic neuropeptide Y-containing nerves were demonstrated by their persistence after destruction of sympathetic nerve terminals by acute 6-hydroxydopamine treatment for 48 h. In order to examine whether these neuropeptide Y-containing nerves reinnervate tissues following the loss of sympathetic nerves we administered guanethidine sulphate to one-week-old rat pups for three weeks to produce a complete and long-lasting sympathectomy and we monitored the innervation of the superior cervical ganglion, mesenteric vein, vas deferens and urinary bladder by noradrenaline- and neuropeptide Y-containing nerves two and 16 weeks later (assay and histochemical observations). By two weeks the reduction in neuropeptide Y content of tissues was similar to the reduction after acute sympathectomy with 6-hydroxydopamine treatment, indicating that there was no early reinnervation by non-sympathetic neuropeptide Y-containing nerve fibres at a time when sensory transmitters increase. Furthermore, there was no reinnervation by neuropeptide Y-containing nerve fibres by the time these sympathectomized animals had reached maturity, 16 weeks after cessation of treatment. Neuropeptide Y levels increased in the superior cervical ganglion with normal maturation but decreased in the prostatic end of the vas deferens. A non-sympathetic source of neuropeptide Y demonstrated in the immature rat vas deferens was no longer evident in the mature animal.     

Comparison of the inhibitory roles of neuropeptide Y and galanin on cardiac vagal action in the dog.

Prolonged attenuation of cardiac vagal action occurs following cardiac sympathetic nerve stimulation or intravenous neuropeptide Y (NPY) injections in anaesthetised dogs. Equimolar intravenous injections of galanin (GAL) had no effect on cardiac vagal action in this species. Immunohistochemical analysis of dog stellate ganglia and cardiac muscle showed that most nerve cell bodies showing tyrosine hydroxylase immunoreactivity (TH-IR) also showed immunoreactivity to both NPY and GAL. The results are consistent with the proposal that NPY released from cardiac sympathetic nerves is responsible for the prolonged inhibition of cardiac vagal action known to be caused by such stimulation. A role for GAL, shown here to exist in cardiac sympathetic nerves in the dog, has yet to be determined.     

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

Developmental patterns of neuropeptide (NPY) and tyrosine hydroxylase (TH)-immunoreactivities (IR) were investigated using the method of indirect immunohistochemistry in the stellate and thoracic sympathetic ganglia of human neonates ranging in gestational age from 24 to 27 weeks (premature group) and from 38 to 41 weeks (mature group). In the paravertebral ganglia of premature neonates a small (up to 7%) population of NPY-IR nerve cells was revealed. With the gestational age increase (a mature group), a marked elevation of the number of NPY-IR ganglionic neurons (up to 41%) was noted. In contrast, in the sympathetic ganglia of premature neonates almost all the neurons were tyrosine hydroxylase immunoreactive and any change in pattern during maturation was insignificant.

The results demonstrate an age-related increase of neuropeptide Y-immunoreactivity in human paravertebral ganglia during maturation, and suggest that peptidergic co-transmission arises later in development than do the classical autonomic messengers. Adaptability of the fetus to a new external environment at birth demands a qualitatively new activity level of the autonomic nervous system, and this is provided side by side with the classical messengers noradrenaline and acetylcholine by the cotransmitter and modulating role of the neuropeptides. The appearance of neuropeptide Y in the principal sympathetic ganglionic neurons defines not only a qualitatively new level in the functional regulation of target organs at birth, but serves as an index of neonatal maturity.     

Prolonged exposure to microgravity modifies limb endpoint kinematics during the swing phase of human walking

Our recent data revealed adrenergic sensitivity in chronically compressed dorsal root ganglion (DRG) of rats. As neuropeptide Y (NPY) is a common sympathetic co-transmitter, we investigated the effect of NPY on injured DRG neurons. The expression of NPY Y1 and Y2 receptors and the effect of NPY on chronically compressed DRG neurons were studied using in situ hybridization and extracellular single fiber recording in vitro, respectively. After DRG compression, the expression of Y1 receptor was distinctly increased in large and medium-sized DRG neurons, while Y2 receptor was increased in small DRG neurons. NPY inhibited both the spontaneous activity and the excitatory effect of norepinephrine in injured DRG A-neurons. The results suggest a possibility that NPY may inhibit the hyperexcitability of injured DRG A-neurons via increased Y1 receptor following chronic compression.