Long-term chemical sympathectomy leads to an increase of neuropeptide Y immunoreactivity in cerebrovascular nerves and iris of the developing rat

Efficacy and influencing factors of cervical perivascular sympathectomy in children with cerebral palsy

BACKGROUND

There is a lack of research to determine the efficacy of cervical perivascular sympathectomy (CPVS) in children with cerebral palsy (CP).

OBJECTIVE

This study aimed to evaluate the efficacy of CPVS in children with CP and analyze the associated influential factors.

METHODS

Using the method of retrospective cohort studies, children who underwent CPVS were included in the CPVS group, whereas those who underwent selective posterior rhizotomy (SPR) were included in the SPR group. The Communication Function Classification System (CFCS) and Teacher Drooling Scale (TDS) were used to evaluate the communication function and salivation in the two groups before and 12 months after surgery and compare the surgical efficiency between the two groups, and the factors affecting the efficacy were screened by binary logistic regression.

RESULTS

The study included 406 patients, 202 in the CPVS group and 204 in the SPR group. No significant differences were observed in the baseline characteristics (p > 0.05). The surgical efficacy of the CPVS group (47.01%) was significantly higher than that in the SPR group (9.81%) (χ2 = 71.08, p < 0.001). Binary logic regression analysis showed that preterm birth and Gross Motor Function Classification System (GMFCS) grade were influencing factors of surgical efficacy. Eighteen patients developed postoperative complications.

CONCLUSION

CPVS is a safe and effective surgery for cerebral palsy. Preterm birth and GMFCS grade are independent factors affecting the efficacy of surgery.

Autonomic control of the eye

The autonomic nervous system influences numerous ocular functions. It does this by way of parasympathetic innervation from postganglionic fibers that originate from neurons in the ciliary and pterygopalatine ganglia, and by way of sympathetic innervation from postganglionic fibers that originate from neurons in the superior cervical ganglion. Ciliary ganglion neurons project to the ciliary body and the sphincter pupillae muscle of the iris to control ocular accommodation and pupil constriction, respectively. Superior cervical ganglion neurons project to the dilator pupillae muscle of the iris to control pupil dilation. Ocular blood flow is controlled both via direct autonomic influences on the vasculature of the optic nerve, choroid, ciliary body, and iris, as well as via indirect influences on retinal blood flow. In mammals, this vasculature is innervated by vasodilatory fibers from the pterygopalatine ganglion, and by vasoconstrictive fibers from the superior cervical ganglion. Intraocular pressure is regulated primarily through the balance of aqueous humor formation and outflow. Autonomic regulation of ciliary body blood vessels and the ciliary epithelium is an important determinant of aqueous humor formation; autonomic regulation of the trabecular meshwork and episcleral blood vessels is an important determinant of aqueous humor outflow. These tissues are all innervated by fibers from the pterygopalatine and superior cervical ganglia. In addition to these classical autonomic pathways, trigeminal sensory fibers exert local, intrinsic influences on many of these regions of the eye, as well as on some neurons within the ciliary and pterygopalatine ganglia.

Cotransmission in the autonomic nervous system

After some early hints, cotransmission was proposed in 1976 and then "chemical coding" later established for sympathetic nerves (noradrenaline/norepinephrine, adenosine 5'-triphosphate (ATP), and neuropeptide Y), parasympathetic nerves (acetylcholine, ATP, and vasoactive intestinal polypeptide (VIP)), enteric nonadrenergic, noncholinergic inhibitory nerves (ATP, nitric oxide, and VIP), and sensory-motor nerves (calcitonin gene-related peptide, substance P, and ATP). ATP is a primitive signaling molecule that has been retained as a cotransmitter in most, if not all, nerve types in both the peripheral and central nervous systems. Neuropeptides coreleased with small molecule neurotransmitters in autonomic nerves do not usually act as cotransmitters but rather as prejunctional neuromodulators or trophic factors. Autonomic cotransmission offers subtle, local variation in physiological control mechanisms, rather than the dominance of inflexible central control mechanisms envisaged earlier. The variety of information imparted by a single neuron then greatly increases the sophistication and complexity of local control mechanisms. Cotransmitter composition shows considerable plasticity in development and aging, in pathophysiological conditions and following trauma or surgery. For example, ATP appears to become a more prominent cotransmitter in inflammatory and stress conditions.

Dynamic cerebral autoregulation in stroke patients with a central sympathetic deficit

OBJECTIVE

To investigate the functional role of the sympathetic innervation on cerebral autoregulation.

MATERIALS AND METHODS

Seventeen patients with infarction of the dorsolateral medulla oblongata affecting central sympathetic pathways (Wallenberg's syndrome) and 21 healthy controls were included in the study. Cerebral blood flow velocity (CBFV) in the medial cerebral artery was investigated using transcranial Doppler ultrasound during decrease in cerebral perfusion pressure induced by leg-cuff test and tilt table.

RESULTS

Upon leg-cuff test, changes of cerebral blood flow and mean arterial blood pressure as well as autoregulatory index did not differ between patients or controls. No differences were found in changes of CBFV, mean arterial blood pressure and heart rate between patients or controls during the tilt table test.

CONCLUSIONS

We suggest that the sympathetic nervous system does not have an influence on cerebral autoregulation after decrease in perfusion pressure under normotonous conditions.

Neural endothelin in hypertension: increased expression in ganglia and nerves to cerebral arteries of the spontaneously hypertensive rat

Endothelin has previously been localised in perivascular nerves of the rat basilar artery. Considering its potent vasoconstrictor and mitogenic properties on vascular smooth muscle, the potential role of a neural source of this peptide in hypertension has been investigated. The trigeminal, superior cervical and sphenopalatine ganglia of Wistar Kyoto (WKY) rats and spontaneously hypertensive rats (SHR) at 16 weeks of age have been examined for immunolocalisation of endothelin at the light and electron microscope level. At the light microscope level, neurones immunopositive for endothelin were detected in these ganglia of the SHR but were not seen in ganglia from WKY rats. This difference was particularly marked in the trigeminal ganglia where endothelin-positive neurones colocalised with substance P immunoreactivity. Using in situ hybridisation techniques, endothelin-1 mRNA was localised to the cytoplasm of neurones in the ganglia and was more prominent in the SHR. At the electron microscope level, endothelin-immunoreactivity was localised at the peripheral perikarya of some neuronal cell bodies of the trigeminal, superior cervical and sphenopalatine ganglia of WKY rats but was more prominent with heavy labelling throughout the cytoplasm of neurones in the SHR. Notably, in the trigeminal ganglia of the SHR only, some endothelin-immunopositive nerve fibres appeared to be damaged and contained vacuoles with granular material. Ultrastructural examination of the basilar artery revealed an increased number of endothelin-positive axons in the SHR, but these axons usually showed selective damage. In summary, in the SHR, there was a marked increase in endothelin particularly in sensory neurones projecting to the basilar artery which also appear to be undergoing degenerative changes. An increased neural source of endothelin in the SHR may contribute to the development of hypertension or may be a consequence of selective degenerative change.

Parasympathetic varicosity proliferation and synaptogenesis in rat eyelid smooth muscle after sympathectomy

Parasympathetic innervation to eyelid smooth muscle inhibits sympathetic neurotransmission pre-junctionally without appreciable direct post-junctional effects. However, 5 weeks after sympathectomy, parasympathetic stimulation elicits substantial cholinergically mediated contractions. This study examined ultrastructural changes accompanying the conversion to parasympathetic excitation. In intact muscles, 64+/-9 nerve varicosities were encountered per 104 micron2. Most were close to muscle cells and not fully enclosed by supporting cells. Axo-axonal synapses were observed occasionally. Two days following sympathectomy, varicosity numbers were reduced by 97% and, relative to controls, remaining varicosities were farther from muscle cells and more frequently fully enclosed by supporting cells, but contained greater numbers of small spherical and large dense vesicles. By 6 weeks post-sympathectomy, numbers of varicosities per unit muscle volume increased to 14% of controls. These varicosities differed from those at 2 days in being closer to smooth muscle cells, less frequently enclosed, and having fewer small vesicles. These findings indicate that intact eyelid smooth muscle varicosities are predominantly sympathetic, but a small number of parasympathetic varicosities are present, some of which may form pre-junctional synapses with sympathetic nerves. Between 2 days and 6 weeks post-sympathectomy, varicosities increased in number and established appositions with smooth muscle cells. This suggests that parasympathetic nerves are capable of re-innervating an atypical smooth muscle target after sympathectomy, and that parasympathetic synaptogenesis is likely to contribute to conversion from pre-junctional inhibition to post-junctional excitation after sympathectomy.

Plasticity in adult and ageing sympathetic neurons

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

Plasticity in the myenteric plexus of the rat ileum after long-term sympathectomy

To investigate the effect of chronic sympathectomy on the innervation of a tissue with an extensive intrinsic component, 1-week-old rat pups were treated with 50 mg/kg guanethidine for 3 weeks, a treatment shown to produce complete and long-lasting sympathectomy, and the ileum examined. Changes in the levels of noradrenaline, neuropeptide Y, calcitonin gene-related peptide, substance P and vasoactive intestinal polypeptide in the external muscle layers containing the myenteric plexus of the ileum were determined between 6 and 20 weeks of age. After sympathectomy, noradrenaline levels were initially depleted (3% of age-matched controls at 6 weeks, P < 0.001, and 18% of age-matched controls at 12 weeks, P < 0.001), but were not significantly reduced at 20 weeks (67% of age-matched controls). Such increases in noradrenaline content with time after sympathectomy did not occur in the mesenteric vein (levels in 20-week-old sympathectomized rats were 2% of the control values (P < 0.001). In the myenteric plexus, catecholamine fluorescent nerve fibers were seen in the 12-week-old sympathectomized rats, although tyrosine hydroxylase-immunoreactivity was absent. Guanethidine sympathectomy had no effect on the neuropeptide levels in 6-week-old rat ileum but there was a selective increase at 20 weeks; the levels of calcitonin gene-related peptide and substance P were increased (X3, P < 0.001 and X1.6, P < 0.05, respectively) while vasoactive intestinal polypeptide and neuropeptide Y levels were unchanged. Short-term sympathectomy (destruction of sympathetic nerve terminals by acute 6-hydroxydopamine treatment) had no affect on noradrenaline or peptide levels in this tissue.(ABSTRACT TRUNCATED AT 250 WORDS)

Contractility of urinary bladder and vas deferens after sensory denervation by capsaicin treatment of newborn rats

1. Capsaicin, a selective sensory neurotoxin, was given to newborn rats and at the age of 3 months the contractile activity of the urinary bladder detrusor muscle and vas deferens evoked by either electrical field stimulation (EFS) or exogenous adenosine 5'-triphosphate (ATP) and carbachol (urinary bladder), or ATP and noradrenaline (vas deferens) were tested. 2. EFS of the urinary bladder evoked contractions which consisted of cholinergic and purinergic components, since they could be partially blocked by either the muscarinic cholinoceptor antagonist, atropine (0.3 microM) or by desensitization of P2x-purinoceptors with alpha,beta-methylene ATP (10 microM). In capsaicin-treated rats, contractions of the urinary bladder evoked by EFS were significantly larger than those of control (vehicle-treated) animals, and this difference remained after the purinergic component of the contractions was blocked by desensitization of P2x-purinoceptors with alpha,beta-methylene ATP. However, when the cholinergic component of the contractions was blocked with atropine, the difference between the groups at 8 Hz and 16 Hz was abolished; EFS caused significantly larger contractions of the capsaicin-treated rat bladder only at frequencies of 2 Hz and 4 Hz. 3. EFS evoked contractions of the vas deferens consisted of adrenergic and purinergic components since they could be partially blocked by either the alpha-adrenoceptor antagonist, phentolamine (3 microM) or by alpha,beta-methylene ATP (10 microM). The contractions of the vas deferens were significantly larger than in the capsaicin-treated rats only at a frequency of 16 Hz. There were no differences between vas deferens contractions of the two groups either after desensitization of P2X-purinoceptors by alpha,beta-methylene ATP or in the presence of phentolamine.4. Contractions of the capsaicin-treated rat urinary bladder evoked by exogenous carbachol (0.1-100 microM) were not significantly different from those of controls, the pD2 values being 1.78 +/- 0.23 micro M and 1.90 +/- 0.20 micro M respectively. There was also no significant difference between the groups in contractions of the bladder evoked by ATP (10 micro M-3 mM).5. Contractions of the vas deferens evoked by either ATP (10 micro M-3 mM) or noradrenaline (1-1000 micro M) in the capsaicin-treated group showed no significant difference between control and capsaicin treated rats.6. In conclusion, the present results indicate that chronic capsaicin treatment increases the amplitude of contractions of the rat urinary bladder, an effect which preferentially involves the cholinergic component of the response; since the response to carbachol is unaffected, the change involves prejunctional mechanisms. In contrast, both the purinergic and adrenergic components of contraction in the vas deferens are unaffected by capsaicin. It is suggested that sensory nerves have a trophic influence on the development of parasympathetic nerves in the rat bladder; removal of sensory nerves shortly after birth results in an increase mainly in the cholinergic, and to a lesser extent purinergic component.

Innervation of cerebral arteries by nerves containing 5-hydroxytryptamine and noradrenaline

Noradrenaline (NA)-containing nerves, mainly originating in the sympathetic superior cervical ganglia, supply large and small cerebral arteries. In large cerebral arteries, nerves containing serotonin (5-hydroxytryptamine, 5-HT) may represent neuronal uptake of circulating 5-HT by sympathetic nerves. 5-HT-containing nerves supplying small pial vessels probably have a central origin in the dorsal raphe nucleus. In most species, NA is a weak vasoconstrictor (alpha 1- or alpha 2-adrenoceptors), while 5-HT is a potent vasoconstrictor (5-HT2 or 5-HT1-like receptors) of large cerebral arteries. In contrast, both NA and 5-HT tend to cause vasodilatation in small pial vessels and arterioles. Adrenergic and serotonergic transmission can be modulated by pH, a range of putative neurotransmitters and neuromodulators, and by the endothelium. Sumatriptan, a 5-HT1-like receptor agonist, has been shown to be effective in the treatment of migraine. Changes in NA- or 5-HT-containing nerves and/or in the responses of cerebral vessels to NA and 5-HT have been observed in a variety of vascular disorders, including cerebral vasospasm following subarachnoid haemorrhage, hypertension, and atherosclerosis.

Adrenergic and nitrergic neurotransmitters are released by the autonomic system of the pig long posterior ciliary artery

The role played by adrenergic, muscarinic and nitric oxide putative neurotransmitters released from autonomic nerve endings onto the pig proximal long posterior ciliary artery (LPCA) was determined. The proximal LPCA in the pig usually supplies both the uveal and retinal circulations. In this study, in vitro ring segments of the artery, passively stretched and with noradrenaline-induced tone, were neurogenically stimulated (NS) using electrical field stimulation with 5-sec trains of 0.2 msec pulses. NS produced a frequency dependent contraction in all vessels which was completely abolished by 10(-6) M tetrodotoxin. 40 Hz stimulation was used throughout the study as it produced a maximal NS contraction. 10(-5) M guanethidine abolished the NS-induced contraction and revealed a NS-induced relaxation, as did the alpha adrenergic blocker, phentolamine, in vessels passively stretched. The beta adrenergic blocker, propranolol, only slightly reduced the NS-induced constriction. In vessels pre-contracted with noradrenaline, NS produced a relaxation (D) which was proportional in magnitude to the tone (C) viz. D = (0.30 +/- 0.04).C + (0.24 +/- 0.06). The muscarinic blocker, atropine, had no effect on the NS-induced relaxation, implying that it is a non-adrenergic, non-cholinergic mediated system. Incubation with Nw-nitro-L-arginine methyl ester reduced the NS-induced relaxation to 48% of its control value, a reduction which was reversed in the presence of excess L-arginine. Damage to endothelial cell function did not reduce the NS-induced relaxation. It is concluded that the autonomic innervation of the proximal LPCA releases both contraction and relaxation neurotransmitters. Contraction is mediated by an alpha adrenergic neurotransmitter. At least two neurotransmitters mediate relaxation, one of which is probably nitric oxide. There is no functional evidence for the release of beta adrenergic neurotransmitter from the sympathetic system or acetylcholine from the parasympathetic system.

Nature and origin of cerebrovascular nerves with substance P immunoreactivity in bats (Mammalia: Microchiroptera), with special reference to species differences

Double staining immunohistochemistry was used to investigate the origin and projection of nerves with substance P (SP) immunoreactivity (-IR) in the walls of the major cerebral arteries in two microchiropteran species. In the greater horseshoe bat, most of the cerebral perivascular nerves with SP-IR did not exhibit calcitonin gene-related peptide (CGRP)-IR, but emitted bright immunofluorescence for vasoactive intestinal polypeptide (VIP). In this species, a large number of cell bodies with both SP- and VIP-IR were observed in many cranial ganglia along various branches of the facial and glossopharyngeal nerves. There were no cell bodies immunoreactive for either SP and VIP in the two sensory (trigeminal and upper cervical dorsal root), two sympathetic (superior cervical and stellate), or two vagal (superior and jugular) ganglia. In addition, several thick fiber bundles with both SP- and VIP-IR were present in the wall of the cerebral carotid artery, and descended progressively reaching as far as the middle part of the basilar artery (BA). These and other findings suggest that SP-immunoreactive nerves with VIP-IR but not CGRP-IR, which contribute to the rich innervation of the vertebrobasilar system in the greater horseshoe bat, originate from neurons with the same combination of peptide-IR in the major or local facial or glossopharyngeal parasympathetic ganglia, and enter the cranial cavity along the internal carotid artery. In the bent-winged bat, however, cerebral perivascular SP-immunoreactive nerves, as well as SP-immunoreactive neurons within the trigeminal and upper cervical dorsal root ganglia (uCDRG), showed neither CGRP-IR nor VIP-IR, and were mostly confined to the caudal BA and the vertebral artery (VA). These observations, in addition to the projection of this nerve type to the BA via the VA as fiber bundles, or through the meninges, indicate that the principal source of the cerebrovascular SP-immunoreactive innervation in this species is the uCDRG.

Pseudo-cerebrospinal fluid rhinorrhea

Because of its potentially serious sequelae, cerebrospinal fluid (CSF) leakage following surgery for lesions of the cranial base is given immediate attention by neurosurgeons. Despite a multitude of approaches used to prevent its occurrence, CSF leakage complicates up to 30% of difficult skull-base tumor operations. The authors describe the cases of 11 patients who developed a syndrome, not previously described in the literature, termed "pseudo-CSF rhinorrhea." This syndrome occurs after surgery of the cranial base, usually involving dissection or removal of the petrous or cavernous carotid artery, the greater superficial petrosal nerve, and the pericarotid sympathetic plexus. It is characterized by nasal stuffiness and nasal hypersecretion and is sometimes accompanied by facial flushing. The symptoms are characteristically exacerbated by exertion or by elevated ambient room temperatures. Lacrimation is typically absent ipsilateral to the pseudo-CSF rhinorrhea. It is believed that pseudo-CSF rhinorrhea developed in these patients because of a relative imbalance of the regulatory autonomic supply of the nasal mucosa.

Conversion of parasympathetic nerve function from prejunctional inhibition to postjunctional excitation following sympathectomy of rat periorbital smooth muscle

Parasympathetic innervation of rat periorbital smooth muscle normally inhibits excitatory sympathetic neurotransmission but does not directly affect muscle tone. Five weeks after sympathetic denervation, however, parasympathetic stimulation now elicits contractions. These are blocked by atropine, indicating establishment of muscarinic cholinergic neuromuscular transmission. Conversion to excitation is not accompanied by enhanced smooth muscle responsiveness to muscarinic stimulation, indicating that prejunctional alterations are responsible.

Ageing in the autonomic nervous system: a result of nerve-target interactions? A review

There are few generalisations that can be made regarding the changes that occur in autonomic nerves during ageing. Old age has different effects, including loss of neurones, loss of axon branches and alterations in neurotransmitters and other intracellular features. However, these age-related events are associated with particular and often small groups of neurones and are frequently species specific. Changes occur at different periods during development and maturity without any obvious age-stage at which neurodegenerative changes come to predominate. Some of the observations regarding neuronal changes in old age can be interpreted as the result of altered interactions between neurones and their peripheral target tissues. Recent studies in my laboratory support this contention. The neurotrophic theory has been used to explain such interactions during early development and it seems possible that, for example, alterations in the access of neurones to target-derived growth factors may underlie some of the changes that have been observed in old age. Plasticity in the mature autonomic nervous system may also be governed by similar relationships between nerves and their target tissues.

Plasticity of the sympathetic nervous system innervating the cerebral arteries in rats

In order to investigate the neuroplasticity of the peripheral sympathetic nervous system innervating the cerebral blood vessels, we observed and traced the sprouting nerve fibers originating in the contralateral superior cervical ganglion (SCG) into the previously denervated cerebral arteries following unilateral excision of the SCG and/or decentralization of the contralateral SCG in young rats (4 weeks old). These nerve fibers were labeled anterogradely with wheat germ agglutinin-horseradish peroxidase or stained immunohistochemically with anti-tyrosine hydroxylase antibody. Eight weeks after the right SCG excision, reinnervating nerve fibers originating in the contralateral ganglion formed a circular pattern of nerve plexus only on the wall of the main cerebral arteries of the circle of Willis in the ganglionectomized side. However, the decentralization of the contralateral SCG, which was performed simultaneously with a unilateral SCG excision, prevented the nerve sprouting into the denervated regions. Unilateral decentralization of SCG itself failed to affect their distribution pattern or their density of nerve fibers originating in the ganglion. It is concluded that in the young rat the outgrowth of the sympathetic nerve fibers into the denervated cerebral arteries was strongly impeded by the disconnection of ganglion cells from the central nervous system, while the decentralization alone could not affect the innervation pattern of the postganglionic fibers which have been already built-up in the cerebral arterial system.

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.

Guanethidine sympathectomy of mature rats leads to increases in calcitonin gene-related peptide and vasoactive intestinal polypeptide-containing nerves

Changes in the innervation of the heart (right atrium), mesenteric blood vessels, vas deferens and superior cervical ganglia have been examined following long-term sympathectomy of the mature rat. Patterns of innervation were investigated by histochemical and immunohistochemical techniques, while levels of noradrenaline and neuropeptides were measured by neurochemical assays. Large doses of guanethidine (80 mg/kg) were given daily for four weeks to 12-14 week-old male rats which were killed at 18-20 weeks of age. Catecholamine-containing nerves were severely depleted or absent in all tissues, together with a reduction in noradrenaline content. Neuropeptide Y levels were depleted by 97% in vas deferens, 78% in mesenteric vein and 50% in right atrium and superior cervical ganglion. Increases in levels of calcitonin gene-related peptide were seen in the mesenteric vein (up seven-fold), superior cervical ganglia (up 11-fold) and vas deferens (prostatic portion up three-fold), which were also evident by assessment of immunolabelling of nerve fibres. Calcitonin gene-related peptide levels were not increased in the right atrium. In addition, an increase in vasoactive intestinal polypeptide-immunoreactive nerve fibre density was seen in the mesenteric artery and vas deferens, although no significant differences were observed in assays of vasoactive intestinal peptide levels in any tissue. No changes were seen in the innervation of any of the tissues by substance P-immunoreactive nerve fibres either by immunohistochemical or immunochemical assay assessment. This study indicates that there are selective changes in the mature nervous system in response to the loss of sympathetic nerves. Differences between these changes and the response of the developing nervous system to long-term sympathectomy are discussed.

Peptidergic and serotoninergic innervation of the rat dura mater

The peptidergic and serotoninergic innervation of the rat dura mater was investigated by reacting dural wholemounts immunohistochemically with antibodies to calcitonin gene-related peptide (CGRP), substance P (SP), neuropeptide Y (NPY), vasoactive intestinal polypeptide (VIP), and serotonin (5-HT). CGRP and SP innervations of the dura were robust and the patterns of distribution of these neuropeptides were essentially the same. The majority of the fibers were perivascular and distributed to branches of the anterior and middle meningeal arteries and to the superior sagittal and transverse sinuses. Other CGRP/SP fibers appeared to end "free" within the dural connective tissue. NPY-immunoreactive fibers were extremely numerous and also distributed heavily to the branches of the meningeal arteries, the venous sinuses, and to the dural connective tissue. The pattern of NPY innervation resembled in many ways that of CGRP/SP; however, NPY innervation of the sinuses was greater and NPY perivascular fibers supplying the meningeal arteries formed more intimate contacts with the walls of the vessels. The pattern of VIP innervation was, in general, similar to that observed for the three previous neuropeptides; however, the overall density was considerably less. Small to moderate numbers of serotoninergic nerve fibers were observed in some, but not all, of the duras processed for 5-HT. The latter fibers were almost exclusively perivascular in distribution. Dural mast cells were prominently stained in the 5-HT preparations because of their serotonin content. Mast cells were also labeled in a nonspecific fashion in some of the tissues reacted immunohistochemically for neuropeptides; some of them were located in close apposition to passing nerve fibers. This study represents, to our knowledge, the first comprehensive work on the peptidergic and serotoninergic innervation of the mammalian dura mater. The results should increase our understanding of the roles that these fibers play in normal dural physiology and of their potential interactions in the pathogenesis of vascular headache.

Increases in NPY in non-sympathetic nerve fibres supplying rat mesenteric vessels after immunosympathectomy

The effect of nerve growth factor (NGF) deprivation on developing peripheral peptide-containing nerves has been examined in Wistar rats. Animals were treated from birth for 7 days with antibodies to NGF (10 microliters/g body weight) and killed at 4 or 8 weeks of age. The nerves of the mesenteric and femoral blood vessels, vas deferns and bladder were viewed with histochemical and immunohistochemical techniques. The effectiveness of anti-NGF treatment was monitored by viewing catecholamine (CA)-containing nerves, which were virtually absent from the blood vessels, but were little affected in the vas deferens and bladder in both age groups. Immunoreactivity for substance P and calcitonin gene-related peptide was slightly reduced in the blood vessels. Immunoreactivity for neuropeptide Y (NPY) was reduced in the femoral blood vessels by 88% at both ages, but reductions in NPY immunoreactivity (NPY-IR) in the mesenteric vessels varied with age. In the mesenteric artery at 4 weeks, NPY-IR was reduced by 96% from control values, but at 8 weeks it was reduced by only 37%. Acute sympathectomy with 6-OHDA treatment reduced NPY-IR in the mesenteric artery by 98% at 4 weeks and 93% at 8 weeks. It is proposed that the increase in NPY-IR but not CA-containing nerves in the mesenteric artery between 4 and 8 weeks after immunosympathectomy is due to compensatory innervation from a non-sympathetic source (probably enteric neurons) that is available to mesenteric, but not to femoral blood vessels.

Increase of dopamine beta-hydroxylase immunoreactivity in non-noradrenergic nerves of rat cerebral arteries following long-term sympathectomy

The expression of dopamine beta-hydroxylase (DBH) and tyrosine hydroxylase (TH) immunoreactivity (IR) after short-term (2 days) and long-term (3 weeks) sympathectomy was investigated in rat cerebral vessels, dura mater and pterygopalatine ganglion neurones (which are known to project to cerebral arteries) by immunohistochemistry at both the light and electron microscopical levels. TH-IR, like glyoxylic acid-induced fluorescence, was completely abolished by sympathectomy. By contrast, DBH-IR was localized in nerve fibres, lacking 5-hydroxydopamine (5-OHDA)-labelled vesicles, along cerebral vessels of long-term sympathectomized rats, but not in the dura mater, and in pterygopalatine ganglia, where the number of DBH-IR neurons increased from 27.87% to 54.11%. Since virtually all the pterygopalatine neurons displayed choline acetyltransferase (ChAT)-IR, both in control and sympathectomized rats, it is concluded that long-term sympathectomy caused an increase of the expression of DBH-IR in cholinergic neurones of the pterygopalatine ganglion, without these neurons producing or storing noradrenaline.

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.

Effects of neonatal sympathectomy with 6-hydroxydopamine or guanethidine on survival of neurons in the intermediolateral cell column of rat spinal cord

The effects of removing target cells on survival of, and inputs to, sympathetic preganglionic neurons were studied in rats that were sympathectomized with 6-hydroxydopamine (6-OHDA) or guanethidine sulfate. Separate groups of neonatal and 1-week male rats were given injections of 6-OHDA for 10 days and of guanethidine for 3 weeks (5 days/week), respectively. Histofluorescence results suggest that catecholaminergic neurons in most ganglia are destroyed with treatment except for adrenal medulla, which is unaffected [14], and the pelvic ganglion where only partial destruction occurs. Cells in the intermediolateral cell column from representative spinal cord segments of treated and control adult rats were counted. In 6-OHDA-treated rats, cells decreased in number in all segments compared to controls. In guanethidine-treated rats, cells were also decreased in number; in some segments the decrease was significantly greater than with 6-OHDA. Sympathectomy had no effect on neurons in the intermediate gray of L5 or in the ventral horn of T3. The results of this study demonstrate that peripheral sympathectomy causes loss of sympathetic preganglionic neurons and that guanethidine is slightly more effective than 6-OHDA.

Peptides and vasomotor mechanisms

The multiple and diverse roles played by neuropeptide Y, vasoactive intestinal polypeptide, substance P, calcitonin gene-related peptide and other biologically active peptides in the cardiovascular system are considered. A model of the vascular neuroeffector junction is described, which illustrates the interactions of peptidergic and nonpeptidergic transmitters that are possible at pre- and postjunctional sites. The effects of peptides on specific endothelial receptors are also described, which highlights the ability of these agents to act as dual regulators of vascular tone at both adventitial and intimal surfaces, following local release from nerves, or from endothelial cells themselves. Changes in expression of vascular neuropeptides that occur during development and aging in some disease situations and following nerve lesion are discussed.

Use of enhanced silver staining combined with electron microscopical immunolabelling to demonstrate the colocalization of neuropeptide Y and vasoactive intestinal polypeptide in cerebrovascular nerves

The combination of immunolabelling at the electron microscope level and enhanced silver staining has been used to demonstrate the colocalization of neuropeptide Y and vasoactive intestinal polypeptide in perivascular nerves supplying cerebral arteries of the rat. This has been shown in control tissue, but it is easier to demonstrate after long-term sympathectomy since that leads to an enhancement of neuropeptide Y in vasoactive intestinal polypeptide-containing parasympathetic nerves supplying these vessels. Immunolabelling of the antigens for these peptides was performed sequentially with the biotin streptavidin diaminobenzidine method, and the end product to the first antiserum was gold-silver intensified before the visualization of the second antigen. Using this technique, it was shown that all the neuropeptide Y immunoreactivity present in the rat cerebral vessels after long-term sympathectomy with guanethidine was localized in vasoactive intestinal polypeptide-containing nerves. Furthermore, an immunohistochemical analysis of the parasympathetic pterygopalatine ganglia in guanethidine-treated rats showed an increase in the percentage of neurons displaying neuropeptide Y immunoreactivity. In order to clarify if the pterygopalatine ganglion was the origin of those neuropeptide Y/vasoactive intestinal polypeptide-immunoreactive cerebrovascular nerves, which had increased in number after sympathectomy, a fluorescent neuronal tracer (Fast Blue) was applied to the right middle cerebral artery of rats which had undergone guanethidine treatment for six weeks. Immunohistochemical analysis of the ipsilateral ganglion 72 h after application of the tracer revealed the presence of immunoreactivity to both these peptides in retrogradely labelled neurons. It is concluded that neuropeptide Y and vasoactive intestinal polypeptide are colocalized in perivascular parasympathetic nerves supplying the middle cerebral artery of the rat, which have their origin in the pterygopalatine ganglion. Furthermore, long-term sympathectomy with guanethidine leads to an increase in the expression of neuropeptide Y in these vasoactive intestinal polypeptide-immunoreactive neurons.