Regional changes in structural and functional integrity of myometrial adrenergic nerves in pregnant guinea-pig,and their relationship to the localization of the conceptus

Pregnancy is accompanied by a reduction in uterine noradrenaline, and the study was undertaken to investigate associated structural and functional integrity of the sympathetic nerves in the organ. The formaldehyde-induced fluorescence of adrenergic nerves was studied in different uterine regions before and after in vitro incubation or injection with α-methyl-noradrenaline in pregnant and puerperal guinea-pig uterus at 6 time periods, from early pregnancy (about 20 days post coitum) to 3 months post partum. The changes were related to the position of the fetuses, which were often present in only one of the two uterine horns. There was a drastic loss of fluorescent adrenergic nerves in myometrial tissue from horns distended by fetuses. Attemps to restore this fluorescence by incubation or injection with α-methyl-noradrenaline were essentially ineffective. Tissues from uterine regions outside (and not distended by) fetuses (in the case of early pregnancy), from horns devoid of fetuses (in the case of unilateral pregnancy), and from the cervix also lost their noradrenaline-fluorescent nerves, but this occurred at a much later stage of pregnancy. After treatment with α-methyl-noradrenaline, a fluorescent plexus of sympathetic nerves could be restored to a considerable extent in these latter tissues. In puerperal animals the horn that had been devoid of fetuses regained its endogenous fluorescence much faster, and ihe uptake of α-methyl-noradrenaline was more efficient, than in the horn which had contained fetuses. In this latter horn clear signs of restoration of endogenous adrenergic fluorescence and a clear uptake capacity was not found until 3 months after delivery. In the tubal end of the uterus, the reduction in the number of fluorescent nerves was only insignificant, and the region thus clearly differed from the rest of the uterus. It is concluded that (1) there are clear regional differences with regard to the disappearance of the noradrenaline transmitter in the uterus, (2) this disappearance in early pregnancy is related to the position of the conceptus, and (3) the changes involve de-and regenerative phenomena as well as alterations in transmitter levels of intact neurons.     

Tyrosine hydroxylase and DOPA decarboxylase activities in the guinea-pig uterus: further evidence for functional adrenergic denervation in association with pregnancy.

The capacity for the synthesis of neuronal noradrenaline was studied during pregnancy andpost partum in the guinea-pig uterus, using animals with bilateral or unilateral pregnancies. The activities of the noradrenaline-synthesizing enzymes, tyrosine hydroxylase and in some experiments alsol-dopa decarboxylase were measured in various parts of the uterus and the adjacent paracervical region, which contains adrenergic ganglion cells contributing to the uterine adrenergic innervation. The submandibular gland was used for comparison. During advancing pregnancy the tyrosine hydroxylase activity in the fetus-containing uterine horn was progressively reduced, to reach undetectable levels at term. This change was not seen in the cervix and the submandibular gland. By analogy with previous fluorescence microscopic observations on the uterine adrenergic innervation, it is suggested that the very pronounced reduction in tyrosine hydroxylase activity in the fetus-containing uterine horn during advancing pregnancy is due to degeneration of the adrenergic terminal network. In the contralateral empty uterine horn of a unilateral pregnancy the tyrosine hydroxylase activity was decreased by about 90% at term despite evidence for a relatively intact adrenergic nerve plexus. In the post partum period the tyrosine hydroxylase activity increased very slowly in both the previously empty and fetus-containing horns. In the latter tissue, even 6 months after delivery, the activity was only 14% of that in uterine horns of virgin animals.In view of the marked regional heterogeneity in the changes, also related to the position and size of the onceptus, it is assumed that they are caused mainly by local humoral and probably also mechanical factors within the uterus.     

The ultrastructure of adrenergic neurons in sympathetic ganglia of the newborn rabbit after treatment with 6-hydroxydopamine

The effects of 6-hydroxydopamine, an analog of dopamine which produces degeneration of peripheral adrenergic nerve terminals in adult animals, on adrenergic neurons in the sympathetic ganglia of newborn rabbits were studied with the electron microscope. Animals were treated with a 50 mg/kg dose of 6-hydroxydopamine within six hours after birth and subsequently given daily doses until seven injections had been administered. The results of this study indicate that the adrenergic neurons underwent a “reaction” to 6-hydroxydopamine which was first manifested by an increase in filaments and smooth membranous structures in the cell bodies. In the axons of these neurons a similar increase in filaments and membranous elements, as well as accumulations of dark-core vesicles and mitchondria, were evident. Microtubules, although plentiful in normal cells and axons, were not conspicuous in these cells and axons. This initial reaction was later followed by degeneration of the cell bodies and axons and their eventual disappearance, leading to a reduction in cell population and size of the ganglia. It is suggested that the initial effect of 6-hydroxydopamine on adrenergic neurons (in newborn animals) may be an interference with their axoplasmic transport mechanism which leads to cell degeneration and death. This study also has shown that some of the small “granule-containing” cells in sympathetic ganglia may be sensitive to 6-hydroxydopamine, at least in newborn rabbits, as is indicated by their degeneration.     

Changes in the Amount of Adrenergic Transmitter in the Female Genital Tract-of Rabbit During Pregnancy

The noradrenaline present in the female reproductive organs – ovary, oviduct, uterus, and vagina – of the rabbit is stored in adrenergic nerves. Fluorescence microscopy revealed that these nerves are related to the vascular bed and the smooth muscle walls; besides the vascular nerves the ovary also contains adrenergic nerves unrelated to the vessels. The adrenergic innervation of the genital organs originates from sympathetic ganglia located near the effector organs, as well as from pre- and paravertebral ganglia. During the former half of pregnancy a marked increase in neuronal noradrenaline occurs in the reproductive organs, except in the ovary. In the uterus and the vagina this increase is followed by a dramatic decrease in total noradrenaline during the latter half of pregnancy; by the end of pregnancy the uterus is almost completely devoid of noradrenaline-containing sympathetic nerves. The findings are discussed in terms of an humoral influence on the adrenergic neurons supplying the female reprocluctive tract.     

Tenascin-C expression during Wallerian degeneration in C57BL/Wlds mice: possible implications for axonal regeneration

Summary Schwann cells in the distal stumps of lesioned peripheral nerves strongly express the extracellular matrix glycoprotein tenascin-C. To gain insights into the relationship between Wallerian degeneration, lesion induced tenascin-C upregulation and regrowth of axons we have investigated C57BL/Wld^s (C57BL/Ola) mice, a mutant in which Wallerian degeneration is considerably delayed. Since we found a distinct difference in the speed of Wallerian degeneration between muscle nerves and cutaneous nerves in 16-week-old C57BL/Wld^s mice, as opposed to 6-week-old animals in which Wallerian degeneration is delayed in both, we chose the older animals for closer investigation. Five days post lesion tenascin-C was upregulated in the muscle branch (quadriceps) but not in the cutaneous branch (saphenous) of the femoral nerve in 16-week-old animals. In addition myelomonocytic cells displaying endogenous peroxidase activity invaded the muscle branch readily whereas they were absent from the cutaneous branch at this time. We could further show that it is only a subpopulation of axon-Schwann cell units (mainly muscle efferents) in the muscle branch which undergo Wallerian degeneration and upregulate tenascin-C at normal speed and that the remaining axon-Schwann cell units (mainly afferents) displayed delayed Wallerian degeneration and no tenascin-C expression. Regrowing axons could only be found in the tenascin-C-positive muscle branch where they always grew in association with axon-Schwann cell units undergoing Wallerian degeneration. These observations indicate a tight relationship between Wallerian degeneration, upregulation of tenascin-C expression and regrowth of axons, suggesting an involvement of tenascin-C in peripheral nerve regeneration.     

Histochemical demonstration of a concomitant reduction in neural vasoactive intestinal polypeptide, acetylcholinesterase, and noradrenaline of cat uterus during pregnancy

Noradrenaline, acetylcholinesterase, and vasoactive intestinal polypeptide (VIP) were visualized in uterine nerves of cats by histochemical techniques. Alterations were followed in different regions of the organs at various stages of pregnancy and compared with the situation in non-pregnant controls. Positively stained nerve fibres, the adrenergic type being particularly well developed, were found along the muscle bundles and around blood vessels in the smooth muscle layers, as well as in the mucosa, of both uterine horns and cervix. The nerve supply was especially prominent in the upper part of the cervix. The distribution of VIP-immunoreactive and acetylcholinesterase-positive nerve fibres resembled each other, but they were less numerous than the adrenergic fibres. In the course of pregnancy there was a marked reduction in the number of all positively reacting nerves, so that almost no fibres were visible in the uterine horns near term. A small number of positive nerve fibres was found to remain, however, in the wall of the sterile (empty) horn during unilateral pregnancy. The reduction was less prominent in the cervix, particularly its lower part. Distinct changes were encountered already during early and mid pregnancy in those parts of the uterine wall distended by the growing conceptus, where almost no fibres were seen. The nerve supply was more intact in the non-distended portions located between the fetuses, and especially in the empty horn of unilateral pregnancy. No overt reduction in the number of positively stained nerve fibres was found in the cervix at these pregnancy stages. The results show that marked alterations take place in the uterine autonomic innervation during such an entirely physiological event as pregnancy. There is reason to assume that the histochemical observations reflect both structural and functional alterations in the innervation related both to the type of nerves involved and to the localization of the conceptus.     

Quantification of the mononuclear phagocyte response to Wallerian degeneration of the optic nerve

Summary We investigated the numbers, origin and phenotype of mononuclear phagocytes (macrophages/microglia) responding to Wallerian degeneration of the mouse optic nerve in order to compare it with the response to Wallerian degeneration in the PNS, already described. We found macrophage/microglial numbers elevated nearly four fold in the distal segments of crushed optic nerves and their projection areas in the contralateral superior colliculus 1 week after unilateral optic nerve crush. This relative increase in mononuclear phagocyte numbers compared well with the four-to five-fold increases reported in the distal segments of transected saphenous or sciatic nerves. Moreover, maximum numbers are reached at 3, 5 and 7 days in the saphenous, sciatic and optic nerves respectively, suggesting that the very slow clearance of axonal debris and myelin in CNS undergoing Wallerian degeneration is not simply due to a slow or small mononuclear phagocyte response. The apparent delay in the response in the CNS occurs because the mononuclear phagocytes respond to the Wallerian degeneration of axons, which is slightly slower in the CNS than the PNS, rather than to events associated with the crush itself, such as the abolition of normal electrical activity in the distal segment. This was demonstrated by the protracted time course of the mononuclear phagocyte response in the distal segment following optic nerve crush in mice carrying theWld ^smutation which dramatically slows the rate at which the axons undergo Wallerian degeneration. By³H-Thymidine labelling or by blocking microglial proliferation by X-irradiation of the head prior to optic nerve crush, we showed that the majority of macrophages/microglia initiating the response to Wallerian degeneration were of local, CNS origin but these cells rapidly (from 3 days post crush) upregulate endocytic and phagocytic functional markers although they do not resemble rounded myelin-phagocytosing macrophages observed in degenerating peripheral nerves. We speculate that the poor clearance of myelin in CNS fibre tracts undergoing Wallerian degeneration compared to the PNS, in the face of a mononuclear phagocyte response which is similar in relative magnitude and time course, is because Schwann cells in degenerating peripheral nerves promptly modify their myelin sheaths such that they can be recognized and phagocytosed by macrophages, whilst in the CNS oligodendrocytes do not.     

The ramifications of adrenergic nerve terminals in the rectum, anal sphincter and anal accessory muscles of the guinea-pig

Summary The anatomy and the adrenergic innervation of the rectum, internal anal sphincter and of accessory structures are described for the guinea-pig. The distribution of adrenergic nerves was examined using the fluorescence histochemical technique applied to both sections and whole mount preparations. The longitudinal and circular muscle of the rectum and the muscularis mucosae are all supplied by adrenergic nerve terminals. The density of the adrenergic innervation of the muscularis externa increases towards the anal sphincter. There is a very dense innervation of the internal anal sphincter, of the anal accessory muscles and of the corrugator ani. Non-fluorescent neurons in the ganglia of the myenteric plexus are supplied by adrenergic terminals. The ganglia become smaller and sparser towards the internal anal sphincter and non-ganglionated nerve strands containing adrenergic axons run from the plexus to the sphincter muscle. Adrenergic fibers innervate two interconnected ganglionated plexuses in the submucosa. Very few adrenergic nerve cells were found in the myenteric plexus and they were not found at all in the submucosa. The extrinsic arteries and veins of the pelvic region are heavily innervated by adrenergic nerves. Within the gut wall the arteries are densely innervated but there is little or no innervation of the veins.This work was supported by grants from the Australian Research Grants Committee and the National Health and Medical Research Council. We thank Professor G. Burnstock for his generous support.     

Degenerative and regenerative changes in central projections of glossopharyngeal and vagal sensory neurons after peripheral axotomy in cats: a structural basis for central reorganization of arterial chemoreflex pathways

Hypoxic hyperventilation in cats is a reflex normally initiated by afferent impulses originating in the carotid body and conducted to the brain stem by the carotid sinus nerves. The reflex response is abolished acutely after section of carotid sinus nerves and excision of the carotid bodies; but, chronically, there is a chemoreflex restoration which is mediated by the aortic body via the aortic depressor nerves. The restoration is associated temporally with changes in efficacy of ventilatory reflexes elicited by electrically stimulating carotid sinus and aortic depressor nerves, and these changes are postulated to reflect a central reorganization of the reflex pathways. In the present study, histological and ultrastructural techniques were used to investigate the neuroanatomical basis of the reorganization. The brain stem of the cat was examined using the Fink-Heimer silver stain to determine if degenerating axons were present following section of the carotid sinus nerve peripheral to its sensory ganglion. Degeneration was found 4-15 days postoperatively and the distribution of the axons corresponded with that reported for central projections of carotid sinus nerves labeled by transganglionic transport of horseradish peroxidase. The fine structure of nerve terminals in nucleus tractus solitarius was then examined with electron microscopy after cutting the vagus and glossopharyngeal nerves unilaterally peripheral to the sensory ganglia. Structural changes consistent with nerve terminal degeneration were observed 4-91 days postoperatively, and presumptive axonal sprouts were seen at 56-91 days.(ABSTRACT TRUNCATED AT 250 WORDS)     

Regeneration and retrograde degeneration of axons in the rat optic nerve

Summary The retinal stump of the rat optic nerve was examined histologically 1–64 weeks after intracranial section of the nerve with or without grafting of autologous peripheral nerve segments. Single unmyelinated axons and bundles of unmyelinated axons appeared in cut optic nerves and were most abundant 2–4 weeks after section. With light and electron microscope radioautography after injection of tritiated amino acids into the globe, it was confirmed that many unmyelinated fibres arose from the optic nerve rather than from nearby peripheral nerves and it was estimated that some axons regenerated as far as 0.5 mm. At or near the end of retinofugal axons, structures resembling growth cones were seen at 2 weeks and vesicle-containing swellings similar to synapses were found at 1–2 months. Outgrowth from optic nerve axons was not obviously enhanced by peripheral nerve grafts although a few retinofugal axons became ensheathed by Schwann cells. Retrograde axonal degeneration was rapid in both cut and grafted optic nerves, the number of nerve fibres near the globe falling to less than 10% of normal after 4 weeks. A few myelinated and unmyelinated fibres were still present 64 weeks after nerve transection. In conclusion, some cut axons in the rat optic nerve display a transient regenerative response before undergoing retrograde degeneration.     

Ultrastructural observations on synapse elimination in neonatal rabbit skeletal muscle

Summary Electron microscopic techniques were used to investigate two main questions about mammalian neuromuscular development. One, does neonatal synapse elimination proceed by the degeneration of synaptic terminals and preterminal axons, or are the terminals retracted into the parent axon, in a process analogous to the resorption of axonal growth cones? Two, is there any discernible relationship between the elimination of supernumerary synapses and the myelination of preterminal axons? Examination of several hundred sections through endplates fixed at the peak time of synapse elimination revealed no signs of degeneration. This result is not consistent with the proposal that the major mechanism of synapse elimination is terminal degeneration, according to calculations based on the time course of terminal degeneration following neonatal nerve transection.Serial and semi-serial reconstruction of terminals and preterminal axons suggest that myelination of intramuscular axons lags behind synapse elimination and that elimination can proceed while axons bear an immature relationship to Schwann cells. In addition, reconstruction of serial sections through neonatal synapses revealed that their three-dimensional configuration is more complex than that of mature neuromuscular synapses; this feature may be indicative of a dynamic relationship between nerve and muscle at early stages.     

Choline acetyltransferase in transected nerves, denervated muscles and Schwann cells of the frog: correlation of biochemical electron microscopical and electrophysiological observations.

The activity of choline acetyltransferase was increased in the peripheral nerve stumps of transected sciatic nerves of frogs (Rana esculenta) 5–21 days after the transection but had fallen markedly by the beginning of the second month. The increase of choline acetyltransferase activity began at a time when large myelinated fibres were still unaffected by degeneration according to both ultrastructural and electrophysiological criteria, whereas the small fibres were undergoing degeneration. It preceded the appearance of the miniature end-plate potentials attributable to the Schwann cells in the denervated sartorius muscle, which occurred 22–25 days after nerve section. The steep fall of choline acetyltransferase activity in the degenerating nerve coincided with the final stages of destruction of the large myelinated axons. One-fifth of control choline acetyltransferase activity was found in the degenerated nerve even 3 months after nerve section, when all axonal remnants were completely resorbed and the peripheral nerve stump was almost exclusively composed of proliferated Schwann cells and of the Büngner bands, formed by their processes. The activity of choline acetyltransferase in denervated sartorius muscle diminished, starting from the fifth day after nerve section. It did not fall below 60% of control level even 3 months after denervation, but it could not be excluded that in the muscle some of the synthesis of acetylcholine observed during assays of choline acetyltransferase activity was due to non-specific acetylcholine-synthesizing activity of carnitine acetyltransferase.The observations strongly suggest that choline acetyltransferase is present in the Schwann cells of degenerated frog nerves and that the enzyme is newly synthesized, rather than taken up from degenerating axons. The synthesis of choline acetyltransferase in degenerating nerves is not restricted to the Schwann cells in direct contact with the muscle fibres; apparently, it depends on the relationship between the Schwann cells and axons, and not solely (if at all) on the relationship between the Schwann cells and muscle fibres.     

The adrenergic nerve supply to the female reproductive tract of the cat

Pilot studies on the fluorescence histochemistry of the adrenergic innervation to the female reproductive tract in different mammals revealed a conspicuously well developed innervation in the cat. Moreover, the female genital tract of the cat is studied extensively with regard to the pharmacology of adrenergic mechanisms. An exact knowledge of the adrenergic innervation apparently would make the cat a particularly suitable model for functional studies on the involvement of neuronal adrenergic mechanisms in the reproductive tract. Fluorimetrically, noradrenaline was the only catecholamine occurring in measurable amounts in nonpregnant cats. The amine seemed to have an exclusively neuronal distribution, although a comparatively small fraction may be also located in “chromaffin” cells present in relation to ganglion formations. A considerable number of adrenergic nerve terminals were found in all organs of the reproductive tract. Consistent numbers of these terminals were directed to various structures forming the ovarian parenchyma and to the smooth muscle coats of the oviduct, uterus, and vagina. The rest of the innervation seemed to be of vasomotor nature. The histochemical results agree well with the high level of noradrenalin, 1.22–4.93 μg/gm, found in the different organs. Denervation experiments revealed that the postganglionic sympathetic innervation reaches the oviduct, uterus, and vagina partly by way of the hypogastric nerves, and partly by way of short adrenergic neurons originating from adrenergic ganglia that could be directly visualized in the region of the uterovaginal junction. The ovarian adrenergic innervation seemed to arise more proximally, probably directly from the sympathetic chain.     

Retrograde degeneration of myelinated axons and re-organization in the optic nerves of adult frogs (Xenopus laevis) following nerve injury or tectal ablation

Summary The optic nerve proximal to the lesion (toward the retina) was examined by light and electron microscopy in adultXenopus laevis after various types of injury to optic nerve fibres. Intraorbital resection, transection or crush of the optic nerve or ablation of the contralateral optic tectum all resulted in marked alterations in the myelinated axon population and in the overall appearance of the nerve proximal to the site of injury. Examination of the nerves from 3 days to 6 months postoperatively indicated that a progressive, retrograde degeneration of myelin and loss of large-diameter axons occurred throughout the retinal nerve stump regardless of the type of injury or distance of the injury from the retina. The retinal stump of nerves receiving resection or transection showed a nearly complete loss of myelin and large-diameter axons while the degree of degeneration was subtotal in nerves receiving crush injury or after lesions farther from the retina (i.e. tectal ablation). In addition, the entire retinal nerve stump after all types of injury was characterized by the appearance of an actively growing axon population situated circumferentially under the glia limitans. The latter fibres are believed to represent regrowing axons which are being added onto the nerve, external to the original axon population and are suspected to modify actively the glial terrain and glia limitans.     

Synaptic Connections of the Paracervical (Frankenhauser) Ganglion of the Rat Uterus Examined with the Electron Microscope after Division of the Sympathetic and Sacral Parasympathetic Nerves

The fine structure of the synapses in the paracervical (Frankenhauser) ganglion of the rat uterus was studied after sympathectomy and sacral parasympathectomy. Degenerative nerve endings to the ganglion cells were observed after division of both the sympathetic and parasympathetic nerves. No degeneration of the synapses to the chromaffin cells were seen. The results are interpreted as evidence of both sympathetic and parasympathetic innervation of the ganglion cells, which send their axons to the uterus, whereas the “chromaffin cells” are innervated by intraganglionic nerves.     

Localization and axonal transport of immunoreactive cholinergic organelles in rat motor neurons—An immunofluorescent study

Antisera produced in rabbits against pure fractions of cholinergic vesicles from Narcine brasiliensis were used to study cholinergic organelles in rat motor neurons. The indirect immunofluorescence method was used on perfusion-fixed material. The rats were surgically sympathectomized to remove sympathetic adrenergic and cholinergic nerves from the sciatic nerve. In the intact animal immunoreactive material, likely to represent cholinergic vesicles, was observed in motor endplates, identified by labelling with rhodamine-conjugated α-bungarotoxin or with subsequent acetylcholinesterase staining. The motor perikarya contained very little immunoreactive material. Non-terminal axons were virtually devoid of immunofluorescence in the intact animal. After crushing the sciatic nerve, immunoreactive material (likely to represent axonal cholinergic organelles) accumulated rapidly on both sides of the crush, indicating a rapid bidirectional transport. The transport was sensitive to local application of mitotic inhibitors.The axons which accumulated immunoreactive organelles were motor axons, as demonstrated by various procedures: (1) Cutting of ventral roots prevented accumulation of immunoreactive material in the nerve. (2) Deafferentation did not notably influence accumulations of immunoreactive material. (3) Ligated axons with immunoreactive material were acetylcholinesterase positive when identification was made on the same section; the intra-axonal distribution of immunoreactive material and acetylcholinesterase was not identical, however, and the Narcine antisera did not cross-react with bovine acetylcholinesterase in a solid phase immunoassay. (4) Most axons in ventral roots, but not in dorsal roots, accumulated strongly fluorescent immunoreactive material, while axons in dorsal roots contained weakly fluorescent material. On the other hand, substance P-like immune reactivity was present in many dorsal root axons, but only very rarely in ventral roots.It is suggested that the antisera against Narcine cholinergic vesicles can be used as a marker for cholinergic organelles in the motor neuron, and may be an important tool for studying the axonal cholinergic vesicles. It cannot, however, be used to identify cholinergic structures in unknown locations because it recognizes common antigenic determinants in transmitter organelles of other nerves e.g. adrenergic nerves. The axonal cholinergic organelles may carry important molecules, other than acetylcholine to the nerve endings.     

Early morphological changes of primary afferent neurons and their processes in newborn mice after treatment with capsaicin

Degenerating figures of dorsal root ganglion (DRG) neurons and their central and peripheral processes (dorsal root and saphenous nerve) and terminals (central terminals in the superficial dorsal horn and cutaneous nerve of the hind paw dorsal skin) of neonatal mice were examined 30 min, 1, 2 and 5 h, and 2, 3, 5, and 10 days after subcutaneous injection of capsaicin on post-natal day 2. Many small DRG neurons showed degeneration 1 h after treatment. Scarcely any features of degeneration were seen in the DRG and dorsal root 10 days after treatment. The degenerating aspects of terminal axons in the marginal layer of the superficial dorsal horn were characterized by enlarged round axons with closely packed osmiophilic materials, lamellar bodies, and loss of axoplasmic organelles. Two types of central terminals (C-terminals) showed degeneration in the substantia gelatinosa from 30 min after treatment onward. One type consisted of small, round, sinuous or slender dark terminals (CI-terminals), and the other of large, pale, round or angular terminals (CII-terminals). Those that degenerated markedly had homogeneously electron-dense axoplasm with dilated synaptic vesicles and inclusion bodies. Extensive degeneration of terminal axons in the marginal layer occurred 5 h after treatment, whereas conspicuous degeneration of C-terminals occurred from 30 min to 10 days after treatment in the substantia gelatinosa. CI-terminals showed marked degeneration during the first 3 days, whereas marked degeneration of CII-terminals occurred between 5 and 10 days after treatment. This time difference between the peaks of degeneration of CI- and CII-terminals indicates an important difference in the origins of these two types of capsaicin-sensitive, nociceptive fibers in the superficial dorsal horn; CI-terminals are derived from small DRG cells, whereas CII-terminals are derived from larger DRG cells. Unmyelinated axons in the dorsal root, saphenous nerve, and dorsal skin of the hind paw showed similar degeneration patterns 2 h after treatment to those of terminal axons in the marginal layer. Thus, the degenerating profiles in the marginal layer suggest that these axons arose from collaterals of unmyelinated primary axons descending or ascending within the marginal layer. Numerous enlarged degenerating axons showing vacuolation were conspicuous in the dorsal skin 3 days after treatment. The synchronous degeneration of the smaller DRG neurons, their central and peripheral processes, and their CI-terminals in the substantia gelatinosa supports the idea that the smaller DRG neurons are directly influenced by capsaicin, and that their degeneration is followed by centrifugal degeneration.     

Comparison of cytokine expression profile during Wallerian degeneration of myelinated and unmyelinated peripheral axons

Changes in cytokine and chemokine expression during Wallerian degeneration have been studied using nerve transection models, which result in denervation of both myelinating and non-myelinating Schwann cells. Cytokine and chemokine response of non-myelinating Remak Schwann cells to loss of their axons is unknown. In this study, we compared the expression profile of various cytokines and chemokines in distal nerves after capsaicin-induced degeneration of unmyelinated axons to Wallerian degeneration induced by nerve transection. Upregulation of MCP-1, IL-2, IL-6 and IL-10 were seen in both groups but IL-1ß and LIF were primarily upregulated in Wallerian degeneration of the whole nerve and not in capsaicin-induced degeneration of unmyelinated axons. The activated macrophage response, as measured by an increase in ED-1 immunostaining, was more prominent in the transected sciatic nerves compared to capsaicin-treated nerves. These findings indicate that there are differences in the cytokine and chemokine response of myelinating and non-myelinating Schwann cells to loss of their axons, and add to a growing body of literature that points to greater heterogeneity among Schwann cells.     

The autonomic innervation of the interstitial gland of the rat ovary during pregnancy

The autonomic innvervation of the interstitial gland of the rat ovary was studied on days 4, 6, 10, 14 and 18 of pregnancy with the acetylcholinesterase procedure, the Falck-Hillarp technique and electron microscopy after 5-hydroxydopamine treatment. Acetylcholinesterase-positive nerves were present as perivascular plexuses at all stages studied. Adrenergic nerves were present in the interstitial gland in all stages studied. The number and intensity of interstitial fluorescent adrenergic nerves increased as pregnancy progressed. Measurement of norepinephrine with the fluorometric procedure showed a highly significant (p < 0.05) increase in the neurotransmitter in the ovary on days 14 and 18 as compared to day 4. Fine-structural studies after administration of the false transmitter, 5-hydroxydopamine, showed that the innervation of the steroidogenic cells of the interstitial gland is adrenergic.     

Considerations on the Cause of Disappearance of the Adrenergic Transmitter in Uterine Nerves during Pregnancy

Sjöberg , N.-O. Considerations on the cause of disappearance of the adrenergic transmitter in uterine nerves during pregnancy. Acta physiol. scand. 1968. 72. 510–517. With a combination of fluorescence histochemical and fluorimetric techniques it has been demonstrated that the smooth muscle coats of the guinea-pig uterus have a fairly rich supply of short adrenergic neurons, i.e. neurons arising in the vicinity of the organ, emitting a green fluorescence owing to their noradrenaline content. During the last period of pregnancy the neuronal fluorescence as well as the uterine noradrenaline disappears. Using animals with unilateral pregnancy it has been possible to establish that despite a marked difference in weight and distention between the two horns there is no difference in the reaction of the adrenergic nerves during the period of pregnancy studied (32–63 days of gestation). Hence, it seems probable that the marked changes in transmitter content found during the latter part of pregnancy are due to a humoral rather than to a mechanical factor.