Ultrastructural changes in the rat superior cervical ganglion following prolonged guanethidine administration

Sympathetic modulation of tumor necrosis factor alpha-induced nociception in the presence of oral squamous cell carcinoma

ABSTRACT

Head and neck squamous cell carcinoma (HNSCC) causes more severe pain and psychological stress than other types of cancer. Despite clinical evidence linking pain, stress, and cancer progression, the underlying relationship between pain and sympathetic neurotransmission in oral cancer is unknown. We found that human HNSCC tumors and mouse tumor tissue are innervated by peripheral sympathetic and sensory nerves. Moreover, β-adrenergic 1 and 2 receptors (β-ARs) are overexpressed in human oral cancer cell lines, and norepinephrine treatment increased β-AR2 protein expression as well as cancer cell proliferation in vitro. We have recently demonstrated that inhibition of tumor necrosis factor alpha (TNFα) signaling reduces oral cancer-induced nociceptive behavior. Norepinephrine-treated cancer cell lines secrete more TNFα which, when applied to tongue-innervating trigeminal neurons, evoked a larger Ca 2+ transient; TNF-TNFR inhibitor blocked the increase in the evoked Ca 2+ transient. Using an orthotopic xenograft oral cancer model, we found that mice demonstrated significantly less orofacial cancer-induced nociceptive behavior during systemic β-adrenergic inhibitory treatment with propranolol. Furthermore, chemical sympathectomy using guanethidine led to a significant reduction in tumor size and nociceptive behavior. We infer from these results that sympathetic signaling modulates oral cancer pain through TNFα secretion and tumorigenesis. Further investigation of the role of neurocancer communication in cancer progression and pain is warranted.

Pharmacological sympathetic denervation prevents the development of polycystic ovarian syndrome in rats injected with estradiol valerate

BACKGROUND

The injection of estradiol valerate in female rats induces polycystic ovary syndrome, which is characterized by polycystic ovaries, anovulation, and hyperandrogenism. These characteristics have been associated with an increase in the ovarian concentration of norepinephrine, which occurs before establishing the polycystic ovary syndrome. The bilateral section of the superior ovarian nerve restores ovarian functions in animals with polycystic ovary syndrome. The superior ovarian nerve provides norepinephrine and vasoactive intestinal peptide to the ovary. An increase in the activity of both neurotransmitters has been associated with the development of polycystic ovary syndrome. The purpose of the present study was analyzed the participation of the noradrenergic nervous system in the development of polycystic ovary syndrome using guanethidine as a pharmacological tool that destroys peripheral noradrenergic nerve fibers.

METHODS

Fourteen-day old female rats of the CIIZ-V strain were injected with estradiol valerate or vehicle solution. Rats were randomly allotted to one of three guanethidine treatment groups for denervation: 1) guanethidine treatment at age 7 to 27-days, 2) guanethidine treatment at age 14 to 34- days, and 3) guanethidine treatment at age 70 to 90- days. All animals were sacrificed when presenting vaginal oestrus at age 90 to 94-days. The parameters analyzed were the number of ova shed by ovulating animals, the ovulation rate (i.e., the numbers of ovulating animals/the numbers of used animals), the serum concentration of progesterone, testosterone, oestradiol and the immunoreactivity for tyrosine hydroxylase enzyme. All data were analyzed statistically. A p-value of less than 0.05 was considered significant.

RESULTS

Our results show that the elimination of noradrenergic fibers before the establishment of polycystic ovary syndrome prevents two characteristics of the syndrome, blocking of ovulation and hyperandrogenism. We also found that in animals that have already developed polycystic ovary syndrome, sympathetic denervation restores ovulatory capacity, but it was not as efficient in reducing hyperandrogenism.

CONCLUSION

The results of the present study suggest that the noradrenergic fibers play a stimulant role in the establishment of polycystic ovary syndrome.

Methods of sympathetic degeneration and alteration

The role of the sympathetic nervous system in health and disease has often been elucidated by inducing changes in, or degeneration of sympathetic neural pathways. Several methods of inducing peripheral lesions have been created from surgical removal, NGF depletion, auto-immune and chemical destruction to novel approaches using immunotoxins and transgenic animals. This review compares these methods in terms of their mechanism and specificity. The advantages and disadvantages of these techniques are discussed.

Chemosensitivity, plasticity, and functional heterogeneity of paraganglionic cells in the rat coeliac-superior mesenteric complex

Chemosensitivity and plasticity of paraganglionic cells in the rat coeliac-superior mesenteric complex (CSMC) were investigated at a basal state of normoxia (21% O2) and after long-term moderate hypoxia (10% O2, 14 days). Chemical sympathectomy previous to hypoxia was performed to destroy principal ganglionic neurons and thus to allow measurement of the norepinephrine and dopamine content of paraganglionic cells. At the basal state, the CSMC contained dopaminergic (TH+/DBH-) and noradrenergic (TH+/DBH+) paraganglionic cells, the majority being of the noradrenergic type. After 14 days of hypoxia, this ratio was reversed and dopaminergic cells predominated, as indicated by a twofold increase of TH+ cells and a twofold decrease of DBH+ cells. Biochemically, hypoxia produced an increase in the content (1.6-fold) and utilization (1.4-fold) of dopamine as well as a smaller increase in the content of norepinephrine, with no change in its utilization rate. The dopaminergic activation induced by hypoxia persisted after sympathectomy with guanethidine. It is concluded that paraganglionic cells in the CSMC display a chemosensitive function. Furthermore, our findings indicate that paraganglionic cells are differentially affected by hypoxia, depending on their distribution and the nature of their neuromodulators. The alterations induced by hypoxia point out the phenotypic plasticity developed by paraganglionic cells in adaptation to hypoxia and further demonstrate the functional heterogeneity of this autonomic cell population in the rat CSMC.

Effect of immunosuppressive agents on the guanethidine-induced sympathectomy in athymic and euthymic rats

Guanethidine sulphate causes destruction of peripheral sympathetic neurons and infiltration of mononuclear inflammatory cells in the sympathetic ganglia of both athymic nude (rnu/rnu) and euthymic LEW/Mol rats. The effect of guanethidine is believed to be an autoimmune reaction. To determine the effect of immunosuppressive drugs concurrently with guanethidine treatment both athymic and euthymic rats were treated with guanethidine 40 mg/kg i.p. daily for 14 days, cyclophosphamide 100 mg/kg i.p. on days 1 and 8, methylprednisolone 10 mg/kg and cyclosporin A 10 mg/kg daily from days 1 to 7, and then every other day from days 8 to 14. The number of neurons in the sympathetic ganglia was counted and four subpopulations of mononuclear inflammatory cells were identified by monoclonal antibodies MHC II, CD8 T-cells/NK-cells, CD5 T-cells, CD4 T-cells/macrophages. Our results show that the immunosuppressive drugs used were unable to prevent the guanethidine-induced reduction of sympathetic neurons, although the number, of neurons following guanethidine-methylprednisolone treatment was significantly higher compared with guanethidine alone in both athymic and euthymic rats. The identification of mononuclear cells in the sympathetic ganglia showed that the CD8/NK and CD5 populations were the populations primarily responding to guanethidine treatment. Both CD8/NK and CD5 populations were absent without guanethidine, but increased significantly following guanethidine in both athymic and euthymic animals. None of the immunosuppressive drugs used could prevent the guanethidine-induced rise in the CD8/NK population in neither athymic nor in euthymic rats. The rise in the CD5 population was suppressed following treatment with all immunosuppressive drugs in athymic rats, but only following methylprednisolone in euthymic animals. These results indicate that guanethidine induces proliferation of T-cells in euthymic rats and non-functional CD5 positive pre T-cells in athymic animals. The CD5 population in both athymic and euthymic animals appears relatively more sensitive to immunosuppressive drugs than the NK-cell population also activated by guanethidine. This relatively resistant NK-cell population seems to play an important role in the guanethidine-induced destruction of sympathetic neurons and can explain why the guanethidine-induced immunological reaction could not be fully prevented by the immunosuppressive drugs used. The conclusion is that guanethidine induces destruction of sympathetic neurons by a NK-cell-mediated reaction.

Myelin sheath survival after guanethidine-induced axonal degeneration

Membrane-membrane interactions between axons and Schwann cells are required for initial myelin formation in the peripheral nervous system. However, recent studies of double myelination in sympathetic nerve have indicated that myelin sheaths continue to exist after complete loss of axonal contact (Kidd, G. J., and J. W. Heath. 1988. J. Neurocytol. 17:245-261). This suggests that myelin maintenance may be regulated either by diffusible axonal factors or by nonaxonal mechanisms. To test these hypotheses, axons involved in double myelination in the rat superior cervical ganglion were destroyed by chronic guanethidine treatment. Guanethidine-induced sympathectomy resulted in a Wallerian-like pattern of myelin degeneration within 10 d. In doubly myelinated configurations the axon, inner myelin sheath (which lies in contact with the axon), and approximately 75% of outer myelin sheaths broke down by this time. Degenerating outer sheaths were not found at later periods. It is probably that outer sheaths that degenerated were only partially displaced from the axon at the commencement of guanethidine treatment. In contrast, analysis of serial sections showed that completely displaced outer internodes remained ultrastructurally intact. These internodes survived degeneration of the axon and inner sheath, and during the later time points (2-6 wk) they enclosed only connective tissue elements and reorganized Schwann cells/processes. Axonal regeneration was not observed within surviving outer internodes. We therefore conclude that myelin maintenance in the superior cervical ganglion is not dependent on direct axonal contact or diffusible axonal factors. In addition, physical association of Schwann cells with the degenerating axon may be an important factor in precipitating myelin breakdown during Wallerian degeneration.

Effect of guanethidine on dopamine in small intensely fluorescent cells of the superior cervical ganglion of the rat

To determine the portion of ganglionic dopamine stored in the small intensely fluorescent (SIF) cells of the superior cervical ganglion, rats were treated chronically with the neurotoxin guanethidine (50 mg/kg i.p. daily for 6, 13 or 18 days) which destroys noradrenergic neurons. The guanethidine effect was assessed in the ganglion using biochemistry of dopamine and norepinephrine and immunocytochemistry of tyrosine hydroxylase (TH) and dopamine beta-hydroxylase (DBH). After 18 days of treatment, the ganglionic norepinephrine content was reduced by 80%, but the dopamine content was reduced by only 20%. Morphologic analysis of ganglia stained to distinguish noradrenergic neurons (TH positive, DBH positive) and SIF cells (TH positive, DBH negative) indicated that guanethidine treatment reduced the number of noradrenergic neurons by 70%, dropping from 19413 +/- 1402 to 6515 +/- 1296 per ganglion, but increased the number of dopaminergic SIF cells by 80% from 578 +/- 150 to 1056 +/- 151 per ganglion. Based on these findings, it is concluded that a substantial portion of the dopamine in the rat superior cervical ganglion is located outside the noradrenergic neurons, i.e. in the SIF cells. Extrapolating the data obtained using guanethidine versus control rat leads to infer that although the proportion of SIF cells in the superior cervical ganglion is small (3 +/- 1% of the SIF and noradrenergic neurons combined), about 40% of the total ganglionic dopamine resides in SIF cells, with the remainder serving as precursor in noradrenergic neurons.

Sympathetic and nonsympathetic neuropeptide Y-containing nerves in the rat myocardium and coronary arteries

We have examined the neuropeptide Y-containing intrinsic nerves of the heart in young (6-week-old) and adult (4-month-old) rats to determine whether they project to the coronary arteries or are capable of doing so if the neuropeptide Y-containing extrinsic nerves are removed. Chronic treatment of neonates with guanethidine was used to permanently destroy the sympathetic nerves. In the young treated animals, 33-54% of the neuropeptide Y remained in the heart despite a 90-99% reduction in norepinephrine; these proportions did not change in the animals that were allowed to develop to adulthood. The level of neuropeptide Y in the right atrium of young animals was unexpectedly high (252 +/- 28.7 pmol/g) compared with adults (75.4 +/- 18.8 pmol/g). The coronary arteries in the control rats received a moderately dense supply of neuropeptide Y-containing nerves; after guanethidine, all neuropeptide Y-containing nerves innervating the large coronary arteries disappeared, but some were still seen in association with small resistance vessels. No compensatory proliferation of the intrinsic neuropeptide Y-containing neurons occurred in the adult sympathectomized animals, and the intrinsic nerves did not reinnervate the large coronary arteries. These results are discussed in relation to the clinical syndrome of coronary artery spasm.

Identification of the mononuclear cell infiltrate in the superior cervical ganglion of athymic nude and euthymic rats after guanethidine-induced sympathectomy

Guanethidine sulphate 40 mg/kg intraperitoneally for 14 days induced chromatolysis and nerve cell death in the superior cervical ganglia of athymic nude (rnu/rnu) LEW/Mol rats and their euthymic (+/rnu) LEW/Mol heterozygous littermates. Histologically the sympathetic ganglia were dominated by an infiltration of small inflammatory cells. By means of monoclonal antibodies these cells were identified. The number of B-lymphocytes increased following guanethidine in both athymic and euthymic rats. The number of T-lymphocytes increased to a great extent in euthymic rats, but was virtually missing in athymic rats. The number of NK-cells and monocytes/macrophages increased in both athymic and euthymic rats. The conclusion is, that guanethidine exerts a direct effect on sympathetic ganglion cells followed by a thymus-independent immune response.

Neurotrophic molecules

Neurotrophic molecules have a profound influence on developmental events such as naturally occurring cell death, differentiation, and process outgrowth. Despite their striking effects on developing neurons, a role for these molecules in the pathogenesis or therapy of neurological disease has not yet been defined. However, a variety of recent advances promise to provide the techniques necessary to assess the potential relevance of neurotrophic molecules to clinical neurology. In this article we review recent investigations into the biological effects, regulation of production, and mechanisms of action of the best characterized trophic molecule, nerve growth factor. In addition we review studies characterizing brain-derived neurotrophic factor and other putative neurotrophic molecules. Finally, we discuss how pharmacological effects of these molecules may be relevant to the therapy of disease states as well as neural regeneration.

Guanethidine-induced sympathectomy in the nude rat

Guanethidine sulphate 40 mg/kg was administered intraperitoneally daily for 14 days to normal Lewis rats and athymic nude rats of a Lewis background (rnu/rnu). Histological examination of the superior cervical ganglia demonstrated a pronounced chromatolysis of the neurones and a loss of the major part of the nerve cells accompanied by an increased number of small mononuclear inflammatory cells. The extent of chromatolysis and nerve cell death induced by guanethidine did not differ between normal and nude rats, whereas the increase of the number of mononuclear cells was lower in the nude rats than in the normal rats (163 and 268 per cent respectively of the saline treated controls, P less than 0.01). Since guanethidine induced nerve cell death in the T-cell deficient nude rat to the same extent as in normal rats, it is concluded, that the effect is caused by either a thymus-independent immune-response or by a direct toxic effect.

Guanethidine adrenergic neuropathy: an animal model of selective autonomic neuropathy

Chronic administration of guanethidine to adult rats induces a selective autoimmune adrenergic neuropathy. Physiological and biochemical features of this disorder in the peripheral nervous system were explored in young adult Sprague-Dawley rats given daily intraperitoneal guanethidine monosulfate for 5 weeks. Control rats received daily saline injections. The guanethidine-treated animals gained less weight, had ptosis, and had a lower mean arterial blood pressure in the supine and upright tilted positions. Norepinephrine was depleted in the peroneal, sural, tibial, and vagal nerves, the nutrient artery to the tibial nerve and in the superior cervical sympathetic ganglion of the drug-treated animals. On light microscopy, there was an inflammatory cell infiltrate and neuron loss in the superior cervical ganglion. Caudal and sciatic-tibial nerve conduction values were well preserved in the guanethidine-treated animals as was the 'C' potential derived from unmyelinated vagal fibers recorded in an in vitro chamber. The 'C' potential recorded from the cervical sympathetic trunk, however, was reduced in amplitude correlating with the loss of norepinephrine content in the harvested contralateral superior cervical sympathetic ganglion. The findings further support the view that guanethidine produces a selective adrenergic neuropathy in the rat--providing a useful standard with which to gauge autonomic involvement in other models of neuropathy. In addition, loss of the cervical sympathetic 'C' potential suggests that this presumed preganglionic structure also contains postganglionic adrenergic fibers.

Target organ destruction enhances recovery of choline acetyltransferase activity in adult rat sympathetic ganglia after denervation

We studied the effect of destruction of the adrenergic neuronal population on the recovery of preganglionic choline acetyltransferase activity in adult rat sympathetic ganglia. To produce a partial destruction of the adrenergic system, rats were injected with guanethidine for 4 weeks; the preganglionic nerve to the superior cervical ganglion was then crushed and the guanethidine injections were continued for an additional 3 days to 6 weeks. To determine that the drug was effective, tyrosine hydroxylase activity was assessed; enzymic activity was reduced by 76% or more after guanethidine administration. In addition, electron microscopy studies showed that the number of principal cell-synaptic contacts and vesicle-containing varicosities were decreased by 90% after guanethidine administration. Those measures indicated the drug effectively destroyed the postsynaptic adrenergic neurons. In contrast, crushing the preganglionic nerve in animals not treated with guanethidine did not change tyrosine hydroxylase activity, suggesting minimal nonspecific damage to the ganglion as a result of the lesion. Choline acetyltransferase activity was measured as an index of presynaptic cholinergic integrity. After crush of the preganglionic nerve, there was a gradual recovery of ganglionic choline acetyltransferase activity in the saline-injected rats from 5% of control 3 days after the crush to 49% of control after 6 weeks. On the other hand, in the ganglia of rats administered guanethidine, there was a much enhanced recovery of choline acetyltransferase activity after the nerve crush compared with saline-injected animals; in the guanethidine-injected rats, the ganglionic choline acetyltransferase activity 3 days and 6 weeks after the nerve crush was 15 and 96%, respectively, compared with the uncrushed side. These results demonstrate after destruction of the adrenergic target tissue, recovery of presynaptic choline acetyltransferase activity in the adult rat sympathetic ganglion can still occur after denervation; however, the mechanism(s) that controls the regeneration is altered, so that enzymic activity is enhanced.

Degeneration of myelinated sympathetic nerve fibres following treatment with guanethidine

The specificity and characteristics of the degeneration of myelinated axons after chronic guanethidine treatment have been investigated in sympathetic and non-sympathetic nerves. Adult male Sprague-Dawley rats aged approximately 43 weeks were treated with guanethidine sulphate (50 mg per kg body weight per day) for between ten days and six weeks. Tissues were examined by qualitative and quantitative light and electron microscopy. In the superior cervical (sympathetic) ganglion (SCG), guanethidine treatment produced a 78% decrease (P = 0.009) in the mean number of myelinated fibres at a standard level of section, compared to the contralateral control ganglion which was removed surgically prior to drug treatment. This reduction in the treated SCG was apparent after 10 days, though complete degeneration of nerve cell bodies was not widespread at this stage. Degeneration of unmyelinated axons was extensive. Degenerating myelinated fibres were consistently small in diameter (up to approximately 3 microns). In individual myelinated fibres the earliest signs of degeneration involved disruption of axonal organelles, particularly the cytoskeleton, and focal widening of the periaxonal space. Myelin breakdown followed these events; degeneration of myelin still associated with a structurally intact axon was not observed. Myelin breakdown appeared to take place initially within the Schwann cell, at least to the stage of 'loosened' membranes. However, infiltrating cells were also involved in myelin phagocytosis. At all stages of treatment some small diameter myelinated fibres remained intact, and there was no evidence of degeneration of the larger diameter fibres (up to approximately 15 microns) which are consistently present in small numbers in the SCG. In the cervical sympathetic trunk, which carries preganglionic axons to the SCG and the vagus and sciatic nerves, degeneration only of unmyelinated axons was detected. These results indicate that guanethidine does not exert a primary degenerative influence on myelin or myelinating Schwann cells and that the myelin degeneration observed in the SCG is a secondary result of the previously documented selectively destructive effect of guanethidine on postganglionic sympathetic neurons. Surviving, small diameter myelinated fibres in the SCG could be either preganglionic or processes of resistant postganglionic neurons, while the larger diameter fibres are likely to be somatic. While the cervical sympathetic trunk, vagus and sciatic nerves all contain postganglionic sympathetic fibres it appears that few of these are myelinated, at least at the levels sampled in this study.

Protection from guanethidine-induced neuronal destruction by nerve growth factor: effect of NGF on immune function

The chronic administration of guanethidine causes an immune-mediated destruction of sympathetic neurons in rats. Destruction can be prevented by various immunosuppressive agents, including gamma-irradiation and cyclophosphamide, as well as by administration with nerve growth factor (NGF). Experiments were conducted to determine whether: (1) NGF prevented accumulation of guanethidine within sympathetic neurons; and (2) NGF caused an inhibition of immune function by either blocking proliferation of immune-competent cells or by blocking effector function even in the presence of antigen and activated immune cells. NGF did not prevent accumulation of guanethidine within sympathetic ganglia in vivo, a necessary prerequisite for neuronal destruction, nor was it inhibitory on immune function using several assay systems. NGF, purified by either conventional methods or additionally by HPLC ("ultrapure'), did not inhibit either proliferation of cloned cytotoxic T lymphocytes (CTL) to antigen (class I major histocompatibility antigens) or lysis of target cells bearing the appropriate antigens. In addition, NGF did not exhibit growth stimulating effects in this assay system (i.e. it could not substitute for T cell growth factor). NGF also did not cause an inhibition of either murine or rat allogeneic mixed lymphocyte responses measured by lysis of appropriate target cells or proliferation, respectively. Finally, NGF did not inhibit, but rather appeared to stimulate the antibody response to sheep red blood cells generated in vivo in young rats. Thus NGF does not appear to prevent the immune-mediated neural destruction induced by guanethidine by acting as an immunosuppressive agent, but rather acts by some other mechanism such as preventing expression or recognition of antigen(s) on the sympathetic neuron.

Sociosexual behaviors of female rats during and after chronic treatment with the sympatholytic agent guanethidine

Ovariectomized female rats were chronically administered saline or guanethidine sulfate, a drug that blocks adrenergic neurons and, when chronically administered, results in peripheral sympathectomy. The females were periodically injected with estradiol benzoate and progesterone and tested for sexual behaviors before, during and after the six-week period of daily guanethidine or saline injections. Tests for copulatory behavior included tests for lordotic responsiveness to manual stimulation and tests of sociosexual behaviors displayed by the females in a complex testing environment. The complex environment permitted the test females to control their coital contacts with sexually active males and their interactions with sexually inactive males and ovariectomized female rats. Guanethidine treatment did not alter lordotic responsiveness to manual stimulation but did reduce the frequency of copulatory acts engaged in by the females in the complex environment. During the first test in the complex environment following the start of drug injections, the guanethidine-treated females, in comparison to saline-treated females, displayed a lower frequency of lordotic behavior during coital contacts. The changes in behavior produced by the sympathetic drug, guanethidine, implicate the autonomic nervous system in the regulation of copulatory pacing in the female rat.

Reproductive physiology and behavior in the male rat following acute and chronic peripheral adrenergic depletion by guanethidine

The effect of guanethidine, an adrenergic neuron blocking agent, on sexual behavior, penile reflexes, and spontaneous seminal emission (SSE) in the rat was studied by acute (i.e., 4 hours prior to testing) and daily IP injection of a low (5 mg/kg) and moderately high (25 mg/kg) dose of the drug. Acute low dose treatment eliminated the expulsion of a seminal plug with behavioral ejaculation without affecting sexual behavior; while acute high dose administration significantly decreased the number of intromissions preceding ejaculation and eliminated emission in copula and SSE for 3 days, with no evidence of retrograde ejaculation. Acute high dose treatment also increased the number of long flips displayed in the penile reflex test, and resulted in significant depression in plasma testosterone (T) and luteinizing hormone (LH) levels. Daily injection with the low dose eliminated emission in and ex copula for 4 weeks, without altering sexual behavior or penile reflexes. Seminal emission in copula reappeared more rapidly after stopping injections than SSE. Chronic high dose treatment was also without effect on copulatory activity. There was a partial recovery of emission in copula by the fourth week of treatment, suggesting that a nonadrenergic mechanism had assumed this function. In penile reflex tests conducted after 4 and 8 weeks, significantly fewer erections were displayed by drug-treated animals. During the period of initial recovery of emission in copula, emission during the reflex test was markedly increased, but SSE was decreased. Plasma T was significantly suppressed after two and four weeks of daily injections, but not thereafter, while plasma LH levels were not affected by the drug.

Effect of chemical destruction of adrenergic neurones on some cholinergic mechanisms in adult rat sympathetic ganglia

Rats were treated for 2-6 weeks with guanethidine after which their superior cervical ganglia were removed. Ganglionic tyrosine hydroxylase and alpha-bungarotoxin binding sites were reduced by the guanethidine treatment indicating adrenergic cell body destruction. Choline acetyltransferase activity and acetylcholine content of ganglia were not clearly changed by the guanethidine treatment, indicating that the drug does not destroy presynaptic terminals and that these presynaptic indicators do not adapt markedly to postsynaptic loss. The cholinesterase in the ganglia was reduced by guanethidine treatment, but such ganglia retained their ability to accumulate surplus acetylcholine when they were incubated with physostigmine. This is interpreted as indicating surplus acetylcholine accumulation is a presynaptic phenomenon. Choline uptake by resting ganglia was not reduced as a result of guanethidine treatment nor was it affected by preganglionic denervation. This is interpreted as indicating that during rest, choline uptake is into supporting cells or intraganglionic cells rather than cholinergic nerve terminals or adrenergic cell bodies.

Histologic evaluation of the sympathectomy induced by guanethidine sulfate in neonatal rats

Guanethidine sulfate was administered to rats from birth to 14 days of age. Cell counts were carried out in the superior cervical sympathetic ganglion at 30, 45, and 90 days of age. Massive permanent destruction of sympathetic ganglionic cells was demonstrated during the experimental period. Evidence for a natural loss of neurons during the morphogenesis of the superior cervical sympathetic ganglion is presented.

Immunosuppressive agents prevent guanethidine-induced destruction of rat sympathetic neurons

Chronic administration of guanethidine to rats causes destruction of peripheral sympathetic neurons. Neuronal destruction, characterized morphologically by small cell infiltration and the reduction in the number of neurons within sympathetic ganglia, and biochemically by a marked reduction in tyrosine hydroxylase activity, occurred reproducibly by day 7 of treatment following 5 daily injections of 50 mg/kg guanethidine sulfate. Several observations in the literature suggested that guanethidine-induced destruction may occur by an immunologically mediated mechanism. Experiments were therefore designed to test the effects of immunosuppressive agents on guanethidine sympathectomy. A single exposure to either gamma-irradiation or cyclophosphamide, administered 8 h prior to the initiation of guanethidine treatment, protected against guanethidine-induced destruction in a dose-related manner and was virtually complete with either 900 rads of irradiation or with 100 or 150 mg/kg of cyclophosphamide. Cyclophosphamide afforded complete protection only if administered immediately prior to guanethidine treatment suggesting that it was acting during the proliferative phase of an immune response rather than non-specifically. Pretreatment with either irradiation or cyclophosphamide had no effect on the sympathectomy produced by treatment with either 6-hydroxydopamine or antibodies to nerve growth factor, nor did it prevent the accumulation of guanethidine within the sympathetic ganglia. Concurrent treatment with either azathioprine or dexamethazone also provided partial protection against guanethidine sympathectomy. These results strongly suggest that the destruction of sympathetic neurons induced by guanethidine occurs by an immunologically mediated mechanism.

Chronic guanethidine and adrenal medullary function in the rat

The clinical application of intravenous angiography to study the cervicocerebrovascular system using the digital video subtraction system described in a companion article is reported. About 0.75 ml/kg of a standard 76% iodine contrast solution is injected into an antecubital vein using a power injector. Then 15-20 exposures of the head and neck region at a 1/sec rate are made on the image intensifier. The images are recorded by a high performance video system and the output signal is digitized for subsequent computer manipulation. The subtraction images of these vessels produced by the computer show the vessels clearly, even though they contain very low concentrations of contrast media. Standard exposure factors of 75–80 kVp, 9–10 msec at 800–1,000 mA are used. Clinically pertinent features of the data alteration and flow through the system and the step-by-step computer procedures used to achieve and analyze the various forms of subtracted images are described.

Five experimental and clinical cases demonstrate appropriate applications to cervicocerebrovascular disease: (1) evaluating the effects of surgical and medical therapy on atherosclerosis; (2) providing a screening angiographic test for patients with asymptomatic bruits and/or positive noninvasive studies; (3) evaluating patients who have significant generalized vascular disease either precluding or presenting hazardous contraindications to transarterial catheterization; (4) evaluating significantly aged patients in whom standard angiography has higher risk; and (5) evaluating currently asymptomatic patients who are medically at higher risk for developing atherosclerotic lesions. Numerous examples of the various types of image manipulations are presented: (1) linear subtraction; (2) logarithmic subtraction; (3) alterations of electronic contrast enhancement (map slope); (4) the usefulness of a series of angiographic images; and (5) the importance of multiple projections with this technique.

The effects of drug which destroy the sympathetic nervous system on the retrograde transport of nerve growth factor

It has been proposed that the drugs (6-hydroxydopamine, guanethidine, vinblastine) which are known to destroy sympathetic neurons in neonatal animals do so by preventing the accumulation of retrogradely transported nerve growth factor (NGF). It was found, consistent with the proposal, that administration of 6-hydroxydopamine (100 mg/kg s.c.) or vinblastine (0.4 mg/kg s.c.) 16 h prior to the administration of [125I]NGF complete prevented the accumulation of retrogradely transported [125I]NGF in superior cervical ganglia of neonatal rats. Administration of 6-hydroxydopamine or vinblastine to adult rats (where it does not cause sympathetic neuron cell death) did not completely prevent the retrograde transport of NGF, although 6-hydroxydopamine produced an alteration of the time course of accumulation (early times unaffected, later times depressed). The administration of guanethidine to adult rats (50 mg/kg/day) produced a modest decrease in the accumulation of NGF (40-60%). It would appear, however, that this decrease cannot account for the cytotoxic effects of guanethidine since: (1) sub-cytotoxic doses of guanethidine and non-cytotoxic guanidinium blocking agents also produce modest decreases in the retrograde transport in NGF; and (2) the retrograde transport of [125I]NGF is not affected in neonatal animals until after the neurons are clearly damaged. Hence, the data are entirely consistent with the hypothesis that NGF deprivation caused by 6-hydroxydopamine and vinblastine is the mechanism of the cytotoxic effects of these drugs on sympathetic neurons in neonatal animals. Guanethidine destroys sympathetic neurons by some other mechanism.

Unique resistance to guanethidine-induced chemical sympathectomy of spontaneously hypertensive rats: a resistance overcome by treatment with antibody to nerve growth factor

The chronic administration of high doses of guanethidine to rats produces complete destruction of the peripheral sympathetic nervous system. In a study of the effect of guanethidine-induced sympathectomy on the development of hypertension is spontaneous hypertensive rats (SHR, Okomoto strain), only a partial sympathectomy could be produced as assessed by biochemical parameters (tyrosine hydroxylase activity in ganglia and tissue norepinephrine concentrations) and by evaluation of response to stimulation of vasomotor outflow in pithed rat preparations. Other strains of rats (Sprague-Dawley, American Wistar, Kyoto Wistar) were uniformly sensitive to guanethidine sympathectomy. The resistance to guanethidine was not due to a lower accumulation of guanethidine in the neurons of SHR. Addition to the guanethidine treatment of low doses of antibody to nerve growth factor (NGF), which itself produced only a modest sympathectomy, resulted in an almost complete sympathectomy. SHR did not become hypertensive when sympathectomized by combined guanethidine-anti NGF. These results show that the sympathetic neurons of SHR differ from those of other strains with respect to sensitivity to guanethidine cytotoxicity and suggest the possibility of a role for NGF in that altered responsiveness.

Adrenergic responses of the rabbit stomach serosal strip and their modification by monoamine oxidase inhibitors and anti-adrenergic drugs

The rabbit stomach serosal strip, was found to contract to adrenaline and noradrenaline but not to isoprenaline. The contractile response could be totally abolished by phenoxybenzamine but was not influenced by propranolol, indicating that the preparation has almost exclusively alpha-adrenoceptors. The responses to adrenaline and noradrenaline were markedly potentiated in the presence of monoamine oxidase inhibitors, guanethidine or reserpine, indicating the presence of MAO activity in the tissue and possible catecholamine stores. The functional state of the latter has not been conclusively established, since tyramine, an indirectly acting amine, was unable to elicit a response qualitatively similar to that of adrenaline, even in the presence of nialamide or tranylcypromine.

Modification and characterization of the permanent sympathectomy produced by the administration of guanethidine to newborn rats

The administration of guanethidine to newborn rats has been shown to produce a permanent sympathectomy with potential advantages over immunosympathectomy and 6-hydroxydopamine-induced chemical sympathectomy. In this paper, we report on a revised treatment regimen involving initiation of treatment (50 mg/kg/day) on day 7 after birth and continuing for 3 weeks. Animals treated by this protocol have a low mortality rate (approx. 10% above saline-treated controls) and no permanent growth deficit. Analysis of tyrosine hydroxylase activity in and light microscopic examination of superior cervical ganglia of the guanethidine-treated animals indicate complete destruction of sympathetic neurons by the end of the second week of treatment. During and after treatment there are no decreases in norepinephrine in whole brain of the treated animals. Norepinephrine levels in peripheral tissues are markedly reduced at both 9 and 16 weeks of age. Stimulation of vasomotor outflow produces no increase in blood pressure in guanethidine-treated rats at 9 or 26 weeks of age, indicating a complete and permanent functional denervation of the vasculature. The adrenal glands of the guanethidine-treated animals are not destroyed, but rather respond, apparently by transsynaptic induction, with increases in tyrosine hydroxylase and epinephrine content. Interestingly, despite the continued deprivation of a peripheral sympathetic nervous system in these animals. adrenal tyrosine hydroxylase and epinephrine levels return to control levels by 10 weeks of age. These data indicate that administration of guanethidine to newborn rats produces a very complete and permanent sympathectomy with significant advantages over immunosympathectomy and 6-hydroxydopamine-induced chemical sympathectomy.

An ultrastructural study of sympathetic ganglion satellite cells in the rat. 2. Effect of preganglionic sympathectomy

The ultrastructure of satellite cells of the rat superior cervical ganglion was studied following preganglionic sympathectomy.Several distinct morphological alterations were observed: (a) enlargement of the intercellular space between the ganglion cells and the satellite cells, (b) dilation of the granular endoplasmic reticulum and loss of attached ribosomes, and (c) swelling of the mitochondria with disorganization of the cristae mitochondriales. The presence of degenerating nerve fibers and synaptic boutons was also noted.

Effects of guanethidine on paraganglionic cells in the superior cervical ganglion of the rat

Paraganglionic cells in the rat superior cervical ganglion were investigated by fluorescence and electron microscopy following treatment with guanethidine for 5-30 days. Control animals received saline and guanidine. Fluorescence cytophotometric measurements revealed a general decrease in the catecholamine content of paraganglionic cells in guanethidine-treated animals. However a few cell clusters showed focal increases. Similarly by electron microscopy there was a general decrease of cell clusters showing increases. -- guanethidine -- as well as guanidine--treated animals showed non-specific cytological alterations such as mitochondrial swelling and increase of cytoplasmic glycogen. However no changes of catecholamine contents and of dense core vesicles were noted in control animals. These results confirm the conception that in rat paraganglionic cells the dense core vesicles are the main storage site of catecholamines. The marked difference in the response of some cell culsters to the experimental treatment can be considered as evidence of functional heterogeneity of this cell population in the rat superior cervical ganglion.

Functional and fine structural characteristics of the sensory neuron blocking effect of capsaicin

In the eye of rats the long-lasting specific desensitization induced by local or systemic capsaicin treatment is characterized by three phases: 1. complete insensitivity, 2. decreased sensitivity and a tendency to rapid adaptation, 3. normal initial sensitivity with a tendency to rapid adaptation to chemical pain stimuli. A low density of nicrovesicles and swollen mitochondria were found after local capsaicin treatment in certain nerve endings of the cornea of rats, but no signs of axonal degeneration or alteration in fine structure of non-neural elements were seen. Systemic capsaicin desensitization induced selective mitochondrial swelling in B type of neurons of the trigeminal ganglion which was demonstrable even 60 days after the pretreatment. Actinomycin-D, 8-azaguanine, 6-azauracil, aminopterin, mannomustin or cycloheximide in high doses did not alter the desensitizing effect of systemic capsaicin treatment. However, pretreatment of rats with colchicine or vinblastine prolonged the desensitizing effect of local capsaicin application, probably by inhibiting the axonal flow. It is concluded that capsaicin is a specific sensory neuron blocking agent having a practically irreversible effect in rats and guinea-pigs.