Ornithine decarboxylase activity in dorsal root ganglia of regenerating frog sciatic nerve

Polyamines increase in sympathetic neurons and non-neuronal cells after axotomy and enhance neurite outgrowth in nerve growth factor-primed PC12 cells

Following axonal damage, sympathetic neurons are capable of regenerating and reinnervating their target tissues. Some years ago exogenous administration of polyamines was shown to enhance this regeneration. Recently, it was found that axonal injury leads to a dramatic up-regulation of the expression of arginase I in sympathetic neurons. This enzyme catalyzes the conversion of arginine to ornithine, which can subsequently be converted to the diamine putrescine and, ultimately, to the polyamines spermidine and spermine. In the present study, using an antiserum that reacts with both spermidine and spermine, we have found an increase in polyamine levels in both neurons and non-neuronal cells in the superior cervical ganglion 2 and 5 days following transection of the ganglion's postganglionic trunks. Using PC12 cells primed with nerve growth factor and then stripped off the culture dish and replated as a model system for axotomized sympathetic neurons, we found that spermidine treatment, with or without nerve growth factor, resulted in an increased percentage of cells with a neurite whose length was at least twice the diameter of the neuron's cell body. These increases could be seen within 48 h and were still evident after 8 days. Together, these data support the possibility that endogenous polyamines are involved in the normal regeneration which occurs following sympathetic axonal damage.

Polyamines and cerebral ischemia

It has been well established that alterations in polyamine metabolism are associated with animal models of global ischemia. Recently, this has been extended to include models of focal ischemia and traumatic brain injury. There is much evidence to support the idea that polyamines may play a multifaceted detrimental role following ischemia reperfusion. Due to the deficit of knowledge about their physiology in the CNS, the link between ischemia-induced alterations in polyamine metabolism and neuronal injury remains to be substantiated. With the recent revelation that polyamines are major intracellular modulators of inward rectifier potassium channels and certain types of NMDA and AMPA receptors, the long wait for the physiologic relevance of these ubiquitous compounds may be in sight. Therefore, it is now conceivable that the alterations in polyamines could have major effects on ion homeostasis in the CNS, especially potassium, and thus account for the observed injury after cerebral ischemia.

Effects of cilostazol, an antiplatelet agent, on axonal regeneration following nerve injury in diabetic rats

To evaluate the ability of cilostazol, an antiplatelet and vasodilating agent, to promote axonal regeneration in streptozotocin-induced diabetic rats, the time until beginning of regeneration (initial delay) and the axonal regeneration rate of the sciatic nerve were estimated using the pinch test, and ornithine decarboxylase activity was measured in dorsal root ganglia. At 5 weeks of diabetes, axonal regeneration rate remained unchanged but the initial delay was prolonged and ornithine decarboxylase induction was delayed in diabetic rats compared with those in normal rats. Cilostazol had little effect on these parameters in normal or diabetic rats. At 10 weeks of diabetes, diabetic rats showed both prolongation of initial delay and a decrease in axonal regeneration rate. Cilostazol markedly increased axonal regeneration rate in diabetic rats. Ornithine decarboxylase induction following nerve injury disappeared almost completely in diabetic rats but was maintained by cilostazol treatment. The effect of cilostazol in diabetic rats is thought to be mediated through its preventive effect on circulatory disorders. The active site of the drug appears to be early processes in nerve regeneration before ornithine decarboxylase induction. Further, the results suggest that the both axonal regeneration and this induction are sensitive to circulatory defects in diabetes.

Glucocorticoid receptors and actions in the spinal cord of the Wobbler mouse, a model for neurodegenerative diseases

We have studied glucocorticoid receptors (GR) and actions in the spinal cord of the Wobbler mouse, a model for amyotrophic lateral sclerosis and infantile spinal muscular atrophy. Basal and stress levels of circulating corticosterone (CORT) were increased in Wobbler mice. Single point binding assays showed that cytosolic type II GR in the spinal cord of Wobbler mice of both sexes were slightly reduced compared with normal littermates. Saturation analysis further demonstrated a non-significant reduction in Bmax with increased Kd. In the hippocampus, however, we found down-regulation of GR, a probable response to increased CORT levels. We also found that the basal activity of ornithine decarboxylase (ODC), a rate-limiting enzyme of polyamine biosynthesis, was higher in Wobbler mice than in control animals. Both groups showed a two-fold stimulation of ODC activity after treatment with dexamethasone (DEX). Additionally, Wobbler mice presented with an intense proliferation of astrocytes immunoreactive (ir) for glial fibrillary acidic protein (GFAP) in grey and white matter of the spinal cord. The enhanced GFAP-ir was attenuated after four days of treatment with a corticosterone (CORT) pellet implant, producing a pharmacological increase in peripheral circulating CORT. Taking into consideration the content of GR and the changes in ODC activity and GFAP-ir brought about by glucocorticoids, we suggest that Wobbler mice are hormone responsive. Further elucidation of glucocorticoid effects in this model may be relevant for understanding the possible use of hormones in human neurodegenerative diseases.

Time-dependent effects of dexamethasone on glutamate binding, ornithine decarboxylase activity and polyamine levels in the transected spinal cord

Evidence exists that the spinal cord is a glucocorticoid-responsive tissue, and glucocorticoids have beneficial effects in cases of spinal cord injury. Using sham-operated rats, spinal cord transected (TRX) rats, and TRX animals receiving dexamethasone (DEX) 5 min or 24 h post-lesion, we have examined the following GC-sensitive parameters 6 h after DEX treatment: (1) binding of glutamate to NMDA-sensitive receptors; (2) the activity of ornithine decarboxylase (ODC); and (3) levels of polyamines. We found that glutamate binding in the dorsal horn (Laminae 1-2) and central canal were upregulated in TRX rats, whereas DEX had an additional stimulatory effect. 24 h post-lesion, glutamate binding was unmodified in TRX or TRX+DEX rats. ODC activity was increased 10-fold in rats killed on the day of transection but only 2-fold 24 h post-lesion. DEX reduced ODC activity on transection day but highly increased it when given 24 h after surgery. The content of the polyamines spermidine and spermine were unchanged after TRX or DEX treatment, in contrast to putrescine which increased in TRX rats and further increased in TRX+DEX rats when measured the day post-lesion. Thus, parallel increases in ODC and putrescine 1 day after the lesion, suggest that glucocorticoid effects on growth responses due to polyamines may develop at a late period. The changes of glutamate binding in the dorsal horn and central canal due to early glucocorticoid treatment, further suggest hormonal modulation of neurotransmission in sensitive areas of the deafferented spinal cord.

Clinical and neurophysiologic response of myopathy and neuropathy in long-chain L-3-hydroxyacyl-CoA dehydrogenase deficiency to oral prednisone

The purpose of this study was to evaluate the clinical and neurophysiologic responses to oral prednisone therapy in a boy with enzymatically confirmed long-chain L-3-hydroxyacyl-CoA dehydrogenase deficiency in biopsied muscle and cultured skin fibroblasts. This boy presented with progressive limb girdle myopathy, recurrent myoglobinuria, peripheral sensorimotor axonopathy, and intraventricular conduction delays. Prior to prednisone therapy, at age 8 years, he exhibited marked distal weakness greater than proximal weakness with a waddling and high-steppage gait, Gowers' maneuver (10 s to rise from the floor), fatigue after 3-20 yards of walking and the ability to climb only 2 stairs. Serum levels of creatine kinase rose from 34 to 4,124 U/L following mild exertion. Nerve conduction studies revealed progressive axonopathy with secondary demyelination. Four weeks after initiation of oral prednisone (0.75 mg/kg/day) therapy, there was approximately a 100% increase in power and endurance. He was able to walk at least 100 yards before tiring, could rise from sitting on the floor in 3-4 s, and was able to climb 20 steps in 30 s. There was concurrent improvement in nerve conduction studies. Prednisone was gradually withdrawn over the next 4 months to 0.19 mg/kg/day; lower doses of 0.08 mg/kg/day resulted in a marked deterioration in power to the prior state. Although 0.19 mg/kg/day did not maintain the peak power achieved at 0.75 mg/kg/day, it provided adequate baseline power and endurance. It is concluded that there was a significant clinical and neurophysiologic response to prednisone at a dosage > or = 0.16 mg/kg/day. Prednisone may stabilize muscle and neuronal plasma membranes, as well as the fatty acid oxidation enzyme complex in the mitochondrial membrane.

Axonal transport and morphological changes following nerve compression. An experimental study in the rabbit vagus nerve

Axonal transport and morphological changes were studied in the rabbit vagus nerve after the nerves had been subjected to compression at either 0, 50 or 200 mmHg for two hours. Slow axonally transported proteins, tubulin and actin, were radiolabelled with 35S-methionine two, seven or 14 days after the injury and the distribution of radiolabelled tubulin and actin within component b of slow transport was measured three days later by densitometric analysis of fluorographs of polyacrylamide gel. No significant differences were found in the distribution of tubulin two (50 and 200 mmHg) or seven (200 mmHg) days after injury, but at 14 days (200 mmHg) there was significantly increased radiolabelling of tubulin relative to actin in the nerve 60 to 70 mm from the nodose ganglion. Morphometric measurements of the nerve cell bodies two days after the compression injury at 200 mmHg revealed no significant changes. Previous work has shown that morphological changes, similar to those found after axotomy, were present in nerve cell bodies seven days after a compression injury. This, taken together with the present results, indicates that compression can induce both morphological and biochemical changes in the neurone. The altered axonal transport of tubulin associated with nerve injury follows a slower time course and does not precede the morphological changes. The findings may be of relevance when discussing the double crush syndrome.

Estradiol increases glucocorticoid binding and glucocorticoid induction of ornithine decarboxylase in the rat spinal cord

Previous results demonstrated that estradiol (E2) treatment of ovariectomized-adrenalectomized (OVX-ADX) rats increased glucocorticoid (GC) binding in brain regions. The experimental protocol was extended to the spinal cord, a GC target tissue in which ornithine decarboxylase (ODC) is markedly induced by GC treatment. First, we measured GC binding to type I and type II receptors in ventral horn, dorsal horn and lateral funiculus of OVX-ADX rats treated during 4 days with E2 or vehicle. In E2-treated rats, type II receptors increased solely in dorsal horn, whereas type I sites remained unchanged. Second, in a group of OVX-ADX rats receiving dexamethasone (DEX), pretreatment with E2 superinduced ODC in ventral horn and lateral funiculus, but not in dorsal horn. Third, we found that the dorsal horn was relatively enriched in E2 receptors compared to other areas. Therefore, E2 stimulation of GC binding to type II sites may be mediated through E2 receptors localized in the dorsal horn. We suggest that combined treatment with E2 and DEX employs a transsynaptic mechanism for ODC induction at the ventral horn and lateral funiculus, with hormonal interaction taking place at the dorsal horn level.

Polyamine metabolism in different pathological states of the brain

Biosynthesis of the polyamines spermidine and spermine and their precursor putrescine is controlled by the activity of the two key enzymes ornithine decarboxylase (ODC) and S-adenosylmethionine decarboxylase (SAMDC). In the adult brain, polyamine synthesis is activated by a variety of physiological and pathological stimuli, resulting most prominently in an increase in ODC activity and putrescine levels. The sharp rise in putrescine levels observed following severe cellular stress is most probably the result of an increase in ODC activity and decrease in SAMDC activity or an activation of the interconversion of spermidine into putrescine via the enzymes spermidine N-acetyltransferase and polyamine oxidase. Spermidine and spermine levels are usually less affected by stress and are reduced in severely injured areas. Changes of polyamine synthesis and metabolism are most pronounced in those pathological conditions that induce cell injury, such as severe metabolic stress, exposure to neurotoxins or seizure. Putrescine levels correlate closely with the density of cell necrosis. Because of the close relationship between the extent of post-stress changes in polyamine metabolism and density of cellular injury, it has been suggested that polyamines play a role in the manifestation of structural defects. Four different mechanisms of polyamine-dependent cell injury are plausible: (1) an overactivation of calcium fluxes and neurotransmitter release in areas with an overshoot in putrescine formation; (2) disturbances of the calcium homeostasis resulting from an impairment of the calcium buffering capacity of mitochondria in regions in which spermine levels are reduced; (3) an overactivation of the NMDA receptor complex caused by a release of polyamines into the extracellular space during ischemia or after ischemia and prolonged recirculation in the tissue surrounding severely damaged areas; (4) an overproduction of hydrogen peroxide resulting from an activation of the interconversion of spermidine into putrescine via the enzymes spermidine N-acetyltransferase and polyamine oxidase. Insofar as a sharp activation of polyamine synthesis is a common response to a variety of physiological and pathological stimuli, studying stress-induced changes in polyamine synthesis and metabolism may help to elucidate the molecular mechanisms involved in the development of cell injury induced by severe stress.

Regeneration of an adult peripheral nerve preparation in culture

The methods used to maintain the vagus nerve from the adult rat in culture and how regeneration is studied in this preparation are described. A hypothesis is presented on the triggering of the cell body reaction. It is suggested that this reaction is initiated by proteins synthesized in nonneuronal cells at the site of a nerve lesion. These proteins, referred to as regenerins, reach the nerve cell body by retrograde axonal transport, where they initiate the regeneration process.

Polyamines enhance recovery after sciatic nerve trauma in the rat

Spermine, a polyamine, is known to enhance motor functional recovery after a sciatic nerve lesion in the rat. The effect of spermine on the sensory axonal elongation after a sciatic crush was studied with the pinch-test from the sural nerve in the rat. The effect of spermidine, another polyamine, on the motor functional recovery after a trauma was studied by using the toe-spreading ability as an indicator of motor recovery after a sciatic crush in the rat. Spermine enhanced the rate of regeneration of the sensory axons by 16%. Spermidine enhanced the rate of the motor recovery by 30%. These results suggest that not only spermine but also spermidine enhance regeneration of peripheral somatic nerves.

Transcription-dependent and -independent induction of cerebral ornithine decarboxylase

Ornithine decarboxylase (ODC; EC 4.1.1.17) is a highly inducible, rate-limiting enzyme of the polyamine pathway. We have studied the mechanisms that lead to the induction of ODC activity in response to electrical stimulation in three brain regions. Hippocampal ODC activity was found to exhibit much larger elevations than that of the neocortex and the cerebellum. The levels of ODC gene expression were also followed to examine its relationship to the existing regional differences in ODC activity. In the neocortex, there was an elevation of both the ODC mRNA and enzyme activity. However, the hippocampal ODC mRNA level was not increased by electroconvulsive shock. Furthermore, the effects of hormonal changes and seizures on these regional differences in ODC induction were also examined. Adrenalectomy did not affect ODC activity, but pretreatment with the anticonvulsant MK-801 caused a depression of the induced levels of enzyme activity. Our data suggest that ODC activity in all the brain regions studied is directly elevated by electrically stimulated seizures. However, this induced ODC activity may or may not involve enhanced gene expression.

Survival and regeneration of the adult rat vagus nerve in culture

Here I report that the vagus nerve from the adult rat survives in culture for several days. The cultured preparation retains its ability to propagate action potentials and transport proteins within its sensory axons. Regeneration could be induced by a crush lesion and nerve fibers regenerated at a rate of 1.4 mm/day. The production of proteins, later subjected to retrograde axonal transport, and outgrowth of neurites could be prevented by inhibition of protein synthesis at the site of the crush lesion.

Differential effects of difluoromethylornithine on basal and induced activity of cerebral ornithine decarboxylase and mRNA

The induction of the activity of cerebral ornithine decarboxylase (EC 4.1.1.17) and mRNA by electrical stimulation exhibits regional differences. The effects of the enzyme inhibitor difluoromethylornithine on these regional variations was examined. Administration of this inhibitor resulted in pronounced depression of both basal and induced activity of ornithine decarboxylase in the hippocampus. Basal activity of the enzyme in the neocortex and the cerebellum appeared to be resistant to difluoromethylornithine but the induced enzyme activity was sensitive to the effects of this inhibitor. Susceptibility to difluoromethylornithine may be directly correlated with a slower turnover rate for ornithine decarboxylase. These results suggest that ornithine decarboxylase in the hippocampus may possess a longer half-life than its counterparts in other regions of the brain. Pretreatment with difluoromethylornithine had no effect on the induced ornithine decarboxylase mRNA in the neocortex. Thus, elevated activity of ornithine decarboxylase enzyme, due to electrical stimulation, appears to not have any effect on either the transcription or the decay rate of the induced ornithine decarboxylase mRNA. These findings support the concept of region-specific regulation of cerebral ornithine decarboxylase.

Polyamines can protect against ischemia-induced nerve cell death in gerbil forebrain

We have previously demonstrated that administration of the polyamines putrescine, spermidine, or spermine can prevent neuronal degeneration in rats during naturally occurring cell death or after injurious treatments such as nerve injury or monosodium glutamate neurotoxicity. The present study demonstrates that also in adult gerbils polyamine treatment can protect forebrain neurons from degeneration after ischemia. Neurons in the hippocampus and striatum were rescued from delayed cell death after brief (5 min) global ischemia in gerbils which were treated with daily injections (10 mg/kg) of polyamines. The evidence accrued, so far, indicates that systemic polyamines can protect a wide variety of central and peripheral neurons from natural or induced degeneration.

The effects of polyamines and polyamine inhibitors on rat sciatic and facial nerve regeneration

The effects of exogenous polyamines and polyamine biosynthetic pathway inhibitors on regenerating nerves were examined in adult male rats following nerve transection and surgical repair. Several studies have demonstrated the efficacy of exogenous polyamines in promoting the functional recovery of peripheral nerves following crush or freeze injuries in the rat. In order to simulate clinical peripheral nerve surgery, we studied these effects after complete nerve transection and evaluated regeneration by counting axons. There was no statistical difference in axon number with and without polyamines and in the presence of inhibitors and inhibitors with end product addition. Our study suggests that the difference in recovery seen in previous studies is not mediated by a change in axon number.

Impaired induction of nerve ornithine decarboxylase activity in the streptozotocin-diabetic rat is prevented by the aldose reductase inhibitor ponalrestat

1. The present study was designed to investigate if the aldose reductase inhibitor ponalrestat is capable of preventing the impairment of the response of ornithine decarboxylase (ODC) to nerve crush in streptozotocin (STZ)-diabetic rats. 2. ODC activity was measured in the dorsal root ganglia of crushed and uncrushed contralateral sciatic nerve of non-diabetic, ponalrestat-treated non-diabetic, STZ-diabetic and ponalrestat-treated STZ-diabetic rats. 3. Twenty four hours after crush, a significant (P less than 0.001) increase in the ratio of ODC activity in ganglia of crushed relative to uncrushed nerves was found in non-diabetic but not in diabetic rats, as expected. In the ponalrestat-treated diabetic rats the ratio was significantly higher (P less than 0.001) than that in the untreated diabetic rats and was not different from that in the non-diabetic group. 4. Ponalrestat also significantly decreased absolute levels of ODC activity in ganglia of uncrushed nerves from diabetic and non-diabetic animals. Despite the near-normal induction of ODC activity by nerve crush in the ponalrestat-treated diabetic animals, absolute ODC activity remained lower than that in ganglia of uncrushed nerves from non-diabetics. 5. We conclude that ponalrestat is able to prevent the impaired induction of ODC in experimental diabetes. The results, however, call into question the relationship between impaired ODC induction and diabetes-induced defects in nerve regeneration, which are insensitive to ponalrestat.

The effect of acrylamide on the induction of ornithine decarboxylase in the dorsal root ganglion of the rat

Injury of the rat sciatic nerve is accompanied by an increased activity of the enzyme ornithine decarboxylase (ODC) in dorsal root ganglia. This increase is impaired in streptozotocin-induced diabetes, in which retrograde axonal transport of proteins is reduced. In order to confirm the relationship between altered axonal transport and ODC induction we treated rats with acrylamide i.p. to cumulative doses of 150 and 350 mg/kg. One sciatic nerve was crushed under anaesthesia and 24 h later dorsal root ganglia were removed and assayed for ODC activity by a dual-label radioenzymatic method. The ratio of activity of 2.41 +/- 0.57 (crushed side over control side) was reduced to 1.66 +/- 0.9 and 1.7 +/- 0.65 after acrylamide treatment at 150 and 350 mg/kg, respectively. The results are consistent with the postulated role of retrograde axonal transport in the cell body responses to nerve injury and may explain the effect of acrylamide on nerve regeneration.

The effect of 2,5-hexanedione on the induction of ornithine decarboxylase in the dorsal root ganglion of the rat

Rat dorsal root ganglia respond to sciatic nerve injury with an increase in the activity of the enzyme ornithine decarboxylase (ODC). The increase is impaired under certain conditions (e.g. diabetes, Vinca alkaloid treatment) where retrograde axonal transport is reduced. The purpose of the experiments was to determine if the neurotoxin 2,5-hexanedione, also known to interfere with retrograde axonal transport, similarly affected ODC induction. Rats were treated with 2,5-hexanedione i.p. to a cumulative dose of 6 and 8 g/kg. One sciatic nerve was crushed under anaesthesia and 24 h later the dorsal root ganglia were removed and assayed for ODC activity by a radioenzymatic method. The ratio of ODC activity of 1.57 +/- 0.58 (crushed side over control side) was reduced to 1.02 +/- 0.41 1.08 +/- 0.39 after 2,5-hexanedione at 6 g and 8 g/kg, respectively. The enzyme was not inhibited by addition of 2,5-hexanedione in vitro. The results confirm the role of retrograde axonal transport in nerve cell responses to injury and are consistent with the effects of 2,5-hexanedione on nerve regeneration.

The role of ornithine decarboxylase and polyamines in regeneration of the frog sciatic nerve

The current study examined both in vivo and in vitro the effects of alpha-difluoromethylornithine (DFMO), an irreversible inhibitor of ornithine decarboxylase (ODC), on regeneration of sensory axons from a local crush of the adult frog sciatic nerve. If daily injections of DFMO started at the same time as crushing and continued throughout the regeneration period (7 days) the outgrowth in vivo of new sensory axons was reduced by about 30%. If DFMO injections started 2 days after crushing, the outgrowth distance did not differ from control values. The sensory axons of a cultured frog sciatic nerve with the attached spinal ganglia start to regenerate from a local crush applied 7 days after the start of the incubation. Five days after crushing the outgrowth distance was 4.5 mm. At the end of the culturing period (7 + 5 days) both the putrescine and spermidine concentrations in the ganglia had increased about 2.5 times, whereas the spermine concentration remained constant. The presence of 10 mM DFMO throughout the culturing period, 7 + 5 days, almost depleted putrescine and prevented the spermidine increase in the ganglia without affecting the regeneration distance. In the nerve putrescine was only reduced by 55% and the other polyamines were unaffected by DFMO. The results show that DFMO influences the early onset of regeneration in vivo. The in vitro results indicate that this is not due to a close mechanistic relationship between the perikaryonal ODC/polyamine system and nerve regeneration. The question of whether polyamines are of local importance for regeneration of the frog sciatic nerve cannot be answered by the present results.

Nerve regeneration and serum levels of insulin-like growth factor-I in rats with streptozotocin-induced insulin deficiency

Peripheral nerve regeneration was studied in female Sprague-Dawley rats with streptozotocin-induced insulin deficiency. Nerve regeneration was provoked by a crush lesion on the sciatic nerve 21 days after the streptozotocin injection. The regeneration was assessed by a pinch test at different time-points after injury. The rate of regeneration in insulin-deficient animals, 2.5 mm/day, was significantly lower than in control animals, 2.9 mm/day (P less than 0.05). There was no difference in the initial delay, i.e. the period before regeneration attains a constant velocity. One group of insulin-deficient rats was treated with insulin during the regeneration period by means of implanted osmotic mini-pumps. This treatment prevented the decrease in regeneration. After 6 days the sciatic nerves of insulin-deficient rats had regenerated 12.3 +/- 0.3 mm (mean +/- S.E.M.), while the corresponding value for insulin-treated rats was 15.7 +/- 0.6 mm. (P less than 0.01). The streptozotocin-treated rats were found to have a 39% reduction in the serum level of insulin-like growth factor-I (IGF-I) compared to control rats (0.33 +/- 0.02 micrograms/ml and 0.54 +/- 0.02 micrograms/ml respectively, P less than 0.001). Insulin treatment during the regeneration period completely restored the IGF-I level back to normal.

Effect of histamine on the development of astroglial cells in culture

The effect of histamine on different aspects of the growth of astrocytes was studied using primary cultures derived either from forebrain or from cerebellum of the rat. The influence on general growth and differentiation was monitored in terms of the activities of ornithine decarboxylase and glutamine synthetase enzymes, whereas [3H]thymidine incorporation into DNA was used as a specific index of cell proliferation. Treatment with 500 nM histamine of cells grown for 6 days in vitro, caused a time-dependent significant increase in ornithine decarboxylase activity of astrocytes from both sources. The maximum increase was observed at 4 h after histamine treatment, at that time the elevation in ornithine decarboxylase activity being about 80% and 300% over control values in the forebrain and the cerebellar astrocytes, respectively. Under similar experimental conditions, addition of histamine (500 nM) to medium resulted in a significant increase in [3H]thymidine incorporation into DNA in both types of cultures: in comparison with control, the elevation was about 45% at 48 h in forebrain astrocytes and at 24 h in cerebellar astrocytes. On the other hand, the specific activity of glutamine synthetase in cerebellar astrocytes was markedly enhanced (about 100%) by treatment with histamine (500 nM) for 4 days, but forebrain astrocytes were little affected. Addition of histamine to the culture medium produced no significant alteration in the activity of lactate dehydrogenase and protein content of either type of astroglial cells. The present findings, which support our earlier proposal that the biochemical properties of astrocytes differ between various brain regions, provide direct evidence for the involvement of histamine in the regulation of growth and development of astrocytes.

Treatment with polyamines can prevent monosodium glutamate neurotoxicity in the rat retina

It has been previously shown that treatment of newborn rats with the polyamines putrescine, spermidine and spermine can rescue sympathetic neurons from naturally occurring cell death and from induced death after axotomy or immunosympathectomy. The present study demonstrates that polyamine treatment can also prevent the neurodegenerative effects in the retina and the loss of body weight caused by monosodium glutamate. The findings indicate that polyamine treatment may have a rather general beneficial effect on neuron survival.

Polyamines induce precocious development in rats. Possible interaction with growth factors

The study reports the effects of daily subcutaneous injections of the biogenic polyamines putrescine, spermidine and spermine (10 mg/kg each) given for a short postnatal period, on growth and development of rats. Polyamine treatment, while only slightly enhancing normal body weight gain, prevented the weight loss caused by surgical injury of 5-day-old animals. The treatment resulted in earlier eyelid and ear opening and in earlier maturation of righting and gripping responses. Increased number of neurons in the superior cervical ganglion that is caused by polyamine treatment, could not be prevented by castration of newborn rats, thus excluding the testes as a site through which polyamines may exert their action. An apparent increase in immunohistochemically detectable nerve growth factor was evident in iris and submaxillary salivary gland of polyamine-treated animals, but no change in epidermal growth factor immunohistochemistry was detected in the salivary gland. We conclude: (1) treatment of newborn rats with polyamines can accelerate somatic and neurobehavioral development; (2) further studies are required in order to verify and quantitate the effects of polyamines on growth factors, and (3) the results imply that exogenous polyamines may exert their growth-promoting effects on a number of cell types when these cells experience periods of polyamine dependence.

Axotomy-induced ornithine decarboxylase activity in the mouse dorsal root ganglion is inhibited by the vinca alkaloids

Vinca alkaloids were used to study the role of retrograde axon transport (RT) in activating neuron perikaryal repair response to nerve transection. Mouse lumbar dorsal root ganglia (DRG) (L4-L6) were excised 48 hours after unilateral transection of the sciatic nerve and ornithine decarboxylase (ODC) activity determined. ODC activity in DRG ipsilateral to nerve transection was increased 10-20 fold over contralateral values. Typical ODC activities in ipsilateral and contralateral DRG samples were 6.18 +/- 1.4 and 0.31 +/- 0.09 pmol 14CO2 released/h/3DRG, respectively. Systemic administration of single doses of either vincristine (1 mg/kg) or vinblastine (5 mg/kg) immediately prior to axotomy attenuated ODC induction in ipsilateral DRG by 39% and 47%, respectively. A direct inhibition of ODC activity in the DRG appears unlikely since only high concentrations of vinblastine (0.5-1.0 mM) were able to inhibit ODC activity in vitro. We suggest vinca alkaloids inhibit ODC induction as a consequence of disrupting retrograde axonal transport. Interruption of this intracellular communication mechanism may be etiologically linked to the the distal axon degeneration which follows repetitive exposure to vinca alkaloids and other agents that induce toxic axonal neuropathy.

Plasticity of primary afferent acid phosphatase expression following rerouting of afferents from muscle to skin in the adult rat

We have examined the possibility that reinnervation of a new peripheral target by primary afferent neurones can alter the histochemical properties of those afferents in the adult rat. The hindlimb sural and gastrocnemius nerves largely supply skin and muscle, respectively. In adult animals these nerves were cut and rejoined to either their own distal stumps (self-anastomosis) or that of the other nerve (cross-anastomosis) and allowed to regenerate for 12-16 weeks to reinnervate an appropriate or inappropriate target. Fluoride-resistant acid phosphatase (FRAP) is a chemical marker found in many unmyelinated afferents. We have determined the FRAP expression in normal and regrown nerves and examined its distribution in the dorsal horn of animals with self- and cross-anastomosed nerves. While normal and self-anastomosed sural nerves stained heavily for FRAP, gastrocnemius nerves showed either no staining or only the occasional fibre. Cross-anastomosed gastrocnemius nerves, now innervating the skin, showed a significant increase in staining, in some cases approaching the levels normally seen in sural nerves. Conversely, cross-anastomosed sural nerves (innervating muscle) showed decreased FRAP staining. In the normal dorsal horn the terminals of FRAP containing afferents form a thin band extending throughout the mediolateral extent of lamina II (Devor and Claman: Brain Res. 190:17-28, '80). One week after axotomy of the sural nerve, FRAP is depleted from its terminals and a gap appears in the normal FRAP staining pattern in the lumbar enlargement of the spinal cord. The new expression of FRAP in cross-anastomosed nerves was also seen in their terminals in the dorsal horn.(ABSTRACT TRUNCATED AT 250 WORDS)

Retrograde changes in transglutaminase activity after peripheral nerve injuries

It has been previously demonstrated that transglutaminase activity in rat superior cervical ganglion is rapidly and transiently increased minutes after nerve injury. The present series of experiments sought to determine: (1) whether or not similar changes are expressed by other peripheral neuronal systems, and (2) if injury-induced changes in the enzyme activity can be detected along the injured nerve, and if so do they occur in axons or in non-neuronal cells. In the nodose ganglion transglutaminase activity increased (approximately 40%) 48 h after the vagus nerve was crushed 25 mm from the ganglion. In the vagus nerve the activity was transiently increased (approximately 100%) within 1 h, followed by a second increase (approximately 140%) after 3 h. This occurred only in the proximal nerve stump close to the injury site and not in the section of nerve closer to the ganglion. Comparable enzyme activity was found in unoperated vagus nerve and in distal stumps of previously ligated vagus nerves. In dorsal root ganglia no changes were found for up to 24 h after the sciatic nerve was crushed 40 mm from the ganglion. In the facial nucleus a transient increase was observed after the facial nerve was crushed about 14 mm distally with a peak (approximately 300) at 3 days and a decline within 14 days. A second lesion of the facial nerve made 12 days following a conditioning lesion led to a rebound of enzyme activity in the facial nucleus.(ABSTRACT TRUNCATED AT 250 WORDS)

Progressive deficits in retrograde axon transport precede degeneration of motor axons in acrylamide neuropathy

Single injection of acrylamide (1.3 mmol/kg, i.p.) inhibited retrograde axon transport of [125I]tetanus toxin in hen sensory and motor axons. Retrograde axon transport deficits appeared within hours of dosing with acrylamide. The inhibitory effect of acrylamide on retrograde axon transport was transient since transport deficits were not detectable 35 h after dosing. Acrylamide impaired the retrograde movement but not the uptake of [125I]tetanus toxin in the axon. Multiple doses of acrylamide (0.42 mmol/kg, i.p.) induced progressive clinical signs of acrylamide neuropathy that correlated with increasing deficits in retrograde axon transport of [125I]tetanus toxin to ventral spinal cord. Deficits were also observed in sensory neurons but were not statistically significant. Accumulated decrements in retrograde axon transport may be the underlying cause of degeneration of motor axons in acrylamide neuropathy in fowl.

Early polyamine treatment enhances survival of sympathetic neurons after postnatal axonal injury or immunosympathectomy

We have recently demonstrated that following injury of their axon, sympathetic neurons of the rat superior cervical ganglion become dependent on polyamine synthesis for their survival. In addition we have observed that the treatment of newborn rats with biogenic polyamines can prevent the naturally occurring reduction in the number of neurons in the ganglion. In the present study groups of newborn rats were subjected to either postganglionic nerve crush (axotomy) or to treatment with antiserum to nerve growth factor (immunosympathectomy), two treatments which result in a massive loss of neurons in the ganglion. Daily injections of the polyamines putrescine, spermidine and spermine (10 mg/kg each), for 7 days after the operation to the axotomized group, and for 9 days starting with the first antiserum injection to the immunosympathectomized group, attenuated the nerve cell loss. The polyamine treatment also attenuated the reduction in the activity of the neurotransmitter-synthesizing enzyme tyrosine hydroxylase observed after both axotomy and immunosympathectomy in the ganglion. These results further indicate that polyamines are important for the survival of sympathetic neurons and, while their mechanism of action is unknown, an interaction with nerve growth factor regulation cannot be excluded. In the iris, the reduction observed in [3H]norepinephrine uptake after the two noxious treatments was unproportionately small when compared to the large drop in the number of parent neurons in the ganglion. This suggests that compensatory mechanisms exist which act to adjust the number of functional axon terminals per neuron so that the number of terminals innervating the target remains relatively constant.

A new method for studies of the effects of locally applied drugs on peripheral nerve regeneration in vivo

An in vivo technique which allows local application of drugs to the regenerating rat sciatic nerve for several days is presented. The sciatic nerve was transected at the knee level and a crush lesion was made proximal to the transection. The crush lesion and the nerve segment distal to it was enclosed in a chamber made of silicone tubing (STC). The STC was perfused via a catheter connected to a miniosmotic pump. Regeneration was evaluated with the 'pinch-test' at 3, 4 and 6 days after the enclosure of the nerve. The rate of regeneration in the STC-surrounded nerve segment was 3.5 mm/day after an initial delay of 1.6 days which are values similar to those in uncovered nerves with crush lesions. Perfusion of the STC with either vinblastine, cycloheximide, actinomycin D or mitomycin C inhibited regeneration. The effects were confined to the STC-covered region. Leakage of drugs was too small to affect the nerve outside the chamber. The results suggest that regeneration requires proliferation and protein synthesis in the cells surrounding the growing axons. This technique could be useful for studies of the local effects of various drugs, specific antibodies, potential growth factors etc. on regeneration of peripheral nerves.

Impaired induction of ornithine decarboxylase activity following nerve crush in the streptozotocin-diabetic rat

Ornithine decarboxylase activity was measured in the dorsal root ganglia from crushed and uncrushed contralateral sciatic nerve of control and streptozotocin-diabetic rats. A further group of diabetic rats was treated with insulin throughout the experiment. Ornithine decarboxylase activity in ganglia from uncrushed nerves was the same in diabetic and non-diabetic rats. A significant (greater than 4-fold) increase in mean levels of ornithine decarboxylase activity 72 h after crush injury was found in ganglia from crushed nerves in non-diabetic but not in diabetic rats. The enzyme activity in ganglia from diabetic rats treated with insulin resembled that in non-diabetic rats. Twenty-four hours after crush injury, ornithine decarboxylase activity in ganglia from crushed nerves was higher in non-diabetic than in diabetic animals. This may be responsible for the delayed and defective nerve regeneration known to occur in peripheral nerve of the streptozotocin-diabetic rat.