Kainate-induced seizure activity stimulates the polyamine interconversion pathway in rat brain

Spermine oxidase inhibitor, MDL 72527, reduced neovascularization, vascular permeability, and acrolein-conjugated proteins in a mouse model of ischemic retinopathy

Disruptions in polyamine metabolism have been identified as contributing factors to various central nervous system disorders. Our laboratory has previously highlighted the crucial role of polyamine oxidation in retinal disease models, specifically noting elevated levels of spermine oxidase (SMOX) in inner retinal neurons. Our prior research demonstrated that inhibiting SMOX with MDL 72527 protected against vascular injury and microglial activation induced by hyperoxia in the retina. However, the effects of SMOX inhibition on retinal neovascularization and vascular permeability, along with the underlying molecular mechanisms of vascular protection, remain incompletely understood. In this study, we utilized the oxygen-induced retinopathy (OIR) model to explore the impact of SMOX inhibition on retinal neovascularization, vascular permeability, and the molecular mechanisms underlying MDL 72527-mediated vasoprotection in the OIR retina. Our findings indicate that inhibiting SMOX with MDL 72527 mitigated vaso-obliteration and neovascularization in the OIR retina. Additionally, it reduced OIR-induced vascular permeability and Claudin-5 expression, suppressed acrolein-conjugated protein levels, and downregulated P38/ERK1/2/STAT3 signaling. Furthermore, our results revealed that treatment with BSA-Acrolein conjugates significantly decreased the viability of human retinal endothelial cells (HRECs) and activated P38 signaling. These observations contribute valuable insights into the potential therapeutic benefits of SMOX inhibition by MDL 72527 in ischemic retinopathy.

Transgenic Mouse Overexpressing Spermine Oxidase in Cerebrocortical Neurons: Astrocyte Dysfunction and Susceptibility to Epileptic Seizures

Polyamines are organic polycations ubiquitously present in living cells. Polyamines are involved in many cellular processes, and their content in mammalian cells is tightly controlled. Among their function, these molecules modulate the activity of several ion channels. Spermine oxidase, specifically oxidized spermine, is a neuromodulator of several types of ion channel and ionotropic glutamate receptors, and its deregulated activity has been linked to several brain pathologies, including epilepsy. The Dach-SMOX mouse line was generated using a Cre/loxP-based recombination approach to study the complex and critical functions carried out by spermine oxidase and spermine in the mammalian brain. This mouse genetic model overexpresses spermine oxidase in the neocortex and is a chronic model of excitotoxic/oxidative injury and neuron vulnerability to oxidative stress and excitotoxic, since its phenotype revealed to be more susceptible to different acute oxidative insults. In this review, the molecular mechanisms underlined the Dach-SMOX phenotype, linked to reactive astrocytosis, neuron loss, chronic oxidative and excitotoxic stress, and susceptibility to seizures have been discussed in detail. The Dach-SMOX mouse model overexpressing SMOX may help in shedding lights on the susceptibility to epileptic seizures, possibly helping to understand the mechanisms underlying epileptogenesis in vulnerable individuals and contributing to provide new molecular mechanism targets to search for novel antiepileptic drugs.

Regional and temporal alterations of ODC/polyamine system during ALS-like neurodegenerative motor syndrome in G93A transgenic mice

Natural polyamines (putrescine, spermidine and spermine) are ubiquitous molecules known to regulate a number of physiological processes and suspected to play a role also in various pathological conditions. Changes in polyamine levels and in their biosynthetic enzymes have been described for some neurodegenerative diseases but the available data are incomplete and somewhat contradictory. We report here alterations of the key enzyme of the polyamine pathway, ornithine decarboxylase (ODC) catalytic activity and polyamine levels in different CNS areas from SOD1 G39A transgenic mice, an animal model for amyotrophic lateral sclerosis (ALS). ODC catalytic activity, was found significantly increased both in the cervical and lumbar spinal cord and, to a lesser extent in the brain stem of transgenic mice at a symptomatic stage of the disease (125-day-old mice), while no differences were present at a pre-symptomatic stage (55-day-old mice). In parallel with the increase of ODC activity putrescine levels were several times increased in both cervical and lumbar spinal cord and in the brain stem of 125-day-old SOD1 G39A mice. Higher order polyamines were not increased except for a significant increase of spermidine in the cervical spinal cord. The present data demonstrate considerable alterations of the ODC/polyamine system in a reliable animal model of ASL, consistent with their role in neurodegeneration and in particular in motor neuron diseases.

Putrescine as a marker of the effects of 2-chloropropionic acid in the rat brain

The neurotoxin 2-chloropropionic acid (2CPA, 750 mg/kg, per os) induces ataxia in rats causing neuropathological changes (necrosis and edema) localized mainly in the cerebellum (CB). It has been described that putrescine (PUT) is a good marker of severe brain damage. We measured the concentration of PUT (by HPLC) in ataxic rat brains 3 days after 2CPA dosing. PUT was 9-fold higher than normal values in CB, 5-fold higher in midbrain (MB) and medulla oblongata + pons (MO) and 3-fold higher in the remaining areas studied. Treatment with glycerol, a reducer of brain edema, lowered the concentration of PUT only in CB, MB and MO. Histological damage was found in CB and the spinal trigeminal nucleus (located in the pontomedullar brainstem). We suggest that PUT can act as a marker of both neuronal necrosis and brain edema.

Genetic approaches to the cellular functions of polyamines in mammals

The polyamines putrescine, spermidine and spermine are organic cations shown to participate in a bewildering number of cellular reactions, yet their exact functions in intermediary metabolism and specific interactions with cellular components remain largely elusive. Pharmacological interventions have demonstrated convincingly that a steady supply of these compounds is a prerequisite for cell proliferation to occur. The last decade has witnessed the appearance of a substantial number of studies, in which genetic engineering of polyamine metabolism in transgenic rodents has been employed to unravel their cellular functions. Transgenic activation of polyamine biosynthesis through an overexpression of their biosynthetic enzymes has assigned specific roles for these compounds in spermatogenesis, skin physiology, promotion of tumorigenesis and organ hypertrophy as well as neuronal protection. Transgenic activation of polyamine catabolism not only profoundly disturbs polyamine homeostasis in most tissues, but also creates a complex phenotype affecting skin, female fertility, fat depots, pancreatic integrity and regenerative growth. Transgenic expression of ornithine decarboxylase antizyme has suggested that this unique protein may act as a general tumor suppressor. Homozygous deficiency of the key biosynthetic enzymes of the polyamines, ornithine and S-adenosylmethionine decarboxylase, as achieved through targeted disruption of their genes, is not compatible with murine embryogenesis. Finally, the first reports of human diseases apparently caused by mutations or rearrangements of the genes involved in polyamine metabolism have appeared.

Polyamine levels in brain and plasma after acute restraint or water-immersion restraint stress in mice

To investigate the relationship between polyamines and stress, we measured polyamine levels in the frontal cortex, hippocampus, hypothalamus, and plasma of mice after acute restraint or water-immersion restraint stress. In all parts of the brain, putrescine levels were elevated (139-157% of the control) 24 h after water-immersion restraint stress. In the case of restraint, however, elevation of the putrescine level (130% of the control) was detected only in the frontal cortex. Spermidine and spermine levels were unchanged or slightly reduced (80-85% of the control) in the brain 6 and 24 h after water-immersion restraint stress. There was no change in plasma polyamine levels at any time subsequent to the stress. Pretreatment with diazepam (5 mg/kg, i.p.) completely blocked the stress-induced putrescine increases. These results indicate that the magnitude of the putrescine increase is dependent upon the intensity of the stressor, and suggest that polyamine metabolism is linked to psychological stress.

Effects of delayed administration of (-)-epigallocatechin gallate, a green tea polyphenol on the changes in polyamine levels and neuronal damage after transient forebrain ischemia in gerbils

(-)-Epigallocatechin gallate has a potent antioxidant property and can reduce free radical-induced lipid peroxidation as a green tea polyphenol. In previous study, systemic administration of (-)-epigallocatechin gallate immediately after ischemia has been shown to inhibit the hippocampal neuronal damage in the gerbil model of global ischemia. Polyamines are thought to be important in the generation of brain edema and neuronal cell damage associated with various types of excitatory neurotoxicity. We examined the effects of delayed administration of (-)-epigallocatechin gallate on the changes in polyamine levels and neuronal damage after transient global ischemia in gerbils. To produce transient global ischemia, both common carotid arteries were occluded for 3 min with micro-clips. The gerbils were treated with (-)-epigallocatechin gallate (50 mg/kg, i.p.) at 1 or 3 h after ischemia. The polyamines; putrescine, spermidine, and spermine levels were examined using high performance liquid chromatography in the cerebral cortex and hippocampus 24 h after ischemia. Putrescine levels in the cerebral cortex and hippocampus were increased significantly after ischemia and the delayed administrations of (-)-epigallocatechin gallate (1 or 3 h after ischemia) attenuated the increases. Only minor changes were noted in the spermidine and spermine levels after ischemia. In histology, neuronal injuries in the hippocampal CA1 regions were evaluated quantitatively 5 days after ischemia. (-)-Epigallocatechin gallate administered 1 h or 3 after ischemia significantly reduced hippocampal neuronal damage. The present results show that the delayed administrations of (-)-epigallocatechin gallate inhibit the transient global ischemia-induced increase of putrescine levels in the cerebral cortex and hippocampus. (-)-Epigallocatechin gallate is neuroprotective against neuronal damage even when administered up to 3 h after global ischemia. These findings suggest that (-)-epigallocatechin gallate may be promising in the acute treatment of stroke.

Extracellular putrescine content after acute excitotoxic brain damage in the rat

We examined the effects of the local infusion of kainic acid (KA), by reverse dialysis in the rat striatum, on the concentration of polyamines in the extracellular striatal compartment and in tissue. KA infusion markedly increased (3-fold) extracellular putrescine (PUT) concentration, which reached its maximum at the end of the dialysis experiments (6 h). Tissue PUT concentration was also increased (2-fold) in the striatum perfused with KA but not in the contralateral side. Extracellular spermidine (SD) concentration but not tissue SD concentration was affected by KA. The increase in PUT was accompanied by histological damage around the probe and by an increase in ornithine decarboxylase content, as assessed by immunohistochemistry. These results indicate that in the first stages of the excitotoxic lesion, there is an increase in the extracellular concentrations of PUT and SD.

Visually driven modulation of glutamatergic synaptic transmission is mediated by the regulation of intracellular polyamines

Ca2+-permeable AMPARs are inwardly rectifying due to block by intracellular polyamines. Neuronal activity regulates polyamine synthesis, yet whether this affects Ca2+-AMPAR-mediated synaptic transmission is unknown. We test whether 4 hr of increased visual stimulation regulates glutamatergic retino-tectal synapses in Xenopus tadpoles. Tectal neurons containing Ca2+-AMPARs form a gradient along the rostro-caudal developmental axis. These neurons had inwardly rectifying AMPAR-mediated EPSCs. Four hours of visual stimulation or addition of intracellular spermine increased rectification in immature neurons. Polyamine synthesis inhibitors blocked the effect of visual stimulation, suggesting that visual activity regulates AMPARs via the polyamine synthesis pathway. This modulation resulted in changes in the integrative properties of tectal neurons. Regulation of polyamine synthesis by physiological stimuli is a novel form of modulation of synaptic transmission important for understanding the short-term effects of enhanced sensory experience during development.

The polyamine oxidase inactivator MDL 72527

Polyamine oxidase is a FAD-dependent amine oxidase, which is constitutively expressed in nearly all tissues of the vertebrate organism. In 1985, N1,N4-bis(2,3-butadienyl)-1,4-butanediamine (MDL 72527) was designed as a selective enzyme-activated irreversible inhibitor of polyamine oxidase (EC 1.5.3.11). It inactivates, at micromolar concentration and time-dependently, the enzyme in cells, as well as in all organs of experimental animals, without inhibiting other enzymes of polyamine metabolism. MDL 72527 served during nearly two decades as a unique tool in the elucidation of the physiological roles of polyamine oxidase. The compound has anticancer and contragestational effects, and it improves the anticancer effect of the ornithine decarboxylase inactivator (D,L)-2-(difluoromethyl)ornithine (DFMO). Profound depletion of the polyamine pools of tumour cells and effects on different components of the immune defence system are responsible for the anticancer effects of MDL 72527/DFMO combinations. Recently a direct cytotoxic effect of MDL 72527 at concentrations above those required for polyamine oxidase inactivation was observed. The induction of apoptosis by MDL 72527 was ascribed to its lysosomotropic properties. Therapeutic potentials of the apoptotic effect of MDL 72527 need to be explored. Polyamine oxidase is the last enzyme of the polyamine interconversion pathway that awaits the detailed elucidation of its structure and regulation. MDL 72527 should be useful as a lead in the development of inactivators which are selective for the isoforms of polyamine oxidase. Isozyme-selective inhibitors will give more profound insights into and reveal a diversity of specific functions of polyamine oxidase.

Regulation of SSAT expression by synaptic activity

Neuronal activity is a requirement for the plasticity and normal development of the central nervous system. We have used differential cloning techniques to identify an immediate-early gene (IEG) that is rapidly induced in neurons by activity in both adult and developmental models of plasticity. Here we describe the key regulatory enzyme of polyamine catabolism, spermidine/spermine N1-acetyltransferase (SSAT), as a neuronal IEG. In the rat brain, kainate-induced seizures result in a 5.5-fold increase in the amount of SSAT mRNA above basal levels and the enzymatic activity is increased twofold. Expression of SSAT mRNA is rapidly and transiently upregulated in the cerebral cortex and hippocampus by seizure-induced neuronal activation. In hippocampal neurons, SSAT expression is dynamically responsive to synaptic activity in the long-term potentiation (LTP) paradigm. In developing brain, region-specific expression of SSAT mRNA is first detected at postnatal day 9 (P9) and subsequently increases through days P15, P20, before reaching maximal level in adult animals. This dynamic transcriptional and translational control suggests that SSAT may play a role in activity-dependent neuronal plasticity and development.

Oxidation of polyamines and brain injury

Several amine oxidases are involved in the metabolism of the natural polyamines putrescine, spermidine, and spermine, and play a role in the regulation of intracellular concentrations, and the elimination of these amines. Since the products of the amine oxidase-catalyzed reactions -- hydrogen peroxide and aminoaldehydes -- are cytotoxic, oxidative degradations of the polyamines have been considered as a cause of apoptotic cell death, among other things in brain injury. Since a generally accepted, unambiguous nomenclature for amine oxidases is missing, considerable confusion exists with regard to the polyamine oxidizing enzymes. Consequently the role of the different amine oxidases in physiological and pathological processes is frequently misunderstood. In the present overview the reactions, which are catalyzed by the different polyamine-oxidizing enzymes are summarized, and their potential role in brain damage is discussed.

Overexpression of spermidine/spermine N-acetyltransferase in transgenic mice protects the animals from kainate-induced toxicity

We recently generated a transgenic mouse line with activated polyamine catabolism through overexpression of spermidine/spermine N1-acetyltransferase (SSAT). A detailed analysis of brain polyamine concentrations indicated that all brain regions of these animals showed distinct signs of activated polyamine catabolism, e.g. overaccumulation of putrescine (three- to 17-fold), appearance of N1-acetylspermidine and decreases in spermidine concentrations. In situ hybridization analyses revealed a marked overexpression of SSAT-specific mRNA all over the brain tissue of the transgenic animals. The transgenic animals appeared to tolerate subcutaneous injections of high-dose kainate substantially better as their overall mortality was less than 50% of that of their syngenic littermates. We used the expression of glial fibrillary acidic protein (GFAP) as a marker of brain injury in response to kainate. In situ hybridization analysis with GFAP oligonucleotide up to 7 days after the administration of sublethal kainate doses showed reduced GFAP expression in transgenic animals in comparison with their non-transgenic littermates. This difference was especially striking in the cerebral cortex of the transgenic mice where the exposure to kainate hardly induced GFAP expression. The treatment with kainate likewise resulted in loss of the hippocampal (CA3) neurons in non-transgenic but not transgenic animals. These results support our earlier findings indicating that elevated concentrations of brain putrescine, irrespective whether derived from an overexpression of ornithine decarboxylase, or as shown here, from an overexpression of SSAT, play in all likelihood a neuroprotective role in brain injury.

Pentylenetetrazol-induced kindling stimulates the polyamine interconversion pathway in rat brain

The levels of polyamines, N-acetylpolyamines, and GABA in the cerebral cortex and brainstem of rat brain after completion of pentylenetetrazol (PTZ)-induced kindling were investigated. Pretreatment with the polyamine oxidase inhibitor MDL72527 caused an accumulation of N1-acetylspermidine and N1-acetylspermine in normal rats. After a kindling seizure, the levels of N-acetylpolyamines were elevated, particularly in the cerebral cortex, indicating activation of polyamine interconversion. The levels of putrescine and GABA were lower in kindled rats pretreated with MDL72527. In addition, pretreatment with MDL72527 enhanced the seizure susceptibility to PTZ in normal rats. These results suggest that the polyamine interconversion pathway is involved in brain excitability, probably through the regulation of putrescine and GABA levels.

Simultaneous assay of ornithine decarboxylase and polyamines after central nervous system injury in gerbil and rat

Ornithine decarboxylase (ODC) is considered the rate-limiting enzyme in polyamine biosynthesis. An increase in putrescine (a natural polyamine) synthesis after central nervous system (CNS) injury appears to be involved in blood-brain barrier dysfunction, development of vasogenic edema and neuronal death. An improved method is described to determine the ODC activity as well as polyamine levels from the same brain tissue. The polyamine results showed no significant differences from data obtained with the conventional assay. The advantages of this method are to: (1) minimize the number of animals needed for the study, and (2) eliminate any internal inconsistencies resulting from use of two independent groups of animals for ODC and polyamine measurements. Using this method, ODC activities and polyamine levels were measured in cortices and hippocampi from global transient ischemia of gerbils and traumatic brain injury (TBI) of rats.

Brain lesions and delayed water maze learning deficits after intracerebroventricular spermine

The effects of spermine on the acquisition and retention of spatial learning in the Morris water maze were studied. Spermine 25 and 125 nmol i.c.v. did not alter the ability of rats to find a hidden platform in the water maze when administered before training over 5 days. However, the inhibitory effect of the benzodiazepine, diazepam (3 mg/kg i.p., 30 min prior to training), on path length to target was markedly potentiated by the higher dose of spermine, consistent with spermine acting as a functional antagonist at the NMDA receptor. This drug combination did not affect performance on visible platform trials. Administration of doses of 125 and 250 nmol (but not 62.5 nmol) of spermine i.c.v. in the week prior to training (daily for 5 days) dose-dependently inhibited subsequent learning of a platform position in the absence of drug. These higher doses of spermine produced neuronal loss and increased [3H]PK11195 binding indicating microglial activation predominantly in the hippocampus and to a lesser extent in the striatum, septum, thalamus and amygdala. Spermine 125 nmol i.c.v. (daily for 7 days) also abolished retention of a previously learned platform position when administered in an interval between training and retention testing. The inhibitory effects of spermine 125 nmol i.c.v. (daily for 7 days) on subsequent spatial learning were not antagonised by concomitant administration of 30 nmol dizocilpine. These results demonstrate that spermine produces a delayed neurotoxic effect in particular neuronal populations in the brain that selectively impair spatial learning and recall.

Long-term effects of status epilepticus induced by kainic acid on hippocampal polyamines

Putrescine has been suggested to have an inhibitory effect on the excitability of the central nervous system. In the present study we found that 2 and 3 weeks after status epilepticus induced by kainic acid, rats had increased concentrations of putrescine (3- and 1.7-fold, respectively) and spermidine (1.6- and 1.4-fold, respectively) in the hippocampus. These animals exhibited a higher susceptibility to pentylentetrazol than the saline group. In addition, several hours after the pentylentetrazol injection, the concentration of putrescine and spermidine increased again in the brain and also in the plasma. In conclusion, increased hippocampal putrescine and spermidine concentrations seem to be linked with a lower threshold of excitability.

Changes in brain putrescine concentration associated with nonconvulsant behavioral patterns induced by systemic N-methyl-D-aspartate injection

The relationship between the behavioral effects and motor activity induced by N-methyl-D-aspartate (NMDA) (150 mg/kg, ip) and brain polyamine concentration was studied in male Wistar rats. Motor activity was evaluated by an automated subtraction analysis system to measure the duration and vigor of any kind of movement. The behavioral modifications exhibited by the nonconvulsant NMDA-treated rats were evaluated according to the composition and sequence of behavioral components as: hypoactivity (pattern A), partially stereotyped activity (pattern B), and generalized stereotyped activity (pattern C). The concentration of polyamines in the frontal cortex and hippocampus was measured 8 and 24 h after drug injection. A relationship was found between the concentration of putrescine in both regions and the motor activity. In addition, the concentrations of putrescine also correlated with the vigor of the movements performed. Moreover, the putrescine concentration in the frontal cortex and hippocampus paralleled the behavioral patterns. The histological examination of the frontocortical and hippocampal areas did not reveal any evidence of damage. In conclusion, partially or generalized stereotyped activity elicited by systemic NMDA administration induces an increase in putrescine in the brain not linked to histological damage.

Spermidine/spermine N1-acetyltransferase mRNA levels show marked and region-specific changes in the early phase after transient forebrain ischemia

Considerable evidence points to an involvement of natural polyamines (putrescine, spermidine and spermine) in trophic regulation of brain tissue. Spermidine/spermine N1-acetyltransferase is the key enzyme in the interconversion pathway which leads to the formation of spermidine and putrescine from spermine and spermidine, respectively. In the present paper we have studied using in situ hybridization histochemistry the levels of spermidine/spermine N1-acetyltransferase mRNA in the rat central nervous system after transient forebrain ischemia. In the first hours after the insult, a modest increase in spermidine/spermine N1-acetyltransferase mRNA levels was observed in ependymal cells and other non-neuronal cells of all telencephalic and diencephalic regions. In addition, major increases in spermidine/spermine N1-acetyltransferase mRNA levels were observed in regions selectively vulnerable to the ischemic insult, such as striatum, hippocampus and cerebral cortex, during the first day post-reperfusion. The time course and extent of labelling increase were subregion- and cell-specific. At the cellular level, the labelling appeared markedly increased in neurons (8-10 fold in ventromedial striatum and CA1 region) and, to a lesser extent, in non-neuronal cells. The increase in SSAT mRNA levels was not directly related to cell degeneration, as it was detected in both some vulnerable and some resistant cell populations. However, the peak increase of SSAT labelling was precocious in resistant neurons (such as those of ventromedial striatum and dentate gyrus granular layer) and delayed or very limited in vulnerable neurons (such as those of CA1 pyramidal layer and dorsolateral striatum). The increase in spermidine/spermine N1-acetyltransferase may contribute to the increase in putrescine and decrease in spermidine levels observed after ischemia and gives further support to the notion that polyamine metabolism in the early phase after lesion is oriented towards putrescine production. This phenomenon could be relevant in determining the prevalence of neurotrophic vs. neurotoxic effects of polyamines.

Regional and cellular distribution of spermidine/spermine N1-acetyltransferase (SSAT) mRNA in the rat central nervous system

Spermidine/spermine N1-acetyltransferase (SSAT) is the key enzyme responsible for polyamine interconversion. SSAT mRNA (visualized by in situ hybridization histochemistry) was shown to have a wide but heterogeneous distribution in the central nervous system (CNS) at both regional and cellular levels. The highest labelling was observed in hippocampus (pyramidal and polymorph neurons) and olfactory bulb. Present data suggest that polyamine metabolism in the CNS is not homogeneous but rather that the preferential production of a polyamine species is region- and cell type-specific.

Intracellular polyamines mediate inward rectification of Ca(2+)-permeable alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors

alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors that lack the glutamate receptor GluR2 subunit are Ca(2+)-permeable and exhibit inwardly rectifying current responses to kainate and AMPA. A proportion of cultured rat hippocampal neurons show similar Ca(2+)-permeable inwardly rectifying AMPA receptor currents. Inward rectification in these neurons was lost with intracellular dialysis and was not present in excised outside-out patches but was maintained in perforated-patch whole-cell recordings, suggesting that a diffusible cytoplasmic factor may be responsible for rectification. Inclusion of the naturally occurring polyamines spermine and spermidine in the recording pipette prevented loss of rectification in both whole-cell and excised-patch recordings; Mg2+ and putrescine were without effect. Inward rectification of Ca(2+)-permeable AMPA receptors may reflect voltage-dependent channel block by intracellular polyamines.

Effect of kainate-induced seizure activity on the polyamine interconversion pathway in juvenile rat brain

The activity of the polyamine interconversion pathway was investigated in the hippocampus and piriform cortex after systemic KA administration in juvenile rats. Pretreatment of 7-day-old rats with the polyamine oxidase inhibitor, MDL 72527, induced a similar accumulation of N-acetylspermidine and N-acetylspermine in control and kainate-treated animals. The results indicate that KA-induced seizure activity has no effect on the polyamine interconversion pathway in developing rat brain.