3-Nitropropionic acid (3-NPA) produces hypothermia and inhibits histochemical labeling of succinate dehydrogenase (SDH) in rat brain

Biocontrol ability of Bacillus velezensis T9 against Apiospora arundinis causing Apiospora mold on sugarcane

Sugarcane (Saccharum officinarum L.) may be infected with Apiospora, which can produce the toxin 3-nitropropionic acid (3-NPA) during improper transportation and storage. The consumption of sugarcane that contains 3-NPA can lead to food poisoning. Therefore, this study sought to explore a novel biocontrol agent to prevent and control Apiospora mold. Bacteria were isolated from the soil of healthy sugarcane and identified as Bacillus velezensis T9 through colony morphological, physiological and biochemical characterization and molecular identification. The inhibitory effect of B. velezensis T9 on Apiospora mold on sugarcane was analyzed. Assays of the cell suspension of strain T9 and its cell-free supernatant showed that T9 had significant in vitro antifungal activities against Apiospora arundinis and thus, would be a likely antagonist. Scanning electron microscopy and transmission electron microscopy showed that treatment with T9 significantly distorted the A. arundinis mycelia, perforated the membrane, contracted the vesicles, and decomposed most organelles into irregular fragments. A re-isolation experiment demonstrates the ability of T9 to colonize the sugarcane stems and survive in them. This strain can produce volatile organic compounds (VOCs) that are remarkably strong inhibitors, and it can also form biofilms. Additionally, the cell-free supernatant significantly reduced the ability of A. arundinis to produce 3-NPA and completely inhibited its production at 10%. Therefore, strain T9 is effective at controlling A. arundinis and has the potential for further development as a fungal prevention agent for agricultural products.

3-Nitropropionic Acid and Similar Nitrotoxins

3-Nitropropionic acid as well as 3-nitro-1-propanol and its β-D-glucopyranoside (miserotoxin) are the plant and fungal toxins reported to interrupt mitochondrial electron transport resulting in cellular energy deficit. These nitrotoxins induce neurological degeneration in ruminants and humans. 3-Nitropropionic acid-intoxicated rats serve as the animal model for Huntington’s disease.

Nicotinamide reverses behavioral impairments and provides neuroprotection in 3-nitropropionic acid induced animal model ofHuntington's disease: implication of oxidative stress- poly(ADP- ribose) polymerase pathway

Huntington's disease (HD) is characterized by cognitive and psychiatric impairment caused by neuronal degeneration in the brain. Several studies have supported the hypothesis that oxidative stress is the main pathogenic factor in HD. The current study aims to determine the possible neuroprotective effects of nicotinamide on 3-nitropropionic acid (3-NP) induced HD. Male Wistar albino rats were divided into six groups. Group I was the vehicle-treated control, group II received 3-NP (20 mg/kg, intraperitoneally (i.p.) for 4 days, group III received nicotinamide (500 mg/kg, i.p.). The remaining groups received a combination of 3-NP plus nicotinamide 100, 300 or 500 mg/kg, i.p. respectively for 8 days. Afterward, the motor function and hind paw activity in the limb withdrawal were tested; rats were then euthanized for biochemical and histopathological analyses. Treatment of rats with 3-NP altered the motor function, elevated oxidative stress and caused significant histopathological changes in the brain. The treatment of rats with nicotinamide (100, 300 and 500 mg/kg) improved the motor function tested by locomotor activity test, movement analysis, and limb withdrawal test, which was associated with decreased oxidative stress markers (malondialdehyde, nitrites) and increased antioxidant enzyme (glutathione) levels. In addition, nicotinamide treatment decreased lactate dehydrogenase and prevented neuronal death in the striatal region. Our study, therefore, concludes that antioxidant drugs like nicotinamide might slow progression of clinical HD and may improve the motor functions in HD patients. To the best of our knowledge, this study is the first to explore the neuroprotective effects of nicotinamide on 3-NP-induced HD.

Thermoregulatory disorders in Huntington disease

Huntington disease (HD) is a paradigmatic autosomal-dominant adult-onset neurodegenerative disease. Since the identification of an abnormal expansion of a trinucleotide repeat tract in the huntingtin gene as the underlying genetic defect, a broad range of transgenic animal models of the disease has become available and these have helped to unravel the relevant molecular pathways in unprecedented detail. Of note, some of the most informative of these models develop thermoregulatory defects such as hypothermia, problems with adaptive thermogenesis, and an altered circadian temperature rhythm. Both central, e.g., in the hypothalamus and peripheral, i.e., the brown adipose tissue and skeletal muscle, problems contribute to the phenotype. Importantly, these structures and pathways are also affected in human HD. Yet, currently the evidence for bona fide thermodysregulation in human HD patients remains anecdotal. This may be due to a lack of reliable tools for monitoring body temperature in an outpatient setting. Regardless, study of the temperature phenotype has contributed to the identification of unexpected molecular targets, such as the PGC-1α pathway.

NGF promotes mitochondrial function by activating PGC-1α in TM4 Sertoli cells

Nerve growth factor (NGF), which is required for the survival and differentiation of the nervous system, has been proved to play important roles in male reproductive physiology. Several studies have focused on the roles of NGF in the testes. However, no study has reported on the mechanism of paracrine and autocrine actions of NGF in Sertoli cells. This study showed that NGF stimulated mitochondrial activity and biogenesis in TM4 Sertoli cells. Moreover, our results demonstrated that peroxisome proliferator-activated receptor-gamma coactivator-1α is a possible downstream key target of the NGF signalling pathway. In a 3-nitropropionic acid cell model, NGF treatment attenuated mitochondrial activity defect and depolarisation. This NGF-triggered signalling may help in discovering new therapeutic targets for certain male infertility disorders.

Beyond muscles: The untapped potential of creatine

Creatine is widely used by both elite and recreational athletes as an ergogenic aid to enhance anaerobic exercise performance. Older individuals also use creatine to prevent sarcopenia and, accordingly, may have therapeutic benefits for muscle wasting diseases. Although the effect of creatine on the musculoskeletal system has been extensively studied, less attention has been paid to its potential effects on other physiological systems. Because there is a significant pool of creatine in the brain, the utility of creatine supplementation has been examined in vitro as well as in vivo in both animal models of neurological disorders and in humans. While the data are preliminary, there is evidence to suggest that individuals with certain neurological conditions may benefit from exogenous creatine supplementation if treatment protocols can be optimized. A small number of studies that have examined the impact of creatine on the immune system have shown an alteration in soluble mediator production and the expression of molecules involved in recognizing infections, specifically toll-like receptors. Future investigations evaluating the total impact of creatine supplementation are required to better understand the benefits and risks of creatine use, particularly since there is increasing evidence that creatine may have a regulatory impact on the immune system.

Effects of mid-respiratory chain inhibition on mitochondrial function in vitro and in vivo

Schematic showing the toxicological and adaptive effects of drug-induced respiratory chain inhibition in vivo; also highlighting unanticipated differences from observations made in vitro (in red).

Relating the in vitro mitochondrial effects of drug candidates to likely in vivo outcomes remains challenging. Better understanding of this relationship, alongside improved methods to assess mitochondrial dysfunction in vivo, would both guide safer drug candidate selection and better support discovery programmes targeting mitochondria for pharmacological intervention. The aim of this study was to profile the in vivo effects of a compound with suspected complex III electron transport chain (ETC) inhibitory activity (GSK932121A) at doses associated with clinical signs, and relate findings back to in vitro data with the same compound. Control liver mitochondria or HepG2 cells were treated in vitro with GSK932121A to assess mitochondrial effects on both calcium retention capacity (CRC) and oxygen consumption rate (OCR) respectively. The same assessments were then performed on liver mitochondria isolated from Crl:CD(SD) rats, 5 hours following intraperitoneal (IP) administration of GSK932121A. Lactate/pyruvate assessment, hepatic microscopy, blood gas analysis, glutathione profiling and transcriptomics were used to characterise the acute toxicity. In vivo, GSK932121A caused hypothermia, increased levels of hepatocellular oxidative stress and a metabolic shift in energy production, resulting in an increased lactate/pyruvate ratio, liver steatosis and glycogen depletion, together with gene expression changes indicative of a fasted state. As would be expected of an ETC inhibitor, GSK932121A reduced the CRC of liver mitochondria isolated from naive control animals and the OCR of HepG2 cells when treated directly in vitro. In contrast, mitochondria isolated from animals treated with GSK932121A in vivo unexpectedly showed an increase in CRC and basal OCR. Whilst seemingly contradictory, these differences likely reflect an adapted state in vivo resulting from the initial insult in combination with compensatory changes made by the tissue to maintain energy production. Only the initial, unconfounded, response is observable in vitro. These findings improve current understanding of the toxicological and molecular consequences of ETC inhibition. Furthermore, this work highlights key differences in the way that mitochondrial perturbation is manifest in vivo versus in vitro in terms of functional endpoints and helps guide endpoint selection for future studies with potential mitochondrial toxicants or drugs designed to modulate mitochondrial function for therapeutic benefit.

Korean red ginseng ameliorates acute 3-nitropropionic acid-induced cochlear damage in mice

3-Nitropropionic acid (3-NP), a mitochondrial toxin, has been reported to induce an acute cochlear damage. Korean red ginseng (KRG) is known to have protective effects from some types of hearing loss. This study aimed to observe the protective effect of KRG in an ototoxic animal model using 3-NP intratympanic injection. BALB/c mice were classified into 5 groups (n=15) and dose-dependent toxic effects after intratympanic injection with 3-NP (300-5000 mM) on the left ear were investigated to determine the appropriate toxicity level of 3-NP. For observation of the protective effects of KRG, 23 mice were grouped into 3-NP (500 mM, n=12) and KRG+3-NP groups (300 mg/kg KRG for 7 days before 500 mM 3-NP administration, n=11). Auditory brain response (ABR) and cochlear morphological evaluations were performed before and after drug administration. The ABR thresholds in the 800-5000 mM groups exceeded the maximum recording limit at 16 and 32 kHz 1 day after 3-NP administration. The ABR threshold in the 500 mM 3-NP+KRG group was significantly lower than that in the 500 mM 3-NP group from post 1 week to 1 month. The mean type II fibrocyte counts significantly differed between the control and 3-NP groups and between the 3-NP and 3-NP+KRG groups. Spiral ganglion cell degeneration in the 3-NP group was more severe than that in the 3-NP+KRG group. This animal model exhibited a dose-dependent hearing loss with histological changes. KRG administration ameliorated the deterioration of hearing by 3-NP.

Acetyl-L-Carnitine Modulates TP53 and IL10 Gene Expression Induced by 3-NPA Evoked Toxicity in PC12 Cells

The neurotoxicity induced by the mitochondrial inhibitor 3-nitropropionic acid (3-NPA) is associated with a decrease of ATP synthesis and an increase of free radical production which can lead to apoptosis or necrosis. We have used the PC12, neuron-like rat pheochromocytoma cell line, to study further the mechanism of 3-NPA-evoked neurotoxicity and the effects of acetyl-L-carnitine (ALC) which has neuroprotective actions against various types of mitochondrial inhibitors.

Cultured PC 12 cells were exposed to a low dose of 3-NPA 50 (microM) in the presence or absence of 5 mM ALC. The dose of 3-NPA was sub toxic and no changes in pro-apoptotic Bax or anti-apoptotic Bcl-2 gene expression were observed. We followed specific genetic markers to look for changes evoked by 3-NPA toxicity and also changes associated with neuroprotection exerted by the ALC treatment, using RT-PCR arrays (delta-delta method). 3-NPA exposure evoked a decrease in expression of the Tp53 gene. This down regulation was prevented by pretreatment of the cells with ALC. The Tp53 gene responds to cellular stresses and the effects seen here are possibly associated with the 3-NPA evoked changes in mitochondrial metabolism. Other genes associated with stress and apoptosis, Parp-1, Bcl-2, and Bax were not affected by 3-NPA or ALC. The decrease of inflammatory response Il-10 gene expression due to 3-NPA was further lowered by presence of ALC. Other inflammation related genes, Il1rn, Nr3c1 and Cxcr4 were not affected. Interestingly, the glutamate transporter slc17a7, carnitine-acylcarnitine translocase Slc25a20 and heat shock proteins genes, Hsp27, Hmox1 (Hsp32, HO1) as well as Hspa 1a (Hsp 70) increased only when both ALC and small dose of 3-NPA were present. The alterations in gene expression detected in this study suggest role of several intracellular pathways in the neurotoxicity of 3-NPA and the neuroprotection against 3-NPA-induced neurotoxicity by ALC.

Co-regulation of dopamine D1 receptor and uncoupling protein-2 expression in 3-nitropropionic acid-induced neurotoxicity: neuroprotective role of L-carnitine

This study tested the hypothesis that the expression of uncoupling proteins (UCPs) and dopamine (DA) system genes is responsive to 3-nitropropionic acid (3-NPA) neurotoxic effects and to the neuroprotective effects of the mitochondrial enhancer, L-carnitine (LC), in the rat striatum. Inactivation of mitochondrial succinate dehydrogenase (SDH) by 3-NPA results in hypoxic brain damage. Hypoxic conditions induce uncoupling protein-2 (UCP-2). An increase in UCP-2 expression may lead to a decrease in production of reactive oxygen species (ROS) associated with energy depletion. However, this adaptive response can also lead to a reduction of ATP that may further contribute to energy deficit and mitochondrial dysfunction. Here, male adult Sprague-Dawley rats (n=5/group) were injected either with saline or 3-NPA at 30 mg/kg, s.c. alone or 30 min after pre-treatment with LC (100mg/kg, i.p.). Rectal temperature was monitored before treatment and 4h following 3-NPA administration. Animals were sacrificed 4h post-treatment. Total RNA was isolated from the striatum and transcripts of UCP-2, UCP-4 and UCP-5 genes, as well as genes related to dopamine metabolism, such as DA D(1) and D(2) receptors, tyrosine hydroxylase (TH), monoamine oxidase-B (MAO-B), and vesicular monoamine transporter-2 (VMAT-2), were measured using real-time reverse transcription polymerase chain reaction (RT-PCR). While core temperature decreased significantly in 3-NPA-treated rats, LC significantly inhibited the hypothermic effect of 3-NPA (p<0.05). 3-NPA caused a significant increase in UCP-2 and DA D(1) receptor gene expression in the striatum and both effects were attenuated by pre-treatment with LC. Since LC maintains the ATP/ADP ratio and was previously shown to be neuroprotective against 3-NPA toxicity, the modulation of UCP-2 expression by LC suggests that LC counteracts energy dissipation and thus prevents the negative effects of ATP decline on DA neurotransmission.

Effects of L-Carnitine Pretreatment in Methamphetamine and 3-Nitropropionic Acid-Induced Neurotoxicity

Adult, male Sprague-Dawley rats were injected with 3-ni-tropropionic acid (3-NPA) at 30 mg/kg or methamphetamine (METH) at 20 mg/kg alone or following pretreatment with L-cartnitine (LC) at 100 mg/kg. Rectal temperature was measured before and 4 h following treatment. Animals were sacrificed at 4 h posttreatment. Monoamine neurotransmitters, dopamine (DA) and serotonin (5-HT), and their metabolites were analyzed in the striatum using high-performance liquid chromatography method coupled with electrochemical detection (HPLC/ED). Transcripts of several genes related to DA metabolism were quantified using real time reverse transciption polymerase chain reaction (RT-PCR). Core temperature decreased significantly after 3-NPA acid and increased in METH-treated rats (P < 0.05). Temperature change at 4 h exhibited a significant LC effect for 3-NPA, preventing hypothermia (P < 0.05) and no effect for METH. Concentration of DA and 5-HT, and their metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), and 5-hydroxyindoleacetic acid (5-HIAA), increased significantly in 3-NPA and decreased in METH-treated rats. An increase in DOPAC/DA turnover and serotonin observed after 3-NPA was abolished in LC-/3-NPA-treated rats. In both 3-NPA- and METH-treated rats, LC prevented an increase in DA receptor D(1) gene expression. It appears that carnitine effect preventing hypothermia after 3-NPA treatments may be related not only to its mitochondriotropic actions but also to inhibitory effect on the DA and 5-HT systems activated after the exposure to 3-NPA. The same effect observed at the transcriptional level, at least for the DA receptor D(1), may account for protection against METH toxicity.

Differential effects of sublethal ischemia and chemical preconditioning with 3-nitropropionic acid on protein expression in gerbil hippocampus

Pretreatment with a low dose of 3-nitropropionic acid (3-NPA) has been shown to induce ischemic tolerance in the gerbil hippocampus. It is well known that sublethal (2-min) ischemia also induces ischemic tolerance. To investigate the acquisition of ischemic tolerance with 3-NPA, we examined the protein expression after 3-NPA treatment in comparison with sublethal ischemia. Immunohistochemical studies revealed intense expression of Bcl-2 and Bcl-xL in the hippocampal CA1 area after 3-NPA treatment. Furthermore, the time course of the expression of Bcl-xL showed a similar pattern to the acquisition of ischemic tolerance by 3-NPA treatment. The induction of Bcl-xL occurred in the hippocampal CA1 area at 24 h after 3-NPA treatment, and significant induction was observed at 48 h. Western blot analysis of hippocampus harvested 48 h after the pretreatment, showed that the expression of Bcl-2 and Bcl-xL was significantly increased by either 3-NPA treatment or 2-min ischemia. However, PMCA1 and HSP70 protein expression increased only in the sublethal ischemia treated group. The difference between 3-NPA treated group and control group was not statistically significant. These results suggest that Bcl-2 and Bcl-xL are essential for acquisition of ischemic tolerance, while HSP70 and PMCA1 play important roles in the enhancement of ischemic tolerance.

Acute effects of pulsed microwaves and 3-nitropropionic acid on neuronal ultrastructure in the rat caudate-putamen

Ultrastructure of the medium sized "spiny" neuron in rat dorsal-lateral caudate-putamen was assessed after administration of 3-nitropropionic acid (3-NP) and exposure to pulsed microwaves. Sprague-Dawley male rats were given two daily intraperitoneal doses of 0 or 10 mg/kg 3-NP and 1.5 h after each dose were exposed to microwave radiation at a whole body averaged specific absorption rate (SAR) of 0 (sham exposure), 0.6, or 6 W/kg for 30 min. Microwave exposure consisted of 1.25 GHz radiation delivered as 5.9 micros pulses with repetition frequency 10 Hz. Tissue samples taken 2-3 h after the second sham or microwave exposure showed no injury with light microscope methods. Blinded qualitative assessment of ultrastructure of randomly selected neurons from the same samples did reveal differences. Subsequent detailed, quantitative measurements showed that, when followed by sham exposure, administration of 3-NP significantly increased endoplasmic reticulum (ER) intracisternal width, ER area density, and nuclear envelope thickness. Microwave exposure at 6 W/kg alone also significantly increased these measures. Exposure of 3-NP treated animals at 6 W/kg significantly increased effects of 3-NP on ultrastructure. Although exposure at 0.6 W/kg alone did not affect ultrastructure measures, exposure of 3-NP treated animals at 0.6 W/kg reduced the effects of 3-NP. We concluded that 3-NP changed neuronal ultrastructure and that the microwave exposures used here changed neuronal ultrastructure in ways that depended on microwave SAR and neuron metabolic status. The apparent cancellation of 3-NP induced changes by exposure to pulsed microwaves at 0.6 W/kg indicated the possibility that such exposure can protect against the effects of mitochondrial toxins on the nervous system.

Neuroprotective effect of l-carnitine in the 3-nitropropionic acid (3-NPA)-evoked neurotoxicity in rats

A plant and fungal toxin, 3-NPA, acts as an inhibitor of mitochondrial function via irreversible inactivation of the mitochondrial inner membrane enzyme, succinate dehydrogenase (SDH). Inhibition of SDH disturbs electron transport and leads to cellular energy deficits and neuronal injury. We have shown that pretreatment with l-carnitine, while not significantly attenuating SDH inhibition, prevented hypothermia and oxidative stress-associated increased activity of free radical-scavenging enzymes. Here, a neurohistological method was applied to examine the effect of carnitine pretreatment against 3-NPA-induced neurotoxicity. Twenty adult male Sprague-Dawley rats were randomly divided into two groups (n = 10/group). Rats in the first group were injected twice with 3-NPA at 30 mg/kg s.c., 2 days apart, and the second group of animals received l-carnitine pretreatment at 100 mg/kg 30-40 min before 3-NPA administration. Rats in both groups were perfused 7 days later and their brains harvested. Degenerating neurons were identified and localized via the fluorescent marker Fluoro-Jade B. In the three animals that survived 3-NPA dosing, one exhibited no pathology, one exhibited moderate unilateral damage to the striatum, and the third exhibited extensive bilateral neuronal degeneration in multiple forebrain regions. In the seven surviving animals that received l-carnitine prior to 3-NPA insult, six exhibited no lesions, while one exhibited a modest unilateral lesion in the striatum. It appears that l-carnitine is protective against 3-NPA-induced toxicity, as reflected by both reduced mortality and significantly reduced neuronal degeneration.

3-nitropropionic acid inhibition of succinate dehydrogenase (complex II) activity in cultured Chinese hamster ovary cells: antagonism by L-carnitine

3-Nitropropionic acid (3-NPA) is an inhibitor of the mitochondrial enzyme succinate dehydrogenase (SDH, a part of complex II) that links the tricarboxylic acid (TCA) cycle to the respiratory electron transport chain. 3-NPA inactivates SDH by covalently and irreversibly binding to its active site. We previously examined the effects of 3-NPA on the histochemical activity of SDH in vivo, by using the reduction of a yellow tetrazolium dye (nitro blue tetrazolium) to a blue formazan as an indicator. In studies of cultured cells, the related dye methylthiazoletetrazolium (MTT) has commonly been used as an indicator of the presence and number of viable cells; that is cells that are capable of producing energy via the TCA cycle. Here we observed that doses of 3-NPA as low as 10(-8) M inhibited formazan production in an in vitro model system using CHO cells. This effect was antagonized by l-carnitine, which greatly increased the production of formazan, indicating a considerable improvement in energy production by the cultured cells. CHO cells appear to be a convenient model for the evaluation of therapeutic compounds that may modulate cellular bioenergetics.

Biomarkers of 3-nitropropionic acid (3-NPA)-induced mitochondrial dysfunction as indicators of neuroprotection

In humans or animals, symptoms of mitochondrial energy dysfunction may be produced by mutations or inborn errors of the necessary enzymes, as well as by enzyme inhibitors or uncouplers of the oxidative phosphorylation process. 3-Nitropropionic acid (3-NPA) is a toxin that is sometimes produced on moldy crops (sugarcane, peanuts, etc.) in amounts sufficient to cause severe neuromuscular disorders when consumed by humans. In vitro, 3-NPA irreversibly inactivates SDH, a Complex II respiratory enzyme important for mitochondrial energy production. We have been studying biomarkers of 3-NPA exposure in the expectation that such markers may be useful in the screening process to identify neuroprotective agents against neurotoxicity produced by mitochondrial energy dysfunction. Animals were sacrificed at various times after 3-NPA exposure for histochemical visualization of SDH activity and measurement of immediate postmortem rectal temperature. 3-NPA-treated rats experienced progressive hypothermia that reached a loss of 3 degrees C or more in core body temperature by three hours after dosing. The optical density of the SDH stain in brain was reduced, following a similar time course, most prominently in the cerebellum and least sharply in the thalamus. Some rats were given injections of L-carnitine (an enhancer of fatty acid transport) either alone, or as a pretreatment prior to a dose of 3-NPA. Although L-carnitine deficiency by itself can produce mitochondrial dysfunction, pretreatment with L-carnitine was of limited efficacy at overcoming the effects of 3-NPA on either body temperature or quantitative SDH histochemistry. Body temperature and SDH histochemistry may be useful biomarkers for evaluating the efficacy of neuroprotective agents against lower doses of 3-NPA, against other pharmacological models of mitochondrial dysfunction, or even against genetic mitochondrial diseases.

Chemical preconditioning with 3-nitropropionic acid in hearts: role of mitochondrial K(ATP) channel

We investigated the cardioprotective effect of 3-nitropropionic acid (3-NPA), an inhibitior of mitochondrial succinate dehydrogenase, and we wanted to show whether this protection is mediated by of opening mitochondrial ATP-sensitive potassium (K(ATP)) channels. Adult rabbits were treated with either 3-NPA (3 mg/kg iv) or saline (n = 6 rabbits/group). After 30 min (for early phase) or 24 h (for late phase) of the treatment, the animals were subjected to 30 min of ischemia and 3 h of reperfusion (ischemia-reperfusion). 5-Hydroxydecanoate (5-HD, 5 mg/kg iv),the mitochondrial K(ATP) channel blocker, was administered 10 min before ischemia-reperfusion in the saline- and 3-NPA-treated rabbits. 3-NPA caused a decrease in the infarct size from 27.8 +/- 4.2% in the saline group to 16.5 +/- 1.0% in the 3-NPA-treated rabbits during early phase and from 30.4 +/- 4.2% in the saline group to 17.6 +/- 1.05 in the 3-NPA group during delayed phase (P < 0.05, % of risk area). The anti-infarct effect of 3-NPA was blocked by 5-HD as shown by an increase in infarct size to 33 +/- 2.7% (early phase) and 31 +/- 2.4% (delayed phase) (P < 0.05 vs. 3-NPA groups). 5-HD had no proischemic effect in control animals. Also, 3-NPA had no effect on systemic hemodynamics. We conclude that 3-NPA induces long-lasting anti-ischemic effects via opening of mitochondrial K(ATP) channels.

Effects of acute systemic 3-nitropropionic acid administration on rat activity and acoustic startle

Spontaneous activity, acoustic startle, and prepulse inhibition (PPI) of acoustic startle were measured in male Sprague-Dawley rats 3-5 h after 0, 10, 15, or 20 mg/kg i.p. 3-nitropropionic acid (3-NP), a mitochondrial toxin. Mean activity was significantly influenced by the 3-NP dose due to decreased activity for 20 mg/kg. Mean startle amplitude was not significantly affected by the 3-NP dose. Means of PPI for prepulses 6 and 12 dBA above background were smaller than means for respective 0 mg/kg doses, but the main effect of 3-NP dose did not reach statistical significance in ANOVA. The changes in measured exploratory-type activity and, possibly, in startle PPI parallel the occurrence of clinical signs exhibited at 3-5 h after 3-NP injection. Neural processing involved in these quantitative behavioral endpoints seems to be affected as energy stores are depleted and degenerative processes are beginning.