Modulation of the behavioral and neurochemical effects of psychostimulants by kappa-opioid receptor systems

The repeated, intermittent use of cocaine and other drugs of abuse produces profound and often long-lasting alterations in behavior and brain chemistry. It has been suggested that these consequences of drug use play a critical role in drug craving and relapse to addiction. This article reviews the effects of psychostimulant administration on dopaminergic and excitatory amino acid neurotransmission in brain regions comprising the brain's motive circuit and provides evidence that the activation of endogenous kappa-opioid receptor systems in these regions opposes the behavioral and neurochemical consequences of repeated drug use. The role of this opioid system in mediating alterations in mood and affect that occur during abstinence from repeated psychostimulant use are also discussed.

Fishing for lymphoid genes

Thymic organogenesis and T-cell lymphopoiesis are crucial interdependent processes that establish a functional vertebrate immune system. The current understanding of vertebrate thymic development during embryogenesis remains incomplete and would benefit from novel approaches. The zebrafish Danio rerio is a powerful developmental and genetic system for the dissection of early events in the ontogeny of the immune system. Forward genetic screens have uncovered genes involved in hematopoiesis, and specific screens are being designed to examine the genes that regulate T-cell development and the origin of the thymus. Studies of the zebrafish should improve our understanding of lymphoid development in vertebrates.

Expression of immunoglobulin heavy chain transcripts (VH-families, IgM, and IgD) in head kidney and spleen of the Atlantic cod (Gadus morhua L.)

Expression of the immunoglobulin (Ig) heavy chain transcripts in spleen and head kidney of the Atlantic cod (Gadus morhua L.) was investigated using in situ hybridization (ISH) and northern blotting. Specific detection of plasma cells was done with a probe for secretory IgM transcripts (mu 4). The plasma cells were often clustered close to blood vessels. Cells expressing surface IgM and IgD transcripts were detected using ISH with tyramide signal amplification (TSA). The positive cells were more abundant than plasma cells, had a lymphocyte-like morphology, and were evenly distributed throughout the tissues. This suggests that cod IgD mainly is expressed as a B-cell receptor akin to IgD in mammals. The VH-III family dominated the repertoire within the plasma cells, in agreement with data from cDNA cloning. Immunization with hapten-carrier antigen did not induce a systemic antibody response, and neither was any change in the clustering or distribution pattern of plasma cells within the tissues seen. A few clusters of plasma cells expressed only the rare VH-I and VH-II families, suggesting an ongoing clonal expansion and differentiation in these regions independently of immunization.

Kappa-opioid receptor activation modifies dopamine uptake in the nucleus accumbens and opposes the effects of cocaine

Coadministration of kappa-opioid receptor agonists (kappa-agonists) with cocaine prevents alterations in dialysate dopamine (DA) concentration in the nucleus accumbens (Acb) that occur during abstinence from repeated cocaine treatment. Quantitative microdialysis was used to determine the mechanism producing these effects. Rats were injected with cocaine (20 mg/kg, i.p.), or saline, and the selective kappa-agonist U-69593 (0.32 mg/kg, s.c.), or vehicle, once daily for 5 d. Extracellular DA concentration (DA(ext)) and extraction fraction (E(d)), an indirect measure of DA uptake, were determined 3 d later. Repeated cocaine treatment increased E(d), whereas repeated U-69593 treatment decreased E(d), relative to controls. Coadministration of both drugs yielded intermediate E(d) values not different from controls. In vitro DA uptake assays confirmed that repeated U-69593 treatment produces a dose-related, region-specific decrease in DA uptake and showed that acute U-69593 administration increases DA uptake in a nor-binaltorphimine reversible manner. Repeated U-69593 also led to a decrease in [(125)I]RTI-55 binding to the DA transporter (DAT), but did not decrease total DAT protein. These results demonstrate that kappa-opioid receptor activation modulates DA uptake in the Acb in a manner opposite to that of cocaine: repeated U-69593 administration decreases the basal rate of DA uptake, and acute U-69593 administration transiently increases DA uptake. kappa-agonist treatment also alters DAT function. The action of kappa-agonists on DA uptake or DAT binding, or both, may be the mechanism(s) mediating the previously reported "cocaine-antagonist" effect of kappa-opioid receptor agonists.

Hereditary spherocytosis in zebrafish riesling illustrates evolution of erythroid beta-spectrin structure, and function in red cell morphogenesis and membrane stability

Spectrins are key cytoskeleton proteins with roles in membrane integrity, cell morphology, organelle transport and cell polarity of varied cell types during development. Defects in erythroid spectrins in humans result in congenital hemolytic anemias with altered red cell morphology. Although well characterized in mammals and invertebrates, analysis of the structure and function of non-mammalian vertebrate spectrins has been lacking. The zebrafish riesling (ris) suffers from profound anemia, where the developing red cells fail to assume terminally differentiated erythroid morphology. Using comparative genomics, erythroid beta-spectrin (sptb) was identified as the gene mutated in ris. Zebrafish Sptb shares 62.3% overall identity with the human ortholog and phylogenetic comparisons suggest intragenic duplication and divergence during evolution. Unlike the human and murine orthologs, the pleckstrin homology domain of zebrafish Sptb is not removed in red cells by alternative splicing. In addition, apoptosis and abnormal microtubule marginal band aggregation contribute to hemolysis of mutant erythrocytes, which are features not present in mammalian red cells with sptb defects. This study presents the first genetic characterization of a non-mammalian vertebrate sptb and demonstrates novel features of red cell hemolysis in non-mammalian red cells. Further, we propose that the distinct mammalian erythroid morphology may have evolved from specific modifications of Sptb structure and function.

Glycine(B) receptor antagonists and partial agonists prevent memory deficits in inhibitory avoidance learning

Activation of N-methyl-d-aspartate (NMDA) receptors has been hypothesized to mediate certain forms of learning and memory. This hypothesis is based on the ability of competitive and uncompetitive NMDA receptor antagonists to disrupt learning. We investigated the effects of glycine site antagonists and partial agonists on deficits of acquisition (learning) and consolidation (memory) in a single trial inhibitory avoidance learning paradigm. Posttraining administration of either hypoxia (exposure to 7% oxygen) or the convulsant drug pentylenetetrazole (PTZ) (45 mg/kg) to mice impaired consolidation without producing neuronal cell death. Pretreatment with the competitive glycine antagonist 7-chlorokynurenic acid (7KYN) and the glycine partial agonists 1-aminocyclopropanecarboxylic acid (ACPC) and (+)HA-966 prevented memory deficits induced by hypoxia and PTZ, but did not affect scopolamine-induced learning impairment. In addition, ACPC prevented consolidation deficits evoked by a nonexcitotoxic concentration of l-trans-pyrrolidine-2, 4-dicarboxylate, a competitive inhibitor of glutamate transport that increases extracellular levels of glutamate. Moreover, (+)HA-966, 7KYN, and ACPC facilitated both acquisition and consolidation of inhibitory avoidance training, an effect that was dose-dependent and reversed by glycine. These results indicate that memory deficits induced by both hypoxia and PTZ involve NMDA receptor activation. Furthermore, the present findings demonstrate that glycine site antagonists and partial agonists prevent memory deficits of inhibitory avoidance learning by affecting consolidation, but not acquisition processes.

Effect of melatonin treatment on 24-h variations in responses to mitogens and lymphocyte subset populations in rat submaxillary lymph nodes

Wistar male rats were injected s.c. with melatonin (30 microg) or vehicle, 1 h before lights off, for 11 days. Ten days after beginning melatonin treatment, rats received Freund's complete adjuvant or its vehicle s.c., and after 2 days, they were sacrificed at six different time intervals throughout a 24-h cycle. The mitogenic effect of lipopolysaccharide (LPS) and concanavalin A (Con A), the activity of ornithine decarboxylase (ODC) and the relative size of lymphocyte subset populations were measured in submaxillary lymph nodes. In control rats, the mitogenic effects of LPS and Con A and ODC activity peaked during the afternoon. Injection of Freund's adjuvant induced a 10-h shift in the diurnal rhythm of the mitogenic effect of LPS to attain maximal values at night. Melatonin pretreatment blunted the daily variations in the mitogenic activity of Con A or LPS and, when given to Freund's adjuvant-injected rats, augmented mesor and amplitude of diurnal rhythm in ODC activity. Maxima in B cell number occurred at night whereas those of T and B-T cell number occurred during the afternoon. During the early phase of immunization tested, the number of B cells augmented and the amplitude of its diurnal rhythmicity increased both after immunization and following melatonin pretreatment. Maxima of 24-h rhythms in CD4+ and CD4+/CD8+ cell populations occurred during the afternoon while those of CD8+ cells occurred at late night. Melatonin significantly augmented CD4+ cell number and decreased CD8+ cell number; it therefore augmented the CD4+:CD8+ ratio. The results suggest that pretreatment with a pharmacological dose of melatonin exerts immunomodulating effects at an early, preclinical, phase of Freund's adjuvant-induced arthritis in rats.

Choline release and inhibition of phosphatidylcholine synthesis precede excitotoxic neuronal death but not neurotoxicity induced by serum deprivation

N-Methyl-d-aspartate (NMDA) receptor overactivation has been proposed to induce excitotoxic neuronal death by enhancing membrane phospholipid degradation. In previous studies, we have shown that NMDA releases choline and reduces membrane phosphatidylcholine in vivo. We now observed that glutamate and NMDA induce choline release in primary neuronal cortical cell cultures. This effect is Ca(2+)-dependent and is blocked by MK-801 ((+)-5-methyl-10, 11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine hydrogen maleate). In cortical neurons, the NMDA receptor-mediated choline release precedes excitotoxic cell death but not neuronal death induced by either osmotic lysis or serum deprivation. Glutamate, at concentrations that release arachidonic acid, does not release choline in cerebellar granule cells, unless these cells are rendered susceptible to excitotoxic death by energy deprivation. The NMDA-evoked release of choline is not mediated by phospholipases A(2) or C. Moreover, NMDA does not activate phospholipase D in cortical cells. However, NMDA inhibits incorporation of [methyl-(3)H]choline into both membrane phosphatidylcholine and sphingomyelin. These results show that the increase in extracellular choline induced by NMDA receptor activation is directly related with excitotoxic cell death and indicate that choline release is an early event of the excitotoxic process produced by inhibition of phosphatidylcholine synthesis and not by activation of membrane phospholipid degradation.

Role of high-affinity choline uptake on extracellular choline and acetylcholine evoked by NMDA

Previous studies have shown that NMDA evokes a calcium-dependent and region-specific increase in extracellular choline that is associated with a reduction of membrane phosphatidylcholine and precedes neuronal cell death. We investigated, using in vivo microdialysis, the contribution of high-affinity choline uptake on the increase in extracellular choline evoked by NMDA. Dialysis was performed in the presence of Neostigmine (0.5 microM), an acetylcholinesterase inhibitor, in prefrontal cortex or hippocampus of freely moving rats. Drugs were administered through the dialysis probe. In cholinergic denervation experiments, rats were subjected to sham or AMPA-induced lesion of cholinergic nuclei at least 2 weeks before microdialysis. Excitotoxic lesion of the medial septum / ventral diagonal band nuclei reduced hippocampal choline acetyltransferase activity by 74%, [(3)H]hemicholinium-3 binding by 32%, and completely abolished potassium-evoked acetylcholine release. Despite this reduction of presynaptic cholinergic function, perfusion of NMDA (300 microM) by retrodialysis produced an increase in hippocampal extracellular choline (249 +/- 22% of basal levels) that was similar to that observed in sham controls (301 +/- 35%). Inhibition of choline uptake with hemicholinium-3 in nonlesioned rats produced a sustained increase in dialysate choline (163 +/- 8%) and reduced acetylcholine to 33 +/- 2% of basal levels, consistent with a depletion of the acetylcholine pool due to precursor deficit. Simultaneous perfusion of hemicholinium-3 and NMDA produced a synergistic increase in dialysate choline (664 +/- 95% of basal levels), indicating that part of the choline released by NMDA is taken up. In contrast, NMDA antagonized the decrease of acetylcholine produced by hemicholinium-3. These results show that NMDA-evoked choline release is not mediated by inhibition of high-affinity choline uptake and indicate that choline released by NMDA can be used to sustain acetylcholine synthesis when there is a precursor deficit secondary to uptake inhibition.

Positional cloning of zebrafish ferroportin1 identifies a conserved vertebrate iron exporter

Defects in iron absorption and utilization lead to iron deficiency and overload disorders. Adult mammals absorb iron through the duodenum, whereas embryos obtain iron through placental transport. Iron uptake from the intestinal lumen through the apical surface of polarized duodenal enterocytes is mediated by the divalent metal transporter, DMTi. A second transporter has been postulated to export iron across the basolateral surface to the circulation. Here we have used positional cloning to identify the gene responsible for the hypochromic anaemia of the zebrafish mutant weissherbst. The gene, ferroportin1, encodes a multiple-transmembrane domain protein, expressed in the yolk sac, that is a candidate for the elusive iron exporter. Zebrafish ferroportin1 is required for the transport of iron from maternally derived yolk stores to the circulation and functions as an iron exporter when expressed in Xenopus oocytes. Human Ferroportin1 is found at the basal surface of placental syncytiotrophoblasts, suggesting that it also transports iron from mother to embryo. Mammalian Ferroportin1 is expressed at the basolateral surface of duodenal enterocytes and could export cellular iron into the circulation. We propose that Ferroportin1 function may be perturbed in mammalian disorders of iron deficiency or overload.

Titanium levels in rats implanted with Ti6Al4V treated samples in the absence of wear

The effect of implantation time and implant nitriding on titanium ion concentration in several tissues of rats carrying Ti6Al4V implants was studied by means of inductively coupled plasma-mass spectroscopy (ICP-MS). Histological studies were also performed in order to check for tissue degeneration due to the Ti6Al4V implantation. The animals were divided into four groups: one received Ti6Al4V implants, the second received nitrided Ti6Al4V implants, the third group received nitrided and descaled Ti6Al4V implants and the last one was the control group. Half the animals of the implanted groups received the Ti6Al4V implant for 30 days, while the other half received the implant for 120 days. Spleen, muscle, kidney, lung, brain and bone samples were retrieved from these rats as well as the control group. Ion concentration measures did not show significant differences between control and implanted rats for the studied period of time, although histological studies showed minor differences, especially on liver tissue samples.

Clinical comparison of dexketoprofen trometamol and dipyrone in postoperative dental pain

A total of 125 outpatients with moderate to severe pain after surgical removal of one impacted third molar were randomly assigned to receive dexketoprofen trometamol 12.5 or 25 mg or dipyrone 575 mg. For first-dose assessments, patients rated their pain intensity and its relief at regular intervals. From 60 min post dose to the end of the 6-h observation period, both doses of dexketoprofen trometamol had higher pain relief scores than dipyrone: Between 3 and 6 h the differences were statistically significant. In addition, peak measures (PIDmax and PARmax) were statistically superior after both doses of dexketoprofen trometamol compared to dipyrone. The overall efficacy assessed at the end of the first-dose phase was rated as good or excellent by 90%, 83.3%, and 70% of patients receiving dexketoprofen trometamol 25 mg, dexketoprofen trometamol 12.5 mg, and dipyrone, respectively. The number of patients who required remedication during the 6-h period was significantly lower in both dexketoprofen groups. Repeated-dose data were also obtained. No significant differences were found in the efficacy after repeated doses, the number of doses taken, or the mean time elapsed between doses. The overall efficacy at the end of the repeated-dose phase was rated as good or excellent by 84.2%, 66.7%, and 70% of patients receiving dexketoprofen trometamol 25 mg, dexketoprofen trometamol 12.5 mg, and dipyrone, respectively. The frequency of adverse events was similar for all treatments and no serious adverse events were reported during the study.

[Occlusion of the right common carotid artery due to oral estrogen overdose]

INTRODUCTION

Continuous use of oral anticontraceptive agents has been related to adverse vascular changes in the form of venous or arterial thromboses and cerebrovascular accidents (CVA). In our case, we describe a CVA due to occlusion of the common carotid artery after an acute massive overdose of estrogens due to error of dosage when using Yuzpe's system or emergency post-coital therapy.

CLINICAL CASE

We describe a 26 year old woman with no previous clinical history, who smoked 20 cigarettes per day, did not take oral contraceptive pills and suffered an acute left facial-brachial-crural hemiplegia together with reduced level of consciousness. Imaging tests showed acute occlusion of the right common carotid artery. Etiological study of the patient's cerebral vascular accident was negative. The only etiopathogenic factor to be related was having taken oral contraceptive agents for three days after coitus as emergency post-coital treatment. This treatment was incorrect, since the dose of estrogens was four times that recommended.

CONCLUSIONS

The continued use of estrogens, especially at doses over 30 micrograms per day, was considered responsible for approximately 10% of CVAs in young people. The risk of cerebral vascular accident is greater when there is associated migraine and/or smoking. We describe a patient who showed that the acute use of high doses of estrogens may also cause arterial occlusion, in this case in the common carotid artery.

Region-specific and calcium-dependent increase in dialysate choline levels by NMDA

NMDA receptor-induced excitotoxicity has been hypothesized to mediate abnormal choline (Cho) metabolism that is involved in alterations in membrane permeability and cell death in certain neurodegenerative disorders. To determine whether NMDA receptor overactivation modulates choline metabolism in vivo, we investigated the effects of NMDA on interstitial choline concentrations using microdialysis. Perfusion of NMDA by retrodialysis increased dialysate choline (approximately 400%) and reduced dialysate acetylcholine (Ach) (approximately 40%). Choline levels remained increased for at least 2.5 hr, but acetylcholine returned to pretreatment values 75 min after NMDA perfusion. The NMDA-evoked increase in dialysate choline was calcium and concentration dependent and was prevented with 1 mM AP-5, a competitive NMDA antagonist, but was not altered by mepacrine, a phospholipase A2 inhibitor. NMDA increased extracellular choline levels four- to fivefold in prefrontal cortex and hippocampus, produced a slight increase in neostriatum, and did not modify dialysate choline in cerebellum. Perfusion with NMDA for 2 hr produced a delayed, but not acute, reduction in choline acetyltransferase activity in the area surrounding the dialysis probe. Consistent with a lack of acute cholinergic neurotoxicity evoked by this treatment, basal acetylcholine levels were unaltered by 2 hr of continuous NMDA perfusion. Prolonged NMDA perfusion produced a 34% decrease in phosphatidylcholine content in the lipid fraction of the tissue surrounding the dialysis probe. These results show that NMDA modulates choline metabolism, eliciting a receptor-mediated, calcium-dependent, and region-specific increase in extracellular choline from membrane phospholipids that is not mediated by phospholipase A2 and precedes delayed excitotoxic neuronal cell death.

Glycine site antagonists and partial agonists inhibit N-methyl-D-aspartate receptor-mediated [3H]arachidonic acid release in cerebellar granule cells

Activation of N-methyl-D-aspartate (NMDA) receptors is known to produce arachidonic acid release, which has been implicated in excitotoxicity. Antagonists and partial agonists at the glycine site of the NMDA receptor, despite exhibiting functional differences in electrophysiological studies, inhibit glutamate-induced neurotoxicity and ischemia-induced neurodegeneration. The objective of this study was to investigate the effects of both glycine site antagonists and partial agonists on NMDA receptor-mediated [3H]arachidonic acid (AA) release evoked by glutamate, NMDA or a competitive inhibitor of the glutamate/aspartate uptake carrier. The [3H]AA release evoked by a maximally effective concentration of glutamate (100 microM) was blocked by the glycine site antagonists 7-chlorokynurenic acid (7-CKYN) and 5,7-dichlorokynurenic acid (5,7-DCKYN) and by a low intrinsic efficacy glycine partial agonist (+)-1-hydroxy-3-aminopyrrolid-2-one [(+)-HA-966]. 1-Aminocyclopropanecarboxylic acid (ACPC), a high intrinsic efficacy glycine partial agonist, did not modify [3H]AA release evoked by 100 microM glutamate. However, ACPC blocked (in a glycine reversible manner) the [3H]AA release induced by NMDA (100 microM) with an IC50 of 131 +/- 2 microM. Furthermore, L-trans-pyrrolidine-2,4-dicarboxylate (PDC), a competitive inhibitor of the glutamate transporter, also released [3H]AA (Emax and EC50 of 127 +/- 4% and 30 +/- 1 microM, respectively). ACPC, 7-CKYN and (+/-)-2-amino-7-phosphonoheptanoic acid (AP-7), a competitive NMDA receptor antagonist, inhibited [3H]AA release evoked by PDC. These results demonstrate that both glycine site antagonists and partial agonists can inhibit NMDA receptor-mediated [3H]AA release in cerebellar granule cells, an action consistent with the neuroprotective effects of these compounds.

Body fat distribution, insulin mediated suppression of non-esterified fatty acids and plasma triglycerides in obese subjects

Triglyceride levels and free fatty acid metabolism are influenced by body fat distribution. To test whether the pattern of fat distribution in obese subjects results in distinct insulin mediated suppression of non-esterified fatty acids which could account for differences in plasma triglycerides, we studied 59 obese subjects who were classified according to waist-to-hip ratio. Non-esterified fatty acids and insulin response to a 75 g oral glucose tolerance test were higher in abdominal obesity. Total non-esterified fatty acids response, after adjustment for sex, showed a positive association with waist-to hip ratio (r = 0.292; p < 0.05). The abdominal obese group had higher fasting triglycerides (1.74+/-0.83 versus 1.11+/-0.71 mmol/L; p = 0.003) and lower glucose/insulin ratio (5.2+/-2.3 versus 7.1+/-2.4; p = 0.003). Stepwise multiple regression analysis showed that triglyceride levels are explained by fasting and 120 min non-esterified fatty acids and by glucose/insulin ratio. We conclude that abdominal obesity is associated with a higher resistance to insulin mediated suppression of non-esterified fatty acids in obese subjects. Variation of triglyceride concentrations in obesity is dependent on both fasting and 120 min non-esterified fatty acids as well as on insulin sensitivity to glucose utilization.

Monoclonal antibodies specific for porcine monocytes/macrophages: macrophage heterogeneity in the pig evidenced by the expression of surface antigens

Macrophages are widely distributed in most tissues of the body, where they play important roles in host defense and repair of tissue damage. In this report we describe the production and characterization of a panel of six monoclonal antibodies (mAb) against porcine macrophages and their use for phenotyping tissue macrophages. All mAbs were produced by immunizing mice with porcine alveolar macrophages. Three of them (2A10/11, 3B11/11 and 3F7/11) react mainly with macrophages and, at a lower extent, blood monocytes, whereas the others (1E12/11, 2C12/10 and 4E9/11) also recognize granulocytes. Antigens recognized by these antibodies could be characterized by Western blot and/or immunoprecipitation, with the exception of that one recognized by 2C12/10. By their behavior in SDS-PAGE under reducing and nonreducing conditions, all seem to be single polypeptides, whose apparent molecular weight under reducing conditions are: 1E12/11 and 3B11/11 larger than 204 kDa; 2A10/11, 150 kDa; 4E9/11, 125-170 kDa; and 3F7/11, 135 kDa. Immunohistochemical analyses of both lymphoid and non-lymphoid organs using these mAbs reveal important antigenic heterogeneity among tissue macrophages. These mAbs are, therefore, useful tools for the study of porcine macrophage maturation and differentiation and for determining their heterogeneity both in normal and pathological conditions.

Effects of NMDA-R1 antisense oligodeoxynucleotide administration: behavioral and radioligand binding studies

The effects of an antisense phosphodiester oligodeoxynucleotide (ODN) directed to the NR1 subunit of the NMDA receptor mRNA and of its corresponding sense ODN were investigated in mice. Treatment with the antisense ODN significantly increased the time mice spent in the open arms of an elevated maze while the total number of arm entries was unaltered. Furthermore, seizure latencies after the administration of an ED100 dose of NMDA (150 mg/kg) were significantly higher in antisense treated animals compared to vehicle controls. At the same time, treatment with NR1 antisense ODN significantly reduced the Bmax of [3H]CGS-19755 binding (2101 fmol/mg protein) compared to both vehicle (2787 fmol/mg protein) and sense (2832 +/- 39 fmol/mg protein) controls without any significant change in KD (33 nM). A corresponding reduction of [3H]CGP-39653 binding was also observed after treatment with NR1 antisense compared to both sense and vehicle controls. In contrast, neither antisense nor sense ODNs altered the proportion of high affinity glycine sites or the potency of glycine at either high or low affinity glycine binding sites to inhibit [3H]CGP-39653 binding. These results show that in vivo treatment with NR1 antisense ODNs to the NMDA receptor complex reduces antagonist binding at NMDA receptors and has pharmacological effects similar to those observed with some NMDA receptor antagonists. These results also suggest that treatment with antisense ODNs may provide another means to investigate allosteric modulation of receptor subtypes in vivo.

Modulation of NMDA-induced cytosolic calcium levels by ACPC in cultured cerebellar granule cells

The effect of 1-aminocyclopropanecarboxylic acid (ACPC) on the potentiation by glycine of N-methyl-D-aspartate (NMDA)-evoked increases in intracellular free calcium concentration [Ca2+]i was examined in cultured rat cerebellar granule cells. NMDA (50 microM) produced a rapid and sustained increase in [Ca2+]i from 72 +/- 3 to 205 +/- 18 nM. Addition of exogenous glycine potentiated (EC50 -2 microM) the effects of NMDA, increasing [Ca2+]i to an Emax of 323 +/- 5 nM. ACPC increased the EC50 of glycine from 2 microM (no ACPC) to 17 microM (400 microM ACPC). Concomitant with reduced potency of glycine, ACPC also inhibited the Emax of glycine to enhance NMDA-evoked cytosolic free calcium to values (224 +/- 1 nM) approaching those observed in the nominal absence of glycine. These results show that ACPC, a compound previously reported to prevent excitotoxic cell death, inhibits the glycine-induced increase of Ca2+ entry through NMDA receptors in cerebellar granule cells.