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The first of the three groups of rats was taken as a control and the other two groups were injected with high (15 mg/kg) and low (5 mg/kg) doses of ferric ammonium citrate given intramuscularly twice daily for 5 days. Pyelonephritis was produced in all groups by intravenous inoculation with Staphylococcus aureus. Serum and urine of each rat was collected periodically and their iron content was determined. The severity of pyelonephritis was evaluated by determination of bacterial growth and pathological lesions in kidneys after 10 days of bacterial inoculation. The results showed that parenteral iron administration markedly aggravated pyelonephritis development in rats. But there was no significant difference in the severity of pyelonephritis between rats treated with high or low iron doses.

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The development of physical dependence on opiates appears to involve an inhibition by opiates of L-asparaginase and glutaminase, and the blockade by opiates of aspartatergic (ASPergic)/glutamatergic (GLUergic) receptors. Ketamine (K) (0.5 or 1 mg/kg) or dextromethorphan (DM) (1 or 2 mg/kg), both of which are known to decrease the responsiveness of ASPergic/GLUergic receptors, were administered to the three morphine (M)-containing pellets implanted rats prior to 2 mg/kg naloxone (NL) injection. Whereas 0.5 mg/kg K showed no significant effect on abstinence syndrome signs, 1 mg/kg K and 1 mg/kg DM significantly attenuated some of the signs. The attenuation or prevention of all the signs were observed after 2 mg/kg DM administration. Almost complete prevention was seen from the second minute on during the ten-minute observation period. As ASP and GLU antagonists K and DM have this antagonizing effect on the precipitated abstinence syndrome signs, the manifestation of abstinence syndrome may mainly result from the normalization of ASP and GLU production because of the disinhibition by NL of the enzymes and the stronger stimulation of ASPergic/GLUergic receptors which have no opiate blockade after NL injection.

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The inhibition by opiates and the sudden normalization by opioid antagonists of the brain L-asparaginase activity (BAA) have previously been reported to be the main factors in the development of physical dependence and the manifestation of precipitated abstinence syndrome, respectively. As a result, L-asparaginase inhibitors D-aspartic acid and prolyl-leucyl-glycinamide (PLG) were separately given to mice and rats either just after morphine (M)-containing pellet implantation or 15 min before naloxone (NL)-precipitated abstinence syndrome. The animals treated in this manner were used to assess the intensity of the physical dependence and to determine the BAA. D-ASP or PLG administration following pellet implantation significantly increased all of the observed signs such as flying, jumping, wet dog shake and writhing. When D-ASP or PLG were given 15 min before precipitated abstinence they significantly decreased the number of the signs. The determination of the BAA showed significant decreases or increases more or less parallel to the severity of the physical dependence on M. The intensification of physical dependence by D-ASP or PLG given just after the pellet implantation was attributed to their additional inhibitory effect to that of M on the BAA at the beginning of the physical dependence development. The attenuating effect of BAA inhibitors D-ASP or PLG administered before precipitated abstinence was explained with the prevention of the increase in the BAA.

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Experimental pyelonephritis was induced by intravenous inoculation of Staphylococcus aureus in homozygous Brattleboro diabetes insipidus (Hom Brattleboro DI), heterozygous Brattleboro (Het Brattleboro) and Wistar rats. One group of rats from each strain was implanted with morphine-containing pellet three days before inoculation. Another series of groups received D-aspartic acid (D-ASP) intraperitoneally, starting three days before inoculation throughout the experiments. Owing to the inhibition by morphine or D-ASP of food intake, another control group from each strain was subjected to food restriction. Pyelonephritis development on the tenth day of inoculation was evaluated by the determination of viable bacteria in urine and total kidney tissue, and pathomorphological lesions in kidney. Hom Brattleboro DI rats appeared more resistant. Morphine or D-ASP significantly increased the findings in three strains of rat.

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The changes in the production of antibody against Salmonella typhimurium antigen were investigated in rats by means of the agglutination test after chronic oral administration of the L-asparaginase inhibitors morphine (M) or D-aspartic acid (D-Asp) alone or together with L-aspartic acid (L-Asp) and food restriction, all of which had been started five days before the injections of antigen. The statistical evaluation, carried out after the titers had been defined as -log2 of the highest dilution giving a positive agglutination reaction, showed that M or D-Asp significantly decreased antibody production in comparison with the immunized control or food restricted group. The concomitant administration of L-Asp appeared to significantly antagonize the inhibitory effect of both M and D-Asp. Therefore, the results were considered as further supporting evidence for the fact that the deleterious effect of M on the immune system and its functions might be related to the inhibitory effect of M on L-asparaginase activity.

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A comparative study was performed on haematogenous experimental pyelonephritis by injecting a Staphylococcus aureus suspension i.v. to homozygous and heterozygous Brattleboro and Wistar rats. The numbers of viable bacteria in blood, urine and kidney homogenates and the pathomorphological scores determined on the tenth day of infection were significantly lower in Brattleboro diabetes insipidus rats than in heterozygous Brattleboro and normal Wistar rats. The results suggest that homozygous Brattleboro rats are much more resistant to experimental pyelonephritis.

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The brain and lung angiotensin converting enzyme (ACE) activities of the rats subjected to haemorrhagic, hypovolemic or endotoxic shock and of the mice immunized and then intravenously challenged with bovine serum albumin were determined by means of a spectrophotometric method. The lung ACE activities of all the shock groups were found significantly higher than those of their Control groups whereas only the brain ACE activities of the rats in endotoxic shock and the mice in anaphylactic shock showed a significant increase compared to their own control values. The results were interpreted as supporting evidence for the idea that peripheral and central renin-angiotensin systems may play a deleterious role in shock.

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The effect of 3 different doses of chronically-administered morphine on the primary immune response was studied in mice by estimating spleen/body weight ratio and serum hemolysin production against sheep red blood cells (SRBC). It was observed that morphine exerted a dose-dependent inhibitory effect on the immune response which was antagonized by the concomitant administration of naloxone. The findings suggest that the inhibitory effect of morphine is specific.

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We have previously demonstrated the antagonizing effect of aspartic acid on some effects of morphine and on the development of physical dependence on, and tolerance to, morphine. In the present study, we have withdrawal from morphine or administration of a morphine antagonist. For this purpose sixty five white rats were given morphine and aspartic acid separately and in combination in a 5% saccharose solution instead of drinking water for 30 days. Some of the dependent rats were then withdrawn and others were injected with levallorphan. Flying, jumping, wet-dog shaking, body weight loss and motor activity were estimated and free amino acid levels in the brain were determined. Aspartic acid was found to prevent or antagonize the behavioural signs and the changes in the free amino acid levels in the brain. The results are discussed in the light of the previous data.

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Since it has been shown in previous study that aspartic acid prevents the development of physical dependence on and tolerance to morphine and antagonizes the abstinence syndrom signs, the biochemical bases of that prevention were investigated in the present study. The brain contents of serotonin, DA, NA, and free amino acids of the rats given aspartic acid and morphine separately and in combination were determined. It has been observed that most of the morphine-induced changes in the brain were normalized in the group given aspartic acid and morphine together. The relative ineffectiveness of aspartic acid in normalizing some amino acid levels decreased by morphine was discussed and some logical explanations were found.

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As free amino acids in the brain have a role in the development of physical dependence on and tolerance to morphine, and in the mechanism of action of some drugs, the effects of aspartic acid which antagonizes some effects of the single dose of morphine were studied during the development of the physical dependence on morphine and after the withdrawal of morphine. 108 rats were given morphine and aspartic acid in different combinations in drinking water for 30 days. Every tenth day the dose of morphine was increased: At the end of this period some of them in each group continued or began to receive aspartic acid depending on the experimental conditions after the withdrawal of morphine. During the experiments body weight, spontaneous motor activity and analgesic threshold were determined. Aspartic acid prevented the alterations induced by morphine during the development of physical dependence and tolerance. Furthermore the rats that received aspartic acid after the withdrawal showed no body weight loss.

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