Histamine formation in rat brain in vivo: effects of histidine loads

Abstract— Administration of l -histidine at the rate of 500 mg/kg induced an increase of nearly 50 per cent in the level of histamine in rat brain which lasted several hours. The augmentation of histamine level was not significant 3 h after lower doses or after d -histidine α-methyl DOPA and Ro 4-4602 neither affected the cerebral level of histamine nor its elevation induced by l -histidine. Brocresine, a known histidine decarboxylase inhibitor not only prevented the effect of histidine load but also induced a prompt fall in the amine level. These results confirm those from earlier experiments in vitro indicating that histamine synthesis in rat brain depends on a specific decarboxylase (EC 4 , 1.1.22) which is not normally saturated by the endogenous level of its substrate. When histamine levels were enhanced by histidine treatment, histidine decarboxylase activity, as evaluated on hypothalamus homogenates, was significantly reduced; intracisternal administration of cycloheximide, an inhibitor of protein synthesis, had similar effects. On the other hand, enzyme activity was not altered by the addition of histamine to hypothalamus homogenates. These results are compatible with the existence of a regulation mechanism of histidine decarboxylase involving repression by its end-product.     

ENZYMATIC ISOTOPIC ASSAY FOR AND PRESENCE OF β-PHENYLETHYLAMINE IN BRAIN

Abstract— An enzymatic isotopic assay for the measurement of β-phenylethylamine in brain, with a sensitivity of 100-200 pg, has been developed. With this assay, the endogenous β-phenylethylamine content (1.5 ng/g) in the rat brain has been determined. Phenylalanine administration increases the brain levels of this amine; inhibition of monoamine oxidase causes a 40-fold increase in brain β-phenylethylamine. After a combined treatment with a monoamine oxidase inhibitor and phenylalanine, the β-phenylethylamine content in the brain increases to about 400-fold. This increase can be blocked by the central decarboxylase inhibitor NSD-1055. p-Chlorophenylalanine also increases β-phenylethylamipe concentration in the brain, and this effect is potentiated by a simultaneous administration of phenylalanine.     

Ontogenetic Development of Histamine H1- Receptor Binding in Rat Brain

Abstract: Histamine H_1- receptors labeled with [³H]mepyramine in rat brain show an age-dependent development. [³H]Mepyramine receptor density and histidine decarboxylase activity in whole rat brain reach adult levels at 25–30 days after birth and they attain 50% of adult level at day 10 and 17, respectively. The apparently later development of histidine decarboxylase activity in whole rat brain is partly accounted for by a biphasic developmental increase of this enzymatic activity in cerebral cortex. For all other brain regions examined, the development of histamine H_1- receptors parallels that of histidine decarboxylase. The increase in [³H]mepyramine binding can be accounted for by an absolute increase in the numbers of the receptor sites, with no change in affinity. Subcellular fractionation studies indicate that histamine H_1- receptors are predominantly associated with synaptosomal fractions derived from both newborn and adult rat.     

The Significance of Mast Cells as a Source of Histamine in the Mouse Brain

Abstract: Knowledge of the relative contributions of mast cells and neurons to the overall pool of histamine in the brain is a prerequisite to determining the significance and role of this amine in brain function. Consequently, we analyzed the levels of brain histamine in four genotypes (+/+, W/+, W^v/+ , and WIW^v ) of WBB6F₁ mice, whose numbers of brain-associated mast cells vary in a genotypically specific manner. Although mast cell numbers ranged from a total absence of mast cells (W/ W^v ) to an average of about 500 mast cells/brain ( W/+ ), no significant differences between genotypes were found in the quantities of histamine in whole brains, brain regions, or crude subcellular fractions. Thus, in this strain of mice, mast cells are not a significant source of histamine in the brain. This suggests that most of the histamine is of neuronal origin. Since neuronal histamine levels are maintained only by continued histidine decarboxylase activity, complete inhibition of this enzyme by α-fluoromethylhistidine, a "suicide" inhibitor of histidine decarboxylase, would totally deplete W/W^v mice of brain histamine. This was not found to occur in the W/W^v mice, suggesting that neuronal stores of histamine can be maintained in the absence of histidine decarboxylase, or that an additional nonneuronal, non-mast cell source of histamine exists in the W/W^v mouse brain.     

Enhancement of histamine synthesis in mouse skin by epinephrine

Intravenous administration of 10-40 micrograms/Kg epinephrine to mice leads to a transient 50% increase in skin histamine, followed by an increase in blood histamine. Delayed inhibition by alpha-fluorometyl histidine (alpha FMH), suggests that these changes follow stimulation of pre-formed tissue histidine decarboxylase.     

Metabolism of intracerebrally administered histidine, histamine and imidazoleacetic acid in mice and frogs

Abstract— After intracerebral administration of [¹⁴C]histidine to mice the major labelled substance found in the brain extracts was histidine itself; small amounts of labelled carnosine and homocarnosine were detected. No other labelled substances were detected on radio- autographs of two-dimensional TLC's of the extracts. In the case of the frog, radioactive histidine, N-acetylhistidine, carnosine and homocarnosine were found in the brain extracts at various times after intracerebral injection of the labelled histidine. With time, approximately 90 per cent of the radioactivity in the extracts was found in the N-acetylhistidine. In neither the mouse nor frog could we find unequivocal evidence for the formation either of histamine or imidazoleacetic acid from intracerebrally administered histidine, but our analytical procedures may have lacked sufficient sensitivity to pick up extremely low activities of histamine and imidazoleacetic acid. Experiments with [¹⁴C]histamine administered intracerebrally into mice demonstrated the major pathway of metabolism in brain to be histamine → methylhistamine → methylimidazoleacetic acid. No detectable label appeared in inlidazoleacetic acid. In the frog intracerebral administration of the labelled histamine led to the formation of methylhistamine and imidazoleacetic acid, but at most only traces of methylimidazoleacetic acid were found. The injection of [¹⁴C]imidazoleacetic acid intra- cerebrally into mice and frogs resulted in virtually no loss of the label in the form administered in the frog brain over a period of 4 h and in a slow rate of decrease in the mouse brain. No radioactive metabolites of imidazoleacetic acid were found in either species. The limitations of trying to determine natural functions of substances in brain by following the fate of exogenously administered materials is discussed.     

Partial characterization of histidine decarboxylase in hamster and rat brain employing a new method

Histidine decarboxylase activity in hamster and rat brains were studied using a newly developed sensitive, direct radioenzymatic microassay. For our assay conditions, we determined aK _m forl-histidine of 320 M and aV _max for histidine decarboxylase of 110 pmol histamine/hr/mg protein in rat hypothalamus. The regional distributions of both histidine decarboxylase and histamine levels were similar in the hamster and rat with the most activity in hypothalamus. Most of the histidine decarboxylase activity in rat hypothalamus was in the cytosol fraction. The developmental pattern of histidine decarboxylase in the fetal rat did not reveal a prenatal spike in activity. Histidine decarboxylase activity in rat brain reached adult levels by four weeks. Alpha-fluoromethylhistidine inhibited histidine decarboxylase activity almost totally in vitro at 10 M and about 80% in vivo after six days of infusion (100mg/kg/day) in all brain regions except the cerebellum. Likewise, histamine levels were depleted about 75% in all brain regions except the cerebellum.     

N-methyl-D-aspartate receptor antagonists enhance histamine neuron activity in rodent brain

The modulation of histamine neuron activity by various non-competitive NMDA-receptor antagonists was evaluated by changes in tele-methylhistamine (t-MeHA) levels and histidine decarboxylase (hdc) mRNA expression induced in rodent brain. The NMDA open-channel blockers phencyclidine (PCP) and MK-801 enhanced t-MeHA levels in mouse brain by 50-60%. Ifenprodil, which interacts with polyamine sites of NR2B-containing NMDA receptors, had no effect. PCP also increased hdc mRNA expression in the rat tuberomammillary nucleus. The enhancement of t-MeHA levels elicited by MK-801 (ED50 of approximately 0.1 mg/kg) was observed in the hypothalamus, cerebral cortex, striatum and hippocampus. Control t-MeHA levels and the t-MeHA response to MK-801 were not different in male and female mice. Double immunostaining for HDC and NMDA receptor subunits showed that histamine neurons of the rat tuberomammillary nucleus express NMDA receptor subunit 1 (NR1) with NMDA receptor subunit 2A (NR2A) and NMDA receptor 2B subunit (NR2B). In addition, immunoreactivity for the neuronal glutamate transporter EAAC1 was observed near most histaminergic perikarya. Hence, these findings support the existence of histamine/glutamate functional interactions in the brain. The increase in histamine neuron activity induced by NMDA receptor antagonists further suggests a role of histamine neurons in psychotic disorders. In addition, the decrease in MK-801-induced hyperlocomotion observed in mice after administration of ciproxifan further strengthens the potential interest of H3-receptor antagonist/inverse agonists for the symptomatic treatment of schizophrenia.     

Histidine induced hypothermia in the rat

The mechanism by which systemic injection of histidine induces hypothermia has been studied in rats. Injection of histidine directly into the rostral hypothalamic thermoregulatory centers, at sites at which histamine causes hypothermia, had no effect on body temperature. Systemic histidine laoding did not change the hypothalamic or whole brain levels of norepinephrine, dopamine or 5-HT, indicating that the fall in temperature is not due to depletion of these amines which are known to be involved in thermoregulation. Blood pressure measurements showed that when histidine was administered to rats pretreated with a peripherally acting histidine decarboxylase inhibitor no appreciable amount of systemic histamine was formed. It is concluded that the hypothermic effect of histidine is due to the increased formation of histamine in the brain.     

Histamine Turnover in the Brain of Different Mammalian Species: Implications for Neuronal Histamine Half-Life

The turnover of neuronal histamine (HA) in nine brain regions and the spinal cord of the guinea pig and the mouse was estimated and the values obtained were compared with data previously obtained in rats. The size of the neuronal HA pool was determined from the decrease in HA content, as induced by (S)-alpha-fluoro-methylhistidine (alpha-FMH), a suicide inhibitor of histidine decarboxylase. The ratios of neuronal HA to the total differed with the brain region. Pargyline hydrochloride increased the tele-methylhistamine (t-MH) levels linearly up to 2 h after administration in both the guinea pig and the mouse whole brain. Regional differences in the turnover rate of neuronal HA, calculated from the pargyline-induced accumulation of t-MH, as well as in the size of the neuronal HA pool, were more marked in the mouse than in the guinea pig brain. The hypothalamus showed the highest rate in both species. There was a good correlation between the steady-state t-MH levels and the turnover rate in different brain regions. Neither the elevation of the t-MH levels by pargyline nor the reduction of HA by alpha-FMH was observed in the spinal cord, thereby suggesting that the HA present in this region is of mast cell origin. The half-life of neuronal HA in different brain regions was in the range of 13-38 min for the mouse and 24-37 min for the guinea pig, except for HA from the guinea pig hypothalamus, which had an extraordinarily long value of 87 min. These results suggest that there are species differences in the function of the brain histaminergic system.     

Ischemia of rat stomach mobilizes ECL cell histamine

Microdialysis was used to study how ischemia-evoked gastric mucosal injury affects rat stomach histamine, which resides in enterochromaffin-like (ECL) cells and mast cells. A microdialysis probe was inserted into the gastric submucosa, and the celiac artery was clamped (30 min), followed by removal of the clamp. Microdialysate histamine was determined by enzyme-linked immunosorbent assay. In addition, we studied the long-term effects of ischemia on the oxyntic mucosal histidine decarboxylase activity in omeprazole-treated rats. Gastric mucosal lesions induced by the ischemia were enlarged on removal of the clamp. The microdialysate histamine concentration increased immediately on clamping (50-fold rise within 30 min) and declined promptly after the clamp was removed. In contrast, histidine decarboxylase activity of the ECL cells was lowered by the ischemia and returned to preischemic values 9 days later. Mast cell-deficient rats responded to ischemia-reperfusion much like wild-type rats with respect to histamine mobilization. Pretreatment with the irreversible inhibitor of histidine decarboxylase, alpha-fluoromethylhistidine, which is known to eliminate histamine from ECL cells, prevented the rise in microdialysate histamine. Pharmacological blockade of acid secretion (cimetidine or omeprazole) prevented the lesions induced by ischemia-reperfusion insult but not the mobilization of histamine. In conclusion, ischemia of the celiac artery mobilizes large amounts of histamine from ECL cells, which occurs independently of the gross mucosal lesions. The prompt reduction of the mucosal histidine decarboxylase activity in response to ischemia probably reflects ECL cell damage. The lesions develop not because of mobilization of histamine per se but because of ischemia plus reperfusion plus gastric acid.     

Peroxidation-induced changes of histamine metabolism and transport of its precursor histidine in rat brain synaptosomes

The metabolism of histamine and transport of its precursor histidine were investigated in rat brain synaptosomes which underwent the ADP-Fe/ascorbate-induced peroxidation. Peroxidation impaired histidine uptake by 40%, and veratridine induced release of it by 25% of maximal uptake. Simultaneously, marked decrease of synaptosomal histamine (HA) content, to about 30% of control value, was found (p less than 0.01). Activity of the two histamine-metabolizing enzymes, histidine decarboxylase (HD) and histamine N-methyl-transferase (HMT), were drastically lowered, by 40% (p less than 0.02) and 60% of control (p less than 0.05), respectively. Pretreatment of rats with glucocorticoid analog, dexamethasone (DMX), 1 mg/kg of body weight, given twice, 20 and 2 h before decapitation, did not influence significantly the effects invoked by peroxidation on HA levels and the activity of HD and HMT, but impaired histidine transport. These results indicate that iron-dependent peroxidation decreases both neuronal pool of histamine and its turnover, which may affect the function of central nervous system. Short pretreatment with dexamethasone does not seem to influence this effect.     

Increased methamphetamine-induced locomotor activity and behavioral sensitization in histamine-deficient mice

We have recently suggested that the brain histamine has an inhibitory role on the behavioral effects of methamphetamine by pharmacological studies. In this study, we used the histidine decarboxylase gene knockout mice and measured the spontaneous locomotor activity, the changes of locomotion by single and repeated administrations of methamphetamine, and the contents of brain monoamines and amino acids at 1 h after a single administration of methamphetamine. In the histidine decarboxylase gene knockout mice, spontaneous locomotor activity during the dark period was significantly lower than in the wild-type mice. Interestingly, methamphetamine-induced locomotor hyperactivity and behavioral sensitization were facilitated more in the histidine decarboxylase gene knockout mice. In the neurochemical study, noradrenaline and O-phosphoserine were decreased in the midbrain of the saline-treated histidine decarboxylase gene knockout mice. On the other hand, single administration of methamphetamine decreased GABA content of the midbrain of the wild-type mice, but did not alter that of histidine decarboxylase gene knockout mice. These results suggest that the histamine neuron system plays a role as an awakening amine in concert with the noradrenaline neuron system, whereas it has an inhibitory role on the behavioral effects of methamphetamine through the interaction with the GABAergic neuron system.     

Induction of histidine decarboxylase in rat basophilic leukemia cells by interferon and prevention of its effect in coincubation with ADP-ribosyltransferase inhibitors

Treatment of rat basophilic leukemia cell line (2H3) with interferon-alpha significantly increased intracellular histamine levels. On the other hand, the histidine content was decreased reciprocally by interferon in a dose-dependent manner. Concomitantly, the activity of histidine decarboxylase, the enzyme responsible for histamine synthesis, was augmented. The increase in histidine decarboxylase activity was partially abolished in co-incubation with inhibitors of ADP-ribosyltransferase, such as 3-aminobenzamide or nicotinamide. These results suggest the pivotal role of activation of histidine decarboxylase, presumably through ADP-ribosylation of the enzyme, in interferon-induced histamine synthesis.     

Lack of a Precursor-Product Relationship Between Histamine and Its Metabolites in Brain After Histidine Loading

Abstract: Levels of histamine and its major metabolites in brain, tele -methylhistamine (t-MH) and tele -methylimidazoleacetic acid (t-MIAA), were measured in rat brains up to 12 h after intraperitoneal administration of l -histidine (His), the precursor of histamine. Compared with saline-treated controls, mean levels of histamine were elevated at 1 h (+ 102%) after a 500 mg/kg dose; levels of t-MH did not increase. Following a 1,000 mg/kg dose; levels mean histamine levels were increased for up to 7 h, peaked at 3 h, and returned to control levels within 12 h. In contrast, levels of t-MH showed a small increase only after 3 h; levels of t-MIAA remained unchanged after either dose. Failure of most newly formed histamine to undergo methylation, its major route of metabolism in brain, suggested that histamine was metabolized by another mechanism possibly following nonspecific decarboxylation. To test this hypothesis, other rats were injected with α-fluoromethylhistidine (α-FMHis; 75 mg/kg, i.p.), an irreversible inhibitor of specific histidine decarboxylase. Six hours after rats received α-FMHis, the mean brain histamine level was reduced 30% compared with saline-treated controls. Rats given His (1,000 mg/kg) 3 h after α-FMHis (75 mg/kg) and examined 3 h later had a higher (+112%) mean level of histamine than rats given α-FMHis, followed by saline. Levels of t-MH and t-MIAA did not increase. These results imply that high doses of His distort the simple precursor-product relationship between histamine and its methylated metabolites in brain. The possibility that some His may undergo nonspecific decarboxylation in brain after His loading is discussed. These findings, and other actions of His independent of histamine, raise questions about the validity of using His loading as a specific probe of brain histaminergic function.     

The effect of volatile anaesthetics on levels of metabolites and on metabolic rate in brain

Anaesthesia with ether, halothane, methoxyflurane (Penthrane) and Ohio 347 (Ethrane) increased the energy stores in mouse brain as much as 1·7-fold above the control values. The greatest increases were observed in glucose and glycogen. Glucose-6-P was increased in some cases and UDP glucose was consistently lower in the anaesthetized animals. Hypothermia in conjunction with anaesthesia modified some of the observed changes. Hypothermia alone was associated with an increase in P-creatine and glucose and a decrease in UDPglucose in the brain. The cerebral metabolic rate was depressed by all the anaesthetic agents to about 50 per cent of the control value. When the body temperature was lowered to 25°, the cerebral metabolic rate fell to 73 per cent of the control rate. A temperature coefficient of 1·035 was calculated as the fractional change/degree between 25° and 34°.     

Glycogen, ammonia and related metabolities in the brain during seizures evoked by methionine sulphoximine

Abstract— The levels of ATP, P-creatine, glucose, glycogen, lactate, glutamate and ammonia were measured in mouse brain after administration of the convulsive agent methionine sulphoximine (MSO). No changes were observed in ATP and P-creatine levels either before or during the seizures. Lactate levels were unchanged until the onset of seizures (4–5 hr) at which time the levels increased an average of 65 per cent. Glucose and glycogen levels increased progressively. Just before the onset of seizures the levels had increased 95 and 62 per cent, respectively. During the seizures both substances had increased a total of 130 per cent. Comparable changes were found in cerebral cortex, cerebellum and subcortical forebrain. Through the use of quantitative histochemical methods it was found that the greatest increases in glycogen occurred in layers I and III (layers II and IV were not analysed). Progressively smaller changes were found in layers V and VI and no increase at all was found in the subjacent white matter. Glucose, in contrast to glycogen, increased to about the same degree in all cerebral layers and in subjacent white matter. The increase in glycogen after MSO administration may be related to the fact that MSO also causes an increase in the ratio of brain to serum glucose levels. This would indicate that an increase in intracellular glucose had occurred. Ammonia levels were increased 300–400 per cent in both cerebrum and cerebellum. A time study in cerebellum showed that the increase begins early and reaches maximal levels long before the onset of seizures. Glutamate levels were reduced by small but statistically significant amounts in both cerebrum and cerebellum. Administration of methionine sulphoximine completely prevented seizures and the increase in lactate, but did not prevent the increases in glycogen and glucose. The rise in ammonia was reduced but not prevented. During 20 sec of complete ischaemia (decapitation) ATP, P-creatine and glucose fell somewhat more rapidly than normal in brain of animals undergoing MSO seizures. From the changes it was calculated that the metabolic rate had been increased about 20 per cent by the seizure. A new sensitive and specific enzymic method for determination of tissue ammonia is presented together with evised enzymic procedures for lactate and glutamate.     

Antisera Against Rat Recombinant Histidine Decarboxylase: Immunocytochemical Studies in Different Species

Histamine is involved in many important biological processes such as allergic reactions, gastric acid secretion and neurotransmission. The formation of histamine is catalysed by the enzyme histidine decarboxylase. In order to understand the role of histamine in different tissues, information about the cellular localisation of the decarboxylase is important. However, the availability of antisera against the enzyme, which can be used in immunocytochemical techniques, has so far been limited, mainly due to the difficulties in purifying sufficient amounts of histidine decarboxylase from various tissues. In the present study we describe the use of antisera raised against rat recombinant histidine decarboxylase to localise the enzyme immunocytochemically in the gastric mucosa of different mammals and submammalian vertebrates. The antisera specifically stained histidine decarboxylase-immunoreactive cells in the gastric mucosa of not only rat, but also of species like frog, chicken, mouse and dog. This is the first report describing the immunocytochemical distribution of the decarboxylase in the gastric mucosa of species other than rat. These antisera are likely to become valuable tools for further studies of the immunocytochemical localisation of histidine decarboxylase.     

In vitro demonstration of histamine biosynthesis from carnosine by kidneys of pregnant mice

Kidneys of pregnant mice synthesize histamine when incubated in the presence of carnosine, manganese, and pyridoxal phosphate. Intensity of biosynthesis increases linearly with the amount of enzyme and the incubation time. The reaction can only be catalysed by two enzymes that are located in kidneys and act in succession: carnosinase, which hydrolyzes carnosine into its two moieties, and histidine decarboxylase, which transforms histidine, a product of carnosine degradation, into histamine. The biosynthesis of histamine from carnosine seems to increase with the progress of pregnancy. In nonpregnant mice, kidneys do not effect this biosynthesis. The above results directly demonstrate that carnosine may be used for histamine synthesis when the activity of histidine decarboxylase is high, as in pregnant mouse kidney. Vertebrate carnosine, its role still enigmatic, might thus be mainly a potential histidine reservoir that would be mobilized any time there is a significant requirement for histidine, such as for histamine biosynthesis.     

Resistance to antibiotics and histamine production at the bacteria, isolated from the stomatopharynx of the children with bronchial asthma]

1549 strains of bacteria (gram-positive and gram-negative bacteria and Candida) were isolated from the 117 children (65 with bronchial asthma and 52 healthy one) aged from 3 to 14 years old. Susceptibility of 1213 strains to 20 antibiotics was determined by disk-diffusion method. It was shown that 336 strains produce histidine decarboxylase and for 40 strains the quantity of the produced histamine was measured on the Moeller medium. Histamine-modifying activity was investigated at 32 strains in vitro by fluorometric method. Reduced colonization resistance of the pharynx of the children with bronchial asthma was shown. Spectrum of bacteria with histidine decarboxylase activity was more wide at the children with asthma. Histamine production was about 1 mcg/mL at streptococci, staphylococci and hemophilic bacteria, from 1 to 3 mcg/mL - at bacilli, corynebacteria and Candida, from 1 to 10 mcg/mL - at lactobacilli, enterobacteria, pseudomonades, acinetobacteria. Ability for partial histamine destruction in virowas demonstrated for some strains of lactobacilli, enterobacteria and pseudomonades (initial histamine concentration reduced on 19.4-35.8 per cent after 48-hour incubation).