Perinatal Manganese Exposure and Hydroxyl Radical Formation in Rat Brain

The present study was designed to investigate the role of pre- and postnatal manganese (Mn) exposure on hydroxyl radical (HO•) formation in the brains of dopamine (DA) partially denervated rats (Parkinsonian rats). Wistar rats were given tap water containing 10,000 ppm manganese chloride during the duration of pregnancy and until the time of weaning. Control rat dams consumed tap water without added Mn. Three days after birth, rats of both groups were treated with 6-hydroxydopamine at one of three doses (15, 30, or 67 µg, intraventricular on each side), or saline vehicle. We found that Mn content in the brain, kidney, liver, and bone was significantly elevated in dams exposed to Mn during pregnancy. In neonates, the major organs that accumulated Mn were the femoral bone and liver. However, Mn was not elevated in tissues in adulthood. To determine the possible effect on generation of the reactive species, HO• in Mn-induced neurotoxicity, we analyzed the contents of 2.3- and 2.5-dihydroxybenzoic acid (spin trap products of salicylate; HO• being an index of in vivo HO• generation), as well as antioxidant enzyme activities of superoxide dismutase (SOD) isoenzymes and glutathione S-transferase (GST). 6-OHDA-depletion of DA produced enhanced HO• formation in the brain tissue of newborn and adulthood rats that had been exposed to Mn, and the latter effect did not depend on the extent of DA denervation. Additionally, the extraneuronal, microdialysate, content of HO• in neostriatum was likewise elevated in 6-OHDA-lesioned rats. Interestingly, there was no difference in extraneuronal HO• formation in the neostriatum of Mn-exposed versus control rats. In summary, findings in this study indicate that Mn crosses the placenta but in contrast to other heavy metals, Mn is not deposited long term in tissues. Also, damage to the dopaminergic system acts as a “trigger mechanism,” initiating a cascade of adverse events leading to a protracted increase in HO• generation, and the effects of Mn and 6-OHDA are compounded. Moreover, HO• generation parallels the suppression of SOD isoenzymes and GST in the brains of rats lesioned with 6-OHDA and/or intoxicated with Mn—the most prominent impairments being in frontal cortex, striatum, and brain stem. In conclusion, ontogenetic Mn exposure, resulting in reactive oxygen species, HO• formation, represents a risk factor for dopaminergic neurotoxicity and development of neurodegenerative disorders

Nitric Oxide (NO) and Central Dopamine (DA) D\u3csub\u3e3\u3c/sub\u3e Receptor Reactivity to Quinpirole in Rats

Nitric oxide (NO) has been implicated in large number of pathologies and in normal physiological function of the brain. The aim of this study was to recognize the effect of Nitro-L-Arginine Methyl Ester ·HCl (NAME) and L-Arginine Ethyl Ester.HCl (ARGININE) on reactivity of the central DA D3 receptor to agonist (Quinpirole) in rats. For this reason we have been used specific behavioural procedure such yawning behaviour which is mediated via central DA D3 receptors. Experiments were perform in adult male Wistar rats treated daily with quinpirole (0.05 mg/kg IP) or vehicle (0.9% NaCl) for the first 11 days from birth to obtain of the central D3 receptor supersensitivity. NAME and ARGININE in different way modified response of the central DA receptor to quinpirole estimated by means yawning behavioural procedure

Lifelong Rodent Model of Tardive Dyskinesia-Persistence After Antipsychotic Drug Withdrawal

Tardive dyskinesia (TD), first appearing in humans after introduction of the phenothiazine class of antipsychotics in the 1950s, is now recognized as an abnormality resulting predominately by long-term block of dopamine (DA) D2 receptors (R). TD is thus reproduced in primates and rodents by chronic administration of D2-R antagonists. Through a series of studies predominately since the 1980s, it has been shown in rodent modeling of TD that when haloperidol or other D2-R antagonist is added to drinking water, rats develop spontaneous oral dyskinesias, vacuous chewing movements (VCMs), after ~3 months, and this TD is associated with an increase in the number of striatal D2-R. This TD persists for the duration of haloperidol administration and another ~2 months after haloperidol withdrawal. By neonatally lesioning dopaminergic nerves in brain in neonatal rats with 6-hydroxydopamine (6-OHDA), it has been found that TD develops sooner, at ~2 months, and also is accompanied by a much higher number of VCMs in these haloperidol-treated lesioned rats, and the TD persists lifelong after haloperidol withdrawal, but is not associated with an increased D2-R number in the haloperidol-withdrawn phase. TD apparently is related in part to supersensitization of both D1-R and serotoninergic 5-HT2-R, which is also a typical outcome of neonatal 6-OHDA (n6-OHDA) lesioning. Testing during the haloperidol-withdrawn phase in n6-OHDA rats displaying TD reveals that receptor agonists and antagonists of a host of neuronal phenotypic classes have virtually no effect on spontaneous VCM number, except for 5-HT2-R antagonists which acutely abate the incidence of VCMs in part. Extrapolating to human TD, it appears that (1)5-HT2-R supersensitization is the crucial alteration accounting for persistence of TD, (2) dopaminergic-perhaps age-related partial denervation-is a risk factor for the development of TD, and (3) 5-HT2-R antagonists have the therapeutic potential to alleviate TD, particularly if/when an antipsychotic D2-R blocker is withdrawn

Stres i nowotwór

Scientific research has shown that during stress, the secretion of hormones and neurotransmitters in the brain, etc. is definitely stronger and longer lasting when persons are convinced that they cannot cope with the requirements of a stressful situation, i.e. they are in a state of uncontrolled stress. The main indicator of this condition is a long-term increase in the concentration of stress hormones in the blood. The higher the catecholamine concentration, the more DNA damage, the more cells undergoing tumour transformation, the larger the tumour and the more advanced the disease. Catecholamines also narrow blood vessels, which leads to an increase in VEGF expression, responsible for an increase in angiogenesis, and hence tumour growth and tumour metastasis. Cortisol contributes to inhibition of the immune system and changes in the central nervous system. Under uncontrolled stress, telomeres are shortened, which is another reason for shortening life expectancy. It has also been proven that stress and trauma are inherited in subsequent generations in the mechanism of epigenetic inheritance. Despite epigenetic predispositions to develop various malignancies, including ovarian, stomach and colorectal cancer, people can move from uncontrolled to controlled stress in a particular situation, even though the situation itself does not change. This is a breakthrough message. During cancer, the transition to controlled stress definitely supports therapy, increasing your chances of survival or even recovery. The most common condition for taking control of stress is to change your current lifestyle.Badania naukowe dowiodły, że w czasie stresu wydzielanie hormonów, neuroprzekaźników w mózgu itp. jest zdecydowanie silniejsze i trwa dłużej, zwłaszcza jeśli człowiek jest przekonany, że nie będzie w stanie sprostać wymaganiom sytuacji stresowej, czyli pozostaje w stanie stresu niekontrolowanego. Głównym wskaźnikiem tego stanu jest długo trwający przyrost stężenia hormonów stresu we krwi. Im większe stężenie katecholamin, tym więcej uszkodzeń DNA, więcej komórek ulegających transformacji nowotworowej, większy guz i bardziej zaawansowana choroba. Katecholaminy ponadto zwężają naczynia krwionośne, co przyczynia się do wzrostu ekspresji czynnika VEGF, który zwiększa angiogenezę, wzrost guza i przerzuty nowotworowe. Kortyzol przyczynia się do hamowania układu immunologicznego i zmian w ośrodkowym układzie nerwowym. W stresie niekontrolowanym skróceniu ulegają telomery, które są kolejną przyczyną skrócenia długości życia. Dowiedziono także, że stres i trauma są dziedziczone w kolejnych pokoleniach w mechanizmie dziedziczenia epigenetycznego. Pojawiają się wtedy predyspozycje epigenetyczne do zachorowania na różne nowotwory złośliwe, w tym raka jajnika, żołądka, jelita grubego. W konkretnej sytuacji można jednak przejść ze stresu niekontrolowanego do kontrolowanego, mimo że sama sytuacja się nie zmienia, i to jest wiadomość przełomowa. W trakcie choroby nowotworowej wejście w stan stresu kontrolowanego zdecydowanie wspomaga terapię, zwiększając szansę na przeżycie lub nawet wyzdrowienie. Najczęściej warunkiem przejęcia kontroli nad stresem jest zmiana dotychczasowego stylu życia. Radzenie sobie ze stresem, aktywność ruchowa i zdrowe odżywianie się są w stanie nawet doprowadzić do zmian na poziomie epigenomu, a badania naukowe dowodzą, że możemy wtedy uporać się z licznymi odziedziczonymi predyspozycjami, zmniejszając prawdopodobieństwo zachorowania na nowotwory złośliwe

Ontogenic Homologous Supersensitization of Quinpirole-Induced Yawning in Rats

Yawning in male rats is a behavior that may be induced by a group of dopamine receptors when low doses of dopamine-receptor agonists are administered. To determine whether agonist treatments during postnatal development could produce a long-lived supersensitization of these dopamine receptors, rats were treated daily for the first 28 days from birth with quinpirole HCl (3.0 mg/kg/day, IP), an agonist that acts at D2 and D3 receptors. At 8 to 10 weeks from birth the dose-effect curve for quinpirole-induced yawning demonstrated that a supersensitization of dopamine receptors for yawning behavior had occurred. Yawning at the optimal dose of quinpirole HCl (100 μg/kg, IP) was increased 2-fold. The Bmax and Kd for D2 receptor binding in rat striatum were unaltered in this group of rats. These findings indicate that dopamine receptors can be ontogenically primed or supersensitized, and that the phenomenon apparently is not related to changes in striatal D2 receptor binding characteristics

Nitro-1-Arginine Attenuates SKF 38393 - Induced Oral Activity in Neonatal 6-Hydroxydopamine-Lesioned Rats

Nitric oxide (NO) in brain has been implicated in neuronal regulatory processes and in neuropathologies. Previously we showed that NO modified quinpirole-induced yawning, a behavioral measure of dopamine (DA) Da receptor activation in rats. The aim of this study was to characterize the effect of nitro-L-arginine methyl ester HC1 (NAME) and L-arginine HC1 on reactivity of rats to the DA DI receptor agonist SKF 38393 and DA DI antagonist SCH 23390 in intact and neonatal 6-hydroxydopamine (o-OHDA)-lesioned rats (134 ng of base ICV at 3rd day after birth). L-arginine HC1 (300 mg/kg IP) increased the oral activity response in 6-OHDA-lesioned rats, like SKF 38393, and induced catalepsy in intact control rats, like SCH 23390. In contrast, NAME had no effect on oral activity or catalepsy, but fully attenuated SKF 38393-induced oral activity. These findings indicate that L-arginine HC1 has no apparent effect at the DA DI receptor, but that NAME is effective in attenuating a DA DI agonist induced effect. Consequently NO may be an intracellular second messenger for supersensitized receptors associated with DA DI agonist - induced oral activity

Sensitivity of Central Dopamine Receptors in Rats, to Quinpirole and SKF-38393, Administered at Their Early Stages of Ontogenicity, Evaluated by Learning and Memorizing a Conditioned Avoidance Reflex

Male and Female newborn rats were primed with either quinpirole 0.05 mg/kg IP or SKF-38393 0.1 mg/kg IP on days 1-11, 12-22 and 23-33 of their lives. When the rats reached the age of 13 weeks, they were placed on metal rods in an activity avoidance chamber, and light and electric current of 30V/0.8 mA were used on them as conditioning stimuli. Avoidance of the electric shock was considered a positive conditioned reaction. Training and memorizing the conditioned avoidance reflex consisted of a series of ten trials, 60 seconds apart, once a week for ten weeks. The mean number of positive responses after quinpirole was more profound in all priming intervals tested, as compared to SKF-38393, and was higher as the priming started later in life. Significantly higher scores were obtained by the female rats primed with quinpirole, as compared to the male rats primed with the same drug. These differences were much weaker with SKF-38393. These findings confirm that the central D2 receptor system is involved in learn ing and memorizing of Conditioned Avoidance Reflex much more than the D1 receptors do, and that female rats are more sensitive and retentive to this reflex

Induction of Grooming Behavior in Male Rats by M-Chlorphenylpiperazine, a Central 5-Hydroxytryptamine Receptor Agonist

Grooming behavior in rats has so far been known to be induced mainly by dopamine agonists type D1. In order to explore the involvement of serotonine (5-HT) and its receptors in such a behavior, rats were exposed to two phases of treatment: to the serotonin neurotoxin 5,7-dihydroxytryptamine (5,7-DHT), injected intraventricularly three days after birth, and to the serotonin partial agonist m-chlorophenylpiperazine (mCPP), administered in two dose levels, two months later. Grooming behavior was monitored immediately before and after the higher dose of mCPP, while brain levels of 5-HT and its major metabolite 5-HIAA were assayed one week after mCPP administration. It is documented that while a low dose of mCPP in the non-lesioned rats increased the grooming-time by 5.7-fold, the higher mCPP dose in the non-lesioned non-primed rats increased grooming behavior by 3.6-fold. The 5,7-DHT lesions caused a 6.7-fold increase in the non-primed rats, and a 4.2-fold increase in the primed ones. These increases were noticeable only in male rats. When a higher dose of mCPP followed its lower dose in the 5,7-DHT-lesioned rats, a 3.6-fold decrease was recorded only in the female rats. A 88% and 94% drop in 5-HT and 5-HIAA levels in the brain neostriatum of the 5,7-DHT-lesioned rats was noticed in both sexes, one week after mCPP administration. These findings are the first to demonstrate that the 5-HT2 partial agonist mCPP is capable of modifying grooming behavior, and that 5,7,-DHT brain lesions increase basal grooming time, suggesting that 5-HT neurons and receptors are involved in grooming behavior in rats

7-OH-DPAT, Unlike Quinpirole, Does Not Prime a Yawning Response in Rats

Repeated treatment in ontogeny with the dopamine (DA) D2/D3 receptor agonist quinpirole is associated with enhanced quinpirole-induced yawning and other behaviors such as vacuous chewing, vertical jumping, and antinociception. To determine if the reputedly DA D3 agonist (±)-2-(dipropylamino)-7-hydroxy-1,2,3,4-tetrahydronaphthalene (7-OH-DPAT) would prime for yawning in a manner analogous to that for quinpirole, rats were treated for the first 11 days after birth with an equimolar dose of either quinpirole or 7-OH-DPAT (195.4 nmol/kg/day) and tested for agonist-induced yawning in adulthood. While enhanced quinpirole-induced and 7-OH-DPAT-induced yawning was observed in quinpirole-primed rats, acute treatments with quinpirole and 7-OH-DPAT did not produce an enhanced yawing response in 7-OH-DPAT-\u27primed\u27 rats. Our findings indicate that 7-OH-DPAT, unlike quinpirole, does not prime for quinpirole- or 7-OH-DPAT-induced yawning in rats