Perillyl Alcohol Mitigates Behavioural Changes and Limits Cell Death and Mitochondrial Changes in Unilateral 6-OHDA Lesion Model of Parkinson's Disease Through Alleviation of Oxidative Stress.

In this study, we aim to assess the phytomedicinal potential of perillyl alcohol (PA), a dietary monoterpenoid, in a unilateral 6-hydroxydopamine (6-OHDA) lesion rat model of Parkinson's disease (PD). We observed that PA supplementation alleviated behavioural abnormalities such as loss of coordination, reduced rearing and motor asymmetry in lesioned animals. We also observed that PA-treated animals exhibited reduced oxidative stress, DNA fragmentation and caspase 3 activity indicating alleviation of apoptotic cell death. We found reduced mRNA levels of pro-apoptotic regulator BAX and pro-inflammatory mediators IL18 and TNFα in PA-treated animals. Further, PA treatment successfully increased mRNA and protein levels of Bcl2, mitochondrial biogenesis regulator PGC1α and tyrosine hydroxylase (TH) in lesioned animals. We observed that PA treatment blocked BAX and Drp1 translocation to mitochondria, an event often associated with the inception of apoptosis. Further, 6-OHDA exposure reduced expression of electron transport chain complexes I and IV, thereby disturbing energy metabolism. Conversely, expression levels of both complexes were upregulated with PA treatment in lesioned rats. Finally, we found that protein levels of Nrf2, the transcription factor responsible for antioxidant gene expression, were markedly reduced in cytosolic and nuclear fraction on 6-OHDA exposure, and PA increased expression of Nrf2 in both fractions. We believe that our data hints towards PA having the ability to provide cytoprotection in a hemiparkinsonian rat model through alleviation of motor deficits, oxidative stress, mitochondrial dysfunction and apoptosis.

Kaempferol derivatives prevent oxidative stress-induced cell death in a DJ-1-dependent manner.

DJ-1, a causative gene product of a familial form of Parkinson's disease (PD), PARK7, plays a role in anti-oxidative stress, and loss of its function is thought to result in the onset of PD. Superfluous oxidation of cysteine at amino acid 106 (C106) of DJ-1 renders DJ-1 inactive, and such oxidized DJ-1 was observed in patients with the sporadic form of PD. In this study, we examined the relationship between DJ-1 and compounds extracted from traditional Chinese medicines possessing anti-oxidant activity. Of the 12 compounds tested, 5 were found to specifically bind to the C106 region by using a quartz crystal microbalance. Although 4 compounds prevented rat PC12 and primary neuronal cells from undergoing H2O2-induced cell death, the protective activity of 2 compounds, kaempferol 3-O-beta-rutinoside and 6-hydroxykaempferol 3,6-di-O-beta-D-glucoside, was diminished in cells transfected with siRNA targeting DJ-1, indicating DJ-1-dependent reaction of these compounds. Furthermore, these compounds reduced the level of reactive oxygen species and restored tyrosine hydroxylase activity that had been induced and compromised, respectively, by treatment of cells with H2O2. The results suggest that these compounds are useful lead compounds for PD therapy.

Catalpol attenuates nitric oxide increase via ERK signaling pathways induced by rotenone in mesencephalic neurons.

Catalpol has been shown to rescue neurons from kinds of damage in vitro and in vivo in previous reports. However, the effect of catalpol on the nitric oxide (NO) system via MAPKs signaling pathway of mesencephalic neurons largely remains to be verified. The current study examined that whether catalpol modulated NO and iNOS increase by rotenone in primary mesencephalic neurons and investigated its underlying signaling pathways. Present results indicated that catalpol inhibited primary mesencephalic neurons from apoptosis by morphological assay, immunocytochemistry and flow cytometric evaluation. Moreover, the ERK signaling pathway plays an important role in NO-mediated degeneration of neuron. The current results suggest that catalpol is a potential agent for the prevention of neurons apoptosis by regulating NO and iNOS increase in ERK-mediated neurodegenerative disorders.

Acupuncture attenuates cocaine-induced expression of behavioral sensitization in rats: possible involvement of the dopaminergic system in the ventral tegmental area.

Acupuncture is widely used for the treatment of many functional disorders, such as substance abuse, and has the suppressive effect on the central nervous system. Many studies have suggested that behavioral sensitization by repeated injections of cocaine produce an increase in locomotor activity and an increase in the expression of tyrosine hydroxylase (TH), in the central dopaminergic system. In order to investigate the effects of acupuncture on the repeated cocaine-induced neuronal and behavioral sensitization alternations, we examined the influence of acupuncture on the repeated cocaine-induced locomotor activity and the expression of TH in the brain using immunohistochemistry. Male SD rats were given repeated injections of cocaine hydrochloride (15 mg/kg, i.p. for 10 consecutive days) followed by one challenge injection on the 4th day after the last daily injection. Cocaine challenge produced a large increase in the locomotor activity and the expression of TH in the ventral tegmental area (VTA). Treatment with acupuncture bilaterally at the Shenman (HT7) points for 1 min significantly inhibited the increase of locomotor activity as well as the TH expression in the VTA. Our data demonstrated that the inhibitory effects of acupuncture on cocaine-induced expression of behavioral sensitization were closely associated with the reduction of dopamine (DA) biosynthesis and the postsynaptic neuronal activity. These results provide evidence that acupuncture may be effective for inhibiting the behavioral effects of cocaine by possible modulation of the central dopaminergic system.

The footfault test as a screening tool in the 6-hydroxydopamine rat model of Parkinson's disease.

The administration of 6-hydroxydopamine (6-OHDA) into the nigrostriatal pathway is a rat model of Parkinson's disease (PD). The footfault test is a behavioural task in which rodents have their motor functions assessed. Here, we observed that unilaterally 6-OHDA-lesioned animals show a context-induced ipsilateral rotational behaviour when placed on the footfault apparatus for 3 min and this may be used as index to detect lesioned animals. Our results showed a sensitivity and specificity of 100% for lesions higher than 94% and 64%, respectively (ROC curve: AUC=0.988). A binary logistic regression model showed an expB=1.116 (95% CI, 1.007-1.236) and C=-9.081+/-4.554 (p=0.046) using the nigral tyrosine hidroxylase immunocontent as standard (each unit represents a 10%-lesion extension). Additionally, the footfault test was more sensitive than apomorphine challenging at 1mg/kg when these tests were carried out days apart and it was less sensitive than methylphenidate at 40 mg/kg (sign test, p<0.05). Therefore, the footfault test may be very useful in the PD animal model for screening animals since it is fast and simple and it does not require a drug to induce rotational activity.

Retinol activates tyrosine hydroxylase acutely by increasing the phosphorylation of serine40 and then serine31 in bovine adrenal chromaffin cells.

Tyrosine hydroxylase is the rate-limiting enzyme in the biosynthesis of the catecholamines. It has been reported that retinol (vitamin A) modulates tyrosine hydroxylase activity by increasing its expression through the activation of the nuclear retinoid receptors. In this study, we observed that retinol also leads to an acute activation of tyrosine hydroxylase in bovine adrenal chromaffin cells and this was shown to occur via two distinct non-genomic mechanisms. In the first mechanism, retinol induced an influx in extracellular calcium, activation of protein kinase C and serine40 phosphorylation, leading to tyrosine hydroxylase activation within 15 min. This effect then declined over time. The retinol-induced rise in intracellular calcium then led to a second slower mechanism; this involved an increase in reactive oxygen species, activation of extracellular signal-regulated kinase 1/2 and serine31 phosphorylation and the maintenance of tyrosine hydroxylase activation for up to 2 h. No effects were observed with retinoic acid. These results show that retinol activates tyrosine hydroxylase via two sequential non-genomic mechanisms, which have not previously been characterized. These mechanisms are likely to operate in vivo to facilitate the stress response, especially when vitamin supplements are taken or when retinol is used as a therapeutic agent.

Neuroprotective effects of echinacoside in the mouse MPTP model of Parkinson's disease.

In the present study, we investigated the neuroprotective effects of echinacoside, a phenylethanoid glycoside extracted from the medicinal Chinese herb Cistanches salsa, against 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced dopaminergic toxicity. We confirmed that exposure to MPTP in mice leads to permanent behavioral deficits and depletion of dopamine and its metabolites. When administered prior to MPTP, echinacoside reduced behavioral deficits, increased striatal dopamine and dopamine metabolite levels, reduced cell death, and led to a marked increase in tyrosine hydroxylase expression relative to mice treated with MPTP alone. In addition, pre-treatment with echinacoside significantly reduced caspase-3 and caspase-8 activation in 1-methyl-4-phenylpyridinium (MPP(+))-induced apoptosis in cerebellar granule neurons. Taken together, these findings suggest that echinacoside improves the behavioral and neurochemical outcomes in MPTP mice model of Parkinson's disease and inhibits caspase-3 and caspase-8 activation in cerebellar granule neurons, making the compound an attractive candidate treatment for various neurodegenerative disorders, including Parkinson's disease.

5-HT1A receptor agonist-mediated protection from MPTP toxicity in mouse and macaque models of Parkinson's disease.

Excitotoxicity-mediated cell death is involved in Parkinson's disease (PD). 5-HT1A receptor agonists can protect from such mechanisms. The current study demonstrates that the 5-HT1A agonists BAY 639044 and repinotan have neuroprotective effects in a subacute 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of PD. In addition, we also show that both compounds delay the appearance of parkinsonian motor abnormalities in a MPTP monkey model that recapitulates the progressive nature of PD. Thus, BAY 639044 or repinotan treatment was initiated when there was 30% neuronal death in the substantia nigra pars compacta, and nerve terminal loss in the striatum was 40%, i.e., compatible with the clinical situation where early symptomatic patients would receive such a treatment. The delay in appearance of parkinsonian motor abnormalities is a consequence of partial neuroprotection of nigrostriatal dopamine neurons, both at neuronal and terminal levels as shown for BAY 639044. These results suggest that 5-HT1A agonists, such as BAY 639044, may protect from neurodegeneration and delay the worsening of motor symptoms in Parkinson patients.

Neuroprotective and neurorescue effect of black tea extract in 6-hydroxydopamine-lesioned rat model of Parkinson's disease.

In the present study, an attempt has been made to explore the neuroprotective and neuroreparative (neurorescue) effect of black tea extract (BTE) in 6-hydroxydopamine (6-OHDA)-lesioned rat model of Parkinson's disease (PD). In the neuroprotective (BTE + 6-OHDA) and neurorescue (6-OHDA + BTE) experiments, the rats were given 1.5% BTE orally prior to and after intrastriatal 6-OHDA lesion respectively. A significant recovery in d-amphetamine induced circling behavior (stereotypy), spontaneous locomotor activity, dopamine (DA)-D2 receptor binding, striatal DA and 3-4 dihydroxy phenyl acetic acid (DOPAC) level, nigral glutathione level, lipid peroxidation, striatal superoxide dismutase and catalase activity, antiapoptotic and proapoptotic protein level was evident in BTE + 6-OHDA and 6-OHDA + BTE groups, as compared to lesioned animals. BTE treatment, either before or after 6-OHDA administration protected the dopaminergic neurons, as evident by significantly higher number of surviving tyrosine hydroxylase immunoreactive (TH-ir) neurons, increased TH protein level and TH mRNA expression in substantia nigra. However, the degree of improvement in motor and neurochemical deficits was more prominent in rats receiving BTE before 6-OHDA. Results suggest that BTE exerts both neuroprotective and neurorescue effects against 6-OHDA-induced degeneration of the nigrostriatal dopaminergic system, suggesting that possibly daily intake of BTE may slow down the PD progression as well as delay the onset of neurodegenerative processes in PD.

The effects of enalapril maleate and cold stress exposure on tyrosine hydroxylase activity in some rat tissues.

Enalapril is a highly specific and competitive inhibitor of angiotensin-I converting enzyme (ACE) and thus belongs to the category of ACE inhibitors. The beneficial effects of ACE inhibitors appear to result primarily from the suppression of the plasma renin-angiotensin-aldesterone system. This study was designed to detect the effects of enalapril maleate and cold stress on tyrosine hydroxylase (TH) activity in adrenal medulla, heart and hypothalamus in rat. In cold stress treatment (exposed to 8 degrees C cold for 48 h) TH activity was found to be raised significantly (p < 0.05) in adrenal medulla, hypothalamus and heart tissues. In the adrenal medulla, hypothalamus and heart tissues, TH activity of enalapril maleate treated rats (10 mg kg(-1) body weight) group was not raised significantly (p > 0.05). Following intraperitoneal injection of enalapril maleate (10 mg kg(-1) body weight) the rats were exposed to 8 degrees C cold for 48 h. After cold stress and enalapril maleate treatment no statistically significant change in tyrosine hydroxylase activity was detected in adrenal medulla, hypothalamus or heart (p > 0.05). The results of our studies show that enalapril maleate blocks the effect of cold stress on the regulation of TH activity.

D-lactate increases pulmonary apoptosis by restricting phosphorylation of bad and eNOS in a rat model of hemorrhagic shock.

UNLABELLED: Resuscitation with racemic lactated Ringer's solution (containing equal amounts of D and L isomers of lactate) has been shown to induce pulmonary apoptosis. Substitution of DL-isomer lactate with ketone bodies (beta-hydroxybutyrate, BHB), sodium pyruvate, or L-isomer of lactate decrease this injury without changing the energy status of the tissues or the expression of apoptotic genes. These modified solutions however alter the function of apoptotic proteins through an unknown mechanism. We postulated that DL-LR induces apoptosis by restricting the phosphorylation of key apoptotic proteins. METHODS: Male Sprague Dawley rats (n = 30, 5/group) were subjected to a three stage, volume-controlled hemorrhage and randomized to the following groups. 1) No hemorrhage (Sham); 2) Hemorrhage and no resuscitation (NR); 3) Resuscitation with 3x shed blood volume of racemic LR (DL-LR); 4) Resuscitation with 3x shed blood volume of LR containing only the L-isomer of lactate (L-LR); 5) Resuscitation with 3s shed blood volume of pyruvate Ringer's (PR); 6) Resuscitation with 3s shed blood volume of ketone Ringer's (KR). The modified Ringer's solutions were identical to racemic LR except for equimolar substitution of DL-lactate for L-lactate, pyruvate and BHB respectively. Lung tissue was obtained 2 hours later and subjected to Western Blotting. The levels of Akt, Bad, and eNOS (total and phosphorylated) proteins were measured. Finally, the expression of gene coding for protein 14-3-3 was measured using RT-PCR. RESULTS: Resuscitation with DL-LR caused a significant (p < 0.05) increase in the total Bad and a decrease in phosphorylated Bad protein expression in the lung. It also caused an increase in the phosphorylated Akt levels and a decrease in gene coding for protein 14-3-3. These changes were consistent with signaling imbalances that favor apoptosis. Modified LR solutions, on the other hand, did not cause these alterations. Phosphorylation pattern of eNOS supported the involvement of PI3K/Akt pathway in this process. CONCLUSION: Racemic lactate plays a role in the induction of pulmonary apoptosis by restricting phosphorylation of Bad and eNOS proteins.

Angiotensin II regulates tyrosine hydroxylase activity and mRNA expression in rat mediobasal hypothalamic cultures: the role of specific protein kinases.

Dopamine secreted by hypothalamic neurons is crucial in regulating prolactin secretion from the pituitary. We have examined the ability of angiotensin II (AngII) to regulate the activity of these dopaminergic neurons and thus act as a potential physiological regulator of prolactin secretion. Using a hypothalamic cell culture preparation we determined the effect of AngII on tyrosine hydroxylase activity and expression (TOH). This is important because TOH is the rate-limiting enzyme in dopamine biosynthesis. AngII stimulated a time- and concentration-dependent increase in TOH activity which was suppressed by inhibitors able to act on protein kinase A (PKA), protein kinase C (PKC) and Ca(2+)/calmodulin-dependent protein kinase II (CaMPKII). An inhibitor of the mitogen-activated protein kinase (MAPK) pathway, PD 98059, reduced basal TOH activity but the AngII response was still detectable. AngII stimulation enhanced the phosphorylation of TOH at Ser19, Ser31 and Ser40. AngII also induced a time-dependent increase in TOH mRNA expression which was unaffected by inhibitors able to act on PKA and CaMPKII, but was abolished by inhibitors able to act on ERK and PKC. AngII responses were very much larger in cultures prepared from female when compared to male rat pups. Data from adult hypothalamic slices confirmed this sexual dimorphism and supported the role of the protein kinases noted above. Therefore AngII can regulate both the activity and expression of TOH in hypothalamic neurons employing multiple, but only partially overlapping, signaling pathways.

In vitro inhibitory effects of bergenin and norbergenin on bovine adrenal tyrosine hydroxylase.

The aqueous extract of Mallotus japonicus (Euphorbiaceae) showed an inhibitory effect on bovine adrenal tyrosine hydroxylase (TH), the rate-limiting enzyme in the biosynthesis of catecholamine. The present study was undertaken to investigate the effects of bergenin and norbergenin, constituents of the aqueous extract of Mallotus japonicus on bovine adrenal TH. Bergenin and norbergenin inhibited the TH activity by 29.0% and 53.4% at a concentration of 20 microg/mL, respectively, and exhibited noncompetitive inhibition of TH activity with the substrate l-tyrosine. The inhibition of TH activity and the inhibitory effect of norbergenin was more potent than that of bergenin. From these results, it is presumed that bergenin and norbergenin may be the active components of Mallotus japonicus in inhibiting TH, and these inhibitory effects may be partially responsible for the clinical use of Mallotus japonicus in treating peptic ulcer by reducing the availability of dopa/dopamine in vivo.

Neuroprotective effects of (+/-)-kavain in the MPTP mouse model of Parkinson's disease.

This is the first study to investigate the potential protective effects of the lipophilic kavapyrone (+/-)-kavain in the experimental MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) model of Parkinson's disease (PD). Male C57BL/6 mice were treated with (+/-)-kavain (50, 100, or 200 mg/kg i.p.) or vehicle 60 min before and 60 min after a single administration of MPTP (30 mg/kg s.c.) or saline, respectively. Mice were sacrificed after 7 days and the neostriatum was analyzed for dopamine and its metabolites using HPLC with electrochemical detection. Furthermore, nigral sections were processed for tyrosine hydroxylase (TH) immunocytochemistry. To determine the effects of (+/-)-kavain (200 mg/kg) on MPTP metabolism, HPLC analysis of striatal MPP(+) (1-methyl-4-phenylpyridinium) levels was performed. MPTP treatment alone led to a significant depletion of striatal dopamine levels to 12.61% of saline controls. The lower dosages of (+/-)-kavain (50 and 100 mg/kg) showed only a nonsignificant attenuation of MPTP-induced dopamine depletion, but a high dosage of (+/-)-kavain (200 mg/kg) significantly antagonized the dopamine depletion to 58.93% of saline control values. Remarkably, the MPTP-induced decrease of TH-immunoreactivity as well as the loss of nigral neurons was completely prevented by (+/-)-kavain (200 mg/kg). Striatal MPP(+) levels were not altered by (+/-)-kavain treatment. In conclusion, we found that MPTP metabolism was not influenced by (+/-)-kavain and postulate the antiglutamatergic effects of (+/-)-kavain for its protective effects against MPTP toxicity. (+/-)-Kavain may be a novel candidate for further preclinical studies in animal models of PD and other disorders with glutamatergic overactivity.

Effects of acute and chronic gonadectomy on the catecholamine innervation of the cerebral cortex in adult male rats: insensitivity of axons immunoreactive for dopamine-beta-hydroxylase to gonadal steroids, and differential sensitivity of axons immunoreactive for tyrosine hydroxylase to ovarian and testicular hormones.

Previous studies have shown that gonadectomy in adult male rats induces a complex series of region- and time-specific changes in the density of presumed cerebral cortical dopamine axons that are immunoreactive for tyrosine hydroxylase. The present study asked whether noradrenergic cortical afferents also show hormone sensitivity by assaying axons immunoreactive for the enzyme dopamine-beta-hydroxylase in representative areas of acutely and chronically gonadectomized and sham-operated adult male rats. Catecholamine afferents (both tyrosine hydroxylase-immunoreactive and dopamine-beta-hydroxylase-immunoreactive) were also quantified in gonadectomized rats supplemented with testosterone propionate, with 17-beta-estradiol, or with 5-alpha-dihydrotestosterone. Analyses of noradrenergic (dopamine-beta-hydroxylase) afferents revealed no differences in axon appearance or density among the hormonally intact and hormonally manipulated groups. However, analyses of tyrosine hydroxylase immunoreactivity revealed an unexpected division of labor among ovarian and testicular hormones in ameliorating the effects of acute verses chronic hormone deprivation on these afferents. Estradiol replacement attenuated the decreases in immunoreactivity induced by acute gonadectomy, but was ineffective in suppressing changes in immunoreactivity stimulated by chronic gonadectomy. In contrast, supplementing gonadectomized animals with dihydrotestosterone provided no protection from acute decreases in innervation, but fully attenuated both the supragranular decreases and infragranular increases in tyrosine hydroxylase-immunoreactive axon density that mark the association cortices of chronically gonadectomized rats. Together these findings indicate both long- and short-term effects of gonadectomy on cortical catecholamines, principally target dopamine afferents, and that chronic gonadectomy, which selectively disturbs dopamine innervation in the prefrontal cortices, involves a compromise in androgen signaling pathways.

Influence of androgen on tyrosine hydroxylase mRNA in adrenal medulla of spontaneously hypertensive rats.

We investigated the effects of castration and testosterone propionate on tyrosine hydroxylase mRNA, its activity, and catecholamine synthesis in the adrenal medulla of spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY). Four-week-old male rats were castrated. Testosterone propionate (500 micrograms per rat) was administered subcutaneously twice a week to castrated rats (between 14 and 25 weeks of age). Systolic pressure was measured at the age of 25 weeks, and rats were decapitated. The systolic pressure of castrated SHR was significantly lower than that of control and testosterone-replaced SHR. Epinephrine and norepinephrine levels, tyrosine hydroxylase activity, and tyrosine hydroxylase mRNA in the adrenal medulla of castrated SHR were significantly lower than in control and testosterone-replaced SHR. Systolic pressure and epinephrine and norepinephrine levels, tyrosine hydroxylase activity, and tyrosine hydroxylase mRNA levels in the adrenal medulla of WKY showed no significant differences among the control, castrated, and testosterone-replaced groups. These results suggest that androgens contribute to the development and maintenance of hypertension in SHR via sustained enhancement of tyrosine hydroxylase synthesis in the adrenal medulla, leading to increased epinephrine and norepinephrine levels.

Effects of gentamicin on catecholamine levels in the striatum, hypothalamus, adrenal gland and vas deferens.

The effects of gentamicin, an aminoglycoside antibiotic, on changes in the catecholamine levels in the rat striatum, hypothalamus, adrenal medulla and vas deferens were studied. When rats were i.v. injected with gentamicin (1.0 mg/kg), the catecholamine content of all tissues increased 2-4 h after injection. The increases in catecholamine levels induced by gentamicin were about 1.4- to 2.3-fold those induced by saline. The effect of gentamicin was observed at 0.1 or 0.5 mg/kg, and was maximal at 2.0 mg/kg. The activity of tyrosine hydroxylase, a rate-limiting enzyme in catecholamine biosynthesis, was markedly increased in all four tissues of rats treated with gentamicin (1.0 mg/kg, 4 h). However, direct addition of gentamicin to the tyrosine hydroxylase assay medium did not affect tyrosine hydroxylase activity. These data indicate that gentamicin administration to rats increases the catecholamine content of both central and peripheral catecholamine-containing tissues. The results also suggest that the effect of gentamicin is due to an indirect activation of tyrosine hydroxylase.

[Enhanced resistance to emotional stress through the use of D-phenylalanine]. / Povyshenie ustoichivosti k émotsional'nomu stressu s pomoshch'iu D-fenilalanina.

Stress-protective action was studied of D-phenylalanine, having an ability to decrease destruction of endogenic enkefalins. In the experiments stability of the experimental (receiving D-phenylalanine) and control groups of male rats of August line to emotional stress was compared in conditions of immobilization stress by parameters of animals survival rate, adrenal glands hypertrophy development, involution of thymus, pathologic changes in lungs (abscesses development), ulcero-dystrophic disturbances in stomach, and also the activity and kinetic properties of enzyme tyrosin-hydroxylase in the hypothalamus were determined. It was shown that by several of the mentioned physiological parameters the D-phenylalanine significantly increased the animals stability to the emotional stress and decreased tyrosinhydroxylase activity which participates in activation of katecholaminergic processes.

Sex-related alterations in hypothalamic tyrosine hydroxylase after neonatal monosodium glutamate treatment.

This study compared tyrosine hydroxylase (TH) mRNA signal levels, relative quantity of TH protein, and the catalytic activity of TH in the tuberoinfundibular dopaminergic neurons (TIDA) of male and ovariectomized (OVEX) female rats. In addition, the effects of monosodium glutamate (MSG) neurotoxicity on these parameters of TH regulation were evaluated. Neonatal rats were injected with MSG (4 mg/g body weight) or 10% sodium chloride (controls) on alternate days for the first 10 days of life. Females were ovariectomized on day 45 of age, and all rats were used between 60 and 80 days of age. The TH mRNA signal levels, as assessed by an in situ hybridization technique, were 2-fold higher in control females than in control males, whereas the number of TH mRNA-containing cells was similar between sexes. The TH immunostainings of the TIDA perikarya in the arcuate nucleus and of the nerve terminals in the median eminence were qualitatively more intense in females than males. The catalytic activity of TH, as determined by in vitro DOPA accumulation in the stalk-median eminence, was 3-fold greater in females than males. Neonatal MSG-treatment resulted in a marked reduction in the number of TH mRNA-containing cells and TH-immunopositive cells in the arcuate nucleus of both sexes, as well as a decrease in the intensity of TH immunostaining in the median eminence. The cellular mRNA signal levels for TH were markedly reduced in females after MSG treatment, but were unchanged in males. MSG treatment reduced TH activity to 20% of control levels in females, but did not alter enzyme activity in males.(ABSTRACT TRUNCATED AT 250 WORDS)