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Biomedical subjects

G Carta

Publications and source records attributed to G Carta.

At least 55 records · Page 3Linked to original sources
PubMed1999

Colposcopy, cytology and histology in the diagnosis of squamous intraepithelial lesions of the cervix.

OBJECTIVE: To compare colposcopic findings to cytologic and histological diagnoses in women with colposcopic reports of ANTZ and/or HPV infection. METHODS: Among 791 hospitalized women referred for colposcopic examination, colposcopy showed ANTZ grade 0-2 and/or HPV infection in 271 patients (34.26%). Only 153 were fully investigated by colposcopy, cytology (under colposcopic observation) and histology (target punch biopsy: 109 patients; surgical specimens of hysterectomy: 42 patients; conization: 2 patients). Cytological and histological diagnoses were reported according to the Bethesda System. RESULTS: 132/153 Pap smears were estimable for sampling adequacy; 44/63 resulted as normal and were histologically positive for LSIL [1]. Five LSIL-positive Pap tests were negative on histology (false negative and false positive rate of 33.33% and 3.78%). The pap test was diagnostic for intraepithelial neoplasia in 34/65 cases (53.3%) and for invasive cancer in 6/11 cases (54.5%). In 67/132 cases (50.8%) adequate-for-sampling Pap smears could not predict the exact diagnosis. On the other hand, 108/141 patients with colposcopic evidence of ANTZ/cancer showed histological SIL or invasive neoplasm (76.59%): ANTZ 1 was associated to LSIL and HSIL in 74.1% and 2.4%; ANTZ 2 to LSIL, HSIL and invasive cancer in 41%, 30.76% and 10.3%. Colposcopic suspicion of invasive cancer in 8 patients was histologically demonstrated in 7 (87.5%); colposcopic diagnosis of HPV infection was confirmed in 10/12 (83.4%). CONCLUSION: A better correspondance was shown between colposcopy and histology than between cytology and histology in the diagnosis of SIL. We suggest a routine colposcopy investigation for all patients admitted to a gynecological clinic and we believe it is very important to take Pap smears under colposcopic observation if colposcopy and cervical smears are performed in the same sitting.

Adult↗
PubMed1999

Adsorptive control of water in esterification with immobilized enzymes. Continuous operation in a periodic counter-current reactor.

A periodic counter-current adsorptive-reactor system is developed to carry out continuous esterifications in organic solvents with immobilized enzymes. The system comprises a number of fixed-beds distributed between a reaction-adsorption zone and a regeneration zone and operated in a "merry-go-round" sequence. Water formed in the reaction is adsorbed preventing the formation of a free-water phase and deactivation of the biocatalyst. The adsorbed water is, in turn, recovered by desorption in the regeneration zone. The concept is tested experimentally on a laboratory-scale using, as a model, the esterification of isoamyl alcohol and propionic acid in hexane catalyzed by an immobilized lipase. Pure isoamyl alcohol is used as a regenerant to remove excess water from the biocatalyst. In the periodic steady-state, improvements in ester productivity greater than 50% over that achievable with a conventional fixed-bed reactor are demonstrated experimentally with just two beds in a series arrangement. Use of a water-selective adsorbent in conjunction with the biocatalyst provides further improvements by reducing accumulation of water on the enzyme. A mathematical model is also developed to predict the thermodynamic activity of water along the reactor and describe the dynamic behavior of the system. The model, based on independently developed rate and equilibrium parameters, successfully predicts the experimental behavior and provides an effective tool for scale-up and optimization.

Adsorption↗
PubMed1999

[Fetal malformations and chromosome abnormalities diagnosed at the Center of Prenatal Diagnosis of the University of Aquila in the 1995-1998 triennium].

BACKGROUND: Over the past few years numerous techniques have been developed, allowing an evaluation of fetal physiopathology that was unthinkable until recently. The authors describe 20 cases of fetal malformations and chromosomal abnormalities diagnosed by scan and amniocentesis at the Centre for Diagnosis and Obstetric Prophylaxis at L'Aquila University. METHODS: Between January 1995 and April 1998 a total of 1180 amniocentesis and 4000 obstetric scans were performed in a group of 1650 pregnant women. RESULTS: Of the patients examined using ultrasound scan, 8 presented manifest fetal pathologies, of which 5 were associated with chromosome abnormalities: 1) left ventricular hypoplasia, common atrium, tricuspid dysplasia; 2) omphalocele; 3) Morgagni-Stewart-Morel syndrome; 4) plurilobate cystic hygroma; 5) duodenal atresia; 6) Dandy-Walker syndrome; 7) cystic hygroma and hydrops; 8) cystic hygroma, hydrops, cardiopathy and Dandy-Walker syndrome. Among the pregnant women undergoing amniocentesis without a prior diagnosis of fetal malformation, 12 presented pathological fetal karyotypes: 2 cases of Turner's syndrome; 2 cases of Edward's syndrome; 2 cases of Klinefelter's syndrome, of deletion of a stretch of chromosome 8; 1 case of Down's syndrome; 2 cases of supernumerary marker chromosome; 1 twin pregnancy with Klinefelter's syndrome in one twin and paracentric inversion of chromosome 13 in the other; 1 twin pregnancy with a small supernumerary marker chromosome in both twins. CONCLUSIONS: Ultrasonography often enables the diagnosis of congenital abnormalities not associated with chromosome pathologies. However, karyotype studies play an essential role in pregnancies with a high genetic risk.

Adult↗
PubMed1999

Preterm delivery: predictive value of cervico-vaginal fetal fibronectin.

OBJECTIVE: This study aimed to evaluate the risk of preterm delivery in the asymptomatic obstetric population of L'Aquila by means of fetal fibronectin immunoassay in cervicovaginal secretions. METHODS: In this prospective study, 60 asymptomatic pregnant women at low-risk for preterm delivery were followed-up. Fetal fibronectin cervical swabs from the esocervix and posterior vaginal fornix were obtained every second week from 24 to 36 weeks of gestation. Fetal fibronectin concentrations were measured by an enzyme-linked immunosorbent assay with a cutoff level set at 50 ng/ml. RESULTS: Twelve patients (20%) had at least one positive fetal fibronectin test result. Six women in our study group (10%) were delivered spontaneously < 37 weeks; 4 of these (66%) had at least one positive fetal fibronectin test result (positive predictive value: 33%; sensitivity: 66%) and 3 of these women (75%) had a positive test result between 24 and 26 weeks. The remaining 8 patients with at least one positive fetal fibronectin test were delivered at term or post-term. Forty-eight women always had negative tests and 46 (95.8%) of these were delivered at term (specificity 82%), whereas 2 (4.2%) were delivered prematurely. The negative predictive value of fetal fibronectin as a predictor of term delivery in this low-risk population in 95% with odds ratio = 11.5 (95% confidence interval 1.44 to 110.4), relative risk = 8 (95% confidence interval 1.38 to 59.2) and Fisher Exact Test p < 0.024. CONCLUSION: In a population of asymptomatic patients at low risk for prematurity, the occurrence of a positive cervical or vaginal fetal fibronectin test result defines a subgroup at increased risk for preterm delivery, mostly at low gestational age.

Adult↗
PubMed1998

Adsorptive control of water in esterification with immobilized enzymes: I. Batch reactor behavior.

Reducing the influence of an undesired product in an enzymatic reaction could have a significant impact on the productivity of such systems. Here, we focus on the removal of water formed during an enzymatic esterification in a batch reactor. A commercial immobilized lipase preparation, known as Lipozyme, is used as the biocatalyst and propionic acid and isoamyl alcohol dissolved in hexane are the substrates. In this system, the water formed will partition between the catalyst and the medium. As the more polar reactants are converted into the less polar ester product, the water is partitioned more towards the biocatalyst and the accumulation of water eventually causes lower reaction rates. Addition of a strong-acid cation exchange resin in sodium form is found to control the water accumulation on the biocatalyst without stripping the essential water needed for the enzyme to function and substantial improvements in conversion are achieved. A mathematical model is developed to describe the batch reaction behavior with and without added absorbent, which successfully predicts the behavior of water and its effects.

Adsorption↗
PubMed1998

Adsorptive control of water in esterification with immobilized enzymes: II. fixed-bed reactor behavior.

Experimental and theoretical studies are conducted to understand the dynamic behavior of a continuous-flow fixed-bed reactor in which an esterification is catalyzed by an immobilized enzyme in an organic solvent medium. The experimental system consists of a commercial immobilized lipase preparation known as Lipozyme as the biocatalyst, with propionic acid and isoamyl alcohol (dissolved in hexane) as the reaction substrates. A complex dynamic behavior is observed experimentally as a result of the simultaneous occurrence of reaction and adsorption phenomena. Both propionic acid and water are adsorbed by the biocatalyst resulting in lower reaction rates. In addition, an excessive accumulation of water in the reactor leads to a rapid irreversible inactivation of the enzyme. A model based on previously-obtained adsorption isotherms and kinetic expressions, as well as on adsorption rate measurements obtained in this work, is used to predict the concentration and thermodynamic activity of water along the reactor length. The model successfully predicts the dynamic behavior of the reactor and shows that a maximum thermodynamic activity of water occurs at a point at some distance from the reactor entrance. A cation exchange resin in sodium form, packed in the reactor as a selective water adsorbent together with the catalyst particles, is shown to be an effective means for preventing an excessive accumulation of water formed in the reaction. Its use results in longer cycle times and greater productivity. As predicted by the model, the experimental results show that the water adsorbed on the catalyst and on the ion exchange resin can be removed with isoamyl alcohol with no apparent loss in enzyme activity.

Adsorption↗
PubMed1998

Inhibition of hippocampal acetylcholine release after acute and repeated Delta9-tetrahydrocannabinol in rats.

The effects of acute and repeated administration of Delta9-tetrahydrocannabinol (Delta9-THC), the psychoactive principle of marijuana, on acetylcholine release in the hippocampus was studied in freely moving rats by microdialysis. The acute intraperitoneal (i.p.) administration of Delta9-THC at the doses of 2.5 and 5 mg/kg reduced acetylcholine release by about 25% and 45%, respectively. A dose of 7.5 mg/kg produced no further reduction. Delta9-THC effects were antagonized by the cannabinoid CB1 antagonist SR141716A at the i.p. dose of 1 mg/kg, per se ineffective in modifying acetylcholine concentrations. After a repeated exposure (twice daily for up to seven days) to Delta9-THC (7.5 mg/kg, i.p.) or vehicle (0.3 ml/kg, i.p.), the inhibitory effect of Delta9-THC (2.5 and 5 mg/kg, i.p) on acetylcholine release was not reduced. The results confirm previous observations that cannabinoids inhibit acetylcholine release through cannabinoid CB1 receptors, and indicate that no tolerance to this effects develops after a repeated Delta9-THC administration.

Acetylcholine↗
PubMed1998

Cannabinoids decrease acetylcholine release in the medial-prefrontal cortex and hippocampus, reversal by SR 141716A.

The effect of delta9-tetrahydrocannabinol, the psychoactive principle of marijuana, and [R-(+)-(2,3-dihydro-5-methyl-3-[[4-morpholinylmethyl]pyrol[1,2,3-d e-]-1,4-benzoxazin-6y)(1-naphthalenyl)methanone monomethanesulfonate] (WIN 55,212-2), a synthetic cannabinoid receptor agonist, on the acetylcholine output in the medial-prefrontal cortex and hippocampus was studied by microdialysis in freely moving rats. The administration of delta9-tetrahydrocannabinol (1 and 5 mg/kg i.p.) and WIN 55,212-2 (5 and 10 mg/kg i.p.) produced a long lasting inhibition of acetylcholine release in both areas. The inhibitory effect of delta9-tetrahydrocannabinol and WIN 55,212-2 was suppressed in both areas by the specific cannabinoid CB1 receptor antagonist, [N-(piperidin-1-yl)-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-me thyl-1H-pyrazole-3carboxamide]HCl (SR 141716A), at the dose of 0.1 mg/kg i.p., per se ineffective to modify basal acetylcholine release. Most interestingly, SR 141716A alone at higher doses increased acetylcholine release both in the medial-prefrontal cortex (3 mg/kg i.p.) and hippocampus (1 and 3 mg/kg i.p.), suggesting that acetylcholine output is tonically inhibited by endogenous cannabinoids. Since the inhibitory effect of delta9-tetrahydrocannabinol is produced by doses within those relevant to human use of marijuana, our results suggest that the negative effects of the latter on cognitive processes may be explained by its ability to reduce acetylcholine release in the medial-prefrontal cortex and hippocampus. Conversely, cannabinoid receptor antagonists may offer potential treatments for cognitive deficits.

Acetylcholine↗
PubMed1998

Rapid increase in basal acetylcholine release in the hippocampus of freely moving rats induced by withdrawal from long-term ethanol intoxication.

The effect of ethanol withdrawal on hippocampal acetylcholine (ACh) release was investigated by brain microdialysis in rats rendered ethanol dependent by repeated forced administration of a 20% ethanol solution for 7 days. The behavioral signs of ethanol withdrawal were accompanied by an increase in hippocampal ACh output that was significantly 6 h after the last ethanol administration, reached a maximum (fourfold) at 12 h, and persisted for >72 h. Administration of diazepam (5 mg/kg, i.p.) or gamma-hydroxybutyrate (1 g/kg, intragastric) 12 h after the last ethanol administration completely antagonized, within 30 min, the increase in ACh output induced by ethanol withdrawal. Thus, the rapid and marked increase in ACh output might contribute to the changes in cognitive function associated with ethanol withdrawal, and the septohippocampal cholinergic system may play a major role in the response to withdrawal of addictive drugs.

Acetylcholine↗
PubMed1998

Asymmetric reduction of acetophenone with calcium-alginate-entrapped Baker's yeast in organic solvents

Baker's yeast cells entrapped in alginate beads are shown to catalyze reactions in organic solvents when a cofactor regeneration scheme is implemented. This study focused on the reduction of acetophenone to 1-phenylethanol, using baker's yeast as well as a cosubstrate to regenerate the cofactor. The product is a chiral alcohol, and it was desired to maintain a high enantiomeric excess. The effects of parameters such as the addition of a cosubstrate, water content, fermentation time, buffer pH, and bead diameter have been investigated. Such a general process may be quite useful when single enantiomers are needed, as well as for the production of other chemicals.

Journal Article↗
PubMed1998

[Tri-test: clinical considerations on 1784 cases].

BACKGROUND: To evaluate the triple screen serum test as a noninvasive screening test for expectant mothers > 35 years old, who are not usually considered for invasive screening for trisomy 21. METHODS: 1784 tri-tests (triple serum screening tests) were performed on expectant mothers between their 15th and 18th week of pregnancy, using the radioimmunological Ria-Kodak with an Alpha program (Logical Medical System LTD) with a cut-off value of 1:350. RESULTS: 244 positive equal to 13.60%. The percentage of false positives was respectively 12.9% (age < 35) and 28% (age > 35). Only in two of these cases did we have a positive response in amniocentesis for a fetus affected with Down syndrome. Of the 1540 patients with a negative tri-test, one woman gave birth to a fetus with Down syndrome. CONCLUSIONS: Our study revealed a sensitivity of 66%. The elevated number of false positives has led us to decide on a variation on the cut off in the future: from 1:350 to 1:300.

Chorionic Gonadotropin↗
PubMed1998

[Pelvic floor rehabilitation in women affected with stress urinary incontinence. Authors' experience].

BACKGROUND: This study evaluated pelvic floor rehabilitation as a possible treatment for urinary stress incontinence: a challenge to tradition. METHODS: In this study 20 female subjects with urinary stress incontinence had rehabilitation therapy, at first in the outpatients clinic with motivated physiotherapists and afterwards by home exercises. RESULTS: At the end of 3 months of training, stress incontinence had disappeared in 7 patients (35%), while an improvement was recorded in 13 (65%). CONCLUSIONS: In summary, pelvic floor rehabilitation program can be an effective alternative to surgical approach in reducing the frequency of urinary leakage. Further studies are needed to identify factors predicting success and to improve the techniques of pelvic floor rehabilitation.

Aged↗
PubMed1997

Direct evidence for antioxidant effect of Bcl-2 in PC12 rat pheochromocytoma cells.

Mock-transfected PC12 rat pheochomocytoma cells and PC12 cells transfected with the bcl-2 gene, a gene associated with inhibition of apoptosis, were subjected to oxidative stress by incubation in the presence of the azo-initiator of lipid peroxyl radicals, 2,2'-azobis(2,4-dimethylvaleronitrile) (AMVN). Extraction and chromatographic analysis by two-dimensional TLC of the major phospholipid classes showed no differences in the phospholipid composition between the mock- and bcl-2-transfected cell lines after incubation in the presence of 0.5 mM AMVN for 2 h at 37 degrees C. A method consisting of incorporation of cis-parinaric acid into the constituent membrane phospholipids before exposure to AMVN was developed to improve the sensitivity of detecting lipid peroxidation in PC12 cells. Analysis of the pattern of changes in parinaric acid-labeled phospholipids after exposure to 0.25 and 0.5 mM AMVN by HPLC showed significant oxidation of phosphatidylcholine (PC), phosphatidylethanolamine (PEA), phosphatidylserine (PS), phosphatidylinositol (PI), and sphingomyelin (SPH) during a 2-h incubation. The extent of oxidation of each phospholipid class was dependent on the concentration of AMVN present up to 1 mM. Based on phospholipid fractional composition, the specific rates of PnA peroxidation in phospholipid classes were estimated. In mock-transfected PC12 cells, the order of AMVN-induced oxidation effectiveness was the same for both specific rates and relative rates: PC >> PEA > PS > SPH > PI. While a dramatic decrease in both relative and specific oxidation rates was observed for all phospholipid classes in bcl-2-transfected PC12 cells, the specific oxidation rates were higher for aminophospholipids (PEA and PS) than for other phospholipids. This suggests that antioxidant protection by bcl-2-related product(s) may be phospholipid-specific and that aminophospholipids are relatively less protected than the other phospholipids. The vitamin E analogue, 2,2,5,7,8-pentamethyl-6-hydrochromane, acted as an effective antioxidant in preventing oxidation of parinaric acid-labeled membrane phospholipids during incubation in the presence of AMVN and the extent of protection was approximately the same in both cell lines. Since, unlike the agents used to generate oxidative stress in other studies, temperature-driven generation of peroxyl radicals by AMVN is not dependent on intracellular metabolism, the results presented provide proof for antioxidant protection, rather than abrogation of radical generation afforded by bcl-2 transfection of PC12 cells.

Animals↗
PubMed1997

Inhibition of hippocampal acetylcholine release by cannabinoids: reversal by SR 141716A.

Two synthetic cannabinoids, WIN 55,212-2 {R-(+)-(2,3-dihydro-5-methyl-3-[{4-morpholinylmethyl]pyrol [1,2,3-de]-1,4-benzoxazin-6-yl)(1-naphthalenyl)methanone monomethanesulfonate} (5.0 and 10 mg/kg i.p.) and CP 55,940 {[1a,2-(R)-5-(1.1-dimethylheptyl)-2-[5-hydroxy-2-(3-hydroxypropyl) cyclohexyl]-phenol} {[1a,2-(R)-5-(1,1-dimethylheptyl)-2-[5-hydroxy-2-(3-hydroxypropyl) cyclohexyl]-phenol} (0.5 and 1.0 mg/kg i.p.), inhibited acetylcholine release in the rat hippocampus. The inhibition was prevented by the cannabinoid receptor antagonist, SR 141716A {N-(piperidin-1-yl)-5-(4- chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide} HCl, at the dose of 0.1 mg/kg i.p. Higher doses of SR 141716A (1.0 and 3.0 mg/kg i.p.) themselves increased hippocampal acetylcholine release, suggesting that acetylcholine output is tonically inhibited by endogenous cannabinoids. The results also suggest that the negative effects of marijuana on learning and memory may depend on cannabinoid receptor-mediated inhibition of acetylcholine release.

Acetylcholine↗
PubMed1997

Peroxidase-catalyzed oxidation of beta-carotene in HL-60 cells and in model systems: involvement of phenoxyl radicals.

Recent studies provide extensive evidence for the importance of carotenoids in protecting against oxidative stress associated with a number of diseases. In particular, reactions of carotenoids with phenoxyl radicals generated by peroxidase-catalyzed one-electron metabolism of phenolic compounds may represent an important antioxidant function of carotenoids. To further our understanding of the antioxidant mechanisms of carotenoids, we used in the present work two different phenolic compounds, phenol and a polar homologue of vitamin E (2,2,5,7,8-pentamethyl-6-hydroxychromane, PMC), as representatives of two different types of phenols to study reactions of their respective phenoxyl radicals with carotenoids in cells and in model systems. We found that phenoxyl radicals of PMC did not oxidize beta-carotene in either HL-60 cells or in model systems with horseradish peroxidase (HRP)/H2O2. In contrast, the phenoxyl radicals generated from phenol (by native myeloperoxidase in HL-60 cells or HRP/H2O2 in model systems) effectively oxidized beta-carotene and other carotenoids (canthaxanthin, lutein, lycopene). One-electron reduction of the phenoxyl radical by ascorbate (assayed by electron spin resonance-detectable formation of semidehydroascorbyl radicals) prevented HRP/H2O2-induced oxidation of beta-carotene. PMC, but not phenol, protected beta-carotene against oxidation induced by a lipid-soluble azo-initiator of peroxyl radicals. No adducts of peroxidase/phenol/H2O2-induced beta-carotene oxidation intermediates with phenol were detected by high-performance liquid chromatography-mass spectrometry analysis of the reaction mixture. Since carotenoids are essential constituents of the antioxidant defenses in cells and biological fluids, their depletion through the reaction with phenoxyl radicals formed from endogenous, nutritional and environmental phenolics, as well as phenolic drugs, may be an important factor in the development of oxidative stress.

Chromatography, High Pressure Liquid↗
PubMed1997

[Cervical maturation and induction of labor with PgE2 gel. Authors' experience].

BACKGROUND: To evaluate the efficacy and safety of intracervical prostaglandin E2 gel applications (PgE2) for cervical ripening and induction of labor in relation to parity and admission cervical score. MATERIALS AND METHODS: One hundred and thirty-nine hospitalized patients with an unfavorable cervix (Bishop score < or = 4) received a dose of commercially available endocervical dinoprostone gel 0.5 mg. On the basis of cervical scores, the gel was reapplied at a 12-hour interval for a maximum of two doses. If cervical ripening was successful (Bishop score > 4) but labor did not start within 12 hours from the last dose of gel, labor was induced with oxytocin infusion or with 1 or 2 doses of intravaginal dinoprostone. RESULTS: Intracervical gel was effective for preparing an unfavorable cervix in 87.1% of patients. In 53.1% of nulliparous with admission Bishop < or = 2 the interval between the first application of gel and delivery was higher than 24 hours whereas in all patients with parity > or = 1 and initial Bishop score between 3 and 4 delivery was achieved within 24 hours. The cesarean delivery rates in the two groups were 23.9% and 43% respectively. CONCLUSIONS: The interval from the first application of gel to delivery is strongly influenced by parity and initial cervical score. Vaginal delivery can be expected in four fifths of patients with an unfavorable cervix who undergo pre-induction cervical ripening with prostaglandin E2 gel.

Adolescent↗
PubMed1996

Reduction of dopamine release and synthesis by repeated amphetamine treatment: role in behavioral sensitization.

Changes in extracellular dopamine concentration in the ventral striatum during repeated amphetamine administration and over the first 7 days of withdrawal were studied by transversal microdialysis in freely moving rats. 2 days after fiber implantation rats were treated with either amphetamine (1.5 mg/kg i.p.) or saline every 12 h for 14 days. In amphetamine-treated rats, the baseline extracellular dopamine concentration, preceding the morning treatment, increased from 0.43 +/- 0.01 on day 1 up to 0.59 +/- 0.02 pmol/40 microliters sample on day 3 of treatment. Thereafter, dopamine fell rapidly on day 5(0.16 +/- 0.01 pmol/40 microliters) and remained at approximately the level reached on day 7(0.11 +/- 0.01 pmol/40 microliters) throughout the treatment and also over the 7 days of withdrawal. In contrast, in control rats, the extracellular dopamine concentration (0.40 +/- 0.01 pmol/40 microliters, on day 1) decreased progressively during the first days of treatment to reach a fairly stable value on day 4 (0.25 +/- 0.01 pmol/40 microliters sample). Thereafter, dopamine remained stable at this level throughout the remaining period of experimentation. Challenge with amphetamine (1.5 mg/kg i.p.) of animals treated with amphetamine for 10 days or withdrawn for 7 days produced a potentiated motor response compared to that in control rats but much less marked dopamine releasing effects. Dopamine synthesis in the ventral striatum, measured as L-dihydroxyphenylalanine formation after blockade of dihydroxyphenylalanine decarboxylase, was found to be reduced by approximately 60% after 2 weeks of amphetamine treatment and in animals withdrawn for 1 day or 7 days. These results indicate that repeated amphetamine treatment causes persistent inhibition of dopamine synthesis and release in the ventral striatum. Such inhibition may be a compensatory response to the repeated stimulation of postsynaptic dopamine receptors by the endogenously released dopamine and also the cause of postsynaptic sensitization to dopamine action.

Amphetamine↗