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I Mocchetti

Publications and source records attributed to I Mocchetti.

71 records · Page 4Linked to original sources
PubMed1985

Use of mRNA hybridization and radioimmunoassay to study mechanisms of drug-induced accumulation of enkephalins in rat brain structures.

The repeated administration of haloperidol or fenfluramine for several days led to an increase of enkephalin content in specific brain areas. In order to characterize the nature of the dynamic changes underlying this increase, we measured the content of proenkephalin mRNA (PE-mRNA), of high molecular weight (HMW) enkephalin precursors, and of low molecular weight enkephalin peptides (LMW) in various brain areas. To measure PE-mRNA, we hybridized the specific mRNA with a [32P]cDNA probe for human pheochromocytoma PE. HMW and LMW enkephalin content was measured by radioimmunoassay after separation of the immunoreactive peaks by Bio-Gel P-2 column chromatography and enzymatic digestion of the precursors. Haloperidol treatment increased enkephalins, the precursor, and PE-mRNA content in the striatum, suggesting that this drug might increase enkephalin steady state by increasing transcription, translation, or both processes. In contrast, fenfluramine increased hypothalamic and striatal enkephalin content by preferentially reducing neuropeptide utilization or decreasing its catabolism without changing its synthesis.

Animals↗
PubMed1985

Reserpine changes the dynamic state of enkephalin stores in rat striatum and adrenal medulla by different mechanisms.

The administration of reserpine increases enkephalin content in rat striatum and adrenal medulla. In order to investigate the mechanisms operative in this increase, we have studied in vivo the dynamic state of enkephalin stores by determining the content of proenkephalin mRNA, enkephalin precursors, and enkephalins in rats receiving reserpine. We measured proenkephalin mRNA by using a cDNA probe for human proenkephalin mRNA which hybridizes to the same species of mRNA either in the brain or in adrenal medulla. (Met5)-Enkephalin-Arg6-Phe7, as well as the high and low molecular weight forms of the enkephalins separated by Sephadex G-75 column chromatography, were measured by radioimmunoassay. Reserpine (2 mg/kg, i.p., repeated daily for two consecutive days) led 3 to 5 days later to an increase in the striatal content of proenkephalin mRNA as well as high and low molecular weight peptides containing enkephalin. The same treatment produced, in adrenal medulla, a shift from higher molecular weight to lower molecular weight enkephalin-containing peptides, an increase of enkephalin peptides, and a decrease of proenkephalin mRNA content. The results in striatum suggest that reserpine increases enkephalin synthesis by removing a tonic dopaminergic inhibition: those in adrenal medulla indicate that reserpine causes an accumulation of enkephalins by blocking the release and/or increasing the processing which may trigger a feedback-regulatory mechanism leading to a decrease in proenkephalin mRNA content.

Adrenal Medulla↗
PubMed1984

A reduction of the tone of 5-hydroxytryptamine neurons decreases utilization rates of striatal and hypothalamic enkephalins.

The administration of drugs such as fenfluramine, p-chlorophenylalanine or 5,7-dihydroxytryptamine, which lower brain 5-hydroxytryptamine content, increases the enkephalin content of hypothalamus and striatum. None of these treatments changes proenkephalin mRNA content. On the basis of these results, we propose that 5-hydroxytryptamine does not increase the biosynthesis of enkephalin, but might increase the content of the neuropeptide by reducing peptide utilization.

5,7-Dihydroxytryptamine↗
PubMed1984

Enkephalin biosynthesis in adrenal medulla. Modulation of proenkephalin mRNA content of cultured chromaffin cells by 8-bromo-adenosine 3',5'-monophosphate.

Incubation of primary cultures of chromaffin cells from bovine adrenal medulla with 8-bromo-adenosine 3',5'-monophosphate (8-Br-cyclic AMP) resulted in an increase in proenkephalin mRNA content. The mRNA that increased was detected by hybridization analysis using a cDNA probe and migrated with an apparent size of approximately 1400 bases. The increase in proenkephalin mRNA following 8-Br-cyclic AMP treatment was apparent in 12 hr and continued over 2 days. Corresponding changes were detected in enkephalin-like immunoreactivity but with a 24-hr lag: the cellular content increased significantly after 2 days of treatment and continued to rise over the next 2 days, whereas changes in the amount released to the medium followed the same time course. Dose-response curves for the increase in the content of proenkephalin mRNA and of enkephalin-containing peptides were essentially identical. Chromatographic characterization of the enkephalin-like peptides demonstrated that 8-Br-cyclic AMP increased both the high molecular weight fraction and the low molecular weight fraction, which was shown by high-pressure liquid chromatography to contain Met5-enkephalin, Leu5-enkephalin, and Met5-enkephalin-Arg6-Phe7. Previous results in chromaffin cells have demonstrated that the synthesis of tyrosine hydroxylase is also regulated by cyclic AMP, with a similar time course. These results therefore suggest the possibility of coordinate regulation by cyclic AMP of the expression of the cotransmitters, catecholamines and enkephalin peptides, in the adrenal medulla.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1983

Cyclic nucleotides in experimental and human brain tumors.

It is well known that the system of cyclic nucleotides plays an important role in cell differentiation and proliferation. Cyclic AMP is capable of stimulating cell growth, and cyclic GMP is thought to control cell division and growth. The authors measured adenylcyclase activity (AC) and cGMP content in the tumor latency period and in early neoplastic proliferations in rats with brain tumors induced by transplacental ethylnitrosourea (ENU). AC activity, which is high during the first days of life, decreases until it reaches, at the 60th day, levels lower than those in control animals. Cyclic GMP, on the contrary, increases during the first month in treated animals and remains consistently higher than controls up to the 45th day. In fully developed experimental brain tumors (mixed gliomas, isomorphic and polymorphic oligodendrogliomas) the percentage of reduction in AC activity is significantly higher. AC activity was measured also in human tumoral tissue. In malignant tumors it is markedly lower than in benign tumors. In the same patients cAMP in the cerebrospinal fluid was measured with results similar to those obtained in tissues. These findings confirm that the system of cyclic nucleotides is implicated in all the developmental phases of brain tumors and therefore may reveal how research can clarify the first transformations of tumoral cells.

Adenylyl Cyclases↗
PubMed1983

Behavioural and biochemical effects in the adult rat after prolonged postnatal administration of clozapine.

Rats were administered 10 mg/kg SC of clozapine (C) or vehicle solution (S) daily from day 1 after birth until 20 days of age. At 60 days of age (40 days after the postnatal treatment with C or S was interrupted) the stereotyped behaviour and the effects on locomotor activity elicited by apomorphine in S- and C-pretreated rats were investigated. The intensity of stereotyped behaviour as well as the decrement in locomotion induced by apomorphine (0.5--1 mg/kg SC) were not influenced by chronic C administration during development. Finally, at 80 days of age (60 days after the postnatal treatment with C or S was interrupted) rats were subjected to a differential reinforcement of low rates schedule (DRL15s). The results indicate that the acquisition of the DRL task performance criterion (Rs/Rf less than or equal to 2.5) was significantly more rapid in S-pretreated rats than in C-pretreated ones. In parallel biochemical experiments, homovanillic acid (HVA) content was measured in striatum in rats at 60 days of age (40 days after the postnatal treatment with C or S was interrupted). The results indicate that even if an acute challenge dose of 10 mg/kg C shows a certain degree of tolerance a single dose of 20 mg/kg C is still able to increase striatal HVA concentration in chronic C-pretreated animals. These data indicate that early postnatal administration of a non-cataleptogenic neuroleptic, like C, induces, in the adult rat, behavioural and biochemical changes which significantly differ from those elicited by a cataleptogenic neuroleptic, like haloperidol.

Animals↗
PubMed1983

Temporal sequence of changes in central noradrenergic system of rat after prolonged antidepressant treatment: receptor desensitization and neurotransmitter interactions.

It has been shown that different receptor components may be involved in the adaptive changes occurring in noradrenergic (NE) neurones after prolonged periods of exposure to antidepressant drugs. In this report the desensitization of NE-coupled adenylate cyclase (NE-AC). beta-adrenergic receptors and [3H]imipramine ([3H]-IMI) or [3H]desipramine ([3H]-DMI) binding sites have been temporally correlated with in vivo changes of NE utilization. Normetanephrine (NMN) was measured as indicator of NE synaptic events involved in antidepressant action. Concentrations of normetanephrine were increased after acute desipramine (DMI), viloxazine and mianserin administration. Following 3 days of treatment, the antidepressant-induced increase of normetanephrine became tolerant and NE neurones were resistant to the antidepressant effect until the 15th day of treatment. After two weeks, DMI elicited a significant decrease in the content of normetanephrine. A different pattern of changes has been found in the temporal modification of [3H]-IMI recognition sites, beta-adrenoceptors and NE-AC activity after chronic DMI treatment. Binding sites and receptors were down regulated after 10 days of treatment preceding the decrease in normetanephrine content. No down-regulation was observed in [3H]-DMI binding sites. Studies on the effects of antidepressants during brain maturation revealed that the mechanisms which cause desensitization of beta-receptors and [3H]-IMI binding sites appear in the early stages of postnatal life. Since [3H]-IMI and [3H]-DMI recognition sites have been shown to be located on serotonergic (5-HT) and noradrenergic neurones respectively, the interactions between NE and 5-HT neurones could represent possible mechanisms implicated in receptor desensitization. The experiments presented involving lesions of 5-HT neurones have clearly demonstrated that NE release in rat cerebral cortex is under a tonic serotonergic influence. Alterations in the chemico-physical properties of the synaptic membranes might be also taken in consideration for the mechanisms underlying receptor modulation. In fact, evidence is provided that in neural tissue phospholipid methylation can be affected. In conclusion, the temporal sequence of changes in cortical noradrenergic neurones, after chronic antidepressant treatment, has demonstrated that integrated mechanisms are operative for the function of the overall system.

Animals↗
PubMed1981

Enduring behavioural and biochemical effects in the adult rat after prolonged postnatal administration of haloperidol.

Rats were administered 0.5 mg/kg SC of haloperidol (H) or saline (S) daily from day 1 after birth until 20 days of age. At 60 days of age (40 days after the postnatal treatment with H or S was interrupted) the stereotyped behaviour and the effects on locomotor activity elicited by apomorphine in S- and H-pretreated rats were investigated. The intensity of apomorphine (0.5--1 mg/kg, SC)-induced stereotyped behaviour was significantly greater in the H-pretreated group than in S-pretreated animals and this was accompanied by a much more marked reduction of locomotor activity in H-pretreated than in S-pretreated rats. Finally, at 80 days of age (60 days after the postnatal treatment with H or S was interrupted) rats were subjected to a Differential Reinforcement of Low Rates schedule (DRL 15-s). The results indicate that the acquisition of the DRL task performance criterion (Rs/Rf less than or equal to 2.5) was significantly more rapid on S-pretreated rats than in H-pretreated ones. In parallel biochemical experiments, acute H produced smaller increases in dopamine turnover in chronic H-treated rats compared with S-treated controls. These data indicate that H treatment in neonatal rats induces behavioural and biochemical changes which can be observed up to 60 days after H withdrawal.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1981

Postmortem changes of normetanephrine determined by a mass-fragmentographic technique in different rat brain areas.

A specific and sensitive gas chromatographic-mass spectrometric assay for measurement of normetanephrine (NMN) in different rat brain regions is presented. The results show that hypothalamus contains the highest concentrations of the norepinephrine metabolite. An increase of NMN concentrations has been detected in animals killed by decapitation in comparison with microwave-irradiated rats. This finding has to be taken into consideration when NMN is measured in the brain in order to assess the functional activity of noradrenergic neurons.

Animals↗
PubMedDate not supplied

Biological activity of interleukin-10 in the central nervous system.

Cytokines play a crucial role as mediators of inflammation. Astrocytes and microglia are the two major glial cells involved in the central nervous system immune responses. In this study we examined the effects of interleukin-10 (IL-10), one of the naturally occurring inhibitory cytokines, on different types of glial cells in culture such as rat astrocytes, hamster microglia and C6-2B glioma cells. Phosphorylation of signal transducers and activators of transcription (STAT) proteins was used as a marker for IL-10 activity. Within minutes, IL-10 elicited a strong and weak increase in STAT3 and STAT1 phosphorylation, respectively, in human T lymphocytes, suggesting that STAT3 is a main IL-10 signaling event in these cells. In contrast, IL-10 failed to induce STAT3 in glial cells, but elicited a weak increase in STAT1 phosphorylation in microglia and C6-2B glioma cells only, suggesting that in some glial cell population(s) IL-10 may produce cellular responses via activation of the STAT1 pathway. Moreover, in C6-2B cells, IL-10 elicited a decrease in the level of basic fibroblast growth factor mRNA. A similar decrease was observed in adult rat hypothalamus, indicating that this cytokine may regulate glial production of trophic factors. Our data suggest that IL-10 may play a role in glial cell differentiation and proliferation.

Acute-Phase Proteins↗
PubMedDate not supplied

Pharmacology of neuronal gene expression.

Pharmacological treatments were used to estimate trans-synaptic regulation of opioid peptide gene expression occuring at specific neurotransmitter receptors. In vitro and in vivo studies have shown that different signal-transduction mechanisms regulate the transcription of proenkephalin, proopiomelanocortin and nerve growth factor mRNA. The activation of receptors coupled to adenylate cyclase elicited the increase of proenkephalin and nerve growth factor gene expression. Therefore, a cAMP-dependent mechanism was suggested to be involved in such regulation. However, the temporal delay between the elevation of the intracellular cAMP content and the increase in nerve growth factor and proenkephalin mRNAs prompted us to investigate whether additional mechanisms associated with the second messenger were operative in the regulation of the expression of these two genes. We report evidence that a protein(s), probably functioning as a trans-acting factor, might be involved in the regulation of nerve growth factor gene transcription. The characterization and isolation of these DNA regulatory proteins will provide the pharmacologist with valuable information for the development of new compounds in the therapy of mental disorders.

Animals↗
PubMedDate not supplied

Engraftment of C6-2B cells into the striatum of ACI nude rats as a tool for comparison of the in vitro and in vivo phenotype of a glioma cell line.

The C6-2B is a well-characterized glioma cell line used extensively in the study of malignant glial biology. While the C6-2B cell line has traditionally been thought of as a homogenous cell line, the in vitro phenotype of the C6-2B cell line can vary considerably depending on the culture technique used and the stratum on which the cells are grown. Thus, we asked whether the in vitro phenotype of the C6-2B cell line was significantly different than the in vivo phenotype of the cell line once it was engrafted into the striatum of nude rats. Under culture conditions used in our laboratory, 100% of the C6 cells were found to express p75, the low-affinity nerve growth factor (NGF) receptor, and Major Histocompatability Class I (MHC Class I), while only 10-15% demonstrated vimentin reactivity. Immunohistochemistry was consistently negative for GFAP, trkA (the high-affinity receptor for NGF), CD4, CD8, and a macrophage specific marker (Ox-41). Once engrafted into the striatum of nude rats, the cells remained 100% p75 and MHC Class I positive, and again, only 15% of the cells demonstrated vimentin reactivity. The grafted cells retained this characteristic for 28 days in vivo. Although an immunoincompetent host was selected to minimize the effects an inflammatory response would have on the graft, a transient inflammatory response was detected. During the first week of engraftment, numerous MHC class II cells, some of which were macrophages, were seen infiltrating the graft. However, by 4 weeks postengraftment, no inflammatory cells were appreciated in the graft and surprisingly little reactive gliosis was seen in the penumbra of the tumor mass. Thus, the limited number of in vitro phenotypic characteristics we examined in the C6-2B cell line remained constant once the cells were engrafted into the striatum of athymic nude rats.

Animals↗