2-Cys peroxiredoxins contribute to thylakoid lipid unsaturation by affecting ω-3 Fatty Acid Desaturase 8

Fatty acid unsaturation levels affect chloroplast function and plant acclimation to environmental cues. However, the regulatory mechanism(s) controlling fatty acid unsaturation in thylakoid lipids is poorly understood. Here, we have investigated the connection between chloroplast redox homeostasis and lipid metabolism by focusing on 2-Cys peroxiredoxins (Prxs), which play a central role balancing the redox state within the organelle. The chloroplast redox network relies on NADPH-dependent thioredoxin reductase C (NTRC), which controls the redox balance of 2-Cys Prxs to maintain the reductive activity of redox-regulated enzymes. Our results show that Arabidopsis (Arabidopsis thaliana) mutants deficient in 2-Cys Prxs contain decreased levels of trienoic fatty acids, mainly in chloroplast lipids, indicating that these enzymes contribute to thylakoid membrane lipids unsaturation. This function of 2-Cys Prxs is independent of NTRC, the main reductant of these enzymes, hence 2-Cys Prxs operates beyond the classic chloroplast regulatory redox system. Moreover, the effect of 2-Cys Prxs on lipid metabolism is primarily exerted through the prokaryotic pathway of glycerolipid biosynthesis and Fatty Acid Desaturase 8 (FAD8). While 2-Cys Prxs and FAD8 interact in leaf membranes as components of a large protein complex, the levels of FAD8 were markedly decreased when FAD8 is overexpressed in 2-Cys Prxs-deficient mutant backgrounds. These findings reveal a function for 2-Cys Prxs, possibly acting as a scaffold protein, affecting the unsaturation degree of chloroplast membranes.

Resistance to deltamethrin in Triatoma infestans (Hemiptera: Reduviidae): does it influence the phenotype of antennae, wings, and heads?

In vector control terms, insecticide resistance is the development of the capacity, of an insect population, to tolerate doses of an insecticide that are lethal to most individuals in a typical population of the same species. The genetic changes that determine resistance may have adaptive costs in the resistant phenotype or, conversely, may result in an adaptive advantage when compared to susceptible insects in the environment without insecticides. Triatoma infestans is one of the main vectors of Trypanosoma cruzi in the southern cone of South America. High insecticide resistance in T. infestans was detected in Argentina in Salta and Chaco provinces. The objective of this study was to determine the possible morphometric changes in wings, heads, and the antennal phenotype of deltamethrin-resistant T. infestans (RR) males and females compared to susceptible insects (SS), evaluating its implication in adaptive processes such as olfactory capacity, dispersion, and probability of colonizing new habitats, among others. Nine type I landmarks were marked on wings, 5 type II landmarks on heads, and 10 antennal sensilla were counted on 106 adults of both sexes (resistant and susceptible from first and second laboratory generations). Morphological divergence was observed between the two groups (RR and SS). The RR insects showed smaller sizes of wings and heads and shape compatible with lower dispersal potential and different active dispersal behaviors. Antennae also revealed sensory simplification in RR and divergence between RR and SS, although more marked in females. This study characterizes for the first time T. infestans RR and SS through wings, heads, and antennae. The results suggest a lower dispersive potential in resistant insects and the differences described lay the foundations for the identification of a resistance biomarker in triatomines.

Plastid 2-Cys peroxiredoxins are essential for embryogenesis in Arabidopsis

The redox couple formed by NADPH-dependent thioredoxin reductase C (NTRC) and 2-Cys peroxiredoxins (Prxs) allows fine-tuning chloroplast performance in response to light intensity changes. Accordingly, the Arabidopsis 2cpab mutant lacking 2-Cys Prxs shows growth inhibition and sensitivity to light stress. However, this mutant also shows defective post-germinative growth, suggesting a relevant role of plastid redox systems in seed development, which is so far unknown. To address this issue, we first analyzed the pattern of expression of NTRC and 2-Cys Prxs in developing seeds. Transgenic lines expressing GFP fusions of these proteins showed their expression in developing embryos, which was low at the globular stage and increased at heart and torpedo stages, coincident with embryo chloroplast differentiation, and confirmed the plastid localization of these enzymes. The 2cpab mutant produced white and abortive seeds, which contained lower and altered composition of fatty acids, thus showing the relevance of 2-Cys Prxs in embryogenesis. Most embryos of white and abortive seeds of the 2cpab mutant were arrested at heart and torpedo stages of embryogenesis suggesting an essential function of 2-Cys Prxs in embryo chloroplast differentiation. This phenotype was not recovered by a mutant version of 2-Cys Prx A replacing the peroxidatic Cys by Ser. Neither the lack nor the overexpression of NTRC had any effect on seed development indicating that the function of 2-Cys Prxs at these early stages of development is independent of NTRC, in clear contrast with the operation of these regulatory redox systems in leaves chloroplasts.

Multi-laboratory experiment PME11 for the standardization of phosphoproteome analysis

Global analysis of protein phosphorylation by mass spectrometry proteomic techniques has emerged in the last decades as a powerful tool in biological and biomedical research. However, there are several factors that make the global study of the phosphoproteome more challenging than measuring non-modified proteins. The low stoichiometry of the phosphorylated species and the need to retrieve residue specific information require particular attention on sample preparation, data acquisition and processing to ensure reproducibility, qualitative and quantitative robustness and ample phosphoproteome coverage in phosphoproteomic workflows. Aiming to investigate the effect of different variables in the performance of proteome wide phosphoprotein analysis protocols, ProteoRed-ISCIII and EuPA launched the Proteomics Multicentric Experiment 11 (PME11). A reference sample consisting of a yeast protein extract spiked in with different amounts of a phosphomix standard (Sigma/Merck) was distributed to 31 laboratories around the globe. Thirty-six datasets from 23 laboratories were analyzed. Our results indicate the suitability of the PME11 reference sample to benchmark and optimize phosphoproteomics strategies, weighing the influence of different factors, as well as to rank intra and inter laboratory performance.

[C677T polymorphism of the methylentetrahydrofolate reductase gene in mothers of children affected with neural tube defects]

Neural tube defects (NTD) are the most common congenital anomalies of the central nervous system, with a multifactorial pattern of inheritance, presumably involving the interaction of several genetic and environmental factors. The methylenetetrahydrofolate reductase (MTHFR) gene 677C>T polymorphism has been implicated as a risk factor for NTD. The main objective of this research was to investigate the association of the 677C>T polymorphism of the MTHFR gene as a genetic risk factor for NTD. Molecular analysis was performed in DNA samples from 52 mothers with antecedent of NTD offspring and from 119 healthy control mothers. Using the Polymerase Chain Reaction, a 198 bases pairs fragment was digested with the restriction enzyme Hinfi. 677T MTHFR allele frequencies for the problem and the control groups were 51.92% and 34.45%, respectively, and 677C MTHFR allele frequencies were 48.08% and 65.55%, respectively. There were significant differences in allele (p: 0.002) and genotype (p: 0.007) frequencies between these two groups. The odds ratio (OR) to the TT genotype vs. the CC genotype was estimated as OR: 4.9 [95% CI: 1,347-6.416] p: 0.002; CT+TT vs. CC: OR: 2.9 [95% CI: 1.347-6.416] p: 0.005; TT vs. CT+CC: OR: 2.675 [95% CI: 1,111-6.441] p: 0.024. The data presented in this study support the relationship between MTHFR 677C>T polymorphism and risk in mothers with antecedent of NTD offspring.

The evolutionary conserved oil body associated protein OBAP1 participates in the regulation of oil body size

A transcriptomic approach has been used to identify genes predominantly expressed in maize (Zea mays) scutellum during maturation. One of the identified genes is oil body associated protein1 (obap1), which is transcribed during seed maturation predominantly in the scutellum, and its expression decreases rapidly after germination. Proteins similar to OBAP1 are present in all plants, including primitive plants and mosses, and in some fungi and bacteria. In plants, obap genes are divided in two subfamilies. Arabidopsis (Arabidopsis thaliana) genome contains five genes coding for OBAP proteins. Arabidopsis OBAP1a protein is accumulated during seed maturation and disappears after germination. Agroinfiltration of tobacco (Nicotiana benthamiana) epidermal leaf cells with fusions of OBAP1 to yellow fluorescent protein and immunogold labeling of embryo transmission electron microscopy sections showed that OBAP1 protein is mainly localized in the surface of the oil bodies. OBAP1 protein was detected in the oil body cellular fraction of Arabidopsis embryos. Deletion analyses demonstrate that the most hydrophilic part of the protein is responsible for the oil body localization, which suggests an indirect interaction of OBAP1 with other proteins in the oil body surface. An Arabidopsis mutant with a transfer DNA inserted in the second exon of the obap1a gene and an RNA interference line against the same gene showed a decrease in the germination rate, a decrease in seed oil content, and changes in fatty acid composition, and their embryos have few, big, and irregular oil bodies compared with the wild type. Taken together, our findings suggest that OBAP1 protein is involved in the stability of oil bodies.

Contribution of the different omega-3 fatty acid desaturase genes to the cold response in soybean

This study analysed the contribution of each omega-3 desaturase to the cold response in soybean. Exposure to cold temperatures (5 °C) did not result in great modifications of the linolenic acid content in leaf membrane lipids. However, an increase in the GmFAD3A transcripts was observed both in plant leaves and soybean cells whereas no changes in GmFAD3B or GmFAD3C expression levels were detected. This increase was reversible and accompanied by the accumulation of an mRNA encoding a truncated form of GmFAD3A (GmFAD3A-T), which originated from alternative splicing of GmFAD3A in response to cold. When the expression of plastidial omega-3 desaturases was analysed, a transient accumulation of GmFAD7-2 mRNA was detected upon cold exposure in mature soybean trifoliate leaves while GmFAD7-1 transcripts remained unchanged. No modification of the GmFAD8-1 and GmFAD8-2 transcripts was observed. The functionality of GmFAD3A, GmFAD3B, GmFAD3C and GmFAD3A-T was examined by heterologous expression in yeast. No activity was detected with GmFAD3A-T, consistent with the absence of one of the His boxes necessary for desaturase activity. The linolenic acid content of Sacharomyces cerevisiae cells overexpressing GmFAD3A or GmFAD3B was higher when the cultures were incubated at cooler temperatures, suggesting that reticular desaturases of the GmFAD3 family, and more specifically GmFAD3A, may play a role in the cold response, even in leaves. The data point to a regulatory mechanism of omega-3 fatty acid desaturases in soybean affecting specific isoforms in both the plastid and the endoplasmic reticulum to maintain appropriate levels of linolenic acid under low temperature conditions.

The dynamics of the O(1D) + HCl --> OH + Cl reaction at a 0.26 eV collision energy: a comparison between theory and experiment

The dynamics of the O((1)D) + HCl(v = 0, j = 0) --> Cl + OH reaction at a 0.26 eV collision energy has been investigated by means of a quasiclassical trajectory (QCT) and statistical quantum and quasiclassical methods. State-resolved cross sections and Cl atom velocity distributions have been calculated on two different potential energy surfaces (PESs): the H2 surface (Martinez et al. Phys. Chem. Chem. Phys. 2000, 2, 589) and the latest surface by Peterson, Bowman, and co-workers (PSB2) (J. Chem. Phys. 2000, 113, 6186). The comparison with recent experimental results reveals that the PSB2 PES manages to describe correctly differential cross sections and the velocity distributions of the departing Cl atom. The calculations on the H2 PES seem to overestimate the OH scattering in the forward direction and the fraction of Cl at high recoil velocities. Although the comparison of the corresponding angular distributions is not bad, significant deviations with a statistical description are found, thus ruling out a complex-forming mechanism as the dominant reaction pathway. However, for the ClO + H product channel, the QCT and statistical predictions are found to be in good agreement.

Petty-Laxova-Wiedemann progeroid syndrome: further phenotypical delineation and confirmation of a rare syndrome of premature aging

A 10-year-old boy with manifestations of Petty-Laxova-Wiedemann progeroid syndrome (PLWPS), a rare neonatal progeroid condition, is described and compared with those previously reported. Clinical manifestation include: severe pre- and postnatal growth retardation, "progeroid" face, large open fontanelle in infancy, umbilical hernia at birth, pseudomacrocephaly, wide calvaria, sparse scalp hair, markedly diminished subcutaneous fat, scoliosis, partial cutaneous syndactyly, aplastic and hypoplastic distal phalanges with aplasia and hypoplasia of nails, undescended testes, and normal cognitive and motor development. This appears to be one of only a handful of cases of PLWPS reported in an older child or adult.

[C677T polymorphism of the methylentetrahydrofolate reductase gene as risk factor in women with recurrent abortion]

The pathogenesis of recurrent spontaneous abortion is multifactorial, presumably involving the interaction of several genetic and environmental factors. The methylenetetrahydrofolate reductase (MTHFR) gene C677T polymorphism has been implicated as risk factor for recurrent spontaneous abortion (RA). The main objective of this research was to investigate the association between the C677T polymorphism of the MTHFR gene as a genetic risk factor for idiopathic RA. Molecular analysis was performed in 80 DNA samples from 30 patients with RA and among 50 healthy control subjects. Using the Polymerase Chain Reaction (PCR), a 198 bp (bases pairs) fragment, was digested with the restriction enzyme Hinf1, which can recognize the C > T substitution responsible for the polymorphism. 677T MTHFR allele frequencies for group with RA and the control group were 35% and 33%, respectively and 677C MTHFR allele frequencies were 65% and 67%, respectively. There was no significant difference in allele frequency between these two groups. The data presented in this study fail to support the relationship between MTHFR C677T polymorphism and risk in women with RA.

[Indirect prenatal molecular diagnostic of haemophilia A and B]

Haemophilia A (HA) and B (HB) are the most common inherited bleeding diseases. HA and HB are X-linked recessive disorders caused by mutation in the factor VIII gene which maps to Xq28 and factor IX located at Xq27, respectively; resulting in absence or deficiency of these proteins. Several mutations have been reported as responsible for the disturbance of these genes; therefore, the use of direct molecular techniques to analyze the carrier status of women and their affected fetuses in not easy to perform. Thus, gene linked polymorphisms analysis is the most convenient molecular test since it is independent from the nature of the mutation, allowing the identification of the mutant X chromosome by following its segregation along the pedigree. The main objective of this research was to perform the molecular diagnosis of HA or HB carrier status in pregnant women and male fetuses affected or not, who were referred to the Medical Genetic Unit of the University of Zulia (UGM-LUZ), Maracaibo, Venezuela. Molecular analysis for HA and HB was performed in 32 DNA samples from 8 pregnant women, 8 fetuses, 8 affected and 8 healthy males. Using the Polymerase Chain Reaction (PCR), a 142 bp (bases pairs) fragment, which corresponds to intron 18 of the Factor VIII gene, was amplified. This fragment has a restriction polymorphism for the enzyme Bcl I. Additionally, a Duplex PCR was performed for the STRs (short tandem repeat) of introns 13 and 22 of the same gene. On the other hand, Hinf I, Xmn I y Taq I polymorphism in the factor IX gene were also amplified, so, we were able to build the haplotypes for each one of the key members in the families affected. The latter, allowed us to identify, in five of the eight cases, the mutant X chromosome responsible of HA and HB, thus, prenatal diagnosis was possible with the following results: three healthy males fetuses, two affected males fetuses with HA and three females fetuses.

Colocalization of CB1 receptors with L1 and GAP-43 in forebrain white matter regions during fetal rat brain development: evidence for a role of these receptors in axonal growth and guidance

There is recent evidence supporting the notion that the cannabinoid signaling system plays a modulatory role in the regulation of cell proliferation and migration, survival of neural progenitors, neuritic elongation and guidance, and synaptogenesis. This assumption is based on the fact that cannabinoid 1-type receptors (CB(1) receptors) and their ligands emerge early in brain development and are abundantly expressed in certain brain regions that play key roles in these processes. We have recently presented in vivo evidence showing that this modulatory action might be exerted through regulating the synthesis of the cell adhesion molecule L1 that is also a key element for those processes. To further explore this issue, we conducted here immunohistochemical studies aimed at determining the cellular substrates of CB(1) receptor-L1 interactions in the rat brain during late fetal development. In this period, we previously found that the activation of CB(1) receptors increased L1 synthesis in several forebrain white matter regions but not in gray matter areas. Using double labeling studies, we observed here colocalization of both proteins in fiber tracts including the corpus callosum, the adjacent subcortical white matter, the internal capsule and the anterior commissure. Experiments conducted with cultures of fetal rat cortical nerve cells revealed that L1 is present mainly in neurons but not in glial cells. This fact, together with the results obtained in the double labeling studies, would indicate that L1 and CB(1) receptors should possibly be present in axons elongating through these white matter tracts, or, alternatively, in migrating neurons. Further experiments confirmed the presence of CB(1) receptors in elongating axons, since these receptors colocalized with growth-associated protein 43 (GAP-43), a marker of growth cones, but not with synaptophysin, a marker of active synaptic terminals, in the same forebrain white matter regions. Lastly, using cultured fetal rat cortical neurons, we also observed that the activation of cannabinoid receptors increased the levels of the full-length L1 and altered those of some active proteolytic fragments of this protein whose generation has been associated with specific steps in the process of neuritic elongation in cultured neurons. In summary, we have demonstrated that the effects caused by cannabinoid agonists on L1 are facilitated by the colocalization of this cell adhesion molecule with CB(1) receptors in several forebrain white matter regions during fetal brain development. We have provided strong evidence that this phenomenon occurs in axons elongating through these white matter tracts, and we have explored in vitro how cannabinoid receptors influence L1 levels. Considering the role played by L1 in different events related to neural development, our observations support the occurrence of a physiological mechanism by which the cannabinoid system might regulate the process of axonal growth and guidance through regulating the synthesis and function of L1.

[Autism, chromosome 15 and the GAbaergic dysfunction hypothesis]

Autism is a complex neurodevelopmental disorder characterized by impairment of social interaction, language, communication, and stereotyped, repetitive behavior. Genetic predisposition to autism has been demonstrated from families and twin studies. Despite recent advances in identifying some susceptibility candidate genes, its underlying neurological mechanism is uncertain. There are genetic, biochemical and neuropathological findings that support the hypothesis that autism could be caused by GABAergic dysfunction and it is partially responsible for the etiology of this disorder. One of the most studied genome regions is the 15q11-q13, where the genes that encode for beta3, alpha5 and gamma3 subunits of the GABAA receptor are located. This review demonstrates evidence that involves this region in autism susceptibility and its likely relation with the hypothesis of GABAergic dysfunction.

[Characterization of neuronal ceroid lipofuscinosis in Venezuelan children]

INTRODUCTION

Neuronal ceroid lipofuscinosis (NCL), represents a group of inherited neurodegenerative disorders. Based on the age of the patient at onset, clinical course and ultrastructural morphology it has been identified three clinical types for the pediatric group: 1) Infantile NCL (INCL); 2) Late infantile NCL (LINCL); and 3) Juvenile NCL (JNCL). Other variants or atypical forms represent around 20% of the NCL in different populations. Genetic advances have made possible a better characterization, diagnostic and classification of these disorders.

CASE REPORTS

We present the clinical, neurophysiological, neuroradiological, and morphological data from 6 patients with NCL, who were assessed at the pediatric neurology department of the Hospital Universitario de Maracaibo during a ten years period (1993 2003). All 6 cases corresponded with the late infantile form. Age of onset ranged form 2 to 5 years. For most of the patients initial symptoms included seizures, psychomotor delay, accompanied by macular degeneration and optic atrophy. The EEG was characterized by high voltage spikes elicited by low frequency photic stimulation, in 5 cases. Neuroimaging findings were characteristic of the late infantile form of the NCL. In three patients a decreased intensity of signal was seen in the thalami and putamen on T2-weighted images. The ultrastructural examination of the samples obtained through a biopsy showed curvilinear bodies in all patients.

CONCLUSION

There is not epidemiological data of the NCL in Venezuela; it is presumed the presence of clinical forms and variants in the pediatric group. This first study could contribute to the knowledge and a better research of this group of disorders in our population.

[Carrier detection of Duchenne/Becker muscular dystrophy by analysis of STRs loci linked to the gene of dystrophin in Venezuelan families]

The Duchenne/Becker Muscular Dystrophy (DMD/BMD) is an X linked recessive lethal disease. The female carrier will transmit the disease gene to half of her sons and half of her daughters; half of the daughters will be carriers, while half will be normal. Half of the sons will be normal and, on average, half will have the disease. It is of particular relevance to be able to detect carrier status among female relatives of the patients for genetic counseling and prenatal diagnosis. The method of Short Tandem Repeat (STR) sequence polymorphism analysis can determine haplotype at normal status or at risk status and, to establish genetic linkage between the mutated gene and the segregated haplotype. We have analyzed 105 members from 15 unrelated Venezuelan families with one or more siblings affected with DMD/DMB and 7 unrelated males. Of the 105, 37 were male (26 affected and 11 normal) and 68 were female. STR sequences (STR44, STR45, STR49, STR50, STR3'DYS) of the gene of the Dystrophin were amplified by polymerase chain reaction (PCR) to analyze allelic polymorphism in the families. Five of the 15 families (33%) had a deletion of one or several of the exons. Of the 68 females, 27 (39.7%) were carriers, 27 (39.7%) were non-carriers and in 14 cases (20.58%) it was not possible to reach a definitive diagnosis. The definitive diagnosis could be established in 79% of the females. This analysis also shows that the mutation occurred on the grandpaternal X chromosome in one family. Hemizygocity was detected and carrier status ascertained in the mother of other patient and in one family we were able to do prenatal diagnosis. The germinal mosaicism could not be excluded in 3 patients.

Bioactive compounds from Iostephane heterophylla (Asteraceae)

The novel bisabolene sesquiterpenes 3-6, were isolated from Iostephane heterophylla, using bioguided fractionation. The new compounds were determined to be (12R/12S)-12,13-epoxy-xanthorrhizols (3,4) and (12R/12S)-12,13-dihydro-12,13-dihydroxy-xanthorrizols (5,6) and their structures were characterized by analysis of spectroscopic data and by chemical correlation from xanthorrhizol (2). The stereochemistry at C-12 of 5 was deduced using the modified Mosher experiment. Some of the isolated compounds elicited activity against gram positive and gram negative bacteria, levadura and dermatophytes.

Short- and long-term effects of atorvastatin, lovastatin and simvastatin on the cellular metabolism of cholesteryl esters and VLDL secretion in rat hepatocytes

The short- and long-term in vitro effects of the hydroxymethylglutaryl-CoA reductase inhibitor atorvastatin, compared with lovastatin and simvastatin on VLDL secretion, and on the formation and the neutral and acid lysosomal hydrolysis of cholesteryl esters was investigated in rat liver hepatocytes maintained in suspension (2 or 4 h) or cultured in monolayers (24 h). All statins time-dependently reduced [14C]oleate incorporation into cholesteryl esters, but when exogenous cholesterol was added only atorvastatin caused an immediate transient decrease in hepatocyte ACAT activity. Activity of the lysosomal, microsomal and cytosolic CEH isoforms was unaffected by the hepatocyte treatments. Statins reduced free and esterified cholesterol mass in hepatocyte microsomes after 2 h, and this was followed by a modest decline in VLDL cholesteryl esters, whilst secretion of VLDL apoB and triglycerides was unaltered. However, after 24 h of treatment, statins caused generalized 20-40% decreases in the secretion of VLDL apoB, cholesterol and triglycerides, with the reduction in apoB48 secretion being significantly superior to that caused in apoB100. The mean diameter of secreted VLDL was not modified by either duration or drug treatment. Additional studies with subcellular fractions demonstrated that statins have a direct selective effect on the enzymes governing the cholesterol-cholesteryl ester cycle, with the exception of the microsomal CEH. Atorvastatin, lovastatin and simvastatin inhibited ACAT activity in microsomes by 50% at doses of 250, 100 and 50 microM, respectively. The cytosolic CEH elicited a biphasic profile of activity with activations up to 100 microM statin and inhibitions above 250 microM, and the lysosomal CEH was only inhibited by atorvastatin at a dose of 100 microM or more. We conclude that a prolonged, but not a short, limited availability of hepatocyte cholesterol derived from the endogenous synthesis reduces VLDL secretion, and that reactivity of statins at the cellular level are more similar than reactivity at the subcellular level as regards the cholesterol-cholesteryl ester cycle.

The endogenous cannabinoid system and brain development

Cannabinoid receptors and their endogenous ligands constitute a novel modulatory system that is involved in specific brain functions, such as nociception, control of movement, memory and neuroendocrine regulation. Recently, it has also been suggested that this system is involved in brain development. Studies have used a variety of techniques to elucidate the effects of cannabinoids during development, as well as to characterize the presence of elements of the endogenous cannabinoid system (receptors and ligands) in the developing brain. Collectively, they suggest that endocannabinoids participate in brain development through the activation of second-messenger-coupled cannabinoid receptors.

Role of endocannabinoids in brain development

In addition to those functions that have been extensively addressed in this special issue, such as nociception, motor activity, neuroendocrine regulation, immune function and others, the endogenous cannabinoid system seems to play also a role in neural development. This view is based on a three-fold evidence. A first evidence emerges from neurotoxicological studies that showed that synthetic and plant-derived cannabinoids, when administered to pregnant rats, produced a variety of changes in the maturation of several neurotransmitters and their associated-behaviors in their pups, changes that were evident at different stages of brain development. A second evidence comes from studies that demonstrated the early appearance of elements of the endogenous cannabinoid system (receptors and ligands) during the brain development. The atypical location of these elements during fetal and early postnatal periods favours the notion that this system may play a role in specific molecular events related to neural development. Finally, a third evidence derives from studies using cultures of fetal glial or neuronal cells. Cannabinoid receptors are present in some of these cultured cells and their activation produced a set of cellular effects consistent with a role of this system in the process of neural development. All this likely supports that endocannabinoids, early synthesized in nervous cells, play a role in events related to development, by acting through the activation of second messenger-coupled cannabinoid receptors.

Localization of mRNA expression and activation of signal transduction mechanisms for cannabinoid receptor in rat brain during fetal development

In the present work, we analyzed cannabinoid receptor mRNA expression, binding and activation of signal transduction mechanisms in the fetal rat brain or in cultures of fetal neuronal or glial cells. Cannabinoid receptor binding and mRNA expression were already measurable at GD14, but they were only located in discrete regions at GD16. Among these, the hippocampus, the cerebellum and the caudate-putamen area, three regions that contain a marked signal for both binding and mRNA in the adult brain. Significant levels of binding and, in particular, of mRNA transcripts were also detected at GD16 in the cerebral cortex, midbrain and brainstem. These structures contain relatively low levels of binding and mRNA in the adult brain, suggesting that cannabinoid receptor gene is transiently expressed in atypical areas during the fetal period. The signal for cannabinoid receptor mRNA in the hippocampus, caudate-putamen and cerebral cortex progressively increased from GD16 up to GD21. At GD18 and GD21, mRNA transcripts could be measured in discrete nuclei, such as septum nuclei, ventromedial hypothalamic nucleus and others. The cerebral cortex exhibited the highest mRNA levels at GD21, although this was not accompanied by a parallel increase in binding. An important aspect is that binding measured at these ages represent binding to functional receptors because their activation by WIN-55,212-2 increased [35S]GTPgammaS binding in the same areas. This increase was reversed by a specific antagonist, SR141716. The areas where the stimulation was more marked were the midbrain and brainstem. Using cell cultures, we have observed that cannabinoid receptor mRNA is present in cortical and hippocampal neuronal cells, but not in the glial cells. However, WIN-55,212-2 was capable of stimulating [35S]GTPgammaS binding in membrane fractions obtained from cortical glial cells and this stimulation was reversed by SR141716. This was not seen with hippocampal glial cell cultures, but occurred in hippocampal and cortical neurons. In addition, the activation of these receptors with Delta9-tetrahydrocannabinol significantly reduced forskolin-stimulated cAMP production in cortical neuronal or glial cell cultures and this effect was reversed by SR141716. In summary, we have detected cannabinoid receptor binding, mRNA expression and activation of signal transduction mechanisms in the fetal rat brain (GD14-GD21), which support the view that the system constituted by these receptors and their putative endogenous ligands might play a role in specific molecular events of the brain development. Of relevance is that binding and mRNA expression appear atypically distributed in the fetal brain as compared with the adult brain, even, that their presence in white-matter-enriched areas might presumably indicate their location in non-neuronal cells. These studies with cell cultures suggest that CB1 receptor subtype is located in neuronal cells obtained from fetal brain, although preliminary evidence is provided of the existence of another receptor subtype operative in glial cells obtained from the cerebral cortex.

Protein phosphatase 1 and 2A inhibitors activate acyl-CoA:cholesterol acyltransferase and cholesterol ester formation in isolated rat hepatocytes

Okadaic acid, calyculin A and cantharidin, potent and specific inhibitors of protein phosphatases 1 (PP1) and 2A (PP2A), stimulated both acyl-CoA:cholesterol acyltransferase (ACAT) activity and cholesterol ester formation in suspension cultures of isolated rat hepatocytes. The activation of microsomal ACAT was marked (up to 14-fold the basal values), fast in onset (within 5 min), persistent in duration (up to 45 min) and concentration-dependent. Concentrations of okadaic acid (OA) or calyculin A > or = 100 nM or of cantharidin > or = 1 microM were required to stimulate enzyme activity, which specifically points to a dominant contribution of PP1. No effects were seen with up to 1 microM nor-okadaone, an inactive OA analogue. Rises in [3H]oleate incorporation into cell cholesteryl esters closely paralleled those in ACAT activity, though were somewhat less accentuated. The increases in microsomal ACAT activity seen in OA-, calyculin A- or cantharidin-treated hepatocytes were not linked to changes in bulk microsomal unesterified cholesterol or in the de novo cholesterol synthesis. The findings firmly indicate a role for protein phosphatase activity, probably that of PP1, in controlling the cholesterol esterification rate and ACAT activity in intact rat hepatocytes, which is not secondary to an alteration of the steady-state distribution of cholesterol mass between cell membranes. However, as the OA-induced stimulation of ACAT was not abrogated by addition of purified PP1 or PP2A to microsomes, it is unlikely that the phosphatase inhibitors here used act directly on the phosphorylation degree of the ACAT enzyme.

delta 9-Tetrahydrocannabinol increases activity of tyrosine hydroxylase in cultured fetal mesencephalic neurons

The exposure of pregnant rats to delta 9-tetrahydrocannabinol (delta 9-THC), the main psychoactive constituent of Cannabis sativa, during gestation and lactation, affects the gene expression and the activity of tyrosine hydroxylase (TH) in the brain of their offspring, measured at fetal and early postnatal ages, when the expression of this enzyme plays an important role in neural development. In the present article, we have examined whether delta 9-THC is able to affect TH activity in cultured mesencephalic neurons obtained from fetuses at gestational d 14. Thus, TH activity increased approximately twofold in cells obtained from naive fetuses when exposed for 24 h to medium containing delta 9-THC. In addition, TH activity was also approx twofold higher in cells obtained from fetuses exposed daily to delta 9-THC from d 5 of gestation than in cells obtained from control fetuses, when both were exposed to basal media. This effect of delta 9-THC on TH activity seems to be produced via the activation to cannabinoid receptors, in particular the CB1 subtype, which would presumably be located in these cells. This is because the exposure to medium containing both delta 9-THC and SR141716A, a specific antagonist for CB1 receptors, abolished the effect observed with delta 9-THC alone. SR141716A alone was without effect on TH activity. Collectively, our results support the notion that delta 9-THC increased TH activity in cultured mesencephalic neurons, as previously observed in vivo, and that this effect was produced by activation of CB1 receptors, which seem to be operative at these early ages. All this points to a role for the endogenous cannabimimetic system in brain development.

Stimulation of microsomal cholesterol ester hydrolase by glucagon, cyclic AMP analogues, and vasopressin in isolated rat hepatocytes

Short-term activation of microsomal cholesterol ester hydrolase by glucagon, cAMP analogues, and vasopressin in isolated rat hepatocytes is described. Glucagon led to a dose- and time-dependent activation of cholesteryl oleate hydrolysis, but values returned to basal levels within 120 min. Exposure of isolated hepatocytes to 0.5 mM concentrations of dibutyryl-cAMP or 8-[4-chlorophenylthio]-cAMP, or 25 microM forskolin caused persistent activation of cholesterol ester hydrolase activity after a lag period of 30 min. The three agents resulted in early marked intracellular accumulation of cAMP that declined progressively, and moderate and sustained reductions in the diacylglycerol content. The actions of glucagon on hepatocytes were inhibited by pretreatment of cells with 10 nM [8-arginine] vasopressin. Vasopressin elicited a consistent and sustained increase in cholesterol ester hydrolase activity and diacylglycerol without affecting cAMP while reducing the effect of glucagon on cAMP. Furthermore, the effects of glucagon and vasopressin on the activation of cholesterol ester hydrolase were not additive despite the similarity of their stimulation of diacylglycerol formation. Blockade of vasopressin-mediated activation of cholesterol ester hydrolase and diacylglycerol content were induced by excess prazosin. These data suggest that stimulation of microsomal cholesterol ester hydrolase in isolated liver cells may involve at least two signal transduction systems.

The integrity of thiol groups is essential for catalytic efficiency of rat liver cholesterol ester hydrolase either in microsomal membranes or after solubilization

Neutral cholesterol ester hydrolase from rat liver microsomes was inactivated in a dose and time-dependent manner by classical sulphydryl-reacting reagents such as p-hydroxymercuribenzoic acid, 5,5'-dithio-bis-(2-nitrobenzoic acid), N-ethylmaleimide, or iodoacetate. The concentrations at which half-maximal inhibition of the native microsomal cholesterol ester hydrolase occurred (IC50) were 15, 68, and 370 mumol/l and 68 mmol/l, respectively. Only partial reactivation of the enzyme was observed under excess dithiothreitol or mercaptoethanol treatment. The stimulation of cholesterol ester hydrolase by the metal ions Ca2+ and Mg2+ was dependent on the integrity of the thiol groups. Solubilization of cholesterol ester hydrolase from membranes preserved its sensitivity towards sulphydryl reagents and thiols, as well as its ability to be activated by Ca2+ and Mg2+. Dithiothreitol, mercaptoethanol, and Ca2+ and Mg2+ provided total protection of the enzyme against inactivation by thiol-reacting reagents. The results indicate that one or more thiol groups are either at the active centre of the native and solubilized forms of rat liver microsomal cholesterol ester hydrolase or are sufficiently near, to interfere with the catalysis when they are reacted.

The prenatal exposure to delta 9-tetrahydrocannabinol affects the gene expression and the activity of tyrosine hydroxylase during early brain development

We have previously reported that the exposure of pregnant female rats to delta 9-tetrahydrocannabinol (THC) during the perinatal period affected the gene expression and the activity of tyrosine hydroxylase (TH) in the brain of their male offspring. Those studies were done in animals perinatally exposed to THC but tested at peripubertal and adult ages. In the present work, we explored whether these effects also appear during early fetal brain development, when TH expression plays an important role in neuronal development. To this end, TH-mRNA concentrations were measured by Northern blot analysis with a specific TH probe in the brain of fetuses at gestational days 14 and 16 which had been prenatally exposed to THC or vehicle from day 5 of gestation. In parallel, measurements of TH activity and catecholamine contents by HPLC were also done. The results obtained were as follows. The prenatal exposure to THC markedly affected the expression of the TH gene in the brain of fetuses at gestational day 14. Thus, the amounts of TH-mRNA at this age were higher (2-fold) in THC-exposed fetuses than in controls. This corresponded with a marked increase in the activity of this enzyme (3-fold) at this age. Normalization was found in both parameters at gestational day 16. In summary, the prenatal exposure to THC affected the expression of the TH gene and the activity of this enzyme in brain catecholaminergic neurons during early fetal brain development. These results support the notion that cannabinoids are able to act at the level of the gene expression of specific key proteins for brain development.

Modifications of mesolimbic and nigrostriatal dopaminergic activities after intracerebroventricular administration of prolactin

In the present study we examined the effects of intracerebroventricular (i.c.v.) injections of prolactin (PRL) on the presynaptic activity and post-synaptic sensitivity of mesolimbic and nigrostriatal dopaminergic neurons. In addition, the effects of PRL on in vitro release of dopamine (DA) from perifused striatal fragments were examined. Tyrosine hydroxylase (TH) activity and D2 receptor density in the striatum decreased after i.c.v. PRL administration; this was accompanied by an increase in D2 receptor affinity. These effects occurred after i.c.v. administration of PRL to normoprolactinemic rats, although normally they did not appear after administration to animals with pituitary grafting-induced hyperprolactinemia. Thus, in these animals, i.c.v. PRL failed to decrease TH activity and D1 and D2 receptor densities to a significant extent. In the case of D2 receptors, this was probably due to the fact that pituitary grafting-induced hyperprolactinemia itself was able to reduce the density of this receptor. No changes were observed in DA or L-3, 4-dihydroxyphenylacetic acid (DOPAC) contents after i.c.v. administration of PRL to both normo-and hyperprolactinemic animals. Basal and K(+)-evoked DA release in vitro from perifused striatal fragments of normoprolactinemic rats were not affected by the addition of PRL, whereas this hormone enhanced K(+)-evoked DA release when added to perifused striatal fragments from hyperprolactinemic animals. In the limbic forebrain, i.c.v. administration of PRL to normoprolactinemic animals produced a decrease in DA and DOPAC contents and D1 receptor density. Interestingly, none of these effects appeared when PRL was injected to hyperprolactinemic animals. In summary, our results suggest a possible inhibitory role of PRL on the activity of both the nigrostriatal and mesolimbic dopaminergic neuronal systems. These inhibitory effects were reflected in the decreases elicited in a set of neurochemical parameters, indicating either presynaptic activity or postsynaptic sensitivity, after i.c.v.-administered PRL. This observation supports the hypothesis of a possible neuromodulatory role for an extrapituitary PRL on the activity of these neurons, although the fact that most of these effects did not appear when i.c.v. administration was performed in hyperprolactinemic rats also suggests that they are influenced by peripheral PRL levels.

Motor behavior and nigrostriatal dopaminergic activity in adult rats perinatally exposed to cannabinoids

We have recently reported several neurochemical alterations, measured at perinatal and peripubertal ages, in the maturation of nigrostriatal dopaminergic neurons following perinatal hashish exposure. In the present work, we tried to undertake whether these neurochemical changes during ontogeny: a) were accompanied by changes of motor behavior, the main neurobiological process regulated by nigrostriatal dopaminergic neurons; and b) persisted in adulthood, leading to disturbances in the expression of an adult motor activity. To this end, two different experiments were performed. In the first, we examined, by using an actimeter, the ontogeny of spontaneous locomotor activity in immature male and female rats born from mothers perinatally exposed to hashish extract. Results showed a complete absence of significant changes in locomotor activity in females, whereas males presented a constant trend to decrease, although never statistically significant, at all ages studied as a consequence of the perinatal cannabinoid exposure. In the second experiment, we evaluated neurochemical indices--dopamine (DA) and L-3,4-dihydroxyphenylacetic acid (DOPAC) contents, tyrosine hydroxylase (TH) activity, and number and affinity of D1 and D2 dopaminergic receptors in the striatum--and behavioral parameters--spontaneous locomotor activity and spontaneous and induced stereotypic behavior--both indicating nigrostriatal dopaminergic activity, in adult female and male rats perinatally exposed to hashish extract. Results were as follows. The spontaneous locomotor activity, measured in the actimeter, was not affected by perinatal hashish exposure in both adult males and females. This was also seen in an open-field test as measured by total number of sector crossings. However, when differentiated between internal and external sectors hashish-exposed males presented a higher number of external crossings than controls, which did not appear in females. Moreover, several induced stereotypic behaviors, such as self-grooming and shaking induced by water spraying, were also altered by hashish treatment in a sexually dimorphic manner, whereas the number of spontaneous rears and self-grooms, measured in the open-field test, was unchanged. Thus, the frequency of water spraying-induced self-grooming was significantly increased in both males and females perinatally exposed to hashish, although the increase was more marked in males (200.4%) than females (121.2%). In addition, the frequency of shaking was also markedly increased in males but remained unchanged in females. These behavioral effects were paralleled by modifications in striatal neurochemical parameters. Thus, there was a significant increase in the DOPAC/DA ratio, indicating increased presynaptic activity, in females perinatally exposed to hashish, but compensated by a lower density of D1 receptors.(ABSTRACT TRUNCATED AT 400 WORDS)

Regulation of rat liver microsomal cholesterol ester hydrolase by reversible phosphorylation

The regulation of neutral cholesterol ester hydrolase activity by changes in its phosphorylation state was studied in rat liver microsomes. Treatment with cAMP-dependent protein kinase resulted in increased enzyme activity, which was further enhanced by the addition of cAMP and MgATP. Consistent activations were also achieved with MgCl2 and MgATP, the magnesium effect being abolished by ethylenediaminetetraacetic acid and adenosine triphosphate. Cholesterol ester hydrolase was activated twofold by free calcium and Ca2+/calmodulin; this latter effect was blocked by the chelator ethylene-glycol-bis(beta-aminoethyl ether)N,N,N',N'-tetraacetic acid and the calmodulin antagonist trifluoperazine. The phosphatase inhibitors pyrophosphate and glycerophosphate led to marked and dose-dependent increases in esterase activity, whereas okadaic acid elicited no effect. Furthermore, pyrophosphate and okadaic acid did not change the increases in enzyme activity promoted by Ca2+, Ca2+/calmodulin, Mg2+ and MgATP. Cholesterol ester hydrolase was inactivated in a concentration-dependent manner by nonspecific alkaline phosphatases. In cAMP-dependent protein kinase/cAMP- or Ca2+/calmodulin-activated microsomes, a time-dependent loss of activation in cholesteryl oleate hydrolysis was caused by alkaline phosphatase. These findings suggest that microsomal cholesterol ester hydrolase is activated through cAMP and Ca2+/calmodulin phosphorylation, whereas enzyme deactivation is dependent on phosphatase action.

An acute dose of delta 9-tetrahydrocannabinol affects behavioral and neurochemical indices of mesolimbic dopaminergic activity

Cannabinoid consumption has been reported to affect several neurotransmitter systems and their related behaviors. The present study has been designed to examine cannabinoid effects on certain behaviors, which have been currently located in the limbic forebrain, in parallel to their effects on mesolimbic dopaminergic neurons. To this end, male rats treated with an oral dose of delta 9-tetrahydrocannabinol (THC) or vehicle were used 1 h after treatment for two different behavioral tests or neurochemical analyses of mesolimbic dopaminergic activity. Treatments, behavioral tests and sacrifice were performed in the dark phase of photoperiod because it corresponds to the maximum behavioral expression in the rat. Behavioral tests were a dark-light emergence test, which allows measurements of emotional reactivity, and a socio-sexual approach behavior test, which allows measurements of sexual motivation and also of spontaneous and stereotypic activities. Neurochemical analyses consisted of measurements of dopamine (DA) and L-3,4-dihydroxyphenylacetic acid (DOPAC) contents, tyrosine hydroxylase activity, in vitro DA release and number and affinity of D1 receptors in the limbic forebrain. Results were as follows. THC exposure markedly altered the pattern executed by the animals in both tests. Concretely, THC-exposed animals exhibited a low number of visits to an incentive female in addition to high time spent in the vicinity of an incentive male, both observed in the socio-sexual approach behavior test, and an increased emergence latency to go out of a dark compartment in the dark-light emergence test. However, the fact that THC also decreased spontaneous activity and the frequency of rearing and self-grooming behaviors, in addition to the observations of either low total number of visits to both incentive sexual areas or high escape latency to go out of a light compartment, when the animal is placed in this compartment, also suggest the possible existence of an accompanying motor deficit. These behavioral effects were accompanied by increases in DA and DOPAC contents and in D1 receptor density in the limbic forebrain and to a slight decrease in the pattern of K(+)-evoked DA release in vitro from perifused limbic fragments, with no changes in the remaining neurochemical parameters. Collectively, these results allow us to conclude that acute THC markedly altered the behavioral pattern executed by the animals in a socio-sexual approach behavior test and in a dark-light emergence test, presumably indicating loss of sexual motivation and increased emotionality, although also accompanied by motor deficiencies.(ABSTRACT TRUNCATED AT 400 WORDS)

delta 9-Tetrahydrocannabinol affects mesolimbic dopaminergic activity in the female rat brain: interactions with estrogens

In this work, we studied the possible estrogenic modulation of the effects of delta 9-tetrahydrocannabinol (THC) on mesolimbic dopaminergic activity, by examining the effects of an acute dose of this cannabinoid: (i) during the estrous cycle; (ii) after ovariectomy, chronic estrogen-replacement and tamoxifen (TMX)-induced blockade of estrogenic receptors; and (iii) combined with a single and physiological injection of estradiol to ovariectomized rats. THC significantly decreased the density of D 1 dopaminergic receptors and non-significantly increased the L-3,4-dihydroxyphenylacetic acid (DOPAC) content in the limbic forebrain of ovariectomized rats chronically replaced with estrogens. The decrease in D 1 receptors was also produced by TMX, whereas the coadministration of both THC and TMX did not lead to a major decrease. In addition to the trend of THC increasing DOPAC content, this cannabinoid was also able to increase the ratio between DOPAC and dopamine, although this last effect only occurred after coadministration of THC and TMX, which had been ineffective administered individually. All these effects were not seen when THC was administered to normal cycling rats during each phase of estrous cycle and to ovariectomized rats without chronic estrogen replacement or only submitted to a single and acute dose of estradiol. This observation might be related to the fact that the density of limbic cannabinoid receptors increased in chronic estrogen-replaced ovariectomized rats versus normal cycling, ovariectomized or acutely estrogen-treated ovariectomized rats. Interestingly, THC administration in ovariectomized rats was followed by a slight, although significant, increase in tyrosine hydroxylase activity, which was also observed after coadministration of THC with a short-time and acute dose of estradiol. In summary, THC stimulated the presynaptic activity of mesolimbic dopaminergic neurons, but accompanied by a decrease in their postsynaptic sensitivity. These effects did not appear in normal cycling rats being only evident after ovariectomy and chronic estrogen replacement, which might be related to changes in binding characteristics of cannabinoid receptors in this area. Moreover, some of them appeared after TMX-induced blockade of estrogenic cytosolic receptors, which likely suggests the existence of a certain estrogenic modulation of the actions of THC on mesolimbic neurons. On the contrary, coadministration of THC with a single and shortly tested dose of estradiol was always ineffective in modifying THC effects.

Motor disturbances induced by an acute dose of delta 9-tetrahydrocannabinol: possible involvement of nigrostriatal dopaminergic alterations

Exposure to cannabinoids has been reported to affect several neurotransmitter systems and their related behaviors. The present study has been designed to further explore the effects of cannabinoids on motor behavior and test the involvement of nigrostriatal dopaminergic neurotransmission and other neurotransmitters as possible neurochemical targets for these cannabinoid effects. Male rats treated with an oral dose of delta 9-tetrahydrocannabinol (THC), the main psychoactive ingredient of cannabinoid derivatives, or vehicle were used 1 h after treatment for analyses of spontaneous motor and stereotypic activities together with neurochemical analyses of the nigrostriatal dopaminergic activity. Treatments and analyses were performed in the dark phase of photoperiod because it corresponds to the maximum behavioral expression in the rat. Neurochemical analyses were measurements of presynaptic activity--dopamine (DA) and L-3,4-dihydroxyphenylacetic acid (DOPAC) contents, tyrosine hydroxylase (TH) activity, and in vitro DA release--and postsynaptic sensitivity--number and affinity of D1 and D2 receptors--in the striatum. In addition, measurements of 5-hydroxytryptamine (5-HT) and 5-hydroxyindolacetic acid (5-HIAA) contents were also performed to evaluate serotoninergic activity in the striatum. An oral dose of THC produced a loss of spontaneous motor activity, measured in both actimeter and open-field test, and a decrease in the frequency of several stereotypic behaviors, such as rearing and self-grooming. This decrease was correlated to a low number of D1-dopaminergic receptors in the striatum, although neither DA and DOPAC contents nor TH activity and D2 receptors were altered.(ABSTRACT TRUNCATED AT 250 WORDS)

Divalent metal ions as modulators of rat liver microsomal cholesterol esterase

The regulatory properties of the divalent metal ions Mg2+, Ca2+ and Mn2+ on the activity and kinetic behaviour of rat liver microsomal cholesterol esterase were studied in vitro. Mg2+ and Ca2+ exhibited similar concentration and preincubation time-dependent increases in esterase activity, with maximal stimulation at a concentration of 2 mM. However, Mn2+ had no effect at this concentration but displayed a potent inhibitory effect at concentrations above 20 mM. Activation of cholesterol esterase by Mg2+ and Ca2+ was selective in relation to i) the changes that cations produced in the enzyme kinetic constants, and ii) the chelating agents that reversed the metal ion-induced activation. Hence, the maximum rate of cholesterol ester hydrolysis doubled in the presence of Mg2+ and activation was reversed by EDTA, whereas a significant decrease in the apparent Km for cholesterol oleate was found when Ca2+ was added and this effect was blocked by ATP and EGTA. Both cations were able to reactivate cholesterol ester hydrolase activity in metal-depleted microsomes.

Modifications of striatal D2 dopaminergic postsynaptic sensitivity during development of morphine tolerance-dependence in mice

Alterations in the activity of striatal dopaminergic neurons have been implicated in the development of morphine tolerance-dependence in rodents. To further explore this possibility, we examined the activity of these neurons in mice exposed to morphine during 4 days (addiction group) and subsequently treated with naloxone (withdrawal group). The efficiency of opiate treatment was assessed behaviorally. Striatal dopaminergic activity was evaluated by measuring: a) the ratio between the amounts of L-3,4-dihydroxyphenylacetic acid (DOPAC), the main intraneuronal metabolite of dopamine (DA), and the neurotransmitter itself, as an index of presynaptic activity; and b) the number and affinity of D1 and D2 dopaminergic receptors, as well as the amount of their coupled second messenger, cyclic adenosine monophosphate (cAMP), as postsynaptic parameters. Spontaneous motor activity was decreased in chronically morphine-exposed mice. In these animals, the number of striatal D2 receptors also decreased, with no changes in their affinity, whereas the number and affinity of D1 receptors remained unchanged. This hyposensitivity of D2 receptors was paralleled by an increase in the amount of cAMP with a good statistical correlation between both parameters. Treatment with naloxone of morphine-exposed mice resulted in the typical jumping behavior indicative of opiate withdrawal. The differences in D2 receptors between placebo- and morphine-exposed mice disappeared after naloxone-induced opiate withdrawal, although this effect was due more to the inhibitory effect of naloxone on the density of these receptors in placebo-exposed mice rather than to a stimulatory effect in morphine-addicted mice. The morphine-induced increase in cAMP content also disappeared after naloxone treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Early changes in the development of dopaminergic neurotransmission after maternal exposure to cannabinoids

Perinatal exposure to cannabinoid derivatives has been shown to affect brain development. In this work, we studied the changes induced by maternal exposure to cannabinoids during gestation and lactation on the dopaminergic activity in the prosencephalic area of offspring of several days of development. This brain area contains an increasing population of dopaminergic terminals from the different dopaminergic pathways that become differentiated in the adult rat. We measured the endogenous content of dopamine and its intraneuronal metabolite, L-3,4-dihydroxyphenylacetic acid, and the activity of tyrosine hydroxylase as indices of dopaminergic activity. Results showed that perinatal exposure to cannabinoids caused several changes in the evolution of the dopaminergic indices studied. These changes were mainly observed in males. The only alteration in females occurred on the tenth day of development: An increase in dopamine content was observed with no changes in either the content of L-3,4-dihydroxyphenylacetic acid or tyrosine hydroxylase activity. In males, the content of both dopamine and L-3,4-dihydroxyphenylacetic acid were decreased on the day previous to birth in the animals exposed to cannabinoids. Although the reduction in its metabolite disappeared on the fifth day, the decrease in dopamine was maintained and it was correlated with a decrease in tyrosine hydroxylase activity. However, this decrease in the activity of tyrosine hydroxylase was followed by an increase on the tenth day. These results allow us to conclude that perinatal exposure to cannabinoids produces changes in the normal development of several indices of the activity of dopaminergic neurons in the brain area containing the most important population of dopaminergic endings. These changes were mainly observed in males. They could be responsible for a long-term alteration in the neurological processes in which these neurons are involved in the adult.

Nigrostriatal and mesolimbic dopaminergic activities were modified throughout the ovarian cycle of female rats

In this work, we have studied the changes in the functional state of nigrostriatal (NSDA) and mesolimbic (MLDA) dopaminergic neurons during the estrous cycle of the female rat. The activity of tyrosine hydroxylase (TH), the turnover rate (Kt) after inhibition of dopamine (DA) synthesis and the ratio between the contents of this amine and its metabolite, L-3,4 dihydroxyphenylacetic acid (DOPAC), were used as indices of neuronal activity. The neuronal activity of NSDA neurons rose during estrous and declined during proestrous, as reflected by the values of Kt and DOPAC/DA ratio measured during both phases. Interestingly, the course of variations in striatal TH activity was similar, although retarded in relation to the changes in neuronal activity. Thus, TH activity was high during diestrous, whereas it was low during estrous. The activity of MLDA neurons was reduced during proestrous. This can be concluded from the decreased Kt and DOPAC/DA ratio measured in this phase and it was accompanied by a low TH activity. Thereupon, both Kt and TH activity increased during estrous. These results indicate the existence of physiological changes in the functional state of both dopaminergic systems during the ovarian cycle, which are partially different for each neuronal pathway. This supports the existence of a specific regulation, and not indiscriminate effects, by the hormones involved in this cycle, mainly estradiol and progesterone.

Is prolactin playing a role in the regulation of catecholamine synthesis and release from male rat adrenal medulla?

Previous evidence allows one to suspect that prolactin (PRL) may be a physiological regulator of catecholamine (CA) synthesis and release in the adrenal gland of rodents. To explore this possibility, we studied the in vivo and in vitro metabolism and release of noradrenaline (NA) and adrenaline (A) in the adrenal gland of male rats. The study was carried out with animals exhibiting a moderate increase in plasma PRL levels induced by grafting of additional pituitaries or a severe hyperprolactinemia produced by diethylstilbestrol (DES)-induced pituitary hyperplasia. The latter animals exhibited a significant increase in adrenal weight, associated with decrease in tyrosine hydroxylase (TH) activity and in NA content. Moreover, the adrenal activity of phenylethanolamine-N-methyl transferease (PNMT) was decreased in DES-treated animals. Pituitary-grafted rats also displayed an increased adrenal weight, together with decreases in the activities of PNMT, catechol-O-methyl transferase and monoamine oxidase. These in vivo observations were followed by in vitro studies, which showed a decrease in the basal release of both CAs from incubated adrenals of DES-treated rats, with no changes in pituitary-grafted rats. In addition, exposure to PRL of the incubated adrenals of animals exhibiting normal PRL levels produced decreases in A release and storage and in TH activity. These observations allow us to conclude that: i) PRL appears to exert an inhibitory influence on the catecholaminergic activity in the adrenal gland; and ii) its effect seems to be exerted by a direct action on this gland.

Time-dependent effects of ovarian steroids on tyrosine hydroxylase activity in the limbic forebrain of female rats

In this work, we have studied the time-course of the effects of pharmacological administration of ovarian steroids on tyrosine hydroxylase (TH) activity in the limbic forebrain of ovariectomized rats. Administration of estradiol produced a late decrease in TH activity. This effect was found 24 hours after the last steroid injection, disappearing at 32 hours. It was antagonized by progesterone, since a single injection of this steroid to estradiol-pretreated rats reversed to control values the estradiol-induced decrease. Nevertheless, the administration of progesterone after estradiol treatment caused a short-time decrease in the limbic activity of TH, which was observed 4 hours after the last steroid injection, disappearing subsequently. On the other hand, the administration of progesterone alone produced a biphasic effect, with a reduction at 24 hours, followed by an increase at 32 hours. These effects were only observed in the animals non-treated with estradiol, disappearing with a previous treatment with estrogens. Hence, it can be concluded that both ovarian steroids may affect the limbic TH activity. Thus, estradiol produced a late inhibitory effect on the activity of this enzyme, which was antagonized by progesterone. Administration of the last one to estradiol-treated rats produced a short-time inhibitory effect, whereas its administration to non-treated rats produced a late biphasic effect (inhibition followed by stimulation), which was not observed in estradiol-treated rats.

Prolactin inhibits the activity of tyrosine hydroxylase in cultured bovine adrenal chromaffin cells in a dose-dependent manner

Prolactin can modulate the adrenal medulla function, but it has not yet been established whether its action is directly exerted on the adrenal medulla cells. In this work, we have studied the effect of several concentrations of prolactin on the synthesis, storage and release of norepinephrine and epinephrine using cultured bovine adrenal chromaffin cells. In these cells, prolactin inhibited the activity of tyrosine hydroxylase, the rate-limiting enzyme in the catecholamine synthesis, in a dose-dependent manner, from a concentration above 50 ng/ml of prolactin in the incubation medium. Surprisingly, this dose-dependent decrease was not accompanied by changes in the catecholamine release, since the secretion of both norepinephrine and epinephrine as well as the total catecholamine secretion were not significantly altered by the different prolactin concentrations. Moreover, the cellular content of both catecholamines was not altered by prolactin. In summary, these observations allow us to conclude that prolactin exerts a direct inhibitory effect on the tyrosine hydroxylase activity in cultured adrenal chromaffin cells without altering catecholamine release.

Time-course of the effects of ovarian steroids on the activity of limbic and striatal dopaminergic neurons in female rat brain

This paper studies the time-course of the effects of pharmacological administrations of ovarian steroids on the functional state of dopaminergic terminals in the striatum and the limbic forebrain, using the ratio between the contents of dopamine (DA) and its metabolite, L-3,4 dihydroxyphenylacetic acid (DOPAC), as an index of nerve activity. Estradiol produced an increase in the dopaminergic activity of both limbic and striatal neurons, reflected in the high DOPAC/DA ratio observed in both areas. This estrogenic effect was only observed at 4 hours, disappearing in the subsequent times studied. The effect was antagonized by progesterone in both tissues, since a single injection of this steroid to estrogen-pretreated rats restored to control values the estradiol-induced increase, suggesting the existence of negative interactions between both steroids. Furthermore, treatment with progesterone produced also a late decrease of the DOPAC/DA ratio in the striatum, which was observed only in the animals nonpretreated with estrogens.

Changes in brain dopaminergic indices induced by perinatal exposure to cannabinoids in rats

Perinatal exposure to cannabinoid derivatives has been shown to produce effects on brain development. In this study, we evaluated the changes induced by maternal exposure to hashish crude extract (HCE) during gestation and lactation in several biochemical indices of dopamine activity in the striatum and the limbic forebrain of offspring. Studies were performed either during the HCE exposure or after drug withdrawal. Perinatal exposure to HCE reduced the number of striatal D1 binding sites in females and increased the L-3,4-dihydroxyphenylacetic acid/dopamine (DOPAC/DA) ratio, whereas an increase in the number of striatal D2 binding sites, with a reduction in their affinity, and a decrease in the activity of tyrosine hydroxylase (TH) were observed in males. The DOPAC/DA ratio was also increased in the limbic forebrain in HCE-exposed females, but there were no changes in binding site parameters. Most of these effects disappeared after cessation of cannabinoid treatment, but the decrease in striatal TH activity in males was maintained during drug withdrawal. Interestingly, the affinity of D2 receptors in the striatum of females, the number of striatal D1 receptors in males, and the limbic TH activity in males increased after the cessation of drug treatment. These results allow us to conclude that: (1) the effects of perinatal exposure to HCE were different depending on the sex and the specific brain area studied; and (2) most of the effects disappeared after cessation of cannabinoid treatment, although some new changes then appeared.

Role of ovarian steroids on the catecholamine synthesis and release in female rat adrenal: in vivo and in vitro studies

In a previous report, we describe the existence of an effect of ovarian steroids on the adrenal medulla activities of the enzymes involved in catecholamine (CA) catabolism. To complete that study, we have now examined the adrenal medulla activity of tyrosine hydroxylase (TH), the rate limiting enzyme of the CA synthesis, as well as the in vitro release of CAs from incubated adrenal medullas. The study has been performed with adrenal medullas from female rats with physiological (estrous cycle) or pharmacological (steroid treatment) alterations in their circulating levels of estrogens and progesterone. The in vitro release of CAs from incubated adrenal medullas of estradiol-treated rats was lower than that obtained in vehicle-treated animals. In consequence, the preovulatory increase of estradiol would be the responsible of the low in vitro release of CAs observed during the estrous phase of ovarian cycle. However, this steroid does not seem to affect the CA synthesis, since the adrenal medulla activity of TH was not altered after the estradiol treatment nor during the estrous cycle. On the contrary, progesterone treatment increased TH activity 24 h after the steroid injection. This effect was independent of estradiol. However, an estrogen-dependent increase in TH activity occurred short-time after the steroid administration. Although progesterone by itself failed to modify the in vitro release of both CAs, it was able to reverse the estradiol-induced decrease in epinephrine release. In summary, estradiol seems to decrease the ability of the adrenal medulla to release CAs to the peripheral blood, without affecting the CA synthesis, whereas progesterone mostly affects TH activity, being its effects temporary and partially depending on estrogens.