Synthesis and Mesomorphic Properties of Azo Compounds Derived from Phenyl-and Thienyl-1,3,4-Thiadiazole

The synthesis and mesomorphic behaviour of new series of liquid crystals containing 1,3,4- thiadiazole and thiophene rings with azo central bond are reported (series 5a and 5b). All compounds of series 5a exhibit enantiotropic nematic mesophase and the higher homologues (n = 9 - 10) also show a monotropic smectic C phase. Series 5b show dimorphism SC - N (for n = 5 - 7 the SC is monotropic). These series are compared with the Schiff’s bases analogues, the imine bond gives rise to similar liquid crystals phase but larger mesomorphic range.

Acetylsalicylic acid (aspirin) and salicylic acid interaction with the human erythrocyte membrane bilayer induce in vitro changes in the morphology of erythrocytes

Despite the well-documented information, there are insufficient reports concerning the effects of salicylate compounds on the structure and functions of cell membranes, particularly those of human erythrocytes. With the aim to better understand the molecular mechanisms of the interaction of acetylsalicylic acid (ASA) and salicylic acid (SA) with cell membranes, human erythrocyte membranes and molecular models were utilized. These consisted of bilayers of dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE), representative of phospholipid classes located in the outer and inner monolayers of the human erythrocyte membrane, respectively. The capacity of ASA and SA to perturb the multibilayer structures of DMPC and DMPE was evaluated by X-ray diffraction while DMPC unilamellar vesicles (LUV) were studied by fluorescence spectroscopy. Moreover, we took advantage of the capability of differential scanning calorimetry (DSC) to detect the changes in the thermotropic phase behavior of lipid bilayers resulting from ASA and SA interaction with PC and PE molecules. In an attempt to further elucidate their effects on cell membranes, the present work also examined their influence on the morphology of intact human erythrocytes by means of defocusing and scanning electron microscopy, while isolated unsealed human erythrocyte membranes (IUM) were studied by fluorescence spectroscopy. Results indicated that both salicylates interact with human erythrocytes and their molecular models in a concentration-dependent manner perturbing their bilayer structures.

Biochemical evidence for the presence of small and large noradrenergic storage vesicles isolated from cat ovary in isoosmotic conditions. Distribution of dopamine-?-hydroxylase activity

The cat ovary presents unusually high levels of noradrenaline that change according to the endocrine status of the animal. Their functional meaning remains unknown. The cat ovary innervation, unlike that of other organs receiving noradrenergic innervation, has been poorly characterized on biochemical grounds. We present here a biochemical characterization of the neurotransmitter storage. By using hyperosmotic and isoosmotic gradients evidence is presented that noradrenaline is associated to two different populations of vesicles. In hyperosmomolarity conditions (sucrose gradients) "light" vesicles (density 1.12 g/ml) and "heavy" vesicles (density 1.17 g/ml) appeared. In both vesicles, noradrenaline and dopamine-?-hydroxylase were found. In isoosmotic Percoll gradients distribution of the markers also suggested the presence of two vesicle populations. Light vesicles (density 1.033 g/ml) with high dopamine-?-hydroxylase activity but very low levels of noradrenaline and adenosine triphosphate; [(3)H]noradrenaline, used as a specific exogenous vesicle marker, was feebly incorporated in this fraction. Heavy vesicles (density 1.041 g/ml) containing high levels of noradrenaline, adenosine triphosphate, low levels of dopamine-?-hydroxylase activity are able to incorporate high amounts of [(3)H]noradrenaline. In these gradients, Mg(2+) activated ATPase activity was present in both vesicle fractions. Sedimentation analysis by analytical differential centrifugation also disclosed two types of vesicles: large vesicles with a sedimentation coefficient between 348 and 308 S and small vesicles with a sedimentation coefficient of 96 S . Large vesicles were associated with noradrenaline-?-hydroxylase activity, while small vesicles were associated only with noradrenaline. In isoosmotic conditions the use of other microsomal markers allowed us to define the degree of contamination of the vesicle fractions. It was found that the noradrenergic heavy vesicles fraction presented under 11% of 5?-nucleotidase activity of the total activity present in the gradient and less than 5% of acid phosphatase, NADH-cytochrome c reductase and monoaminooxidase of the total activities in the gradients. In isoosmotic conditions the physical properties of presumed vesicles were apparently undisturbed supporting the current morphometric observations. Our results then suggest prevailing roles for each type of vesicle: synthesis for light vesicles, and storage and/or release for heavy ones.

Synthesis of E-9-Dodecen-1-yl Acetate Using Organomanganese Reagents

The Grignard reagent obtained from 2-(6-bromohexyloxy)-tetrahydropyrane, by treatment with anhydrous manganese(II) chloride was transformed to the corresponding organomanganese reagent, which was coupled with E-1-bromo-3-hexeneby treatment with anhydrous manganese chloride. Further deprotection and acetylation furnished E-9-dodecen-1-yl acetate. A second procedure involved the coupling of E-3-hexenylmanganese bromide and 6-bromohexyl acetate. Coupling reactions were carried out at 0 °C, using tetrahydrofurane and N-methylpyrrolidone as co-solvent.

Effects of mild protein prenatal malnutrition and subsequent postnatal nutritional rehabilitation on noradrenaline release and neuronal density in the rat occipital cortex

There is evidence that severe malnutrition started during gestation and continued through lactation affects adversely the morphologic development of the neocortex leading to increased neuronal cell packing density and decreased dendritic branching. Nevertheless, the effect of purely mild protein prenatal malnutrition on neocortical development remains rather unexplored. This study evaluates the effects of mild protein prenatal malnutrition (8% casein diet, calorically compensated by carbohydrates) and subsequent postnatal nutritional rehabilitation (25% casein diet) on: (i) the potassium-induced release of [(3)H]-noradrenaline (NA) in occipital cortex slices obtained from 1- and 22-day-old pups; and (ii) the packing density of neurons in lateral, dorso-lateral and dorsal regions of the occipital cortex of 22-day-old pups by using the optical dissector method. The experiments were performed in rats normally fed during gestation and lactation (G(+)L(+)), malnourished during gestation but rehabilitated during lactation (G(-)L(+)) and malnourished during gestation and lactation (G(-)L(-)). At day 1 of age, no significant differences in body and brain weights were observed between prenatally well-nourished and malnourished pups. Nevertheless, at this early age, pups born from mothers submitted to the 8% casein diet had significantly higher cortical net percent NA release than pups born from mothers receiving the 25% casein diet. At weaning (22 days of age) G(-)L(+) rats had, compared to the G(+)L(+) group, similar body weight, brain weight and [(3)H]-NA release values, but significantly higher neuron density scores in the lateral region of the occipital cortex. In contrast, at 22 days of age, G(-)L(-) rats exhibited, compared to G(+)L(+) animals, significant deficits in body and brain weights as well as significant increases in cortical net percent NA release together with enhanced packing density of neurons in the lateral, dorso-lateral and dorsal regions of the occipital cortex. Moreover, in G(-)L(-) animals was not found the laterodorsal histogenetic gradient of neuronal cell packing density observed in G(+)L(+)rats. Results suggest that mild prenatal malnutrition per se is able to induce deleterious effects on cortical neuronal density, in spite of nutritional rehabilitation during lactation, through a mechanism involving central NA hyperactivity during gestation. Prosecution of malnutrition after birth magnifies both neurochemical and morphometric disorders.

Allopregnanolone-induced modification of presynaptic basal and K+-induced [3H]-norepinephrine efflux from rat cortical slices during the estrous cycle

Superfused frontal slices of cerebral cortex were preloaded with [3H]-norepinephrine ([3H]NE). Basal [3H]NE efflux and K+-induced [3H]NE release were studied during the estrous cycle and in the presence of neurosteroids. Basal [3H]NE efflux showed estrous cycle-related variations, with lowest values found during estrus and diestrus II. Allopregnanolone (10(-9) M) potentiated basal [3H]NE efflux from the 1st minute of its application; the effect of the steroid was still present after 20 min. This effect was also dependent upon the estrous cycle, since basal [3H]NE efflux was mainly increased during estrus diestrus I, and to a lesser degree only during proestrus. During diestrus II and after ovariectomy, basal [3H]NE efflux was no longer affected by the neurosteroid. In the presence of yohimbine (10(-6) M), the effect of allopregnanolone on basal efflux was potentiated only during the first 3 min but vanished thereafter. Allopregnanolone (10(-9) M) potentiated the K+-induced [3H]NE release during estrus, but pregnenolone (10(-9) M) was ineffective, suggesting specificity of the neurosteroid. Yohimbine (10(-6) M) also potentiated K+-induced [3H]NE release. When applied simultaneously with allopregnanolone (10(-9) M), a potentiating effect on [3H]NE release was observed. The present results suggest that allopregnanolone is a neurosteroid able to modulate norepinephrine release in the cerebral cortex in an estrous cycle-dependent manner, and that the effect could involve noradrenergic alpha-2 receptors.

Prenatal malnutrition-induced functional alterations in callosal connections and in interhemispheric asymmetry in rats are prevented by reduction of noradrenaline synthesis during gestation

Prenatal malnutrition results in increased concentration and release of central noradrenaline, a neurotransmitter that is an important regulator of normal regressive events such as axonal pruning and synaptic elimination. This suggests that some of the functional disturbances in brain induced by prenatal malnutrition could be due at least in part to increased noradrenaline activity that may enhance regressive events during early stages of development. To test this hypothesis we studied whether chronic administration of alpha-methyl-p-tyrosine, an inhibitor of tyrosine hydroxylase, to rats during gestation might prevent long-term deleterious effects of prenatal malnutrition on functional properties of interhemispheric connections of the visual cortex, and on asymmetry of visual evoked responses. The experiments were conducted on normal and malnourished rats 45-50 d of age. Prenatal malnutrition was induced by restricting the food consumption of pregnant rats to 40%, from d 8 postconception to parturition. At birth, prenatally malnourished rats had significantly greater whole-brain noradrenaline concentration as well as significantly enhanced noradrenaline release in the visual cortex. At 45-50 d of age, the malnourished group had a significantly smaller cortical area, exhibiting transcallosal evoked responses; in addition, the amplitude of these responses was significantly smaller. Malnourished rats showed a significant reduction of the normal interhemispheric asymmetry of visual evoked responses. The addition of 0.3% alpha-methyl-p-tyrosine to the diet of malnourished pregnant rats during the last 2 wk of gestation prevented functional disorders induced in the offspring by prenatal malnutrition on interhemispheric connectivity of visual areas and on interhemispheric bioelectrical asymmetry, probably by reducing the elevated brain noradrenaline activity and thereby restoring the normal trophic role of this neurotransmitter.

Prenatal protein restriction alters synaptic mechanisms of callosal connections in the rat visual cortex

Mild prenatal protein malnutrition, induced by reduction of the casein content of the maternal diet from 25 to 8%, calorically compensated by the addition of excess carbohydrates, leads to so-called "hidden" malnutrition in the rat. This form of malnutrition results in normal body and brain weights of pups at birth, but in significant alterations of their central nervous system neurochemical profiles. Since severe forms of prenatal malnutrition induce morpho-functional deficits on callosal interhemispheric communication together with brain neurochemical disturbances, we evaluated, in rats born from mothers submitted to an 8% casein diet, the potassium-induced release of [3H]-noradrenaline in visual cortex slices, as well as functional properties of callosal-cortical synapses by determining cerebral cortical excitability to callosal inputs and fatigability and temporal summation of transcallosal evoked responses. Rats born from mothers submitted to a 25% casein diet served as controls. At birth prenatally malnourished pups had significantly higher cortical percent net noradrenaline release (14.79 +/- 1.11) than controls (9.14 +/- 1.26). At 45-50 days of age, rehabilitated previously malnourished rats showed, when compared to controls; (i) significantly reduced percent net noradrenaline release in the visual cortex (4.50 +/- 0.52 vs 11.31 +/- 1.14); (ii) decreased cortical excitability to callosal inputs as revealed by significantly increased chronaxie (607.2 +/- 82.8 microseconds vs 351.3 +/- 47.7 microseconds); (iii) enhanced fatigability of transcallosal evoked responses as revealed by significantly decreased stimulus frequency required to fatigate the responses (4.9 +/- 0.8 Hz vs 9.2 +/- 1.3 Hz); and (iv) decreased ability of callosal-cortical synapses to perform temporal summation, as revealed by significantly reduced percent response increment to double-shock (54.2 +/- 6.2 vs 83.0 +/- 11.0, for a 3.2-ms interstimulus time interval). These changes, resulting from mild prenatal protein restriction, are discussed in relationship to developmental processes leading to the formation of synaptic contacts between callosal axons and their appropriate cortical target during perinatal age.

Responsiveness to depolarization of hypothalamic neurons secreting somatostatin under stress and estrous cycle conditions: involvement of GABAergic and steroidal interactions

We studied the sensitivity to a depolarizing stimulus of hypothalamic fragments dissected from cycling female donor rats exposed or not to 30-min stress at 4 degrees C. The neuronal response was estimated in terms of the ability of tissue to release somatostatin when stimulated with 40 mM K+. The data showed no differences in response to K+, regardless of the ovarian cycle of the female donors, whereas tissues dissected from ovariectomized or pregnant rats responded significantly to K+. However, when donors underwent previous cold stress, significant differences were noted at all stages of the cycle, except diestrus-1, compared with control rats. We tested whether GABA and/or neuroactive steroids could be involved in this phenomenon and observed no GABA inhibition of somatostatin release in vitro, but inhibition occurred in the presence of a neuroactive steroid, THDOC. The effect of GABA in vivo on somatostatin release was estrogen dependent because bicuculline modified the total amount of somatostatin secreted in estrus but not in diestrus II. Finally, in hypothalamic primary cultures, GABA inhibition of somatostatin release was only detected when steroids were present in the media throughout culture. Our results suggest that steroid-GABA-somatostatin interactions could explain the different responses of neurons to depolarization.

Rapid and opposite effects of dexamethasone on in vivo and in vitro hypothalamic somatostatin release

We have previously reported the rapid response of hypothalamic somatostatin (SS) neurons to acute stress. Since it is well known that glucocorticoids (GC) are involved in neuroendocrinal stress regulation, we investigate in this study the effects of acute administration of dexamethasone (Dex) on both in vivo and in vitro SS release. Freely moving animals received stereotaxic implant of a push-pull cannula into the median eminence for 10 days, and then they were perfused with artificial cerebrospinal fluid for 120-150 min. An i.p. injection of Dex (200 or 300 micrograms/100 g) induced, 15-30 min later, a mean increase in SS hypothalamic output of 62.6 +/- 6.2% of basal secretion. By contrast, after 15 min incubation of hypothalamic fragments with either 10(-7) or 10(-6) M Dex, SS release decreased abruptly to 57.3 +/- 3.3% (n = 16; P < 0.001 compared with basal release) and 78.0 +/- 9.5% (n = 13; P < 0.05 compared with basal release) of basal release, respectively. Other Dex concentrations induced no variations, giving the dose-effect curve an abrupt "on-off" effect. The inhibitory effect was blocked by picrotoxin (10(-4) M) and was immediately reversed when Dex was removed from the medium. Specificity was tested by using another steroid, estradiol, and another tissue, cortex. The rapid action of GC whatever the model used and in particular the blocking in vitro effect of picrotoxin could suggest that GCs act at the level of the membrane and could operate physiologically in response to stress. In addition, the opposite in vivo and in vitro effects on SS release would indicate that GCs exert two different controls on SS neurons.

Enhancement of central noradrenaline release during development alters the packing density of neurons in the rat occipital cortex

The effect of chronic yohimbine treatment early in life on packing density of neurons was evaluated in the occipital cortex of young rats. Yohimbine administration to pups between days 5 and 16 of postnatal life (2.5 mg/kg/day i.p.) resulted at 45 days of age in significantly higher neuronal density in layers II-V of the occipital cortex, the effect being more marked in the dorsal region than in the dorsolateral and lateral ones. Results suggest a relationship between enhanced central noradrenaline activity and altered development of the neuropil in the occipital cortex.

N-methyl-D-aspartate receptor involvement in dexamethasone and stress-induced hypothalamic somatostatin release in rats

The median eminence (ME) push-pull perfusion technique was used in this work and the results clearly showed that i.p. administration of MK-801 (4 mg/kg), a specific N-methyl-D-aspartate (NMDA) receptor antagonist, totally abolished dexamethasone (Dex) (300 micrograms/ 100 g i.p. injected) and immobilization stress-induced hypothalamic somatostatin release in adult male rats. We also observed that glutamate from median eminence-hypothalamic medio basal (ME-MBH) complex, measured by high performance liquid chromatography (HPLC), exhibited a conspicuous secretory pattern, with the total amount released not modified by Dex administration. This indicates that Dex and stress-induced somatostatin (SS) secretion is not mediated by endogenous glutamate variations but likely by activation of NMDA receptors.

Variations in hypothalamic somatostatin release and content during the estrous cycle in the rat. Effects of ovariectomy and estrogen supplementation

To investigate the secretory pattern of somatostatin (SS) from the median eminence (ME) in the female rat, as well as estrogenic influence on this secretion, we measured both SS release and hypothalamic content in cycling, 10-day ovariectomized, and ovariectomized rats treated with estradiol for 3 days before. Animals were stereotaxically implanted with a push-pull cannula into the ME, and 10 days later the hypothalamic structure was perfused with artificial cerebrospinal fluid for 120-150 min at a regular flow rate of 17 mu l/min. Secretion peaks were observed in the pattern of SS release, whatever the stage of the estrous cycle. The mean amplitude of SS peaks was similar throughout the cycle: 11.7 +/- 4.0, 8.6 +/- 1.5 and 10.5 +/- 1.3 pg at proestrus, estrus and diestrus, respectively, and it was affected neither by ovariectomy (7.4 +/- 1.3 pg) nor by estrogen replacement (5.5 +/- 1.0 pg). By contrast, mean SS release levels in the proestrus phase were significantly higher than those measured in the other phases: 21.6 +/- 2.1 vs. 17.7 +/- 1.2 pg/15 min in diestrus (p < 0.05) and vs. 12.0 +/- 0.7 pg/15 min in estrus (p < 0.001). Hypothalamic SS content showed variations quite similar to those observed during its release, i.e. with the highest values corresponding to the proestrus phase (1,170.5 +/- 224.9 pg/mg of tissue) and to the diestrus (1,156.5 +/- 332.1 pg/mg of tissue) and the lowest values in the estrus (511.5 +/- 52.9 pg/mg of tissue; p < 0.05 vs. proestrus and diestrus). In addition, the lowest SS content and secretion values were found in ovariectomized animals: 95.5 +/- 5.1 pg/mg of tissue (p < 0.001 compared to the values obtained for each stage of the estrous cycle) and 10.0 +/- 0.9 pg/15 min (p < 0.001 vs. proestrus and diestrus), respectively. Patterns of SS release and SS hypothalamic content were not modified by estradiol treatment in ovariectomized animals. Our results suggest that (1) whatever the stage of the estrous cycle, SS release from the ME is not uniform and exhibits irregular peaks; (2) mean SS release levels were subjected to gonadal influence; (3) the occurrence of SS peaks seems to be estrogen-independent, and (4) variations in hypothalamic SS content were generally in good agreement with those of neurohormone release.

Neuroactive steroids modulate GABA inhibition of hypothalamic somatostatin release

The reduced steroids 3 alpha-hydroxy-5 alpha-pregnan-20-one (allopregnanolone) and 3 alpha,21-di-hydroxy-5 alpha-pregnan-20-one (allotetrahydroDOC) are potent ligands of GABAA receptors. This study examined the possible modulatory effect of these metabolites on GABA inhibition of somatostatin release in cultured hypothalamic neurones. Allopregnanolone potentiates GABA inhibition, and reversed picrotoxin and bicuculline-induced augmentation of somatostatin release in a dose-dependent manner. AllotetrahydroDOC also inhibits the stimulated release induced by the antagonists, but did not modify that induced by depolarizing concentrations of K+. Pregnenolone sulphate had no effect on picrotoxin-induced somatostatin release. These findings clearly establish that 3 alpha-hydroxysteroids modulate GABA inhibition of hypothalamic somatostatin release.

Immune depression induced by protein calorie malnutrition can be suppressed by lesioning central noradrenaline systems

Depressed immune function is well documented in protein calorie malnutrition (PCM). Also, central noradrenergic hyperactivity has recently been reported in malnourished animals. Increase in central noradrenaline activity could be responsible for cell-mediated immune depression. The present study is designed to address this hypothesis by testing whether neurotoxic lesion of central noradrenergic systems by 6-hydroxydopamine (6-OHDA) could improve lymphoproliferative response to mitogens and interleukin (IL)-1 production in PCM rats. A significant enhancement of lymphoproliferative response to concanavalin A (ConA) and in IL-1 production was observed in spleen mononuclear cells of PCM rats injected intracerebroventricularly with 120 micrograms of 6-OHDA, as compared with solvent injected and untreated PCM animals. A significant decrease in brain noradrenaline levels was produced in the drug-injected animals. These results suggest that central noradrenergic hyperactivity is one of the mechanisms involved in the immunodepression produced by malnutrition.

Depressed immune response in malnourished rats correlates with increased thymic noradrenaline level

Depressed immune response is well documented in protein-calorie malnutrition (PCM). Also, central and peripheral noradrenaline (NA) activities have been reported to be increased in malnourished animals. Since increases in central and peripheral NA may inhibit immune function, it is possible that malnutrition-induced immunodepression could be mediated by noradrenergic hyperactivity. To address this hypothesis the effect of malnutrition on cell-mediated immune response, as well as on NA levels of the median eminence, spleen and thymus was studied in PCM rats. Decreased lymphoproliferative response and IL-1 production by mononuclear macrophages was observed in PCM. Besides, increased NA concentration was detected in thymuses of PCM rats, while unchanged levels of this neurotransmitter were observed in median eminence and spleen. These data suggest a positive correlation between malnutrition-induced immunodepression and sympathetic noradrenergic activity in thymus, an organ implicated in immune cell differentiation during early development.

Clonidine treatment during gestation prevents functional deficits induced by prenatal malnutrition in the rat visual cortex

It has been shown that prenatal malnutrition results at birth in increased concentration of noradrenaline (NA) in the brain. Besides, it is known that NA is an important regulator of normal regressive processes occurring during synaptogenesis such as cell death, axonal pruning and synaptic elimination. The present study was designed to investigate (i) whether prenatal malnutrition enhances the NA release in the visual cortex and (ii) whether or not chronic administration of clonidine during gestation may prevent long-term deleterious effects of fetal malnutrition on functional properties of interhemispheric connections of the visual cortex and on the interhemispheric asymmetry of visual evoked responses. Prenatal malnutrition was induced by restricting food consumption to pregnant rats from Day 8 postconception to parturition. Results show that at birth, prenatally malnourished rats had higher NA release than normals. At 45-50 days of age, the malnourished group exhibited (a) reduced peak-to-peak amplitude and diminished extent of the projecting field of transcallosal evoked responses, and (b) abolished interhemispheric asymmetry of visual evoked responses. Clonidine administration to malnourished mothers from Day 14 postconception to parturition (10 g/kg/day s.c.), prevented in the offspring disorders induced by prenatal malnutrition on cortical NA release, on interhemispheric connectivity of visual areas and on interhemispheric bioelectrical asymmetry, probably by restoring the normal trophic role of NA during synaptogenesis. Results are discussed in relationship to normal regressive events occurring during early brain development.

In vitro progesterone effects on 3H-norepinephrine release from rat cerebral cortex slices

The effect of progesterone in vitro (0.05-5 microM) on K(+)-induced, Ca(2+)-dependent release of 3H-NE from brain slices obtained from the occipital region of rats, during the oestrous cycle or 7 days after ovariectomy or on the fifth day of pregnancy was studied. The hormone reduced the K+ (20 mM) effect in all the stages of the cycle, but did not modify the reduced release found after ovariectomy or pregnancy or the release induced from male slices. Yohimbine blocked the effect of progesterone. The results suggest the releasing process of norepinephrine in the cerebral cortex as a target for progesterone modulatory influences on brain function.

Functional alterations induced by prenatal malnutrition in callosal connections and interhemispheric asymmetry as revealed by transcallosal and visual evoked responses in the rat

It is known that nutritional restriction during gestation affects the growth of the corpus callosum. The present study was designed to evaluate whether prenatal malnutrition may alter, in the rat, the normal pattern of functional callosal interhemispheric connections of the visual cortex. Since callosal development has been associated with brain lateralization, the effect of malnutrition during gestation on the normal asymmetry of visual cortical evoked responses was also studied. Prenatal malnutrition was induced by restricting food consumption by pregnant rats (10 g daily) from Day 8 post-conception to parturition. Results of experiments performed on 45- to 50-day-old offspring showed that the starvation treatment (i) reduced both the peak-to-peak amplitude and the extent of the projecting field of transcallosal evoked responses, and (ii) abolished the normal brain interhemispheric asymmetry of visual evoked responses. These effects are discussed in relationship to regressive events occurring during synaptogenesis, which are known to play key roles in establishing the adult structure and functional properties of the corpus callosum.

Non-neuronal endogenous GABA efflux from the rat oviduct

The subcellular distribution of Gamma-aminobutyric acid (GABA) was studied in the rat oviduct. The highest content of GABA was found in the soluble fraction. The effect of chemical stimulation of the endogenous GABA efflux from the rat oviduct was examined. High K+ concentrations could not induce elevation of the GABA efflux. Instead, a continuous spontaneous GABA efflux without change for long periods of time was observed. The total GABA content and GABA concentration were determined in the rat oviduct on days 1, 5, 10, 15, 30, 35 and 40 of the postnatal period and also during the estrous cycle. During postnatal development the GABA levels increase gradually with time reaching at prepuberal age a concentration similar to that found in diestrous rats. In the estrous cycle both GABA content and GABA concentration reached the highest value in the proestrous and the lowest value in the estrous phase. These findings support the hypothesis that GABA efflux may be modulated by the changes in oviductal fluid volume during the estrous cycle.

In vitro progesterone effects on 3H-dopamine release from rat corpus striatum slices obtained under different endocrine conditions

The release of dopamine (DA) from corpus striatum is affected by the endocrine state of the animal being progesterone suggested as a potential hormonal modulatory signal. Most of its actions have been described on endogenous DA release induced by amphetamine. However, the release of DA and the mechanism of the drug effect have been shown to be highly complexes. Considering that DA recently incorporated and/or synthetized is preferentially used we have characterized the effect of progesterone in vitro on the K(+)-induced release of 3H-dopamine (3H-DA) from rat corpus striatum slices. These were obtained during the estrous cycle or under conditions of high or low levels of endogenous progesterone (pregnant and ovariectomized rats). The release of 3H-DA was independent of the cycle. However, progesterone in vitro modified the induced release in a cycle-dependent way. Low concentrations of the hormone (100-200 mM) reduced the K+ (30 mM) effect while higher doses (300-500 mM) were facilitatories. After 7 days of ovariectomy, the induced release of 3H-DA was unchanged while in pregnant rats it was found decreased. In both cases the inhibitory effect of the hormone disappeared. Both progesterone (200 nM) and omission of Ca++ from the superfusion medium did not modified tyramine (20 microM) or K+ induced release, respectively. Data suggest that the pool of DA, related to exocytotic mechanism of release, could be specifically affected by progesterone, in a bimodal way, probably through independent genomic and non-genomic influences.

Changes of norepinephrine levels and release in rat cerebral cortex during the estrous cycle

We studied the influence of the estrous cycle and ovariectomy on the noradrenergic innervation of the rat cerebral cortex. The lowest norepinephrine (NE) concentration was found during estrus in frontal and occipital cortex. At that stage and at diestrus-2, 20 mM K+ induced the lowest release of [3H]NE from occipital region slices, and the highest release was found at 60 mM K+. Ovariectomy (7 days) decreased the 20 mM K+ effect. Yohimbine (10 x 10(-6) M) increased the induced NE release through the cycle but its effects disappeared after ovariectomy. In the frontal cortex the drug effect was only found at diestrus-1 and no changes were observed in the K+ effect through the cycle. Results suggest that normal endocrine influences can modify noradrenergic neurotransmission in the rat cerebral cortex.

Release of norepinephrine from the cat ovary: changes after ovulation

The distribution of intraneuronal constituents involved in norepinephrine (NE) storage, uptake, and release were used to estimate changes in NE secretion from the cat ovary after ovulation induced with eCG plus hCG. The content of NE and ATP, which are principally stored in small noradrenergic vesicles (isolated at a density of 1.041 g/ml in Percoll gradient), decreased after ovulation. However, the activity of dopamine beta-hydroxylase, which is principally associated with large noradrenergic vesicles (isolated at a density of 1.033 g/ml in Percoll gradient), was only slightly decreased. Mg(2+)-dependent ATPase, located in both large and small storage vesicles, decreased only in the small storage vesicles, suggesting that preferential secretion from small noradrenergic vesicles occurred. The hormonal treatment also affected the functional capacity of the vesicles, as evidenced by the decrease in uptake and storage capacity as well as the decrease in the stimulated release of 3H-NE observed after ovulation. The aforementioned changes are characteristically seen after a sympathetic discharge; thus they strongly support the notion that ovarian sympathetic activity increases during the ovulatory process, resulting in the postovulatory decrease in both the size and functional capacity of the intraneuronal compartment where NE is stored.

Yohimbine early in life alters functional properties of interhemispheric connections of rat visual cortex

It has been shown that noradrenaline (NA) is an important regulator of normal regressive processes occurring during synaptogenesis such as cell death, axonal pruning and synaptic elimination. The present study was designed to investigate whether enhanced NA release induced by chronic yohimbine administration early in life may alter in the rat the normal pattern of functional interhemispheric connections of the visual cortex. Yohimbine administration to rats between days 5 and 16 of postnatal life (2.5 mg/kg, IP, daily) resulted in changes in the pattern of transcallosal responses evoked in the visual cortex, characterized by a reduction in the peak-to-peak amplitude as well as a reduction of the extent of projecting fields of maximal activity, when examined at 30-35 days following termination of the drug treatment regimen. The results indicate that yohimbine treatment early in life induces functional alterations in the interhemispheric connectivity of the visual areas, probably by disrupting the normal trophic role of NA during synaptogenesis.

Bradykinin modulates the release of noradrenaline from vas deferens nerve terminals

To asses whether bradykinin influences the release of noradrenaline from the adrenergic varicosities of the vas deferens, tissues were loaded with 3H-noradrenaline. Upon electrical depolarization bradykinin increased in a concentration-dependent fashion, the overflow of tritium from the mouse or rat vas deferens. The 3H-overflow is dependent on the external Ca2+concentration suggesting neuronal release of 3H-noradrenaline. The present results add evidence to the hypothesis that bradykinin modulates the release of noradrenaline from peripheral sympathetic nerve terminals via the activation of a presynaptic mechanism.

Effect of clonidine early in life on brain morphofunctional deficits induced by neonatal malnutrition in the rat

A great body of evidence indicates that malnutrition early in life induces central noradrenergic hyperactivity (CNH). On the other hand, it is known that noradrenaline (NA) is an important regulator of the regressive processes occurring during synaptogenesis such as cell death, axonal pruning and synaptic elimination. This leads to the hypothesis that some of the morphofunctional modifications induced by malnutrition on the brain could be due, at least in part, to an increase of NA activity during the period of accelerated brain growth. This study evaluates whether early reduction of CNH by the alpha-2 presynaptic adrenoreceptor agonist clonidine, prevents long-term morphofunctional deficits induced by protein-energy malnutrition in the rat. Results of experiments performed on 45 day-old malnourished animals that received clonidine during the suckling period, show that the pharmacological treatment prevented: (i) deficits in both NA levels and NA release in the visual cortex; (ii) deficit in brain weight but not in body weight; and (iii) reduction of the normal brain interhemispheric asymmetry of visual cortical evoked potentials. It is suggested that administration of clonidine early in life prevents brain morphofunctional deficits by malnutrition, by restoring the normal tropic role of NA during synaptogenesis.

Changes of norepinephrine levels, tyrosine hydroxylase and dopamine-beta-hydroxylase activities after castration and testosterone treatment in vas deferens of adult rats

Norepinephrine levels and tyrosine hydroxylase and dopamine-beta-hydroxylase activities have been used to evaluate the effect of castration and testosterone treatment on the sympathetic innervation of the adult vas deferens. Castration was followed by a decrease in both norepinephrine content and tyrosine hydroxylase activity, even though the changes were not concomitant. Treatment of castrated animals with testosterone reversed the effect of castration on organ weight and norepinephrine content, but only a short-lasting increase in tyrosine hydroxylase activity occurred at the beginning of testosterone treatment. In contrast, the testosterone-induced recovery of norepinephrine content observed at this time was accompanied by a marked increase in dopamine-beta-hydroxylase activity. The results suggest that in rat vas deferens, norepinephrine levels are under androgenic control and that this regulation mainly involves changes in dopamine-beta-hydroxylase activity rather than a modulation of tyrosine hydroxylase.

Early malnutrition and changes in the induced release of noradrenaline in the prefrontal cortex of adult rats

The influence of early protein-energy malnutrition on the induced release of noradrenaline in the rat prefrontal cortex was studied: (i) by evaluating in vivo the release of the neurotransmitter as revealed by changes in the ability of pyramidal cells to integrate transient transmembrane currents generated by discrete packets of noradrenaline released by repetitive electrical stimulation of the locus coeruleus; and (ii) by measuring in vitro the potassium-induced release of 3H-noradrenaline in slices obtained from the brain frontal pole. Both electrophysiological and neurochemical data show that, in malnourished rats, weak stimulation produces an increased release, whereas strong stimulation results in a decreased release of the neurotransmitter. The results provide direct evidence that malnutrition alters the release of noradrenaline at the cortical level. Since the prefrontal cortex is involved in cognitive processing, the present results could provide functional evidence linking nutritional and behavioral deficits.

Changes in noradrenergic vesicle markers of rabbit oviducts during progesterone treatment

The effect of progesterone (P) on norepinephrine (NE), [3H] norepinephrine ([3H]NE) and dopamine beta-hydroxylase (DBH) in noradrenergic vesicles from rabbit oviducts was studied after daily injections of the hormone during different periods (4, 7 and 15 days). Progesterone induced a concomitant increase in NE and DBH activity and [3H]NE uptake. To study the mechanism involved in such effects, 4 tissue fractions were obtained by differential centrifugation of the oviducts of which the vesicular fraction was applied over continuous sucrose gradients (0.3-2 M). The changes induced by P in markers of tissue and gradient fractions showed an increase of the NE storage capacity which could be ascribed to an increase in the number of storage vesicles, and/or to a higher extravesicular storage capacity. The occurrence of these mechanisms during pregnancy or after P treatment could account for the (long-lasting) high levels of NE observed in such instances.