Daily variation of zooplankton abundance and evenness in the Rosana reservoir, Brazil: biotic and abiotic inferences

The zooplankton community presents stochastic temporal fluctuation and heterogeneous spatial variation determined by the relationships among the organisms and environmental conditions. We predicted that the temporal and spatial zooplankton distribution is heterogeneous and discrete, respectively, and that the daily variation of most abundant species is related to environmental conditions, specifically the availability of resources. Zooplankton samples were collected daily at three sampling stations in a lateral arm of the Rosana Reservoir (SP/PR). The zooplankton did not present significant differences in abundance and evenness among sampling stations, but the temporal variation of these attributes was significant. Abiotic variables and algal resource availability have significantly explained the daily variation of the most abundant species (p<0.001), however, the species distribution makes inferences on biotic relationships between them. Thus, not only the food resource availability is influential on the abundance of principal zooplankton species, but rather a set of factors (abiotic variables and biotic relationships).

DAILY VARIATION OF CONSTITUTIVELY ACTIVATED NUCLEAR FACTOR KAPPA B (NFKB) IN RAT PINEAL GLAND

In mammals, the production of melatonin by the pineal gland is mainly controlled by the suprachiasmatic nuclei (SCN), the master clock of the circadian system. We have previously shown that agents involved in inflammatory responses, such as cytokines and corticosterone, modulate pineal melatonin synthesis. The nuclear transcription factor NFKB, detected by our group in the rat pineal gland, modulates this effect. Here, we evaluated a putative constitutive role for the pineal gland NFKB pathway. Male rats were kept under 12 h: 12 h light-dark (LD) cycle or under constant darkness (DD) condition. Nuclear NFKB was quantified by electrophoretic mobility shift assay on pineal glands obtained from animals killed throughout the day at different times. Nuclear content of NFKB presented a daily rhythm only in LD-entrained animals. During the light phase, the amount of NFKB increased continuously, and a sharp drop occurred when lights were turned off. Animals maintained in a constant light environment until ZT 18 showed diurnal levels of nuclear NFKB at ZT15 and ZT18. Propranolol (20 mg/kg, i.p., ZT 11) treatment, which inhibits nocturnal sympathetic input, impaired nocturnal decrease of NFKB only at ZT18. A similar effect was observed in free-running animals, which secreted less nocturnal melatonin. Because melatonin reduces constitutive NFKB activation in cultured pineal glands, we propose that this indolamine regulates this transcription factor pathway in the rat pineal gland, but not at the LD transition. The controversial results regarding the inhibition of pineal function by constant light or blocking sympathetic neurotransmission are discussed according to the hypothesis that the prompt effect of lights-off is not mediated by noradrenaline, which otherwise contributes to maintaining low levels of nuclear NFKB at night. In summary, we report here a novel transcription factor in the pineal gland, which exhibits a constitutive rhythm dependent on environmental photic information. (Author correspondence: rpmarkus@usp.br)

Longitudinal study of daily variation of rats' behavior in the elevated plus-maze

We conducted a longitudinal study about daily variation of Wistar male rats' behavior in the elevated plus-maze (EPM) evaluated in the 1st, 2nd, 3rd, 6th, 12th, and 18th months of life. Animals were submitted to the plus-maze in 12 sessions at 2-h intervals (n=72, 6 per time point). Spontaneous rest-activity rhythm of four animals was assessed by observation of 24-h videotape records. Time series were analyzed by Cosinor method. Behavioral rates on the six occasions and in light and dark phases were compared by means of two-way ANOVA with repeated measures. Exploratory behavior in EPM was smaller in the light phase and in older animals. Higher values of open and closed arms exploration were observed in the first and third months of the dark phase, and in the first month of the light phase. Adjustment to the 24-h period was significant at all stages for rest-activity data, number of entries in closed arms, and time on center, and for three to five stages for open-arm exploration. In general, 24 h variability was more pronounced in younger animals compared with older ones. The present study showed that: (1) a significant amount of total variability of the behavioral indexes analyzed could be attributed to 24 h variation, (2) light/dark phases differences in EPM exploration were present at all developmental stages, (3) older Wistar rats explored less the EPM and were less active in their home cage compared with younger ones, and (4) behavioral indexes (EPM) decrease was phase related and partially related to a reorganization of rest-activity rhythm. (C) 2003 Elsevier B.V. All rights reserved.

DAILY VARIATION IN PLASMA-CONCENTRATION OF FENCAMFAMINE AND STRIATAL DOPAMINE-RECEPTORS IN RATS

Fencamfamine (FCF) is a psychostimulant drug classified as an indirect dopamine agonist. In the present study we evaluated the daily variation in plasma FCF concentration and in striatal dopamine receptors. Adult male Wistar rats (250-300 g) maintained on a 12-h light/12-h dark cycle (lights on at 07:00 h) were used. Rats received FCF (10.0 mg/kg, ip) at 09:00, 15:00, 21:00 or 03:00 h and blood samples were collected 30 (N = 6) or 60 (N = 6) min after the injections. Plasma FCF was measured by gas chromatography using an electron capture detector. Two-way ANOVA showed significant differences in FCF concentration when blood samples were collected 30 min after the injection, and the highest value was obtained following injection 21:00 h. Moreover, at 15:00, 21:00 and 03:00h, plasma FCF levels were significantly lower 60 min after injection when compared to the 30-min interval. Two other groups of rats (N = 6) were decapitated at 09:00 or 21:00 h and the striata were dissected for the binding assays. The Bmax for [H-3]-spiroperidol binding to striatal membranes was higher at 21:00 h, without changes in affinity constant (Kd). In conclusion, plasma FCF levels and dopamine receptors undergo daily variation,a phenomenon that should be considered to explain the circadian time-dependent effects of FCF.

Temporal variation in glucocorticoid levels during the resting phase is associated in opposite way with maternal and paternal melanic coloration.

Sex-dependent selection can help maintain sexual dimorphism. When the magnitude of selection exerted on a heritable sex trait differs between the sexes, it may prevent each sex to reach its phenotypic optimum. As a consequence, the benefit of expressing a sex trait to a given value may differ between males and females favouring sex-specific adaptations associated with different values of a sex trait. The level of metabolites regulated by genes that are under sex-dependent selection may therefore covary with the degree of ornamentation differently in the two sexes. We investigated this prediction in the barn owl, a species in which females display on average larger black spots on the plumage than males, a heritable ornament. This melanin-based colour trait is strongly selected in females and weakly counter-selected in males indicating sex-dependent selection. In nestling barn owls, we found that daily variation in baseline corticosterone levels, a key hormone that mediates life history trade-offs, covaries with spot diameter displayed by their biological parents. When their mother displayed larger spots, nestlings had lower corticosterone levels in the morning and higher levels in the evening, whereas the opposite pattern was found with the size of paternal spots. Our study suggests a link between daily regulation of glucocorticoids and sex-dependent selection exerted on sexually dimorphic melanin-based ornaments.

Daily dynamics of photosynthesis of the freshwater red alga Sirodotia delicatula (Batrachospermales, Rhodophyta)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Daily cycling of nitric oxide synthase (NOS) in the hippocampus of pigeons (C. livia)

Abstract: Background: Nitric oxide synthase (NOS) is essential for the synthesis of nitric oxide (NO), a non-conventional neurotransmitter with an important role in synaptic plasticity underlying processes of hippocampus-dependent memory and in the regulation of biological clocks and circadian rhythms. Many studies have shown that both the NOS cytosolic protein content and its enzymatic activity present a circadian variation in different regions of the rodent brain, including the hippocampus. The present study investigated the daily variation of NOS enzymatic activity and the cytosolic content of nNOS in the hippocampus of pigeons. Results: Adult pigeons kept under a skeleton photoperiod were assigned to six different groups. Homogenates of the hippocampus obtained at six different times-of-day were used for NOS analyses. Both iNOS activity and nNOS cytosolic protein concentrations were highest during the subjective light phase and lowest in the subjective dark phase of the circadian period. ANOVA showed significant time differences for iNOS enzymatic activity (p < 0.05) and for nNOS protein content (p < 0.05) in the hippocampus. A significant daily rhythm for both iNOS and nNOS was confirmed by analysis with the Cosinor method (p < 0.05). The present findings indicate that the enzymatic activity of iNOS and content of nNOS protein in the hippocampus of pigeons exhibit a daily rhythm, with acrophase values occurring during the behavioral activity phase. Conclusions: The data corroborate the reports on circadian variation of NOS in the mammalian hippocampus and can be considered indicative of a dynamic interaction between hippocampus-dependent processes and circadian clock mechanisms.

Daily cycling of nitric oxide synthase (NOS) in the hippocampus of pigeons (C. livia)

Background: Nitric oxide synthase (NOS) is essential for the synthesis of nitric oxide (NO), a non-conventional neurotransmitter with an important role in synaptic plasticity underlying processes of hippocampus-dependent memory and in the regulation of biological clocks and circadian rhythms. Many studies have shown that both the NOS cytosolic protein content and its enzymatic activity present a circadian variation in different regions of the rodent brain, including the hippocampus. The present study investigated the daily variation of NOS enzymatic activity and the cytosolic content of nNOS in the hippocampus of pigeons. Results: Adult pigeons kept under a skeleton photoperiod were assigned to six different groups. Homogenates of the hippocampus obtained at six different times-of-day were used for NOS analyses. Both iNOS activity and nNOS cytosolic protein concentrations were highest during the subjective light phase and lowest in the subjective dark phase of the circadian period. ANOVA showed significant time differences for iNOS enzymatic activity (p < 0.05) and for nNOS protein content (p < 0.05) in the hippocampus. A significant daily rhythm for both iNOS and nNOS was confirmed by analysis with the Cosinor method (p < 0.05). The present findings indicate that the enzymatic activity of iNOS and content of nNOS protein in the hippocampus of pigeons exhibit a daily rhythm, with acrophase values occurring during the behavioral activity phase. Conclusions: The data corroborate the reports on circadian variation of NOS in the mammalian hippocampus and can be considered indicative of a dynamic interaction between hippocampus-dependent processes and circadian clock mechanisms.

Air pollution and hospital admissions for respiratory diseases in the subequatorial Amazon: a time series approach

The objective of the study is to evaluate the effect of the daily variation in concentrations of fine particulate matter (diameter less than 2.5µm - PM2.5) resulting from the burning of biomass on the daily number of hospitalizations of children and elderly people for respiratory diseases, in Alta Floresta and Tangará da Serra in the Brazilian Amazon in 2005. This is an ecological time series study that uses data on daily number of hospitalizations of children and the elderly for respiratory diseases, and estimated concentration of PM2.5. In Alta Floresta, the percentage increases in the relative risk (%RR) of hospitalization for respiratory diseases in children were significant for the whole year and for the dry season with 3-4 day lags. In the dry season these measurements reach 6% (95%CI: 1.4-10.8). The associations were sig-nificant for moving averages of 3-5 days. The %RR for the elderly was significant for the current day of the drought, with a 6.8% increase (95%CI: 0.5-13.5) for each additional 10µg/m3 of PM2.5. No as-sociations were verified for Tangara da Serra. The PM2.5 from the burning of biomass increased hospitalizations for respiratory diseases in children and the elderly.

Study of a population of Biomphalaria tenagophila (Orbigny, 1835) and of schistosomiasis transmission in "Alto da Boa Vista", Rio de Janeiro

The present study was performed using data from a Biomphalaria tenagophila population located in a water cress garden in the Alto da Boa Vista region representing an isolated focal point of schistosomiasis in the city of Rio de Janeiro. The density and age structure of this B. tenagophila population and its rate of intection by Schistosoma mansoni were studied for a period of 15 months. The snail population showed seasonal variation in density, with a decrease in number of individual at the begining of the rainy season. At the end of this season, the population consisted mainly of adults (92.8% in May 1985 and 82.8% in April 1986). The population growth curve was logistic and of sigmoidal configuration. Shiscotoma mansoni cercariae were eliminated over a short period of time (March, April and May 1986). The release of cercariae of S. mansoni and of birds seems to depend on environmental temperature, which during certain months would show a daily variation of up to 13ºC, with the lower thermal limit approaching the limit value for sporocyte development.

Please die during office hours : periodicity of cardiovascular events in switzerland between 1969 and 2007

Purpose: to evaluate and compare the periodical patterns of death from cardiovascular disease (CVD), including acute myocardial infarction (AMI) and stroke in the Swiss population between the years 1969 and 2007.¦Methods: Swiss mortality database for the period of 1969- 2007 (2'362'430 deaths overall). The number of deaths due to CVD, AMI and stroke according to the time of day, day of the week and month were assessed, overall and after dividing the events according to gender and age (< 65 or ≥65 years old).¦Results: In general and for all four subgroups according to age and sex, there is a daily variation in the number of deaths with a first peak in the morning (8h00 -12h00) and a smaller second peak in the late afternoon (14h - 18h). Both males and females have similar hourly patterns, although the magnitude of the difference diminishes in older patients particularly for people who die from stroke. For the weekly variation, there seems to be a significant trend only in the younger population with the lowest mortality rates on Sunday and the highest on Mondays for all diseases. When it comes to seasonal variation according to month, the trend is more significant in the elder patients with the highest death rates during the winter months (+31%) and the lowest in the summer (July/August).¦Conclusion: There is a timely pattern for CVD, AMI and stroke deaths in Switzerland. This pattern changes according to the age and sex of the patients. Knowing this trend, its triggering factors and consequences, perhaps there could be measures put in place to prevent, diagnose and treat the population which is the most vulnerable at certain times.

Molluscicidal action of the latex of Euphorbia splendens var. hislopii N.E.B. ("Christ's Crown") (Euphorbiaceae) against Lymnaea columella (Say, 1817) (Pulmonata: Lymnaeidae), intermediate host of Fasciola hepatica Linnaeus, 1758 (Trematode: Fasciolidae): 1- test in laboratory

The latex action of Euphorbia splendens var. hislopii (Christ's Crown) against snails Lymnaea columella, intermediate host of Fasciola hepatica, derived from irrigation ditches of the Station of Pisciculture at Universidade Federal Rural do Rio de Janeiro, was studied in the laboratory. Lab bioassays, using aqueous solutions of the latex, varying between 0.1 and 10 mg/l, have proven molluscicidal activity of the product collected on the same day the tests were performed, during the four seasons of the year, finding the following lethal concentrations (LC90): 1.51 mg/l in the spring; 0.55 mg/l in the summer; 0.74 mg/l in the fall and 0.93 mg/l in winter, after 24 h exposure of the snails, showing significant differences among the seasons of the year (ANOVA test, F = 11.01, G.L.= 3/33, p < 0.05), as well as among the concentrations (ANOVA test, F = 27.38, G.L.= 11/33, p < 0.05). In the summer, mortality reached 100% from concentration at 0.6 mg/l, the same during fall and in winter as of 1 mg/l, while in spring it only reached 100% mortality as of 2 mg/l. Mortality in the controls was low, reaching 5% in the summer and winter and 10% in the fall and spring. None of the samples died. During the assay, with an aqueous solution of the latex at a concentration of 5 mg/l, in order to check the time of duration of the product effect, in the laboratory, it was observed that the molluscicidal activity remained stable up to the 15th day after the beginning of the test with 100% mortality of L. columella, gradually losing its effect until the 23rd day, when we no longer observed animal mortality. In the control group, there was a random daily variation in mortality rate ranging 0-50% after 48 h of observation for 30 days.

Role of CLOCK and circadian rhythms in calcium homeostasis

Le maintien d'une concentration sanguine constante de calcium est d'une importance cruciale et trois organes participent à la balance calcique normale : les reins, les intestins et les os. La concentration plasmatique de calcium est strictement régulée par l'hormone parathyroïdienne (PTH) et par la vitamine D. Des variations circadiennes de la PTH, de la vitamine D ainsi que du calcium plasmatique ont été décrites précédemment chez l'humain ainsi que chez le rat. Ces rythmes de PTH dans le sérum sont importants pour la régulation du remodelage de l'os. En effet, il a été montré chez les souris C57BL/6J que des injections de PTH une fois par jour mènent à une augmentation de la densité minérale de l'os alors que l'infusion en continu de PTH est associée à une diminution de cette densité. La vitamine D joue également un rôle fondamental dans la physiologie osseuse, car un déficit en vitamine D peut conduire à une ostéomalacie. Cependant la fonction des oscillations de vitamine D au niveau de l'homéostasie osseuse reste inconnue. L'horloge circadienne est un système interne de contrôle biologique du temps générant des rythmes de 24 heures dans l'expression des gènes, ainsi que dans la physiologie et le comportement. Ce contrôle s'opère par des boucles rétroactives positives et négatives de l'expression de gènes circadiens tels que CLOCK, BMAL1, CRY1 et 2 ou PERI et 2. Dans ce travail, nous avons émis l'hypothèse que l'homéostasie calcique est sous le contrôle de l'horloge circadienne. Dans un premier temps, nous avons montré chez les souris C57BL/6J des variations journalières des concentrations de calcium, de PTH et de vitamine D dans le sang, ainsi que de calcium dans les urines. Nous avons également démontré des changements au niveau de l'expression rénale des gènes importants dans l'homéostasie du calcium, tant au niveau de l'ARN messager que des protéines. Ensuite, pour analyser le rôle du système de l'horloge circadienne dans l'homéostasie du calcium, nous avons étudié des souris dans lesquelles a été supprimé le gène CLOCK crucial pour la fonction de l'horloge et nous avons comparé ces souris à des souris de type sauvage de même portée. Les souris CLOCK-I- étaient hypercalciuriques à chaque moment de la journée. Cependant le rythme circadien de l'excrétion de calcium était préservé. Le taux de calcium plasmatique ne différait pas entre les génotypes, mais les souris CLOCK -/- ne montraient pas de variations journalières de ce paramètre. Une perte du rythme journalier était également observée pour les niveaux de vitamine D, perte qui pourrait être une cause de l'altération de la micro-architecture osseuse révélée chez les souris CLOCK-/-. En effet, ces souris montrent une diminution du nombre de trabécules, de leur volume ainsi que de leur surface, ce qui suggère la présence d'ostéoporose. Nous avons également trouvé que le rythme de l'expression de l'ARN messager de CYP27B1 était aboli dans les reins des souris CLOCK -/-, ce qui peut expliquer l'altération du rythme de la vitamine D. Les taux sanguins de PTH étaient comparables entre les souris CLOCK -/- et de type sauvage. Dans les reins, une augmentation de l'expression de l'ARN messager de TRPV5 et NCX1 a été constatée, ce qui suggérerait une augmentation de la réabsorption de calcium dans le tubule convoluté distal et dans le tubule connecteur. Dans les intestins, la réabsorption calcique était diminuée, chez les souris CLOCK-I-, fait confirmé par une diminution des niveaux d'ARN messager de TRPV6 et PMCAL. En résumé, la suppression du gène CLOCK chez les souris a conduit à une hypercalciurie, une altération du rythme des taux plasmatiques de calcium et de vitamine D et à une détérioration de l'architecture osseuse. Pour conclure, ces résultats montrent que l'horloge circadienne est essentielle à l'homéostasie calcique ainsi qu'à la physiologie des os. - L'ostéoporose affecte environ 22 millions de femmes et 5.5 millions d'hommes en Europe, réduisant significativement leur qualité de vie et a causé 3.5 millions de nouvelles fractures en 2010. Les dépenses totales liées à ces fractures ont atteint 37 milliards d'euro et ce coût devrait augmenter de 25% d'ici à 2025. Le nombre de nouvelles fractures dues à l'ostéoporose à travers le monde est estimé à environ 1000 par heure. Parmi les causes de l'ostéoporose, le déficit én calcium et/ou en vitamine D joue un rôle important, mais il existe également des causes génétiques ou liées à des facteurs comme les hormones sexuelles (estrogènes, testostérone), l'âge, le tabac, le poids corporel, certains médicaments,... La vie est rythmique : ceci est dû à l'alternance naturelle du jour et de la nuit et de ses effets sur le corps. La prise alimentaire, par exemple, est un processus qui a lieu pendant la phase active, qui est prévisible (il se produit toujours au même moment) et qui peut être anticipé par le corps. Pour cela, une horloge interne est présente dans chaque cellule du corps et est synchronisée par la lumière du jour, entre autres stimuli. Cette horloge indique la phase du jour et régule l'expression de gènes impliqués dans les différents processus qui nécessitent une anticipation. Pendant mon travail de thèse, je me suis demandé si des îythmes circadiens (c'est-à-dire d'une durée d'environ 24 heures et indépendants des stimuli externes) étaient observables'pour les gènes régulant les flux de calcium dans le corps et si l'interruption de ces rythmes pouvait mener à des altérations de la qualité de l'os. J'ai d'abord travaillé avec des souris normales et j'ai pu montrer la présence de rythmes au niveau du calcium sanguin et urinaire, mais également au niveau des hormones et gènes qui contrôlent le métabolisme du calcium dans le corps, comme la vitamine D et l'hormone parathyroidienne. De manière intéressante, j'ai observé que la plupart de ces gènes ont un rythme synchronisé. J'ai ensuite utilisé un modèle de souris dans lequel l'horloge interne a été génétiquement invalidée et j'ai montré que ces souris présentent une augmentation de leur excrétion urinaire de calcium et un rythme circadien altéré de la vitamine D dans le sang. Ces souris absorbent aussi moins bien le calcium intestinal et présentent une ostéoporose marquée. Ce travail montre donc que l'horloge interne est nécessaire pour établir un rythme circadiens de certains facteurs influant les flux de calcium dans l'organisme, comme la vitamine D, et que la perturbation de ces rythmes mène à une dérégulation du métabolisme osseux. Ainsi, la perturbation de l'horloge interne peut causer une ostéoporose et une hypercalciurie qui pourraient aboutir à la formation de fractures et de calculs rénaux. L'extrapolation de ces observations chez l'homme ou à des changements plus subtiles des rythmes circadiens, comme le décalage horaire, restent à montrer. Cette recherche a démontré que les rythmes circadiens des mécanismes de régulation des flux de calcium dans l'organisme sont essentiels au maintien d'un squelette normal et suggère que les perturbations des rythmes circadiens pourraient être une nouvelle cause de l'ostéoporose. - Maintaining constant calcium concentration in the plasma is of a crucial importance and three organs participate in normal calcium balance - kidney, gut and bone. Plasma calcium concentration is strictly regulated by parathyroid hormone (PTH) and vitamin D. Circadian variations of PTH, vitamin D and plasma calcium were previously described in humans, as well as in rats. Rhythms in serum PTH are important for balanced bone remodelling. Indeed in C57BL/6J mice, PTH injection once per day leads to an increase in bone mineral density (BMD), whilst continuous infusion is associated with decreased BMD. Vitamin D also plays a crucial role in bone physiology, since the deficiency in vitamin D can lead to rickets/osteomalacia. However, the role of vitamin D rhythms in bone homeostasis remains unknown. The circadian clock is an. internal time-keeping system generating rhythms in gene expression with 24h periodicity, in physiology and in behaviour. It is operated by positive- and negative-feedback loops of circadian genes, such as CLOCK, BMAL1, CRY1 and 2 or PERI and 2. In this work, we hypothesized, that calcium homeostasis is under the control of the circadian clock. First, we showed daily variations in urinary calcium and serum calcium, PTH and l,25(OH)2 vitamin D, together with renal mRNA and protein levels of genes involved in calcium homeostasis in C57BL/6J mice. Second, and to investigate the role of the circadian clock system in calcium handling, we studied mice lacking the gene CLOCK crucial for fonction of the clock system and compared them to the WT littermates. CLOCK-/- mice were hypercalciuric at all timepoints of the day. However, the circadian rhythm of calcium excretion was preserved. Serum calcium levels did not differ between the genotypes, but CLOCK-/- mice did not exhibit daily variation for this parameter. Loss of rhythm was observed also for serum l,25(OH)2 vitamin D levels, which may be one of the causes of altered bone microarchitecture that was revealed in CLOCK-/- mice. They displayed increased trabecular separation and decreased trabecular number, trabecular bone volume and trabecular bone surface, suggestive of osteoporosis. We found that the rhythm of the mRNA expression of CYP27B1 was abolished in the kidney of CLOCK-/- mice, which could induce the altered rhythm of l,25(OH)2 vitamin. Serum PTH levels were comparable between CLOCK-/- and WT mice. In the kidney, increased mRNA expression of TRPV5 and NCX1 suggests increased calcium reabsorption in the distal convoluted and connecting tubule. In the gut, intestinal calcium absorption was decreased in CLOCK¬/- mice, confirmed by decreased mRNA levels of TRPV6 and PMCA1. In summary, deletion of the CLOCK gene in mice conducts to hypercalciuria, alteration of the rhythm in serum calcium and l,25(OH)2D levels, and impainnent of their bone microarchitecture. In conclusion, these data show that the circadian clock system is essential in calcium homeostasis and bone physiology.

Circadian time-dependent effects of fencamfamine on inhibition of dopamine uptake and release in rat striatal slices

Fencamfamine (FCF) is a central stimulant that facilitates central dopaminergic transmission through inhibition of dopamine uptake and enhanced release of the transmitter. We evaluated the changes in the inhibition of uptake and the release of striatal [3H]-dopamine at 9:00 and 21:00 h, times corresponding to maximal and minimal behavioral responses to FCF, respectively. Adult male Wistar rats (200-250 g) maintained on a 12-h light/12-h dark cycle (lights on at 7:00 h) were used. In the behavioral experiments the rats (N = 8 for each group) received FCF (3.5 mg/kg, ip) or saline at 9:00 or 21:00 h. Fifteen minutes after treatment the duration of activity (sniffing, rearing and locomotion) was recorded for 120 min. The basal motor activity was higher (28.6 ± 4.2 vs 8.4 ± 3.5 s) after saline administration at 21:00 h than at 9:00 h. FCF at a single dose significantly enhanced the basal motor activity (38.3 ± 4.5 vs 8.4 ± 3.5 s) and increased the duration of exploratory activity (38.3 ± 4.5 vs 32.1 ± 4.6 s) during the light, but not the dark phase. Two other groups of rats (N = 6 for each group) were decapitated at 9:00 and 21:00 h and striata were dissected for dopamine uptake and release assays. The inhibition of uptake and release of [3H]-dopamine were higher at 9:00 than at 21:00 h, suggesting that uptake inhibition and the release properties of FCF undergo daily variation. These data suggest that the circadian time-dependent effects of FCF might be related to a higher susceptibility of dopamine presynaptic terminals to the action of FCF during the light phase which corresponds to the rats' resting period

Food and the circadian activity of the hypothalamic-pituitary-adrenal axis

Temporal organization is an important feature of biological systems and its main function is to facilitate adaptation of the organism to the environment. The daily variation of biological variables arises from an internal time-keeping system. The major action of the environment is to synchronize the internal clock to a period of exactly 24 h. The light-dark cycle, food ingestion, barometric pressure, acoustic stimuli, scents and social cues have been mentioned as synchronizers or" zeitgebers". The circadian rhythmicity of plasma corticosteroids has been well characterized in man and in rats and evidence has been accumulated showing daily rhythmicity at every level of the hypothalamic-pituitary-adrenal (HPA) axis. Studies of restricted feeding in rats are of considerable importance because they reveal feeding as a major synchronizer of rhythms in HPA axis activity. The daily variation of the HPA axis stress response appears to be closely related to food intake as well as to basal activity. In humans, the association of feeding and HPA axis activity has been studied under physiological and pathological conditions such as anorexia nervosa, bulimia, malnutrition, obesity, diabetes mellitus and Cushing's syndrome. Complex neuroanatomical pathways and neurochemical circuitry are involved in feeding-associated HPA axis modulation. In the present review we focus on the interaction among HPA axis rhythmicity, food ingestion, and different nutritional and endocrine states