The role of vasopressin in modulating circadian rhythm responses to phase shifts

Telemetered body temperature (BT), heart rate (HR), and motor activity (AC) data were collected in vasopressin-containing, Long-Evans (LE) and vasopressin-deficient, Brattleboro (DI) rats. In Experiment 1, the rats were initially exposed to a 12 h/12 h light/dark cycle under ad-libitum feeding and were then subjected to either a phase-advance or phase-delay shift of 6 h. After the phase-advance shift, neither strain adapted; however, after the phase-delay shift, both strains adapted rapidly. In Experiment 2, the animals were subjected to either a nocturnal or a diurnal restricted-feeding paradigm and were then exposed to either a phase-advance or phase-delay shift with synchronized feeding. In the nocturnal restricted-feeding paradigms, both strains rapidly adapted to both shifts. Concerning diurnal restricted-feeding, DI animals readily entrained to the presentation of food in both shifts; whereas, LE animals exhibited a confused rhythmicity. In Experiment 3, animals were subjected to a phase-advance shift, while the time of feeding was held constant. Following the shift, LE animals responded to the onset of the dark at the new time; yet, were still influenced by the presentation of food. The DI animals maintained the preshift circadian pattern and continued to be dominated by the presentation of food. These experiments indicate that circadian rhythms of LE animals are dominated by the light entrainable oscillator (LEO) in ad-libitum feeding and by both the LEO and food entrainable oscillator (FEO) in restricted-feeding. On the other hand, the circadian rhythms of DI animals are dominated by the FEO unless food is provided ad-libitum. The demonstrated role of vasopressin in synchronizing circadian rhythms to the LEO may be of significance in understanding human circadian rhythm disturbances, such as jet lag.     

Destruction of serotonergic neurons in the median raphe nucleus blocks circadian rhythm phase shifts to triazolam but not to novel wheel access

Systematic treatment of hamsters with triazolam (TRZ) or novel wheel (NW) access will yield PRCs similar to those for neuropeptide Y. Both TRZ and NW access require an intact intergeniculate leaflet (IGL) to modulate circadian rhythm phase. It is commonly suggested that both stimulus types influence rhythm phase response via a mechanism associated with drug-induced or wheel access-associated locomotion. Furthermore, there have been suggestions that one or both of these stimulus conditions require an intact serotonergic system for modulation of rhythm phase. The present study investigated these issues by making serotonin neuron-specific neurotoxic lesions of the median or dorsal raphe nuclei and evaluating phase response of the hamster circadian locomotor rhythm to TRZ treatment or NW access. The expected effect of TRZ injected at CT 6 h on the average phase advance was virtually eliminated by destruction of serotonin neurons in the median, but not the dorsal, raphe nucleus. No control or lesioned animal engaged in substantial wheel running in response to TRZ. By contrast, all median raphe-lesioned hamsters that engaged in substantial amounts of running when given access to a NW had phase shifts comparable to control or dorsal raphe-lesioned animals. The results demonstrate that serotonergic neurons in the median raphe nucleus contribute to the regulation of rhythm phase response to TRZ and that it is unlikely that these neurons are necessary for phase response to NW access. The data further suggest the presence of separate pathways mediating phase response to the two stimulus conditions. These pathways converge on the IGL, a nucleus afferent to the circadian clock, that is necessary for the expression of phase response to each stimulus type.     

Binocular rivalry and dichoptic masking: Suppressed stimuli do not mask stimuli in a dominating eye.

Reaction time (RT) was used to gauge the sensitivity of an eye during its dominant and suppressed phases of binocular rivalry. During dominance, performance was uniformly good in detecting both stimuli that were spatially identical to the suppressed stimulus and those that were different in spatial frequency. When suppressed eyes were tested, performance was poor when the stimulus was different from the dominating stimulus, but even worse when the test stimulus and the dominating stimulus were spatially identical. The results favor the view that suppression operates nonselectively on a monocular visual channel, prior to the point at which dichoptic pattern masking occurs. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of chronic tryptophan depletion on the circadian rhythm of wheel-running activity in rats

The effect of chronic treatment with a tryptophan (TRP)-free diet on the free-running circadian wheel-running rhythm and the central serotonergic system was investigated in blinded male rats. The long-term TRP-free diet did not change periods of activity, but disordered their patterns. This seemed to be due to masking, entrainment, enhancement of the morning activity, and obscuring of the activity onset as well as appearance of some periodic activities within the subjective night. A long-term TRP-fre diet decreased the concentration of TRP, 5-hydroxytryptamine (5-HT), and 5-hydroxyindoleacetic acid (5-HIAA) in all brain regions tested: frontal cortex, hippocampus, thalamus, hypothalamus, midbrain, and pons. Density of 5-HT1A receptor binding was significantly decreased in the frontal cortex and hypothalamus, whereas no significant change was observed in the density of 5-HT2 receptor binding in all regions. These results suggest that the period of primary circadian pacemaker is not affected, but its oscillation, as well as the coupling strength between the primary and secondary pacemakers, is weakened by the dysfunction of the serotonergic system caused by chronic TRP depletion.     

What neuroimaging and brain localization can do, cannot do and should not do for social psychology.

Interest in bridging social psychology and neuroscience has seen a significant upsurge. Much of this interest has centered on brain localization--the attempt to relate psychological events to locations of brain events. Although many articles have sought to localize brain activity that supports social behavior, scant attention has been paid to the specific methods to be used in integrating brain localization data into psychological theory. The authors describe 4 strategies psychologists can use to integrate brain localization data and psychological theory, and they consider whether social psychology presents special considerations in the use of these strategies. They conclude that brain localization offers a useful tool for some but not all problems in social psychology, and they discuss the types of problems for which it may and may not prove useful. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Serum leptin levels do not rise during pregnancy in age-matched rats

The serum leptin profile and its production in adipose tissue during pregnancy and lactation were investigated along with changes in appetite and factors reflecting nutritional status in 11-week-old rats. Serum leptin levels in pregnant rats were stable except on day 20 of pregnancy and significantly reduced during lactation compared to nonpregnant rats (P < 0.001). Circulating leptin levels corresponded with changes in appetite during pregnancy and postparturition. Leptin mRNA in parametrial adipose tissue reflected the circulating levels, also being significantly reduced during late pregnancy and during lactation (P < 0.05). Leptin mRNA expression was observed in placenta, but the amount suggested little influence on circulating leptin levels. These results indicate that reduction in leptin mRNA in parametrial adipose tissue and circulating leptin levels may increase appetite during late pregnancy and lactation and may play a role in regulating metabolic homeostasis around parturition in rats.     

Posture, age, menopause, and osteopenia do not influence the circadian variation in the urinary excretion of pyridinium crosslinks

This study was performed to investigate whether the circadian variation in urinary pyridinium crosslinks is related to physical activity, age, the menopause, and asymptomatic osteopenia. We measured urinary pyridinoline/creatinine (Pyr/Cr) and deoxypyridinoline/creatinine (D-Pyr/Cr) in 9 healthy premenopausal women in two 27 h studies, before and at the end of 5 days of total bed rest. Both Pyr/Cr and D-Pyr/Cr showed highly significant circadian variations, with the peak at night and the nadir during the day (p < 0.001). The 5 days of complete bed rest produced no changes in the circadian pattern, but a general increase of 28% was observed in pyridinium crosslinks. A group of 12 healthy, early postmenopausal women (aged 55 +/- 2 years), 12 healthy, elderly postmenopausal women (aged 73 +/- 1 years), and 12 elderly osteopenic but otherwise healthy women (aged 73 +/- 1 years) were also studied for 27 h. All three groups showed highly significant (p < or = 0.001) circadian variations in the urinary excretion of pyridinium crosslinks. As expected, both Pyr/Cr (p < 0.05) and D-Pyr/Cr (p < 0.001) increased at the time of menopause, but the circadian variations in Pyr/Cr and D-Pyr/Cr were similar in all groups studied. We conclude that the circadian variation in the urinary excretion of pyridinium crosslinks is independent of physical factors. Furthermore, the circadian variation in pyridinium crosslinks was not related to age, menopausal status, or asymptomatic osteopenia.     

Supplemental arginine and ornithine do not affect splenocyte proliferation in surgically treated rats

The present study was designed to determine whether arginine or ornithine supplementation enhanced immune responsiveness in surgically stressed rats. Young rats (130 to 150 g; n = 72) were fed one of three nonpurified diets: control, arginine-supplemented (30 g/kg of diet), or supplemented with ornithine on an equimolar basis to supplemental arginine. Control and ornithine-supplemented diets were made isonitrogenous to the arginine-supplemented diet with alanine. Food intake and body weight were monitored throughout the experimental period. Eight days after initiation of dietary treatments, 36 rats were given dorsal skin wounds. Rats were killed 7 days later. Blood was collected, spleen and thymus were weighed, and splenocytes were isolated to measure proliferation in response to mitogens and interleukin-2 production. Food intake, body weight gain, and thymus weight were lower in rats subjected to surgery than in controls rats (p < .01). Neither supplemental dietary arginine nor ornithine affected food intake, body weight gain, thymus weight, splenocyte proliferation, or splenocyte interleukin-2 production in any treatment group (p < .1). These data suggest that low-level dietary supplementation of arginine and ornithine did not ameliorate detrimental effects of minor surgery in rats.     

Olfactory bulbectomy impedes social but not photic reentrainment of circadian rhythms in female Octodon degus

Recent studies demonstrated that nonphotic (social) cues markedly accelerate reentrainment to large phase shifts of the light-dark (LD) cycles in female Octodon degus and that such changes are likely effected by chemosensory stimuli. This experiment investigated the effects of olfactory bulbectomies on (1) socially facilitated reentrainment rates of circadian rhythms following a 6-h phase advance of the LD cycle, (2) photic reentrainment rates of circadian rhythms following a 6-h advance of the LD cycle, (3) photic entrainment, and (4) the circadian period (tau) of activity rhythms in constant darkness (DD). olfactory bulbectomies (BX) blocked socially facilitated reentrainment rates but did not alter reentrainment rates of circadian rhythms to photic cues alone. In addition, BX lowered mean daily locomotor activity levels and decreased the amplitude of the activity rhythm in degus housed in entrained (LD 12:12) conditions but did not alter the phase of activity onset or offset, duration (alpha) of activity, or mean daily core body temperature. Bulbectomies also failed to modify tau of free-running activity rhythms. This experiment confirms that the olfactory bulbs and chemosensory cues are necessary for socially facilitated reentrainment. In contrast to their effects in nocturnal rodents, BX do not produce significant circadian photic changes in diurnal degus. This is the first experiment to determine that chemosensory stimuli modulate the circadian system in a diurnal rodent.     

Effects of corticotropin-releasing factor on circadian locomotor rhythm in the golden hamster

Stress produces a reduction in the amplitude of some circadian rhythms. The neurochemical mechanisms underlying stress-induced changes in circadian rhythms are not known. To investigate a possible role of corticotropin-releasing factor (CRF) in this phenomenon, three related experiments were carried out: activity rhythms of male golden hamsters (10/14 hours light/dark entrained, lights on at 0800 h) were measured 1) following the intracerebroventricular administration of CRF (0.5, 1.0, 2.0, or 4.0 microg) at two different times of day, 2) following social stress (30-min resident-intruder confrontation), 3) and following the administration of the CRF-antagonist alpha-helical CRF9-41 (2.0 microg) prior to a 15-min resident-intruder confrontation. CRF produced a significant, dose-related decrease in circadian rhythm amplitude following administration in the morning hours, but not in the afternoon. CRF also induced transient increases in activity post injection concomitant with an activation of the hypothalamic-pituitary-adrenocortical (HPA) system. Stress similarly reduced the amplitude of activity patterns and stimulated the HPA system. The stress-induced depression of circadian rhythm amplitude was significantly attenuated following alpha-helical CRF9-41. These data suggest a role for CRF in the stress-related modulation of circadian locomotor rhythm amplitude.     

Antigenic stimuli do not influence thymic B lymphocytes: a morphological and functional study in germ-free and conventionally reared piglets

We have recently reported that thymic B lymphocytes (TBL) are the first B-cell subpopulation undergoing isotype switching to IgG and IgA during embryonic life. The aim of this study is to analyze the influence of antigenic stimulation on TBL location and activity using a germ-free (GF) newborn pig model, in which maternal antibodies and antigens do not affect B-cell development. Immunohistological analysis showed that TBL were disseminated mainly in the thymic medulla. There were no differences in the distribution of TBL, both in GF newborn piglets before and after colonization with Escherichia coli and in older conventionally reared (CONV) piglets. The number of immunoglobulin (Ig)-secreting cells measured by the ELISPOT method was not influenced by microflora and food antigens. IgM-positive cells secreting IgM and CD45RC-positive cells spontaneously producing IgM, IgG, and IgA were detected in newborn thymus. Our findings suggest that TBL differentiation and Ig switching to IgG and IgA-secreting cells is not influenced by external antigens and that the thymic microenvironment plays an important role in this process.     

Locus coeruleus neurons from morphine-treated rats do not show opiate-withdrawal hyperactivity in vitro

Aqueous biphasic systems (ABS) and aqueous biphasic extraction chromatographic (ABEC) resins are currently under investigation for their utility in the removal of color from textile plant wastes. The structures of several widely used food colorings, suggest that these dyes would also be retained on the resins. In work currently in progress, we have begun to investigate the retention and resolution of several common food colorings including indigo carmine, amaranth, carminic acid. erythrosin B, tartrazine and quinoline yellow. The relationship between the uptake of these dyes on ABEC resins in terms of the binding strengths and capacities of the resins and their partitioning behavior in ABS is illustrated. Some possible theoretical and practical approaches to the prediction of the partitioning and retention behavior is discussed.     

Infant color vision: moving tritan stimuli do not elicit directionally appropriate eye movements in 2- and 4-month-olds

The purpose of the present study was to investigate the capacity of infants to code the direction of motion of moving tritan-modulated gratings. Infant and adult subjects were tested with 0.2 c/d sinusoidal gratings moving at a speed of 20 deg/sec. Three conditions were tested: luminance-modulated gratings, tritan-modulated gratings, and luminance- vs tritan-modulated gratings superimposed and moving in opposite directions in a chromatic motion nulling paradigm. Two-month-old infants were tested in all three conditions, while 4-month-olds were tested in only the first two conditions. For infant subjects, an adult observer reported the direction of the slow phase of the infant's eye movements; adult subjects judged the perceived direction of motion of the stimuli. Luminance-modulated gratings produced directionally appropriate eye movements (DEM) in all age groups. Tritan gratings presented alone did not produce DEM in either 2- or 4-month-olds, but did so in adults. Mean equivalent luminance contrasts were near zero in 2-month-olds, and small but reliably above zero in adults. In sum, the present study provides no evidence that infants can code the direction of motion of moving tritan gratings.     

Lesions of the perirhinal cortex do not impair integration of visual and geometric information in rats.

Rats with lesions of the perirhinal cortex and a control group were required to find a platform in 1 corner of a white rectangle and in the reflection of this corner in a black rectangle. Test trials revealed that these groups were able to integrate information regarding the shape of the pool and the color of its walls (black or white) to identify the correct location of the platform. A clear effect of the perirhinal cortex lesions was, however, revealed using an object recognition task that involved the spontaneous exploration of novel objects. The results challenge the view that the perirhinal cortex enables rats to solve discriminations involving feature ambiguity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Increased histidine preference during specific alteration of rhythm of environmental temperature stress in rats.

It has been reported that specific alteration of rhythm of environmental temperature (SART) stress induces various physiological changes. In this study, changes in taste preference during SART stress were investigated in rats. Rats were given free access to six amino acid solutions, saline, and water in a choice paradigm. During SART stress, daily food intake increased significantly by 50% whereas the rate of body weight gain decreased significantly to one third that observed during the prestress baseline period. In addition, consumption of histidine solution increased significantly, whereas intakes of water, monosodium glutamate, saline, glycine, arginine, lysine, and threonine were unaffected. Results suggest that a specific preference for histidine emerges during SART stress, which may be related to the stress-induced changes in the histamine turnover in the brain and peripheral tissues. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Prenatal stress and prepuberal social rearing conditions interact to determine sexual behavior in male rats.

The possible interaction between relative amounts of androgen present during specific stages of development and adequate prepuberal social stimulation was evaluated by characterizing the ejaculatory and lordotic behavior potentials of 20 prenatally stressed and 23 control male Sprague-Dawley rats that had been weaned at 16 days of age and raised either in total social isolation or with a same-age female, a control male, or a prenatally stressed male. The decrement in male sexual behavior produced by prenatal stress was attenuated by raising the male with either a female or a control male. Social isolation alone or in combination with stress resulted in severely deficient male behavior. Peripheral skin shock promoted ejaculatory behavior in many previously noncopulating, prenatally stressed males raised with other stressed males, but it was ineffective in most isolated Ss. The high lordosis potential characteristic of prenatally stressed male rats was slightly lower in the group with a female cagemate and was markedly decreased by social isolation. Results support and extend the finding by J. L. Dunlap et al (see record 1980-11465-001) that prenatal hormonal events and prepuberal rearing conditions can interact to attenuate or accentuate the effects that either treatment alone has on the development of adult sexual behavior potentials. (27 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differential pattern of the circadian rhythm of serum melatonin in young and elderly healthy subjects

The daily profile of serum level of melatonin was studied in 10 young and 13 elderly subjects. All of the subjects were physically and psychiatrically healthy and did not have any clinical symptoms related to rhythm disturbance. Blood samples were taken every 3 h for 1 day and serum melatonin levels were determined by RIA. All except for 1 of the elderly subjects exhibited a clear circadian rhythm of serum melatonin level with a nocturnal peak. In both subject groups, the melatonin rhythm showed significant diurnal variation. There was no significant difference in the total melatonin level per day between young and elderly groups, suggesting that there was no influence of aging on daily total melatonin secretion. However, there was a marked difference in the features of the melatonin rhythm between the two groups, i.e., a rapid decline of the melatonin level from the nocturnal peak in the elderly group, suggesting that the off-set time of melatonin secretion advances with aging. Our findings suggest that the pattern of melatonin rhythm alters significantly without clear clinical symptoms in the process of senescence.