Behavioral effects of LPS in adult, middle-aged and aged mice

Acute infections lead to alterations in behavior, collectively known as sickness behavior. which includes reduction in locomotion, food ingestion, sexual and social behavior, environmental exploration, and sleep profile. Although generally seen as undesired, sickness behavior represents a conserved strategy for animals to overcome disease. Aging process is associated with a variety of changes in immunity, which are referred to as immunosenescence, and include higher mortality by infectious diseases. Few works studied sickness behavior display in old animals. Thus, we sought to investigate the display of sickness related behaviors on aged mice. Adult(3-6 months old), middle-aged (12-15 m) and aged mice (18-22 m)were treated with i.p. LPS (200 mu g/kg) and their behaviors were assessed in the open field and in the elevated plus-maze. Exploratory activity was similar in aged mice treated or not with LPS in both apparati. In the open field, locomotion remained at baseline levels; in the elevated plus-maze, there was a time-dependent decrease in motor activity. (C) 2008 Elsevier Inc. All rights reserved

Nitric oxide synthase inhibitors improve prepulse inhibition responses of Wistar rats

Introduction: Cognitive and attentional deficits in schizophrenia include impairment of the sensorimotor filter as measured by prepulse inhibition (PPI). In this way, the study of animals that naturally present low PPI responses could be a useful approach for screening new antipsychotic drugs. Several pieces of evidence suggest that dopamine and nitric oxide (NO) can modulate PPI but their role in those animals is unknown. Objectives: The aim of this study was to investigate the role of dopamine and NO in Wistar rats with naturally low PPI response. Methods: Male Wistar rats with low PPI responses received an i.p. injection of the antipsychotics haloperidol (0.1, 0.3 or 1 mg/kg) or clozapine (0.5, 1.5 or 5 mg/kg), the anxiolytic diazepam (1 or 3 mg/kg) or the NO synthase (NOS) inhibitors, N(G)- nitro-L-arginine (L-NOARG; 40 mg/kg, acutely or sub-chronically) or 7-Nitroindazole (7-NI; 3, 10 or 30 mg/kg). All animals were submitted to the PPI test 1 h after injection. Striatal and cortical dopamine, DOPAC, and noradrenaline levels of rats with low PPI responses were compared to rats with normal PPI responses. Results: We found increased levels of catecholamines on the striatum and prefrontal cortex of Wistar rats with low PPI. In these animals, both antipsychotics, typical and atypical, and NOS inhibitors significantly increased PPI. Conclusion: Taken together, our findings suggest that the low PPI phenotype may be driven by an over-active catecholamine system. Additionally, our results corroborate the hypothesis of dopamine and NO interaction on PPI modulation and suggest that Wistar rats with low PPI may represent an interesting non-pharmacological model to evaluate new potential antipsychotics. (C) 2010 Elsevier B.V. All rights reserved.

Functional mapping of the periaqueductal gray matter involved in organizing tonic immobility behavior in guinea pigs

Tonic immobility behavior (TI) is an innate response characterized by profound motor inhibition that is exhibited by prey when physical contact with a predator is prolonged and the situation inescapable. The periaqueductal gray matter (PAG) is intimately associated with the somatic and autonomic components of defensive reactions. This study investigated whether the TI response was able to recruit specific functional columns of the PAG by examining c-fos immunolocalization in guinea pigs. In the TI group, the innate response was invoked in animals through inversion and physical contention for at least 15 min. In the control group, the animals were physically manipulated only. Our results demonstrate that the defensive behavior of TI is capable of promoting the expression of Fos protein in different areas of the PAG, with higher levels of staining in the ventrolateral (vI) and lateral (I) columns. In addition, our results demonstrate increased Fos immunoreactivity (FOS-IR) in the dorsal raphe nucleus, the Edinger-Westphal nucleus, the cuneiform nucleus and the superior colliculus. In contrast, there were no significant alterations in the number of FOS-IR cells in the inferior colliculus or the oculomotor nucleus. Analysis of the results suggests that neuronal activation after the TI response differs by functional column of the PAG. (C) 2010 Elsevier B.V. All rights reserved.

Nitric oxide modulation of methylphenidate-induced disruption of prepulse inhibition in Swiss mice

Drugs that facilitate dopaminergic neurotransmission induce cognitive and attentional deficits which include inability to filter sensory input measured by prepulse inhibition (PPI) Methylphenidate, an amphetamine analog is used in the treatment of attention deficit hyperactivity disorder Given that nitric oxide (NO) modulates dopamine effect our aim is to analyze the nitric oxide synthase (NOS) and soluble guanylate cyclase (sGC) inhibitors effect on PPI disruption induced by methylphenidate The inhibitors effects were compared to those produced by haloperidol and clozapine Male Swiss mice received a first I p. Injection (one hour before testing), of either saline, or N(G) nitro L-arginine (10, 40 or 90 mg/kg) or 7-Nitroindazole (3, 10, 30 or 60 mg/kg). or oxadiazolo-quinoxalin (5 or 10 mg/kg). or haloperidol (1 mg/kg), or clozapine (5 mg/kg) Thirty min later mice received the second injection of either saline or methylphenidate (20 or 30 mg/kg) or amphetamine (5 or 10 mg/kg). One group of mice received intracerebroventricular 7-Nitroindazole (50 or 100 nM) followed by systemic administration of saline or methylphenidate (30 mg/kg) The results revealed a methylphenidate dose-dependent disruption of PPI comparable to amphetamine. The effect was prevented by either nitric oxide synthase or guanilate cyclase inhibitors or clozapine or haloperidol In conclusion, methylphenidate induced a dose-dependent PPI disruption in Swiss mice modulated by dopamine and NO/sGC. The results corroborate the hypothesis of dopamine and NO interacting to modulate sensorimotor gating through central nervous system. It may be useful to understand methylphenidate and other psychostimulants effects (C) 2009 Elsevier B.V All rights reserved

Role of central nitric oxide in behavioral thermoregulation of toads during hypoxia

Nitric oxide (NO) is thought to play a key role in the development of hypoxia-induced anapyrexia in mammals, acting on the preoptic region of the anterior hypothalamus to activate autonomic heat loss responses. Regarding behavioral thermoregulation, no data exists for NO modulation/mediation of thermoregulatory behavior changes during hypoxia. Therefore, we tested the hypothesis that NO is involved in the preferred body temperature (Tb) reduction in the hypoxic toad Chaunus schneideri (formerly Bufo paracnemis), a primarily behavioral thermoregulator. Toads equipped with a temperature probe were placed in a thermal gradient chamber, and preferred Tb was monitored continuously. We analyzed the effect of intracerebroventricular injections of the nonselective NO synthase inhibitor L-NMMA (200, 400 and 800 microg per animal) or mock cerebrospinal fluid (mCSF, vehicle) on the preferred Tb of toads. No significant difference in preferred Tb was observed after L-NMMA treatments. Another group of toads treated with 2 mg kg(-1) (400 microg per animal) of L-NMMA or mCSF was submitted to hypoxia (3% inspired 02) for 8 h. The vehicle group showed a reduction of preferred Tb, a response that was inhibited by L-NMMA. A 3rd group of hypoxic animals was injected with Ringer or L-NMMA (2 mg kg(-1)) into the lymph sac and both treatments induced no change in the anapyretic response to hypoxia. These results indicate that NO acting on the central nervous system has an excitatory role for the development of hypoxia-induced anapyrexia in toads. (C) 2008 Elsevier Inc. All rights reserved.

Imitation, mirror neurons and autism

Various deficits in the cognitive functioning of people with autism have been documented in recent years but these provide only partial explanations for the condition. We focus instead on an imitative disturbance involving difficulties both in copying actions and in inhibiting more stereotyped mimicking, such as echolalia. A candidate for the neural basis of this disturbance may be found in a recently discovered class of neurons in frontal cortex, 'mirror neurons' (MNs). These neurons show activity in relation both to specific actions performed by self and matching actions performed by others, providing a potential bridge between minds. MN systems exist in primates without imitative and 'theory of mind' abilities and we suggest that in order for them to have become utilized to perform social cognitive functions, sophisticated cortical neuronal systems have evolved in which MNs function as key elements. Early developmental failures of MN systems are likely to result in a consequent cascade of developmental impairments characterised by the clinical syndrome of autism. Crown Copyright (C) 2001 Published by Elsevier Science Ltd. All rights reserved.

Variations in cone photoreceptor abundance and the visual ecology of birds

The relative abundance and topographical distribution of retinal cone photoreceptors was measured in 19 bird species to identify possible correlations between photoreceptor complement and visual ecology. In contrast to previous studies, all five types of cone photoreceptor were distinguished, using bright field and epifluorescent light microscopy, in four retinal quadrants. Land birds tended to show either posterior dorsal to anterior ventral or anterior dorsal to posterior ventral gradients in cone photoreceptor distribution, fundus coloration and oil droplet pigmentation across the retina. Marine birds tended to show dorsal to ventral gradients instead. Statistical analyses showed that the proportions of the different cone types varied significantly across the retinae of all species investigated. Cluster analysis was performed on the data to identify groups or clusters of species on the basis of their oil droplet complement. Using the absolute percentages of each oil droplet type in each quadrant for the analysis produced clusters that tended to reflect phylogenetic relatedness between species rather than similarities in their visual ecology. Repeating the analysis after subtracting the mean percentage of a given oil droplet type across the whole retina (the 'eye mean') from the percentage of that oil droplet type in each quadrant, i.e. to give a measure of the variation about the mean, resulted in clusters that reflected diet, feeding behaviour and habitat to a greater extent than phylogeny.

Nocturnal activity in the green sea turtle alters daily profiles of melatonin and corticosterone

In nature, green turtles (Chelonia mydas) can exhibit nocturnal activity in addition to their typically diurnal activity cycle. We examined whether nocturnal activity in captive and free-living green turtles altered daily plasma profiles of melatonin (MEL) and corticosterone (CORT). In captivity, diurnally active green turtles expressed distinct diel cycles in MEL and CORT; a nocturnal rise was observed in MEL and a diurnal rise was observed in CORT. However, when induced to perform both low- and high-intensity nocturnal activity, captive green turtles exhibited a significant decrease in MEL, compared to inactive controls. In contrast, plasma CORT increased significantly with nocturnal activity, and further, the relative increase in CORT was correlated with the intensity of the nocturnal behavior. In free-living green turtles that performed nocturnal activity including: nesting, mate searching, and feeding/swimming behaviors, plasma profiles in MEL and CORT exhibited relatively little, or no, daily fluctuation. Our findings demonstrate that nocturnal activity in green turtles is often associated with MEL and CORT profiles that resemble those measured during the day. We speculate that these conspicuous changes in MEL and CORT during nocturnal activity could either support or promote behaviors that enable acquisition of transient resources important to the survival and reproductive success of green turtles. (C) 2002 Elsevier Science (USA).

Axon navigation in the mammalian primary olfactory pathway: Where to next?

The process of establishing long-range neuronal connections can be divided into at least three discrete steps. First, axons need to be stimulated to grow and this growth must be towards appropriate targets. Second, after arriving at their target, axons need to be directed to their topographically appropriate position and in some cases, such as in cortical structures, they must grow radially to reach the correct laminar layer Third, axons then arborize and form synaptic connections with only a defined subpopulation of potential post-synaptic partners. Attempts to understand these mechanisms in the visual system have been ongoing since pioneer studies in the 1940s highlighted the specificity of neuronal connections in the retino-tectal pathway. These classical systems-based approaches culminated in the 1990s with the discovery that Eph-ephrin repulsive interactions were involved in topographical mapping. In marked contrast, it was the cloning of the odorant receptor family that quickly led to a better understanding of axon targeting in the olfactory system. The last 10 years have seen the olfactory pathway rise in prominence as a model system for axon guidance. Once considered to be experimentally intractable, it is now providing a wealth of information on all aspects of axon guidance and targeting with implications not only for our understanding of these mechanisms in the olfactory system but also in other regions of the nervous system.

Lateralization of speech production using verbal/manual dual tasks: meta-analysis of sex differences and practice effects

The present paper reviews the findings of 30 years of verbal/manual dual task studies, the method most commonly used to assess lateralization of speech production in non-clinical samples. Meta-analysis of 64 results revealed that both the type of manual task used and the nature of practice that is given influence the size of the laterality effect. A meta-analysis of 36 results examining the effect size of sex differences in estimate,, of lateralization of speech production indicated that males appear to show, slightly larger laterality effects than females. (C) 2002 Elsevier Science Ltd. All rights reserved.

The distribution and morphological characteristics of catecholaminergic cells in the brain of monotremes as revealed by tyrosine hydroxylase immunohistochemistry

The present study describes the distribution and cellular morphology of catecholaminergic neurons in the CNS of two species of monotreme, the platypus (Ornithorhynchus anatinus) and the short-beaked echidna (Tachyglossus aculeatus). Tyrosine hydroxylase immunohistochemistry was used to visualize these neurons. The standard A1-A17, C1-C3 nomenclature was used for expediency, but the neuroanatomical names of the various nuclei have also been given. Monotremes exhibit catecholaminergic neurons in the diencephalon (All, A12, A13, A14, A15), midbrain (A8, A9, A10), rostral rhombencephalon (A5, A6, A7), and medulla (A1, A2, C1, C2). The subdivisions of these neurons are in general agreement with those of other mammals, and indeed other amniotes. Apart from minor differences, those being a lack of A4, A3, and C3 groups, the catecholaminergic system of monotremes is very similar to that of other mammals. Catecholaminergic neurons outside these nuclei, such as those reported for other mammals, were not numerous with occasional cells observed in the striatum. It seems unlikely that differences in the sleep phenomenology of monotremes, as compared to other mammals, can be explained by these differences. The similarity of this system across mammalian and amniote species underlines the evolutionary conservatism of the catecholaminergic system. Copyright (C) 2002 S. Karger AG, Basel.

The distribution and morphological characteristics of serotonergic cells in the brain of monotremes

The distribution and cellular morphology of serotonergic neurons in the brain of two species of monotremes are described. Three clusters of serotonergic neurons were found: a hypothalamic cluster, a cluster in the rostral brainstem and a cluster in the caudal brainstem. Those in the hypothalamus consisted of two groups, the periventricular hypothalamic organ and the infundibular recess, that were intimately associated with the ependymal wall of the third ventricle. Within the rostral brainstem cluster, three distinct divisions were found: the dorsal raphe nucleus (with four subdivisions), the median raphe nucleus and the cells of the supralemniscal region. The dorsal raphe was within and adjacent to the periaqueductal gray matter, the median raphe was associated with the midline ventral to the dorsal raphe, and the cells of the supralemniscal region were in the tegmentum lateral to the median raphe and ventral to the dorsal raphe. The caudal cluster consisted of three divisions: the raphe obscurus nucleus, the raphe pallidus nucleus and the raphe magnus nucleus. The raphe obscurus nucleus was associated with the dorsal midline at the caudal-most part of the medulla oblongata. The raphe pallidus nucleus was found at the ventral midline of the medulla around the inferior olive. Raphe magnus was associated with the midline of the medulla and was found rostral to both the raphe obscurus and raphe pallidus. The results of our study are compared in an evolutionary context with those reported for other mammals and reptiles. Copyright (C) 2002 S. Karger AG, Basel.

The distribution and morphological characteristics of cholinergic cells in the brain of monotremes as revealed by ChAT immunohistochemistry

The present study employs choline acetyltransferase (ChAT) immunohistochemistry to identify the cholinergic neuronal population in the central nervous system of the monotremes. Two of the three extant species of monotreme were studied: the platypus (Omithorhynchus anatinus) and the short-beaked echidna (Tachyglossus aculeatus). The distribution of cholinergic cells in the brain of these two species was virtually identical. Distinct groups of cholinergic cells were observed in the striatum, basal forebrain, habenula, pontomesencephalon, cranial nerve motor nuclei, and spinal cord. In contrast to other tetrapods studied with this technique, we failed to find evidence for cholinergic cells in the hypothalamus, the parabigeminal nucleus (or nucleus isthmus), or the cerebral cortex. The lack of hypothalamic cholinergic neurons creates a hiatus in the continuous antero-posterior aggregation of cholinergic neurons seen in other tetrapods. This hiatus might be functionally related to the phenomenology of monotreme sleep and to the ontogeny of sleep in mammals, as juvenile placental mammals exhibit a similar combination of sleep elements to that found in adult monotremes. Copyright (C) 2002 S. Karger AG, Basel.

Testosterone is correlated with courtship but not aggression in the tropical buff-banded rail, Gallirallus philippensis

Past studies into the roles of testosterone in birds have focused on species that occur in temperate regions. In such species, plasma testosterone levels are high during the establishment of territories in the spring and are associated with increased aggression. In contrast to most temperate species, tropical birds frequently defend territories year-round, during which time territoriality often occurs in a nonsexual context. The few studies that have been carried out on tropical birds show lower levels of circulating testosterone than occur in their temperate counterparts. In some year-round territorial tropical species, testosterone and aggression are dissociated, while in other species testosterone still plays a role in regulating aggression. This study examined the relationship between aggression and plasma testosterone levels in a year-round territorial, subtropical population of the buff-banded rail with characteristics typical of tropical species. Peak testosterone levels were substantially lower than those found in temperate species. Males displayed a seasonal peak in plasma testosterone level when their partners were most likely to be fertile. At other times, testosterone levels were mostly undetectable, despite year-round territoriality. We found that T levels increased with courtship behavior but showed no relationship with aggression, supporting the hypothesis that dissociation between testosterone and territoriality may be widespread among tropical avian taxa. (C) 2003 Elsevier Science (USA). All rights reserved.