Cardiovascular effects of L-glutamate injected in the medial prefrontal cortex of spontaneously hypertensive rats

We have previously reported that L-glutamate (L-glu) injected into the ventral portion of medial prefrontal cortex (vMPFC) of unanesthetized normotensive Wistar rats elicited cardiovascular responses. In the present study we investigated whether the spontaneously hypertensive rat (SHR) exhibit abnormal cardiovascular responses after L-glu microinjection in the vMPFC. Microinjections of L-glu (3, 9, 27, 81 or 150 nmol/200 nl) caused long-lasting dose-related depressor and bradycardiac responses in unanesthetized SHR (n = 6, each dose). Pressor and tachycardiac responses were evoked after the injection of 81 nmol of L-glu in the vMPFC of normotensive Wistar rats (n=6). Systemic pretreatment with the betal-adrenoceptor antagonist atenolol (1.5 mg/kg, i.v.) had no effect on L-glu cardiovascular responses evoked in the SHR (n=5). However, the treatment with the muscarinic antagonist homatropine methyl bromide (I mg/kg, i.v.) blocked the bradycardiac response to L-glu, without significant effects on depressor response evoked by L-glu in the SHR (n = 5). These results indicate that the bradycardiac response to the injection of L-glu injection in the vMPFC is due to activation of the parasympathetic system and not to inhibition of the cardiac sympathetic input. In conclusion, results indicate opposite cardiovascular responses when L-glu was microinjected in the vMPFC of unanesthetized SHR or normotensive. The bradycardiac response observed in the SHR was due to parasympathetic activation and was not affected by pharmacological blockade of the cardiac sympathetic output. (C) 2007 Elsevier B.V. All rights reserved.

Cadmium levels in the lung, liver, kidney cortex, and urine samples from Australians without occupational exposure to metals

The authors undertook this study to assess levels of cadmium exposure in the general population. Samples of lung, liver, and kidney were obtained from 61 cadavers (43 males, 18 females; 2-89 yr of age, mean age = 38.5 yr) who died from accidental causes and who were subject to postmortem examinations at the John Tonge Centre for Forensic Sciences, Queensland Health Scientific Services, Brisbane, Australia, in 1997 and 1998. Samples of bladder urine were also obtained from 22 cadavers. Tissue and urine samples were analyzed for cadmium, zinc, and copper with inductively coupled plasm (ICP) mass spectrometry. The overall mean values for cadmium in the lung, liver, and kidney cortex samples were 0.13, 0.95, and 15.45 mug/gm wet tissue weight. The average renal cadmium level in subjects with high lung-cadmium levels (n = 13) was 6 mug/gm wet tissue weight higher than that of similarly aged subjects who had medium lung-cadmium levels (n = 30). In females, the average level of cadmium in the liver was 74% greater than in males, and the average liver cadmium in females with high lung-cadmium levels was 100% higher than in males in the same age range who had the same high lung-cadmium levels. Renal cadmium accumulation tended to be greater in females than in males who were in the same age range and who had similar lung-cadmium levels, a result that suggested that there was a higher absorption rate of cadmium in females. The mean value for a urinary cadmium excretion of 2.30 mug/gm creatinine was found in a subset of samples that had a mean age of 39 yr and a renal cortex cadmium concentration of 18.6 mug/gm wet tissue weight. Urinary cadmium excretion rates were correlated more strongly with lung and kidney cadmium content than with age or liver cadmium levels. The results suggest that urinary cadmium excretion may be increased in smokers and could provide some estimate of body cadmium burdens in future Australian epidemiological studies.

Cortex, cognition and the cell: New insights into the pyramidal neuron and prefrontal function

Arguably the most complex conical functions are seated in human cognition, the how and why of which have been debated for centuries by theologians, philosophers and scientists alike. In his best-selling book, An Astonishing Hypothesis: A Scientific Search for the Soul, Francis Crick refined the view that these qualities are determined solely by cortical cells and circuitry. Put simply, cognition is nothing more, or less, than a biological function. Accepting this to be the case, it should be possible to identify the mechanisms that subserve cognitive processing. Since the pioneering studies of Lorent de No and Hebb, and the more recent studies of Fuster, Miller and Goldman-Rakic, to mention but a few, much attention has been focused on the role of persistent neural activity in cognitive processes. Application of modern technologies and modelling techniques has led to new hypotheses about the mechanisms of persistent activity. Here I focus on how regional variations in the pyramidal cell phenotype may determine the complexity of cortical circuitry and, in turn, influence neural activity. Data obtained from thousands of individually injected pyramidal cells in sensory, motor, association and executive cortex reveal marked differences in the numbers of putative excitatory inputs received by these cells. Pyramidal cells in prefrontal cortex have, on average, up to 23 times more dendritic spines than those in the primary visual area. I propose that without these specializations in the structure of pyramidal cells, and the circuits they form, human cognitive processing would not have evolved to its present state. I also present data from both New World and Old World monkeys that show varying degrees of complexity in the pyramidal cell phenotype in their prefrontal cortices, suggesting that cortical circuitry and, thus, cognitive styles are evolving independently in different species.

Neurochemical profile of the developing mouse cortex determined by in vivo 1H NMR spectroscopy at 14.1 T and the effect of recurrent anaesthesia.

The neurochemical profile of the cortex develops in a region and time specific manner, which can be distorted by psychiatric and other neurological pathologies. Pre-clinical studies often involve experimental mouse models. In this study, we determined the neurochemical profile of C57BL/6 mice in a longitudinal study design to provide a reference frame for the normal developing mouse cortex. Using in vivo proton NMR spectroscopy at 14 T, we measured the concentrations of 18 metabolites in the anterior and posterior cortex on postnatal days (P) 10, 20, 30, 60 and 90. Cortical development was marked by alterations of highly concentrated metabolites, such as N-acetylaspartate, glutamate, taurine and creatine. Regional specificity was represented by early variations in the concentration of glutamine, aspartate and choline. In adult animals, regional concentration differences were found for N-acetylaspartate, creatine and myo-inositol. In this study, animals were exposed to recurrent isoflurane anaesthesia. Additional experiments showed that the latter was devoid of major effects on behaviour or cortical neurochemical profile. In conclusion, the high sensitivity and reproducibility of the measurements achieved at 14 T allowed us to identify developmental variations of cortical areas within the mouse cortex.

Differential distribution of tau proteins in developing cat cerebral cortex and corpus callosum.

During the postnatal development of cat visual cortex and corpus callosum the molecular composition of tau proteins varied with age. In both structures, they changed between postnatal days 19 and 39 from a set of two juvenile forms to a set of at least two adult variants with higher molecular weights. During the first postnatal week, tau proteins were detectable with TAU-1 antibody in axons of corpus callosum and visual cortex, and in some perikarya and dendrites in the visual cortex. At later ages, tau proteins were located exclusively within axons in all cortical layers and in the corpus callosum. Dephosphorylation of postnatal day 11 cortical tissue by alkaline phosphatase strongly increased tau protein immunoreactivity on Western blots and in numerous perikarya and dendrites in all cortical layers, in sections, suggesting that some tau forms had been unmasked. During postnatal development the intensity of this phosphate-dependent somatodendritic staining decreased, but remained in a few neurons in cortical layers II and III. On blots, the immunoreactivity of adult tau to TAU-1 was only marginally increased by dephosphorylation. Other tau antibodies (TAU-2, B19 and BR133) recognized two juvenile and two adult cat tau proteins on blots, and localized tau in axons or perikarya and dendrites in tissue untreated with alkaline phosphatase. Tau proteins in mature tissue were soluble and not associated with detergent-resistant structures. Furthermore, dephosphorylation by alkaline phosphatase resulted in the appearance of more tau proteins in soluble fractions. Therefore tau proteins seem to alter their degree of phosphorylation during development. This could affect microtubule stability as well as influence axonal and dendritic differentiation.

Nurture versus nature: long-term impact of forced right-handedness on structure of pericentral cortex and basal ganglia.

Does a conflict between inborn motor preferences and educational standards during childhood impact the structure of the adult human brain? To examine this issue, we acquired high-resolution T1-weighted magnetic resonance scans of the whole brain in adult "converted" left-handers who had been forced as children to become dextral writers. Analysis of sulcal surfaces revealed that consistent right- and left-handers showed an interhemispheric asymmetry in the surface area of the central sulcus with a greater surface contralateral to the dominant hand. This pattern was reversed in the converted group who showed a larger surface of the central sulcus in their left, nondominant hemisphere, indicating plasticity of the primary sensorimotor cortex caused by forced use of the nondominant hand. Voxel-based morphometry showed a reduction of gray matter volume in the middle part of the left putamen in converted left-handers relative to both consistently handed groups. A similar trend was found in the right putamen. Converted subjects with at least one left-handed first-degree relative showed a correlation between the acquired right-hand advantage for writing and the structural changes in putamen and pericentral cortex. Our results show that a specific environmental challenge during childhood can shape the macroscopic structure of the human basal ganglia. The smaller than normal putaminal volume differs markedly from previously reported enlargement of cortical gray matter associated with skill acquisition. This indicates a differential response of the basal ganglia to early environmental challenges, possibly related to processes of pruning during motor development.

The roles of perirhinal cortex, postrhinal cortex, and the fornix in memory for objects, contexts, and events in the rat

Investigation of the anatomical substructure of the medial temporal lobe has revealed a number of highly interconnected areas, which has led some to propose that the region operates as a unitary memory system. However, here we outline the results of a number of studies from our laboratories, which investigate the contributions of the rat's perirhinal cortex and postrhinal cortex to memory, concentrating particularly on their respective roles in memory for objects. By contrasting patterns of impairment and spared abilities on a number of related tasks, we suggest that perirhinal cortex and postrhinal cortex make distinctive contributions to learning and memory: for example, that postrhinal cortex is important in learning about within-scene position and context. We also provide evidence that despite the strong connectivity between these cortical regions and the hippocampus, the hippocampus, as evidenced by lesions of the fornix, has a distinct function of its own-combining information about objects, positions, and contexts.

Anabolic-androgenic steroid treatment induces behavioral disinhibition and downregulation of serotonin receptor messenger RNA in the prefrontal cortex and amygdala of male mice

Nandrolone is an anabolic-androgenic steroid (AAS) that is highly abused by individuals seeking enhanced physical strength or body appearance. Supraphysiological doses of this synthetic testosterone derivative have been associated with many physical and psychiatric adverse effects, particularly episodes of impulsiveness and overt aggressive behavior. As the neural mechanisms underlying AAS-induced behavioral disinhibition are unknown, we investigated the status of serotonergic system-related transcripts in several brain areas of mice receiving prolonged nandrolone administration. Male C57BL/6J mice received 15 mg/kg of nandrolone decanoate subcutaneously once daily for 28 days, and different sets of animals were used to investigate motor-related and emotion-related behaviors or 5-HT-related messenger RNA (mRNA) levels by real-time quantitative polymerase chain reaction. AAS-injected mice had increased body weight, were more active and displayed anxious-like behaviors in novel environments. They exhibited reduced immobility in the forced swim test, a higher probability of being aggressive and more readily attacked opponents. AAS treatment substantially reduced mRNA levels of most investigated postsynaptic 5-HT receptors in the amygdala and prefrontal cortex. Interestingly, the 5-HT(1B) mRNA level was further reduced in the hippocampus and hypothalamus. There was no alteration of 5-HT system transcript levels in the midbrain. In conclusion, high doses of AAS nandrolone in male mice recapitulate the behavioral disinhibition observed in abusers. Furthermore, these high doses downregulate 5-HT receptor mRNA levels in the amygdala and prefrontal cortex. Our combined findings suggest these areas as critical sites for AAS-induced effects and a possible role for the 5-HT(1B) receptor in the observed behavioral disinhibition.

Viability of primordial follicles derived from cryopreserved ovine ovarian cortex tissue

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

Comparison of Botu-bov and Tris as Freezing Extenders of Buffalo Sperm Recovered from Epididymal Cauda

Valuable genetic material can be preserved by the cryopreservation of epididymal sperm. This study evaluated the viability of pre-freezing and post-thawed sperm samples recovered from the epididymal cauda of buffaloes. Epididymides from eight Murrah buffaloes with 18 months of age were used. Semen samples were diluted in two different freezing extenders: Botu-bov (BB) and Tris (TRIS). Immediately after slaughter, both testicles from each animal were collected and transported at 4 degrees C for six hours interval. In laboratory, the removed epididymides were flushed to obtain sperm and the fractions were diluted in both freezing extenders (BB and TRIS). Semen doses were analyzed before and after frozen at -196 degrees C. BB and TRIS pre-freezing results were 38.54 +/- 22.33%(b) and 14.17 +/- 12.78%(a) for total motility (TM), 25.00 +/- 16.12(a) and 9.44 +/- 9.11(a) for progressive motility (PM), 7.21 +/- 0.98(a) and 5.09 +/- 2.65(a) for percentage of rapid cells (RAP), 91.08 +/- 12.53(b) and 63.33 +/- 31.47(a) for velocity of trajectory (VAP), 73.54 +/- 20.17(b) and 49.50 +/- 9.11(a) for linear progressive velocity (VSL), 172.21 +/- 24.55(a) and 116.94 +/- 59.48(a) for curvilinear velocity (VCL), respectively (P < 0.05). BB and TRIS post-thawing results were 42.25 +/- 21.50(b) and 17.62 +/- 19.46(a) for TM, 27.25 +/- 24.86(a) and 18.00 +/- 13.68(a) for PM, 7.35 +/- 0.98(a) and 6.26 +/- 1.13(a) for RAP, 91.42 +/- 16.86(a) and 75.96 +/- 13.17(a) for VAP, 67.96 +/- 12.13(a) and 60.04 +/- 10.42(a) for VSL, 177.54 +/- 23.53(b) and 141.29 +/- 24.97a for VCL, respectively (P < 0.05). The sperm recovered from the epididymal cauda, after 6 h storage of epididymides at 5 degrees C ensures sperm preservation demonstrating that the diluent Botu-bov had higher total motility both pre-and post-freezing when compared with TRIS. Additionally, the sperm frozen with the diluent Botu-bov showed higher values of VSL at post-thawing. These findings may reflect in improvement of conception rates.

Medial prefrontal cortex endocannabinoid system modulates baroreflex activity through CB1 receptors

Ferreira-Junior NC, Fedoce AG, Alves FHF, Correa FMA, Resstel LBM. Medial prefrontal cortex endocannabinoid system modulates baroreflex activity through CB1 receptors. Am J Physiol Regul Integr Comp Physiol 302: R876-R885, 2012. First published December 28, 2011; doi: 10.1152/ajpregu.00330.2011.-Neural reflex mechanisms, such as the baroreflex, are involved in the regulation of cardiovascular system activity. Previous results from our group (Resstel LB, Correa FM. Medial prefrontal cortex NMDA receptors and nitric oxide modulate the parasympathetic component of the baroreflex. Eur J Neurosci 23: 481-488, 2006) have shown that glutamatergic synapses in the ventral portion of the medial prefrontal cortex (vMPFC) modulate baroreflex activity. Moreover, glutamatergic neurotransmission in the vMPFC can be modulated by the endocannabinoids system (eCBs), particularly the endocannabinoid anandamide, through presynaptic CB1 receptor activation. Therefore, in the present study, we investigated eCBs receptors that are present in the vMPFC, and more specifically whether CB1 receptors modulate baroreflex activity. We found that bilateral microinjection of the CB1 receptor antagonist AM251 (100 or 300 pmol/200 nl) into the vMPFC increased baroreflex activity in unanesthetized rats. Moreover, bilateral microinjection of either the anandamide transporter inhibitor AM404 (100 pmol/200 nl) or the inhibitor of the enzyme fatty acid amide hydrolase that degrades anandamide, URB597 (100 pmol/200 nl), into the MPFC decreased baroreflex activity. Finally, pretreatment of the vMPFC with an ineffective dose of AM251 (10 pmol/200 nl) was able to block baroreflex effects of both AM404 and URB597. Taken together, our results support the view that the eCBs in the vMPFC is involved in the modulation of baroreflex activity through the activation of CB1 receptors, which modulate local glutamate release.

Both alpha(1)- and beta(1)-adrenoceptors in the bed nucleus of the stria terminalis are involved in the expression of conditioned contextual fear

BACKGROUND AND PURPOSE The bed nucleus of the stria terminalis (BNST) is a limbic structure that is involved in the expression of conditioned contextual fear. Among the numerous neural inputs to the BNST, noradrenergic synaptic terminals are prominent and some evidence suggests an activation of this noradrenergic neurotransmission in the BNST during aversive situations. Here, we have investigated the involvement of the BNST noradrenergic system in the modulation of behavioural and autonomic responses induced by conditioned contextual fear in rats. EXPERIMENTAL APPROACH Male Wistar rats with cannulae bilaterally implanted into the BNST were submitted to a 10 min conditioning session (6 footshocks, 1.5 ma/ 3 s). Twenty-four hours later freezing and autonomic responses (mean arterial pressure, heart rate and cutaneous temperature) to the conditioning box were measured for 10 min. The adrenoceptor antagonists were administered 10 min before the re-exposure to the aversive context. KEY RESULTS L-propranolol, a non-selective beta-adrenoceptor antagonist, and phentolamine, a non-selective a-adrenoceptor antagonist, reduced both freezing and autonomic responses induced by aversive context. Similar results were observed with CGP20712, a selective beta 1-adrenoceptor antagonist, and WB4101, a selective a1-antagonist, but not with ICI118,551, a selective beta 2-adrenoceptor antagonist or RX821002, a selective a2-antagonist. CONCLUSIONS AND IMPLICATIONS These findings support the idea that noradrenergic neurotransmission in the BNST via a1- and beta 1-adrenoceptors is involved in the expression of conditioned contextual fear.

Imagery of a moving object: the role of occipital cortex and human MT/V5+

Visual imagery – similar to visual perception – activates feature-specific and category-specific visual areas. This is frequently observed in experiments where the instruction is to imagine stimuli that have been shown immediately before the imagery task. Hence, feature-specific activation could be related to the short-term memory retrieval of previously presented sensory information. Here, we investigated mental imagery of stimuli that subjects had not seen before, eliminating the effects of short-term memory. We recorded brain activation using fMRI while subjects performed a behaviourally controlled guided imagery task in predefined retinotopic coordinates to optimize sensitivity in early visual areas. Whole brain analyses revealed activation in a parieto-frontal network and lateral–occipital cortex. Region of interest (ROI) based analyses showed activation in left hMT/V5+. Granger causality mapping taking left hMT/V5+ as source revealed an imagery-specific directed influence from the left inferior parietal lobule (IPL). Interestingly, we observed a negative BOLD response in V1–3 during imagery, modulated by the retinotopic location of the imagined motion trace. Our results indicate that rule-based motion imagery can activate higher-order visual areas involved in motion perception, with a role for top-down directed influences originating in IPL. Lower-order visual areas (V1, V2 and V3) were down-regulated during this type of imagery, possibly reflecting inhibition to avoid visual input from interfering with the imagery construction. This suggests that the activation in early visual areas observed in previous studies might be related to short- or long-term memory retrieval of specific sensory experiences.

Effects of in situ freezing on soil net nitrogen mineralization and net nitrification in fertilized grassland of northern China

Effects of soil freezing on nitrogen (N) mineralization have been the subject of increased attention in the ecological literature, though fewer studies have examined N mineralization responses to successive mild freezing, severe freezing and cyclic freeze–thaw events. Even less is known about relationships of responses to soil N status. This study measured soil N mineralization and nitrification in the field along an experimental N gradient in a grassland of northern China during the dormant season (October 2005–April 2006), a period in which freezing naturally occurs. Net N mineralization exhibited great temporal variability, with nitrification being the predominant N transformation process. Soil microbial biomass C and N and extractable NH4 + pools declined by 40, 52, and 56%, respectively, in April 2006, compared with their initial concentrations in October 2005; soil NO3– pools increased by 84%. Temporal patterns of N mineralization were correlated with soil microbial biomass C and N. N mineralization and nitrification increased linearly with added N. Microbial biomass C in treated soils increased by 10% relative to controls, whereas microbial N declined by 9%. Results further suggest that freezing events greatly alter soil N dynamics in the dormant season at this site, with considerable available N accumulating during this period.

Formation of mnemonic neuronal responses to visual paired associates in inferotemporal cortex is impaired by perirhinal and entorhinal lesions.

Functional roles of the cortical backward signal in long-term memory formation were studied in monkeys performing a visual pair-association task. Before the monkeys learned the task, the anterior commissure was transected, disconnecting the anterior temporal cortex of each hemisphere. After training with 12 pairs of pictures, single units were recorded from the inferotemporal cortex of the monkeys as the control. By injecting a grid of ibotenic acid, we unilaterally lesioned the entorhinal and perirhinal cortex, which provides massive direct and indirect backward projections ipsilaterally to the inferotemporal cortex. After the lesion, the monkeys fixated the cue stimulus normally, relearned the preoperatively learned set (set A), and learned a new set (set B) of paired associates. Then, single units were recorded from the same area as for the prelesion control. We found that (i) in spite of the lesion, the sampled neurons responded strongly and selectively to both the set A and set B patterns and (ii) the paired associates elicited significantly correlated responses in the control neurons before the lesion but not in the cells tested after the lesion, either for set A or set B stimuli. We conclude that the ability of inferotemporal neurons to represent association between picture pairs was lost after the lesion of entorhinal and perirhinal cortex, most likely through disruption of backward neural signals to the inferotemporal neurons, while the ability of the neurons to respond to a particular visual stimulus was left intact.