Propionic acid affects the synaptic architecture of rat hippocampus and prefrontal cortex

It is well documented that propionic acid (PPA) produces behavioral, morphological, molecular and immune responses in rats that are characteristic of autism spectrum disorder in humans. However, whether PPA affects the ultrastructure and synaptic architecture of regions of autistic brain has not been adequately addressed. Earlier we show that single intraperitoneal (IP) injection of PPA (175 mg/kg) produces superficial changes in the spatial memory and learning of adolescent male Wistar rats. However, in neurons, synapses and glial cells of hippocampal CA1 area and medial prefrontal cortex transient (mainly) or enduring alterations were detected. In this study, we used electron microscopic morphometric analysis to test the effect of PPA on different structural parameters of axodendritic synapses of the hippocampus and prefrontal cortex. The animals were treated with a single IP injection of PPA (175 mg/kg). The length and width of synaptic active zone, the area of presynaptic and postsynaptic mitochondria, the distance between presynaptic mitochondria and the synapse active zone, the distance between postsynaptic mitochondria and postsynaptic density and the depth and opening diameter of neuronal porosome complex were evaluated. Our results show that synaptic mitochondria of the hippocampus and prefrontal cortex are the most vulnerable to PPA treatment: in both regions, the area of postsynaptic mitochondria were increased. In general, our results show that even small dose of PPA, which produces only superficial effects on spatial memory and learning is able to alter the synapse architecture in brain regions involved in cognition and autism pathogenesis. Therefore, the microbiome may be involved in the control of neurotransmission in these regions.

Differential effects of aging on hippocampal ultrastructure in male vs. female rats

Age-related decline in physical and cognitive functions are facts of life that do not affect everyone to the same extent. We had reported earlier that such cognitive decline is both sex- and context-dependent. Moreover, age-associated ultrastructural changes were observed in the hippocampus of male rats. In this study, we sought to determine potential differences in ultrastructural changes between male and female rats at various stages of life. We performed quantitative electron microscopic evaluation of hippocampal CA1 region, an area intimately involved in cognitive behavior, in both male and female adolescent, adult and old Wistar rats. Specifically, we measured the number of docking synaptic vesicles in axo-dendritic synapses, the length of active zone as well as the total number of synaptic vesicles. Distinct age- and sex-dependent effects were observed in several parameters. Thus, adult female rats had the lowest synaptic active zone compared to both adolescent and old female rats. Moreover, the same parameter was significantly lower in adult and old female rats compared to their male counterparts. On the other hand, old male rats had significantly lower number of total synaptic vesicles compared to both adolescent and adult male rats as well as compared to their female counterparts. Taken together, it may be suggested that age- and sex-dependent ultrastructural changes in the hippocampus may underlie at least some of the differences in cognitive functions among these groups.

Short- and long-term effects of chronic toluene exposure on recognition memory in adolescent and adult male Wistar rats

Abuse of toluene-containing volatile inhalants, particularly among youth, is of significant medical and social concern worldwide. Teenagers constitute the most abundant users of toluene and the majority of adult abusers of toluene started as teenagers. Although the euphoric and neurotoxic effects of acute toluene have been widely studied, lasting effects of chronic toluene exposure, especially in various age groups, have not been well investigated. In this study, we used adolescent and adult male Wistar rats to evaluate the short- and long-term effects of chronic toluene on various behaviors including cognitive function. Daily exposure to toluene (2000 ppm) for 40 days (5min/day) resulted in age-dependent behavioral impairments. Specifically, adolescent animals showed recognition memory impairment the day after the last exposure, which had normalized by day 90 post- exposure, whereas such impairment in adult animals was still evident at day 90 post-exposure. Our data suggest that age-dependent responses should be taken into consideration in interventional attempts to overcome specific detrimental consequences of chronic toluene exposure.

Anxiety and ultrastructural consequences of chronic mild stress in rats

Detrimental consequences following exposure to severe stress, either acute or chronic are well recognized. Chronic mild stress (CMS) is also a leading cause of emotional distress and neuropsychiatric conditions such as anxiety disorders. However, the neurobiological substrates of the latter, particularly at the ultrastructural levels have not been adequately investigated. In this study, adult male Wistar rats were subjected to 4 h daily mild restraint for 20 days and their behavior in open field and elevated plus maze (EPM) were evaluated 24 h after the last restraint. Anxiety-like behavior was evident in CMS exposed rats by increases in rearing and grooming in the open field and the avoidance of open arms in the EPM. Concomitant ultrastructural alterations such as chromatolysis, agglutination of synaptic vesicles or mitochondrial damage were also observed in the central nucleus of amygdala (CNA), an area intimately involved in emotional and fear response, in CMS exposed rats. These results while confirming detrimental consequences of CMS, also suggest that ultrastructural alterations in CNA may be a basis for CMS-induced anxiety.

Age-related cognitive decline in rats is sex and context dependent

Previously, we had observed age-related cognitive decline in male rats compared to adolescent and adult rats. This was shown in both a multi-branched maze test (MBM), as well as in the Morris water maze test (MWM). In the present study, we compared the behavior of similar age groups in both male and female rats using the same paradigms. The results confirmed the increase in errors and time spent in MBM in aged male rats compared to other age groups. However, no such differences were observed in female rats. In the acquisition phase of MWM, aged male rats did not differ significantly from the other two groups in terms of time spent in quadrants, whereas aged female rats spent significantly more time in quadrants compared to the other 2 age groups. Aged male rats also travelled significantly more than the other 2 age groups during the acquisition phase, whereas no such differences were observed in female rats. In both short term (30 min post acquisition) and long term (24 h after acquisition) retrieval phases of MWM, significant gender-related differences were also observed in all age groups. These findings suggest gender- and context-dependent alterations in cognitive functions during aging.

THE EFFECT OF HIGH INTENSITY WHITE NOISE ON THE ULTRASTRUCTURE OF AXO-DENDRITIC SYNAPSES IN COLLICULUS INFERIOR OF ADULT MALE CATS. QUANTITATIVE ELECTRON MICROSCOPIC STUDY

Environmental noise is a serious problem for the society and medicine. Chronic loud noise is known to produce numerous adverse effects on different levels of the organism. In addition to behavioral changes, the involvement of different regions of the brain was documented. The analysis of structural modifications provoked by noise in brain give the possibility to suggest that one of the effects of noise may be the alterations in neurotransmission. Therefore, of special interest should be the elucidation of the effects of chronic noise on the fine structure of synapses of brain areas participating in the processing of auditory information. In the present study, using transmission electron microscope. We elucidate the effects of high intensity chronic white noise on the morphology of axo-dendritic synapses, and size and diameter of synaptic vesicles in auditory region, inferior colliculus of adult male cats. Experimental animals were exposed to 100 dB (5-20 kHz) white noise for one hour per day, for 10 consecutive days. On 11th day, after special procedures, the area of interest was examined under electron microscope. In ~ 15% large synaptic terminals the clustering of synaptic vesicles, as well as swelling, partial vacuolization or degeneration of presynaptic mitochondria were detected. Morphometric analysis of docked (with presynaptic membrane) and undocked synaptic vesicle size revealed that docked vesicles are smaller than undocked vesicles. It was observed in both control and experimental animals, however, in experimental animals, such difference was more significant. Such results suggest that due to continuous transmission, the majority of vesicles are unable to replenish their cargo via transporters. Evaluation of synaptic vesicles size undertaken in the current electron microscopic study has advanced the understanding of the pathophysiology of white noise exposure on auditory brain processing regions, in addition to our understanding of fractional neurotransmitter release at the nerve terminal and on overall brain function.

FINE ARCHITECTURE OF THE HIPPOCAMPUS IN ADOLESCENT, ADULT AND AGED RATS. ELECTRON MICROSCOPIC STUDY

The study included adolescents (P30-36), adult (P125-130) and aged (P330-340) male Wistar rats - 4 animals in each age group. The rats were housed individually, in wire-top polypropylene cages (30-cm width x 30 cm length x 25 cm height) and maintained on a 12-h light/dark cycle. Standard food pellets and tap water were ad libitum. The animal maintenance and electron microscopic procedures were conducted in accordance with European Union Directive on the protection of animals used for scientific research. The Ultrastructure of adult and adolescent rats are almost same. However, remarkable changes are expressed between adult and senescent rats. Precisely, in the last one there are following ultrastructural modifications - lipofuscin concentrations, small destructive cytoplasmic organelles, changes in presynaptic vesicular and mitochondrial quantity. Rare apoptotic signs in neurons. Analysis of all this means that aging in rat's hippocampus causes selective changes, also it underlines changes in neurotransmission and neuronal developmental pathways.

Aging affects cognition and hippocampal ultrastructure in male Wistar rats

It is now well established that aging is associated with emotional and cognitive changes. Although the basis of such changes is not fully understood, ultrastructural alterations in key brain areas are likely contributing factors. Recently, we reported that aging-related anxiety in male Wistar rats is associated with ultrastructural changes in the central nucleus of amygdala, an area that plays important role in emotional regulation. In this study, we evaluated the cognitive performance of adolescent, adult, and aged male Wistar rats in multi-branch maze (MBM) as well as in Morris water maze (MWM). We also performed ultrastructural analysis of the CA1 region of the hippocampus, an area intimately involved in cognitive function. The behavioral data indicate significant impairments in few indices of cognitive functions in both tests in aged rats compared to the other two age groups. Concomitantly, a total number of presynaptic vesicles as well as vesicles in the resting pool were significantly lower, whereas postsynaptic mitochondrial area was significantly higher in aged rats compared to the other age groups. No significant differences in presynaptic terminal area or postsynaptic mitochondrial number were detected between the three age groups. These results indicate that selective ultrastructural changes in specific hippocampal region may accompany cognitive decline in aging rats.

Gender differences in anxiety response to high intensity white noise in rats

Prolong exposure to high intensity white noise (HIWN), defined as a heterogeneous mixture of sound waves extending over a wide frequency range, has detrimental peripheral and central consequences including cardiovascular and emotional effects. Anxiety is a common manifestation of HIWN. Although gender-dependent differences in manifestation of anxiety and/or response to treatment of this condition has been amply documented, potential differences in response to HIWN, a common exposure in combat, construction and rave disco, has not been adequately investigated. In this study, both male and female Wistar rats were subjected to HIWN for 10 consecutive days, 1 h/day. On day 11, a day after the last exposure, the performance of the rats in open field (OF) and elevated plus maze (EPM) was evaluated. Male rats showed a higher anxiety-like response to HIWN as evidenced by: lower number of entries into the open arm of the EPM, lower number of entries into central zone of OF, excess grooming in OF and more boluses in closed arm of EPM. These results indicate that gender-related differences in anxiety in general, and in response to HIWN, in particular, has to be taken into consideration when investigating the neurobiological components and/or treatment modalities.

Behavioural and brain ultrastructural changes following the systemic administration of propionic acid in adolescent male rats. Further development of a rodent model of autism

Short chain fatty acids, produced as gut microbiome metabolites but also present in the diet, exert broad effects in host physiology. Propionic acid (PPA), along with butyrate and acetate, plays a growing role in health, but also in neurological conditions. Increased PPA exposure in humans, animal models and cell lines elicit diverse behavioural and biochemical changes consistent with organic acidurias, mitochondrial disorders and autism spectrum disorders (ASD). ASD is considered a disorder of synaptic dysfunction and cell signalling, but also neuroinflammatory and neurometabolic components. We examined behaviour (Morris water and radial arm mazes) and the ultrastructure of the hippocampus and medial prefrontal cortex (electron microscopy) following a single intraperitoneal (i.p.) injection of PPA (175 mg/kg) in male adolescent rats. PPA treatment showed altered social and locomotor behaviour without changes in learning and memory. Both transient and enduring ultrastructural alterations in synapses, astro- and microglia were detected in the CA1 hippocampal area. Electron microscopic analysis showed the PPA treatment significantly decreased the total number of synaptic vesicles, presynaptic mitochondria and synapses with a symmetric active zone. Thus, brief systemic administration of this dietary and enteric short chain fatty acid produced behavioural and dynamic brain ultrastructural changes, providing further validation of the PPA model of ASD.

The monthly variations in mortality from the cardiovascular diseases in Tbilisi

Results of the detailed statistical analysis of the monthly average decade mortality on the reasons for cardiovascular diseases in Tbilisi into 1980-1992 and 2012-2013 are represented. Variable +background and random component of time-series of mortality are determined. A share of the mean values of the component of variable +background from the mean value of real data of mortality constitute 68,4 % in 1980-1992 and 73,4 % in 2012-2013. Variations of the random component and their contribution to the real values of mortality (31,6 % in 1980-1992 and 26,6 % in 2012-2013) besides the air temperature can depend on many others meteorological, geophysical, social and so forth of factors. The scale of the six levels of cardiovascular mortality is proposed. In different months of year the indicated levels of mortality are various.

Validating the effect of muscle artifact suppression in localizing focal epilepsy

Source localization of an epileptic seizure is becoming an important diagnostic tool in pre-surgical evaluation of epileptic patients. However, for localizing the epileptogenic zone precisely, the epileptic activity needs to be isolated from other activities that are not related to the epileptic source. In this study, we aim at an investigation of the effect of muscle artifact suppression by using a low-pass filter (LPF), independent component analysis (ICA), and a combination of ICA-LPF prior to source localization in focal epilepsy. These techniques were applied on the EEG data obtained from a left-temporal lobe epileptic patient by artificially contaminating the isolated spike interval, present in the four left-temporal electrodes, with a muscle artifact. The results show that the muscle artifact was fully suppressed. Applying the dipole and current-density reconstruction (CDR) source-analysis algorithms on the filtered data, we were able to identify the location of the epileptogenic zone similar to that of the original undistorted data.

Effect of nadolol injected prior to CRH on stress-induced plasma corticosterone level in rat

The proposed research is the part of our investigation of the role of catecholamines in the alterations provoked by stress. Especially, we elucidate if Nadolol injected prior to CRH ICV has some effect on plasma corticosterone level. 15 mg/kg of Nadolol (the dose sufficient to prevent CRH-induced increases in heart-rate for 2 hr), dissolved in saline was administered intraperitoneally, 30 minutes prior to CRH (The dose of interest for CRH - 1 mkg/kg - was determined earlier, as provoking the maximal increase of plasma corticosterone level after 20 minutes of its ICV injection). Whole blood was collected at 11.00 am, via indwelling jugular catheter at 0 (control) and 15 minutes after Nadolol injection, also 30 and 60 min after CRH injection. After centrifugation the plasma level of corticosterone was essayed using ELISA method. 15 minutes after Nadolol injection the level of plasma corticosterone in comparing with control wasn't changed, at subsequent time-points plasma corticosterone level was increased but significant difference was observed only after 30 minutes. Thus, according our results, 30 min after injection, the dose of Nadolol, sufficient to prevent CRH-induced increase in heart rate, doesn't preclude the CRH-induced increase of plasma corticosterone - one of key signs of the stress-axis activation. The results were discussed.

Stress-system: corticotropin-releasing hormone and catecholamines (review)

The brain's stress-handling system--the limbic-hypothalamic-pituitary-adrenal axis--is one of the most thoroughly studied circuitry of the central nervous system. As a result of stress-axis activation different behavioral and physical changes develop; these changes allow the organism to adapt. For this purpose stress-system closely "works" with other elements of central nervous system, which are involved in the regulation of emotion and structures, also with axes, responsible for reproduction, growth and immunity. Dysfunction of stress-system--it's hyper- or hypoactivity--is characteristic peculiarity of many pathological states and disorders. Various molecules (corticotropin-releasing hormone, vasopressin, glucocorticoids, mineralocorticoids, ACTH, its precursor proopiomelanocortin etc.) are engaged in the regulation of stress-axis. Among these molecules corticotropin-releasing hormone is supposed to have a key role in regulating the response to stress. Besides these molecules, the end-products of the stress-axis activation: catecholamines, different hormones and cytokines - control the activity of multiple levels of this axis. According some views catecholamines play one of the essential roles in the alterations provoked by stress-axis activation. In this review we cite some classical (Crousseau et al.) and modern data concerning corticotropin-releasing hormone and catecholamine activities during stress.

Pyramidal cell loss in hippocampus of young rats exposed to toluene

In the present study the influences of toluene intoxication on quantity of the pyramidal and granular cells in hippocampus was analysed in young and adult rats. An inhalation route of intoxication was used in our experiments - animal inhaled toluene until attaining a sidewise laying position. This procedure was performed in the closed glass container, in which air was beforehand saturated with the toluene vapors. Experiments was carried out on two age groups (n=20): one and two months age rats. Inhalation period was 40 days, Each age group consisted of ten animals and was divided into the two subgroups: I - control animals (n=5), II - experimental animals (n=5). Assessment of the neurons' quantity in different structures was made according to the fractional approach method proposed by M. West. The results obtained showed that number of the pyramidal neurons decreases by 26% (I - 1067+/-83,8; II - 786+/-7; p<0,05) against the control in CA-3 field of the Subgroup II of the younger animals only. In the dentate fascia number of the granular cells does not change in either age group. Loss of pyramidal cells in the CA-3 field will induce deterioration of the hippocampal neural circuits and destroy of memory and learning processes in the rats.

Influence of toluene intoxication on the number of mitral and granular neurons in olfactory bulbs of rats

In the last years, implementation of the volatile solvents in order to get a narcotic high, used via inhalation (sniffing), increased significantly, especially in the youth. Substances containing these agents induce hallucinations and euphoric state. In the present study the influences of toluene intoxication on quantity of the mitral and granular cells in olfactory bulbs was analyzed in young and adult rats. An inhalation route of intoxication was used in our experiments - animal inhaled toluene until attaining a sidewise laying position. This procedure was performed in the closed glass container, in which air was beforehand saturated with the toluene vapours. Experiments was carried out on two age groups (n=20 animals): one - and two months age rats. Inhalation period was 40 days. Each age group consisted of ten animals and was divided into the two subgroups: I - control animals (n=5), II - experimental animals (n=5). Assessment of the neurons' quantity in different structures was made according to the fractional approach method proposed by M. West (1999). The results obtained showed that number of mitral neurons in the olfactory bulb of the Subgroup II of the rats, sniffing since the age of one and two months, significantly decreased by 43% (p<0,05) and by 28% (p<0,01), respectively. Meanwhile, the granular cells remained unaltered in experimental animals of both age groups. Decrease of the projection mitral neurons, in its turn, results in disruption of the projections to olfactory cortex and hampers proper functioning of the olfactory analyzer.