Alterations in synaptosomal neurotransmitter amino acids in “petit-mal” rats at a daytime and a nighttime

The synaptosoma fractions of 6 brain areas-olfactory tubercles (OT), frontal cortex (FC), striatum (Sr), amygdala (A), thalamus (Th), hypothalamus (Hy)-have been analyzed for their neurotransmitter amino acids (AA) content in Wistar rats exhibiting petit-mal epilepsy (PM-E) and in controls (C). The analysis was carried out at 11 p.m. (nighttime corresponding to the acrophase for the hourly number of spike-wave complexes) and at 11 a.m. (daytime). A day versus night rhythmicity is recorded for synaptosomal inhibitory AA in control and in PM-E rats. However, day versus night variations are more frequent and more prominent in C rats than in PM-E rats. Two day versus night variations exist only in PM-E rats: increases of GABA level in Sr and of Asp in Hy. Differences between PME-and C in synaptosomal AA content are more likely to be present during the nighttime. During this period lower AA values for PM-E rats are found for one or several inhibitory AA in OT, Th, and FC. It seems that the differences between PM-E and C concerning the inhibitory AA correlate with the number of spike-wave discharges. Only in one brain area is there a similar difference for PM-E and C during daytime and nighttime: a decreased GABA content for PM-E rats in OT. The decrease is larger in nighttime than in daytime. This difference may serve as a marker for this epileptic disorder. Moreover, it is in OT that the greatest number of PM-E versus C differences in synaptosomal neurotransmitter AA are observed. In view of these and former data, the existence of different alterations in synaptosomal neurotransmitter AA for different types of epilepsy is suggested.Abbreviations used GABA 4-aminobutyrate - Tau taurine - Gly glycine - Asp aspartate - Glu glutamate - Gln glutamine - OT offactory tubereles - FC fronto-parietal cortex - Sr striatum - A amygdala - Th lateral thalamus - Hy lateral hypothalamus - AA neurotransmitter amino acids - I inhibitory - E excitatory - C control rats - PM-E petit-mal rats     

Repeated neonatal separation stress alters the composition of neurochemically characterized interneuron subpopulations in the rodent dentate gyrus and basolateral amygdala

Emotional experience during early life has been shown to interfere with the development of excitatory synaptic networks in the prefrontal cortex, hippocampus, and the amygdala of rodents and primates. The aim of the present study was to investigate a developmental "homoeostatic synaptic plasticity" hypothesis and to test whether stress-induced changes of excitatory synaptic composition are counterbalanced by parallel changes of inhibitory synaptic networks. The impact of repeated early separation stress on the development of two GABAergic neuronal subpopulations was quantitatively analyzed in the brain of the semiprecocial rodent Octodon degus. Assuming that PARV- and CaBP-D28k-expression are negatively correlated to the level of inhibitory activity, the previously described reduced density of excitatory spine synapses in the dentate gyrus of stressed animals appears to be "amplified" by elevated GABAergic inhibition, reflected by reduced PARV- (down to 85%) and CaBP-D28k-immunoreactivity (down to 74%). In opposite direction, the previously observed elevated excitatory spine density in the CA1 region of stressed animals appears to be amplified by reduced inhibition, reflected by elevated CaPB-D28k-immunoreactivity (up to 149%). In the (baso)lateral amygdala, the previously described reduction of excitatory spine synapses appears to be "compensated" by reduced inhibitory activity, reflected by dramatically elevated PARV- (up to 395%) and CaPB-D28k-immunoreactivity (up to 327%). No significant differences were found in the central nucleus of the amygdala, the piriform, and somatosensory cortices and in the hypothalamic paraventricular nucleus. Thus during stress-evoked neuronal and synaptic reorganization, a homeostatic balance between excitation and inhibition is not maintained in all regions of the juvenile brain.     

Long-lasting effects of audiogenic seizures on neurotransmitter amino acids in Rb mice

The existence of long-lasting (15–18 h) alterations of neurotrasmitter amino acid levels following a single or repeated acoustic stimulations in audiogenic seizure-prone Rb1 and Rb2 mice and suizure-resistant Rb3 mice were investigated. The levels of glutamate, aspartate, glycine, taurine, and of some of their precursors: glutamine and serine were determined. Fourteen brain areas were examined. Alterations were found only in 6 brain areas (pons, olfactory bulbs, superior colliculus, inferior colliculus, olfactory tubercles and raphe). Most frequent occuring changes were observed in pons and olfactory tubercles. These changes concerned mainly the excitatory amino acids, glutamate, and aspartate. Alterations of taurine, glycine and serine were also recorded.Abbreviations GABA 4-aminobutyrate - Tau taurine - Gly glycine - Asp aspertate - Glu glutamate - Gln glutamine - Ser serine - OB olfactory bulbs - OT olfactory tubercles - Sr striatum - Se septum - Hy hypothalamus - Th thalamus - Hi hippocampus - A amygdala - SC superior colliculus - IC inferior colliculus - FC frontal cortex - C cerebellum - P pons medulla - Ra raphe - AA neurotransmitter amino acids - I inhibitory - E excitatory - SSL steady-state level Plesant memories of Lawrence Austin's sojourn in my group at Strasbourg gather upon me when I dedicate this article on this occasion for the contribution that Lawrence Austin has made for the cause of neurochemical researchers.     

Viability of spores after repeate freezing and thawing shocks

Survival of spores of the fungus Rhizopus nigricans after repeated freezing and thawing was investigated. The cooling rate was 10(4) degrees C/min. Dry spores were fully inactive after 32 repeated shocks. About one-half of spores were killed after 8 repetitions. The water content did not change the resistance, swollen spores reacted to shocks much like dry ones. The sensitivity of spores to freezing-thawing shocks increased considerably when the spores changed from the dormant to the active state. Already after a 30 min cultivation of spores in the nutrient medium two freezing and thawings were sufficient for inactivation of 60% spores. After a 90 min cultivation one freezing and one thawing were sufficient to inactivate practically all spores.     

Brain ascorbic acid and block of the catecholamine synthesis induced by alpha-methyl-tyrosine

In brain medial-basal areas (midbrain, hypothalamus, striatum) ascorbic acid (AA) content is lower than in the rest of the brain. It has been hypothesized that AA may be involved in brain catecholamine metabolism. To test this hypothesis AA content in medial-basal areas and in the remaining brain areas was measured in rats pretreated with alpha-methyl-paratyrosine (alpha-MpT), a tyrosine hydroxylase inhibitor. The AA content, in brain medial-basal areas, had slightly decreased, without statistically significant differences, in rats treated with alpha-MpT in comparison with untreated animals. Therefore the role of AA in brain metabolism is not clear to.     

Stability and structural constraints of random brain networks with excitatory and inhibitory neural populations

The stability of brain networks with randomly connected excitatory and inhibitory neural populations is investigated using a simplified physiological model of brain electrical activity. Neural populations are randomly assigned to be excitatory or inhibitory and the stability of a brain network is determined by the spectrum of the network’s matrix of connection strengths. The probability that a network is stable is determined from its spectral density which is numerically determined and is approximated by a spectral distribution recently derived by Rajan and Abbott. The probability that a brain network is stable is maximum when the total connection strength into a population is approximately zero and is shown to depend on the arrangement of the excitatory and inhibitory connections and the parameters of the network. The maximum excitatory and inhibitory input into a structure allowed by stability occurs when the net input equals zero and, in contrast to networks with randomly distributed excitatory and inhibitory connections, substantially increases as the number of connections increases. Networks with the largest excitatory and inhibitory input allowed by stability have multiple marginally stable modes, are highly responsive and adaptable to external stimuli, have the same total input into each structure with minimal variance in the excitatory and inhibitory connection strengths, and have a wide range of flexible, adaptable, and complex behavior.     

Primary afferent fibers conduct impulses in both directions under physiological stimulus conditions

Summary In electric fish of the family Mormyridae some primary afferent fibers conduct impulses not only from electroreceptors to the brain but also from the brain to the receptors. The efferent impulses may be elicited by electrical stimulation which is within the physiological range, i.e., by stimulation which is similar in amplitude and duration to the stimulation that is caused by the fish's own electric organ discharge. Afferent and efferent impulses in the same afferent fiber were identified by: simultaneously recording from a fiber at two different points, at the receptor and at the nerve trunk (Figs. 2C-H; 3B-D); by cutting the afferent fiber between the brain and the recording site as well as between the recording site and the periphery; and by intra-axonal recording from the afferent fiber near its entry into the brain (Fig. 4). The efferent impulses result from the central integration of a corollary discharge of the electric organ motor command with excitatory and inhibitory input from several different receptors near the one from which afferent impulses originate (Fig. 4). The centrally originating impulse may be capable of modifying the effect of signals originating in the periphery.Abbreviations ELLL electrosensory lateral line lobe - EOCD electric organ corollary discharge - EOD electric organ discharge - epsp excitatory postsynaptic potential - NPLL posterior lateral line nerve     

Influence of glutamate and GABA transport on brain excitatory/inhibitory balance

An optimally functional brain requires both excitatory and inhibitory inputs that are regulated and balanced. A perturbation in the excitatory/inhibitory balance—as is the case in some neurological disorders/diseases (e.g. traumatic brain injury Alzheimer’s disease, stroke, epilepsy and substance abuse) and disorders of development (e.g. schizophrenia, Rhett syndrome and autism spectrum disorder)—leads to dysfunctional signaling, which can result in impaired cognitive and motor function, if not frank neuronal injury. At the cellular level, transmission of glutamate and GABA, the principle excitatory and inhibitory neurotransmitters in the central nervous system control excitatory/inhibitory balance. Herein, we review the synthesis, release, and signaling of GABA and glutamate followed by a focused discussion on the importance of their transport systems to the maintenance of excitatory/inhibitory balance.     

猫中·间脑结合部神经元与眼球下斜肌运动神经元的直接突触联系

本文应用神经元自发放电触发的迭加平均法,研究了猫中·间脑结合部内侧区神经元与眼球下斜肌运动神经元（inferiorobliquemotoneurons,IOMNs）之间的突触联系。电刺激同侧或对侧中·间脑结合部的Forel'sfieldeH（FFH）的内侧区（A7～Ag）,在IOMN池内记录到兴奋性单突触电场电位。应用FFH神经元的自发放电作为触发信号,将此放电引起的IOMNs的电位变化进行迭加平均,结果亦获得一兴奋性单突触电场电位。这些结果表明,中·间脑结合部内侧区神经元与IOMNs之间存在兴奋性单突触联系,其作用为启动眼球的垂直运动。     

Differential effects of inescapable footshocks and of stimuli previously paired with inescapable footshocks on dopamine turnover in cortical and limbic areas of the rat

The effect of electric footshocks and of exposure to environmental stimuli paired with electrical shocks upon the dopaminergic activity in various cortical and limbic areas of the rat were evaluated by measuring dihydroxyphenylacetic acid (DOPAC) levels in these areas. In animals exposed to a 20 min electric footshock session DOPAC concentrations were significantly increased in the antero-medial and sulcal frontal cortices, olfactory tubercle, nucleus accumbens and amygdaloid complex (by 66, 37, 28, 55 and 90% respectively). Re-exposure of rats to an environment where they had been shocked 24 h earlier induced an elevation of DOPAC content only in the anteromedial frontal cortex (by 47%). Plasma corticosterone levels were elevated in both situations. No change in serotonin or 5-hydroxyindolacetic acid content of these areas could be detected in either situation. The results show that electric footshocks and environmental stimuli associated to previous shocks both activate central dopaminergic systems, although the patterns of activation are different.     

Chronic administration of ethyl docosahexaenoate decreases mortality and cerebral edema in ischemic gerbils

Dietary docosahexaenoic acid (DHA) intake can decrease the level of membrane arachidonic acid (AA), which is liberated during cerebral ischemia and implicated in the pathogenesis of brain damage. Therefore, in the present study, we investigated the effects of chronic ethyl docosahexaenoate (E-DHA) administration on mortality and cerebral edema induced by transient forebrain ischemia in gerbils. Male Mongolian gerbils were orally pretreated with either E-DHA (100, 150 mg/kg) or vehicle, once a day, for 4 weeks and were subjected to transient forebrain ischemia by bilateral common carotid occlusion for 30 min. The content of brain lipid AA at the termination of treatment, the survival ratio, change of regional cerebral blood flow (rCBF), brain free AA level, thromboxane B(2) (TXB(2)) production and cerebral edema formation following ischemia and reperfusion were evaluated. E-DHA (150 mg/kg) pretreatment significantly increased survival ratio, prevented post-ischemic hypoperfusion and attenuated cerebral edema after reperfusion compared with vehicle, which was well associated with the reduced levels of AA and TXB(2) in the E-DHA treated brain. These data suggest that the effects of E-DHA pretreatment on ischemic mortality and cerebral edema could be due to reduction of free AA liberation and accumulation, and its metabolite synthesis after ischemia and reperfusion by decreasing the content of membrane AA.     

尿嘧啶对单胺氧化酶的抑制作用

给青年小鼠(1月龄)po尿嘧啶25—800mg/kg对脑和肝MAO-B活性抑制作用与剂量成明显量-效关系,而对MAO-A抑制较弱。多次po尿嘧啶300mg/kg对老年小鼠(18月龄)脑MAO活性抑制作用明显强于对青年小鼠,并能增加老年小鼠脑组织5-HT和DA含量。另外,随年龄增加,小鼠血、脑和肝组织MAO活性显著升高,而上述组织中尿嘧啶含量则明显降低。体外实经证明,尿嘧啶对MAO-B活性抑制程度明显强子对MAO-A,并且对MAO-B为竞争性抑制,对MAO-A为混合型抑制。     

Is "scopolamine-induced amnesia" in rats the result of state-dependent learning?

The effects of a single and repetitive administration of m-cholinoblocker scopolamine (Sc) to male rats on retention of step-through passive avoidance (PA) or active avoidance (AA) in a shuttle-box were compared. In case of PA Sc (1 mg/kg) was injected i.p. only 30 min before training, only 30 min before testing, or both before training and before testing. In case of AA Sc (0.5 mg/kg/day) was injected i.p. only 15 min before each training session or both before training and before testing (44 days after achievement of learning criterion). The PA and AA retention were impaired only in the experiments, where the drug was administered before training, but did not differ from control, when Sc was injected twice. The Sc-induced amnesia (like many other cases of memory deficits) is suggested to be a manifestation of state-dependent learning. Similarity between the brain state during memory consolidation and during the retention test is necessary for recollection.     

Brain IL-6 elevation causes neuronal circuitry imbalances and mediates autism-like behaviors

Abnormal immune responses have been reported to be associated with autism. A number of studies showed that cytokines were increased in the blood, brain, and cerebrospinal fluid of autistic subjects. Elevated IL-6 in autistic brain has been a consistent finding. However, the mechanisms by which IL-6 may be involved in the pathogenesis of autism are not well understood. Here we show that mice with elevated IL-6 in the brain display many autistic features, including impaired cognitive abilities, deficits in learning, abnormal anxiety traits and habituations, as well as decreased social interactions. IL-6 elevation caused alterations in excitatory and inhibitory synaptic formations and disrupted the balance of excitatory/inhibitory synaptic transmissions. IL-6 elevation also resulted in an abnormal change in the shape, length and distributing pattern of dendritic spines. These findings suggest that IL-6 elevation in the brain could mediate autistic-like behaviors, possibly through the imbalances of neural circuitry and impairments of synaptic plasticity.     

Effect of phospholipids containing omega-3 fatty acids on structural changes of microsomal lipids in cell membranes of functionally different cells

As a result of the experimental researches conducted it has been shown that administration of some normal animal marine phospholipids (PL) including in their structure omega-3 polyunsaturated fatty acids (PUFA) provides for quantitative changes of individual PL, fatty acids (FA) content and quantity in general and individual PL of liver, heart, brain and gonads microsomes. While estimating general microsomal PL fraction FA content under the action of PL omega-3 PUFA FA concentration change, unsaturation index (omega 6/omega 3) and relation of arachidonic acid to docosahexenic (AA/DHA) decrease have been identified. The decrease of AA/DHA relationship occurs due to AA and DHA quantitative changes. In the case of AA increase in some tissues there is observed the decrease of docosapentaenic acid and increase of DHA and eucosapentaenic (EPA) acidds. As a result of studying FA content in the individual PL composition it has been identified that certain PL classes characteristic for some tissues respond by changes of some certain FA. The relationship omega 6/omega 3 has been shown as decreasing in phosphatidilcholine (PC) all tissues microsomes (liver, gonads, heart, brain), in phosphatidilethanolamine (PEA) of liver and cardiac microsomes, in phosphatidilserine (PS) this relationship relationship decreases in the liver, brain and heart, for phosphatidilinositole (PI) the changes take place in liver, gonads, brain. Simultaneously, the decrease of AA/DHA relationship in the individual PL decrease of AA and increase of EPA and DHA depend on the tested tissues. The marine phospholipids might be supposed to render their effect on AA metabolism resulting in AA/DHA relationship in PEA and PS relationship displays itself as specific and depends on the tissues functions. The preference of PEA and PS use by certain tissues microsomes could be explained by their membrane protective capability.     

A role for chromogranin A (4-16), a vasostatin-derived peptide, on human colonic motility. An in vitro study

The hypothesis that CgA-derived peptides may be involved in mechanisms modulating motility was tested. Human colonic smooth muscles were studied using an organ bath technique. Acetic acid (AA) effects were characterized on spontaneous mechanical activities (SMA) and on responses to transmural nerve stimulation (NS). AA induced a significant decrease in tone and abolished SMA; this effect was insensitive to either TTX or L-NAME/apamin. The AA-induced inhibitory effects were significantly reduced in the presence of CgA4-16. This effect was insensitive to TTX or L-NAME/apamin. Furthermore, AA-induced effects were blocked in the presence of BAYK8644 and CgA4-16 together. The inhibitory effect of nifedipine was delayed in the presence of CgA4-16. NS induced a triphasic response. Only the excitatory components were reduced in the presence of AA. This effect was dose-related and remained unchanged in the presence of CgA4-16 alone, but was blocked in the presence of simultaneous administration of CgA4-16 and L-NAME/apamin. AA application induced inhibition of human colon motility in vitro. This effect may be mediated through an action on L-type calcium channels. CgA4-16 may display a protective role, which prevents the inhibition of motility due to AA to occur, by acting on both smooth muscle and afferent terminals.     

Operant generalization in quail neonates after intradimensional training: Distinguishing positive and negative reinforcement

Operant generalization has been demonstrated in neonates only recently. To investigate the development of intradimensional stimulus control immediately after hatching, northern bobwhite chicks (Colinus virginianus) pecked for brief heat presentations while hearing a high-pitched sound repeated at two constant rates: an S+ tempo signaling a rich reinforcement schedule, alternating with an S− tempo signaling a leaner schedule. Tempo generalization was then assessed in extinction. The expected excitatory gradients were produced after a threshold number of training sessions; unexpectedly, below that threshold, gradients were inhibitory. The chicks’ rapidly developing thermoregulatory capability may have resulted in a change from perceived negative reinforcement initially to positive reinforcement later. Given past research showing excitatory gradients after negative reinforcement, we suggest that these results demonstrate that all negative reinforcement is not equivalent, and, further, that classical conditioning effects require consideration.     

Urethane inhibits the GABAergic neurotransmission in the nucleus of the solitary tract of rat brain stem slices

Because urethane is a widely used anesthetic in animal experimentation, in the present study, we evaluated its effects on neurons of the nucleus of the solitary tract (NTS) in brain stem slices from young rats (25-30 days old). Using the whole cell configuration of the patch-clamp technique, spontaneous postsynaptic currents (sPSCs) and evoked excitatory postsynaptic currents (eEPSCs) were recorded. Urethane (20 mM) decreased by approximately 60% the frequency of GABAergic sPSCs (1.0 +/- 0.2 vs. 0.4 +/- 0.1 Hz) but did not change the frequency, amplitude, or half-width of glutamatergic events or TTX-resistant inhibitory sPSCs [miniature inhibitory postsynaptic currents (IPSCs)]. Miniature IPSCs were measured in the presence of urethane plus 1 mM diazepam (1 mM), and no changes were seen in their amplitude. This suggests that the GABA concentration in the NTS synapses is set at saturating level. We also evaluated the effect of urethane on eEPSCs, and no significant change was observed in the amplitude of N-methyl-d-aspartate [NMDA; 44.2 +/- 11.5 vs. 37.6 +/- 10.6 pA (holding potential = 40 mV)] and non-NMDA currents [204.4 +/- 35.5 vs. 196.6 +/- 31.2 pA (holding potential = -70 mV)]. Current-clamp experiments showed that urethane did not alter the action potential characteristics and passive membrane properties. These data suggest that urethane has an inhibitory effect on GABAergic neurons in the NTS but does not change the spontaneous or evoked excitatory responses.     

Presynaptic kainate receptors modulating glutamatergic transmission in the rat hippocampus are inhibited by arachidonic acid

Kainate receptors are ionotropic glutamate receptors located postsynaptically, mediating frequency-dependent transmission, and presynaptically, modulating transmitter release. In contrast to the excitatory postsynaptic kainate receptors, presynaptic kainate receptor can also be inhibitory and their effects may involve a metabotropic action. Arachidonic acid (AA) modulates most ionotropic receptors, in particular postsynaptic kainate receptor-mediated currents. To further explore differences between pre- and postsynaptic kainate receptors, we tested if presynaptic kainate receptors are affected by AA. Kainate (0.3-3 microM) and the kainate receptor agonist, domoate (60-300 nM), inhibited by 19-54% the field excitatory postsynaptic potential (fEPSP) slope in rat CA1 hippocampus, and increased by 12-32% paired-pulse facilitation (PPF). AA (10 microM) attenuated by 37-72% and by 62-66% the domoate (60-300 nM)-induced fEPSP inhibition and paired-pulse facilitation increase, respectively. This inhibition by AA was unaffected by cyclo- and lipo-oxygenase inhibitors, indomethacin (20 microM) and nordihydroguaiaretic acid (NDGA, 50 microM) or by the free radical scavenger, N-acetyl-L-cysteine (0.5 mM). The K+ (20 mM)-evoked release of [3H]glutamate from superfused hippocampal synaptosomes was inhibited by 18-39% by domoate (1-10 microM), an effect attenuated by 35-63% by AA (10 microM). Finally, the KD (40-55 nM) of the kainate receptor agonist [3H]-(2S,4R)-4-methylglutamate ([3H]MGA) (0.3-120 nM) binding to hippocampal synaptosomal membranes was increased by 151-329% by AA (1-10 microM). These results indicate that AA directly inhibits presynaptic kainate receptor controlling glutamate release in the CA1 area of the rat hippocampus.     

A novel theoretical framework for simultaneous measurement of excitatory and inhibitory conductances

The firing of neurons throughout the brain is determined by the precise relations between excitatory and inhibitory inputs, and disruption of their balance underlies many psychiatric diseases. Whether or not these inputs covary over time or between repeated stimuli remains unclear due to the lack of experimental methods for measuring both inputs simultaneously. We developed a new analytical framework for instantaneous and simultaneous measurements of both the excitatory and inhibitory neuronal inputs during a single trial under current clamp recording. This can be achieved by injecting a current composed of two high frequency sinusoidal components followed by analytical extraction of the conductances. We demonstrate the ability of this method to measure both inputs in a single trial under realistic recording constraints and from morphologically realistic CA1 pyramidal model cells. Future experimental implementation of our new method will facilitate the understanding of fundamental questions about the health and disease of the nervous system.