GABA agonists and neurotransmitters metabolizing enzymes in steroid-primed OVX rats

The effect of intraventricular (IVT) administration of GABAA receptor agonist muscimol and GABAB receptor agonist, baclofen was examined on the activity of acetylcholinesterase (AChE), monoamine oxidase (MAO) and Na+, K(+)-ATPase in discrete areas of brain from estrogen-progesterone primed ovariectomized rats. AChE enzyme activity was increased in two subcellular fractions (soluble and total particulate) studied, with statistically significant changes in cerebral hemispheres (CH), cerebellum (CB), thalamus (TH) and hypothalamus (HT), Na+, K(+)-ATPase enzyme activity was decreased in both these fractions. MAO activity increased significantly in CH, TH and HT. The presented results suggest a functional relationship between GABAergic (inhibitory), cholinergic and monoaminergic (excitatory) systems by affecting the rate of degradation of the excitatory neurotransmitters and Na+, K(+)-ATPase.     

Amino-terminal dimerization of an erythropoietin mimetic peptide results in increased erythropoietic activity

BACKGROUND: Erythropoietin (EPO), the hormone involved in red blood cell production, activates its receptor by binding to the receptor's extracellular domain and presumably dimerizing two receptor monomers to initiate signal transduction. EPO-mimetic peptides, such as EMP1, also bind and activate the receptor by dimerization. These mimetic peptides are not as potent as EPO, however. The crystal structure of the EPO receptor (EBP) bound to EMP1 reveals the formation of a complex consisting of two peptides bound to two receptors, so we sought to improve the biological activity of EPO-mimetic peptides by constructing covalent dimers of EMP1 and other peptide mimetics linked by polyethylene glycol (PEG). RESULTS: The potency of the PEG-dimerized EPO peptide mimetics both in vitro and in vivo was improved up to 1,000-fold compared to the corresponding peptide monomers. The dimers were constructed using peptide monomers which have only one reactive amine per molecule, allowing us to conclude that the increase in potency can be attributed to a structure in which two peptides are linked through their respective amino termini to the difunctional PEG molecule. In addition, an inactive peptide was converted into a weak agonist by PEG-induced dimerization. CONCLUSIONS: The potency of previously isolated peptides that are modest agonists of the EPO receptor was dramatically increased by PEG-induced dimerization. The EPO receptor is thought to be dimerized during activation, so our results are consistent with the proposed 2:2 receptor : peptide stoichiometry. The conversion of an inactive peptide into an agonist further supports the idea that dimerization can mediate receptor activation.     

Glutamate inhibits GABA excitatory activity in developing neurons

In contrast to the mature brain, in which GABA is the major inhibitory neurotransmitter, in the developing brain GABA can be excitatory, leading to depolarization, increased cytoplasmic calcium, and action potentials. We find in developing hypothalamic neurons that glutamate can inhibit the excitatory actions of GABA, as revealed with fura-2 digital imaging and whole-cell recording in cultures and brain slices. Several mechanisms for the inhibitory role of glutamate were identified. Glutamate reduced the amplitude of the cytoplasmic calcium rise evoked by GABA, in part by activation of group II metabotropic glutamate receptors (mGluRs). Presynaptically, activation of the group III mGluRs caused a striking inhibition of GABA release in early stages of synapse formation. Similar inhibitory actions of the group III mGluR agonist L-AP4 on depolarizing GABA activity were found in developing hypothalamic, cortical, and spinal cord neurons in vitro, suggesting this may be a widespread mechanism of inhibition in neurons throughout the developing brain. Antagonists of group III mGluRs increased GABA activity, suggesting an ongoing spontaneous glutamate-mediated inhibition of excitatory GABA actions in developing neurons. Northern blots revealed that many mGluRs were expressed early in brain development, including times of synaptogenesis. Together these data suggest that in developing neurons glutamate can inhibit the excitatory actions of GABA at both presynaptic and postsynaptic sites, and this may be one set of mechanisms whereby the actions of two excitatory transmitters, GABA and glutamate, do not lead to runaway excitation in the developing brain. In addition to its independent excitatory role that has been the subject of much attention, our data suggest that glutamate may also play an inhibitory role in modulating the calcium-elevating actions of GABA that may affect neuronal migration, synapse formation, neurite outgrowth, and growth cone guidance during early brain development.     

Opioid and GABA modulation of accumbens-evoked ventral pallidal activity

The purpose of this work has been to establish the pattern of prenatal growth and normal development of the digestive tract and annex glands during goat embryonic stages. 21 embryos with ages ranging from 14 to 34 days (1.69 to 5.90 cm CR) as determined by registering the mating time, were obtained by cesarean section. This material was histologically processed to obtain complete serial sections of the stomatodaeum, foregut, midgut, hindgut and cloaca. In this work, it is chronologically described the morphogenesis and histogenesis of the mouth, hypophysis, pharynx and its derivatives, stomach, intestine, liver, pancreas and cloaca. The results obtained establish chronological comparisons with the development of the lamb and gives information on the unitary origin of the gastric compartments in ruminants.     

Anti-ulcerogenic properties of psychostimulants of the phenylalkylsydnone imine series

In rats, administration of 96% ethanol to the stomach causes ulcerative damages to its mucosa just 8 minutes later, which are of significant dimensions, reaching their maximum size following 3 hours. The sydnonimine psychostimulant OF-743 in combination with ethanol substantially reduces mucosal damage. The use of ethanol after OF-743 injections results in less ulcerative damage. The findings suggest that the drug has not only protective (preventive) effects, but beneficial properties.     

Cardiovascular responses to intracerebroventricular injection of GABA in renovascular hypertensive rats

Effects of central GABAergic stimulation on cardiovascular function were evaluated in 2-kidney, 1-clip (2K1C) renovascular hypertensive rats (RVHR). Intracerebroventricular injection (icv) of GABA (100 and 200 micrograms) reduced blood pressure (BP) to a greater degree in RVHR as compared with sham-operated controls, and the greatest response was seen in RVHR 4 wk after operation (4 wk-RVHR). In addition, a decreased sensitivity of baroreflex was observed in 4 wk-RVHR, and was improved by icv GABA. Pretreatment with icv captopril (200 micrograms) only reduced BP moderately in 4 wk-RVHR, but attenuated remarkably the depressor effect of GABA. On the contrary, pretreatment with ip captopril was less effective in attenuating the depressor effect of GABA. Our results indicated that RVHR was deficient in central GABAergic inhibition on BP control, for GABAergic stimulation reduced BP to a greater degree and improves the decreased sensitivity of baroreflex in RVHR; the depressor effect of GABA is mediated, at least in part, by inhibiting brain angiotensin system.     

Effects of the GABA mimetic drug, sodium valproate, on event-related potentials and its relation to the law of initial value

The effects of gamma-aminobutyric acid (GABA) mimetic drug sodium valproate (VPA) on event-related potentials (ERPs) were investigated in 18 healthy volunteers during an auditory odd ball task. VPA (200 or 400 mg) or an inactive placebo was administered according to a completely randomized double-blind, cross-over design. ERPs were recorded one hour after medication was given. VPA did not affect the latencies of N100, P200, N200 and P300. Although on the whole VPA had no effect on the amplitudes of the ERP components in the subjects, it increased the P300 amplitude in the low P300 amplitude subjects and decreased it in the high P300 amplitude subjects. This tendency toward a bidirectional response was also seen in the P200 and N200 amplitudes. It was concluded that the response which takes place being dependent on the difference in the initial values was recognized on the effect of a single administration of 200 or 400 mg VPA to ERPs. The results of this study are discussed, especially in relation to the law of initial value.     

Occurrence of GABA and GABA receptors in human spermatozoa

Acute graft-versus-host disease (GVHD) is effected by donor T lymphocytes which have been stimulated by host antigens. Activated donor T lymphocytes express interleukin-2 receptor (IL-2R), which is comprised of three subunits (alpha, beta, gamma). During activation, the a IL-2R subunit (CD25) is shed from the receptor complex and can be measured in the circulation. Soluble IL-2Ralpha (sIL-2R) levels are increased in states of immune activation including GVHD, and could theoretically be used as a guide to therapy. Since IL-2Ralpha expression is an early marker of T cell activation, we investigated: (1) if an increase in sIL-2R is specific for acute GVHD; and (2) if serial sIL-2R levels can identify patients with early GVHD, prior to the onset of clinical tissue damage (effector function). Weekly sIL-2R levels were monitored in 36 patients undergoing matched related (n=23) or matched unrelated (n=13) allogeneic bone marrow transplantation (BMT). There was no significant difference in sIL-2R levels between matched related and matched unrelated recipients. Patients with acute GVHD (n=19, 53%) demonstrated higher sIL-2R levels, than those without during weeks 2 and 3 post-BMT (P=0.02 and 0.04, Mann-Whitney U test, two-tailed). In patients with acute GVHD, the rise in sIL-2R preceded the clinical signs of GVHD (16/19 patients). However, patients with sepsis demonstrated a trend towards higher sIL-2R levels at week 1 and significantly greater levels by week 4 (P=0.02). Furthermore, patients with veno-occlusive disease (VOD) (25%) also had significantly higher sIL-2R levels at week 2 (P=0.03). We conclude that although sIL-2R levels increase in patients with acute GVHD, similar increases are seen in patients with VOD and/or sepsis and therefore, as a single biochemical marker, we find that serial measurements of sIL-2R lacks sufficient specificity to guide GVHD therapy.     

Effects of the GABA agonists baclofen and THIP on long-term compensation in hemilabyrinthectomised rats

Horizontal eye movements, elicited by sinusoidal rotation in darkness, were recorded with a magnetic search coil technique in pigmented rats, hemilabyrinthectomised 8-12 weeks before the investigation. Separate gains during rotation towards the lesioned side (LS) and the intact side (IS) were calculated by a computer program, demonstrating an asymmetry. Systemic single administration of the GABAB agonist baclofen caused a dose-related temporary rebalancing of the compensatory eye movements to the LS and the IS. At an optimal dose of 14 micromol/kg b.wt symmetry was achieved by excitation of eye movements during rotation to the LS and depression during rotation to the IS. Administration of the GABAA agonist THIP did not obviously reduce the asymmetry. It is suggested that stimulation of GABAB receptors modifies the tonic imbalance between the bilateral vestibular nuclei and/or the central processing of the input from the peripheral sensory organs.     

A developmental dissociation of context and GABA effects on extinguished fear in rats.

Although extinction has attracted considerable attention in recent years, there has been very little empirical work on extinction during development. Using Pavlovian fear conditioning, the authors provide evidence for developmental differences in extinction. Specifically, Postnatal Day (PND) 23 rats exhibited recovery of an extinguished freezing response to an auditory conditioned stimulus when tested in a context different from that in which extinction occurred (i.e., renewal) or when injected with the gamma-amino butyric acid (GABA) inverse agonist FG7142 prior to test. In contrast, PND 16 rats failed to exhibit either of these effects, although a subsequent experiment demonstrated that FG7142 alleviated spontaneous forgetting in PND 16 rats. Taken together, it appears that there are fundamental differences in the processes involved in extinction across development. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Affect and mimetic behavior]

The relationship between facial expression and experienced affect presents many problems. The two diametrically opposed positions proposing solutions to this problem are exemplified using the conceptions of Mandler u. Izard. The underlying premises of both conceptions still prevail in various forms. The authors reject the concepts according to which facial expression is merely correlated to the affects (see Mandler 1975) as well as the view that facial expression controls the affects (see Izard 1977). The relationship between affect and facial expression is reexamined, subjecting it to a semiotic, essentially semantic analysis similar to the Ogden and Richards' language and meaning approach. This analysis involves a critical discussion of Scherer's attempt of a purely communicational interpretation using Bühler's organon model. In the author's approach, facial expression is seen not simply as a system of signals, but as a system of representative signs which signify the affects and refer to the emotive meaning of things for the subject. The authors develop the thesis that human beings are not born simply with the ability to speak, but also with the abstract possibility of performing facial expressions. This ability develops by way of coordinating patterns of expressions, which are presumably phylogenetically determined, with affects that take on a socially determined individual form, similar to language acquisition during socialisation. The authors discuss the methodological implications arising for studies investigating the affective meaning of facial expressions.     

A short-term assessment of tumor-promotion activity in the livers of rats treated with two genotoxic methylating agents: dimethylnitrosamine and methylnitrosourea

Induction of replicative DNA synthesis (RDS) and mitoinhibitory effects were studied in the hepatocytes of F344 rats exposed in vivo to the methylating agents dimethylnitrosamine (DMN, hepatocarcinogen) and methylnitrosourea (MNU, non-hepatocarcinogen). Cytotoxicity and chromosome aberrations (CA) in rat liver were also investigated to clarify the cause of changes in RDS and mitoinhibitory effects, respectively. The animals were killed at different intervals (up to 14 days) after a single oral dose, or 1 day after 7 or 14 days of repeated oral doses. The hepatocytes were isolated and cultured with Williams' medium E to assess their RDS, mitoinhibitory effects and CA. Mitoinhibitory effects were investigated by monitoring their effect on epidermal growth factor-induced replicative DNA synthesis (EGF-induced RDS) in rat hepatocytes. Hepatotoxic effects were assessed by measuring aspartate transaminase and alanine transaminase in the plasma and by histopathological examination. In the single-dose study, DMN (20 mg/kg body weight (bw)) induced both RDS and hepatotoxicity. MNU (50 mg/kg bw) induced RDS without causing hepatotoxicity, and thus was classified as a mitogen. In the repeated-dose study, DMN (4 mg/kg bw) induced both RDS and hepatotoxicity, but MNU (10 mg/kg bw) induced neither. Both inhibition of EGF-induced RDS and induction of CA were observed in the hepatocytes of rats treated with DMN, but were not observed with MNU in both single and repeated dose studies. The mitoinhibitory effect of DMN persisted for 14 days after the single dose and time dependently increased for 14 days after repeated administration. This mitoinhibitory effect correlated positively with CA. The mitoinhibitory effect was thought to be attributable to the DNA-damaging effect that induces CA. We concluded that the differences which we found in this study between DMN and MNU contribute to the differences in their hepatocarcinogenicity. Our findings suggested that both cell proliferative and mitoinhibitory properties play an important role in tumor promotion, and measuring them may provide an ancillary index that is useful in predicting hepatocarcinogenicity.     

Serotoninergic control of the activity and expression of glial GABA transporters in the rat cerebellum

OBJECTIVE: The purpose of the study was to compare staff versus patient perceptions of the causes and emotional impact of verbal and physical aggression on a psychiatric inpatient unit, and the corrective measures each group would endorse. METHODS: Fifty-four patients and 32 nursing staff members responded to similar questions about physical and verbal aggression. They also reported their emotional responses to aggression and steps they would endorse to reduce aggression at the medical center. Data was analyzed by chi-square tests for proportion comparisons between groups. RESULTS: "Verbal Abuse" was viewed an important contributor to physical aggression. Staff stressed patient substance abuse and violent lifestyles. Patients focused on the use of involuntary procedures and cultural differences between patients and staff. CONCLUSIONS: Patients endorsed more restrictive safety measures as long as the measures such as metal detectors and searches were applied to staff and visitors, as well as patients. Patients requested more input into decision-making processes through patient-staff workgroups.     

Role of GABA in the actions of ethanol in rats selectively bred for ethanol sensitivity

Rats from the N/Nih heterogeneous stock have been selectively bred for high (HAS) or low (LAS) initial sensitivity to injected ethanol as measured by duration of the loss of the righting reflex. The selection for ethanol sensitivity in these lines apparently has reached a maximum. These lines are useful to elucidate the central nervous system mechanisms of the genetic differences between the lines and also provide clues to the mechanisms of ethanol's action. We have found that: 1) ethanol, etomidate, and ketamine but not propofol produce different sleep times and brain levels of the drug on awakening between these two lines; 2) only ethanol, etomidate, and ketamine produced significant differences between the HAS and LAS rats in GABA-mediated stimulation of chloride uptake into brain microsacs; 3) GABA, propofol, and etomidate decreased the Kd for flunitrazepam binding to whole-brain membranes but equally in both lines. Neither ethanol nor ketamine had an effect; 4) only GABA, ethanol, and etomidate increased the Kd for TBPS binding and only GABA decreased Bmax of TBPS binding. As with the previous selection for ethanol sensitivity in mice (short and long sleep) these lines of rats have very marked line differences in GABA-mediated events, and these are correlated with the sedative effects of ethanol. From these and previous studies we know that the major differences between selected lines of mice and rats are that the mouse lines are not differentially sensitive to halothane or pentobarbital while the rat lines are. However, the mouse lines are differentially sensitive to propofol and the rat lines are not. These data should be useful in dissecting the actions of ethanol at the GABA(A) receptor.     

Antiendotoxin activity of cationic peptide antimicrobial agents

The endotoxin from gram-negative bacteria consists of a molecule lipopolysaccharide (LPS) which can be shed by bacteria during antimicrobial therapy. A resulting syndrome, endotoxic shock, is a leading cause of death in the developed world. Thus, there is great interest in the development of antimicrobial agents which can reverse rather than promote sepsis, especially given the recent disappointing clinical performance of antiendotoxin therapies. We describe here two small cationic peptides, MBI-27 and MBI-28, which have both antiendotoxic and antibacterial activities in vitro and in vivo in animal models. We had previously demonstrated that these peptides bind to LPS with an affinity equivalent to that of polymyxin B. Consistent with this, the peptides blocked the ability of LPS and intact cells to induce the endotoxic shock mediator, tumor necrosis factor (TNF), upon incubation with the RAW 264.7 murine macrophage cell line. MBI-28 was equivalent to polymyxin B in its ability to block LPS induction of TNF by this cell line, even when added 60 min after the TNF stimulus. Furthermore, MBI-28 offered significant protection in a galactosamine-sensitized mouse model of lethal endotoxic shock. This protection correlated with the ability of MBI-28 to reduce LPS-induced circulating TNF by nearly 90% in this mouse model. Both MBI-27 and MBI-28 demonstrated antibacterial activity against gram-negative bacteria in vitro and in vivo against Pseudomonas aeruginosa infections in neutropenic mice.     

Age-dependent and cell class-specific modulation of retinal ganglion cell bursting activity by GABA

Competition for postsynaptic targets during development is thought to be driven by differences in temporal patterns of neuronal activity. In the ferret visual system, retinal ganglion cells that are responsive either to the onset (On) or to the offset (Off) of light exhibit similar patterns of spontaneous bursting activity early in development but later develop different bursting rhythms during the period when their axonal arbors segregate to occupy spatially distinct regions in the dorsal lateral geniculate nucleus. Here, we demonstrate that GABAergic transmission plays an important, although not exclusive, role in regulating the bursting patterns of morphologically identified On and Off ganglion cells. During the first and second postnatal weeks, blocking GABAA receptors leads to a decrease in the bursting activity of all ganglion cells, suggesting that GABA potentiates activity at the early ages. Subsequently, during the period of On-Off segregation in the geniculate nucleus, GABA suppresses ganglion cell bursting activity. In particular, On ganglion cells show significantly higher bursting rates when GABAergic transmission is blocked, but the bursting rates of Off ganglion cells are not affected systematically. Thus, developmental differences in the bursting rates of On and Off ganglion cells emerge as GABA becomes inhibitory and as it consistently and more strongly inhibits On compared with Off ganglion cells. Because in many parts of the CNS GABAergic circuits appear early in development, our results also implicate a potentially important and possibly general role for local inhibitory interneurons in creating distinct temporal patterns of presynaptic activity that are specific to each developmental period.     

Lipid-lowering activity of phytostanols in rats

In the present study, the hypocholesterolemic activity of phytosterols and phytostanols was compared. Phytostanols were prepared by hydrogenating a phytosterol mixture from corn oil and were fed at different levels (0.1-1.0%) to male rats for 10 to 14 days with or without cholesterol (1.0%). In an appropriate combination with cholesterol, phytostanols showed significantly greater activity in lowering the plasma and possibly liver cholesterol levels in comparison with the corresponding phytosterols. The stanols further stimulated the fecal recovery of cholesterol. The rate of intestinal absorption of phytostanols appeared obviously lower than that of phytosterols and thus the deposition into plasma and liver lipids was almost negligible.     

The ultrastructure of the olivary pretectal nucleus in rats. A tracing and GABA immunohistochemical study

The Cerdanya valley in the eastern Pyrenees has a physical unity into which a political frontier has been imposed to divide it. The social and cultural repercussions of this Franco-Spanish border have created obstacles to marriage which are not due to topography. Choice of month of marriage is under cultural control and the study of seasonality in marriages recorded in the registers of all the Cerdan parishes on both sides of the border demonstrated differences over time and between French and Spanish sectors. It is suggested that these changes demonstrate the process of distancing of the two populations. Cluster and correspondence analysis showed progressive differentiation of the seasonality patterns of the French and Spanish Cerdans despite the geographic unity of the valley. Sociocultural factors are presumed responsible.     

GABA(A) receptor function in the cerebral cortex of alcohol-naive P and NP rats

In our previous paper (Biochim. Biophys. Acta 1379 (1998) 257-263), we demonstrated that bicarbonate promotes a cleavage of lactone ring of dehydroascorbate (DHA) on the basis of in vitro experiments. In the present study, we examined the degradation of DHA in blood circulation in vivo by using a high-performance liquid chromatographic method for the determination of ascorbate (AsA), DHA and 2,3-diketogulonate (2,3-DKG), which required no pretreatment of biological fluids. When DHA was intravenously administered to rats, a rapid disappearance of DHA (t1/2 < 1 min) and a concomitant appearance of 2,3-DKG in blood circulation were observed. Approximately 90% of the administered DHA were excreted into urine as resulting 2,3-DKG (55%) and AsA (31%), respectively. Furthermore, we elucidated that rat plasma lacks an enzyme having an aldonolactonase-like activity. The result of the present study suggests that this DHA disappearance is a function of both a chemical degradation to 2,3-DKG and a reduction to AsA.     

Comparative analysis of changes in respiration and systemic hemodynamics during activation of GABA receptors in cats and rats]

Rat liver mitochondrial alanine aminotransferase (mALT) is known to be a very unstable enzyme, a property that has hindered efforts to purify it. In this report we examine the possibility of stabilizing mALT with ethanol, trehalose, and protease inhibitors. The presence of ethanol was shown to slow down the inactivation of mALT, increasing its half-life from 1 to 4 h. Trehalose was found to greatly enhance the stability of mALT in a concentration-dependent manner. In the presence of 36.5% trehalose, the half-life of mALT was 85 h. Of the protease inhibitors tested only antipain and chymostatin slowed down the inactivation of mALT but only within the first 24 h following preparation of the crude enzyme. It is concluded that the inclusion of ethanol and trehalose in purification protocols could aid the purification of the enzyme. It is also concluded that the inclusion of protease inhibitors in purification protocols of mALT may not be necessary as its inactivation does not seem to be due to protease activity.