ABSTRACT
Although a large body of evidence shows that pretreatment of brain tissue with creatine protects against anoxic injury in vitro, only a couple of papers have investigated creatine protection in vivo, and they yielded conflicting results. We attempted to clarify how creatine may be protective in an in vivo model of global cerebral ischemia (GCI). We administered creatine either before of after GCI. We decided to administer it by intracerebroventricular infusion, to maximize its bioavailability to the brain. Our findings show that creatine is clearly protective in vivo when administered before ischemia. In that case, histological evaluation of damage was consistently improved in all regions examined, and neurological score was better in creatine-treated rats than in controls. When administered after ischemia, histology was improved in the hippocampus, while only a not significant trend toward improvement was observed in the cerebral cortex and in the caudo-putamen. Neurological score was not improved by creatine administration after GCI. Our findings show that creatine administration is protective in vivo. Such protection was clear in the case of pretreatment, and was present, to a lesser degree, when treatment was started after ischemia. Our results should encourage further research in the possible role of creatine therapy in neuroprotection.
Subject(s)
Brain Ischemia/complications , Cerebral Infarction/etiology , Cerebral Infarction/prevention & control , Creatine/administration & dosage , Neuroprotective Agents/administration & dosage , Animals , Disease Models, Animal , Drug Administration Schedule , Hippocampus/pathology , Injections, Intraventricular/methods , Male , Neurologic Examination , Neurons/drug effects , Neurons/pathology , Rats , Rats, Sprague-Dawley , Severity of Illness Index , Time FactorsABSTRACT
Experiments were performed to address the dynamics of evoked focal potentials in slices of rat olfactory cortex during 10-min anoxia and subsequent reoxygenation. These experiments showed that perfusion with corticotropin-releasing factor (CRF)--corticoliberin--at concentrations of 1, 10, and 100 nM had no effect on changes in EPSP parameters before or during anoxia. However, CRF (10 and 100 nM) significantly aided recovery of the amplitude and slope of EPSP during reoxygenation. Application of the competitive NMDA receptor blocker APV (50 microM) during reoxygenation did not eliminate the protective effects of CRF on neuronal activity.
Subject(s)
Corticotropin-Releasing Hormone/physiology , Evoked Potentials/physiology , Hypoxia/physiopathology , Olfactory Pathways/physiology , Valine/analogs & derivatives , Action Potentials/drug effects , Action Potentials/physiology , Animals , Electric Stimulation , Evoked Potentials/drug effects , Excitatory Postsynaptic Potentials/drug effects , Excitatory Postsynaptic Potentials/physiology , Olfactory Pathways/drug effects , Organ Culture Techniques , Oxygen/metabolism , Rats , Rats, Inbred WKY , Receptors, N-Methyl-D-Aspartate/antagonists & inhibitors , Statistics, Nonparametric , Valine/pharmacologyABSTRACT
The experiments were performed on incubated slices of the rat rostal olfactory cortex. The slices were treated with various concentrations (10(-7) to 10(-9)) of corticotropin-releasing factor before (40 min), during, and after a 10-minute anoxic episode. The parallel control experiments were carried out without CRF. A 10-minute anoxia, both in control experiments and in perfusion with CRF, resulted in an approximately equal decrease of field excitatory postsynaptic potential's (fEPSP) amplitude. However, CRF at 10 nM and 100 nM concentrations protected the fEPSP amplitude. The selected NMDA receptor antagonists 2-amino-5-phosphonopentanoate (AP5) added in the perfusion medium after the anoxia, did not eliminate the neuroprotective effect of CRF.
Subject(s)
Corticotropin-Releasing Hormone/pharmacology , Evoked Potentials/drug effects , Olfactory Pathways , Oxygen/metabolism , Animals , Culture Techniques , Evoked Potentials/physiology , Male , Olfactory Pathways/drug effects , Olfactory Pathways/metabolism , Olfactory Pathways/physiology , Rats , Rats, Inbred WKYABSTRACT
The corticotropin-releasing factor (CRF) is a hypothalamic peptide that regulates the release of adrenocorticotropic hormone (ATCH) and of beta-endorphin. It has been suggested that it modulates learning and memory processes in rat. However, the electrophysiological effects that CRF produces on hippocampal neurons have been so far little investigated. In particular, the effects of CRF on long-term potentiation (LTP), a phenomenon which is thought to be the substrate of memory processes, are unknown. We studied the effects of sustained administration of CRF and of two of its receptor agonists on basal neuronal activity and on in vitro hippocampal LTP. The two receptor agonists were D-Glu-20-CRF and D-Pro-5-CRF, selective for the CRF-R1 and the CRF-R2 receptors, respectively. We found that CRF, D-Pro-5-CRF and D-Glu-20-CRF at the concentration of 1 nM diminish the amplitude of hippocampal population spike and prevent the onset of LTP. Higher concentrations of CFR have less depressing effects on neuronal activity, yet they still prevent the occurrence of LTP.
Subject(s)
Corticotropin-Releasing Hormone/pharmacology , Hippocampus/drug effects , Receptors, Corticotropin-Releasing Hormone/agonists , Action Potentials/drug effects , Animals , Corticotropin-Releasing Hormone/administration & dosage , Corticotropin-Releasing Hormone/analogs & derivatives , Electrophysiology , Female , In Vitro Techniques , Long-Term Potentiation/drug effects , Rats , Rats, Sprague-DawleyABSTRACT
Perfusion of the rat olfactory cortex slices with 1 mcM corticotropin-releasing factor (CRF) increased the rate of initiation of the posttetanic potentiation. The latter had a shorter supporting phase than in the control. With the perfusion, with 0.1 mcM the potentiation had a longer supporting phase than in the control.
Subject(s)
Corticotropin-Releasing Hormone/physiology , Long-Term Potentiation , Olfactory Pathways/physiology , Animals , Corticotropin-Releasing Hormone/pharmacology , Excitatory Postsynaptic Potentials , In Vitro Techniques , Long-Term Potentiation/drug effects , Male , Olfactory Pathways/drug effects , Rats , Rats, WistarABSTRACT
Free hand isolation of adult rabbit vestibular Deiters' neurons and dissection of their single membranes allows the study of their ionic permeability characteristics in a microchambers device. In the case of hare-like rabbits, the dissection of such membranes presents evidence of a high basal permeation of labelled chloride, possibly related to mechanical disturbance of the plasma membrane-related cytoskeleton and activation of chloride channels. This did not apply to the laboratory strain of white New Zealand rabbits. However, membranes from hare-like rabbits which were stressed by being rotated on a platform before the experiment, behaved like those from the New Zealand strain. Vice versa, habituation to handling day after day of New Zealand rabbits resulted in a chloride permeation equal to that of unstressed hare-like rabbits. We propose that the stressful conditions result in the release of neurochemical messages to the vestibular Deiters' cells which influence their electrophysiological behavior. The corticotropin releasing factor (CRF), a stress-related peptide present in the climbing fibers, actually blocks the basal chloride permeation across the Deiters' membranes and this effect is partially reversed by its receptor antagonist, alpha-helical CRF [9-41].
Subject(s)
Cell Membrane Permeability/physiology , Cell Membrane/metabolism , Chloride Channels/metabolism , Corticotropin-Releasing Hormone/metabolism , Neurons/metabolism , Stress, Physiological/metabolism , Vestibular Nucleus, Lateral/metabolism , Acute Disease , Animals , Behavior, Animal/physiology , Cell Membrane/drug effects , Cell Membrane Permeability/drug effects , Chloride Channels/drug effects , Corticotropin-Releasing Hormone/drug effects , Habituation, Psychophysiologic/physiology , Male , Neurons/drug effects , Rabbits , Stress, Physiological/physiopathology , Vestibular Nucleus, Lateral/drug effectsABSTRACT
Intracerebroventricular (ICV) administration of creatine increased cerebral phosphocreatine in normal rats by 67%, the highest increase so far reported in an in vivo model. We used osmotic minipumps (Alzet, Palo Alto, CA, USA) to administer creatine, 0.5 mM, to the lateral ventricle at the rate of 10 microl/h for 3 days. Brain phosphocreatine in saline-treated controls was 33 +/- 17 microM/g protein (mean +/- SD, N = 9). In creatine-treated rats (0.5 mM for 3 days) such content was 55 +/- 17 microM/g protein (mean +/- SD, N = 7). This difference is statistically significant (p = 0.02, t-test). The increase we found in cerebral phosphocreatine is of an order of magnitude comparable to the increase previously found in in vitro experiments, and may be effective in protecting brain tissue from ischemic damage.
Subject(s)
Brain/metabolism , Creatine/administration & dosage , Phosphocreatine/metabolism , Animals , Injections, Intraventricular , Male , Rats , Rats, Sprague-DawleyABSTRACT
Cell membrane recordings were made in conditions of voltage clamping with tight attachment of the microelectrode-patch clamping--to study the effects of morphine on tetrodotoxin-resistant (TTXr) sodium channels in rat spinal ganglion neurons in culture. The effects of a number of biologically active substances which regulate the receptor-mediated actions of morphine were studied. The effects of morphine were found to involve a chain of sequential reactions leading to decreases in the transfer of effective charge (Zeff) by the activatory gate system of TTXr sodium channels, depending on the concentration of agonist in the extracellular solution. A value of 8 nM was obtained for KD. with a Hill coefficient of X = 0.5. Non-specific antagonists of opioid receptors blocked the actions of morphine; these included ouabain at a concentration of 100 microM. An inhibitor, and activator, and a blocker of G-proteins had no effect on the effective charge. These data provide evidence that morphine decreases the voltage sensitivity of TTXr sodium channels.
Subject(s)
Morphine/pharmacology , Narcotics/pharmacology , Sodium Channels/drug effects , Sodium Channels/physiology , Animals , Cells, Cultured , Drug Resistance , Electrophysiology , Enzyme Inhibitors/pharmacology , Ganglia, Spinal/cytology , Ganglia, Spinal/metabolism , Ion Channel Gating/physiology , Models, Neurological , Naloxone/pharmacology , Narcotic Antagonists/pharmacology , Neurons/metabolism , Osmolar Concentration , Ouabain/pharmacology , Patch-Clamp Techniques , Rats , Rats, Wistar , Receptors, Opioid/physiology , Sodium-Potassium-Exchanging ATPase/antagonists & inhibitors , Tetrodotoxin/pharmacologyABSTRACT
Morphine was shown to decrease in a dose-dependent manner the effective charge transfer in tetrodotoxin-resistant (TTXr) sodium channel activation system in short-term cultured dorsal root ganglion cells. Morphine seems to interact with opioid receptors because of total block of the binding by naloxone and naltrexone. Neither activating, nor inhibiting G-protein agents exerted any effect on this process. The morphine signal was blocked by extracellular application of 2 x 10(-4) M ouabain. The findings suggest existence of sodium signalling pathway involving receptors, Na+, K(+)-ATPase and the TTXr sodium channels.
Subject(s)
Morphine/pharmacology , Neurons/drug effects , Sodium Channels/drug effects , Animals , Cell Membrane , Cells, Cultured , Ganglia, Spinal/cytology , Morphine/metabolism , Neurons/physiology , Patch-Clamp Techniques , Rats , Rats, Wistar , Receptors, Opioid/agonists , Receptors, Opioid/metabolism , Sodium Channels/physiology , Sodium-Potassium-Exchanging ATPase/drug effects , Sodium-Potassium-Exchanging ATPase/physiology , Tetrodotoxin/pharmacologyABSTRACT
Enzymatic methods were used to demonstrate an increase in the activity of G-proteins and protein kinase A in the brain of the common snail at early stages of learning. There were no differences in the activity of G-proteins in the brain between young (unable to learn) and adult snails. Snail brain protein kinase C activity was unchanged compared to controls 20-40 minutes after the end of the training procedure. It is concluded that cAMP-dependent phosphorylation and cAMP-dependent activation of early gene expression have active roles in learning in the snail. The question of the role of additional intracellular regulatory systems in learning in the snail is discussed.
Subject(s)
Behavior, Animal/physiology , Conditioning, Classical/physiology , GTP-Binding Proteins/physiology , Helix, Snails/physiology , Neuronal Plasticity/physiology , Second Messenger Systems/physiology , Animals , Brain Chemistry , Cyclic AMP-Dependent Protein Kinases/metabolism , Ganglia, Invertebrate/metabolism , Nervous System/metabolism , Protein Kinase C/metabolismABSTRACT
Long-term potentiation was elicited in living slices of rat olfactory cortex by stimulation of the lateral olfactory tract. A group of interdependent parameters of membrane metabolism was studied, i.e., the kinetics of 45Ca metabolism, lipid peroxidation, and antioxidant defense; cytochemical measurements were made of Na+, K(+)-ATPase activity in neurons and glial cells; the functional (GTPase) activity of G-proteins was also studied. All parameters were compared with the bioelectrical activity of slices at three time points after tetanization, i.e., 3-5, 15, and 30 min. In most cases, regular phasic changes in metabolic parameters occurred, and their functional significance is discussed.
Subject(s)
Brain Chemistry/physiology , Long-Term Potentiation/physiology , Acetylcholine/metabolism , Animals , Antioxidants/metabolism , Brain/enzymology , Calcium/metabolism , Electric Stimulation , GTP Phosphohydrolases/metabolism , In Vitro Techniques , Kinetics , Lipid Peroxidation/physiology , Membranes/metabolism , Neuroglia/metabolism , Neurons/metabolism , RatsABSTRACT
Na+,K(+)-ATPase and Mg(2+)-ATPase activities were studied in neurons and glial cells of the olfactory cortex of the rat by quantitative cytophotometry in conditions of long-term potentiation (LTP), and significant changes in direction and extent were found. Na+,K(+)-ATPase activity decreased in neurons in the first 15 min after LTP, with subsequent elevation by 30 min. Mg(2+)-ATPase activity remained unchanged in these conditions. Glial cells showed significant increases in Na+,K(+)-ATPase activity in the initial period after LTP, with return to control by 30 min. Again, there were no significant changes in Mg(2+)-ATPase activity. The formation and persistence of LTP in neurons and glial cells was accompanied by significant changes in Na+,K(+)-ATPase activity, which were reciprocal in nature.
Subject(s)
Long-Term Potentiation/physiology , Neuroglia/enzymology , Neurons/enzymology , Olfactory Pathways/enzymology , Sodium-Potassium-Exchanging ATPase/metabolism , Animals , Ca(2+) Mg(2+)-ATPase/metabolism , Electric Stimulation , Neuroglia/physiology , Neurons/physiology , Olfactory Pathways/physiology , Rats , Rats, WistarABSTRACT
An increase in the activity of G-proteins and protein kinase A was shown in the brain of Helix at the early stages of learning. The protein kinase C activity did not differ from the baseline in 20-40 min after training. There was no difference between the brain G-protein activities in the young (unable to learn) and adult snails. A conclusion is drawn that the system of cAMP-dependent phosphorylation and cAMP-dependent activation of the early genes actively participate in learning of Helix. The participation of additional systems of intracellular regulation in learning is discussed.
Subject(s)
Avoidance Learning/physiology , Conditioning, Classical/physiology , GTP-Binding Proteins/physiology , Helix, Snails/physiology , Neuronal Plasticity/physiology , Second Messenger Systems/physiology , Aging/physiology , Animals , Brain/physiology , Cyclic AMP-Dependent Protein Kinases/physiology , Protein Kinase C/physiologyABSTRACT
A group of interrelated parameters of the membrane metabolism was studied during stimulation of the lateral olfactory tract in the rat brain slices of olfactory cortex. All the parameters were studied in respect to electrical activity of the slices in three temporal points after the tetanisation: 3-5, 15, and 30 min. Regular phasic alterations of the metabolism parameters occurred in most of the cases. Their functional significance is discussed.
Subject(s)
Cerebral Cortex/metabolism , Long-Term Potentiation/physiology , Animals , Antioxidants/metabolism , Cell Membrane/metabolism , Electric Stimulation , Histocytochemistry , In Vitro Techniques , Lipid Peroxidation , Rats , Time FactorsABSTRACT
The initial stationary phase of the LTP was followed by a decrease in the Na(+),K(+)-ATPase activity of neurons and an augmentation of enzyme activity in the glial cells. Decay of the LTP tends to normalize the above types of activity.
Subject(s)
Long-Term Potentiation/physiology , Neuroglia/enzymology , Neurons/enzymology , Olfactory Pathways/enzymology , Sodium-Potassium-Exchanging ATPase/metabolism , Animals , Ca(2+) Mg(2+)-ATPase/metabolism , In Vitro Techniques , Rats , Rats, Wistar , Time FactorsABSTRACT
AI, B29 insulin polymeric derivatives in which the polymeric chains (N-polyvinylimidazole, N-polyvinylpyrrolydone and polyacrylic acid) are bonded to the insulin molecule at one point were synthesized. The hydrolysis of the modified insulin by trypsin is dependent to a great extent on the chemical nature of the modifying polymer and is virtually independent of its molecular weight up to 20 kD. The effect of the modifying polymer manifests itself mainly in a change of the Michaelis constant. Investigation of the conformational properties of the insulin derivatives by the method of optical rotatory dispersion revealed that insulin modification by polymers caused a decrease of the amino acid content in the alpha-helical sequence from 41 to 33-30%. The chemical nature of the modifying polymer and its molecular weight have a profound effect on the conformational stability of the residual spatial structure of the modified insulin in alkaline media.
Subject(s)
Insulin/analogs & derivatives , Polymers , Amino Acids/analysis , Hydrolysis , Insulin/chemical synthesis , Insulin/metabolism , Kinetics , Molecular Weight , Protein Conformation , Trypsin/metabolismABSTRACT
The effect of insulin and its seven synthetic derivatives on spontaneous bioelectrical activity of the cerebral cortex of rabbits was described in the paper. The influence of these substances on consolidation of long-term memory of white rats was shown at normal state and during experimental neurosis. Insulin was supposed to influence the higher nervous activity not only through glucose metabolism but also by means of increase of permeability of biological membranes for amino acids.
Subject(s)
Brain/physiopathology , Conditioning, Classical/physiology , Insulin/therapeutic use , Neurotic Disorders/drug therapy , Animals , Chinchilla , Electroencephalography , Female , Humans , Insulin/analogs & derivatives , Insulin/physiology , Male , Memory/physiology , Neurotic Disorders/physiopathologyABSTRACT
An intramolecular modification of insulin at the alpha-amino group of glycine (A1) and the epsilon-amino group of lysine (B29) was carried out. The modification resulted in a slight alteration of the insulin secondary structure; the modified hormone possessed a biological activity which was practically identical to that of the natural hormone. Therefore the modified insulin can be used as a high molecular weight physiologically active radical inducer for the synthesis of (A1-B29) polyvinylimidazole derivatives. The molecular weight of the covalently linked polymer can be variable. It was shown that the increase in the amount of modifying polymer in the conjugate results in stabilization of the insulin secondary structure concomitant with a decrease of the biological activity and, moreover, of the immunoresponsiveness of the hormone.
Subject(s)
Insulin/analogs & derivatives , Animals , Biological Assay , Blood Glucose/analysis , Indicators and Reagents , Insulin/chemical synthesis , Insulin/pharmacology , Macromolecular Substances , Molecular Weight , Protein Conformation , Rabbits , Structure-Activity RelationshipABSTRACT
Lysyl and tetralysyl derivatives of insulin on phenylalanine of chain B were synthesized. The effects of modifications on the spatial structure and biological properties of the hormone were studied. It was found that an increase in the length of the modifier leads to a distortion of the hormone spatial structure resulting in a decrease of its biological activity.