Effect of psychotropic drugs on dopamine uptake by synaptosomes and glial cells

Uptake of dopamine-³H by synaptosomes and glial cells of the rabbit cerebral cortex and synaptosomes of the rat cerebral cortex was investigated. The value of K_m for dopamine-³H uptake was found to be the same (0.075±0.01 M) for both synaptosomes and glial cells. Rabbit cortical synaptosomes took up dopamine-³H twice as fast as glial cells (the rate of uptake was compared in terms of protein). Among the psychotropic drugs studied, the most active inhibitors of synaptosomal uptake were amphetamine and cocaine, but they were less active against glial uptake. Neuroleptics and antidepressants inhibited both types of uptake equally. The results are in agreement with the view that the mechanism of action of psychostimulants include a striatal dopaminergic component.Laboratory of Neurochemical Pharmacology, Institute of Pharmacology, Academy of Medical Sciences of the USSR, Moscow. Department of Biochemistry, Tbilisi University. (Presented by Academician of the Academy of Medical Sciences of the USSR V. V. Zakusov.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 87, No. 3, pp. 237–239, March, 1979.     

Uptake of tryptophan by glial cells and synaptosomes of the rabbit cerebral cortex

The uptake of L-[¹⁴C]tryptophan by glial cells and synaptosomes of the rabbit cerebral cortex was investigated. The assimilation system of the glial cells exhibits high affinity for tryptophan (K_m=0.8 M). Tryptophan uptake by the synaptosomes has lower affinity (K_m=50 M). The psychotropic drugs chlorpromazine and imipramine inhibit glial uptake. The leading role of the glial cells in the nutrition of the neurons and the normal course of neurodynamic processes is confirmed.Laboratory of Neurochemical Pharmacology, Institute of Pharmacology, Academy of Medical Sciences of the USSR, Moscow. Department of Biochemistry, Tbilisi University. (Presented by Academician of the Academy of Medical Sciences of the USSR V. V. Zakusov.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 85, No. 2, pp. 172–174, February, 1978.     

Uptake of GABA-3H by cortical glial cells and synaptosomes of rats receiving psychotropic drugs

Chlorpromazine noncompetitively inhibits the uptake of GABA-³H by both glial cells and synaptosomes, synaptosomal uptake being more sensitive to certain inhibitors. -Alanine competitively inhibits only the low-affinity GABA uptake system in the glial cells. Correlation is observed between inhibition of GABA uptake by psychotropic drugs in glial cells and synaptosomes. It is postulated that two different systems of GABA uptake with high and low affinity function in nerve endings and glial cells.Laboratory of Neurochemical Pharmacology, Institute of Pharmacology, Academy of Medical Sciences of the USSR, Moscow. Department of Biochemistry, Tbilisi University. (Presented by Academician of the Academy of Medical Sciences of the USSR V. V. Zakusov.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 83, No. 5, pp. 561–563, May, 1977.     

Changes in active uptake of noradrenalin-14C by rat brain synaptosomes during conditioning

Active uptake of noradrenalin-¹⁴C (NA-¹⁴C) by rat brain synaptosomes was shown to be inhibited by the action of ouabain (0.1 M) and during potassium depolarization. Defensive conditioning (DC) led to depression of active uptake of NA by synaptosomes. This effect may be connected both with changes in the state of the presynaptic membranes and with possible enhancement of the function of postsynaptic adrenergic receptors.Laboratory of Neurochemical Mechanisms of Conditioned Reflexes, Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR. Laboratory of General Pathology of the Nervous System, Institute of General Pathology and Pathological Physiology, Academy of Medical Sciences of the USSR, Moscow. (Presented by Academician of the Academy of Medical Sciences of the USSR A. M. Chernukh.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 87, No. 2, pp. 137–139, February, 1979.     

Effect of sodium and potassium ions on serotonin uptake by lung tissue

The dependence of serotonin (5-HT) uptake on the Na⁺ and K⁺ concentrations in the perfusion fluid was demonstrated in experiments on isolated perfused albino rat lungs. With high Na⁺ concentrations in the perfusion fluid (60–150 mM), the uptake of 5-HT by lung tissue cells was high, whereas with low Na⁺ concentrations (0–30 mM) 5-HT uptake was sharply reduced. The K⁺ concentration in the perfusion fluid had a weak effect on 5-HT uptake. Maximal uptake was observed in the presence of K⁺ in a concentration of 5 to 20 mM. A decrease or increase in K⁺ concentration retarded 5-HT uptake. 5-HT uptake was sharply inhibited by strophanithin K, an inhibitor of Na,K-ATPase, in concentrations of 10^–4–10^–3 M. A link is postulated between 5-HT transport through the cell membrane and Na⁺ transport.Department of Normal Physiology, Altai Medical Institute, Barnaul. (Presented by Academician of the Academy of Medical Sciences of the USSR N. N. Sirotinin.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 81, No. 2, pp. 145–147, February, 1976.     

Morphine treatment in early life alters glutamate uptake in the spinal synaptosomes of adult rats

Morphine exposure during the neonatal period can promote changes in pain signaling pathways that can be expressed as an increased nociceptive response in adult life. Glutamate is the major excitatory neurotransmitter in primary afferent terminals and plays a critical role in normal spinal excitatory synaptic transmission. Considering the importance of a better understanding of the mechanisms that underlie nociceptive changes throughout the life course, the aim of this study was investigate the effects of repeated morphine administration at postnatal days 8 (P8) to 14 (P14) on glutamate uptake in spinal synaptosomes at P30 and P60. The morphine group showed decreased [3H]-glutamate uptake as compared to control groups in both P30 and P60. These findings suggest that morphine exposure in early life leads to changes in glutamatergic signaling at least until the 60th day of age, which may lead to increased levels of glutamate in the spinal synaptic cleft and, consequently, an increased nociceptive response in adult life. Thus, this study highlights the importance of conducting research in this field to provide a comprehensive knowledge of the long-term effects of early-life morphine treatment on nociceptive pathways.     

Role of serotonin in the regulation of the dynorphinergic system by a kappa-opioid agonist and cocaine treatment in rat CNS

It has been shown that chronic cocaine increases prodynorphin mRNA in the caudate putamen and decreases it in the hypothalamus. In addition, treatment with a kappa-opioid receptor agonist produced the opposite effect on prodynorphin gene expression in these brain regions and also evoked a decrease in the hippocampus. It is already known that kappa-opioid receptor agonists decrease the development of sensitization to some of the behavioral effects of cocaine. The serotonin system has also been shown to regulate dynorphin gene expression and a continuous infusion of fluoxetine induced prodynorphin gene expression in the same pattern as the kappa-opioid agonist (+)(5a,7a,8b)-N-methyl-N-[7-(1-pyrrolidinyl)-1 oxaspiro[4.5]dec-8-yl]-benzeneacetamide (U-69593) in the brain regions investigated. It is interesting to note that treatment with a continuous infusion of cocaine produced different effects on this parameter. To determine whether serotonin plays a role in the regulation of prodynorphin mRNA by kappa-opioid agonists or cocaine, rats were treated with the serotonin depleter parachloroamphetamine (PCA). Beginning 24 h later, rats were treated with the selective kappa-opioid agonist U-69593 for 5 days or continuously with cocaine for 7 days and prodynorphin mRNA was measured. Prodynorphin mRNA was decreased significantly in the hypothalamus, caudate putamen, and hippocampus of rats treated with a single injection of PCA. Subsequent to PCA administration the effects of U-69593 or cocaine on prodynorphin mRNA were differentially affected across brain regions. Prodynorphin gene expression was still increased by U-69593 treatment in the hypothalamus and decreased in the caudate putamen. Cocaine treatment still produced a decrease in this parameter in the hypothalamus and an increase in the caudate putamen. In contrast, in the hippocampus, the decrease in prodynorphin mRNA produced by U-69593 was no longer evident after PCA and cocaine, which previously had no effect, now increased it in the serotonin-depleted group. These findings suggest that serotonin is necessary to maintain normal levels of dynorphin mRNA in all of the investigated brain areas and that the regulation of prodynorphin mRNA expression by chronic treatment with a kappa-opioid receptor agonist or cocaine requires serotonin in the hippocampus, but not in the hypothalamus or caudate putamen.     

Effect of psychotropic drugs on synaptosomal uptake of H3-γ-aminobutyric acid and on Na,K-ATPase activity

Neurotropic drugs belonging to various groups (fluphenazine, nonachlazine, trifluperidol fluacizine, imipramine, diazepam, apomorphine fetanyl, diphenylhydantoin) in experiments in vitro showed an inhibitory effect on active transport of -aminobutyric acid (GABA) by synaptosomes of the rat cerebral cortex. In most cases a parallel decrease in the activity of synaptosomal Na,K-ATPase was observed. Substances not changing GABA uptake as a rule had no effect on the activity of the enzyme (carbidine and morphine). Some substances inhibiting Na,K-ATPase were ineffective with respect to GABA uptake (azabuperon, tetrabenazine). It is suggested that the drugs tested have at least two possible points of application: Na,K-ATPase and the hypothetical transmembrane carrier of GABA.Institute of Pharmacology, Academy of Medical Sciences of the USSR. Institute of General Pathology and Pathological Physiology, Academy of Medical Sciences of the USSR, Moscow. (Presented by Academician of the Academy of Medical Sciences of the USSR V. V. Zakusov.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 81, No. 1, pp. 45–47, January 1976.     

Hypoxic effects on glutamate uptake in cultured glial cells

Hypoxic effects on glutamate uptake and ATP content in glial cells were investigated by using cultured C6 glioma cells. Mild regressive changes were found depending on the duration of the hypoxic insult, but necrosis or detachment of the cells from the substratum was rarely observed. Glutamate uptake was relatively well preserved after a short hypoxic insult, while a marked decrease in glutamate uptake was observed after hypoxia of long duration. The uptake of sucrose was reduced in a similar pattern to glutamate uptake. Hypoxic insult resulted in a significant reduction of the ATP content in glial cells. Therefore, the decrease in glutamate uptake by glial cells under hypoxia is likely to be due to ATP dependency, and not to the failure of a specific glutamate uptake system, but the failure of a general uptake of the glial cells owing to the energy-dependent membrane dysfunction by ATP depletion. These findings suggest that there are phased changes of astrocytic functions in a hypoxic condition, a preservative phase in the initial stages and then a dysfunctional phase in the later stages of hypoxia.     

Ultrastructural mechanisms of serotonin demyelination

The effect of serotonin on the ultrastructure of the white matter in the CNS of dogs was studied. Intracisternal injection of the amine (6 g in 0.1 ml physiological saline) led to considerable disturbances in the myelin and glia in regions of the white matter of the spinal cord adjacent to the cerebrospinal fluid channels. Loss of the regular structure and separation of the lamellae of the myelin with rupture and lysis of the myelin sheath and demyelination were observed. Vacuolar degeneration was observed in the oligodendrocytes; the astrocytes were virtually unchanged. After local intracerebral injection of the amine (2 g in 0.01 ml physiological saline) similar disturbances developed in the white matter of the cerebral hemispheres, but with features of an inflammatory reaction in the late stages of the investigation. In control animals which received injections of physiological saline, changes appeared later and only in the gliocytes. It is concluded that serotonin has the property of injuring myelin and glia.Medical Institute, Rostov-on-Don. (Presented by Academician of the Academy of Medical Sciences of the USSR A. D. Ado.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 83, No. 5, pp. 606–610, May, 1977.