Inhibition of serotonin uptake by synaptosomes and glial cells induced by certain drugs

Uptake of [¹⁴C]serotonin by glial cells and synaptosomes in the rabbit cerebral cortex was studied. The value of K_m for serotonin uptake was the same (0.083±0.02 M) for both synaptosomes and glial cells. Cortical synaptosomes took up serotonin twice as fast as glial cells (the rates of uptake were compared as protein). Of the psychotropic drugs tested, the most active inhibitors of both synaptosomal and glial serotonin uptake were the tricyclic antidepressant imipramine and the psychostimulant cocaine which, in concentrations of 50 M, inhibited uptake of [¹⁴C]serotonin in synaptosomes by 90% and in glial cells by 75–80%.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. 88, No. 11, pp. 564–566, November, 1979.     

Modulation of Ca channels by activation of adenosine A1 receptors in rat striatal glutamatergic nerve terminals

We determined that activation of adenosine A₁ receptors in striatal synaptosomes with 100 nM N⁶-cyclopentyladenosine (CPA) inhibited both the release of endogenous glutamate and the increase of intracellular free Ca²⁺ concentration ([Ca²⁺]_i), due to 4-aminopyridine (4-AP) stimulation, by 28 and 19%, respectively. Furthermore, CPA enhanced the inhibition of endogenous glutamate release due to ω-conotoxin GVIA (ω-Cgtx GVIA), ω-Cgtx MVIIC or ω-Cgtx GVIA plus ω-Cgtx MVIIC. Similar effects were observed in the [Ca²⁺]_i signal. The inhibitory effects of CPA and ω-Cgtx GVIA were additive, but the effects of CPA and ω-Cgtx MVIIC were only partially additive. These results suggest that P/Q-type Ca²⁺ channels and other type(s) of Ca²⁺ channel(s), coupled to glutamate release, are inhibited subsequently to activation of adenosine A₁ receptors.     

Effect of uridine of presynaptic NMDA and kainate receptor of rat brain cortex

It was demonstrated that uridine affects presynaptic NMDA and kainite receptors of rat brain cortex. Uridine considerably inhibited ⁴⁵Ca²⁺ uptake into synaptoneurosomes (IC₅₀=7.1×10⁻¹² M) under conditions NMDA stimulation and increased it under conditions AMPA stimulation (157.8%). __________ Translated from Byulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 145, No. 3, pp. 288–290, March, 2008     

脑缺血再灌注后酪氨酸蛋白激酶和蛋白磷酸酶的活性变化及其机制(英文)

目的:研究脑缺血再灌注后沙土鼠海马突触体蛋白质酪氨酸激酶(PTK)和蛋白质酪氨酸磷酸酶(PTP)活性的变化及其引起变化的机制。方法:双侧颈总动脉结扎(15min)形成全脑缺血模型;放射性同位素γ-~(32)P掺入法和比色法分别测定了总PTK和PTP的活性,免疫沉淀和γ-~(32)P放射性同位素测定Src和PYK_2活性,免疫印渍测定Src和PYK_2蛋白表达量。结果:①脑缺血再灌注引起PTK活性升高,而PTP活性不变。②在假手术对照组中,Src比PYK_2活性高,脑缺血再灌引起Src活性明显升高,而PYK_2活性无显著变化。③脑缺血前腹腔分别给予氯胺酮和硝苯地平,都能拮抗脑缺血再灌注引起的PTK和Src活性的升高,但对PTP活性无影响。结论:脑缺血再灌注能诱导沙土鼠海马突触体总的PTK活性升高,而对PTP活性无影响,PTK活性的升高主要是Src活性的增加而与PYK_2无关;脑缺血再灌注诱导PTK和Src活性升高是通过NR和L-型电压门控钙通道介导的,即与这两种钙通道的激活有关,而与其蛋白表达量无关。     

神经生长因子改善衰老性记忆障碍及突触机制的探讨

目的　探讨神经生长因子(NGF)改善衰老性记忆障碍的机制。方法　采用开场行为和一次性被动回避反应模型,观察海马内微量注射NGF对衰老小鼠自发活动和记忆巩固过程的影响, 同时用Ca²⁺荧光探针Fura-2/AM和AR-CM-MIC阳离子测定系统测定海马突触体游离钙水平,以³H-Leu为标记物测定海马突触体总蛋白的合成量。结果　NGF使衰老小鼠在新异环境中的自发活动和探究行为明显增多,并显著延长电击后24 h的步入潜伏期(STL); NGF显著降低衰老小鼠海马突触体内的高钙水平,并使海马突触体蛋白质的³H-Leu参入量显著增加。结论　NGF改善衰老性记忆障碍与其降低海马突触体内高钙水平,并由此促进海马突触体蛋白质的合成有关。     

Effects of delta sleep-inducing peptide on pre-and postsynaptic glutamate and postsynaptic GABA receptors in neurons of the cortex, hippocampus, and cerebellum in rats

We studied the effect of delta sleep-inducing peptide on GABA receptors of hippocampal and cerebellar neurons in rats. It was shown that delta sleep-inducing peptide considerably and dose-dependently potentiates GABA-activated currents in these neurons and blocks NMDA-activated potentiation in cortical and hippocampal neurons. The peptide modulates activity of presynaptic NMDA receptors, which is seen from changes in ⁴⁵Ca²⁺ uptake into synaptosomes of the brain cortex after uptake stimulation with glutamate and NMDA. __________ Translated from Byulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 142, No. 8, pp. 149–151, August, 2006     

Inhibitory effect of dibutyryl cyclic GMP on potassium-stimulated 45Ca uptake by synaptosomes from rat brain

The effects of dibutyrl cyclic GMP (db-cGMP) and dibutyryl cyclic AMP (db-cAMP) on potassium-stimulated 45Ca uptake by the P2 fraction of Gray and Whittaker were investigated with the following results. (1) db-cGMP inhibited the initial rate of potassium-stimulated 45Ca-uptake in a dose-dependent manner in 0.1 mM Ca0 medium, but had no effect on the uptake in low K+ medium. In 0.1 mM Ca0 medium, the concentration of db-cGMP causing 50% inhibition was about 3 mM. db-cAMP (5 mM) had no effect on the uptake. (2) db-cGMP-inhibited potassium-stimulated 45Ca uptake in 1 mM Ca0 medium, though less than in 0.1 mM Ca0 medium. (3) db-cGMP inhibited potassium-stimulated 45Ca uptake by synaptosomes (pinched-off nerve terminals) more than the uptakes by other subfractions of P2 fraction. It is suggested from the results that cGMP inhibits the Ca influx resulting from depolarization of the nerve endings in situ.     

Effects of neonatal hypothyroidism on cerebral and cerebellar synaptosome development.

The effect of hypothyroidism on cerebral and cerebellar synaptosome development has been studied. Neonatal hypothyroidism was induced following addition of 0.3% propylthiouracil to the diet of nursing mothers. Maturation profiles of total synaptosome fraction and specific activities of lactate dehydrogenase, Na+K ATPase, cytochrome c oxidase, and protein were obtained from days 6 to 32 on synaptosomes isolated from Ficoll-sucrose gradients. The greatest changes were found in the total activities of enzymes isolated from the cerebellum. Hypothyroidism induced a retardation of LDH and cytochrome c oxidase in cerebellar synaptosomes, but no change in corresponding specific activities. Maximum rates of 14C-leucine incorporation into cerebellar synaptosome protein was found at 16-20 days, after which a rapid decline occurred to adult levels at 32 days. In neonatal hypothyroidism, synthesis was significantly reduced at 8 and 14 days, but reached control levels or above at 21--32 days. In the cerebrum, maximum rates of 14C-leucine incorporation into synaptosome protein were identified at 8--12 days in normal with a rapid drop to adult levels at approximately 20 days. In neonatal hypothyroidism, peak activities were identified at 14 days and increased activities over control were noted at 14, 20 and 30 days. These observations demonstrate the sensitivity of the developing cerebellar synaptic apparatus to neonatal hypothyroidism, with a protraction in the peak levels of synaptosome protein synthesis in cerebrum and cerebellum.