[Chronic treatment with GABA A receptor blockers increases efficacy of GABAergic synaptic transmission in rat hippocampal neuron cultures]. / Zbil'shennia efektyvnosti GAMKerhichnoï synaptychnoï peredachi pislia tryvaloï blokady GAMK A-retseptoriv u kul'turi neironiv hipokampa shchura.

It has been proposed to consider plasticity in neuronal network as occurring in two forms: use-dependent plasticity which modifies the network properties, and homeostatic plasticity which may counteract use-dependent changes. Chronic block of some of transmitter receptors is often used as a model for studying homeostatic plasticity. We studied whether chronic block of GABAA receptors can affect GABAergic transmission. Using whole-cell voltage clamp recording and local extracellular stimulation we investigated evoked inhibitory postsynaptic currents (IPSCs) in cultured rat hippocampal neurons grown in the presence of GABAA receptor antagonist--bicuculline (20mM) and in control conditions. Cell for both control and pretreated cultures were obtained from same dissection and were grown in parallel. We compared the amplitudes of the evoked IPSC, the reversal potentials of the responses IPSC coefficient of variation and depression evoked by paired stimulation. Chronic bicuculline treatment did not significantly affect the paired-pulse depression (PPD) and IPSC reversal potentials. In contrast we found that amplitude of evoked IPSCs was increased about two times in cultures treated with bicuculline. However, IPSC coefficients of variation were not significantly different. We conclude that chronic block of GABAA receptors enhances efficacy of GABAergic synaptic transmission in rat hippocampal cell cultures and this effect is likely to postsynaptic mechanism(s) because IPSC increase was not accompanied with changes of IPSC coefficient of variation. A possibility that the effect of chronic block of GABAA receptors on GABAergic transmission is mediated by neurotrophin BDNF is discussed.

[Effect of synaptic transmission blockade and hypoglycemia on neuron impulse activity in cultured rat hippocampal neurons]. / Vplyv blokady synaptychnoï peredachi ta hipohlikemiï na impul'snu neironnu aktyvnist' u kul'turi neironiv hipokampa shchura.

Spontaneous neuronal activity was studied in rat hippocampal cell cultures using patch clamp technique in cell-attached or loose-patch configuration. It was found that in spite of relatively low average frequency (1-2 Hz) of neuronal activity in the cell cultures, neurons often fire doublets or triplets of action potentials with interspike interval of 60 ms and less. Interspike interval histograms were substantially better fitted by double exponential decay functions than by single exponential ones. On average, estimated decay time constant for the fits were tau1 approximately 36, ms and tau2 approximately 1000 ms respectively. Spontaneous neuronal firing to a large extent depended on glutamatergic excitation and GABA(A)ergic inhibition: a blocker of AMPA/kainate receptor CNQX (10 microM) either substantially decreased or completely blocked spontaneous action potentials; a blocker of GABA(A) receptors bicuculine (10 microM) increased neuronal firing. Effect of glucose deprivation on action potential frequency was also studied. It was found that glucose deprivation reduces AP frequency to 25% of control. Taken together, these results support an idea that hypoglycaemia alters synaptic transmission in hippocampus.

[Properties and expression of the human activated alpha2-macroglobulin receptor]. / Izuchenie svoistv i vyiavlenie ékspressii retseptora aktivirovannogo al'fa2-makroglobulina cheloveka.

A multi-step purification procedure has been used for isolation of alpha 2M/LRP receptor from human placenta. Enzymatic properties of complexes of purified alpha 2M trypsin with alpha 2M/LRP receptor were studied. This complex is characterized by enzymatic activity measured by a kinetic procedure based on the trypsin reaction with synthetic substrate alpha 2N-benzoyl-D,L-arginine nitroparaanilide. Purified triple complexes of alpha 2M trypsin with alpha 2M/LRP had 22-28% residual trypsin activity, while that of trypsin complex with alpha 2-macroglobulin was 52-53%. Patients' blood samples were characterized by a high level of residual activity of the studied double and triple complexes only initially. A decrease in the activities of these complexes was observed in patients with high levels of malonic dialdehyde (by TBA-reactive products) combined with decreased level of superoxidedismutase-like activity.