Role of the GABA-ergic link in the development of the tranquilizing effect in cats

The development of the tranquilizing effect of n-dipropylacetate (n-DPA) selectively increasing the GABA level in the nerve terminals was studied in experiments on cats in comparison with diazepam effect. The changes in the spectrum of emotional-behavioral reactivity were estimated. In doses of 50 and 200 mg/kg n-DPA caused a marked antiphobic effect which was not accompanied by the activating component characteristic of diazepam. The n-DPA-induced increase in the GABA level in the nerve terminals is suggested to be important for the development of the anxiolytic effect of tranquilizers. The total increase in the GABA level in the nerve terminals is suggested to be important for the development of the anxiolytic effect of tranquilizers. The total increase in the GABA content in the brain correlates to a greater extent with the sedative effect of drugs.     

Effect of GABA-ergic substances on the analgesic effect of morphine in rats]

The effect of GABA-ergic compounds on morphine-induced analgesia was studied to reveal probable interaction of GABA and opiates. As an index for morphine effect the reaction of vocalization in response to electrical stimulation of the rat tail was used. It was shown that thiosemicarbazide, the inhibitor of glutamate decarboxylase and bicuculline, GABA-ergic receptor blocking agent, which were proposed to be joined in a group of GABA-negative compounds, reduce and shorten the effect of morphine. Depakine, the inhibitor of alpha-ketoglutarate-GABA-transaminase, as well as GABA itself administered in high doses (GABA-positive actions) make morphine analgesia more pronounced and longer. Probable causes of the described interrelationship between GABA and opiates are discussed.     

GABA-ergic system in brain regions of glutamate-lesioned rats

Subcutaneous administration of high doses of glutamate to rats during their first 10 days after birth produced a great reduction of GABA content and GAD activity in the adult mediobasal hypothalamus, both in male and female. In addition GABA content and GAD activity showed a slight significant decrease in female cerebellum and male striatum. Glutamate treatment was also followed by a significant increase in GABA content and GAD activity of male substantia nigra, cerebellum, hippocampus and of female olfactory bulb. No reduction in GABA-T activity was observed in different brain areas studied except in mediobasal hypothalamus. The results support the view that glutamate treatment had a direct toxic effect on GABA-ergic neurons in mediobasal hypothalamus. The changes in GAD activity observed in all areas studied may reflect the neuroendocrine changes determined by nucleus arcuate lesions.     

Mechanism of the effect of diazepam on acetylcholine concentration in mouse brain

Intraperitoneal injection of diazepam (20 mg/kg) caused an increase of free and bound acetylcholine in the mouse brain. Diazepam pretreatment (20 mg/kg) increased galanthamine anticholinesterase activity and its toxicity; as to physostigmine, armine, and paraoxon toxicity--it remained unchanged. It is supposed that diazepam blocks the release of aetylcholine from the cholinergic nerve terminals which should result in a decrease of functional acetylcholine concentrations in the synapse.     

Increased specific binding of [3H]diazepam in rat brain following chronic diazepam administration.

Male rats (175 g) were given 30 mg of diazepam in their food daily for 35 days. The animals became drowsy and ataxic from this high dose of drug. After the 35-day dosing, the rats were killed daily, and specific binding of [3H]diazepam and [3H]flunitrazepam was determined in synaptosomal preparations from these and corresponding control rats. On days 3, 4, 6, and 7 after the treatment period the specific binding and specific binding of [3H]diazepam was double that of the control binding and specific binding of [3H]flunitrazepam was 1.67 times that of control. The data indicate that very high doses of diazepam, given for long periods, cause increased specific binding of radiolabeled ligand to brain subfractions. The possible mechanisms and implications are discussed. When lower doses or shorter dosage regimens are used, increased binding is not observed.     

Neuropharmacologic analysis of the dopamin-, cholin- and GABA-ergic systems of the brain in the organization of reflexes to time

Neurochemical mechanisms and structural-functional relations of conditioned reflex to time, temporal prognosing, and trace processes were studied in freely behaving intact cats and cats with lesions of the frontal cortex and the head of the caudate nucleus. It has been found that reactions to time are controlled mainly by cholinergic brain structures, temporal prognosing is controlled by dopaminergic mediation, and the trace phenomena--by GABA-ergic system. The data obtained and the methods applied may be used in analysis of some psychopathological symptoms such as desorientation in time, confabulatory confusion, mnestic disorders.     

Norharman inhibition of [3H]diazepam binding in mouse brain

Norharman competitively inhibits specific binding of [³H]-diazepam in mouse brain homogenates. $\text{In vivo}$ this β-carboline produces a striking rigid catatonic-like appearance which is abolished by diazepam. It also causes a rapid tremor but has little anticonvulsant effect. Measurement of $\text{in vivo}$ concentrations and receptor occupancy demonstrate that these biological effects occur at doses which occupy a large proportion of benzo-diazepine receptors. It may represent a ligand of the benzo-diazepine receptors whose effects are opposite those of diazepam.     

Role of monoaminergic systems in the development of the effect of stimulation of acetylcholinergic brain structures in the cat

The influence of systemic injection of anticholinesterase substance physostigmine on the behaviour of cats was studied under the conditions of pharmacological stimulation of monoaminergic cerebral systems. Development of the effect of the substance with an increase of its dose was accompanied by a successive alternation of three phases each representing an independent form of behaviour. Each form of behaviour originating in the process of acetylcholinergic stimulation increase was supposed to be caused by an involvement of corresponding monoaminergic system: serotonindopamine-, or noradrenergic one.     

Interaction of the serotoninergic and GABA-ergic systems in "psychogenic" amnesia

The results are analyzed of the influence of blockade of separate components of BD-GABA-iontophoretic complex on activation of memory-trace amnesia under blockade of serotonine PGA synthesis in experiments with conditioned reaction (CR) of passive avoidance in mice. It has been shown that the blockade of serotonine PGA synthesis did not change the behavioral manifestations of amnesia at all terms of testing. The blockade of chlorine channel by picrotoxin and of BD receptors RO15-1788 and RO15-3505 restored the reproduction of the memory trace disturbed against the PGA background; the blockade of GABAA-receptors by bicuculline lost its effectiveness. Activation of serotonin system by sertraline against the PGA background before learning and amnestic influence or before testing of CR of passive avoidance contributed to restoration of CR activating action of bicuculline. It was found that preliminary blockade of PGA serotonine synthesis changed the amnesia development and the character of subsequent restoration of CR of passive avoidance reproduction by blockaders of separate components of BD-GABA-iontophoretic complex.     

Calcium alters the properties of [3H]diazepam binding sites in rat brain membranes

• 1.1. [³H]diazepam ([³H]DZ) was used as a ligand to study the effects of Ca²⁺ on benzodiazepine binding to rat brain membranes.
• 2.2. [³H]DZ bound at a single class of binding sites showing K_D and B_max values of 5.4 nM and 852 fmol/mg protein respectively. These values are consistent with previous reports.
• 3.3. Amongst the various divalent cations tested Mg²⁺, Fe²⁺, Cd²⁺, and Sr²⁺ had no significant effect on [³H]DZ binding. Mn²⁺, Ba²⁺, Co²⁺, Ni²⁺ and La²⁺ enhanced radioligand binding, whereas Ca²⁺, Zn²⁺ and Pb²⁺ inhibited [³H]DZ binding to brain freeze-thawed membranes.
• 4.4. The inhibition of [³H]DZ binding by Ca²⁺ was concentration-dependent. 50% inhibition occurred at a Ca²⁺ concentration of 5.6mM. The Hill coefficient for the inhibition was 1.03, displaying noncoperativity. The effect of Ca²⁺ on [³H]DZ binding could be prevented by La³⁺ but was not reversed by EGTA.
• 5.5. A kinetic analysis of Ca²⁺ inhibition of [³H]DZ binding indicates that Ca²⁺ inhibited competitively. Analysis of binding isotherms indicates that both K_D and B_max were altered at the [³H]DZ binding sites. The marked increase in K_D value in the presence of Ca²⁺ (5 mM) can be explained by a drastic increase in the dissociation rate constant.
• 6.6. It was suggested that Ca²⁺ may induce a conformational change in the diazepam binding sites on rat brain membranes. The unchanged Hill coefficient in the presence or absence of Ca²⁺ indicates that a single population of binding sites was labeled by [³H]DZ.
• 7.7. The calmodulin antagonists, trifluoperazine and W-7 were weak inhibitors of [³h]dz binding.

     

The effect of different activating influences on the self stimulation reaction]

A study was made of the influence on self-stimulation of non-painful sensory stimuli of different modalities, and of intra-brain stimulations of emotionally positive and neutral points with the wiew to elucidate the specificity of certain functional relations appearing during interaction between emotionally negative and positive conditions. The data obtained attest that the influence of various excitation sites on self-stimulation reactions depends not so much on the strength of the stimuli, as on the specific neurophysiological organization of emotionally negative zones in the brain. A reciprocal enhancement of excitation of self-stimulation zones points to a certain non-specificity of positively reinforced structures.     

The effect of diazepam on adenosine uptake and adenosine-stimulated adenylate cyclase in guinea-pig brain

We have used the adenosine-stimulated adenylate cyclase of guinea-pig brain to examine the potency of diazepam as an adenosine uptake inhibitor. Diazepam at concentrations in the range 10--500 microM stimulates the production of cAMP in incubated slices of guinea-pig cerebral cortex, with maximal fivefold stimulations over basal levels by 200 microM diazepam. The increases can be largely (but not completely) blocked by the adenosine antagonist theophylline or by addition of excess adenosine deaminase to the system. It appears that the stimulation of cAMP production is due to a blockade of adenosine uptake which results in an increase in extracellular adenosine and concomitant activation of the adenosine receptor coupled to adenylate cyclase. Since the cAMP response to standard adenosine uptake blockers (dipyridamole, dilazep) can be completely blocked by theophylline or adenosine deaminase, a small component of the diazepam response cannot be explained by an adenosine effect. The concentration of diazepam at which the first significant cAMP increase occurs is 10 microM or slightly lower. This is significantly higher than the concentration of diazepam needed to saturate the pharmacologically characterized central nervous system receptors for benzodiazepines.     

The disinhibitory influence of the activating system when artificially excited from different points in the brain]

EEG activation can be produced by electrical stimulation of some cortical points with the same threshold current strength as by the midbrain RF and thalamic CM stimulation. Near-threshold stimulation of all these points acting simultaneously with inhibitory conditioned signals does not disturb the effector inhibition but displays an EEG difference between negative signals: the fine differentiation sound evokes considerable EEG desynchronization, while the rough one does not change the background rhythms. The same stimulation combined with a positive signal which has been made ineffective by successive inhibition or extinction, reestablishes the intensive EEG activation in response to this signal and the effector conditioned reflex. Therefore a mode-rate additional stimulation of the activating points in the cortex, RF and CM has a disinhibitory influence. When initiated in the cortex this influence may be transmitted from the cortical point to other parts of the brain along transcortical and corticofugal connections.     

Tranquilizing effect of n-dipropylacetate and other GABA-ergic substances in conflict situations

Effect of n-dipropyl acetate (n-DPA), amino oxyacetic acid (AOAA), pantogam and piracetam on rat behaviour was studied under conflict situation. n-DPA, AOAA and piracetam increased significantly the main index of the tranquilizing action, that is the number of water intakes from the drinking bowl, supported by electric stimulation. This effect was most pronounced in n-DPA. Bicuculline and corasol almost completely eliminated the tranquilizing effect of n-DPA, while this effect was abolished by caffeine only by 50%.     

Bupivacaine kinetics in serum, cardiac and brain tissues: effect of diazepam pretreatment in mice

This study was designed to document possible changes in bupivacaine kinetics in serum and in heart and brain tissues induced by a pretreatment with diazepam in mice. When diazepam is associated with bupivacaine, elimination of bupivacaine from serum and cardiac tissues is decreased; statistical differences were not found in brain tissues.     

Role of low-molecular weight factors isolated from Methanobacillus kuzneceovii in the activating effect of visible light on methane formation and reduction of pyridine nucleotides]

Four low molecular weight fluorescent factors are isolated from thermophylic methaneproducing facteria Methanobacterium kuzneceovii. These factors are: the factor 340; the factor 420 (both reduced and oxidized); and a flavine derivative, comprising together with proteins a biochemical system, which reduces pyridine nucleotides in dark (at 55degrees C) and in the light (at 21degrees C).     

Action of a UHF field on GABA-ergic and acetylcholinergic systems in synaptic transmission

It was shown that exposure of rats to microwaves (800 MHz, 16 Hz modulation, 1-3 mW/cm2) decreased muscimol binding with synaptic membranes and reduced acetycholinesterase activity in the rat brain.