In connection with the known inhibitive action of bisphosphonates on bone resorption we were interested in their possible influence on bone blood flow (BBF). We determined BBF (^Sr-microsphere uptake in the tibia, distal femur and diaphysis of femur), cardiac output, density and ash weight of the tibia, as well as 24-h incorporation of 45Ca and 3H-proline into the tibia. Pamidronate (Aredia, CIBA-Geigy, Switzerland) was administered to sham- operated or oophorectomized (OOX) female rats in doses of 0.6 mg i.p. 2 days a week for 4 weeks. ^Sr- microsphere uptake was increased after OOX in the tibia and distal femur, simultaneous pamidronate administration significantly suppressed this increase below the control level. In addition, pamidronate inhibited the 24-h incorporation of 45Ca and 3H-proline in sham-operated females and suppressed the incorporation of 3H- proline that was increased after OOX. Bone density and ash weight were significantly increased after pamidronate administration in both sham-operated and OOX rats. The results of both experiments showing a significant effect of pamidronate on BBF and incorporation of 45Ca and 3H-proline require further verification and elucidation.
The action of phenytoin was studied in acute experiments in rats with brainstem transection at the midcollicular level. Symmetrical epileptogenic foci were elicited in sensorimotor cortical areas of both hemispheres by local application of penicillin. Seven rats formed a control group, ten animals were pretreated with phenytoin (60 mg/kg i.p., 10 min before penicillin application). Synchronization of interictal discharges in control rats was delayed in comparison to animals with an intact brainstem; phenytoin did not influence this synchronization. Spontaneous transition of interictal into ictal activity was not abolished by phenytoin, i.e. in cerveau isolé preparations phenytoin lost this activity. The loss of anticonvulsant activity was not complete. Ictal episodes were modified; they started as very short ones and their duration progressively increased. Structures localized below the level of transection represent a site of at least one of the mechanisms of phenytoin anticonvulsant action.
Reoxygenation following hypoxic episodes can increase the risk for the development of ventricular arrhythmias, which, in addition to circadian aspects of reoxygen ation arrhythmias has not been studied extensively. The aim of the present study was to evaluate circadian changes in the electrical stability of the rat heart during reoxygenation following a hypovent ilatory episode. The electrical stability of the heart, defined in the present study as the ventricular arrhythmia threshold (VAT), was measured at 3 h intervals at clock times 09:00, 12:00, 15:00, 18:00, 21:00, 24:00, 03:00, 06:00 and 09:00 during 20 min hypoventilation (20 breaths/min, tidal volume = 0.5 ml/100 g body weight [n=17]) and subsequent 20 min reoxygenation (50 breaths/min, tidal volume = 1 ml/100 g body weight [n=4]) intervals. The experiments were performed usin g pentobarbital-anesthetized (40 mg/kg intraperitoneally) female Wistar rats that first underwent a four-week adaptation to a 12 h light:12 h dark regimen. Detailed analysis show ed that circadian VATs changed to biphasic rhythms at 10 min of hypoventilation. The VAT circadian rhythms were observed immediately following the commencement of reoxygenation, with the highest values measured between 12:00 and 15: 00, and the lowest values between 24:00 and 03:00. These resu lts suggest that myocardial vulnerability is dependent on the light:dark cycle and characteristics of pu lmonary ventilation., P. Švorc ... [et al.]., and Obsahuje bibliografii a bibliografické odkazy
We have investigated the effect of a diet containing of 4 % oyster fungus (Pleurotus ostreatus) and 0.1 % cholesterol on glycaemia and hyperlipoproteinaemia in rats with insulin-dependent diabetes (streptozotocin 45 mg/kg). After two months, the rats with diabetes kept on the oyster fungus diet, had a significantly lower basal and postprandial glycaemia, the insulinaemia remained unchanged. The cholesterol concentration was decreased by more than 40 %, the lipoprotein profile was upgraded by the decrease of the cholesterol in both the low density and very low density lipoproteins. The oyster fungus decreased the cholesterol accumulation in the liver and had no significant effects on the levels of serum and liver triacylglycerols.
Two doses of alprazolam (0.1 and 0.5 mg.kg“1) were tested against a model of human absences - rhythmic EEG activity elicited by low doses of pentylenetetrazol (35 mg.kg-1) - in 10 unrestrained rats with implanted cortical electrodes. Alprazolam delayed the onset of epileptic EEG activity, decreased the number of rhythmic episodes and shortened the total duration of rhythmic activity in a dose-dependent manner. The average duration of episodes of rhythmic activity remained unchanged; other benzodiazepines studied previously were able to influence this measure.
A voltammetric technique was used (differential pulse voltammetry with a carbon fibre microelectrode) to investigate dynamics of the changes of catecholamine overflow in the corpus striatum following electroconvulsive stimulation (ECS) of chloral hydrate-anaesthetized rats. Application of "maximal" ECS (50 Hz, AC, sine wave, approximately 150 mA, 0.2 s) caused large enhancement of catechol-oxidative current (CA.OC): In the first minute after its arrest, the CA.OC peak raised to 1032±405% (n=5, mean±S.D.) of the controls (P<0.001, Student's t-test). This large elevation of the extracellular catecholamine content ceased rapidly - the baseline level was attained in the second minute. CA.OC changes evoked by a "minimal" ECS (50 Hz, AC, sine wave, approximately 30 mA, 0.2 s) were equivocal in the first minute (increase, decrease: 145 ±56 %, P>0.05, n=6). Possible mechanisms of the ECS therapeutic effect are discussed.
The effects of various doses of L-arginine, a nitric oxide substrate, on lithium-pilocarpine-induced seizures were studied in rats. Rats were implanted with chronic, stainless steel screw electrodes epidurally for electrocortical recordings. A control group received 3 mEq/kg LiCl (i.p.) and 24 h later 45 mg/kg pilocarpine HCl (i.p.). Two different experimental procedures were followed: (1) L-arginine was applied in doses of 100 mg/kg, 300 mg/kg or 500 mg/kg (i.p.), 30 min before pilocarpine injection; (2) 300 mg/kg, 500 mg/kg or 1000 mg/kg (i.p.) L-arginine was injected either 5 min or 30 min after the onset of status epilepticus (SE). L-arginine (300 mg/kg) injected 30 min before pilocarpine significantly reduced the percentage of SE, but did not change the latency to SE or 24-hour survival. These parameters were not significantly affected by the 100 mg/kg or 500 mg/kg dose of L-arginine. On the other hand, no dose of L-arginine that was applied after SE had begun, had any significant influence on the seizures. We concluded that L-arginine may prevent seizure activity in some but not all doses, and does not have any effect on the ongoing seizure activity., B. Noyan, G. Güleç., and Obsahuje bibliografii
After long-lasting administration of estradiol (4—6 weeks) in the presence or absence of pertussis toxin treatment we followed up the changes in body weight and adenohypophyseal weight in rats subjected to this treatment. The most striking effect was the potentiating effect of pertussis toxin on the estradiol-induced adenohypophyseal growth reaction. Adenylyl cyclase activity in the adenohypophysis was significantly increased in the estradiol- treated group and the addition of pertussis toxin did not further increase this enzyme activity. The lipolytic activity in adipose tissue exhibited a similar response as adenohypophyseal growth. Adrenergic lipolysis stimulated by pertussis toxin was highly significantly increased in tissues of rats treated with pertussis toxin. Our results show that the estrogen-induced adenohypophyseal growth reaction is highly potentiated by the treatment of rats with pertussis toxin and that this effect is in many aspects similar to that observed in adrenergic lipolysis. It thus seems that both processes might be mediated via a pertussis toxin-sensitive G protein which is involved in inhibitory regulation of adenylyl cyclase.
a1_In the present study, the effect of the medial septal (MS) lesions on exploratory activity in the open field and the spatial and object recognition memory has been investigated. This experiment compares three types of MS lesions: electrolytic lesions that destroy cells and fibers of passage, neurotoxic -ibotenic acid lesions that spare fibers of passage but predominantly affect the septal noncholinergic neurons, and immunotoxin - 192 IgG -saporin infusions that only eliminate cholinergic neurons. The main results are: the MS electrolytic lesioned rats were impaired in habituat ing to the environment in the repeated spatial environment, but rats with immuno - or neurotoxic lesions of the MS did not differ from control ones; the MS electrolytic and ibotenic acid lesioned rats showed an increase in their exploratory activity to the objects and were impaired in habituating to the objects in the repeated spatial environment; rats with immunolesions of the MS did not differ from control rats; electrolytic lesions of the MS disrupt spatial recognition memory; rats with immuno - or neurotoxic lesions of the MS were normal in detecting spatial novelty; all of the MS - lesioned and control rats clearly reacted to the object novelty by exploring the new object more than familiar ones. Results observed across lesion techniques indicate that: (i) the deficits after nonselective damage of MS are limited to a subset of cognitive processes dependent on the hippocampus, (ii) MS is substantial for spatial, but not for object recognition memory - the object recognition memory can be supported outside the septohippocampal system; (iii) the selective loss of septohippocampal cholinergic or noncholinergic projections does not disrupt the function of the hippocampus to a sufficient extent to impair spatial recognition memory;, a2_(iv) there is dissociation between the two major components (cholinergic and noncholinergic) of the septohippocampal pathway in exploratory behavior assessed in the open field - the memory exhibited by decrements in exploration of repeated object presentations is affected by either electr olytic or ibotenic lesions, but not saporin., M. G. Dashniani, M. A. Burjanadze, T. L. Naneishvili, N. C. Chkhikvishvili, G. V. Beselia, L. B. Kruashvili, N. O. Pochkhidze, M. R. Chighladze., and Obsahuje bibliografii
We present a custom-made multielectrode array for the recording of evoked potentials during acute experiments in rats, which offers a quick and reliable estimation of the cortical tonotopy. The array consists of electrodes represented by insulated copper wires of 0.09 mm diameter fixed in epoxy resin in a 3 x 5 arrangement, with final impedances of 410-800 kOhm. The array was placed on the brain surface of anesthetized rats approximately at the location of the auditory cortex (AC) and the cortical evoked potentials (middle-latency responses, MLR) were elicited by a series of tone pips of different frequencies at 50 dB of sound pressure level (SPL) intensity. The frequency that evoked the highest MLR amplitude (best frequency, BF) was identified for each electrode. The obtained distribution of the BFs characterized the cortical tonotopy, and it correlated with the frequency selectivity of neurons recorded at the same positions by an extracellular microelectrode. Although the space resolution of the array did not allow for the identification of AC sub regions, the array proved to be a reliable tool for a quick estimation and prediction of areas of interest for the subsequent measurements of neurons by more precise techniques.