The effect of anesthetics on cardiovascular reactivity to isoprenaline in rats]

Compared study was performed in rats under chloral or urethanne anaesthesia after venous infusion of isoproterenol. Cardiovascular haemodynamics and capillary regional blood flows of digestive tract showed changes; cardiac output was increased only under chloral anaesthesia; nutritional flows were different according to anaesthesia.     

Role of ventral surface of brain stem in control of arterial pressure and in hypotensive action of clonidine]

Superficial destructions of the brain stem have been performed in cats at the level of the chemosensitive areas "S". These destructions produced a drop in blood pressure, which was transient in 9 and definitive in 4 animals. In 6 sham-operated animals, clonidine (15 mug/kg), injected intravenously, always induced a marked fall in blood pressure, whereas in the 10 animals which have maintained or regained normal blood pressure after the destruction of the areas S, clonidine no longer induced any decrease in blood pressure. These results suggest that the integrity of the areas S is necessary for the development of the hypotensive action of clonidine. This hypotensive drug may act, at least at that level of the ventral surface of the brain stem, through an inhibition of a vasopressive structure.     

Effect of brain serotonin on the arterial pressure and plasma renin in normal and hypertensive rats]

The effects of changes in brain serotonin content after injections of p-chlorophenylalanine (p-CPA), L-5-hydroxytryptophan (L-5HTP) and 5-6-dihydroxytryptamine (5-6DHT) on the mean arterial pressure (MAP), plasma renin activity (PRA) and peripheral levels of atrial natriuretic peptide (ANP) have been studied in normal and hypertensive (2K:1C model) male Wistar rats. The p-CPA (250 mg/kg) and L-5HTP (200 mg/kg) were injected i.p., while 5-6 DHT (15 micrograms/animal in 10 mu/animal vehicle) was injected into lateral brain ventricles. The effects were studied 24 h after the p-CPA injection, 2 h after L-5HTP and 10 or 20 days after 5-6DHT administration. The fall in brain serotonin produced by p-CPA and 5-6DHT did not modify the MAP values in the normal and hypertensive rat model, whereas the increase induced after L-5HTP injection only caused a slight decrease in arterial pressure in normotensive animals. The ARP experimented remarkable rises in the normal and hypertensive rats, these values increasing after L-5HTP and falling after p-CPA and 5-6 DHT injections. Similar changes are detected in the normal group after administration of these substances related to serotoninergic brain activity. The ANP levels rose after renal artery constriction, and they are not affected by the above mentioned substances. Only p-CPA and 5-6DHT reduced a low decrease in the ANP levels 10 days after their administration.(ABSTRACT TRUNCATED AT 250 WORDS)     

Age-related differences in the effect of osmotic pressure on liver mitochondrial respiration in rats]

The subject under investigation is the influence of osmotic pressure of incubation medium (25-500 mM of sucrose) upon the respiration and the respiration control (RC) of mitochondria of the liver of rats aged 1, 3, 12 and 24 months when oxidizing succinate. In a medium with 0.3 M of sucrose the respiration rate under condition 3 (V3) and RC increased from the age of 1 to 12 months and decreased by 24 months. In a medium with 0.15 M of sucrose the age differences have not been observed. In a uncoupling state the osmotic dependence of the respiration of mitochondria of 1- and 12-month-old rats did not vary. It is assumed that with age there is a change in the rate of structural coupling of the carrier of adenine nucleotides with H(+)-ATP synthetase complex and (or) the viscosity of the matrix.     

Opposing effects of anesthetics on pressure tolerance and compression rate effect

Inert gas narcotics increase intrinsic pressure tolerance (1,000Pc) in CD-1 mice but interfere with development of the protective responses raising seizure thresholds during slower compression (e.g., 60Pc). This secondary narcotic effect can block up to 40% of the total attainable increase in Pc. The narcosis susceptible moiety of this compression rate effect develops early, whereas a narcosis resistant remnant accounts for increase in Pc occurring after 90 min of compression or pressure exposure. Pressure conditioning by multiday pressure exposure entails increases in both 60Pc and 1,000Pc and in virtual annullment of the compression rate effect. The effect can be completely blocked by narcotic gases in the conditioning atmosphere. In addition to blocking part of the compression rate effect the presence of narcotic gases under these conditions can reverse the effects of previously established pressure conditioning. 60Pc regresses much more slowly under these conditions than 1,000Pc. Either reversal rate is much more rapid in air at 1 ATA than at 80 ATA under 0.9 atm N2O. The implications of these data are discussed with regard to evaluation of the hypothesis of antagonism between inert gas narcotics and high pressures and to elaboration of the monoamine hypothesis to account for the modification of the compression rate effect by narcotic gases.     

Brain stem control of arterial pressure in chronic arterial baroreceptor-denervated rats

Interruption of the baroreceptor reflex by transection of afferent nerves (sinoaortic denervation; SAD) or lesions of nucleus tractus solitarius (NTS) elevates sympathetic nerve activity (SNA) and arterial pressure (AP). However, within 1 wk, mean AP returns to normal despite the absence of baroreflexes. In this study, we examine central mechanisms that control AP in chronic baroreceptor-denervated rats. In urethane-anesthetized rats (1.5 g/kg i.v.) after autonomic ganglionic blockade (5 mg/kg i.v. chlorisondamine), alpha1-adrenergic-mediated pressor responses (1-100 microg/kg i.v. phenylephrine) were not altered by chronic lesions of NTS, indicating vascular reactivity to sympathetic stimulation is normal. Transection of the spinal cord at T1 profoundly decreased AP and was not further reduced by chlorisondamine in control or denervated rats. Inhibition of the rostral ventrolateral medulla (RVLM) by microinjections of muscimol (100 pmol/side) decreased AP to levels not further reduced by chlorisondamine in control rats, rats with SAD, and rats with NTS lesions. Blockade of GABA(A) receptors in the RVLM (50 pmol/side bicuculline) increased AP similarly in control rats and denervated rats. In agreement, inhibition of the caudal ventrolateral medulla (CVLM) by microinjections of muscimol or blockade of glutamatergic inputs (2.7 nmol/side kynurenate) produced comparable increases in AP in control and denervated rats. These data suggest the RVLM continues to drive the SNA that regulates AP in the chronic absence of baroreceptor inputs. In addition, despite the absence of a tonic excitatory input from NTS, in chronic baroreceptor-denervated rats glutamatergic inputs drive the CVLM to tonically inhibit the RVLM. Baroreceptor-independent regulation of the ventrolateral medulla may underlie central mechanisms contributing to the long-term control of AP.     

The weak neurotoxin from Naja kaouthia Cobra venom decreases the arterial blood pressure in rats]

The weak neurotoxin from the Naja kaouthia cobra venom was found to reduce, under the intravenous administration to rats, the arterial blood pressure and increase the heart rate.     

Analysis of polymorphic DNA markers cosegregation with arterial blood pressure in ISIAH hypertensive rats]

A search for DNA markers of hereditary arterial hypertension in ISIAH rats was performed by means of contemporary molecular genetic approaches. The backcross rat population used for the analyses was derived from a cross of the Wistar x ISIAH F1 progeny with the Wistar rats. Hybridization of the HaeIII-digested DNA samples with the (CAC)5 microsatellite probe revealed cosegregation of the basal arterial pressure value with the 4.8-kb polymorphic DNA fragment. Examination of the DNA polymorphism by means of polymerase chain reaction with arbitrary primers showed an association of the 700-bp polymorphic DNA fragment with the increase of arterial blood pressure under conditions of emotional stress.     

Respiration of an obligate methylotroph in the presence of various substrates]

Respiration of the cells of Methylococcus ucrainicus, strain 21, cultivated in the atmosphere of methane, is stimulated by methanol, formaldehyde, formate, n-alcohols, and allyl alcohol. The rate of oxygen assimilation is lower in the presence of isopropanol, isobutanol, propane, butane, maltose, and some organic acids (acetate, fumarate, citrate, succinate). The Michaelis constant for methanol is 88 mcM. Oxidation of methane, methanol, formaldehyde, and formate by the bacterium is inhibited by cyanide, hydroxylamine, and azide. The rate of oxygen assimilation by the cells in the presence of methane and other C1-compounds did not decrease after the suspension had been stored at 4 degrees C during four months and longer.