The concentrations of immunoreactive cortisol were monitored over 24 hours in the serum of a total of 23 dogs. The dogs were divided into three groups: (a) control group with no exercise, (b) experimental group, (c) working dogs. Blood was collected from each dog at the intervals of 90-180 min. The cortisol concentrations in different time periods were mutually compared using the Kruskal-Wallis test for the analysis of variance. Circadian pattern was found in the study. Cortisol concentrations found between 10.00 and 13.00 (46.5 ± 17.0 nmol/l) were significantly higher (P < 0.05) than those found between 19.00 and 22.00 (38.9 ± 16.0 nmol/l). The results differed within individual groups. Diurnal rhythms were confirmed in control group but not found in experimental group and in working dogs. In experimental group, other significant (P < 0.05) differences were also found between various time intervals compared to the total pattern but no diurnal rhythm was established. In working dogs no significant differences (P < 0.05) were found between cortisol concentrations in different time intervals. The results suggest that cortisol concentrations in the dog are subject to considerable changes during the day. Depending on the characteristics of day and night activities a diurnal rhythm can be found in some dogs.

No abstract

The aim of this study was in vivo testing of the action of three newly synthesized potential ultrashort acting beta-blockers on the heart rate in the laboratory rat. The tested substance 44Bu was administered to animals with induced tachycardia, in the form of an intravenous bolus in general anaesthesia.Doses at concentrations of 1.5 mg⋅kg -1 , 2.5 mg⋅kg -1 , and 3.5 mg⋅kg -1 of body mass were tested and the efficacy was compared with placebo. For the heart rate monitoring a computer electrocardiograph was used. Significant (p < 0.05) heart rate decrease was recorded for all three tested doses, minimally up to the 14 th minute following the intravenous administration.Bradycardic effect of the compound 44Bu was compared with the action of esmolol under the same experimental conditions. The effects of the compound 44Bu and esmolol were not different in the onset, but in the depth of the heart rate decrease, above all at higher concentrations. It was experimentally verified, that the compound 44Bu has the properties of an ultrashort acting beta adrenergic receptor blocker.Pharmacology, ester-functional group, bradycardic effect, heart rate, rats

Three newly synthesized potential ultrashort-acting beta adrenergic blockers containing metabolically unstable ester functional groups that are easily cleft by plasma esterases were tested. In the experiment, 30 laboratory rats divided into 4 subgroups were used. Agent 42Bu was administered to Group 1 (n = 8), agent 43Bu to Group 2 (n = 8), agent 44Bu to Group 3 (n = 8) and placebo to Group 4 (n = 6). Under general anesthesia the arteria carotis and vena jugularis were exteriorized. The arteria carotis was connected by a cannula to the machine HSE UNIPER UP -100, a universal perfusion system for isolated organs recording and converting actual values of blood pressure into graphical representation in a computer. Subsequently, 42Bu, 43Bu, 44Bu and placebo were administered into v. jugularis, and systolic blood pressure was recorded within the period of 18 minutes of their administration. All agents were administered at 2.5 mg/kg doses. The systolic blood pressure values after 42Bu, 43Bu, 44Bu administration were compared to those of the placebo Group. The 42Bu caused a statistically significant decrease (p < 0.05) in systolic blood pressure 1 minute after administration, 43Bu 1.5 minute after administration, and 44Bu 9 minutes thereafter. Statistically significant decrease of systolic blood pressure began immediately after administration of all three tested substances.The results of our in vivo testing show that agent 44Bu was the most effective of all three tested agents. Its onset of action was rapid and the hypothesis of ultrashort action was confirmed.Pharmacology, plasma esterases, ester functional group, universal perfusion system, hypotensive effect

The anti-arrhythmic effect was tested on the model of aconitine-induced arrhythmia. The experiment was performed in vivo with 31 male Wistar laboratory rats. Group A was first administered aconitine and, after the onset of the first sinus rhythm disorders, the 44Bu compound was administered. Group B was first administered the 44Bu compound and only after that the aconitine. The control group was administered aconitine and saline as a replacement of the tested compound. In group A, there was a decrease in the ventricular fibrillation occurrence from 100 % to 8 % (p < 0.001) after the administration of the 44Bu compound. In the B group, the onsets of all monitored arrhythmia types were delayed by an average of 15.6 min. Ventricular rhythm occurrence was decreased from 100 to 20 %, as well as ventricular fibrillations, from 100 to 0 % (p < 0.001).