[Comparison of the inhibitory effect of diltiazem on neurogenic contractions in the mesenteric arteries and veins]. / Porovnanie inhibicného úcinku diltiazemu na neurogénne kontrakcie mezenteriálnych artérií a vén.

The effect of diltiazem on the magnitude of isometric contractions induced by electric stimulation of intramural nerves (4Hz) was studied on isolated rings of the mesenteric artery and vein of the dog and rabbit. Diltiazem in concentrations of 10(-5) mol/l and above inhibited neurogenic contractions of the mesenteric artery and vein of the dog in a dose-dependent manner. Inhibition of contractions of the mesenteric vein was found to be more pronounced than that of contractions of the mesenteric artery. In the mesenteric vessels of the rabbit, diltiazem in concentrations of 10(-6) and above inhibited neurogenic contractions, and again more markedly in the veins than in the arteries. On comparing the inhibition of contractions in the two animal species studied, the contractions of the mesenteric vein of the rabbit were found to be more intensely inhibited than those of the dog vein. Diltiazem inhibited also phentolamine-resistant neurogenic contractions of the mesenteric artery. The established differences in the magnitude of neurogenic contraction inhibition may presumably be accounted for by quantitative differences in adrenergic innervation of mesenteric arteries and veins, as well as by differences in the magnitude of the contraction component dependent on extracellular calcium which is greater in the veins than in the arteries. This may also explain the more pronounced inhibition of neurogenic contractions in the veins compared to arteries.

[Relative volume of open capillaries in the skeletal muscles of rats with chronic local arterial hypotension]. / Otnositel'nyi ob"em otkrytykh kapilliarov v skeletnykh myshtsakh krysy pri khronicheskoi mestnoi arterial'noi gipotenzii.

A modification of Pickworth's method for detection of open capillaries was used. The modification is based on freezing an organ in situ with liquid propane, cooled with liquid nitrogen, followed by lyophilization of the preparation and its fixation in gaseous formaldehyde. It was shown in rat experiments that the number of functioning capillaries in m. gastrocnemius and m. soleus 14 and 90-12 days after reduction of pressure in the hindquarter of the body with the narrowing of the abdominal aorta lumen was practically the same as that in the control animals. The data support the view that reduction of the hydraulic resistance in the area of regional hypotension does not correlate with increase in the number of parallel-functioning vessels.