Regional variation in electrically‐evoked contractions of rabbit isolated pulmonary artery

Abstract

1 Electrically-evoked contractions in dierent regions of the rabbit isolated pulmonary artery have been investigated using stimulation parameters generally assumed to stimulate nerves selectively. 2 In extrapulmonary artery, trains of stimuli (10 Hz; pulse width 0.1 ms) evoked monophasic contractions. In contrast, a biphasic contraction was evoked in the intrapulmonary artery consisting of an initial fast component followed by a secondary very long-lasting component. 3 The contraction in the extrapulmonary artery was prazosin-sensitive (1 mM) whereas that in the intrapulmonary artery was prazosin-resistant. 4 a,b-Methylene ATP (1 mM), atropine (1 mM), losartan (1 mM), BIBO3304 (1 nM) or nifedipine (1 mM) had no eect on the biphasic contraction of the intrapulmonary artery. Bretylium (2 mM) abolished the contraction of extrapulmonary artery but only partially inhibited the initial component in the intra region with no eect on the second component. 5 Tetrodotoxin (0.3 ± 1 mM), abolished the contraction of extrapulmonary artery but only partially reduced the electrically-evoked contraction of intrapulmonary artery. 6 Removal of the endothelium and application of sulphisoxazole (0.6 ± 22 mM) had no eect. 7 Varying the resting tone on the arteries, or applying gadolinium, had no eect on contractions. 8 Using confocal microscopy and calcium imaging, reproducible whole cell calcium transients were evoked in individual smooth muscle cells in intact preparations but only when direct muscle stimulation was used (pulse width of 5 ± 10 ms). No detectable changes in calcium were elicited when brief pulse widths were used (0.1 ± 2 ms). 9 Together, these data suggest that noradrenaline is the neurotransmitter inducing contraction in extrapulmonary artery. Noradrenaline and sympathetic nerves appear to play a less important role in the intrapulmonary artery. The tetrodoxin-resistant component is not mediated by ATP, NPY, acetylcholine, angiotensins, ET-1, stretch-activation or Ca 2+ in¯ux through L-type Ca 2+ channels. Smooth muscle cells do not appear to be damaged by the stimulation protocol. The mechanism underlying the long lasting contraction of intrapulmonary artery evoked by brief electrical stimuli remains to be elucidated.

Non Thermal Irreversible Electroporation: Novel Technology for Vascular Smooth Muscle Cells Ablation

“…We do not have a definitive explanation for the conductance decrease observed here. We consider that a plausible hypothesis is that NTIRE pulses cause a contraction of the arteries by stimulating the vascular smooth muscle cells and that such a contraction results in an increase in the electrical impedance of the arteries [24]–[26]. Another explanation could be based on the fact that electroporation disturbs the osmotic balance of the cells and causes cell swelling which in turn can result in a decrease of the conductance [23].…”

“…We consider that a plausible hypothesis is that NTIRE pulses cause a contraction of the arteries by stimulating the vascular smooth muscle cells and that such a contraction results in an increase in the electrical impedance of the arteries. [24] – [26] Another explanation could be based on the fact that electroporation disturbs the osmotic balance of the cells and causes cell swelling which in turn can result in a decrease of the conductance. [23] Nevertheless, we believe that such swelling cannot be manifested as fast as would be required here in order to explain the conductance decrease during the sequence, particularly in Groups 1 and 2 (sequence duration = 1 second).…”

Caracterização farmacológica de artéria pulmonar de Callithrix jacchus

“…resposta contrátil de ambas as artérias(37). Em artéria pulmonar isolada de humano a ACh e o carbacol induziram contração em vasos sem endotélio e relaxamento em vasos com endotélio, enquanto que o inibidor da butirilcolinesterase, iso-OMPA potencializou a contração, mas não o relaxamento induzido pela ACh(38).…”