Comparison of the frequency dependence of venous and arterial responses to sympathetic nerve stimulation in guinea-pigs.
1. Intracellular potentials and measurements of contractions were recorded in adjacent veins and arteries in the colonic mesentery of the guinea-pig in vitro during stimulation of post-ganglionic nerve trunks. 2. Repetitive stimulation (0.5-5 Hz) of lumbar colonic nerve trunks produced frequency-dependent slow depolarizations in all venous and in 92% of arterial smooth muscle cells. Excitatory junction potentials were observed for each nerve shock in arteries, but not in veins. 3. Low-frequency stimulations produced slow depolarizations of greater amplitude and longer duration in veins than in arteries. The frequencies at which half-maximal depolarizations and contractions occurred were always lower for veins than for arteries. 4. The alpha 1-adrenergic antagonist prazosin (5 X 10(-7) M) reduced the mean arterial slow depolarizations by 82% and reduced mean venous slow depolarizations by 58% for 5 Hz stimulations. Arterial contractions were completely inhibited by prazosin but venous contractions were incompletely reduced in a frequency-dependent manner. 5. These findings suggest that functional differences in activation between mesenteric veins and arteries during sympathetic stimulation are a result of differences in neuromuscular transmission.
Hottenstein
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Department of Pharmacology, College of Medicine, University of Arizona, Tucson 85724.
Kreulen
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D000818:Animals; D004558:Electric Stimulation; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D008638:Mesenteric Arteries / Q000502:physiology; D008642:Mesenteric Veins / Q000502:physiology; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000502:physiology*; D009469:Neuromuscular Junction / Q000502:physiology; D011224:Prazosin / Q000494:pharmacology; D013564:Sympathetic Nervous System / Q000502:physiology*; D009435:Synaptic Transmission / Q000187:drug effects
D011224:Prazosin