Noradrenergic transmission in the isolated portal vein of the spontaneously hypertensive rat.
The effect of electrical field stimulation (1, 2, 5, 10 Hz for a total of 480 pulses at 15-minute intervals) on the release of 3H-norepinephrine from the superfused portal vein of spontaneously hypertensive rats (SHR) or Wistar-Kyoto rats (WKY) of various ages was studied. The ages of the animals were (in weeks) 5-6 (prehypertensive), 8-10 (young hypertensives), 16-18 (older hypertensives), and 28 (mature hypertensives). There was no difference in the release of 3H-norepinephrine or developed tension of the portal vein to any frequency of field stimulation of SHR or WKY at 5-6 weeks of age. However, there was a significantly greater release of 3H-norepinephrine and developed tension of veins of SHR in response to low (1 or 2 Hz) but not high frequencies (5 or 10 Hz) at 8-10, 16-18, and 28 weeks of age. Vessels from hypertensive animals also developed greater resting tension and spontaneous activity, which was reduced to that of WKY in the presence of an alpha-adrenergic antagonist. The alpha 2 selective adrenergic antagonist yohimbine produced the same degree of enhancement of release of 3H-norepinephrine to field stimulation of veins obtained from both SHR and WKY at 5-6, 8-10 and 16-18 weeks of age. However, the facilitory effect of yohimbine was significantly attenuated in portal veins obtained from SHR at 28 weeks of age compared to age-matched WKY.(ABSTRACT TRUNCATED AT 250 WORDS)
D000367:Age Factors; D000809:Angiotensins / Q000494:pharmacology; D000818:Animals; D004558:Electric Stimulation; D006973:Hypertension / Q000378:metabolism / Q000503:physiopathology*; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects; D009638:Norepinephrine / Q000378:metabolism*; D011169:Portal Vein / Q000187:drug effects / Q000294:innervation* / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D017981:Receptors, Neurotransmitter / Q000187:drug effects; D013268:Stimulation, Chemical; D009435:Synaptic Transmission; D014316:Tritium; D015016:Yohimbine / Q000494:pharmacology
D000809:Angiotensins; D017981:Receptors, Neurotransmitter; D014316:Tritium; D015016:Yohimbine; D007545:Isoproterenol; D009638:Norepinephrine