These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: Involvement of alpha 1- and alpha 2-adrenoceptors in the responses of proximal and distal segments of the canine saphenous vein to exogenous and endogenous noradrenaline.
    Author: Pereira O, Moura D, Nunes P, Vaz-da Silva MJ, Guimarães S.
    Journal: Naunyn Schmiedebergs Arch Pharmacol; 1991 Jun; 343(6):616-22. PubMed ID: 1658662.
    Abstract:
    In the present study the relationship between adrenergic nerve terminals and postjunctional alpha-adrenoceptors mediating the responses to the endogenous transmitter was compared at proximal and distal levels of the canine saphenous vein. Concentration-response curves to noradrenaline and to tyramine as well as frequency-response curves to electrical stimulation were compared at both levels of the vessel, in the absence and presence of either prazosin (100 nmol.l-1) or yohimbine (100 nmol.l-1). The influence of inhibition of neuronal uptake by cocaine (12 mumol.l-1) on the responses to noradrenaline in the presence of prazosin (56 nmol.l-1) or yohimbine (20 nmol.l-1) was compared at the proximal level. The results show that, at the proximal level, the maximal responses to electrical stimulation and tyramine reached 80.1 +/- 2.2 (n = 18) and 74.2 +/- 1.9 (n = 18)%, respectively, of the maximal responses to noradrenaline, and 70.3 +/- 0.8 (n = 15) and 53.1 +/- 1.2 (n = 14)%, respectively, at the distal level. Furthermore, the proximal strips were more sensitive to electrical stimulation than the distal ones. Prazosin had a much greater inhibitory effect on the contractile responses to noradrenaline than on those to electrical stimulation, at both levels. At proximal level, the shifts (to the right) of the concentration (frequency)-response curves (at EC50) amounted to 0.58 +/- 0.02 (n = 16) and 0.18 +/- 0.02 (n = 8) log units, respectively (P less than 0.05), but, at the distal level, to 1.12 +/- 0.03 (n = 16) and 0.28 +/- 0.08 (n = 8) log units, respectively (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)
    [Abstract] [Full Text] [Related] [New Search]