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: Enhanced endogenous neurotransmitter overflow in the isolated perfused rat kidney after chronic epinephrine administration: lack of a prejunctional beta adrenoceptor influence.
    Author: Schwartz DD, Eikenburg DC.
    Journal: J Pharmacol Exp Ther; 1988 Jan; 244(1):11-8. PubMed ID: 2891841.
    Abstract:
    This study examines stimulus-induced overflow of endogenous catecholamines from the isolated perfused kidney of rats after epinephrine (EPI) administration at 100 micrograms/kg/hr for 6 days via s.c. implanted osmotic minipumps. This regimen resulted in the incorporation of EPI into renal catecholamine stores and the co-release of EPI with norepinephrine during periarterial nerve stimulation. Stimulus-induced (1 Hz) absolute and fractional overflows of neurotransmitter were significantly greater in the EPI-treated rats. These differences in overflow were not altered by uptake blockade. Alpha adrenoceptor blockade with phentolamine (10(-9)-10(-5) alone increased overflow in a dose-dependent manner in both groups, although to a greater extent in the EPI-treated group. However, in the presence of 1 microM propranolol the effect of phentolamine in the EPI-treated group was greatly reduced such that, in the presence of propranolol, phentolamine was less effective in the EPI-treated vs. vehicle-treated rats. Beta adrenoceptor blockade alone with propranolol (10(-9)-10(-6) M) did not alter stimulus-induced overflow in either group but propranolol dose dependently reduced fractional overflow in the EPI-treated rats when the experiments were done in the presence of 10 microM phentolamine. It is concluded that the enhanced fractional overflow observed in the kidneys of EPI-treated rats was not due to beta adrenoceptor activation, but rather, a reduced influence of the prejunctional alpha adrenoceptor-mediated negative feedback loop. Beta adrenoceptor activation by neurally released EPI does not appear to modulate stimulus-induced overflow unless the dominant inhibitory alpha adrenoceptor mechanism is inactivated.(ABSTRACT TRUNCATED AT 250 WORDS)
    [Abstract] [Full Text] [Related] [New Search]