Analysis of brain adrenergic receptors in dopamine-beta-hydroxylase knockout mice.
The biosynthesis of norepinephrine occurs through a multi-enzymatic pathway that includes the enzyme dopamine-beta-hydroxylase (DBH). Mice with a homozygous deletion of DBH (Dbh-/-) have a selective and complete absence of norepinephrine. The purpose of this study was to assess the expression of alpha-1, alpha-2 and beta adrenergic receptors (alpha1-AR, alpha2-AR and beta-AR) in the postnatal absence of norepinephrine by comparing noradrenergic receptors in Dbh-/- mice with those in Dbh heterozygotes (Dbh+/-), which have normal levels of norepinephrine throughout life. The densities of alpha1-AR, alpha2-AR and beta-AR were assayed with [3H]prazosin, [3H]RX21002 and [125I]-iodo-pindolol autoradiography, respectively. The alpha2-AR agonist high affinity state was examined with [125I]-para-iodoclonidine autoradiography and alpha2-AR functionality by alpha2-AR agonist-stimulated [35S]GTPgammaS autoradiography. The density of alpha1-AR in Dbh-/- mice was similar to Dbh+/- mice in most brain regions, with an up-regulation in the hippocampus. Modest decreases in alpha2-AR were found in septum, hippocampus and amygdala, but these were not reflected in alpha2-AR functionality. The density of beta-AR was up-regulated to varying degrees in many brain regions of Dbh-/- mice compared to the heterozygotes. These findings indicate that regulation of noradrenergic receptors by endogenous norepinephrine depends on receptor type and neuroanatomical region.
Sanders
Jeff D
JD
Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE 68198-5800, and Veterans Administration Puget Sound Health Care System, Seattle, WA 98108, USA.
Szot
Patricia
P
Weinshenker
David
D
Happe
H Kevin
HK
Bylund
David B
DB
Murrin
L Charles
LC
D000704:Analysis of Variance; D000818:Animals; D000831:Animals, Newborn; D001345:Autoradiography / Q000379:methods; D001921:Brain / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D004299:Dopamine beta-Hydroxylase / Q000172:deficiency*; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects / Q000235:genetics; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D019329:Idazoxan / Q000031:analogs & derivatives / Q000378:metabolism; D007554:Isotopes / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010869:Pindolol / Q000378:metabolism; D011224:Prazosin / Q000378:metabolism; D018340:Receptors, Adrenergic, alpha-1 / Q000235:genetics / Q000378:metabolism*; D018341:Receptors, Adrenergic, alpha-2 / Q000235:genetics / Q000378:metabolism*
D007554:Isotopes; D018340:Receptors, Adrenergic, alpha-1; D018341:Receptors, Adrenergic, alpha-2; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D010869:Pindolol; C058525:2-methoxyidazoxan; D004299:Dopamine beta-Hydroxylase; D011224:Prazosin; D019329:Idazoxan