Opposite changes in imidazoline I2 receptors and alpha2-adrenoceptors density in rat frontal cortex after induced gliosis.
Opposite age-dependent changes in alpha2-adrenoceptor and imidazoline I2 receptor (I2-IRs) density have been related to brain gliosis development with aging. To check this hypothesis we applied in rats a model of reactive gliosis induced by heat. The specific binding of [3H]idazoxan (0.5-20 nM) in the presence of (-)adrenaline (5 x 10(-6) M) to membranes from rat brain cortex showed that the density of I(2)-IRs was significantly higher in membranes of injured cortex (Bmax=60+/-6 fmol/mg protein; n=9) than in control (Bmax=38+/-3 fmol/mg protein; n=9; p=0.0053). Conversely, the density of alpha2-adrenoceptors, measured by [3H]clonidine (0.25-16 nM), in the injured cortex (Bmax=75+/-4 fmol/mg protein; n=9) was significantly lower than in sham membranes (Bmax=103+/-7 fmol/mg protein; n=9; p=0.0035). No significant differences in receptor's affinity were observed between both groups. These results support the hypothesis that gliosis induces opposite changes in alpha2-adrenoceptor and I2-IR density.
Martín-Gómez
J Ignacio
JI
Department of Pharmacology, University of the Basque Country, E-48940 Leioa, Bizkaia and E-01006 Vitoria-Gasteiz, Spain.
Ruiz
Javier
J
Barrondo
Sergio
S
Callado
Luis F
LF
Meana
J Javier
JJ
D000199:Actins / Q000378:metabolism; D000316:Adrenergic alpha-Agonists / Q000493:pharmacokinetics; D000317:Adrenergic alpha-Antagonists / Q000493:pharmacokinetics; D000818:Animals; D015153:Blotting, Western; D002462:Cell Membrane / Q000378:metabolism; D003000:Clonidine / Q000493:pharmacokinetics; D004837:Epinephrine / Q000493:pharmacokinetics; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D005911:Gliosis / Q000378:metabolism* / Q000473:pathology; D006358:Hot Temperature / Q000009:adverse effects; D019329:Idazoxan / Q000493:pharmacokinetics; D054755:Imidazoline Receptors; D008297:Male; D017397:Prefrontal Cortex / Q000378:metabolism* / Q000473:pathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D018341:Receptors, Adrenergic, alpha-2 / Q000378:metabolism*; D011955:Receptors, Drug / Q000378:metabolism*
D000199:Actins; D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists; D005904:Glial Fibrillary Acidic Protein; D054755:Imidazoline Receptors; D018341:Receptors, Adrenergic, alpha-2; D011955:Receptors, Drug; C487767:imidazoline receptor 2; D003000:Clonidine; D019329:Idazoxan; D004837:Epinephrine