Region-specific mechanisms for testosterone-induced Fos in hamster brain.
Hamsters self-administer androgens. Previously, we determined that testosterone (T) activates select steroid- and opiate-sensitive brain regions. Is T-stimulated neuronal activation androgenic? Thirty-five castrated males with physiologic T replacement (n=7/group) were pre-treated with the androgen antagonist flutamide (15 mg/kg sc) or ethanol (0.25 ml) and infused into the lateral ventricle (ICV) for 4 h with 40 microg T (TF and TE, respectively) or 40 microl vehicle (VF and VE). To determine if androgens and opiates activate overlapping brain areas, 7 additional males received 20 mug morphine sulfate ICV following ethanol injection (ME). Immediately after ICV infusion, animals were perfused. Sixty-micrometer coronal brain slices were stained for Fos. Fos-positive neurons were counted in a 0.3-mm(2) area from 5 regions previously shown to express T-induced Fos: the posteromedial bed nucleus of the stria terminalis (BSTPM), posteromedial amygdala (MeP), lateral habenula (LHb), ventral tegmental area, and lateral pontine nucleus. T induced Fos in all areas reported previously (TE vs. VE, p<0.05), except LHb (p>0.05). Morphine induced Fos in all 5 brain regions (ME vs. VE, p<0.05), indicating that androgens and opiates activate overlapping brain regions. Flutamide alone did not induce Fos (VF vs. VE, p>0.05). Moreover, flutamide treatment blocked T-induced Fos expression only in the steroid-sensitive BSTPM, suggesting that androgens mediate neuronal activation in this area (mean+/-SEM: TF: 68.4+/-13.2 vs. TE: 137.9+/-17.6, p<0.05). The absence of flutamide effects on T-induced Fos in the steroid-sensitive MeP (TE: 210.6+/-50.0 vs. TF: 215.3+/-28.2, p>0.05) suggests that distinct mechanisms activate Fos in individual androgen-responsive nuclei.
Nagypál
Anita
A
Neuroscience Program, Department of Cell and Neurobiology, Keck School of Medicine of the University of Southern California, 1333 San Pablo St., BMT 401, Los Angeles, CA 90033, USA.
Wood
Ruth I
RI
D000704:Analysis of Variance; D000726:Androgen Antagonists / Q000008:administration & dosage; D000728:Androgens / Q000494:pharmacology*; D000818:Animals; D001921:Brain / Q000166:cytology / Q000187:drug effects*; D006224:Cricetinae; D004305:Dose-Response Relationship, Drug; D005485:Flutamide / Q000008:administration & dosage; D007276:Injections, Intraventricular / Q000379:methods; D008297:Male; D009020:Morphine / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism*; D013739:Testosterone / Q000494:pharmacology*
D000726:Androgen Antagonists; D000728:Androgens; D016760:Proto-Oncogene Proteins c-fos; D013739:Testosterone; D009020:Morphine; D005485:Flutamide