Effect of NMDA-induced lesion of the subfornical organ on the angiotensin II binding sites density and acetylcholinesterase or NADPH-diphorase activities in the lamina terminalis of the rat brain
Ss. Guilhaume et Fma. Correa, Effect of NMDA-induced lesion of the subfornical organ on the angiotensin II binding sites density and acetylcholinesterase or NADPH-diphorase activities in the lamina terminalis of the rat brain, CELL MOL N, 21(1), 2001, pp. 81-90
1. Neural angiotensinergic circuitry located in the lamina terminalis has b
een proposed to be involved in blood pressure regulation and fluid homeosta
sis.
2. ANG LI binding sites have been described to be localized throughout the
lamina terminalis including the subfornical organ (SFO), the median preopti
c nucleus (MnPO), and the organum vasculosum lamina terminalis (OVLT).
3. The present experiment was designed to investigate the ANG II binding si
tes localization in the lamina terminalis. For this purpose, we have compar
ed the ANG II binding sites, acetylcholinesterase, and NADPH-diaphorase dis
tributions throughout the lamina terminalis. Additionally, we have studied
the effect of the preferential lesion of SFO neuronal cell bodies by local
injection of NMDA on the ANG II binding sites density in different areas of
the lamina terminalis.
4. Male Wistar rats were anesthetized, immobilized in a stereotaxic apparat
us, and 500 nl of saline or 250 nmol NMDA. was injected into the SFO.
5. Animals were sacrificed 1 week later, the brain was removed, frozen, and
sagittal 16 mum slices were cut in a cryostat. Alternate brain slices were
incubated with [I-125]- Sar(1)-ANG II for receptor autoradiography or hist
ochemically stained for Visualization of acetylcholinesterase and NADPH-dia
phorase activities. Binding capacity was determined by computerized quantit
ative densitometry of autoradiograms. The intensity of histochemical reacti
ons was measured as relative units obtained by computerized densitometry pr
ocessing of the brain slices stained for either activity.
6. Acetylcholinesterase staining was mainly located in the SFO, with faint
staining reaction in other areas of the lamina terminalis. NADPH-diaphorase
staining was homogeneously distributed throughout the lamina terminalis. A
significant positive correlation was observed between acetylcholinesterase
and NADPH-diaphorase stainings in the SFO of control and NMDA-lesioned rat
s.
7. ANG II binding sites were localized throughout the lamina terminalis. A
significant positive correlation was observed between the density of ANG II
binding sites and the intensity of acetylcholinesterase or NADPH-diaphoras
e staining in the SFO of control and NMDA-lesioned rats.
8. The distribution of the NADPH-diaphorase staining was found to closely m
atch the distribution of the ANG II binding sites in the lamina terminalis.
9. Neuronal lesion of the SFO caused significant reductions in the density
of ANG II biding sites in the SFO (-68%) and the MnPO (-48%). No changes we
re observed either in the OVLT or outside the lamina terminalis in the supe
rior colliculus.
10. The present results indicate the following: first, the presence of high
levels of acetylcholinesterase staining in the SFO and of NADPH-diaphorase
throughout the lamina terminalis; second, that ANG II binding sites in the
SFO and possibly in the MnPO are localized in neuronal cell bodies; third,
that SFO lesion did not affect the expression of ANG II binding sites in t
he OVLT thus suggesting that these binding sites correspond to different an
giotensinergic system; and finally, the existence of a striking correlation
between the distribution of the ANG II binding sites and NADPH-diaphorase
throughout the lamina terminalis, thus suggesting a interrelation between a
ngiotensinergic and nitrergic systems in the lamina terminalis.