TOPOGRAPHICAL RELATIONSHIP BETWEEN NEURONAL NITRIC-OXIDE SYNTHASE IMMUNOREACTIVITY AND CYCLIC 3',5'-GUANOSINE MONOPHOSPHATE ACCUMULATION INTHE BRAIN OF THE ADULT XENOPUS-LAEVIS
W. Allaerts et al., TOPOGRAPHICAL RELATIONSHIP BETWEEN NEURONAL NITRIC-OXIDE SYNTHASE IMMUNOREACTIVITY AND CYCLIC 3',5'-GUANOSINE MONOPHOSPHATE ACCUMULATION INTHE BRAIN OF THE ADULT XENOPUS-LAEVIS, Journal of chemical neuroanatomy, 15(1), 1998, pp. 41-56
Previous immunohistochemical staining procedures of the brain and pitu
itary in Xenopus laevis, using an antiserum against neuronal nitric ox
ide (NO) synthase (nNOS) and nicotinamide adenine dinucleotide phospha
te-diaphorase histochemistry, have revealed NOS activity in neurons an
d fibers in a number of brain areas, as well as in fibers in the pitui
tary. In the present study we have localized the target structures of
the NOergic system in the Xenopus brain by visualizing the sites of NO
-sensitive cyclic 3',5'-guanosine monophosphate (cGMP) accumulation, a
ccording to a method for cGMP visualization in rat brain slices. Brain
slices of unfixed Xenopus are incubated in the presence of the phosph
odiesterase inhibitor isobutylmethylxanthine and the NO donor sodium n
itroprusside, followed by fixation and cryosectioning. Sections were t
hen processed for immunohistochemistry using rabbit and sheep antisera
against cGMP and a sheep antiserum against nNOS. Visualization of sin
gle and double labeling of cGMP immunoreactive and/or nNOS immunoreact
ive structures was performed with combined CY3/fluorescein isothiocyan
ate fluorescence microscopy. Following this procedure, we provide immu
nohistochemical evidence for the distribution of cGMP-accumulating neu
rons in the brain of adult Xenopus. In most brain areas, the distribut
ion of nNOS and cGMP immunoreactive structures (neuron somata and fibe
rs) is distinct and separate, for instance in the dorsal pallium, the
lateral thalamic nuclei, the optic tectum, the locus coeruleus and the
reticular formation. However, nNOS and cGMP immunoreactive structures
are often found in the vicinity of each other, and in the optic tectu
m even in adjacent neuron fibers and somata. The present observations
are in line with the presence of an NO-dependent soluble guanylate cyc
lase in distinct brain areas of Xenopus laevis, corroborating similar
data in the mammalian brain. Further, our observations may add to the
understanding of the anatomical connectivity pattern and functional re
levance of the NOergic system in the amphibian brain. (C) 1998 Elsevie
r Science B.V. All rights reserved.