Neuronal and inducible nitric oxide synthase immunoreactivity following serotonin depletion.
Serotonin (5HT) modulates the development and plasticity of its innervation areas in the central nervous system (CNS). Astrocytic 5HT(1A) receptors are involved in the plastic phenomena by releasing the astroglial-derived neurotrophic factor S-100beta. Several facts have demonstrated that nitric oxide (NO) and the nitric oxide synthase enzyme (NOS) may also be involved in this neuroglial interaction: (i) NO, S-100beta and 5HT are involved in CNS plasticity; (ii) micromolar S-100beta concentration stimulates inducible-NOS (iNOS) expression; (iii) neuronal NOS (nNOS) immunoreactive neurons are functionally and morphologically related to the serotoninergic neurons; (iv) monoamines level, including 5HT, can be modulated by NO release. We have already shown that 5HT depletion increases astroglial S-100beta immunoreactivity, induces neuronal cytoskeletal alterations and produces an astroglial reaction, while once 5HT level is recovered, a sprouting phenomenon occurs [Brain Res. 883 (2000) 1-14]. To further characterize the relationship among nNOS, iNOS and 5HT we have analyzed nNOS and iNOS expression in the CNS after 5HT depletion induced by parachlorophenylalanine (PCPA) treatment. Studies were performed immediately after ending the PCPA treatment and during a recovery period of 35 days. Areas densely innervated by 5HT fibers were studied by means of nNOS and iNOS immunoreactivity as well as NADPH diaphorase (NADPHd) staining. All parameters were quantified by computer-assisted image analysis. Increased nNOS immunoreactivity in striatum and hippocampus as well as increased NADPHd reactivity in the striatum, hippocampus and parietal cortex were found after PCPA treatment. The iNOS immunoreactivity in the corpus callosum increased 14 and 35 days after the end of PCPA treatment. These findings showed that nNOS immunoreactivity and NADPHd activity increased immediately after 5HT depletion evidencing a close functional interaction between nitrergic and serotoninergic systems. However, iNOS immunoreactivity increased when 5HT levels were normalized, which could indicate one of the biological responses to S-100beta release.
Ramos
Alberto Javier
AJ
Instituto de Biología Celular y Neurociencia Prof E De Robertis, Facultad de Medicina, Universidad de Buenos Aires, Paraguay 2155 (1121) Buenos Aires, Argentina.
Tagliaferro
Patricia
P
López-Costa
Juan José
JJ
López
Ester María
EM
Pecci Saavedra
Jorge
J
Brusco
Alicia
A
D000818:Animals; D004525:Efferent Pathways / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D010134:Fenclonine / Q000494:pharmacology; D006624:Hippocampus / Q000166:cytology / Q000378:metabolism; D007150:Immunohistochemistry; D008297:Male; D009252:NADPH Dehydrogenase / Q000378:metabolism; D017072:Neostriatum / Q000166:cytology / Q000378:metabolism; D009414:Nerve Growth Factors; D026602:Nitrergic Neurons / Q000201:enzymology*; D009569:Nitric Oxide / Q000096:biosynthesis; D019001:Nitric Oxide Synthase / Q000378:metabolism*; D010296:Parietal Lobe / Q000166:cytology / Q000378:metabolism; D017729:Presynaptic Terminals / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D011903:Raphe Nuclei / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D064568:S100 Calcium Binding Protein beta Subunit; D009418:S100 Proteins / Q000378:metabolism; D012701:Serotonin / Q000172:deficiency*; D012702:Serotonin Antagonists / Q000494:pharmacology; D013687:Telencephalon / Q000166:cytology / Q000378:metabolism*; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology
D009414:Nerve Growth Factors; D064568:S100 Calcium Binding Protein beta Subunit; D009418:S100 Proteins; D012702:Serotonin Antagonists; D009569:Nitric Oxide; D012701:Serotonin; D019001:Nitric Oxide Synthase; D009252:NADPH Dehydrogenase; D010134:Fenclonine