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Immunocytochemical localization of calretinin‐containing neurons in the rat periaqueductal gray and colocalization with enzymes producing nitric oxide: A double, double‐labeling study
Author(s) -
Barbaresi Paolp,
Quaranta Alexia,
Amoroso Salvatore,
Mensà Emanuela,
Fabri Mara
Publication year - 2012
Publication title -
synapse
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.809
H-Index - 106
eISSN - 1098-2396
pISSN - 0887-4476
DOI - 10.1002/syn.21509
Subject(s) - colocalization , immunocytochemistry , calretinin , periaqueductal gray , nadph dehydrogenase , axon , nitric oxide synthase , chemistry , nitric oxide , microbiology and biotechnology , biology , immunohistochemistry , anatomy , neuroscience , endocrinology , central nervous system , immunology , midbrain
Abstract The pattern of distribution and colocalization of the calcium‐binding protein calretinin (Cal) and of enzymes producing nitric oxide (NO) was examined in the rat periaqueductal gray matter (PAG) using two different experimental approaches, by combining Cal immunocytochemistry with NADPH‐diaphorase (NADPH‐d) histochemistry and with NOS immunocytochemistry, respectively. Cal‐immunopositive neurons were found throughout the rostrocaudal extension of both dorsolateral (PAG‐dl) and ventrolateral PAG (PAG‐vl). Double‐labeled neurons were found only in PAG‐dl. The first experimental approach indicated that 33–41% of the NADPH‐d‐positive (Nadph+) cells were immunoreactive for Cal, whereas NADPH‐d activity appeared in 19–26% of the Cal‐immunopositive (Cal IP ) neurons. Two‐color immunofluorescence revealed that ∼39–43% of NOS‐immunoreactive (NOS IR ) neurons were double‐labeled with Cal and ∼23% of Cal IP neurons expressed NOS immunoreactivity. Measurement in semithin sections of the size of the three neuronal populations found in PAG‐dl, showed that Cal IP neurons had a cross‐sectional area of 94.7 μm 2 , whereas Nadph+ neurons and double‐labeled neurons were slightly smaller, having a cross‐sectional area of 90.5 and 91.4 μm 2 , respectively. On electron microscopy, Cal IP axon terminals formed either symmetric or asymmetric synapses; although the latter synapses were more numerous, both types contacted preferentially Cal IP dendrites. These experiments suggest that PAG‐dl is characterized by a high degree of heterogeneity. Synapse, 2012. © 2011 Wiley Periodicals, Inc.