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Bilateral serotonergic projections to the dorsal hippocampus of the rat: Simultaneous localization of 3 H‐5HT and HRP after retrograde transport
Author(s) -
Azmitia Efrain C.
Publication year - 1981
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/cne.902030410
Subject(s) - dorsal raphe nucleus , locus coeruleus , raphe nuclei , serotonergic cell groups , nucleus , serotonergic , hippocampus , locus ceruleus , median raphe nucleus , axoplasmic transport , biology , 5 ht receptor , neuroscience , anatomy , serotonin , chemistry , biochemistry , dopamine , receptor , substantia nigra , dopaminergic
Horseradish peroxidase (HRP, Sigma VI, 30–70 nl of a 10–15% solution in saline) or 3H ‐5HT (30 Ci/mmole, 2.5 × 10 −3 M containing 3.3 × 10 −3 M norepinephrine in saline, 50–100 nl) was injected unilaterally into the dorsal hippocampus in separate groups of rats. HRP‐labeled cells were seen in the hippocampus, medial septal nucleus, nucleus of the diagonal band, supramammilary nucleus, median raphe nucleus, interfascicular portion of the dorsal raphe nucleus, and the locus coeruleus. In contrast, 3H ‐5HT‐labeled cells were largely restricted to the raphe nuclei. In this nucleus an equal number of ipsilateral and bilateral cells were found. Occasionally, these labeled cells stretched across the midline (bridge pattern). In another series, the 3 H‐5HT and HRP were injected into the same hippocampus either as a mixture or sequentially. This resulted in double labeling of the median and dorsal raphe neurons. A final group of rats received injections of 3 H‐5HT and HRP into opposing hippocampi. Double‐labeled cells accounted for 10% of the neurons labeled. In addition, closely paired neurons composed of an HRP‐and 3 H‐5HT‐containing cell were found. In summary, the serotonergic fibers may play a key role in harmonizing the electrical activity of the hippocampi by use of bilateral projections, paired neurons with differential projections, and bridging neurons stretching across the midline but with unilateral projections.