Highlights
- •Rat superior salivatory nucleus (SSN) neurons were immunohistochemically studied.
- •SSN neurons had orexin-A- and -B-immunoreactive nerve fibers.
- •SSN neurons were immunoreactive for orexin receptor-1 and -2.
- •Orexins may regulate activation of SSN neurons for salivary secretion.
Abstract
Orexin (OX), which regulates sleep and wakefulness and feeding behaviors has 2 isoforms,
orexin-A and -B (OXA and OXB). In this study, the distribution of OXA and OXB was
examined in the rat superior salivatory nucleus (SSN) using retrograde tracing and
immunohistochemical and methods. OXA- and OXB-immunoreactive (-ir) nerve fibers were
seen throughout the SSN. These nerve fibers surrounded SSN neurons retrogradely labeled
with Fast blue (FB) from the corda-lingual nerve. FB-positive neurons had pericellular
OXA- (47.5%) and OXB-ir (49.0%) nerve fibers. Immunohistochemistry for OX receptors
also demonstrated the presence of OX1R and OX2R in FB-positive SSN neurons. The majority
of FB-positive SSN neurons contained OX1R- (69.7%) or OX2R-immunoreactivity (57.8%).
These neurons had small and medium-sized cell bodies. In addition, half of FB-positive
SSN neurons which were immunoreactive for OX1R (47.0%) and OX2R (52.2%) had pericellular
OXA- and OXB-ir nerve fibers, respectively. Co-expression of OX1R- and OX2R was common
in FB-positive SSN neurons. The present study suggests a possibility that OXs regulate
the activity of SSN neurons through OX receptors.
Keywords
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Article info
Publication history
Published online: July 20, 2020
Accepted:
July 14,
2020
Received in revised form:
May 21,
2020
Received:
October 31,
2019
Identification
Copyright
© 2020 Elsevier B.V. All rights reserved.
