Zx. Cheng et al., Projections of the dorsal motor nucleus of the vagus to cardiac ganglia ofrat atria: An anterograde tracing study, J COMP NEUR, 410(2), 1999, pp. 320-341
We injected the anterograde fluorescent tracer 1,1'-dioleyl-3,3,3',3 '-tetr
amethylindocarbocyanine methanesulfonate (DiI) into the dorsal motor nucleu
s of the vagus (DmnX), counterstained the cardiac ganglia with Fluorogold (
FG), and used confocal microscopy to examine the distributions and differen
t types of DmnX fibers in wholemounts of the atria. We also quantified the
number of DmnX cardiac axons and the number of innervated cardiac principal
neurons (PNs). Rats with unilateral DiI injections were used in three diff
erent experiments, including unilateral FG soaking of cervical vagal trunks
, intracranially rhizotomizing the vagal afferent roots, or contralaterally
sectioning the cervical vagus. These manipulations indicated that DiI-labe
led cardiac fibers were exclusively from the DmnX. Our observations establi
shed that: (1) three major ganglionic plexuses were localized in the epicar
dium; (2) both sides of the DmnX supplied significant fibers to each of the
plexuses; (3) these cardiac efferents formed dense basket terminals around
individual PNs; (4) collaterals of individual DmnX fibers diverged, produc
ing calyx endings on multiple PNs; (5) small intensely fluorescent (SIF) ce
lls in the cardiac plexuses were innervated pericellularly; (6) individual
axons could innervate both PNs and SIF cells; (7) the total number of DmnX
fibers were in the range of [68, 96; left] and [67, 115; right]; (8) these
fibers innervated 709 (left) and 494 (right), or at least 18% and 12%, of t
he PNs, respectively; and (9) vagal preganglionics exhibited a degree of la
teralization: Significantly more PNs were contacted by fiber varicosities i
n the sinoatrial plexus than in the atrioventricular plexus after right Dmn
X injections. In summary, the present observations suggest that the DmnX pl
ays a significant role(s) in controlling the heart. (C) 1999 Wiley-Liss. In
c.