S. Vanhatalo et al., NITRIC OXIDE-SYNTHESIZING NEURONS ORIGINATING AT SEVERAL DIFFERENT LEVELS INNERVATE RAT PENIS, Neuroscience, 75(3), 1996, pp. 891-899
While the crucial role of neurally produced nitric oxide in mediating
penile erection is well established, the understanding of the peripher
al neuroanatomy of the nitric oxide-ergic pathways is still incomplete
. This study was designed to elucidate further the distribution of nit
ric oxide synthase, and its relation to the distribution of neuropepti
des and tyrosine hydroxylase in all penis-projecting neural pathways.
A triple-labelling technique was employed, with the retrograde tracer
Fluoro Gold combined with neuropeptide immunohistochemistry and nicoti
namide adenine dinucleotide phosphate (NADPH)-diaphorase histochemistr
y, a marker of nitric oxide synthase. The presence within the penis of
scattered nerve cell bodies exhibiting NADPH-diaphorase activity was
revealed. Most (76%) of the penis-projecting neurons in the major pelv
ic ganglion exhibited NADPH-diaphorase activity and immunoreactivity t
o vasoactive intestinal peptide, while none of them contained tyrosine
hydroxylase. Sympathetic paravertebral postganglionic neurons, in tur
n, contained tyrosine hydroxylase, but did not exhibit NADPH-diaphoras
e activity. In the afferent, sensory neurons projecting to the penis f
rom the dorsal root ganglia, NADPH-diaphorase activity coexisted with
immunoreactivity to both substance P (8%) and calcitonin gene-related
peptide (26%). Preganglionic neurons originating in the spinal cord in
termediolateral column at the thoracolumbar level T11-L3 terminated, n
ot only in the major pelvic ganglion, but also within the penis. The m
ajority (81%) of the penis-projecting neurons exhibited NADPH-diaphora
se activity. The results indicate that the rat penis receives several
different nitric oxide-ergic neural projections. It is therefore possi
ble that nitric oxide affects penile erection at several neuronal leve
ls. Copyright (C) 1996 IBRO.