Atrial natriuretic factor-like immunoreactivity in spinal cord and in primary sensory neurons of spinal and trigeminal ganglia of guinea-pig: correlation with tachykinin immunoreactivity.

Atrial natriuretic factor (ANF) is a cardiac hormone with various functions in body homeostasis. It is also processed in the brain and in the peripheral nervous system where it appears to play a role as a neuromodulator. Little is known about the presence of ANF throughout the spinal cord of the guinea-pig. We therefore examined the distribution of ANF and its possible interrelation with primary sensory afferents in this species. Using enzyme-and fluorescence-immunohistochemistry on deparaffinized sections. ANF-like immunoreactivity was found to be present in nerve fibers in laminae I/II of the spinal cord and in neurons of spinal and trigeminal ganglia. Tachykinins and ANF coexisted in very few fibers of the spinal cord but did not coexist in primary sensory spinal or trigeminal neurons. Our results indicate that spinal ANF-immunoreactive fibers are of dual origin, primary sensory and non-primary sensory. The possibly heterogeneous source of the non-primary sensory ANF, its possible coexistence with other co-transmitters and functional implications are discussed.