The distribution and origin of a novel brain peptide, neuropeptide Y, in the spinal cord of several mammals

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Abstract
The distribution of neuropeptide Y [NPY]‐immunoreactive material was examined in the spinal cord and dorsal root ganglia of rat, guinea‐pig, cat, marmoset, and horse. Considerable concentrations of NPY and similar distribution patterns of immunoreactive nerve fibres were found in the spinal cord of all species investigated. The dorsal root ganglia of the cat and the horse contained numerous immunoreactive nerve fibres, but in these species, as in the other three studied [rat, guinea‐pig, marmoset], no positively stained cell bodies were found. Neuropeptide Y‐immunoreactive nerves were observed at all levels of the spinal cord, being most concentrated in the dorsal horn. In the rat, guinea‐pig, and marmoset, there was a marked increase of NPY‐immunoreactive fibres in the lumbosacral regions of the spinal cord, and this was reflected by a considerable increase of extractrable NPY. Estimations of NPY‐immunoreactive material in the various regions of the rat spinal cord were as follows: cervical, 13.8 ±1.0; thoracic, 21.1 ±2.5; lumbar, 16.3 ±2.9; sacral, 92.4 ±8.5 pmol/gm wet weight of tissue ±SEM. In the ventral portion of the guinea‐pig spinal cord they were as follows: cervical, 7.1 ±1.2; thoracic, 8.2 ±3.6; lumbar, 22.6 ±7.0; sacral, 36.7 ±9.5 pmol/gm wet weight of tissue ±SEM. Analysis of spinal cord extracts by reverse phase high performance liquid chromatography [HPLC] demonstrated that NPY‐immunoreactive material elutes in the position of pure NPY standard. No changes in the concentration and distribution of the NPY‐like material in the rat spinal cord were observed following a variety of surgical and pharmacological manipulations, including cervical rhizotomy, sciatic nerve section and ligation, and local application of capsaicin [50 mM] to one sciatic nerve. It is therefore suggested that most of the NPY‐immunoreactive material in the spinal cord is derived either from intrinsic nerve cell bodies or from supraspinal tracts.