FMRF-amide-like immunoreactivity (FMRF-amide-LIR) in the vegetative areas and dorsal horn of the spinal cord of some rodents.

A dorsal horn fiber system is revealed along the entire length of the spinal cord of guinea pig, rat and wild hamster by means of FMRF-amide immunocytochemistry. Additionally by the same method are revealed two IR networks in the intermediate zone of the thoracic and sacral spinal cord which are identical with the described earlier by us (Galabov and Davidoff, 1976; Galabov 1980; Davidoff et al. 1985) vegetative networks. The dorsal horn fiber system on transversal sections possesses five main components identical with the components of such system described earlier by Davidoff et al. (1986) by means of SP immunocytochemistry. On horizontal sections it is composed of two FMRF-amide LIR networks: One is localized in the superficial layers of the dorsal horn (Laminae I and II) and the second in laminae IV and V, in the borders of nucleus proprius. Both networks are interconnected and in the thoracic and sacral spinal cord are connected with the vegetative networks. It is suggested that some fibers of the dorsal horn fiber system originate from dorsal-root ganglia and may represent primary sensory or visceral afferents. It is likely that this system together with the vegetative networks may represent the morphological basis for the integration of 1) the central and peripheral vegetative nervous systems and 2) the somatic and vegetative nervous system. The presence of different neuropeptides in the dorsal horn fiber system gives ground to term it as a Peptidergic Dorsal Horn Fiber System (pDHFS).