Fluorescent double-label study of lateral reticular nucleus projections to the spinal cord and periaqueductal gray in the rat

Abstract

Following injections of WGA-HRP into either the spinal cord or periaqueductal gray, labeled neurons were observed bilaterally along the periphery of the lateral reticular nucleus (LRN) magnocellular division. The possibility that some of these neurons in the LRN provide collateral axonal branches to both the periaqueductal gray and the spinal cord was investigated in rats using a retrograde double-labeling method employing two different fluorescent tracers, True Blue and Nuclear Yellow. Following sequential injection of the two fluorescent axonal tracers into the spinal cord and periaqueductal gray in the same animal, a modest number of double-labeled neurons were observed bilaterally near the medial and dorsal perimeter of the magnocellular division of the LRN. The labeled neurons were distinctly multipolar in shape and measured approximately 15-18 mu in their greatest transverse diameter. No double-labeled neurons were observed in the parvocellular or subtrigeminal divisions of the LRN. Based upon these observations, it is suggested that collaterals of the LRN-spinal pathway provide feedback information to the periaqueductal gray that might then be used to modulate the participation of the latter cell group in a variety of pain processing and cardiovascular regulatory functions.

The spino-bulbar-cerebellar pathway: organization and neurochemical properties of spinal cells that project to the lateral reticular nucleus in the rat

“…Most of our spinal injection sites were focussed upon the ventrolateral/ventromedial region of the cord but there was spread also into the intermediate gray matter. The present and previous studies of retrogradely labeled spinal cells following injections of tracer substances into the LRt ( Corvaja et al, 1977a ; Hrycyshyn and Flumerfelt, 1981 ; Menétrey et al, 1983 ; Shokunbi et al, 1985 ; Koekkoek and Ruigrok, 1995 ; Lee and Mihailoff, 1999 ) reveal that neurons in laminae VII, VIII, and X project predominantly to the contralateral LRt ( Menétrey et al, 1983 ; Shokunbi et al, 1985 ). The axons of bVFRT neurons ascend in the ventral part of the lateral funiculus ( Ekerot, 1990b ) and project contralaterally at the segmental level ( Holmqvist et al, 1960 ; Lundberg and Oscarsson, 1962 ; Rosen and Scheid, 1973a ; Ekerot, 1990b ).…”

Evidence that dopamine‐beta‐hydroxylase immunoreactive neurons in the lateral reticular nucleus project to the spinal cord in the rat

“…4, 6, and 8). It has also been reported that spinal-projecting neurons at this location send axon collaterals into the ventrolateral portion of the periaqueductal gray matter (Lee and Mihailoff, 1999). The finding confirms the possible role for this descending system in pain suppression.…”

The Use of Hoechst Dyes for DNA Staining and Beyond

“…Hoechst 34580 possesses a dimethylamine group instead of the phenol, which shifts its emission maximum to 490 nm compared to the 461 nm of Hoechst 33258 and Hoechst 33342. Emission of yet another dye of the family, Nuclear yellow (Hoechst S769121), is further shifted to the yellow region (495 nm), which allows its use together with a popular retrograde tracer True Blue for mapping branched neurons in animal brains [15][16][17][18].…”