PROJECTIONS FROM THE RAPHE NUCLEI TO THE OLFACTORY BULB IN THE CAT——HRP METHOD
He Ye(Department of Anatomy, Lanzhou Medical College)
The ascending projections from the raphe nuclei of the brain stcm in the cat were studied with the method of the retrograde transport of horseradish peroxidase and the shape and the distribution of the labeled cells in the raphe nuclei were analysed. It was demonstrated that following injecting HRP into one olfactory bulb the labeied cells appeared regularly in the nucleus raphe dorsalis (RD), the nucleus cen-tralis superior (CS), the nucleus linearis intermedius (LI) and the nucleus linearis rostralis (LR).The rest of the raphe nuclei nucleus raphe obscurus, nucleus raphe pallidus, nucleus raphe magnus and nucleus raphe pontiswere not labeled. The labeled cells in the four nuclei varied in number and had dif-ferent distribution patterns. The labeled cells in RD were most nume-rous of the four and distributcd along the midline, concentrated in its rostral and middle parts and few in its caudal part. The labeled cells in CS were second in number, presented only in its caudal half but not in its rostral half. The labeled cells in LI were the least and scattered in its whole extent. Less labeled cells were seen in LR and presented mainly in its ventral part ipsilaterally. Previous studies about the projections of the raphe nuclei to the olfactory bulb are reviewed and only RD and CS, no other raphe nuclei, have been reported to project to the olfactory bulb. This study agrees with the previous studies describing the projections of RD and CS to the olfactory bulb and suggests that LI and LR are the additional sources of the afferent fibers to the olfactory bulb.