CEREBELLAR AND SPINAL PROJECTIONS OF THE COERULEUS COMPLEX IN THE DUCK - A FLUORESCENT RETROGRADE DOUBLE-LABELING STUDY

The double fluorescent retrograde tracing technique was used to identi fy, within the coeruleus complex (Co complex) of the duck, the nerve c ells projecting to the cerebellar cortex and to the spinal cord. This technique was also used to investigate the possibility that the cerebe llar and spinal projections of the Co complex are collaterals of the s ame axons. In the same animal, nuclear Diamidino yellow dihydrochlorid e (DY) fluorescent tracer was placed into the cerebellar cortex of fol ia V-VII, and cytoplasmic fluorescent Fast blue (FB) dye was injected into C-3-C-4 spinal cord segments. FB labeled multipolar somata and DY fluorescent nuclei were intermingled within the dorsal caudal region of the locus coeruleus (LCo) and within the dorsal division of the nuc leus subcoeruleus (dSCo). Moreover, in the LCo, a low proportion of do uble-labeled neurons (about 3-4% of labelings) was evidenced among sin gle-labeled neurons. In the ventral division of the nucleus subcoerule us (vSCo), occasional DY labeled nuclei were found, whereas FB-labeled cells were frequently present. The present findings reveal the locati on of the coeruleocerebellar and coeruleospinal projecting neurons wit hin the Co complex of the duck. They are intermingled in the caudal po rtion of the LCo and along the rostrocaudal extent of the subjacent dS co. The LCo and the dSCo are the major source of the projections to th e folia V-VII, whereas the vSCo contributes very slightly to the inner vation of the cerebellar injected areas. Moreover, the double-labeling study demonstrates that in the duck a low percentage of neurons withi n the ventrolateral portion of the caudal region of the LCo projects b oth to the cerebellar cortex of folia V-VII and to C3-C4 spinal cord s egments via collaterals. Therefore, these neurons simultaneously influ ence the cerebellar cortex and spinal cord. The possibility that the p rojections studied are noradrenergic and that they play a role in feed ing is discussed. Anat. Rec. 251:392-397, 1998. (C) 1998 Wiley-Liss, I nc.