Nigral axon terminals are in contact with parvicellular reticular neurons which project to the motor trigeminal nucleus in the rat.
We examined whether in the rat the descending fibers from the substantia nigra pars reticulata (SNr) were in contact with premotor neurons projecting to the motor trigeminal nucleus (Vm), using a combined anterograde and retrograde tracing technique. After ipsilateral injections of cholera toxin B subunit (CTb) into the Vm and biotinylated dextranamine (BDA) into the SNr, numerous CTb-labeled neurons were distributed bilaterally with slightly ipsilateral dominance in the parvicellular reticular formation (RFp), where many BDA-labeled axons with bouton-like varicosities were found bilaterally with a clear-cut ipsilateral dominance. The overlapping distribution of these labeled axons and neurons was more prominent in the rostral RFp than in the caudal RFp. Within the neuropil of the RFp, some of the BDA-labeled axons made synapses with the somata and proximal dendrites of CTb-labeled neurons. Thus, the present study demonstrated the existence of an indirect pathway from the SNr to the Vm, relayed by the RFp.
Yasui
Y
Y
Department of Anatomy (2nd Division), Shimane Medical University, Izumo, Japan. yyasui@shimane-med.ac.jp
Tsumori
T
T
Ono
K
K
Kishi
T
T
D000818:Animals; D001710:Biotin / Q000031:analogs & derivatives; D002772:Cholera Toxin / Q000494:pharmacology; D003911:Dextrans; D005456:Fluorescent Dyes; D007150:Immunohistochemistry; D008297:Male; D008854:Microscopy, Electron; D009434:Neural Pathways / Q000166:cytology / Q000502:physiology; D009474:Neurons / Q000502:physiology*; D017729:Presynaptic Terminals / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D012154:Reticular Formation / Q000166:cytology* / Q000502:physiology*; D013378:Substantia Nigra / Q000166:cytology* / Q000502:physiology*; D014279:Trigeminal Nucleus, Spinal / Q000166:cytology* / Q000502:physiology*
D003911:Dextrans; D005456:Fluorescent Dyes; C076397:biotinylated dextran amine; D001710:Biotin; D002772:Cholera Toxin