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Anatomical Location of the Mesencephalic Locomotor Region and Its Possible Role
in Locomotion, Posture, Cataplexy, and Parkinsonism
#MMPMID26157418
Sherman D
; Fuller PM
; Marcus J
; Yu J
; Zhang P
; Chamberlin NL
; Saper CB
; Lu J
Front Neurol
2015[]; 6
(?): 140
PMID26157418
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The mesencephalic (or midbrain) locomotor region (MLR) was first described in
1966 by Shik and colleagues, who demonstrated that electrical stimulation of this
region induced locomotion in decerebrate (intercollicular transection) cats. The
pedunculopontine tegmental nucleus (PPT) cholinergic neurons and midbrain
extrapyramidal area (MEA) have been suggested to form the neuroanatomical basis
for the MLR, but direct evidence for the role of these structures in locomotor
behavior has been lacking. Here, we tested the hypothesis that the MLR is
composed of non-cholinergic spinally projecting cells in the lateral pontine
tegmentum. Our results showed that putative MLR neurons medial to the PPT and MEA
in rats were non-cholinergic, glutamatergic, and express the orexin (hypocretin)
type 2 receptors. Fos mapping correlated with motor behaviors revealed that the
dorsal and ventral MLR are activated, respectively, in association with
locomotion and an erect posture. Consistent with these findings, chemical
stimulation of the dorsal MLR produced locomotion, whereas stimulation of the
ventral MLR caused standing. Lesions of the MLR (dorsal and ventral regions
together) resulted in cataplexy and episodic immobility of gait. Finally,
trans-neuronal tracing with pseudorabies virus demonstrated disynaptic input to
the MLR from the substantia nigra via the MEA. These findings offer a new
perspective on the neuroanatomic basis of the MLR, and suggest that MLR
dysfunction may contribute to the postural and gait abnormalities in
Parkinsonism.
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