Collateral projection from the forebrain and mesopontine cholinergic neurons to whisker-related, sensory and motor regions of the rat.
The primary goal of this anatomical study was to examine in the rat whether cholinergic neurons provide axon collaterals to whisker-related, sensorimotor regions at cortical, thalamic, and brainstem levels, using a combined method of retrograde tracing and choline acetyltransferase (ChAT) immunostaining. First, when injections were made at primary sensory (S1) barrel field/primary whisker motor (M1) cortices, cholinergic neurons with dual projections were observed in the basal nucleus of Meynert (BM), mainly at middle level; the projection was almost exclusively ipsilateral (99%+/-0.7%, n=6). Second, following unilateral injections of tracers into ventroposteromedial (VPM) barreloids/ventrolateral (VL) thalamic nucleus, dual-projecting cells were observed in the mesopontine tegmental complex including the pedunculopontine tegmental (PTg) and laterodorsal tegmental (LDTg) nuclei, mainly at rostral to middle levels; the projection exhibited ipsilateral dominance, i.e., 67%+/-1.3% (n=6) for the PTg and 64%+/-1.2% (n=6) for the LDTg. Finally, when injections were made at whisker-related, principal sensory trigeminal (Pr5)/facial motor (Mo7) nuclei, a relatively small number of labeled neurons were observed in the PTg and the LDTg at middle to caudal levels; within LDTg, labeled cells occupied the ventral portion of the dorsal LDTg as well as the ventral LDTg (LDTgV). This projection exhibited contralateral preponderance, i.e., 67%+/-2.0% (n=6) for the PTg and 69%+/-3.2% (n=6) for the LDTg. Taken together, the present observations demonstrated that each division of the BM, PTg, and LDTg possessed a differential functional organization with respect to its collateral projection to whisker-related sensorimotor targets, suggesting that the cholinergic projection might play a modulatory role in vibrissal sensorimotor integration, which allows the guidance of behavioral action essential for the survival of the animal.
Beak
Suk K
SK
Department of Anatomy, College of Medicine, Konkuk University, Hwayang-dong, Gwangjin-gu, Seoul, Korea.
Hong
Eun Y
EY
Lee
Hyun S
HS
D000109:Acetylcholine / Q000378:metabolism; D000818:Animals; D001921:Brain / Q000166:cytology* / Q000378:metabolism; D009434:Neural Pathways / Q000166:cytology*; D009474:Neurons / Q000166:cytology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014738:Vibrissae / Q000294:innervation* / Q000378:metabolism
D000109:Acetylcholine