Journal of Neuroscience, Vol 12, 3272-3281, Copyright © 1992 by Society for Neuroscience
Habenula and thalamus cell transplants mediate different specific patterns of innervation in the interpeduncular nucleus
TC Eckenrode, M Murray and F Haun
Department of Anatomy and Neurobiology, Medical College of Pennsylvania, Philadelphia 19129.
Innervation of specific peptidergic and cholinergic compartments of the
interpeduncular nucleus (IPN) was investigated using embryonic cell
suspension transplants immunoreactive for substance P (SP) and ChAT. In
both neonatal and adult host rats, the IPN was first denervated of its
normal SP and cholinergic input from the medial habenula by bilateral
lesions of the fasciculi retroflexi (FR). In adult hosts, transplants of
embryonic habenular cells placed near the denervated IPN mediated a return
of the normal pattern of SP staining restricted to habenula- target
subnuclei, plus an increase in staining intensity of SP cells intrinsic to
the IPN. There was no recovery of ChAT staining. A similar pattern of SP
staining resulted following habenular transplants into neonatal hosts, but
in addition there was a partial recovery of normal ChAT staining in
cholinergic subnuclei and anomalous ChAT staining in normally peptidergic
subnuclei. Control transplants of embryonic thalamus cells placed into
adult hosts produced a surprising pattern of ChAT staining in the IPN
identical to that seen with habenula transplants placed into neonatal
hosts; the adult IPN was thus able to support reinnervation mediated by an
aberrant cholinergic source while being refractory to its normal habenular
cholinergic afferents. This pattern of results implies regulation by the
IPN of habenular SP and cholinergic innervation, and some interaction
between the maturing normal cholinergic afferents and their targets that is
missing when these afferent sources are abnormal.