VASOACTIVE-INTESTINAL-PEPTIDE EFFERENT PROJECTIONS OF THE SUPRACHIASMATIC NUCLEUS IN ANTERIOR HYPOTHALAMIC TRANSPLANTS - CORRELATION WITH FUNCTIONAL RESTORATION OF CIRCADIAN BEHAVIOR
Pj. Sollars et Ge. Pickard, VASOACTIVE-INTESTINAL-PEPTIDE EFFERENT PROJECTIONS OF THE SUPRACHIASMATIC NUCLEUS IN ANTERIOR HYPOTHALAMIC TRANSPLANTS - CORRELATION WITH FUNCTIONAL RESTORATION OF CIRCADIAN BEHAVIOR, Experimental neurology, 136(1), 1995, pp. 1-11
Circadian rhythmicity can be restored by transplantation of fetal ante
rior hypothalamic (AH) tissue containing the suprachiasmatic nucleus (
SCN) into hosts rendered arrhythmic by SCN ablation. However, the natu
re of the SCN effector pathways mediating functional recovery has rema
ined elusive. To examine implant-derived SCN innervation of the host,
AH homografts (hamster-to-hamster) and heterografts (mouse- or rat-to-
hamster) were employed and the distribution of vasoactive intestinal p
eptide (VIP) within the SCN terminal fields was evaluated. A compariso
n was made between cases where circadian locomotor activity was restor
ed and cases where circadian rhythmicity remained disrupted following
AH transplantation. A dense aggregation of VIP neurons and processes w
as identified in each transplant that restored behavioral rhythmicity
in the host. In these cases, SCN-derived VIP fibers were integrated wi
th the host brain and could be identified in host terminal fields typi
cally innervated by SCN-VIP fibers. A correlation was noted between VI
P innervation of the host paraventricular thalamic nucleus (PVT) and r
estoration of circadian rhythmicity. Neither qualitative nor quantitat
ive differences in transplant VIP projections were noted between AH ho
mografts and heterografts. These results demonstrate that SCN VIP neur
ons in AH transplants send an appropriately restricted set of efferent
projections to the host brain and suggest that SCN efferent projectio
ns to the PVT may participate in mediating the functional recovery of
circadian locomotor activity. (C) 1995 Academic Press, Inc.