Journal of Neuroscience, Vol 16, 836-842, Copyright © 1996 by Society for Neuroscience
Neonatal deprivation of maternal touch may suppress ornithine decarboxylase via downregulation of the proto-oncogenes c-myc and max
S Wang, JV Bartolome and SM Schanberg
Department of Pharmacology, Duke University, Durham, North Carolina 27710, USA.
Previously, we have shown that short-term (1 hr) separation of neonatal
rats from their mother (MS) suppresses basal ornithine decarboxylase (ODC)
synthesis and tissue ODC response to trophic factors. This effect in the
pup is caused by absence of maternal tactile stimulation (touch) but not
from lack of maternal nutrients (food). This study was performed to examine
in 10-d-old rats whether maternal touch deprivation affects expression of
certain hepatic proto-oncogenes, the protein products of which are known to
interact with the regulatory region of the ODC gene. Prolactin (PRL)
injected subcutaneously increased hepatic ODC activity as well as mRNA
levels of ODC and the proto-oncogenes c-fos, c-jun, junB, junD, c-myc, and
max. MS significantly suppressed PRL-induced increases in ODC enzyme
activity and c-myc, max, and ODC mRNAs but had little effect on expression
of the other proto-oncogenes. PRL-induced stimulation of ODC, c-myc, and
max mRNAs also was depressed in neonates placed with an anesthetized
lactating dam (touch-deprived) but not in pups placed with nipple- ligated
dams (food-deprived). Furthermore, unlike its effect on preweanling-age
pups (< 20 d old), MS did not alter expression of either ODC or c-myc
mRNAs in 25-d-old pups acutely separated from their mother. These findings
indicate that suppression of ODC gene transcription in the neonatal pup
during MS may be mediated by downregulation of the ODC gene transactivator
proto-oncogenes c-myc and max. They are also consistent with our previous
observation that lack of maternal touch, but not maternal milk, initiates
the physiological alterations induced by MS.