EFFECTS OF GESTATIONAL OR NEONATAL TREATMENT WITH ALPHA-DIFLUOROMETHYLORNITHINE ON ORNITHINE DECARBOXYLASE AND POLYAMINES IN DEVELOPING RAT-BRAIN AND ON ADULT-RAT NEUROCHEMISTRY
M. Sparapani et al., EFFECTS OF GESTATIONAL OR NEONATAL TREATMENT WITH ALPHA-DIFLUOROMETHYLORNITHINE ON ORNITHINE DECARBOXYLASE AND POLYAMINES IN DEVELOPING RAT-BRAIN AND ON ADULT-RAT NEUROCHEMISTRY, Experimental Brain Research, 108(3), 1996, pp. 433-440
Pregnant rats were treated for five consecutive days during gestation
with s.c. injections of the ornithine decarboxylase (ODC) inhibitor al
pha-difluoromethylornithine (DFMO). Treatment beginning at gestational
days 13 or 14 was effective in inhibiting ODC and altering polyamine
levels, and resulted in relatively small decreases in body and forebra
in weight, but not in significant differences in adult neurochemistry.
Neonatal rats were treated with DFMO from postnatal day 0 (PD 0) to P
D 24. In addition to some somatic effects (decreased body weight, dela
yed eyelid opening and delayed fur growth) the postnatal treatment res
ulted in a permanent decrease in brain weight, which was mainly due to
a dramatic decrease in cerebellar size. During treatment, and 3 days
after the end of it, the levels of putrescine and spermidine, but not
those of spermine, were consistently lower in the cerebellum and foreb
rain of DFMO-treated rats than in controls. On the other hand, ODC app
eared strongly inhibited only during the first phase of the treatment
and showed recovery, and also rebound of the activity, during the seco
nd part of the treatment. A screening of neurochemical markers related
to cholinergic, GABAergic and glutamatergic neurons, as well to astro
cytes and oligodendrocytes was performed in several brain regions (cer
ebellum, olfactory bulbs, cortex, striatum, hippocampus) of some of th
ese rats once they became adults. Significant alterations for all the
parameters tested, with the exception of the marker for the gluta- mat
ergic transmission, were measured in the undersized cerebellum of the
neonatally DFMO-treated rats. A shorter neonatal treatment with DFMO (
from PD 1 to 6) resulted, in the adult, in decreased cerebellar size a
nd in neurochemical alterations, both very similar to those oc curring
after the prolonged treatment. In the other brain regions a few minor
differences were noticed. The present results show that: (1) the brai
n polyamine system is differently regulated in foetuses with respect t
o newborns; (2) the effects of chronic ODC blockade are different on p
renatally or postnatally proliferating neurons, due either to a lower
sensitivity of gestationally proliferating neurons or to a subsequent
recovery; and (3) chronic postnatal ODC inhibition has a strong effect
on proliferating neurons, but little effect on further maturation of
postmitotic neurons.