Abstract
Background: It has been hypothesized that adverse early experience may be a mechanism
by which children become vulnerable to later psychopathology via alteration of neurochemical
or hormonal systems associated with such disorders. Such effects may in turn affect
later responses to pharmacologic agents that act on these systems.
Methods: In this study, 18 mother-reared (MR) and 18 peer-reared (PR) rhesus monkeys
experienced six 1-week separations from cagemates interspersed with 1-week reunions,
while housed in like-reared groups of 3. Within rearing groups, equal numbers of animals
received either fluoxetine (2 mg/kg), desipramine (5 mg/kg) or placebo delivered daily
beginning 4 weeks before the first separation. Levels of norepinephrine (NE), the
NE metabolite MHPG, the dopamine metabolites DOPAC and HVA, and the serotonin metabolite
5HIAA were measured in CSF samples collected approximately every 2 to 3 weeks during
these procedures.
Results: Following treatment, DMI increased NE and decreased MHPG in the DMI-treated
groups, while 5HIAA was decreased in the fluoxetine-treated groups following treatment.
The increase in NE was followed by a sharp decline over the course of treatment, which
was accompanied by an increase in MHPG. The rearing groups did not show a differential
response to the drug treatments, and the separation manipulation itself had few effects.
The mother-reared group showed higher levels of NE and DOPAC over all samples and
higher levels of HVA in most samples.
Conclusions: These rearing effects on biogenic amine activity were observed even in
the presence of pharmacologic treatments that effectively altered the activity of
these systems, and are consistent with previous findings from the same subject. The
higher NE values observed in mother-reared infants over separations and reunions may
have been due to higher basal levels of NE than peer-reared monkeys or to greater
responsiveness to the stress of repeated social disruption or both. These findings
agree with other primate studies showing that rearing differences persist beyond the
infancy period and add to growing evidence of the important influence of the early
social environment on neurobiologic development in primates.
Keywords
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Article info
Publication history
Accepted:
January 22,
1999
Received in revised form:
January 8,
1999
Received:
August 4,
1998
Identification
Copyright
© 1999 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.
