Infant rats with chronic neonatal isolation experience show decreased extracellular serotonin levels in ventral striatum at baseline and in response to cocaine.
Previously, we demonstrated that the early life stress of neonatal isolation enhances extracellular dopamine (DA) levels in ventral striatum in response to psychostimulants in infant rats. Yet, neonatal isolation does not alter baseline DA levels. DA levels are affected by serotonin (5-HT) and striatal levels of this transmitter are also enhanced by cocaine. Other early life stresses are reported to alter various 5-HT neural systems. Thus, the purpose of this study is to test whether neonatal isolation alters ventral striatal 5-HT levels at baseline or in response to cocaine. Litters were subjected to neonatal isolation (1-h individual isolation/day on postnatal days 2-9) or to non-handled conditions and pups assigned to one of three cocaine doses (0, 2.5, or 5.0 mg/kg) groups. On postnatal day 10, probes were implanted in the ventral striatum. Dialysate samples obtained over a 60-min baseline period and for 120 min post cocaine injections were assessed for levels of 5-HT and its metabolite, 5-HIAA. ISO decreased ventral striatal 5-HT levels at baseline and after cocaine administration but did not alter 5-HIAA levels. These data add to the literature on the immediate effects of early life stress on 5-HT systems by showing alterations in the ventral striatal system. Because serotonergic effects in this neural area are associated with reward and with emotion and affect regulation, the results of this study suggest that early life stress may be a risk factor for addiction and other psychiatric disorders.
Kosten
Therese A
TA
Yale University School of Medicine, Ribicoff Research Facilities, Room S-305 CMHC, 34 Park Street, New Haven, CT 06508, USA. therese.kosten@yale.edu
Zhang
Xiang Yang
XY
Kehoe
Priscilla
P
D000818:Animals; D000831:Animals, Newborn; D001479:Basal Ganglia / Q000378:metabolism*; D016739:Behavior, Addictive / Q000503:physiopathology; D003042:Cocaine / Q000494:pharmacology*; D018765:Dopamine Uptake Inhibitors / Q000494:pharmacology*; D005260:Female; D006897:Hydroxyindoleacetic Acid / Q000378:metabolism; D008297:Male; D017551:Microdialysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D012701:Serotonin / Q000378:metabolism*; D012934:Social Isolation / Q000523:psychology*
D018765:Dopamine Uptake Inhibitors; D012701:Serotonin; D006897:Hydroxyindoleacetic Acid; D003042:Cocaine