Neonatal exposure to cocaine: altered dopamine levels in the amygdala and behavioral outcomes in the developing rat.
The amygdala is a brain region that is known to be implicated in the development of behavioral sensitization to cocaine. This area is often related to conditioned associations, stress responses, and anxiety; and these behaviors are usually posited to be due to altered dopamine levels. This study aimed to evaluate the effects of neonatal exposure to cocaine on the levels of neurotransmitters in the amygdala of developing rats and to relate these levels with open-field observations, mainly rearing behavior, that is regarded to reflect emotional components. Male and female Wistar rats were given 15 mg of cocaine hydrochloride/kg body weight, subcutaneously, in two daily doses, from postnatal day 1 (PND1) to PND30. Controls were given 0.9% saline. Open-field activity was registered on PND14, 21, and 30 in three sessions of 15 min each. In PND30, rats were decapitated, and the amygdala dissected from both brain hemispheres and processed for determination of dopamine (DA) and metabolites by high-performance liquid chromatography with electrochemical detection (HPLC-EC). Results show that in PND14 and 21 all registered activity behaviors were increased in male and female cocaine-exposed animals. In PND30, there was a significant decrease in rearing and in global activity in the group exposed to cocaine, and DA levels were significantly decreased in the amygdala of the same group. No differences were found between the left and right amygdala. These results suggest that chronic neonatal cocaine administration leads to depletion of DA levels in the amygdala, which is consistent with previous findings. Furthermore, the lower levels of DA are associated with decreased rearing behavior, which may indicate emotional depression. These results can help to clarify the role of amygdala in cocaine-induced behavioral sensitization in the developing rat.
Summavielle
Teresa
T
Institute of Molecular and Cell Biology (IBMC), University of Porto, Portugal. tsummavi@ibmc.up.pt
Magalhães
Ana
A
Castro-Vale
Ivone
I
de Sousa
Liliana
L
Tavares
Maria Amélia
MA
D015102:3,4-Dihydroxyphenylacetic Acid / Q000378:metabolism; D000375:Aging / Q000502:physiology*; D000679:Amygdala / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D000831:Animals, Newborn; D003042:Cocaine / Q000633:toxicity*; D004298:Dopamine / Q000378:metabolism*; D005260:Female; D008297:Male; D009043:Motor Activity / Q000187:drug effects*; D051381:Rats; D017208:Rats, Wistar
D015102:3,4-Dihydroxyphenylacetic Acid; D003042:Cocaine; D004298:Dopamine