Chronic cocaine administration and withdrawal of cocaine modify neurotensin binding in rat brain.
Neurotensin (NT) is a peptide colocalized with dopamine (DA) within some mesocorticolimbic DA neurons that are affected by cocaine. We assessed whether chronic treatment with cocaine and withdrawal from cocaine would alter NT binding within these and other areas in the brain. Rats were given infusions repeatedly of isotonic saline or cocaine (1 mg/kg i.v. every 12 min for 2 hr over 10 days) and then were killed within 15 min of the last treatment session ("cocaine" or "saline") or 10 days later ("withdrawal"). Brains were processed for NT receptor autoradiography. Cocaine affected NT binding in the mesocortical regions differently from other areas. Within the mesocorticolimbic system, NT binding in the parabrachial pigmented nucleus of the ventral tegmental area (VTA) was 67% lower in cocaine-treated rats killed immediately after or 10 days after their final infusion than in rats given saline. In contrast to the perikaryal region, significantly more NT binding occurred postsynaptically in the terminal areas of the VTA (prefrontal cortex [PFC] and substantia nigra, pars compacta) 10 days after withdrawal of cocaine than in the saline controls. NT binding in the nucleus accumbens was unaffected by cocaine or its withdrawal. Cocaine also decreased NT binding in non-mesocorticolimbic areas, including the dorsal hypothalamic area and the zona incerta, but binding returned toward control levels 10 days after withdrawal from cocaine. These data suggest that in central areas poor in DA uptake sites such as the PFC, NT may be a critical element in the inactivation of DA. Chronic cocaine treatment and its withdrawal appear to uncouple the normal NT-DA interaction at both the cell bodies and terminals.(ABSTRACT TRUNCATED AT 250 WORDS)
Pilotte
N S
NS
Addiction Research Center, National Institute on Drug Abuse, Baltimore, Maryland 21224.
Mitchell
W M
WM
Sharpe
L G
LG
De Souza
E B
EB
Dax
E M
EM
D000818:Animals; D001665:Binding Sites; D001921:Brain / Q000378:metabolism*; D003042:Cocaine / Q000494:pharmacology*; D008297:Male; D009496:Neurotensin / Q000378:metabolism*; D051381:Rats; D011917:Rats, Inbred Lew; D013375:Substance Withdrawal Syndrome / Q000378:metabolism*; D013997:Time Factors; D014018:Tissue Distribution
D009496:Neurotensin; D003042:Cocaine