CHRONIC CONTINUOUS OR INTERMITTENT INFUSION OF COCAINE DIFFERENTIALLYALTER THE CONCENTRATION OF NEUROTENSIN-LIKE IMMUNOREACTIVITY IN SPECIFIC RAT-BRAIN REGIONS
St. Cain et al., CHRONIC CONTINUOUS OR INTERMITTENT INFUSION OF COCAINE DIFFERENTIALLYALTER THE CONCENTRATION OF NEUROTENSIN-LIKE IMMUNOREACTIVITY IN SPECIFIC RAT-BRAIN REGIONS, Neuropsychopharmacology, 8(3), 1993, pp. 259-265
Neurotensin (NT) is an endogenous brain tridecapeptide that exhibits s
elective anatomic and neurochemical interactions with rat brain dopami
nergic systems. Because modulation of dopaminergic neurotransmission m
ay underlie many of the behavioral properties of cocaine, the effects
of both acute and chronic administration of cocaine on the concentrati
on of NT-like immunoreactivity (NT-LI) in specific brain regions was d
etermined. Adult male rats were treated with cocaine for 14 days at a
dose of 40 mg/kg/day (0.118 mmoles/kg/day) administered as either 1 su
bcutaneous injection per day, or infused continuously using subcutaneo
usly implanted minipumps. Neurotensin-like immunoreactivity in specifi
c brain regions was then measured 24 hours or 8 days following drug ad
ministration. After 24 hours of withdrawal from daily subcutaneous inj
ection, the concentration of NT-LI was significantly increased in the
substantia nigra (SN) and frontal cortex. After 24 hours of withdrawal
from continuous infusion with cocaine, NT-LI was increased only in th
e SN. After 8 days of withdrawal, NT-LI was increased in the SN of rat
s treated with daily subcutaneous injections of cocaine, but not in th
e group treated with continuous infusion. Twenty-four hours following
a single acute injection of 40 mg/kg of cocaine, NT-LI was increased i
n the SN and nucleus accumbens. These results provide evidence consist
ent with a neuroanatomically selective involvement of NT systems in th
e behavioral and/or addictive properties of cocaine.