The Journal of Neuroscience, September 15, 1998, 18(18):7502-7510
Food Restriction Enhances the Central Rewarding Effect of
Abused Drugs
Soledad
Cabeza de Vaca and
Kenneth
D.
Carr
Millhauser Laboratories, Department of Psychiatry, New York
University Medical Center, New York, New York 10016
Chronic food restriction increases the systemic self-administration
and locomotor-stimulating effect of abused drugs. However, it is not
clear whether these behavioral changes reflect enhanced rewarding
potency or a CNS-based modulatory process. The purpose of this study
was to determine whether food restriction specifically increases the
rewarding potency of drugs, as indexed by their threshold-lowering
effect on lateral hypothalamic self-stimulation, and whether any such
effect can be attributed to an enhanced central response rather than
changes in drug disposition. When drugs were administered systemically,
food restriction potentiated the threshold-lowering effect of
amphetamine (0.125, 0.25, and 0.5 mg/kg, i.p.), phencyclidine (1.0, 2.0, and 3.0 mg/kg, i.p.), and dizocilpine (MK-801) (0.0125, 0.05, and
0.1 mg/kg, i.p.) but not nicotine (0.15, 0.3, 0.45 mg/kg, s.c.). When
amphetamine (25.0, 50.0, and 100.0 µg) and MK-801 (5.0, 10.0, and
20.0 µg) were administered via the intracerebroventricular route,
food restriction again potentiated the threshold-lowering effects and
increased the locomotor-stimulating effects of both drugs. These
results indicate that food restriction increases the sensitivity of
neural substrates for rewarding and stimulant effects of drugs. In
light of work that attributes rewarding effects of MK-801 to blockade
of NMDA receptors on medium spiny neurons in nucleus accumbens, the
elements affected by food restriction may lie downstream from the
mesoaccumbens dopamine neurons whose terminals are the site of
amphetamine-rewarding action. Possible metabolic-endocrine triggers of
this effect are discussed, as is the likelihood that mechanisms
mediating the modulatory effect of food restriction differ from those
mediating sensitization by intermittent drug exposure.
Key words:
food restriction; sensitization; reward; locomotion; amphetamine; MK-801; self-stimulation
Copyright © 1998 Society for Neuroscience 0270-6474/98/18187502-09$05.00/0