Injection of
2-deoxy-D-glucose (2DG) elicits both
analgesic and hyperphagic responses in rats. While pituitary dysfunction, decreased
dopamine availability, or neonatal
monosodium glutamate treatment decreases 2DG
hyperphagia, they increase 2DG
analgesia. In contrast, 2-DG
analgesia alone is decreased by repeated 2-DG
injections, while 2-DG
hyperphagia alone is decreased following
naloxone pretreatment. The present four experiments examined further mechanisms subserving these two induced responses. In the first experiment, rats were deprived of food for 6 h following 2-DG (600 mg/kg). While 2-DG
hyperphagia persisted in the absence of glucoprivation, 2-DG
analgesia failed to occur after this delay. In the second experiment, acute exposure to inescapable foot
shock (4 mA, 0.5 s/5 s for 1 h) preceded administration of 2-DG (600 mg/kg). While 2-DG
hyperphagia was eliminated by this procedure, 2-DG
analgesia was significantly potentiated. In the third experiment, repeated
morphine (10 mg/kg)
injections over 14 days eliminated 2-DG
analgesia on the fifteenth day, but failed to affect 2-DG
hyperphagia. In the fourth experiment, lesions placed in either the lateral hypothalamus or zona incerta decreased 2-DG
hyperphagia, but failed to affect 2-DG
analgesia. These results are discussed in terms of common and dissociative mechanisms mediating both responses.