Fixed-ratio level pressing by VMH rats: work vs accessibility of sucrose reward.
D000818:Animals; D001835:Body Weight; D003216:Conditioning, Operant / Q000502:physiology*; D005260:Female; D007031:Hypothalamus / Q000502:physiology*; D007033:Hypothalamus, Middle / Q000502:physiology*; D051381:Rats; D012055:Reinforcement Schedule; D012201:Reward