title: Thyroid and thymus morphology in rats following sudden DRL reinforcement schedule changes.
mesh_terms: D000818:Animals; D002452:Cell Count; D003216:Conditioning, Operant; D008407:Mast Cells / Q000166:cytology; D051381:Rats; D012055:Reinforcement Schedule; D013950:Thymus Gland / Q000033:anatomy & histology* / Q000166:cytology; D013961:Thyroid Gland / Q000033:anatomy & histology* / Q000166:cytology