The present application relates methods for treating a depressive symptom comprising administering an effective amount of a opioid receptor agonist or a pharmaceutically acceptable salt thereof to a subject in need thereof. Non-limiting examples of such agonist include the compounds of Formulas I, II, III, and IV, as well as the compounds of Table A.

In one aspect, the invention provides compounds of Formula I: (I) and pharmaceutically acceptable salts and solvates thereof, wherein R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, Y, Z.sub.a are defined as set forth in the disclosure. The invention also provides compounds of any one of Formulae II to VII, IA to IC, and IIA to IIC, and pharmaceutically acceptable salts and solvates thereof. Other aspects of the invention include the use of compounds of Formulae I to VII, IA to IC, and IIA to IIC, and pharmaceutically acceptable salts and solvates thereof for the treatment of disorders responsive to modulation of one or more opioid receptors. In certain embodiments, the Compounds of the Invention are useful for treating pain.

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The present application relates methods for treating a depressive symptom comprising administering an effective amount of a opioid receptor agonist or a pharmaceutically acceptable salt thereof to a subject in need thereof. Non-limiting examples of such agonist include the compounds of Formulas I, II, III, and IV, as well as the compounds of Table A.

The present application relates methods for treating a depressive symptom comprising administering an effective amount of a opioid receptor agonist or a pharmaceutically acceptable salt thereof to a subject in need thereof. Non-limiting examples of such agonist include the compounds of Formulas I, II, III, and IV, as well as the compounds of Table A.

The present application relates methods for treating a depressive symptom comprising administering an effective amount of a opioid receptor agonist or a pharmaceutically acceptable salt thereof to a subject in need thereof. Non-limiting examples of such agonist include the compounds of Formulas I, II, III, and IV, as well as the compounds of Table A.

The present application relates methods for treating a depressive symptom comprising administering an effective amount of a opioid receptor agonist or a pharmaceutically acceptable salt thereof to a subject in need thereof. Non-limiting examples of such agonist include the compounds of Formulas I, II, III, and IV, as well as the compounds of Table A.