In its many embodiments, the present invention provides tetracyclic compounds of formula I or formula II (wherein the various moieties are as defined herein) useful as metabotropic glutamate receptor (mGluR) antagonists, particularly as selective metabotropic glutamate receptor 1 antagonists, pharmaceutical compositions containing the compounds, and methods of treatment using the compounds and compositions to treat diseases associated with metabotropic glutamate receptor (e.g., mGluR1) such as, for example, pain, migraine, anxiety, urinary incontinence and neurodegenerative diseases such Alzheimers disease.