The invention provides methods of screening for substances having an effect on a nicotine receptor by contacting a cell having a nicotine receptor with a test substance; and determining any increase or decrease in phosphorylation of Janus-Activated Kinase 2 (JAK2). An increase in phosphorylation of JAK2 indicates that the test substance stimulates the nicotine receptor, and wherein a decrease in phosphorylation of JAK2 indicates that the test substance inhibits the nicotine receptor. The invention also provides screening methods for identification of substances that affect nicotine receptor activity through activity mediated by the AT2 receptor. Related pharmaceutical compositions and methods of treatment are also provided.