Downregulation decreases neurotransmitter receptors, whereas upregulation increases receptors. Sensitivity to molecules decreases with downregulation. Smoking anything containing nicotine can cause upregulation, necessitating more nicotine to obtain similar effects. Additionally, note that nicotine has an affinity for the hemoglobin molecule, which is on the red blood cell carrying oxygen to every cell in our body. Nicotine takes the place of approximately half of the oxygen molecules on hemoglobin. Remember that oxygen is life and life ends when our oxygen supply ends. In ischemia, lack of oxygen perfusing or circulating to tissue and vital organs, cells can die. If this sounds scary, it’s because it is! If you’re serious about stopping smoking—do it! Read the book, “The Little Engine That Could,” each night for 30 days. You can do anything with a changed and made up mind.