Generate and Test the Reliability of a PD Model of OXT on Pupillary Hippus as a Measure of CNS Activity

Inclusion Criteria: 1. Male or female \> 18 and \< 75 years of age, Body Mass Index (BMI) \<40. 2. Generally in good health as determined by the Principal Investigator based on prior medical history, American Society of Anesthesiologists physical status 1, 2, or 3. 3. For healthy volunteers, normal blood pressure (systolic 90-140 mmHg; diastolic 50-90 mmHg) resting heart rate 45-100 beats per minute) without medication. For knee arthritis subjects, normal blood pressure or, for those with hypertension, pressure controlled with anti-hypertensives and with a resting heart rate 45-100 beats per minute. 4. Female subjects of child-bearing potential and those \< 1 year post-menopausal, must be practicing highly effective methods of birth control such as hormonal methods (e.g., combined oral, implantable, injectable, or transdermal contraceptives), double barrier methods (e.g., condoms, sponge, diaphragm, or vaginal ring plus spermicidal jellies or cream), or total abstinence from heterosexual intercourse for a minimum of 1 full cycle before study drug administration. Exclusion Criteria: 1. Hypersensitivity, allergy, or significant reaction to any ingredient of Pitocin® 2. Any disease, diagnosis, or condition (medical or surgical) that, in the opinion of the Principal Investigator, would place the subject at increased risk (active gynecologic disease in which increased tone would be detrimental e.g., uterine fibroids with ongoing bleeding), compromise the subject's compliance with study procedures, or compromise the quality of the data 3. Women who are pregnant (positive result for serum pregnancy test at screening visit), women who are currently nursing or lactating, women that have been pregnant within 2 years 4. Subjects with neuropathy, chronic pain, diabetes mellitus, or taking benzodiazepines or pain medications on a daily basis. 5. Subjects with eye pathology, eye surgery, or taking topical eye medications, or any disease process that would cause motor tremors or excessive eye movements.