After placement of a high resolution impedance manometry catheter (transnasally), citalopram will be administered IV over 30 minutes (20 mg in 100ml saline). Thereafter, the investigators will wait for 20 minutes, after which the volunteers will receive 10 wet swallows (5ml saline), to investigate esophageal peristalsis. Thereafter, a standard meal (1000kcal) will be given to the volunteers and recordings will continue for another 2 hours.

After placement of a high resolution impedance manometry catheter (transnasally), placebo (saline 100ml) will be administered IV over 30 minutes. Thereafter, the investigators will wait for 20 minutes, after which the volunteers will receive 10 wet swallows (5ml saline), to investigate esophageal peristalsis. Thereafter, a standard meal (1000kcal) will be given to the volunteers and recordings will continue for another 2 hours.

Citalopram HCl IV 20 mg in 100 ml saline will be infused IV over the course of 30 minutes. Volunteers will receive a standard meal, and recordings using high resolution impedance manometry, will be continued for 2 hours.

The investigators will measure lower esophageal sphincter pressure after a meal between placebo and citalopram, using a high resolution impedance manometry system. LES pressures will be measured in the first hour postprandial and will be compared (preprandial vs postprandial hour 1).

The investigators will measure the number of reflux episodes after a meal between placebo and citalopram, using a high resolution impedance manometry system.

The investigators will measure the number of transient lower esophageal sphincter relaxations after a meal between placebo and citalopram, using a high resolution impedance manometry system.