Effects of serotonin re-uptake inhibition on ventilatory control in goats

Fluoxetine (Prozac(R)) inhibits serotonin (5-HT) re-uptake, thereby enhancing serotonergic effects. Since serotonin is known to affect ventilation in a variety of circumstances, we investigated the effects of chronic serotonin re-uptake inhibition with fluoxetine on selected ventilatory responses including: (1) eupnea; (2) the hypercapnic ventilatory response at rest; (3) the exercise ventilatory response and (4) repeated trials of hypercapnic exercise. Ventilatory and arterial blood gases were measured in goats (n = 5) at rest, during steady-state treadmill exercise, and during successive rest:exercise trials with increased respiratory dead space (0.4-0.6 L). Fluoxetine was administered (greater than or equal to 4 weeks, 1 mg/kg, SQ, SID) and protocols were repeated. Following fluoxetine, Pa-CO2 was increased in most conditions studied: however, no differences were seen in exercise Pa-CO2 regulation or ventilatory responses pre- versus post-fluoxetine. We conclude that chronic fluoxetine slightly depresses respiratory control at rest, but, has minimal effects during exercise or with mild hypercapnia during rest or exercise in goals. (C) 1999 Elsevier Science B.V. All rights reserved.