Cocaine stimulation of ovine fetal swallowing

Abstract

Cocaine acts to block reuptake of neurotransmitters, resulting in elevated intra-synaptic norepinephrine levels. As monoaminergic systems may contribute to central regulation of swallowing motor activity as well as dipsogenic responses, and cocaine is known to alter fetal behavior, we examined the effect of intravenous cocaine on fetal swallowing. Six ovine fetuses (130 ± 1 days) were chronically prepared with esophageal electrodes and an esophageal flow probe. Following a 1-h control period, fetuses received an intravenous injection of 1.0 mg/kg cocaine over 30 s. Fetal blood samples were withdrawn at timed intervals and fetal swallowing activity was monitored for 180 min after the cocaine bolus. Basal fetal swallowing activity during the control period was 0.6 ± 0.1 swallows/min, with esophageal flow of 0.3 ± 0.1 ml/min. At 10 min following cocaine, fetal swallowing rate increased to 1.4 ± 0.4 swallows/min though esophageal flow did not change significantly (0.4 ± 0.2 ml/min). Swallowing rate then returned to basal levels. Fetal heart rate increased in response to cocaine injection (149 ± 14 to 174 ± 24 bts/min at 180 min) though there was no change in fetal mean blood pressure. These results demonstrate acute stimulation of fetal swallowing activity in response to intravenous cocaine injection. Together with previous reports, these data further illustrate the diversity of fetal behavioral effects in response to in utero cocaine exposure.