The central effects of the adenosine analogue l-2-N6-(phenylisopropyl) adenosine (l-PIA) on breathing movements was determined by making injections into the fourth ventricle in unanesthetized fetal sheep. Administration of 0.5 μg l-PIA reduced the percent time during which fetal breathing occurred from 48.0 ± 5.2 (SEM) to 19.5 ± 6.1. Inspiratory slope was reduced to 62 ± 5.5 and 43 ± 5.7 percent of the control values when 0.2 and 0.5 μg l-PIA were given respectively. The effects of l-PIA on the percent time fetal breathing movements occurred and on inspiratory slope were prevented by the prior systemic administration of theophylline (plasma concentrations ∼15 μg/ml). When the vehicle for l-PIA, dimethyl sulfoxide in Ringer solution was given into the fourth ventricle or when 0.5 μg l-PIA was given systemically, there was no effect on fetal breathing. None of these protocols resulted in a change in sagittal sinus blood pH, PO2 or, PCO2. These data indicate adenosine acts at the brain stem to depress fetal respiratory drive.
- Adenosine, and fetal breathing
- Control of breathing, central mediators
- Fetal breathing, effect of adenosine
- Theophylline, and fetal breathing
ASJC Scopus subject areas
- Pulmonary and Respiratory Medicine