Bisphenol A attenuates phenylbiguanide-induced cardio-respiratory reflexes in anaesthetized rats

Bisphenol A (BPA), a toxic chemical released from plastics, produces respiratory arrest and hypotension after a latency. The latency was similar to the reflex apnoea induced by the vagal C fibre stimulation. Therefore, the present study was undertaken to examine the effects of chronic and acute exposure to BPA on cardio-respiratory reflexes elicited by phenylbiguanide (PBG). Acute and chronic experiments were performed on adult female rats. In chronic experiments, the animals were ingested with pellets containing BPA (2 μg/kg body weight) or without BPA (time-matched control) for 30 days. Subsequently, the animals were anaesthetized and prepared for recording blood pressure, ECG and respiratory excursions. PBG was injected through jugular vein to evoke reflexes in these animals. In acute experiments, the PBG reflexes were obtained before and after injecting BPA/ethanol. Also vagal afferent activity was recorded in some rats. In time-matched control rats, PBG produced bradycardia, hypotension and tachypnoea over a period of time. The maximal changes were around 50-65%. In BPA treated group, the PBG-induced heart rate and respiratory frequency changes were attenuated significantly. Acute exposure of animals to BPA (35 mg/kg body weight) for 30 min also attenuated the PBG-induced responses significantly. The attenuation of the PBG reflex responses by BPA in acute experiments was associated with decreased vagal afferent activity. The present results indicate that BPA attenuates the protective cardio-respiratory reflexes due to decreased vagal afferent activity.