GSK3B and hydrops fetalis: The finding that attenuation of GSK3β activity results in an increased heart rate response to atropine, and an increase in the bradycardia response to carbamylcholine taken together with the increased HF fraction of HRV in response to propranolol in these mice further strongly support the conclusion that GSK3β plays a critical role in regulating the autonomic balance in the Akita mouse.