Increase in the cholinergic cardiac plexus in sympathetically aneural chick hearts

Embryonic chick hearts were made sympathetically aneural by removal of premigratory neural crest over somites 10-20. The cholinergic cardiac plexus was assessed at 12 to 15 days of incubation using morphological and biochemical techniques. The cholinergic innervation to the heart was increased by 50 to 100% due to both hypertrophy and hyperplasia of the ganglion cells as well as their terminals. The additional cells were an expansion of the normal population of cholinergic neurons in the heart rather than from some extra source. The expanded population of neurons did not express an adrenergic phenotype in response to the absence of adrenergic cardiac innervation.