COCULTURES OF ADULT VENTRICULAR MYOCYTES WITH STELLATE GANGLIA OR INTRINSIC CARDIAC NEURONS FROM GUINEA-PIGS - SPONTANEOUS ACTIVITY AND PHARMACOLOGICAL PROPERTIES

Objective: The aim was to develop long term primary cocultures of adult ventricular myocytes with autonomic neurones dissociated from stellate or intrinsic cardiac ganglia. This was to provide an experimental model for the investigation of the regulatory role of autonomic neurones with respect to cardiac myocyte function. Methods: Ventricular myocytes and stellate and intrinsic cardiac neurones were enzymatically dissociated from adult male guinea pigs and plated together on 13 mm cover slips; the cultures were maintained in an incubator for two to 10 weeks. The electrical properties of cultured myocytes and neurones were investigated by means of a conventional microelectrode technique and the spontaneous contractile activity of the myocytes was recorded by a video system. The electrical, contractile, and pharmacological properties of myocyte-neuronal networks were investigated by superfusing the cultures with various neuromodulators and blockers. Results: The electrical properties of the cultured myocytes and neurones were similar to those reported in other in vitro studies. Innervated and non-innervated cardiomyocyte cultures responded differently, however, to various pharmacological interventions. Spontaneous contractions were attenuated by tetrodotoxin (4X10(-7) M), beta adrenergic blockade, and nicotinic blockade more in cocultures than in cardiac myocyte cultures alone. On the other hand, the beta agonist isoproterenol increased the spontaneous beating in both types of cocultures more than in myocytes alone. The effects of the muscarinic agonist bethanechol and the muscarinic blocker atropine were not significantly different in innervated and non-innervated cultures. Nicotine induced either an increase or decrease in contractile rates of both cocultures and did not affect non-innervated myocyte cultures. Conclusions: Cocultures of myocytes and autonomic neurones alter the responses of myocytes relative to cultures without neurones. The results suggest that functional contacts can be established between adult myocytes.and dissociated neurones in primary cultures. Contractile rates of such myocyte cultures are influenced by the presence of neurones. Neurones innervating these cultures were modified by beta adrenergic, muscarinic, and nicotinic