Functional interdependence of neurons in a single canine intrinsic cardiacganglionated plexus

1. To determine the activity characteristics displayed by different subpopu lations of neurons in a single intrinsic cardiac ganglionated plexus, the b ehaviour and co-ordination of activity generated by neurons in two loci of the right atrial ganglionated plexus (RAGP) were evaluated in 16 anaestheti zed dogs during basal states as well as in response to increasing inputs fr om ventricular sensory neurites. 2. These sub-populations of right atrial neurons received afferent inputs f rom sensory neurites in both ventricles that were responsive to local mecha nical stimuli and the nitric oxide donor nitroprusside. Neurons in at least one RAGP locus were activated by epicardial application of veratridine, br adykinin, the beta (1)-adrenoceptor agonist prenaterol or glutamate. Epicar dial application of angiotensin II, the selective beta (2)-adrenoceptor ago nist terbutaline and selective alpha -adrenoceptor agonists elicited incons istent neuronal responses. 3. The activity generated by both populations of atrial neurons studied ove r 5 min periods during basal states displayed periodic coupled behaviour (c ross-correlation coefficients of activities that reached, on average, 0.88 +/- 0.03; range 0.71-1) for 15-30 s periods of time. These periods of coupl ed activity occurred every 30-50 s during basad states, as well as when neu ronal activity was enhanced by chemical activation of their ventricular sen sory inputs. 4. These results indicate that neurons throughout one intrinsic cardiac gan glionated plexus receive inputs from mechano- and chemosensory neurites loc ated in both ventricles. That such neurons respond to multiple chemical sti muli, including those liberated from adjacent adrenergic efferent nerve ter minals, indicates the complexity of the integrative processing of informati on that occurs within the intrinsic cardiac nervous system. 5. It is proposed that the interdependent activity displayed by populations of neurons in different regions of one intrinsic cardiac ganglionated plex us, responding as they do to multiple cardiac sensory inputs, forms the bas is for integrated regional cardiac control.