ROLE OF AUTOINHIBITORY FEEDBACK IN CARDIAC SYMPATHETIC TRANSMISSION

Abstract

The relationship between two indices of transmitter release measured simultaneously and the frequency of 4 field pulses (0.125-2 Hz) were obtained from superfused guinea pig right atria after labelling with 3H-noradrenaline. The relationships between 3H-efflux or rate responses and frequency were hyperbolic. Autoinhibitory feedback did not play a role since phentolamine (1 microM) did not alter the 3H-efflux or rate responses to 4 field pulses that gave 50-60% of the maximum rate response. In the presence of neuronal uptake block (desipramine (0.1 microM) phentolamine enhanced 3H-efflux and rate responses to 4 field pulses at all frequencies. In the absence of desipramine prolonged trains of..