Homogeneous distribution of excitatory and inhibitory synapses on the dendrites of the cat surea triceps α-motoneurons increases synaptic efficacy: Computer model

The effects of input distribution in dendrites on postsynaptic inhibition of spinal monosynaptic reflex were studied in morphologically and physiologically characterized α-motoneurons. In homogeneous (HOM) and heterogeneous (HEM) models, the location of the excitatory and inhibitory synapses was randomly selected for each bin of dendritic length. In the HOM, each compartment was forced to contain only one synapse as long as other compartments did not have at least one synapse. In the HEM, no restriction was made for synaptic distribution within a bin. EPSP amplitude in the HOM was enhanced by 28% and inhibition of EPSP peak (upon activation of inhibition) was increased by 66%, compared to the HEM. These results indicate that synaptic efficacy is greater in the HOM, both for excitatory and inhibitory synapses. Thus, it is suggested that homogeneously distributed postsynaptic inhibition may serve as the powerful inhibition of the monosynaptic reflex in realistic α-motoneurons.