When pretreated with pertussis toxin (PTX), the neurites of adult rat dorsal root ganglion (DRG) cells in mixed cell cultures retract over a period of 2 h following the initial stimulus of removal from the cell culture incubator for brief periods of observation. The purpose of this investigation was to determine whether this PTX-dependent response was specific to any one of the three subpopulations of DRG neurons. However, no neurite retraction response was observed in neuron-enriched populations of cells, or in cultures enriched in isolectin B4 (IB4)-positive neurons or in IB4-negative neurons. But, the addition of non-neuronal cells, and/or medium conditioned by non-neuronal cells, was sufficient to restore the PTX-dependent neurite retraction response, but only in large diameter IB4-negative neurons. In conclusion, we have identified a regulatory response, mediated by Gi/o-proteins, which prevents retraction of neurites in large diameter IB4-negative cells of adult rat DRG. The non-neuronal cells of adult rat DRG constitutively release factor/s that can stimulate neurite retraction of a subset of isolated DRG neurons, but this property of non-neuronal cells is only observed when the Gi/o-proteins of large diameter IB4-negative cells are inhibited.