Neurotransmitter functions are typically associated with neural function rather than with development, but there is a growing body of evidence suggesting that neurotransmitters may also regulate cell proliferation and differentiation in the nervous system. Recent work has demonstrated that GABAA receptor signalling can control adult neurogenesis in the mouse. Verdon Taylor and co-workers now investigate a role for GABAB receptors in the adult mouse hippocampus (p. 83), finding that deletion or inhibition of GABAB1 promotes proliferation of neural stem cells (NSCs), whereas GABAB-receptor agonists induce NSC quiescence. These effects of manipulating GABA signalling appear to represent a cell-autonomous function for GABAB receptors in NSCs. The authors propose that GABAB may be part of a crosstalk mechanism between differentiated neurons and the progenitor population, such that neurogenesis is appropriately coordinated with neural activity. While it has yet to be determined how GABA signalling regulates NSC fate, it is increasingly clear that neurotransmitter-mediated signalling in NSCs is an important mechanism by which neurogenesis can be regulated.