Developmental Neurobiology

Starburst Network Goes from Excitatory to Inhibitory

Science's STKE  07 Dec 2004:
Vol. 2004, Issue 262, pp. tw442
DOI: 10.1126/stke.2622004tw442

During development, the action of γ-aminobutyric acid (GABA) changes from an excitatory neurotransmitter to an inhibitory one. Zheng et al. show that, in starburst neurons of the developing mammalian retina [rabbits, embryonic day 29 (E29) to postnatal day 1 (P1)], a single neuron releases both acetylcholine (ACh) and GABA. The nicotinic ACh synaptic activity diminished during development so that after P11, the time when the rabbits' eyes opened, only GABAergic responses were detectable. At the same time that these nicotinic cholinergic synapses were being eliminated, the starburst cell morphology was also changing to one with numerous varicosities. Pharmacological analysis coupled with electrophysiological recordings indicated that the spontaneous retinal waves associated with the starburst cells at the early stages of development (E30) were the result of mutual nicotinic cholinergic excitation among the starburst cells. In cells from P8 animals, GABA input became inhibitory, and the retinal waves were insensitive to nicotinic antagonists and were then mediated by glutamatergic synaptic interactions. After eye opening, GABA mediated light-evoked synaptic inhibition among neighboring starburst cells. Thus, the conversion of GABA synaptic activity from excitatory to stimulatory and the elimination of nicotinic ACh activity change the character of the retinal starburst synaptic network from one with recurrent spontaneous rhythmic activity to a stable network.

J.-J. Zheng, S. Lee, Z. J. Zhou, A developmental switch in the excitability and function of the starburst network in the mammalian retina. Neuron 44, 851-864 (2004). [Online Journal]