Effects of Intraocular Activity Blockade on the Morphology of Developing LGN Neurons in the Cat

Abstract

Spontaneous neuronal activity is known to play a major role in the construction and final functioning of neuronal circuits, especially those that are formed through interactions of competing inputs. The requirement for neuronal activity in the formation of highly specific connections found in the adult has been well documented in the development of the cat visual system. Shatz and Stryker (1988) and Sretavan et al. (1988) showed that prenatal intracranial infusion of the sodium channel blocker tetrodotoxin, TTX, blocks the segregation of retinogeniculate afferents into eye-specific layers in the lateral geniculate nucleus, LGN, that normally form before birth in the cat. In addition, Stryker and Harris (1986) demonstrated that the formation of the ocular dominance columns in layer 4 of the cat visual cortex can be prevented if retinal ganglion cell discharges are eliminated by intraocular injections of TTX within the critical period postnatally. These studies have clearly shown that action potential activity is required for the elimination of excessive axonal branches and the remodeling of the axonal arbor. Little, however, is known about the role of activity on dendritic development. In this paper we wished to determine whether action potential activity from the retina also influences the morphological development of the dendritic arbors of LGN neurons.