Developmental changes in physiological properties in the rat's dorsal nucleus of the lateral lemniscus.

To better understand the development of the dorsal nucleus of the lateral lemniscus (DNLL), intrinsic membrane properties and synaptic responses of DNLL neurons in brain slice preparations were examined. Intracellular recordings were taken from DNLL neurons of rat pups at postnatal days 4-8 (early group), 10-12 (intermediate group) and 16-18 (late group). In response to positive current injection, neurons in the early group displayed firing with lower frequency and a longer action potential duration in comparison to the intermediate and late groups. The action potential amplitude of DNLL neurons increased during development. Postsynaptic potentials (PSPs), with excitatory predominance, were elicited by electrical stimulation of the lateral lemniscus and commissure of Probst throughout the three age groups. Neurons showed a longer latency and rise time of the PSPs in the early group in comparison with those in the intermediate and late groups. These results suggest that the early DNLL neurons display physiological characteristics associated with immature neurons, while the other two groups tend to illustrate mature-like neuronal properties. Furthermore, it seems that the neurons at day 10-12 are in a transitional period of development, which coincides with the onset of hearing.