[Changes in electrophysiological and morphological properties of neuron in the ventral partition of medial geniculate body during the postnatal development of rats].

We investigated the electrophysiological and morphological characteristics of the neurons in the ventral partition of medial geniculate body (MGBv) in the rat during postnatal development (postnatal day 3-30, P3-30) with whole-cell patch clamp recording and intracellular labeling technique. The results are as follows: (1) There was an increase in the negativity of the resting membrane potential, a decrease in the input resistance and the time constant of the MGBv neurons of rats during the postnatal development; the amplitude, threshold and duration of the action potentials were also different on different postnatal days; (2) During the postnatal development, the changes in voltage-dependent ion channels dramatically influenced the waveform of action potential in the MGBv neurons. Application of 4-AP, a K(+)-channel blocker, reduced the amplitude and prolonged the durations of the action potentials in P6 neurons, and inactivated the neurons at the end of the pulse in P16 rats. Application of CdCl2 to block the voltage-dependent Ca(2+)-channel decreased the amplitude and increased the duration of the action potential in P16 rats; (3) Biocytin staining revealed that immature MGBv cell had smaller somata and short, simple dendritic aborization. During postnatal development, the matured neurons had oval somata and 3-4 primary dendrities that radiated irregularly and projected outside the section; spines also appeared on the dendrites of the mature neurons. These results reveal that the morphologic and electrophysiological properties are not matured during early postnatal development, and that the electrophysiological and morphological features of the developing MGBv neurons are interrelated.