Maturation of membrane properties of neurons in the rat deep cerebellar nuclei

Abstract

Patch clamp recordings of neurons in the adult rat deep cerebellar nuclei have been limited by the availability of viable brain slices. Using a new slicing technique, this study was designed to explore the maturation of membrane properties of neurons in the deep cerebellar nuclei (DCN)-an area involved in rat eyeblink conditioning. Compared to whole-cell current-clamp recordings in DCN in rat pups at postnatal day 16 (P16) to P21, recordings from weanling rats at P22-P40 revealed a number of significant changes including an increase in the amplitude of the afterhyperpolarization (AHP)-an index of membrane excitability which has been shown to be important for eyeblink conditioning-a prolonged interval between the first and second evoked action potential, and an increase in AHP amplitude for hyperpolarization-induced rebound spikes. This is the first report of developmental changes in membrane properties of DCN which may contribute to the ontogeny of eyeblink conditioning in the rat.

Keywords: after-hyperpolarization; cerebellar nuclear neurons; developmental changes; maturation; membrane property.

Fig. 1. Typical recordings of evoked APs by depolarizing current injection in DCN neurons

Left panel (Top, middle, and bottom) represents typical whole-cell current clamp recordings with depolarizing current injection of 0.1nA in DCN neurons from P19, P24, and P29 rats, respectively. Right top panel represents the corresponding APs. Right bottom panel represents AP measures taken.

Fig. 2. Developmental changes in APD, AP rising phase, AP falling phase, AHP amplitude, and S1S2 interval

A-E represent the measurements taken for APD, AP rising phase, AP falling phase, AHP amplitude, and S1S2 interval, respectively. Note that each point in the graphs represents the result from a single neuron, and dash line illustrates the average at a given age. A shortening of APD, AP rising phase, and AP falling phases but increased AHP amplitude, prolonged S1S2 interval were observed in post-weaning group.

Fig. 3. Developmental changes in membrane properties happened at P22-25

A-D represent the measurements taken for APD, AP falling phase, AHP amplitude, and S1S2 interval, respectively. Note that each point in the graphs represents the result from a single neuron, and dash line illustrates the average at a given age. The developmental changes happened on P22-25 (weaning age).

Fig. 4. Developmental changes in AHP amplitude of DCN rebound spikes elicited by hyperpolarization pulses

A represents typical rebound spikes elicited by hyperpolarization current injection of -0.5nA in DCN neurons from P19, P24, and P29 rats, respectively. B represents AHP amplitude of rebound spikes from P16-21 group, and P22-40 group, respectively. C represents AHP amplitude of rebound spikes from P16-21 group, P22-25 group, and P26-40 group, respectively. Note that each point in the graphs represents the result from a single neuron, and dash line illustrates the average at a given age. The developmental changes happened on P22-25 (weaning age).