Aims: 

It is well known that persistent inward currents (PICs) could trigger all-or none plateau potentials and self-sustained firing in motoneurones. It was demonstrated this PIC was mediated by a particular subgroup of L-type Ca²⁺channels, the Cav1.3 channel. The goal of this study is to investigate the distribution of Cav1.3-immunoreractive (Cav1.3-IR) neurons in different spinal segments as well as in the brain stem in the rat.

Methods: 

This issue is studied by immunohistochemistry. The immunostaining was performed using a polyclonal antibody to a segment of the a-1D subunit of rat brain voltage-gated calcium channel. Eight adult male Wistar rats were used. Four of the animals were used for retrograde labelling of tail motoneurons in the spinal cord by injecting fluorogold into tail muscles. Selected segments from the whole spinal cord and brain stem were investigated.

Results: 

Cav1.3-IR neurons were found in the all the segments of the spinal cord, particularly in the ventral horn including the motor nuclei. In the brain stem Cav1.3- IR neurons were observed in many nuclei including all cranial motor nuclei, many sensory nuclei as well as some reticular nuclei and raphe nuclei. In retrograde labelled spinal motoneurons the Cav1.3-IR labelling is seen at the soma and proximal dendrites; few, if any, distal dendrites were labelled.

Conclusion: 

These results in rat's spinal cord are very similar to the cat but differ from studies in mouse and turtle motoneurons where the immunoreactivity against these channels was described to localise to the (distal) dendrites.