As dendritic spines are the compartments showing the highest expression for GIRK, in order to determine the abundance of the three subunits in the spines located in the different dendritic subfields of CA1, we next analysed their plasma membrane distribution as a function of distance from the soma in the adult (immunoparticles/μm2; Table 1). The density of GIRK1 and GIRK2 followed a similar pattern; it was low in spines present in the proximal part of the stratum radiatum, increased significantly in the distal part of the stratum radiatum and was highest in the stratum lacunosum–moleculare (Table 1). In contrast, the density of GIRK3 was similar in the three hippocampal subfields and significantly different from that of GIRK1 and GIRK2 (Table 1).
