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The dorso-ventral and developmental gradients of entorhinal layer II cell grid properties correlate with their resonance properties and with their hyperpolarization-activated cyclic nucleotide-gated ion channel current (HCN, Ih) characteristics. We investigated whether such correlation existed in rat hippocampal CA1 pyramidal cells, where place fields also show spatial and temporal gradients. Resonance was absent during the first postnatal week, and emerged during the second week. Resonance was stronger in dorsal than ventral cells, in accord with HCN current properties. Resonance responded to cAMP in ventral but not in dorsal cells. The dorso-ventral distribution of HCN1 and HCN2 subunits and of the auxiliary protein tetratricopeptide repeat-containing Rab8b-interacting protein (TRIP8b) could account for these differences between dorsal and ventral cells. The analogous distribution of the intrinsic properties of entorhinal stellate and hippocampal cells suggests the existence of general rules of organization among structures that process complementary features of the environment.

Background:Information is differentially processed in the dorsal versus ventral hippocampus. Results: Expression levels of Kv4.2 and HCN1 varied and conferred distinct integrative properties to CA1 pyramidal cell dendrites in dorsal and ventral hippocampus. Conclusion: Molecular and physiological differences provide the basis for the specific properties of dorsal and ventral CA1 pyramidal cells. Significance: Channel expression and function enable specific processing roles.

Background: Gamma knife surgery (GKS) is used at subnecrotic doses for temporal lobe epilepsy (TLE) treatment. Rat models of TLE have been used to probe the mechanisms underlying GKS. Previous GKS studies on rats have used the Leksell GammaPlan® (LGP) treatment planning system to determine the irradiation time to achieve the dose to deliver. Since LGP is not designed for such small structures, it is important to calibrate the system for the rat brain. Methods: We have used a Monte Carlo simulation (MCS) radiation transport scheme, with CT data as anatomical and tissue-specific information, to simulate the dose distribution in a rat brain when using a Leksell Gamma Knife®. Results: We show how dose distributions obtained by MCS quantitatively compare to those predicted by LGP, and discuss whether LGP should be used for studies involving rats. The energy deposited when using the 4-mm collimators was calculated for targets on both sides of the rat brain in the dorsal hippocampus, which allowed us to determine the exact time to irradiate rats with a given dose. Conclusion: The MCS method used in this study can easily be used for future GKS studies on small animals when accurate dose distributions are required.