Distribution of T-type calcium channels in LGN interneurons

INs form inhibitory synapses on the TCNs, and have presynaptic terminals in the dendrites as well as the soma. These various locations of sites make them special, and somatic IN activity may thus be a result of either axonal or dendritic GABA release onto TCNs. Dendritic sites of GABA release are most often located in the distal dendrites of the INs, as part of triadic synapses elsewhere in the brain. In these triads, both presynaptic and postsynaptic terminals of INs lie close to each other. If a terminal receives strong enough visual input from retinal ganglion neurons (RGNs), GABA release can be locally triggered at the very same site without somatic involvement. GABA release from these dendritic sites may also be triggered by somatic activity of INs. The function of having multiple release possibilities is not fully understood, and nei- ther are the conditions for GABA release in these sites. In order to gain understanding of this, more knowledge of the two-way communication between distal dendrites and the soma is crucial. T-type calcium channels (IT -channels) are important for achieving firing in thalamic cells. The distribution of IT -channels on the somatodendritic membrane has been sug- gested to be important for the cell functions. In a modeling study of TCNs, it was concluded that specific IT -channel distributions were optimal for the TCNs ability to evoke bursts. To my knowledge, no corresponding studies of IT -channel distribu- tions in INs have been done. Compared to TCNs, INs have relatively long dendrites, and due to their roles as both sender and receiver of signals, the distribution of IT -channels will likely be important for the INs somatic firing properties, and perhaps more so for the two-way signaling between the soma and the distal dendrites. In this thesis, I explore what role the IT -channel distribution plays on the function of INs, using a multicompartmental model of a IN in LGN