ANATOMICAL INVESTIGATIONS OF THE SOURCE OF PERISOMATIC EXCITATORY INPUTS ON PARVALBUMIN-EXPRESSING INTERNEURONS IN THE DENTATE GYRUS AND THE DISTRIBUTION OF TRPC6 CHANNELS IN THE HIPPOCAMPUS
Nagy Attila Gergő
János Szentágothai Neurosciences Division
Dr. Bereczki Dániel
SE Belgyógyászati és Onkológiai Klinika, Simonyi Terem
2026-05-13 09:30:00
Functional neurosciences
Dr. Sperlágh Beáta
Dr. Hájos Norbert
Dr. Zachar Gergely
Dr. Rimayné Dr. Ábrahám Hajnalka
Dr. Alpár Alán
Dr. Adorján István
Dr. Rácz Bence
The hippocampus plays a fundamental role in several physiological functions such as memory and spatial navigation and pathological conditions such as depression or epilepsy. Despite decades of intensive research, several details of the hippocampal operation are still not known. The DG, a part of the hippocampus, is a brain region known to be critical in processing the multimodal information transmitted from cortical regions to the hippocampus. One type of inhibitory cells, PV-IRs, play a key role in DG functions. These INs receive excitatory inputs on their perisomatic region; however, the source of these synapses has been unknown. In the work presented in the first part of my thesis we used a combination of immunohistochemistry, light and electron microscopy, and in vitro patch clamp electrophysiology to address this question. Our results indicate that in the DG, SGCs are the primary source of perisomatic excitatory synapses on PV-IRs.
TRPC6 channels are DAG-sensitive, Ca2+-permeable, non-selective cation channels. These channels are selectively activated by hyperforin, the active constituent of Hypericum perforatum (St John’s wort). Hyperforin has mild antidepressant effects and has a neuroprotective effect during seizures. TRPC6 channels have also been proposed to be involved in the formation and maintenance of excitatory synapses and dendritic spines. To understand how TRPC6 channels are involved in hippocampal functions, in our work presented in the second part of my thesis, we aimed to determine its cellular and subcellular distribution in the hippocampus using immunohistochemistry and light and electron microscopy. Our results show that TRPC6 channels are expressed in the dendrites, spines, somata, axons and axon terminals of the GCs. In the dendrites, spines and cell bodies of the GCs, the TRPC6 channels are expressed in the plasma membranes. In the spines, the TRPC6 channels are evenly distributed showing an enrichment at the edge of the synapses. In the axons and terminals TRPC6 channels are frequently localized intracellularly, in the terminals often associated to membrane cisternae. We also show that in the hippocampus, TRPC6 channels are expressed in the dendrites of two interneuron populations expressing mGluR1a or parvalbumin.
Taken together, these results lead to a better understanding of the possible roles of SGCs and TRPC6 channels in the hippocampus and open the way for further, functional investigations.
