Chemogenetic inhibition of the lateral hypothalamic area to decrease food intake in rats: A proof-of-concept study and the optimization of technical parameters

Designer receptors exclusively activated by designer drugs (DREADD) are chemogenetic tools that enable the selective activation or silencing of neurons in a given brain area. According to classical findings on the role of the lateral hypothalamic area (LHA) in hunger, we hypothesized that selective silencing of the LHA may decrease food intake.We bilaterally injected adeno-associated viral (AAV) vectors carrying the gene of a modified M4 muscarinic acetylcholine receptor into the LHA of rats. Later, rats were treated with DREADD actuator agents and food intake was measured in a 30 min time-window after refeeding subsequently to 16 h food restriction. To optimize the technical parameters, we tested different AAV serotypes, injection volumes, and actuators with various modes of administration.Deschloroclozapine decreased the food intake of rats that were transfected with AAV5 or AAV9 vectors both after subcutaneous and oral administrations. However, clozapine-N-oxid was not effective in rats that were transfected with AAV9 vectors. In further experiments, AAV2 and AAV5 were compared, and we found that substantially higher injection volume has to be used in the case of AAV2 (min. 1000 nl) compared to AAV5 (500 nl). Visualisation of mCherry reporter protein showed that transfection using AAV5 resulted in the expression of the transgene in a substantially larger area compared to AAV2.In conclusion, we demonstrated the proof-of-concept that chemogenetic silencing of the LHA is an effective way to decrease food intake. Our results suggest that AAV5 serotype is more appropriate to achieve stable expression of DREADD and effective pharmacological modulation.