AAV5-hSyn-mCherry

Central cholinergic circuits play a role in regulating feeding behavior. The dorsomedial hypothalamus (DMH) is considered an appetite-stimulating center and contains cholinergic neurons. Here, researchers investigated the role of DMH cholinergic neurons in controlling food intake. Mice lacking the Chat gene in the DMH lost weight compared to controls. Chemogenetic activation of DMH cholinergic neurons promoted food intake. This orexigenic effect was further supported by experiments using optogenetic stimulation of DMH cholinergic neurons. DMH cholinergic neurons innervate proopiomelanocortin neurons in the arcuate nucleus (ARC) of the hypothalamus. Treatment with acetylcholine (ACh) enhanced GABAergic inhibitory transmission to ARC POMC neurons, which was blocked by muscarinic receptor antagonists. Direct activation of cholinergic fibers in the ARC readily stimulates food intake that is also abolished by the muscarinic receptor antagonist.

Here, the researchers first examined whether ACh in the DMH regulates body weight. To delete the Chat gene in DMH cholinergic neurons, they bilaterally injected AAV5-hSyn-mCherry (control) or AAV5-hSyn-mCherry-Cre viruses into the DMH of a floxed mutant that possesses loxP sites flanking exons 3 and 4 of the Chat gene (ChAT^flox/flox) (Figure 1A). The study found that male mice lacking the Chat gene in the DMH gained significantly less weight than control mice fed a normal diet (Figure 1B, AAV5-con, n = 12 mice; AAV5-Cre, n = 12 mice). Although female mice also showed a trend of decreased body weight, there was no significant difference between mice infected with AAV5-control or AAV5-Cre (Figure 1B, AAV5-con, n = 11 mice; AAV5-Cre, n = 11 mice). These findings suggest that ACh in DMH cholinergic neurons is required for body weight maintenance.

Figure 1. A. Schematic diagram showing the injection of AAV vectors into the DMH of ChAT^flox/flox mice. B. Effects of loss of DMH cholinergic function on mouse body weight. (Jeong J H, et al., 2017)