Fig. 3: Chemogenetic modulations of dorsal and median Raphe 5-HT neuron activity differentially affect short and long-term ethanol consumption.
From: Neural serotonergic circuits for controlling long-term voluntary alcohol consumption in mice
A–E mCherry-control, hM3Dq-excitatory and hM4Di-inhibitory DREADDs were injected in pet1-5-HT DRN neurons and their expression in TPH2-immunoreactive neurons was confirmed by immunohistochemistry (A, micrograph field corresponding to the red dashed square in the diagram above, scale bar: 150 µm). Manipulation of DREADD-expressing neurons in the DRN by systemic CNO (1 mg/kg) bidirectionally modulated short-term (6 weeks) ethanol intake, with their stimulation increasing ethanol intake, and their inhibition reducing ethanol intake (B–C, repeated measure two-way ANOVA, n = 8, treatment x construct: F (2, 21) = 11.34; p = 0.0005; with Bonferroni multiple comparison: *p = 0.0113, **p = 0.0072). However, this modulation of ethanol intake by DRN 5-HT neurons was lost long-term exposure to ethanol (D–E, repeated measure two-way ANOVA, n = 8, treatment x construct: F (2, 21) = 0.1371; p = 0.8727). mCherry-control, hM3Dq-excitatory and hM4Di-inhibitory DREADDs were then injected in pet1-5-HT MRN neurons and their expression in TPH2-immunoreactive neurons was confirmed by immunohistochemistry (F, micrograph field corresponding to the blue dashed square in the diagram above, scale bar: 100 µm). Manipulation of DREADD-expressing neurons in the MR by intraperitoneal CNO (1 mg/kg) had no effect on short-term (6 weeks) ethanol intake (G–H, repeated measure two-way ANOVA, n = 6, treatment x construct: F (2, 15) = 0.5862, p = 0.5687). However, inhibition of MRN 5-HT neurons by systemic CNO (1 mg/kg) reduced long-term ethanol intake (I–J, repeated measure two-way ANOVA, n = 6, treatment x construct: F (2, 15) = 9.318, p = 0.0023, with Bonferroni multiple comparison: **p = 0.0031), while their activation had no effect (I-J, p = 0.1836).
