GH1 and nicotine dependence: Moreover, down-regulated GO terms mainly included chemical synaptic transmission and synapse function (Fig. 2d), and the related down-regulated KEGG pathways were neuroactive ligand-receptor interaction, Rap1 signaling pathway, growth hormone synthesis, secretion and action, glutamatergic synapse, GABAergic synapse, and nicotine addiction (Fig. 2e).