A single taxon collected nearly all cholinergic, monoaminergic neurons (which we identified based on expression of the necessary biosynthesis enzymes and vesicular and reuptake transporters; Figure S6C and STAR Methods) from the whole brain, as well as peptidergic neurons mainly of the hypothalamus. These included the cholinergic afferent nuclei of cranial nerves III-V (HBCHO4) and VI-XII (HBCHO3), the adrenergic nucleus of the solitary tract (HBADR), the noradrenergic cell groups of the medulla (HBNOR), five serotonergic hindbrain types, two dopaminergic neuron types of the ventral midbrain, and 15 types of peptidergic neurons, including those secreting neurotensin (Nts), vasopressin (Avp), oxytocin (Oxt), gonadotropin-releasing hormone (Gnrh), galanin (Gal), enkephalin (Penk), orexin (Hcrt), CART peptides (Cartpt), thyrotropin (Trh), pro-opiomelanocortin (Pomc), agouti-related peptide (Agrp), and neuromedin (Nmu) (Lam et al., 2017, Romanov et al., 2017). Most of these peptidergic cell types were located in hypothalamus, but some were from telencephalon (bed nuclei of stria terminalis and septal nucleus), midbrain (Darkschewitz nucleus), and spinal cord (central canal neurons; see below). The fact that the majority of cholinergic, monoaminergic, and peptidergic neurons clustered together suggests a common
