Genetically Targeted Connectivity Tracing Excludes Dopaminergic Inputs to the Interpeduncular Nucleus from the Ventral Tegmentum and Substantia Nigra.

The "habenulopeduncular system" consists of the medial habenula (MHb) and its principal target of innervation, the interpeduncular nucleus (IP). Neurons in the ventral MHb (MHbV) express acetylcholine along with glutamate, and both the MHb and IP are rich in nicotinic acetylcholine receptors. Much of the work on this system has focused on nicotinic mechanisms and their clinical implications for nicotine use, particularly because the IP expresses the α5 nicotinic receptor subunit, encoded by the CHRNA5 gene, which is genetically linked to smoking risk.

Mapping Cell Types and Efferent Pathways in the Ascending Relaxin-3 System of the Nucleus Incertus.

Relaxin-3 (Rln3) is an insulin-family peptide neurotransmitter expressed primarily in neurons of the nucleus incertus (NI) of the pontine tegmentum, with smaller populations located in the deep mesencephalon (DpMe) and periaqueductal gray (PAG). Here, we have used targeted recombination at the gene locus to generate an transgenic mouse line, and characterize the molecular identity and axonal projections of Rln3-expressing neurons. Expression of Cre recombinase in mice, and the expression of Cre-mediated reporters, accurately reflect the expression of Rln3 mRNA in all brain regions.

Dual recombinase fate mapping reveals a transient cholinergic phenotype in multiple populations of developing glutamatergic neurons.

Cholinergic transmission shapes the maturation of glutamatergic circuits, yet the developmental sources of acetylcholine have not been systematically explored. Here, we have used Cre-recombinase-mediated genetic labeling to identify and map both mature and developing CNS neurons that express choline acetyltransferase (ChAT). Correction of a significant problem with a widely used Chat transgenic line ensures that this map does not contain expression artifacts.

Chrna5-Expressing Neurons in the Interpeduncular Nucleus Mediate Aversion Primed by Prior Stimulation or Nicotine Exposure.

Genetic studies have shown an association between smoking and variation at the gene locus encoding the α5, α3, and β4 nicotinic receptor subunits. The α5 receptor has been specifically implicated because smoking-associated haplotypes contain a coding variant in the gene. The locus is conserved in rodents and the restricted expression of these subunits suggests neural pathways through which the reinforcing and aversive properties of nicotine may be mediated.