Neurokinin-1 receptor (NK1R) and mu-opioid receptor (muOR) agonists affected respiratory rhythm when injected directly into the preBötzinger Complex (preBötC), the hypothesized site for respiratory rhythmogenesis in mammals. These effects were mediated by actions on preBötC rhythmogenic neurons. The distribution of NK1R+ neurons anatomically defined the preBötC. Type 1 neurons in the preBötC, which have rhythmogenic properties, expressed both NK1Rs and muORs, whereas type 2 neurons expressed only NK1Rs. These findings suggest that the preBötC is a definable anatomic structure with unique physiological function and that a subpopulation of neurons expressing both NK1Rs and muORs generate respiratory rhythm and modulate respiratory frequency.

The mammalian pancreas is constructed during embryogenesis by multipotent progenitors, the identity and function of which remain poorly understood. We performed genome-wide transcription factor expression analysis of the developing pancreas to identify gene expression domains that may represent distinct progenitor cell populations. Five discrete domains were discovered. Genetic lineage-tracing experiments demonstrate that one specific domain, located at the tip of the branching pancreatic tree, contains multipotent progenitors that produce exocrine, endocrine, and duct cells in vivo. These multipotent progenitors are Pdx1(+)Ptf1a(+)cMyc(High)Cpa1(+) and negative for differentiated lineage markers. The outgrowth of multipotent tip cells leaves behind differentiated progeny that form the trunk of the branches. These findings define a multipotent compartment within the developing pancreas and suggest a model of how branching is coordinated with cell type specification. In addition, this comprehensive analysis of >1,100 transcription factors identified genes that are likely to control critical decisions in pancreas development and disease.

The normal breathing rhythm in mammals is hypothesized to be generated by neurokinin-1 receptor (NK1R)-expressing neurons in the preBötzinger complex (preBötC), a medullary region proposed to contain the kernel of the circuits generating respiration. If this hypothesis is correct, then complete destruction of preBötC NK1R neurons should severely perturb and perhaps even fatally arrest breathing. Here we show that specific and near complete bilateral (but not unilateral) destruction of preBötC NK1R neurons results in both an ataxic breathing pattern with markedly altered blood gases and pH, and pathological responses to challenges such as hyperoxia, hypoxia and anesthesia. Thus, these ~600 neurons seem necessary for the generation of normal breathing in rats.Breathing is an exceptionally reliable and continuous mammalian behavior that regulates blood gases and pH at rest and in response to diverse challenges such as exercise, sleep or altitude. The rhythm underlying breathing is postulated to depend critically on neurons in the preBötC1 , 2. Two recent developments allowed us to determine in awake adult rats whether this critical regulatory behavior would be affected by lesions in the preBötC. First, the extent of the preBötC can be anatomically defined by the sub-population of propriobulbar respiratory neurons within the ventrolateral respiratory column expressing NK1R3 -5 . Second, NK1R neurons can be specifically lesioned by substance P conjugated to saporin (SP-SAP) 6 , an effect that takes several days, allowing for complete recovery from surgery6. ResultsSP-SAP was effective in eliminating preBötC NK1R neurons in adult rats. Injections of 0.1-0.2 pmol of SP-SAP or 0.3 pmol each of unconjugated saporin and SP were made in the preBötC. Unilateral SP-SAP injection transiently produced sighs (large inspiratory efforts followed by prolonged expiration), consistent with the effects of injection of SP alone into the pre-BötC in vitro 7 and in vivo (P.A.G., D.R.M. and J.L.F., unpublished observations). All rats returned to normal behavior upon recovery from surgery. Two to eighteen days after injection, rats were perfused and their medullas were stained for NK1R immunoreactivity (n = 20 NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript lesion extent was estimated by counting NK1R immunopositive neuronal soma in the rostral medulla inside a circle of 600-μm diameter approximating the preBötC (ventrolateral to the nucleus ambiguus) and in a rectangle (1600 × 1070 μm) outside this circle (Fig. 1, inset). Counts were estimated from four transverse sections beginning within 100 μm of the rostral border of the lateral reticular nucleus and spanning the preBötC 3,4 containing approximately 12-15% of the total preBötC volume. Uninjected controls (n = 4) had 35 ± 5.1 (mean ± s.e.m., per side) NK1R neurons within the preBötC (~600 preBötC NK1R neurons total, which we estimate represent less than 10% of all preBötC neurons) and 82 ± 9 NK1R neurons outside the preBötC. Most of the latter were i...

Mechanical deflection of the sensory hair bundles of receptor cells in the inner ear causes ion channels located at the tips of the bundle to open, thereby initiating the perception of sound. Although some protein constituents of the transduction apparatus are known, the mechanically gated transduction channels have not been identified in higher vertebrates. Here, we investigate TRP (transient receptor potential) ion channels as candidates and find one, TRPA1 (also known as ANKTM1), that meets criteria for the transduction channel. The appearance of TRPA1 messenger RNA expression in hair cell epithelia coincides developmentally with the onset of mechanosensitivity. Antibodies to TRPA1 label hair bundles, especially at their tips, and tip labelling disappears when the transduction apparatus is chemically disrupted. Inhibition of TRPA1 protein expression in zebrafish and mouse inner ears inhibits receptor cell function, as assessed with electrical recording and with accumulation of a channel-permeant fluorescent dye. TRPA1 is probably a component of the transduction channel itself.