| First Author | Barrett KT | Year | 2016 |
| Journal | J Neurosci | Volume | 36 |
| Issue | 14 | Pages | 3943-53 |
| PubMed ID | 27053202 | Mgi Jnum | J:231745 |
| Mgi Id | MGI:5774883 | Doi | 10.1523/JNEUROSCI.1796-15.2016 |
| Citation | Barrett KT, et al. (2016) Partial Raphe Dysfunction in Neurotransmission Is Sufficient to Increase Mortality after Anoxic Exposures in Mice at a Critical Period in Postnatal Development. J Neurosci 36(14):3943-53 |
| abstractText | Sudden infant death syndrome (SIDS) cases often have abnormalities of the brainstem raphe serotonergic (5-HT) system. We hypothesize that raphe dysfunction contributes to a failure to autoresuscitate from multiple hypoxic events, leading to SIDS. We studied autoresuscitation in two transgenic mouse models in which exocytic neurotransmitter release was impaired via conditional expression of the light chain from tetanus toxin (tox) in raphe neurons expressing serotonergic bacterial artificial chromosome driversPet1orSlc6a4 These used recombinase drivers targeted different portions of medullary raphe serotonergic, tryptophan hydroxylase 2 (Tph2)(+)neurons by postnatal day (P) 5 through P12: approximately one-third in triple transgenicPet1::Flpe, hbetaactin::cre, RC::PFtoxmice; approximately three-fourths inSlc6a4::cre, RC::Ptoxmice; with the first model capturing a near equal number ofPet1(+),Tph2(+)versusPet1(+),Tph2(low or negative)raphe cells. At P5, P8, and P12, "silenced" mice and controls were exposed to five, approximately 37 s bouts of anoxia. Mortality was 5-10 times greater in "silenced" pups compared with controls at P5 and P8 (p= 0.001) but not P12, with cumulative survival not differing between experimental transgenic models. "Silenced" pups that eventually died took longer to initiate gasping (p= 0.0001), recover heart rate (p= 0.0001), and recover eupneic breathing (p= 0.011) during the initial anoxic challenges. Variability indices for baseline breathing distinguished "silenced" from controls but did not predict mortality. We conclude that dysfunction of even a portion of the raphe, as observed in many SIDS cases, can impair ability to autoresuscitate at critical periods in postnatal development and that baseline indices of breathing variability can identify mice at risk. SIGNIFICANCE STATEMENT: Many sudden infant death syndrome (SIDS) cases exhibit a partial ( approximately 26%) brainstem serotonin deficiency. Using recombinase drivers, we targeted different fractions of serotonergic and raphe neurons in mice for tetanus toxin light chain expression, which prevented vesicular neurotransmitter release. In one model, approximately one-third of medullary Tph2(+)neurons are silenced by postnatal (P) days 5 and 12, along with some Pet1(+),Tph2(low or negative)raphe cells; in the other, approximately three-fourths of medullary Tph2(+)neurons, also with some Tph2(low or negative)cells. Both models demonstrated excessive mortality to anoxia (a postulated SIDS stressor) at P5 and P8. We demonstrated fatal vulnerability to anoxic stress at a specific time in postnatal life induced by a partial defect in raphe function. This models features of SIDS. |
