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Post‐natal age enhances somal calcium responses of peripheral chemoreceptor neurons in response to extracellular ATP
Author(s) -
Nunes Ana Rita,
Gauda Estelle B.,
Donnelly David F
Publication year - 2009
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.23.1_supplement.1002.5
Subject(s) - chemoreceptor , extracellular , medicine , endocrinology , receptor , purinergic receptor , suramin , carotid body , hypoxia (environmental) , adenosine triphosphate , biology , calcium , electrophysiology , chemistry , biochemistry , organic chemistry , oxygen
ATP, acting through P2X receptors, mediates hypoxia‐induced excitation in the carotid body (CB). The magnitude of excitation increases over the first 3 weeks after birth. We hypothesized that this increase is due, in part, to enhanced responses of P2X receptors. The CB was harvested, intact, with the petrosal ganglion and chemoreceptor neurons of SD rats aged P12‐P17 (n=5, younger) and P20‐24 (n=2, older). Chemoreceptor neurons were labelled by applying calcium green dextran crystals (3 Kd, Molecular Probes) to the CB. The change in fluorescent (°F) from baseline in response to increasing concentrations of ATP was obtained for 57 and 36 neurons in the younger and older animals, respectively. At each concentration of ATP, the percent of positively responding cells was greater for the older than the younger animals: 45% vs 30% at 250 μM; 67% vs 21% at 500 μM; and 34% vs 6% at 1000 μM of ATP. Furthermore, the magnitude °F was greater in the older vs the younger animals with 11 vs 5% of the cells, having > 20% °F in response to 500 μM of ATP and 11 vs 3% in response to 1000 μM of ATP in the older vs younger age group, respectively. The °F in response to ATP was blocked by pre‐incubation with suramin (0.1 μM) nonspecific blocker, or TNP‐ATP (0.5 μM ) PX3 receptor blocker. Thus, a greater sensitivity of the P2X receptors on chemoafferents to ATP may in part account for maturation of hypoxic chemosensitivty. NIH HL072748 ; SFRH / BD / 39473 / 2007