Development of chemosensitivity in neurons from the nucleus tractus solitarii (NTS) of neonatal rats.
We studied the development of chemosensitivity during the neonatal period in rat nucleus tractus solitarii (NTS) neurons. We determined the percentage of neurons activated by hypercapnia (15% CO(2)) and assessed the magnitude of the response by calculating the chemosensitivity index (CI). There were no differences in the percentage of neurons that were inhibited (9%) or activated (44.8%) by hypercapnia or in the magnitude of the activated response (CI 164+/-4.9%) in NTS neurons from neonatal rats of all ages. To assess the degree of intrinsic chemosensitivity in these neurons we used chemical synaptic block medium and the gap junction blocker carbenoxolone. Chemical synaptic block medium slightly decreased basal firing rate but did not affect the percentage of NTS neurons that responded to hypercapnia at any neonatal age. However, in neonates aged <P10, but not in older neonates, chemical synaptic block medium increased CI. Carbenoxolone did not significantly alter the number of NTS neurons activated by hypercapnia in neonatal rats of any age. In summary, the response of NTS neurons from neonatal rats appears to be intrinsic and largely unchanged throughout early development. In young neonates (<P10) chemical synaptic input reduces the magnitude of the firing rate response to hypercapnia, but otherwise neither chemical synaptic input nor gap junctions significantly alter the percentage of NTS neurons that respond to hypercapnia or the magnitude of that response.
Conrad
Susan C
SC
Department of Neuroscience, Cell Biology and Physiology, Wright State University School of Medicine, 3640 Colonel Glenn Highway, Dayton, OH 45435, United States.
Nichols
Nicole L
NL
Ritucci
Nick A
NA
Dean
Jay B
JB
Putnam
Robert W
RW
D000367:Age Factors; D000704:Analysis of Variance; D000818:Animals; D000831:Animals, Newborn; D002229:Carbenoxolone / Q000494:pharmacology; D002245:Carbon Dioxide / Q000494:pharmacology; D002628:Chemoreceptor Cells / Q000502:physiology*; D004347:Drug Interactions; D004558:Electric Stimulation; D006935:Hypercapnia / Q000503:physiopathology; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology*; D018408:Patch-Clamp Techniques / Q000379:methods; D051381:Rats; D017207:Rats, Sprague-Dawley; D017552:Solitary Nucleus / Q000166:cytology* / Q000254:growth & development*
D002245:Carbon Dioxide; D002229:Carbenoxolone