| Project/Area Number |
05680707
|
|---|
| Research Category |
Grant-in-Aid for General Scientific Research (C)
|
| Allocation Type | Single-year Grants |
|---|
| Research Field |
Neuroscience in general
|
|---|
| Research Institution | Showa University |
|---|
Principal Investigator |
ONIMARU Hiroshi Showa Univ.School of Med.Dept.of Physiol. ; Assistant Prof., 医学部, 講師 (30177258)
|
|---|
| Project Period (FY) |
1993 – 1994
|
| Project Status |
Completed (Fiscal Year 1994)
|
| Budget Amount *help |
¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 1994: ¥300,000 (Direct Cost: ¥300,000)
Fiscal Year 1993: ¥1,700,000 (Direct Cost: ¥1,700,000)
|
|---|
| Keywords | respiratory center / rhythm generation / brain-stem spinal cord / Ca channels / respiratory neurons / newbron rat / medulla / Ca チャネル / Kチャネル |
|---|
| Research Abstract |
The purpose of the present study was to analyze properties of membrane ionic channels of mammalian medullary respiratory neurons by whole-cell patch-clamp recordings. I focused on analysis of mainly Ca channels of pre-inspiratory (Pre-I), inspiratory (Insp) and tonic-expiratory (Exp) neurons in brainstem-spinal cord preparations isolated from newborn rats. These respiratory neurons were recorded in the rostral ventrolateral medulla. After Na-channel blockade by TTX and K-channel blockade by Cs^+ and TEA^+, at least 4types of Ca-dependent membrane potential responses were revealed : 1) High-threshold Ca^<2+> spike (HTS) which has the threshold of -40 to -20mV.The HTS was observed in all types of respiratory neurons analyzed. 2) Rebound responses including low-threshold Ca^<2+> spike (LTS) ; depolarizing responses to termination of hyperpolarizing current pulses. The LTS that was induced at holding potential below -50mV,was observed frequently in Pre-I,Insp or Exp neurons that tended to
… More
show continuous firings (i.e.tonic pacemaker activity) in the perfusate with or without TTX.3) Low-threshold Ca^<2+> after-depolarization (L-ADP). This was observed at holding potential more negative than -45 to -50 mV and the amplitude increased with progressive membrane hyperpolarization. The L-ADP was observed in some Insp neurons. 4) Intermediate-threshold Ca^<2+> plateau potential (ITP) of which threshold ranged from -50 to -40mV.This response was characterized with slow regenerative depolarization induced by brief depolarization from resting potential level (about -50mV) and with afterdepolarization at termination of depolarizing current pulse injection. The amplitude decreased with membrane hyperpolarization. The ITP was detected in about half of Pre-I neurons and type III (receiving inhibitory synaptic input from Pre-I) Insp neurons. Pharmacological study suggested that P-and also N-type Ca channels are involved in ITP responses. The present study shows that medullary respiratory neurons in newborn rat preparations have a complex set of Ca-dependent membrane conductances, which may be relevant for the respiratory burst generation and maintenance. Less
|
