Abstract
Central chemosensitive neurons increase their firing rate (FR) during hypercapnia acidosis (HA). We measured changes in membrane resistance (R in ), rheobase and action potential (AP) properties of neurons in the locus coeruleus (LC) to determine which ion channels may be contributing to the CO 2 -induced FR response. Whole cell recordings were made from LC neurons (n=6) in brainstem slices sectioned from neonatal rats (P11–P13), superfused with artificial cerebral spinal fluid or chemical synaptic blockade medium (11.4 mM Mg 2+ , 0.2 mM Ca 2+ ) with a gap junction blocker (100µM carbenoxolone). HA caused a non-significant increase in R in (34 ± 9 M); however, blockade of chemical and electrical synapses resulted in a significant increase in R in (87 ± 21 M, P<0.05) and HA caused an additional increase of 27 ± 22 M (P<0.05). HA had no effect on AP properties; however, synaptic blockade increased the depolarization threshold (5 ± 8 mV, P<0.05), decreased the rate of depolarization (41 ± 11 mV ms –1 , P<0.05), decreased the rate of repolarization (29 ± 7 mV ms –1 , P<0.05), decreased AP height (45 ± 16 mV, P<0.05), and decreased the after-hyperpolarization (24 ± 6 mV, P<0.05). The increased R in during HA and synaptic blockade supports a role for K + channels, but the high variability of AP properties supports the multiple factors model for chemosensitivity.
[Supported by NIH grants R01HL56683 & F32 HL80877].
| Original language | American English |
|---|---|
| State | Published - Apr 1 2007 |
Disciplines
- Medical Cell Biology
- Medical Neurobiology
- Medical Physiology
- Medical Sciences
- Medicine and Health Sciences
- Neurosciences
- Physiological Processes