The Edinger-Westphal nucleus of the juvenile rat contains transient- and repetitive-firing neurons

TY - JOUR

T1 - The Edinger-Westphal nucleus of the juvenile rat contains transient- and repetitive-firing neurons

AU - Laursen, M

AU - Rekling, J C

PY - 2006/8/11

Y1 - 2006/8/11

N2 - Classically, the Edinger-Westphal nucleus is described as containing neurons controlling accommodation and pupillary constriction via projections to the ciliary ganglion. However, in several species including rat, some Edinger-Westphal neurons have ascending or descending CNS projections suggesting that the Edinger-Westphal nucleus might also have non-ocular functions. To further characterize the function of this nucleus we studied the electrophysiological properties of Edinger-Westphal neurons in a slice preparation from juvenile rats. The position of the Edinger-Westphal nucleus was determined using an immunohistochemical procedure directed at the peptide Urocortin, which is expressed in Edinger-Westphal neurons. Passive and active membrane responses were investigated and two different neuron types were identified. One type had a transient firing response to 400 ms depolarizing current pulses and one type had a repetitive firing response. Transient-firing neurons had an outward rectifying response inhibiting firing, possibly due to slowly inactivating I(D)-like potassium channels since low concentrations (200 microM) of the potassium channel blocker 4-aminopyridine elicited repetitive firing. In all neurons, low threshold Ca(2+) spikes were seen and these were blocked by nickel(II) chloride hexahydrate, suggesting that they are mediated via low voltage-activated Ca(2+) channels. Some biocytin-labeled neurons had axons or axonal collaterals projecting laterally or dorsally, suggesting possible non-ocular targets. In conclusion, the rat Edinger-Westphal nucleus contains two separate types of neurons with distinct electrophysiological properties.

AB - Classically, the Edinger-Westphal nucleus is described as containing neurons controlling accommodation and pupillary constriction via projections to the ciliary ganglion. However, in several species including rat, some Edinger-Westphal neurons have ascending or descending CNS projections suggesting that the Edinger-Westphal nucleus might also have non-ocular functions. To further characterize the function of this nucleus we studied the electrophysiological properties of Edinger-Westphal neurons in a slice preparation from juvenile rats. The position of the Edinger-Westphal nucleus was determined using an immunohistochemical procedure directed at the peptide Urocortin, which is expressed in Edinger-Westphal neurons. Passive and active membrane responses were investigated and two different neuron types were identified. One type had a transient firing response to 400 ms depolarizing current pulses and one type had a repetitive firing response. Transient-firing neurons had an outward rectifying response inhibiting firing, possibly due to slowly inactivating I(D)-like potassium channels since low concentrations (200 microM) of the potassium channel blocker 4-aminopyridine elicited repetitive firing. In all neurons, low threshold Ca(2+) spikes were seen and these were blocked by nickel(II) chloride hexahydrate, suggesting that they are mediated via low voltage-activated Ca(2+) channels. Some biocytin-labeled neurons had axons or axonal collaterals projecting laterally or dorsally, suggesting possible non-ocular targets. In conclusion, the rat Edinger-Westphal nucleus contains two separate types of neurons with distinct electrophysiological properties.

KW - 4-Aminopyridine

KW - Action Potentials

KW - Animals

KW - Animals, Newborn

KW - Brain Stem

KW - Corticotropin-Releasing Hormone

KW - Dose-Response Relationship, Radiation

KW - Electric Stimulation

KW - Female

KW - Ganglia, Parasympathetic

KW - Immunohistochemistry

KW - Lysine

KW - Male

KW - Neurons

KW - Nickel

KW - Patch-Clamp Techniques

KW - Potassium Channel Blockers

KW - Rats

KW - Rats, Wistar

KW - Sodium Channel Blockers

KW - Tetrodotoxin

KW - Urocortins

U2 - 10.1016/j.neuroscience.2006.03.062

DO - 10.1016/j.neuroscience.2006.03.062

M3 - Journal article

C2 - 16677766

SN - 0306-4522

VL - 141

SP - 191

EP - 200

JO - Neuroscience

JF - Neuroscience

IS - 1

ER -