Mechanisms and functional impact of Group I metabotropic glutamate receptor modulation of excitability in mouse MNTB neurons.
Synapse
; 74(3): e22137, 2020 03.
Article
in En
| MEDLINE
| ID: mdl-31584700
ABSTRACT
We examined effects of Group I metabotropic glutamate receptors on the excitability of mouse medial nucleus of the trapezoid body (MNTB) neurons. The selective agonist, S-3,5-dihydroxyphenylglycine (DHPG), evoked a dose-dependent depolarization of the resting potential, increased membrane resistance, increased sag depolarization, and promoted rebound action potential firing. Under voltage-clamp, DHPG evoked an inward current, referred to as IDHPG , which was developmentally stable through postnatal day P56. IDHPG had low temperature dependence in the range 25-34°C, consistent with a channel mechanism. However, the I-V relationship took the form of an inverted U that did not reverse at the calculated Nernst potential for K+ or Cl- . Thus, it is likely that more than one ion type contributes to IDHPG and the mix may be voltage dependent. IDHPG was resistant to the Na+ channel blockers tetrodotoxin and amiloride, and to inhibitors of iGluR (CNQX and MK801). IDHPG was inhibited 21% by Ba2+ (500 µM), 60% by ZD7288 (100 µM) and 73% when the two antagonists were applied together, suggesting that KIR channels and HCN channels contribute to the current. Voltage clamp measurements of IH indicated a small (6%) increase in Gmax by DHPG with no change in the voltage dependence. DHPG reduced action potential rheobase and reduced the number of post-synaptic AP failures during high frequency stimulation of the calyx of Held. Thus, activation of post-synaptic Group I mGlu receptors modifies the excitability of MNTB neurons and contributes to the reliability of high frequency firing in this auditory relay nucleus.
Key words
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Action Potentials
/
Receptors, Metabotropic Glutamate
/
Excitatory Amino Acid Agents
/
Synaptic Potentials
/
Trapezoid Body
Limits:
Animals
Language:
En
Journal:
Synapse
Journal subject:
NEUROLOGIA
Year:
2020
Document type:
Article
Affiliation country:
Brasil