P- and R-type Ca2+ channels regulating spinal glycinergic nerve terminals
Kiku Nonaka1, Nobuki Murayama, Megumi Maeda
1Graduate School of Science and Technology, Kumamoto University, Kurokami 2-39-1, Kumamoto, Japan 860-8555.
Toxicon : Official Journal of the International Society on Toxinology
|February 11, 2010
Summary
Calcium (Ca2+) entry via P- and R-type channels predominantly controls glycine release at rat spinal nerve endings. This study clarifies the specific roles of these calcium channels in glycinergic neurotransmission.
Area of Science:
- Neuroscience
- Cellular Biology
- Neurophysiology
Background:
- Glycinergic nerve endings (boutons) in the rat spinal sacral commissural nucleus (SDCN) play a crucial role in inhibitory neurotransmission.
- The specific types of calcium channels mediating glycine release from these boutons remain largely uncharacterized.
Purpose of the Study:
- To investigate the functional contribution of P- and R-type calcium channels to glycinergic neurotransmission in the rat SDCN.
- To elucidate the mechanisms controlling glycine release at spinal nerve terminals.
Main Methods:
- Measurement of inhibitory postsynaptic currents (eIPSCs) from individual glycinergic nerve endings.
- Focal electrical stimulation of nerve endings.
- Application of selective calcium channel antagonists (omega-Aga IVA, SNX-482, Ni2+) and varying extracellular calcium concentrations ([Ca2+](o)).
Main Results:
- Glycinergic eIPSC amplitude and failure rate were directly influenced by extracellular calcium concentrations.
- P-type calcium channel blockade significantly suppressed eIPSCs, with little contribution from Q-type channels.
- R-type calcium channel antagonism markedly reduced eIPSC amplitude and increased failure rates.
Conclusions:
- Glycine release from spinal nerve endings is primarily regulated by calcium influx through P- and R-type calcium channels.
- These calcium channels are ubiquitously present at spinal glycine release sites, highlighting their critical role in glycinergic neurotransmission.
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