title: G-protein-coupled inward rectifier potassium channels involved in corticostriatal presynaptic modulation.
abstract: Presynaptic modulation has been associated mainly with calcium channels but recent data suggests that inward rectifier potassium channels (K(IR)) also play a role. In this work we set to characterize the role of presynaptic K(IR) channels in corticostriatal synaptic transmission. We elicited synaptic potentials in striatum by stimulating cortical areas and then determined the synaptic responses of corticostriatal synapsis by using paired pulse ratio (PPR) in the presence and absence of several potassium channel blockers. Unspecific potassium channels blockers Ba(2+) and Cs(+) reduced the PPR, suggesting that these channels are presynaptically located. Further pharmacological characterization showed that application of tertiapin-Q, a specific K(IR)3 channel family blocker, also induced a reduction of PPR, suggesting that K(IR)3 channels are present at corticostriatal terminals. In contrast, exposure to Lq2, a specific K(IR)1.1 inward rectifier potassium channel, did not induce any change in PPR suggesting the absence of these channels in the presynaptic corticostriatal terminals. Our results indicate that K(IR)3 channels are functionally expressed at the corticostriatal synapses, since blockage of these channels result in PPR decrease. Our results also help to explain how synaptic activity may become sensitive to extracellular signals mediated by G-protein coupled receptors. A vast repertoire of receptors may influence neurotransmitter release in an indirect manner through regulation of K(IR)3 channels.
authors.affiliation: Neurociencias, FES Iztacala, UNAM, México.
authors.forename: David
authors.initials: D
authors.lastname: Meneses
authors.affiliation: Neurociencias, FES Iztacala, UNAM, México.
authors.forename: Verónica
authors.initials: V
authors.lastname: Mateos
authors.affiliation: Neurociencias, FES Iztacala, UNAM, México.
authors.forename: Gustavo
authors.initials: G
authors.lastname: Islas
authors.affiliation: Neurociencias, FES Iztacala, UNAM, México.
authors.forename: Jaime
authors.initials: J
authors.lastname: Barral
mesh_terms: D000818:Animals; D002540:Cerebral Cortex / Q000187:drug effects / Q000502:physiology*; D003342:Corpus Striatum / Q000187:drug effects / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D051676:G Protein-Coupled Inwardly-Rectifying Potassium Channels / Q000378:metabolism*; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D026902:Potassium Channel Blockers / Q000494:pharmacology; D017729:Presynaptic Terminals / Q000187:drug effects / Q000502:physiology*; D017208:Rats, Wistar; D046509:Tissue Culture Techniques
chemical_list: D051676:G Protein-Coupled Inwardly-Rectifying Potassium Channels; D026902:Potassium Channel Blockers
keywords: corticostriatal presynaptic channels; inward rectifier potassium channels; paired pulse facilitation