Group I metabotropic glutamate receptors activate a calcium-sensitive transient receptor potential-like conductance in rat hippocampus - PubMed (original) (raw)

A, sample traces from one cell recorded with intracellular K+ and 1 m

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GDPβS are shown in chronological order. _A_1, 2, the loss of response to baclofen indicates G protein blockade. _A_3, following G protein blockade, responses to DHPG were blocked. _A_4, raising intracellular Ca2+ by increasing extracellular K+ rescued the response to selective activation of mGluR5 (DHPG + LY367385). _A_5, rescue is also observed by activation of both group I mGluRs after washing LY367385 from the slice. _A_6, response in 8 m

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K+ to selective activation of mGluR1 (DHPG + MPEP). _B_1, pooled data with GTP, GDPβS or GDPβS plus _N_-(2,6-dimethylphenylcarbamoylmethyl) triethylammonium chloride (QX-314; 5 m

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) showing the block of responses to DHPG in 2.7 m

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K+, potentiation of the response in GTP cells with 8 m

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K+ and rescue of the response after G protein blockade. _B_2, with intracellular Cs+, GDPβS still blocked the response to DHPG in 2.7 m

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K+ and responses were rescued with 8 m

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K+. C, with intracellular GDPβS, responses to baclofen recorded within 3 min of gaining whole-cell access were abolished within 12–60 min. Raising extracellular K+ to 8 m

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did not affect G protein blockade by GDPβS. With QX-314 added to the GDPβS-containing solution, baclofen responses were blocked within 10–36 min, and again were not affected by the rise in intracellular Ca2+ induced by 8 m

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K+. D, pooled data from five cells in which responses to DHPG with the mGluR1- and mGluR5-selective antagonists were obtained in 8 m

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K+ following G protein blockade. E, rescue of responses to DHPG by 8 m

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K+ was not affected by the phospholipase C antagonist U73122 (10 µ

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). In two cells, G proteins were blocked by GDPβS, and in five cells they were blocked by GDPβS plus QX-314. F, following G protein blockade, the L-type Ca2+ channel agonist BAY K8644 also rescued the response to DHPG. Traces are from one cell, with baclofen responses abolished by GDPβS. G, BAY K8644 increased intracellular Ca2+ levels (holding potential −50 mV). A typical CA3 pyramidal cell showing the region of interest along with the simultaneous Ca2+ and electrophysiological recordings.