Journal: The Journal of Neuroscience

Article Title: Functional Diversity of P-Type and R-Type Calcium Channels in Rat Cerebellar Neurons

doi: 10.1523/JNEUROSCI.16-20-06353.1996

Figure Lengend Snippet: Pharmacological properties of DHP-insensitive whole-cell Ba2+ current of rat cerebellar granule cells. Whole-cell recordings with 5 mm Ba2+ as charge carrier in the continuous presence of 3–5 μm nimodipine to inhibit L-type channels. a, Plot of peak Ba2+ current versus time for an experiment in which 1 μm GVIA and 3 μm MVIIC were sequentially applied and then washed; examples of traces from the same experiment were taken at times indicated by a, b, c.Inset, Calibration: 50 pA, 20 msec. Depolarizations 56 msec long (Vt = −10 mV) were delivered every 10 sec from Vh = −90 mV. Cell T84D. Shown on the right are representative traces recorded during 720-msec-long depolarizations (from a different experiment: cell U22H; calibration: 50 pA, 80 msec). Trace a, Total DHP-insensitive current, 38% current decay after 720 msec, biexponential best fit with τ1 = 50 msec, τ2 = 1938 msec, and relative amplitudes of 0.5 and 99.5% (average values: τ1 = 46 ± 3 msec, τ2 = 1979 ± 51 msec; relative amplitudes 0.4 and 99.6%;n = 11). Trace c, Resistant current in the presence of MVIIC and GVIA, 57% decay after 720 msec, biexponential best fit with τ1 = 40 msec, τ2 = 1177 msec, and relative amplitudes of 1.3 and 98.7% (average values: τ1 = 66 ± 11 msec, τ2 = 1196 ± 104 msec; relative amplitudes 2 and 98 ± 1%, respectively; n = 4). Traces a–c, Difference current, 31% decay after 720 msec, biexponential best fit with τ1 = 57 msec, τ2 = 2000 msec, and relative amplitudes 0.3 and 99.7%.b, Dose–response curve for Ni2+ inhibition of the resistant current recorded in the presence of (in μm): 5 nimodipine, 1 GVIA, and 5 MVIIC. Data were pooled from five cells. The data points were best fit by the sum of two Langmuir adsorption isotherms with dissociation constantsKd1 = 11.8 μm andKd2 = 286 μm, number of binding sites n1 = 1.9 andn2 = 1.1, and relative amplitudes 52 and 48%, respectively. Representative traces of resistant current during 720-msec-long depolarizations (Vt = −10 mV;Vh = −90 mV) before and after addition of 100 μm Ni2+ are shown on thebottom (calibration: 50 pA, 80 msec). Percentage of decay (67%) and time course of decay (τ1 = 78 msec, τ2 = 1029 msec) of the resistant current inhibited by 100 μm Ni2+ were similar to those of the total resistant current. Cell U13C.

Article Snippet: An additional component of HVA current (R-type) has been identified as the current resistant to DHPs and ω-conotoxin MVIIC (SNX-230, Neurex Corporation, Menlo Park, CA) (MVIIC; Hillyard et al., 1992 ; Zhang et al., 1993 ).

Techniques: Inhibition, Adsorption, Binding Assay

Journal: The Journal of Neuroscience

Article Title: Functional Diversity of P-Type and R-Type Calcium Channels in Rat Cerebellar Neurons

doi: 10.1523/JNEUROSCI.16-20-06353.1996

Figure Lengend Snippet: G2 and G3 Ca2+ channels of rat cerebellar granule cells are not blocked irreversibly by MVIIC. Cell-attached recordings with 90 mm Ba2+ as charge carrier. Shown are representative current traces and normalized current amplitude histograms from all traces with activity of single G2 and G3 channels at −10 mV. Depolarizations were 720 msec long and were delivered every 4 sec from holding potentials of −80 to −100 mV. Records were sampled and filtered at 5 and 1 kHz, respectively.Control: G2, unitary current i = 0.69 pA, average open probability Po = 0.20, cell N03C; G3, i = 1.05 pA,Po = 0.06, cell N56B [in the presence of 1 μm (+)-(S)-202-791 in the incubation bath]. MVIIC: Cell-attached recordings with 3 μm MVIIC in pipette after incubation of neurons with 10 μm MVIIC in the potassium gluconate bath solution [and in the presence of 0.5 μm(+)-(S)-202-791]. G2, i = 0.68 pA,Po = 0.23, one L-type channel was also present in the patch (compare unresolved openings of higher amplitude in second trace), cell U24A; G3, i = 0.95 pA,Po = 0.06, cell U23D. In paired control and MVIIC recordings (i.e., performed alternatively on the same neuronal preparation at each day in culture), G2 channels were observed in 9 of 42 patches in controls and in 4 of 32 patches with MVIIC; G3 channels were observed in 8 of 40 patches in controls and in 4 of 31 patches with MVIIC (excluding all multichannel patches for which identification was uncertain). G2 and G3 channels were identified on the basis of their unitary current and conductance and on the basis of the voltage range for activation (compare Table ​Table11 and Forti et al., 1994).

Article Snippet: An additional component of HVA current (R-type) has been identified as the current resistant to DHPs and ω-conotoxin MVIIC (SNX-230, Neurex Corporation, Menlo Park, CA) (MVIIC; Hillyard et al., 1992 ; Zhang et al., 1993 ).

Techniques: Activity Assay, Control, Incubation, Transferring, Activation Assay

Journal: The Journal of Neuroscience

Article Title: Functional Diversity of P-Type and R-Type Calcium Channels in Rat Cerebellar Neurons

doi: 10.1523/JNEUROSCI.16-20-06353.1996

Figure Lengend Snippet: MVIIC and low doses of ω-AgaIVA inhibit the same type of Ca2+ channels in rat cerebellar granule cells. Whole-cell recordings with 5 mm Ba2+ as charge carrier in the continuous presence of 3–5 μm nimodipine. Depolarizations 56 or 136 msec long were delivered every 10 sec.Vt = −10 mV; Vh = −90 mV. a, Filled bars, Average fractional inhibition of DHP-insensitive current by 1 μmGVIA (reversible + irreversible; 20 ± 2%, n = 25), by 50 nm ω-AgaIVA (47 ± 3%,n = 20), by 3 μm MVIIC added after GVIA (MVIIC*; 43 ± 2%, n = 20), and average fractional current remaining in the presence of nimodipine plus GVIA plus MVIIC (R; 38 ± 2%,n = 21). Empty bars, Sum of pharmacological current components indicated below. The sum of the average fraction of DHP-insensitive current resistant to GVIA and MVIIC and the average fraction of current inhibited by GVIA and that inhibited by low doses of ω-AgaIVA amounted to 104 ± 7%. In agreement with Amico et al. (1995) and in contrast with Pearson et al. (1995), there seems to be no significant overlapping selectivity between GVIA and ω-AgaIVA. b, Plot of peak Ba2+ current versus time for an experiment in which 50 nm ω-AgaIVA plus 2 μm GVIA and 3 μm MVIIC were sequentially applied and then washed.Vh = −90 mV; Vt = −10 mV. Inset, Traces taken at times a, b, c (calibration: 50 pA, 20 msec). Cell T82F. On average, the fraction of non-L current inhibited irreversibly by 3 μmMVIIC added after 50 nm ω-AgaIVA (+GVIA) was 10 ± 1% (n = 5).

Article Snippet: An additional component of HVA current (R-type) has been identified as the current resistant to DHPs and ω-conotoxin MVIIC (SNX-230, Neurex Corporation, Menlo Park, CA) (MVIIC; Hillyard et al., 1992 ; Zhang et al., 1993 ).

Techniques: Inhibition

Journal: The Journal of Neuroscience

Article Title: Functional Diversity of P-Type and R-Type Calcium Channels in Rat Cerebellar Neurons

doi: 10.1523/JNEUROSCI.16-20-06353.1996

Figure Lengend Snippet: Properties of a small current component inhibited rapidly and reversibly by MVIIC. Plots of peak Ba2+ current versus time from whole-cell recordings in the continuous presence of 3 μm nimodipine. Depolarizations 56 msec long were delivered every 10 sec. Vt = −10 mV;Vh = −90 mV. a, GVIA (1 μm) inhibited 17% of non-L current. Of this inhibition, 50% was recovered by wash and was reinhibited by a subsequent addition of the same concentration of GVIA. As shown by the fraction of current recovered after wash, 100 nm MVIIC inhibited reversibly both the component of current inhibited reversibly by GVIA and an additional 11% of total non-L current. Inset, Traces taken at times a, b, c, d (calibration: 50 pA, 20 msec). Cell T93F. b, The reversible inhibition by MVIIC is not occluded by low doses of ω-AgaIVA. In the presence of 50 nm ω-AgaIVA and 1 μm GVIA, MVIIC (3 μm) inhibited rapidly and reversibly 15% of total non-L current. Inset, Traces taken at times a, b, c, d. Calibration: 100 pA, 20 msec. Cell T91E.

Article Snippet: An additional component of HVA current (R-type) has been identified as the current resistant to DHPs and ω-conotoxin MVIIC (SNX-230, Neurex Corporation, Menlo Park, CA) (MVIIC; Hillyard et al., 1992 ; Zhang et al., 1993 ).

Techniques: Inhibition, Concentration Assay

Journal: The Journal of Neuroscience

Article Title: Functional Diversity of P-Type and R-Type Calcium Channels in Rat Cerebellar Neurons

doi: 10.1523/JNEUROSCI.16-20-06353.1996

Figure Lengend Snippet: Pharmacological properties of G1, G2, and G3 Ca 2+ channels

Article Snippet: An additional component of HVA current (R-type) has been identified as the current resistant to DHPs and ω-conotoxin MVIIC (SNX-230, Neurex Corporation, Menlo Park, CA) (MVIIC; Hillyard et al., 1992 ; Zhang et al., 1993 ).

Techniques: