TABLE 1.Repeated cocaine administration in vivo altered the membrane properties and characteristics of HVA-Ca2+ potentials recorded in vitro
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Group | Saline pretreated (cells/rats) | Cocaine pretreated (cells/rats) |
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TTX + 4-AP | n = 8/8 | n = 11/9 |
Passive membrane properties | ||
RMP, mV | –79.0 ± 1.0 | –84.0 ± 1.0** |
Rin, mΩ | 47.6 ± 5.6 | 41.5 ± 2.5 |
τm, ms | 6.5 ± 1.0 | 4.3 ± 1.6 |
Active membrane properties | ||
Rheobase, nA | 0.9 ± 0.2 | 1.7 ± 0.3* |
Threshold, mV | –39.3 ± 2.9 | –32.4 ± 2.6 |
Amplitude of slow Ca2+ spike, mV | 24.3 ± 3.7 | 19.5 ± 2.5 |
Duration of slow Ca2+ spike, ms | 8.4 ± 1.2 | 6.1 ± 0.7 |
AHP of slow Ca2+ spike, mV | 22.3 ± 2.6 | 34.6 ± 3.2* |
Ca2+ Spike evoked in neurons, % | 100 (8/8) | 45.5 (5/11)* |
TEA | n = 12/10 | n = 10/8 |
Passive membrane properties | ||
RMP, mV | –76.0 ± 1.1 | –83.0 ± 1.4** |
Rin, mΩ | N/A + | N/A + |
τm, ms | N/A + | N/A + |
Active membrane properties | ||
Rheobase, nA | 0.6 ± 0.1 | 1.0 ± 0.2* |
Threshold, mV | N/A ++ | N/A ++ |
Amplitude of Ca2+ plateau potential, ms | N/A ++ | N/A ++ |
Duration at 1/2 amplitude, ms | 145.7 ± 24.7 | 55.5 ± 11.8** |
Secondary Ca2+ potential, % of cells | 100% (12/12) | 40% (4/10)# |
TTX + TEA + Csin | n = 16/8 | n = 15/7 |
Passive membrane properties | ||
RMP, mV | –68.7 ± 1.2 | –70.1 ± 0.7 |
Rin, mΩ | N/A + | N/A + |
τm, ms | N/A + | N/A + |
Active membrane properties | ||
Rheobase, nA | 0.9 ± 0.1 | 1.2 ± 0.1* |
Threshold, mV | –14.2 ± 1.3 | –11.6 ± 1.5 |
Amplitude of Ca2+ plateau potential, ms | 58.2 ± 1.8 | 54.5 ± 1.6 |
Duration at 1/2 amplitude, ms | 315.4 ± 24.3 | 210.1 ± 16.3** |
Total area of plateau potential, mV x ms | 38,016 ± 2,889 | 25,502 ± 2,042** |
+: Not available due to the use of short duration of current pulse (20 ms) ++: Not available due to difficulty in measuring
the threshold with TEA but without TTX. Values are means ± SE. 4-AP, 4-aminopyridine; RMP, resting membrane potential; Rin, input resistance; Tm, time constant.
* P < 0.05,
** P < 0.01, t-test,
# P < 0.05, χ2 test.