Table 5.
Cerebrovascular Contractile Pathways and Electro-Mechanical Coupling with Development
| Physiologic Variable | Fetus | Newborn | Adult | Reference |
|---|---|---|---|---|
| Ca2+ Sensitivity | >> | >> | Numerous reports Please see text | |
| Maximum tension (g)* | 6±1 (40) | 10±2 (67) | 15±2 | [17] |
| Maximum tension (g) | 2.4±0.5 (83) | 2.8±0.5 (96) | 2.9±1 | [17] |
| K+max Tension (g) | 1.0±0.1 (55) | 1.8±0.1 | [344] | |
| L-type Ca2+ Channel density (Bmax, fmol · mg protein−1) | 141±12 (243) | 58±8 | [45] | |
| Membrane Potential (mV) | −38.1±3.4c (84) | −45.4±2.5 | [345] | |
| Basal [Ca2+]i (10−9 M) in arterial segments | 130±5 (at 45 mmHg) (72) | 180±5 (at 75 mmHg) | [107] | |
| Basal [Ca2+]i in arterial segments† | 87±17 (81) | 107±15 | [346] | |
| Basal [Ca2+]i in arterial segments (10−9 M)† | 84±3 (153) | 55±2 | [347] | |
| Intracellular [Ca2+]i (10−9 M)† | 145±19 (95) | 157±15 | [345] | |
| Maximal 45Ca uptake in response to K+ depolarization (μM · g dry wt−1 · min−1) | 231±19a (152) | 152±13 | [348] | |
| % Inhibition Tension by Nifedipine | 100±10 | 100±10 | [46] | |
| pIC50 | 7.3±0.1 (‡) | 6.6±0.1 | [46] | |
| % Inhibition Fluorescence Ratio by Nifedipine | 100 ±10 | 100±10 | [46] | |
| K+ Stress(10−6 Dynes/cm2) | ||||
| pIC50 | 7.2±0.1 (‡) | 6.9±0.1 | [344] | |
| KCa Channel (% Inhibition Tension by NS-1619) | 100±10a (238) | 42±9 | [344] | |
| pIC50 | 8.2±0.1 (‡) | 7.6±0.1 | [344] | |
| KCa Channel (% Inhibition Fluorescence Ratio by NS-1619 | 37±6 (−) | unchanged | [344] | |
| pIC50 | 7.3±0.1 (‡) | – | ||
| KATP Channel (% Inhibition Tension by Pinacidil) | 100±10 | 100±10 | [344] | |
| pIC50 | 5.0±0.1 (‡) | 5.1±0.1 | [344] | |
| KATP Channel (% Inhibition Fluorescence Ratio by Pinacidil) | 72±8c (1600) | 4.5±0.5 | [344] | |
| pIC50 | 4.6±0.1 (− ‡) | – | ||
| Total Outward Current Density at 60 mV (pA/pF)† | 57.9 ±6.6a (153) | 37.9 ±1.8 | [345] | |
| Calcium Set Point (10−6 M)† | 4.7±0.1a (53) | 8.8±0.1 | [345] | |
| Native V1/2 Control (mV)† | 10.5±8.1a (31) | 34.0±36 | [349] | |
| Right-Shift by Dephos-phorylation State, ΔV1/2 (mV)† | 52.3±3.9a (173) | 30.3±3.4 | [349] | |
| V1/2 of Dephosphorylated Channels (mV)† | 62.8±5.2 (98) | 64.3±3.4 | [349] | |
| Endogenous Activated Kinase Shift, ΔVmax (mV)† | 38.8±4.6c (69) | 56.5±7.9 | [349] | |
| Channel-Associated PKA Shift, ΔVmax (mV)† | 36.4±2.8a (67) | 53.9±3.9 | [349] | |
| Channel-Associated PKG Shift, ΔVmax (mV)† | 32.1±3.2 (90) | 35.6±1.5 | [349] |
Values are mean ± SE of 5 or more in each group;
Values in parentheses represent % of adult value;
Significantly different from adult value:
a
P<.0.01;
c
P<0.05;
†
Basilar artery;
*
CCA;
‡
Because these are logarithmic functions, percent change is not an accurate or appropriate representation