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. 2008 Mar 28;4(3):e1000036. doi: 10.1371/journal.pcbi.1000036

Table 1. Expected Traveling Time of Different Means of Signaling. (Calculated for 40 µm synapse-to-nucleus distance, which correspond to ∼30* µm synapse-to-soma distance).

Means Speed Time References
Transport vesicles 11–21 µm/hr 2–4 hr [14]
Transport granules** 122 µm/hr 20 min [15]
Diffusion of CaM D = 2.5×10−9 cm2/s 48 min [8]
Diffusion of kinase-bound CaM D =  5×10−8 cm2/s 2.7 min [8]
Regenerative Calcium waves*** ∼0.1 µm/ms 0.4 sec [16]
Electrotonic signal 81 µm/ms 0.5 ms ****

*: The distance from the soma to the most proximal spine was reported to be 39.7±12.1 µm [9].

**: Average maximal speed of granules traveling along a dendrite is 0.034±0.025 µm/s [15].

***: Regenerative Calcium waves were ruled out as means for synapse-to-CREB signaling [1].

****: Electrotonic speed (θ) was calculated according to the parameters in Table 2 using the conventional definition Inline graphic given by the classic cable theory.