  An analysis of the X-ray variability of the low luminosity Seyfert nucleus
NGC 4395, based on a long XMM-Newton observation, is presented. The power
spectrum shows a clear break from a flat spectrum (alpha ~ 1) to a steeper
spectrum (alpha ~ 2) at a frequency f_br = 0.5 - 3.0 * 10^-3 Hz, comparable to
the highest characteristic frequency found previously in a Seyfert galaxy. This
extends the measured M_BH-f_br values to lower M_BH than previous studies of
Seyfert galaxies, and is consistent with an inverse scaling of variability
frequency with black hole mass. The variations observed are among the most
violent seen in an AGN to date, with the fractional rms amplitude (F_var)
exceeding 100 per cent in the softest band. The amplitude of the variations
seems intrinsically higher in NGC 4395 than most other Seyferts, even after
accounting for the differences in characteristic frequencies. The origin of
this difference is not clear, but it is unlikely to be a high accretion rate
(L/L_Edd < 20 per cent for NGC 4395). The variations clearly follow the linear
rms-flux relation, further supporting the idea that this is a ubiquitous
characteristics of accreting black holes. The variations are highly coherent
between different energy bands with any frequency-dependent time delay limited
to <1 per cent.
