In Vivo Recording of the Adult Zebrafish Electrocardiogram - Zebrafish: Methods for Assessing Drug Safety and Toxicity - page 65

Table 6.1 Baseline Electrocardiographic Intervals of the Adult Male Zebrafish in the
Presence ( þ ) or Absence ( )ofm-Conotoxin GIIIB (CTX)

PR QRS QT RR

Males ( ) CTX (n ¼ 5) 52 19 26 3 229 11 348 43

Males ( þ ) CTX (n ¼ 58 110) 66 14 34 11 242 54 398 77

All values are presented in ms.

6.3 BASIC INTERVALS

Once we had optimized our ex aqua system to allow reproducible electrocardio-
graphic recordings, we were able to obtain technically satisfactory QT measurements
in over 80% of zebrafish tested (Fig. 6.2c). Synchronized video microscopy and
electrocardiographywas employed to demonstrate the precise correlation of electrical
and mechanical events (PQRS sequence with atrial and ventricular contraction).
The mean heart rate of the adult male zebrafish is 151 30 bpm (beats per minute),

and the baseline intervals are described in Table 6.1. Conotoxin did not affect heart
rate, QRS, or QT intervals, but did affect the PR interval prolonging it reproducibly by
about 27%.
We obtained normal zebrafish QTand RR data from a total of 110 zebrafish. Each
point in Fig. 6.3 is a three-beat average of QT and RR for a given fish. The data were

500

QT = 653 × RR

R 2 = 0.83 400

Figure 6.3 The dependence
of the QT interval on the basic
cycle length is shown in this
graph derived from recordings of
110 zebrafish. Each point
represents the average of three
consecutive RR and QT
measurements for a given fish.
The relationship is nearly linear
with R 2

300

200

¼ 0.83 for the equation

100

0.3 0.4 0.5 0.6
RR (s)

QT RR. (Figure

adapted fromMilan et al., 2006.)

634

¼