Objective    To study the biological effect of β3 adrenoceptoractivated electrophysiological activities in cardiac myocytes.      Methods    Changes of transient outward potassium (I

to

) and L-type calcium current (I

Ca-L

) in primary cultured guinea pig cardiacmyocytes were detected with the standard whole-cell patch clamp technique about 5-10 min before and after administration of β3 adrenoceptor agonist

4-[-[2-hydroxy-(3-chlorophenyl)ethyl-amino

]

propyl

]

phenoxyacetate

(BRL-37344; BRL).     Results    BRL could significantly increased the I

to

in guinea pig cardiac myocytes with the I-V curve up-moved. When the membrane potential reached to +80 mV

the density current increased from 6.11±1.03 pA/pF to 8.46±2.07 pA/pF (n=6

P=0.013 064). BRL (10

-6

mol/L) could significantly increase the I

Ca-L

in guinea pig cardiac myocytes

which was (2.30±0.75)fold higher than in control group（n=5，P=0.0063）. When the membrane potential increased to +10 mV

the  current

increased from 89.25±17.83 pA to 205.00±72.24 pA （n=5，P=0.006 3）.     Conclusion    BRL-37344 can increase the transient I

to

and I

Ca-L

thus further regulating the cardiac activities.