Publication details

Acute effects of sigma receptor ligand haloperidol on isolated guinea pig heart

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Year of publication 2007
Type Conference abstract
MU Faculty or unit

Faculty of Medicine

Description Sigma receptor ligand haloperidol is a psychotropic drug used in treatment of various psychiatric disorders and agitation. Mechanisms of its life-threatening cardiovascular side effects (cardiac arrhythmias such as torsade de pointes, ventricular fibrillation or even cardiac arrest) are not elucidated yet. Therefore we examined the effects of haloperidol on 3-D electrogram of isolated guinea pig hearts. Six adult male guinea pigs were sacrificed under deep ether anesthesia. The hearts were perfused according to Langendorff with Krebs-Henseleit solution (K-H) at constant pressure (85mmHg) and 37C (CaCl2, 1.2 mM). The experiment consists of four 30min periods: control, 10nM haloperidol, wash-out, 10nM haloperidol. Ten successive RR intervals were averaged at the end of control (steady state heart rate). This value was used for normalization of heart rate during the rest of experiment. The incidence of arrhythmias was evaluated according to Lambeth Conventions. Normalized spontaneous heart rate showed a clear tendency to decrease during both haloperidol applications and this effect was partially reversible. In all hearts but one, typical arrhythmias were observed during both haloperidol periods (torsade de pointes, flutter and fibrillation); the hearts were mostly classified by number 4. Since nanomolar concentration is close to binding constant of sigma receptors, we can conclude that these effects are mediated by binding of the drug to cardiac sigma receptor and not by direct effect on membrane ionic channels. However, the putative downregulation of sigma receptors (known from rat heart) has not been proven because heart rate changes as well as incidence of arrhythmias were not diminished by the second haloperidol administration.
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