The impact of organic inhibitors of the hyperpolarization activated current (Ih) on the electroretinogram (ERG) of rodents.
We have compared the effect of two distinct Ih inhibitors on the temporal properties of the ERG response that, as previously shown, correlates well with the HCN activation in rods. The present results confirm the notion that cilobradine is more effective than zatebradine in inducing bradycardia. Importantly, the doses of cilobradine that reduce the heart rate to values comparable to, or lower than, those obtained with higher doses of zatebradine have little effect on the frequency response of the ERG. While more potent than zatebradine in its bradycardic action, cilobradine appears comparatively less effective on the visual response. A possible explanation is that the affinity of cilobradine for the HCN channels in the heart is higher than that for the HCN channels of retinal neurons.
Maccarone
R
R
Dipartimento di Scienze e Tecnologie Biomediche, Università di L'Aquila, Italy.
Izzizzari
G
G
Gargini
C
C
Cervetto
L
L
Bisti
S
S
D000818:Animals; D001552:Benzazepines / Q000494:pharmacology*; D001919:Bradycardia / Q000139:chemically induced; D002316:Cardiotonic Agents / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004596:Electroretinography / Q000187:drug effects; D006321:Heart / Q000187:drug effects* / Q000502:physiology; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D007473:Ion Channels / Q000187:drug effects* / Q000502:physiology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D010880:Piperidines / Q000494:pharmacology; D051381:Rats; D020318:Rats, Long-Evans; D012160:Retina / Q000187:drug effects* / Q000502:physiology; D012165:Retinal Ganglion Cells / Q000187:drug effects / Q000502:physiology; D017948:Retinal Rod Photoreceptor Cells / Q000187:drug effects / Q000502:physiology; D013610:Tachycardia / Q000188:drug therapy
D001552:Benzazepines; D002316:Cardiotonic Agents; D007473:Ion Channels; D010880:Piperidines; C490484:cilobradine; C043636:zatebradine