Influence of Catecholamines on Cochlear Action Potentials

Catecholamines were injected intraarterially in guinea pigs using a rheological model described elsewhere. With this method, apart from the ear, only a relatively restricted area was perfused with catecholamines, and the amount eventually entering the general circulation was insufficient to change the normal BP. The induced vasoconstriction of the labyrinthine vessels affected the cochlear blood flow and caused an increase of 11.34 dB in the mean action potential threshold. When the rate of catecholamine infusion was increased, associating vasoconstriction of the cochlear vessels with increased BP, deterioration of the action potential threshold was limited to only 2 dB. However, decrease in the normal BP under the same experimental conditions raised the threshold by 21.67 dB. (Arch Otolaryngol 1983;109:530-532)