Simultaneous HPLC quantification of monoamines and metabolites in the blood-free rat cochlea.
Monoamine quantification in peripheral sensory receptors, such as the cochlea, is of major interest since monoamines could play a role in neurotransmission. A three-step biochemical protocol was developed to analyze monoamine content within the cochlea. Removal of the blood by aortic perfusion was carried out with an anticoagulant solution prior to the dissection of the cochlea from the temporal bone. The cochlear monoamines and some of their metabolites were then quantified, from homogenated cochlear tissue, by a new application of high performance liquid chromatography coupled to electrochemical detection. This method demonstrated enough sensitivity to detect norepinephrine (NE), dopamine (DA), serotonin (5-HT) and some of their metabolites (3,4-dihydroxyphenylacetic acid, DOPAC; homovanillic acid, HVA; and 5-hydroxyindole-3-acetic acid, 5-HIAA). Furthermore, it enabled the demonstration of noise-induced changes in the cochlear concentrations of NE, DA, DOPAC and HVA. In addition, the aortic perfusion allowed removal of the blood-borne 5-HT from the cochlea without inducing systemic alterations or monoamine degradation, as shown by the absence of effects on NE, DA, DOPAC, HVA or 5-HIAA concentrations. The present methodology may constitute a useful strategy to analyze monoamine turnover in the cochlea and other peripheral sensory receptors.
Vicente-Torres
Maria Angeles
MA
Center for Cell Culture (CAI) and Department of Surgery II (ORL), Medicine Faculty, University Complutense of Madrid, 28040 Madrid, Spain.
Gil-Loyzaga
Pablo
P
Carricondo
Francisco
F
Bartolomé
Maria Visitación
MV
D015102:3,4-Dihydroxyphenylacetic Acid / Q000378:metabolism; D000161:Acoustic Stimulation; D000818:Animals; D015306:Biogenic Monoamines / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D003051:Cochlea / Q000378:metabolism*; D004298:Dopamine / Q000378:metabolism; D004563:Electrochemistry / Q000379:methods; D006719:Homovanillic Acid / Q000378:metabolism; D006897:Hydroxyindoleacetic Acid / Q000378:metabolism; D008297:Male; D009638:Norepinephrine / Q000378:metabolism; D010477:Perfusion; D051381:Rats; D020318:Rats, Long-Evans; D012701:Serotonin / Q000378:metabolism
D015306:Biogenic Monoamines; D015102:3,4-Dihydroxyphenylacetic Acid; D012701:Serotonin; D006897:Hydroxyindoleacetic Acid; D004298:Dopamine; D009638:Norepinephrine; D006719:Homovanillic Acid