Cocaine inhibits extraneuronal O-methylation of exogenous norepinephrine in nasal and oral tissues of the rabbit.

Nasal mucosa (respiratory and olfactory) and lingual gingiva of the rabbit were depleted of their sympathetic nerves by superior cervical ganglionectomy. In the innervated nasal mucosa, exogenous tritiated norepinephrine (3H-NE) was metabolised mainly to tritiated 3,4-dihydroxyphenylethylene glycol (3HDOPEG) and 3,4-dihydroxy mandelic acid (3HDOMA), whereas after denervation it was metabolised mainly to tritiated normetanephrine (3HNMN). In the denervated mucosa, cocaine (30 umol/1) inhibited 3HNMN formation by 50-60%. Cocaine also inhibited 3HNMN formation by 60% in the denervated lingual gingiva. It is concluded that the tissues metabolise 3H-NE via a cocaine-sensitive extraneuronal uptake and O-methylating system similar to that which has been shown to be present in dental pulp.