Metatyrosine‐Induced Reversal of the Suppression of the Conditioned Avoidance Response in Reserpine‐Treated Rats

Publisher Website
Google Scholar
Abstract
DL‐Metatyrosine (200 mg/kg intraperitoneally) administration after peripheral DOPA decarboxylase inhibition caused a temporary reversal of reserpine‐induced (5 mg/kg intraperitoneally) suppression of a conditioned avoidance response in the rat, both with and without pretreatment with a dopamine‐β‐hydroxylase inhibitor, bis‐(4‐methyl‐1‐homopiperazinylthiocarbonyl)‐disulfide, (FLA‐63, 10 mg/kg intraperitoneally); but the duration of the reversal was shorter after FLA‐63. After the injection of DL‐metatyrosine there was a rapid and marked accumulation of metatyramine and a smaller accumulation of the β‐hydroxylated metabolite, metaoctopamine. FLA‐63 pretreatment prevented the metaoctopamine accumulation. Some of the behavioural effects observed after DL‐metatyrosine may be due to displacement of endogenous noradrenaline not depleted by reserpine. The increase in locomotor activity after DL‐metatyrosine was not affected by the dopamine‐β‐hydroxylase inhibitor. The results provide further support for the hypothesis that dopamine is important for elementary motor functions (e.g. locomotor activity) whilst additional noradrenaline receptor stimulation is essential for more complex and integrated hebaviour (e.g. a conditioned avoidance response).