Ergometrine induced locomotor activity following intracerebral injection into the nucleus accumbens

Abstract

Ergometrine was injected in rats intraperitoneally or intravenously and also directly into different parts of the brain. After peripheral injection the animals showed a characteristics crawling behaviour. This behaviour was reversed by apomorphine. Following bilateral injection of ergometrine into the nucleus accumbens, the rats showed a biphasic response. After a period, during which sedation and ptosis predominated, their followed a strong and long-lasting locomotor stimulation, which started and finished in most cases rather abruptly. When the doses of ergometrine were lowered the locomotor activity remained at a constant high level, but the duration was shorter. Bilateral injection of ergometrine into the caudate nucleus or into the septum had only little or no stimulant effect on locomotor activity. The strong locomotor stimulation following injection of ergometrine into the nucleus accumbens was inhibited by low doses of haloperidol and pimozide given intraperitoneally. Pretreatment with α-methyl-p-tyrosine had no influence on this motor activity. Ergometrine injected unilaterally into the nucleus accumbens and into the caudate nucleus caused only a slight enhanced locomotor activity and turning to the contralateral side. The possible mode of action of ergometrine is discussed.