ISSN:
1432-2072
Keywords:
Morphine
;
Dopamine
;
Dopamine agonists
;
Haloperidol
;
Catalepsy
;
Stereotypy
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract Induction of catalepsy by morphine was evaluated after pretreatment with α-methyl-paratyrosine-methylester (αMpT). Under these experimental conditions morphine does not affect striatal DA release, as reported elsewhere (Moleman and Bruinvels, 1976). It was of interest, therefore, to assess whether dopaminergic systems were involved in morphine-induced catalepsy under these conditions. Administration of morphine (20 mg/kg, i.p.) 30 min after αMpT resulted in marked catalepsy, which was maximal 40–90 min after injection of morphine. Pretreatment with αMpT did not alter the induction of morphine catalepsy, but prolonged its duration. The effect of several drugs on the catalepsy induced by morphine after αMpT pretreatment was investigated. Naloxone, a specific morphine antagonist, entirely abolished the morphine-induced catalepsy, while apomorphine antagonized this catalepsy for 40 min when administered simultaneously with morphine. Amphetamine, on the other hand, potentiated morphine-indiced catalepsy and also produced catalepsy directly. Moreover, amphetamine-induced sniffing, a major sign of stereotypic behaviour, was antagonized by morphine. Atropine, an anticholinergic agent, and bicucculine, a GABA-receptor blocking agent, were ineffective against morphine-induced catalepsy. Catalepsy induced by administration of haloperidol (1 mg/kg, i.p.) 30 min after αMpT appeared to differ from morphine-induced catalepsy, since repeated testing was an important factor in the induction of catalepsy by haloperidol, but not by morphine. It is suggested that catalepsy may be induced by blockade of striatal DA receptors by neuroleptics or by activation of mesolimbic or mesocortical DA systems by morphine. The implications of this hypothesis are discussed in relation to the interaction of morphine with apomorphine and amphetamine in the induction of catalepsy and stereotypic behaviour.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00429176
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