EFFECTS OF CATECHOLAMINERGIC OR TRYPTAMINERGIC AGENTS ON THE MORPHINE-INDUCED STRAUB TAIL REACTION

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Abstract
An investigation was made of monoamine-related agents on the Straub tail reaction (STR) due to central excitatory effect of morphine (10 mg/kg). Apomorphine (10 mg/kg) showed a tendency to enhance the STR, and L-dopa (150 mg/kg) and methamphetamine (5 and 10 mg/kg) produced a significant increase in the STR. Phenoxybenzamine and propranolol induced the inhibition of the STR to a large extent. Diethyldithiocarbamate (250 mg/kg) and disulfiram (200 and 400 mg/kg) had no influence on the STR. .alpha.-Methyl-p-tyrosine (100 and 400 mg/kg) reduced the STR. L-5-Hydroxytryptophan [L-5-HTP] (100 mg/kg) inhibited the STR significantly. Isocarboxazid (50 mg/kg), nialamide (50 and 100 mg/kg) and tranylcypromine (10 and 25 mg/kg) did not influence the STR. Biochemical investigations showed that morphine (10 and 20 mg/kg) decreased the 5-hydroxytryptamine (5-HT) content of the lumbosacral cord significantly, although no alteration of 5-HT content occurred in various sites of the brain, compared to a vehicle-treated group. Morphine (10 and 20 mg/kg) did not act on the dopamine or norepinephrine content of various sites of the brain and spinal cord. The STR is the result of an increase of catecholaminergic activity and/or a decrease in tryptaminergic activity in the CNS of mice.