Abstract
1 The relative potencies of methotrimeprazine, (+)-methotrimeprazine, (±)-10-(3-dimethylamino-2-methylpropyl)-2-valeroyl phenothiazine hydrochloride (M & B 18,706) and (+)-M & B 18,706 in reducing the pressor action of noradrenaline in the spinal cat, reducing intercollicular decerebrate rigidity, and muscle spindle afferent activity have been studied.
2 Methotrimeprazine was eight times as potent as (+)-methotrimeprazine in reducing the pressor action of noradrenaline and six times as potent in reducing decerebrate rigidity. M & B 18,706 was also eight times as potent as (+)-M & B 18,706 in reducing the pressor action of noradrenaline and six times as potent in reducing decerebrate rigidity.
3 For the above compounds and chlorpromazine there was a significant correlation between the effective doses for the inhibition of the pressor action of noradrenaline and for the reduction of decerebrate rigidity.
4 The doses which reduced decerebrate rigidity were similar to those that reduced muscle spindle afferent discharge. It is likely that these drugs reduce decerebrate rigidity by inhibiting fusimotor activity.
5 Desipramine increased decerebrate rigidity and increased spindle afferent discharge.
6 It is thought that the phenothiazine derivatives studied reduce decerebrate rigidity and spindle afferent discharge by inhibiting receptors for noradrenaline in the central nervous system.
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Selected References
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