Shaking behaviour induced by putrescine in naive rats: a pharmacological and histological study.

In untreated rats, the intraperitoneal injection of putrescine evoked a typical wet-dog shake response, that was maximal at a dose of 300 mg/kg and at room temperature (22 degrees) (number of shakes: 84.00 +/- 17.90/hr). In a hot environment (30 degrees) the number of shakes was markedly reduced (26.90 +/- 5.19/hr). The putrescine-induced shaking behaviour was unaffected by atropine, bicuculline, chlorpheniramine, cimetidine, methysergide, naloxone and noradrenaline, but was markedly antagonized by morphine. Naloxone pretreatment nullified the antagonistic activity of morphine. Histological studies showed marked alterations in brain vascular permeability, which was increased by putrescine. Morphine completely prevented this putrescine-induced vascular effect. These results suggest a correlation between WDS produced by putrescine and increase in brain vascular permeability. Furthermore they show that morphine can affect brain vascular permeability.