Behavioural changes induced in conscious mice by intracerebroventricular injection of catecholamines, acetylcholine and 5-hydroxytryptamine.

1 A simple method of injecting soluble substances into the lateral ventricle of the brain of the conscious mouse is described. 2 The effect of various doses of noradrenaline, dopamine, acetylcholine, 5-hydroxytryptamine given into the right lateral brain ventricle were tested on locomotor and exploratory activities of mice. 3 Noradrenaline in a dose of 0.1 mug increased locomotor activity. This effect was prevented by phenoxybensamine but not by propranolol. 4 Higher doses of noradrenaline (1 or 10 mug) decreased locomotor and exploratory activities. Propranolol but not phenoxybenzamine abolished these effects. 5 Dopamine (0.1 or 1 mug) increased locomotor activity. The higher doses also induced tremor. 6 The highese dose of dopamine tested (10 mug) elicited stereotypical behaviour. 7 All the behavioural phenomena induced by 0.1 mug and 10 mug of dopamine were blocked by pimozide. 8 Acetylcholine (1 and 10 mug) and 5-hydroxytryptamine (1 mug) inhibited locomotor and exploratory activity. 9 The effects of 1 and 10 mug of acetylcholine were abolished by atropine (5 mg/kg i.p. Methysergide (5 mg/kg i.p.) had no influence on the effects of 5-hydroxytryptamine (1 mug).