1. Clonidine (4 μg/kg) given intracisternally to anaesthetized cats inhibited brain stem-evoked parasympathetic submaxillary or parotid salivation by 62% at 5 Hz and 44% at 15 Hz.
2. The inhibitory action of clonidine on salivation was equally prevented by pretreatment with either intracisternal yohimbine (175 μg/kg) or phentolamine (250 μg/kg), used as preferential pre- and post-synaptic α-adrenoreceptor-blocking drugs respectively.
3. The inhibition of centrally evoked salivation by clonidine is due to an action on α-adrenoreceptors but no clear evidence was obtained to indicate whether these were located pre- or post- synaptically. This is in contrast to the preferential presynaptic action of clonidine in reducing peripheral parasympathetic nerve-evoked salivation.