Arch Ital Biol
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1. The Purkinje (P)-cells of the cerebellar vermis, which exert a prominent influence on posture as well as on the gain of vestibulospinal (VS) reflexes, are under the control not only of the classic mossy fibers and climbing fibers which liberate excitatory amino acids as neurotransmitter, but also of cholinergic afferents. The role of these afferents was investigated in precollicular decerebrate cats by using the method of local microinjection of cholinergic agents into appropriate areas of the cerebellar cortex. 2. ⋯ On the other hand opposite effects, characterized by an increased postural activity in the ipsilateral forelimb associated with a decreased activity in the contralateral forelimb, as well as by a reduced gain of the EMG responses of the triceps brachii of both sides to animal tilt were observed in other experiments after local microinjection of the muscarinic antagonist scopolamine (0.25 microliter at 4-8 micrograms/microliters saline). Evidence for muscarinic supersensitivity was obtained following repetitive injections of scopolamine into the cerebellar vermis. 4. The area which upon injection of the cholinergic agents modified the postural activity as well as the gain of the VS reflexes was located within the third and/or the fourth folium rostral to the fissura prima (culmen), at the laterality of 1.4-1.8 mm with respect to the midline.(ABSTRACT TRUNCATED AT 400 WORDS)