Pharmacological and functional data suggest the existence of uridine (Urd) receptors in the
central nervous system (CNS). In the present study, simultaneous extracellular single unit
recording and microiontophoretic injection of the pyrimidine nucleoside Urd was used to
provide evidence for the presence of Urd-sensitive neurons in the thalamus and the cerebral
cortex of Long Evans rats. Twenty-two neurons in the thalamus (24% of recorded neurons)
and 17 neurons in the cortex (55%) responded to the direct iontophoresis of Urd. The …

Fig. 1. Representative sample of the effect of Urd (A1: excitatory effects on maintained firing
activity, A3: inhibitory effects on maintained firing activity), UTP (A2) and Ado (A4) on the
firing rate of single thalamic neurons with average amplitude of action potentials and overall
effects normalized on the total pool of recorded neurons expressed in mean percentage of
control firing rate±SEM (Part A). Schematic presentation of recording sites superimposed on
the representative coronal plane (AP:-3.6 mm) of the standard stereotaxic rat brain atlas …