Mammal-like striatal functions in Anolis II. Distribution of dopamine D-1 and D-2 receptors, and a laminar pattern of basal ganglia sub-systems

We used in situ autoradiographic ligand binding methods to determine the oc currence and distribution of dopamine D-1 and D-2 receptor sub-types in the anole lizard, Anolis carolinensis, Both were present and exhibited pharmac ological specificity characteristics similar to those described for mammals . However, unlike in mammals where in the neostriatum [outside the nucleus accumbens/olfactory tubercle complex (NA/OT)] these receptors exhibit only slight dorsolateral (D-2 high, D-1 low) to ventromedial (D-1 high, D-2 low) gradients that co-mingle extensively, in the anole striatum outside the NA /OT there was a striking laminar pattern, with little if any overlap betwee n D-2 (high in a dorsal band) and D-1 thigh ventral to the D-2 band) distri butions. As D-1 receptors are related to the direct and D-2 to the indirect basal ganglia (BG) subsystems in mammals, we also determined anole striata l distributions of pre-proenkephalin mRNA, a marker for striatal efferents to the indirect BG subsystem in mammals, Here, too, there was a striking la minar pattern, with pre-proenkephalin mRNA in a band similar to that seen f or Dg receptors. The crisp neuroanatomical separation between these classic BG subsystem markers in Anolis striatum make this species attractive for t he study of such systems' functions during behavior. Copyright (C) 2001 S. Karger AG, Basel.