Mammal-like striatal functions in Anolis II.: Distribution of dopamine D1 and D2 receptors, and a laminar pattern of basal ganglia sub-systems

We used in situ autoradiographic ligand binding methods to determine the occurrence and distribution of dopamine D-1 and D-2 receptor sub-types in the anole lizard, Anolis carolinensis, Both were present and exhibited pharmacological 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 between D-2 (high in a dorsal band) and D-1 thigh ventral to the D-2 band) distributions. 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 striatal distributions of pre-proenkephalin mRNA, a marker for striatal efferents to the indirect BG subsystem in mammals, Here, too, there was a striking laminar pattern, with pre-proenkephalin mRNA in a band similar to that seen for Dg receptors. The crisp neuroanatomical separation between these classic BG subsystem markers in Anolis striatum make this species attractive for the study of such systems' functions during behavior. Copyright (C) 2001 S. Karger AG, Basel.