We optically probe and electrically control a single artificial molecule containing a well defined number of electrons. Charge and spin dependent interdot quantum couplings are probed optically by adding a single electron-hole pair and detecting the emission from negatively charged exciton states. Coulomb- and Pauli-blockade effects are directly observed, and tunnel coupling and electrostatic charging energies are independently measured. The interdot quantum coupling is shown to be mediated by electron tunneling. Our results are in excellent accord with calculations that provide a complete picture of negative excitons and few-electron states in quantum dot molecules.

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We used in situ autoradiographic ligand binding methods to determine the occurrence and distribution of dopamine D₁ and D₂ 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 (D₂ high, D₁ low) to ventromedial (D₁ high, D₂ 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 D₂ (high in a dorsal band) and D₁ (high ventral to the D₂ band) distributions. As D₁ receptors are related to the direct and D₂ 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 D₂ 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.