Dopamine transporter binding without cocaine-like behavioral effects: synthesis and evaluation of benztropine analogs alone and in combination with cocaine in rodents.

Rationale: Previous SAR studies demonstrated that small halogen substitutions on the diphenylether system of benztropine (BZT), such as a para-Cl group, retained high affinity at the cocaine binding site on the dopamine transporter. Despite this high affinity, the compounds generally had behavioral effects different from those of cocaine. However, compounds with meta-Cl substitutions had effects more similar to those of cocaine.

Discriminative stimulus effects of putative D3 dopamine receptor agonists in rats.

Three separate groups of rats were trained to discriminate the putative D3 dopamine receptor agonists (+/-)-7-hydroxydipropylaminotetralin (7-OH-DPAT) (0.03 mg/kg), PD 128,907 (1.0 mg/kg) and quinpirole (0.

Choice under concurrent VI schedules: comparison of behavior maintained by cocaine or food.

Previous research has shown that concurrent schedule responding maintained by cocaine under short variable-interval (VI) schedules is well described by the generalized matching law. That is, drug-maintained behavior was apportioned in accordance with relative frequency of reinforcement. The purpose of the present experiment was to examine the ability of the generalized matching law to account for choice under longer VI schedules of cocaine availability, and to compare cocaine-maintained to food-maintained behavior in this regard.

Characterization of unconditioned behavioral effects of dopamine D3/D2 receptor agonists.

A series of experiments examined the ability of dopamine D3/D2 receptor agonists [(+)-(4aR,10bR)-3,4,4a,10b-tetrahydro-4-propyl-2H,5H-[1]b enzopyrano-[4,3-b]-1,4-oxazin-9-ol hydrochloride (PD 128,907), (+/-)-7-hydroxy-dipropylaminotetralin hydrobromide (7-OH-DPAT), quinpirole and bromocriptine] to produce a variety of dopaminergically mediated behaviors. The effects of these drugs with selectivity for D3/D2 receptors over D1 receptors were compared with those produced by the selective D1 agonists [(+/-)-Phenyl-2,3,4,5-tetrahydro-(1H)-3-benzazepine-7,8-diol hydrochloride (SKF 38393), (+/-)-6-Chloro-7,8-dihydroxy-3-allyl-1-phenyl-2,3,4,5-tetrahydro-1H-3-be nzazepine hydrobromide (SKF 82958)], a nonselective dopaminergic agonist (apomorphine), and an indirect dopamine agonist (cocaine). The D3/D2 agonists decreased locomotor activity, had no effect on gnawing and only inconsistently induced climbing in mice.