A series of variously N-substituted 2-aminotetralins having OH groups at 5 and 6 and at 6 and 7 positions, as well as nonoxygenated systems, has been evaluated for central dopaminergic effects. Stereotypical behavioral effects (sniffing, compulsive gnawing, and hyperactivity) produced by direct intracerebral administration of some of the agents were shown to differ strikingly from responses resulting from peripheral administration. The centrally mediated responses of hyperactivity and sterotypical gnawing-biting head and limb movements were shown to be separable in some test compounds. An improved route to 2-aminotetralin systems has been utilized for some of the compounds, which involves Pummerer rearrangement and cyclization of beta-keto sulfoxides and reductive amination of beta-tetralones with a NaBH4-carboxylic acid complex.

A number of dopamine agonists were applied intracerebrally to the nucleus accumbens and caudate-putamen of rat in an attempt to differentiate the dopamine mechanisms in these nuclei which mediate hyperactivity and stereotyped behaviour. The major effect of dopamine was to induce hyperactivity from the nucleus accumbens and stereotypy from the caudateputamen; N-n-propyl-norapomorphine induced hyperactivity and stereotypy from the nucleus accumbens whilst apomorphine induced a marked stereotypy from the caudateputamen, modest stereotypy from the nucleus accumbens and no hyperactivity. In contrast to apomorphine, 2-(NN-dipropyl)amino-5,6-dihydroxy TN: induced a more marked stereotypy from the nucleus accumbens and, again, no hyperactivity. The major effect of 2-(NN-diethyl)amino-5,6-dihydroxy TN was to cause an intense hyperactivity from the

The characteristics of [3H]hemicholinium-3 ([3H]HC-3) interactions with rat striatal membranes were investigated. Under the described assay conditions, [3H]-HC-3 binds with a saturable population of membrane binding sites having the following regional distribution: striatum much greater than hippocampus greater than or equal to cerebral cortex greater than cerebellum. The specific binding of [3H]HC-3 showed an obligatory requirement for NaCl; other halide salts of sodium or KCl failed to substitute for NaCl. The Scatchard transformation of saturation isotherm data generated a curvilinear plot with high- and low-affinity components of binding. The dissociation of [3H]HC-3 at infinite dilution was also multiexponential. The dissociation could, however, be accelerated if unlabeled HC-3 was included in the diluting buffer, and this increase in dissociation appeared to be dependent on the concentrations of unlabeled HC-3 used, with the maximal increase demonstrable at 100 nM. The dissociation was also dependent on the fractional saturation of binding sites with labeled HC-3, such that, at higher fractional saturation of binding sites, the overall dissociation was faster and the difference in the dissociation observed between "dilution only" and "dilution + unlabeled HC-3" was reduced. This occupancy-dependent change in dissociation could also be influenced by temperature and pH. Based on the results of these kinetic studies, the steady-state [3H]HC-3 binding data were analyzed for a homogeneous population of binding sites undergoing site-site interactions of the negative cooperative type. Such an analysis yielded a KD of 9.3 nM for the high-affinity state and a KD of 22.8 nM for the low-affinity state of binding sites, with a Bmax of 434 fmol/mg of protein. Competitive binding studies showed that unlabeled HC-3 was most potent in displacing [3H]HC-3, followed by choline. Other drugs known to have little influence on the synaptosomal sodium-dependent high-affinity choline uptake system (SDHACU) had no significant effect on [3H]HC-3 binding sites. Similarities in ionic dependencies, regional distributions, and pharmacological selectivities of [3H]HC-3 binding with synaptosomal SDHACU suggest that [3H]HC-3 selectively labels SDHACU sites located on presynaptic cholinergic neurons in rat CNS. We suggest that the two affinity states of [3H]HC-3 binding sites represent the different "functional" states of the SDHACU system. The binding of HC-3 (or choline) with the high-affinity state of the binding sites induces negative cooperative site-site interactions among the binding sites, resulting in the formation of a low-affinity binding state.(ABSTRACT TRUNCATED AT 400 WORDS)

No abstract

No abstract