S33138 [N-[4-[2-[(3aS,9bR)-8-cyano-1,3a,4,9b-tetrahydro[1]-benzopyrano[3,4-c]pyrrol-2(3H)-yl)-ethyl]phenylacetamide], a preferential dopamine D3 versus D2 receptor antagonist and potential antipsychotic agent. II. A neurochemical, electrophysiological and behavioral characterization in vivo

J Pharmacol Exp Ther. 2008 Feb;324(2):600-11. doi: 10.1124/jpet.107.132563. Epub 2007 Nov 16.


The novel benzopyranopyrrolidine, S33138 [N-[4-[2-[(3aS,9bR)-8-cyano-1,3a,4,9b-tetrahydro[1]benzopyrano[3,4-c]pyrrol-2(3H)-yl)-ethyl]phenylacetamide], is a preferential antagonist of cloned human D(3) versus D(2L) and D(2S) receptors. In mice, S33138 (0.04-2.5 mg/kg i.p.) increased levels of mRNA encoding c-fos in D(3) receptor-rich Isles of Calleja and nucleus accumbens more potently than in D(2) receptor-rich striatum. Furthermore, chronic (3 weeks) administration of S33138 to rats reduced the number of spontaneously active dopaminergic neurones in the ventral tegmental area (0.16-10.0 p.o.) more potently than in the substantia nigra (10.0). In primates treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, antiparkinson actions of the D(3)/D(2) agonist, ropinirole, were potentiated by low doses of S33138 (0.01-0.16 p.o.) but diminished by a high dose (2.5). Consistent with antagonism of postsynaptic D(3)/D(2) sites, S33138 attenuated hypothermia and yawns elicited by the D(3)/D(2) agonist 7-OH-DPAT [(+)-7-dihydroxy-2-(di-n-propylamino)-tetralin] in rats, and it blocked (0.01-0.63, s.c.) discriminative properties of PD128,907 [(+)-(4aR,10bR)-3,4, 4a,10b-tetrahydro-4-propyl-2H,5H-[1]benzopyrano-[4,3-b]-1,4-oxazin-9-ol; trans-N-[4-[2-(6-cyano-1,2,3,4-tetrahydroisoquinolin-2-yl)ethyl]cyclohexyl]-4-quinolininecarboxamide]. Suggesting antagonist properties at D(3)/D(2) autoreceptors, S33138 prevented (0.16-2.5 s.c.) the inhibitory influence of PD128,907 upon dopamine release in frontal cortex, nucleus accumbens, and striatum and abolished (0.004-0.25 i.v.) its inhibition of ventral tegmental dopaminergic neuron firing. At higher doses, antagonist actions of S33138 (0.5-4.0 i.v.) at alpha(2C)-adrenoceptors were revealed by an increased firing rate of adrenergic perikarya. Finally, antagonism of 5-hydroxytryptamine (5-HT(2A) and 5-HT(7)) receptors was shown by blockade of 1-[2,5-dimethoxy-4-iodophenyl]-2-aminopropane-induced head twitches (0.63-10.0 s.c.) and 5-carboxytryptamine-induced hypothermia (2.5-20.0 i.p.), respectively. In conclusion, S33138 displays modest antagonist properties at central alpha(2C)-adrenoceptors, 5-HT(2A) and 5-HT(7) receptors. Furthermore, in line with its in vitro actions, it more potently blocks cerebral populations of D(3) versus D(2) receptors.

Publication types

  • Comparative Study

MeSH terms

  • Animals
  • Antipsychotic Agents / chemistry
  • Antipsychotic Agents / metabolism
  • Antipsychotic Agents / pharmacology*
  • Callithrix
  • Corpus Striatum / drug effects
  • Corpus Striatum / metabolism
  • Dopamine Antagonists / chemistry
  • Dopamine Antagonists / metabolism
  • Dopamine Antagonists / pharmacology*
  • Dopamine D2 Receptor Antagonists
  • Electrophysiology
  • Guinea Pigs
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Motor Activity / drug effects*
  • Motor Activity / physiology
  • Rats
  • Rats, Sprague-Dawley
  • Rats, Wistar
  • Receptors, Dopamine D2 / physiology*
  • Receptors, Dopamine D3 / antagonists & inhibitors
  • Receptors, Dopamine D3 / physiology*


  • Antipsychotic Agents
  • Dopamine Antagonists
  • Dopamine D2 Receptor Antagonists
  • Receptors, Dopamine D2
  • Receptors, Dopamine D3