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Modifications in muscarinic, dopaminergic and serotonergic receptors concentrations in the hippocampus and striatum of epileptic rats.

Mendes de Freitas R, Aguiar LM, Vasconcelos SM, Sousa FC, Viana GS, Fonteles MM

Department of Physiology and Pharmacology, Laboratory of Neuropharmacology, School of Medicine, Federal University of Ceará, Rua Cel. Nunes de Melo 1127, Fortaleza 60431-970, CE, Brazil. rivmendes@bol.com.br

The present study was undertaken in order to investigate the muscarinic (M(1)), dopaminergic (D(1) and D(2)) and serotonergic (5-HT(2)) receptors densities in hippocampus and striatum of Wistar rats after status epilepticus (SE) induced by pilocarpine. The control group was treated with 0.9% saline. An other group of rats received pilocarpine (400 mg/kg, s.c.) and both groups were sacrificed 1 h after treatment. The results have shown that pilocarpine administration and resulting SE produced a downregulation of M(1) receptor in hippocampus (41%) and striatum (51%) and an increase in the dissociation constant (K(d)) values in striatum (42%) alone. In both areas the 5-HT(2) receptor density remained unaltered, but a reduction (50%) and an increase (15%) in the K(d) values were detected in striatum and hippocampus, respectively. D(1) and D(2) receptor densities in hippocampus and striatum remained unaltered meanwhile K(d) values for D(1) receptor declined significantly, 33% in hippocampus and 26% in striatum. Similarly, K(d) values for D(2) decreased 55% in hippocampus and 52% in striatum. From the preceding results, it is clear that there is a possible relation between alterations in muscarinic receptor density and others systems studied as well as they suggest that changes in dissociation constant can be responsible for the establishment of pilocarpine-induced SE by altering the affinity of neurotransmitters such as acetylcholine, dopamine and serotonine.

Published 7 November 2005 in Life Sci, 78(3): 253-8.
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