Apomorphine-induced rotation in the substantia nigra lesioned rat : relationship to changes in biogenic amine receptors

Abstract

The relationship between the destruction of dopamine (DA) containing neurons, specific binding of [(3)H]-spiperone ([(3)]-SP), [(3)H]-quinclidynyl benzilate ([(3)H)-QNE) and ipsilateral rotation in response to apomorphine (1 mg/kg, IP) was studied in rats with unilateral electrolytic lesions (2 mA DC, 15 sec) of the substantia nigra. The lesioned animals with rotational behavior in response to apomorphine were classified into 3 groups according to the number of total turns. The [(3)H] - SP binging and [(3)H]-QNB binding to striatal membrane were carried out in both lesioned and nonlesioned side. It has been shown that in rate, group I (number of trunes < 10), group II (number of turns between 80-150) and group III (number of turns > 300), there are no significant different in the equilibrium dissociation constant values (K(,d) between the lesioned and nonlesioned side. However, the significant differences of the maximal receptor density (B(,MAX) of both [(3)H] -SP binding and [(3)H]-QNB binding between the two striatal sides were observed in group III animals. The B(,max) after [(3)H]-SP binding in the lesioned side is 357 ± 103 fmol/mg protein and in the nonlesioned side is 759 ± 119 fmol/mg protein, whereas in [(3)HO]-QNB binding the B(,max) in the lesioned side is 460.14 ± 26.56 fmol/mg protein and in the nonlesioned side is 371.71 + 16.9 fmol/mg protein. The results of the present study show that the number of dopamine receptor binding sites and muscarinic receptor binding sites are altered in the striatum of the rats with significant rotational behavior in response to apomorphine. Furthermore, the number of dopaminergic binding sites decrease, while the number of muscarinic receptor binding sites increase which indicates the reciprocal relationship between the function of dopaminergic and cholinergic systems in the striatum.