{'fraction_non_alphanumeric': 0.03529411764705882, 'fraction_numerical': 0.01238390092879257, 'mean_word_length': 5.622950819672131, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Role of calmodulin-dependent phosphorylation in chronic sulpiride-induced striatal dopamine receptor supersensitivity.

In the present study we investigated several pharmacological and biochemical parameters in striatal preparations of rats which were treated chronically with a selective D2 receptor antagonist, sulpiride. Chronic sulpiride treatment in rats (50 mg/kg s.c. for 20 days) potentiated stereotyped responses by apomorphine (0.1-2.5 mg/kg). In association with the dopaminergic behavior supersensitivity, we observed a significant increase in the number of specific [3H]spiperone binding sites (D2 receptors) in the striatum without affecting the ligand binding affinity constant. We further observed a marked increase in the sensitivity of the protein kinase to calcium (0.1-0.5 mM) and calmodulin (1 micrograms) in these rats. The D1 receptor functions which are represented by the basal and dopamine-stimulated adenylate cyclase and the cyclic AMP-dependent protein kinase activity were not changed after chronic sulpiride treatment. In vitro, pretreatment of striatal particulates with the Ca++-chelating agent ethylene glycol bis(beta-aminoethyl ether)-N,N'-tetraacetic acid (1.2 mM) to remove endogenous Ca++ and calmodulin or the addition of Ca++ and calmodulin to the striatal particulates did not affect the binding affinities of dopamine agonists and antagonists to the receptors. Therefore, the increased sensitivity of the calmodulin-dependent system seen in chronic sulpiride-treated rats correlates with the increased number of D2 receptors in striatal dopamine receptor supersensitivity.