Enhanced pilocarpine-induced oral activity responses in neonatal 6-OHDA treated rats (original) (raw)

1993, Pharmacology Biochemistry and Behavior

KOSTRZEWA, R. M. AND D. NEELY. Enhanced pilocarpine-induced oral activity responses in neonatal 6-OHDA treated rats. PHARMACOL BIOCHEM BEHAV 45(3) 737-740, 1993.-Neonatal destruction of rat nigrostriatal dopaminergic fibers results in an enhanced oral activity response to both dopamine (DA) D~ and serotonin (5-HT) agonists. Because cholinergic systems represent another one of the neural circuits involved in oral behavior, it was of interest to determine whether muscarinic receptors might also be sensitized in the lesioned rats. At 3 days after birth, rats were pretreated with desipramine HC1 (20 mg/kg, IP) 1 h before 6-hydroxydopamine (6-OHDA) HBr (100 tLg in each lateral ventricle) or salineascorbic acid (0.1%) vehicle. Between 2 and 4 months, behavioral supersensitivity to a D~ agonist (SK&F 38393) and 5-HT agonist (m-chlorophenylpiperazine; m-CPP) was established before rats were challenged with the muscarinic receptor agonist, pilocarpine HC1 (0.125 to 10.0 mg/kg, IP). The pilocarpine dose-effect curve was shifted to the left, with a maximal effect of 63.7 =1= 8.6 oral movements being produced by a 1.0 mg/kg pilocarpine HC1 dose in the 6-OHDA lesioned rats, versus 15.0 =t = 2.4 oral movements in the control group (p < 0.001). The enhanced response to pilocarpine was attenuated by the muscarinic receptor antagonist, scopolamine HCI (0.1 mg/kg IP). These findings indicate that neonatal 6-OHDA treatment produces supersensitization of muscarinic receptors in rats.

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