Involvement of Central Presynaptic Noradrenergic Neuron Activity in Head Twitches Induced by Bromocriptine in Rats

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The study was carried out in an attempt to understand the contribution of endogenous catecholamine on head twitches induced by bromocriptine (BRC), a dopamine D -2 recepter agonist, in rats. Intraperitoneal (I.p.) of BRC (1-10 mg/kg) induced head twitches which are prominent at 2.5mg/kg. The pretreatment with α-methyl-p-tyrosine (α-MPT ; 200 and 400 mg/kg) inhibited in dose-dependet manner, whereas reserpine (2mg/kg) did not affet but reserpine plus α-MPT (200mg/kg) markedly decreased. Apomorphine (0.1 and 1 mg/kg) tended to increase the behavior but no significant. Thyrotropin releasing hormone (TRH ; 5mg/kg) potentiated the behavior, whereas clonidine (0.05 and 1mg/kg) completely blocked, but phentolamine (10 mg/kg), a α-1 and α-2 receptor blocker, and yohimbine (1mg/kg), a direct α-2 recepter blocker, did not affect. Yonimbine, however, reversed inhibitory effect of low dose of clonidine (0.05 mg/kg). These results suggest that endogenous catecholamine especially noradrenarine synthesis and release mediated in presynaptic sites may be involved in head twitches induced by BRC.
Yamaguchi University Graduate School of Medicineの論文