In vivo alteration of calcium turnover induced by reserpine in rat tissues

Abstract

when compared with rats injected acutely with saline. Since the apomorphine-induced sedation is considered to be mediated by presynaptic dopamine receptors, these data are evidence for the development of presynaptic supersensitivity following chronic haloperidol. Higher doses of apomorphine elevated locomotor activity to presedative levels indicating an activation of supersensitive postsynaptic dopamine receptors. In addition 2 out of 5 rats displayed obvious stereotypic behaviour.Combined injection of haloperidol and lithium daily for 34 days reversed the pre-and postsynaptic supersensitive responses to apomorphine. Apomorphine at 0.004 and 0.008 mg kg-' did not induce significant inhibition of locomotor activity as was seen in rats treated chronically with only haloperidol (Fig. 1). This supports previous electrophysiological data suggesting that lithium blocks the development of presynaptic dopamine receptor supersensitivity.The higher doses of apomorphine did not produce increases in locomotor activity in chronic haloperidol plus lithium treated rats (Fig. 1). On the contrary apomorphine (0.01 6 mg kg-l) induced sedation that was analogous to the responses seen in the control groups.In conclusion lithium appears to block the develop. ment of supersensitivity in both pre-and postsynaptic dopamine receptors. The chronic lithium regimen has been demonstrated to result in plasma lithium concen. trations in the therapeutic range of lithium in man (Allikments et al 1979). Therefore the stabilization of pre-and postsynaptic receptors by lithium may repre. sent an important mechanism in the clinical pharmacotherapy of manic-depressive disorders and tardive dyskinesia.

<b>AUGMENTATION OF MALONDIALDEHYDE PRODUCTION IN RESERPINIZED RABBIT PLATELETS BY ENHANCEMENT OF INTRACELLULAR CA²⁺-MOBILIZATION IN RESPONSE TO </b><b>THROMBIN </b>

“…As one of the possibilities it is conceivable that depletion of catecholamines caused by reserpine may influence calcium turnover in tissues through alteration of ,3-adrenergic stimulated parathormone secretion. Alterations of calcium storage and/or turnover have been reported in heart and vascular smooth muscles after reserpine pretreatment (5,18,19,35). These alterations are considered to be due to the reserpine-induced supersensitivit.y of these tissues.…”

“…It is thought that intracellular Ca" is regulated by cylic AMP. Dibutyryl cyclic AMP has been shown to impair the production of biologically active cyclic endoperoxides, and to exert its effect at the level of the phospholipases (15,18). Rittenhouse-Simmons and Deykin suggested that dibutyryl cyclic AMP might promote a compartmentalization of Ca", thereby inhibiting phospholipase activity (30).…”