Effect of theophylline on binding of delta-9-tetrahydrocannabinol with mammalian neuronal and non-neuronal membranes.

Delta-9-tetrahydrocannabinol (THC) (1.6 x 10(-6)-13.33 x 10(-6) M) binds to neuronal and non-neuronal subcellular membranes in a biphasic manner. Its binding to neuronal membranes occur in the following order synaptosome > myelin > brain microsome and brain mitochondria. Unlike brain membranes binding of delta-9-THC is greater with liver microsome than liver mitochondria. Irrespective of membranes theophylline (Th) (11.0 x 10(-6) and 550.0 x 10(-6) M) increases the binding of delta-9-THC by exposure of more number of delta-9-THC binding sites on the subcellular membranes without affecting its binding affinity. Failure of Th (11.0 x 10(-6)-550.0 x 10(-6) M) to increase the binding of delta-9-THC (1.6 x 10(-6)-13.33 x 10(-6) M) in solubilized membranes suggests the involvement of membrane lipid in the Th-induced enhancement of delta-9-THC binding.

Delta-9-tetrahydrocannabinol and theophylline: in vitro interaction with bovine serum albumin.

Delta-9-tetrahydrocannabinol (delta-9-THC) (1.6 x 10(-6) M-13.33 x 10(-6) M) and theophylline (11.0 x 10(-6) M-550.0 x 10(-6) M) both bind to bovine serum albumin (BSA) and the binding is linear with respect to concentration. Further, it is observed that delta-9-THC both at low (1.6 x 10(-6) M and 6.4 x 10(-6) M) and high (13.33 x 10(-6) M) concentrations inhibits the binding of theophylline to BSA; whereas theophylline (11.0 x 10(-6) M-550.0 x 10(-6) M) promotes the binding of delta-9-THC to BSA. Kinetic analysis (using Scatchard plots) shows that delta-9-THC (1.6-13.33 x 10(-6) M) reduces the high affinity binding constant (K1) and the number of low affinity binding sites (n2) of theophylline to BSA; while its low affinity binding constant (K2) increased without affecting the number of high affinity binding sites (n1) under identical conditions. Further, it is observed that at lower concentrations (1.6-6.4 x 10(-6) M) delta-9-THC exerts greater effect on the binding parameters of theophylline-BSA interactions as compared to the effect observed with its high concentration (13.33 x 10(-6) M). Theophylline (11.0-550.0 x 10(-6) M). on the other hand, increases the affinity of the binding of delta-9-THC to BSA without changing the number of its binding sites. These suggest that (a) delta-9-THC and theophylline bind at different sites of BSA molecules and (b) the two drugs interfere with each other in their individual binding with the molecular orientation of the BSA molecule.

Long term effect of lithium on brain regional catecholamine metabolism.

Administration of LiCl (2-4 mmol/kg/day, po) to adult male albino rats for 7 consecutive days increased the catabolism of dopamine (DA) in striatum (ST) and noradrenaline (NA) in hypothalamus (H). Extension of the period of treatment with LiCl (2-4 mmol/kg/day, po) to 14 consecutive days increased catabolism of DA in CX (cerebral cortex) and PM (pons-medulla) and NA in H, and decreased metabolism of DA in ST and NA in PM. Further prolongation of treatment with LiCl (2 or 4 mmol/kg/day, po) for 21 consecutive days greatly affected DA and NA metabolism in the respective brain regions. These results, thus suggest that LiCl produces region specific differential action depending on its dosage and duration of treatment in catecholaminergic activity in rat brain.

In vivo distribution of lithium in plasma and brain.

A single administration of LiCl (0.5, 2 and 4 mmol/kg) to adult male albino rats produced a dose dependent increase of Li level in plasma, whole brain and brain regions. The concentration of Li in whole brain and brain regions was much less than that in plasma. Further, it is also found that concentration of Li in plasma reached a peak at 8 hr while that of Li in whole brain and brain regions reached a peak at 12 hr after the administration. The distribution and retention of Li was found to be highest in hypothalamus followed by striatum, pons-medulla, cerebellum and cerebral cortex. Daily administration of LiCl at a dose of 0.5 and 2 mmol/kg/day showed a time and dose dependent increase in plasma Li level up to a period of 21 consecutive days. But at higher dose (4 mmol/kg/day), on the other hand, under similar condition showed a time dependent increase in plasma Li level up to a period of 14 consecutive days and then gradually decreased with prolongation of treatment to 21 consecutive days. In brain there was no such decrease, rather increase in Li level was observed with the prolongation of duration of treatment, highest concentration of Li was found in hypothalamus and striatum than the rest of the brain regions. These results suggest that under short term treatment with LiCl, the clearance rate of Li in brain cell is much slower than that in plasma. Both single and long-term exposure of LiCl produces a dose dependent increase of Li in plasma, whole brain and brain regions.(ABSTRACT TRUNCATED AT 250 WORDS)