Effect of pentoxifylline on α- and β-adrenoceptor sites in cerebral cortex, medial basal hypothalamus and pineal gland of the rat

Abstract The intraperitoneal injection of the methylxanthine derivative pentoxifylline [3,7-dimethyl-1-(5-oxo-hexyl)-xanthine] brought about, 3 hr later, a significant depression of α- and β-adrenoceptor sites in the cerebral cortex, and of β-adrenoceptor sites in medial basal hypothalamus and pineal gland, (assessed from the specific binding of radioactive dihydroergocryptine and dihydroalprenolol respectively). The changes in the density of binding sites were not accompanied by significant modifications of the K d ′s. Sympathetic denervation of the pineal gland by superior cervical ganglionectomy (SCGx) abolished the changes of β-adrenoceptor number in the pineal caused by pentoxifylline. The increase of α-adrenoceptor sites in the hypothalamus brought about by ganglionectomy was not affected by injection of pentoxifylline. Pentoxifylline did not compete in vitro for radioligand binding to brain membranes. These results suggest that methylxanthines depress brain adrenoceptor sites acutely, probably by down-regulation of receptors following the increase in catecholamine release caused by injection of the drug.