Ketamine interacts with the noradrenaline transporter at a site partly overlapping the desipramine binding site

Abstract

Effects of the intravenous anaesthetic ketamine on the desipramine-sensitive noradrenaline transporter (NAT) were examined in cultured bovine adrenal medullary cells and in transfected Xenopus laevis oocytes expressing the bovine NAT (bNAT). Incubation (1-3 h) of adrenal medullary cells with ketamine (10-300 microM) caused an increase in appearance of catecholamines in culture medium. Ketamine (10-1000 microM) inhibited desipramine-sensitive uptake of [3H]noradrenaline (NA) (IC50=97 microM). Saturation analysis showed that ketamine reduced Vmax of [3H]NA uptake without changing Km, indicating a non-competitive inhibition. Other inhibitors of NAT, namely cocaine and desipramine, showed a competitive inhibition of [3H]NA uptake while a derivative of ketamine, phencyclidine, showed a mixed type of inhibition. Ketamine (10-1000 microM) also inhibited the specific binding of [3H]desipramine to plasma membranes isolated from bovine adrenal medulla. Scatchard analysis of [3H]desipramine binding revealed that ketamine increased Kd without altering Bmax, indicating a competitive inhibition. In transfected Xenopus oocytes expressing the bNAT, ketamine attenuated [3H]NA uptake with a kinetic characteristic similar to that of cultured adrenal medullary cells. These findings are compatible with the idea that ketamine non-competitively inhibits the transport of NA by interacting with a site which partly overlaps the desipramine binding site on the NAT.

Up-regulation of noradrenaline transporter in response to prolonged exposure to ketamine

“…In particular, sympathomimetic effects of ketamine have been shown to be due to inhibition of the noradrenaline (NA) transporter system. A number of investigators have reported that ketamine suppresses [ 3 H]NA uptake in various sympathetic nervous tissues (Taube et al 1975;Azzaro and Smith 1977;Garty et al 1990;Graf et al 1995) and the adrenal medulla (Hara et al 1998). All previous reports described acute effects of ketamine on noradrenaline transporter (NAT) activity.…”

“…We have recently reported that ketamine directly interacts with NAT at a site partly overlapping the antidepressant binding site and acutely inhibits its functional activity in bovine adrenal medullary cells (Hara et al 1998). In the present study, we examined the effects of prolonged exposure to ketamine on the functional activity, number, and mRNA of NAT in cultured bovine adrenal medullary cells and demonstrate an up-regulation of NAT in the cells induced by ketamine.…”

“…The pharmacological properties of NAT in bovine adrenal medullary cells are similar to those of the NAT in central and peripheral noradrenergic neurons . Therefore, the NAT in bovine adrenal medullary cells has provided a convenient model system for studying the effects of various agents such as cytokines, anaesthetics or antipsychotic drugs on this transporter (Hara et al 1998;Toyohira et al 1998;Yoshimura et al 2000).…”

Pentazocine Inhibits Norepinephrine Transporter Function by Reducing its Surface Expression in Bovine Adrenal Medullary Cells

“…The pharmacological properties of NET in bovine adrenal medullary cells are similar to those of NET in central and peripheral noradrenergic neurons (13). Therefore, NET in bovine adrenal medullary cells has provided a convenient model for studying the effects of various agents such as anesthetics and antipsychotic drugs on this transporter (19,20). Some centrally acting analgesic agents such as tramadol have both opioid and monoamine modes of action (21,22).…”

Influence of Ketamine on Catecholamine Secretion in the Perfused Rat Adrenal Medulla

“…The increase in systolic and diastolic pressure in animals, as well as in man, is mainly due to enhanced cardiac output (Domino et al, 1965;Virtue et al, 1967;Schwartz & Horwitz, 1975). Moreover, A number of investigators have reported that ketamine suppresses [ 3 H]NA uptake in various sympathetic nervous tissues (Taube et al, 1975;Azzaro & Smith, 1977;Garty et al, 1990;Graf et al, 1995) and the adrenal medulla (Hara et al, 1998;Hara et al, 2002). Local administration of ketamine was also found to induce an increased norepinephrine (NE) levels in dialysate in anesthetized cats (Kitagawa et al, 2002).…”