Rescue of dopamine transporter function in hypoinsulinemic rats by a D2 receptor-ERK-dependent mechanism

J Neurosci. 2012 Feb 22;32(8):2637-47. doi: 10.1523/JNEUROSCI.3759-11.2012.

Abstract

The dopamine (DA) transporter (DAT) is a major target for abused drugs and a key regulator of extracellular DA. A rapidly growing literature implicates insulin as an important regulator of DAT function. We showed previously that amphetamine (AMPH)-evoked DA release is markedly impaired in rats depleted of insulin with the diabetogenic agent streptozotocin (STZ). Similarly, functional magnetic resonance imaging experiments revealed that the blood oxygenation level-dependent signal following acute AMPH administration in STZ-treated rats is reduced. Here, we report that these deficits are restored by repeated, systemic administration of AMPH (1.78 mg/kg, every other day for 8 d). AMPH stimulates DA D(2) receptors indirectly by increasing extracellular DA. Supporting a role for D(2) receptors in mediating this "rescue," the effect was completely blocked by pre-treatment of STZ-treated rats with the D(2) receptor antagonist raclopride before systemic AMPH. D(2) receptors regulate DAT cell surface expression through ERK1/2 signaling. In ex vivo striatal preparations, repeated AMPH injections increased immunoreactivity of phosphorylated ERK1/2 (p-ERK1/2) in STZ-treated but not control rats. These data suggest that repeated exposure to AMPH can rescue, by activating D(2) receptors and p-ERK signaling, deficits in DAT function that result from hypoinsulinemia. Our data confirm the idea that disorders influencing insulin levels and/or signaling, such as diabetes and anorexia, can degrade DAT function and that insulin-independent pathways are present that may be exploited as potential therapeutic targets to restore normal DAT function.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Amphetamine / therapeutic use
  • Analysis of Variance
  • Animals
  • Blood Glucose / drug effects
  • Body Weight / drug effects
  • Brain / blood supply
  • Brain / drug effects
  • Brain Mapping
  • Corpus Striatum / blood supply
  • Corpus Striatum / drug effects*
  • Diabetes Mellitus, Experimental / drug therapy*
  • Diabetes Mellitus, Experimental / pathology*
  • Dopamine / metabolism
  • Dopamine Agents / therapeutic use
  • Dopamine Plasma Membrane Transport Proteins / metabolism*
  • Drug Administration Schedule
  • Drug Interactions
  • Enzyme Inhibitors / pharmacology
  • Hypoglycemic Agents / pharmacology
  • Image Processing, Computer-Assisted
  • Insulin / pharmacology
  • MAP Kinase Signaling System / drug effects
  • MAP Kinase Signaling System / physiology*
  • Magnetic Resonance Imaging
  • Male
  • Oxygen / blood
  • Raclopride / pharmacology
  • Rats
  • Rats, Sprague-Dawley
  • Receptors, Dopamine D2 / metabolism*

Substances

  • Blood Glucose
  • Dopamine Agents
  • Dopamine Plasma Membrane Transport Proteins
  • Enzyme Inhibitors
  • Hypoglycemic Agents
  • Insulin
  • Receptors, Dopamine D2
  • Raclopride
  • Amphetamine
  • Oxygen
  • Dopamine