CR and drug abuse

[Guest guest]

Hi All,

We have little drug abuse among us, but the below seems

of interest in this area.

The definition of amphetamine is:

" Drug of abuse that acts by increasing extraneuronal dopamine

in midbrain. Thought to displace dopamine in synaptic vesicles,

leading to increased synaptic levels. "

" Leptin, a circulating hormone secreted from adipocytes, is an

index of adiposity and is reduced by caloric restriction and

weight loss. " http://tinyurl.com/532r9

Yet the pdf not available below states:

" Lateral ventricular infusion of leptin, using a regimen that

decreases

food intake and body weight in ad libitum fed rats (12 mug/day), had

no effect

on the locomotor response to d-amphetamine in food-restricted rats

that were

maintained at 80% of prerestriction body weight. "

Can this be correct?

Physiol Behav. 2004 Dec 15;83(3):377-81.

Effects of chronic ICV leptin infusion on motor-activating

effects of

d-amphetamine in food-restricted and ad libitum fed rats.

Hao J, Cabeza de Vaca S, Carr KD.

... endocrine adiposity

hormones, such as leptin, may regulate appetitively motivated

behavior by

modulating brain dopamine function. By extension, it has been

hypothesized that

the increased behavioral sensitivity of food-restricted, underweight

rats to

psychostimulant challenge may be triggered by the accompanying

hypoleptinemia.

The purpose of the present study was to determine whether two weeks of

continuous intracerebroventricular (ICV) infusion of leptin alters the

motor-activating effect of d-amphetamine (0.75 mg/kg, IP) in food-

restricted

rats. Lateral ventricular infusion of leptin, using a regimen that

decreases

food intake and body weight in ad libitum fed rats (12 mug/day), had

no effect

on the locomotor response to d-amphetamine in food-restricted rats

that were

maintained at 80% of prerestriction body weight. This result may

indicate that

hypoleptinemia is not involved in the induction/maintenance of

neuroadaptations

that mediate enhanced behavioral sensitivity to psychostimulant

challenge.

Interestingly, ad libitum fed rats treated with leptin displayed an

increased

locomotor response to d-amphetamine that was most prominent 3-5 days

after

termination of the infusion. Body weights and d-amphetamine

sensitivity of these

subjects returned to control values by 8-10 days postinfusion. The

enhanced

behavioral sensitivity to d-amphetamine in leptin-treated ad libitum

fed rats

may be a by-product of adipose depletion and, if so, would further

support

involvement of a peripheral signal other than hypoleptinemia in the

modulation

of central sensitivity to psychostimulant challenge.

PMID: 15581659 [PubMed - in process]

Cheers, Alan Pater