The effects of dose and repeated administration on the longer-term hypophagia produced by amphetamine in rats

Abstract

Rats are hypophagic approximately 1 to 3 and 13-27 hours after receiving amphetamine (2.0 mg/kg). This study examined how these short- and longer-term phases of hypophagia were affected by repeated administration of different amphetamine doses. Throughout eight five-day tests, rats could lever press for food pellets for one-hour periods beginning every three hours. On test day 1, rats were treated with saline, and on test day 3, they were treated with a dose of amphetamine. Across tests, for one group treatment on day 3 alternated between 0.0 (saline) and 0.5 mg/kg amphetamine; for a second group treatment on day 3 alternated between 1.0 and 2.0 mg/kg amphetamine; and for a third group, treatment on day 3 was always 1.0 mg/kg amphetamine. Patterns of food intake following day 1 saline and day 3 treatment were compared. Short-term food intake was abolished by 0.5, 1.0, and 2.0 mg/kg amphetamine, and no tolerance was observed to this effect. Longer-term hypophagia was produced by 1.0 and 2.0 but not by 0.5 mg/kg. Tolerance to longer-term hypophagia was seen when 1.0 mg/kg alone was used as the day 3 treatment, but not when 1.0 and 2.0 mg/kg were alternated across tests as the day 3 treatment. Short- and longer-term hypophagia were dissociated by threshold doses for elicitation and by differential tolerance. Occasional receipt of a higher amphetamine dose may sometimes increase the longer-term hypophagia produced by a lower dose.

Acute withdrawal-related hypophagia elicited by amphetamine is attenuated by pretreatment with selective dopamine D1 or D2 receptor antagonists in rats

“…On average, Day 1 intake during a subsequent test was 99% of Day 1 intake during a prior test. In other words, at the start of successive tests, intake was comparable: Recovery periods appeared to be long enough for intake to normalize from one test to the next (for discussions of within-test stability see White et al, 2010; White et al, 2007). …”

“…The first phase (short-term hypophagia) occurs during the first several hours after drug treatment and is one aspect of the psychomotor stimulant state. The second phase (longer-term hypophagia) tends to be most prominent between, roughly, hours 19 to 26 post-treatment (White et al, 2010; White et al, 2007). Other motivational and affective impairments are observed during the same time period (Barrett et al, 1992; White et al, 2004; White and White, 2006), and so longer-term hypophagia may be an aspect of an acute withdrawal or “hangover” syndrome.…”

“…The intervals are distinguished on the basis of the effects observed in prior studies following 2.0 mg/kg amphetamine (White et al, 2004; White et al, 2010; White et al, 2007; White and White, 2006). The short-term interval includes hours 1–6 post-treatment.…”

“…The present study employed a procedure that measured short- and longer-term effects (White et al, 2010; White et al, 2007). Throughout a series of five-day tests, rats could lever press for food pellets during one-hour intervals that began every 3 hours.…”

Involvement of adenosinergic and dopaminergic systems in the regulation of alcohol or sucrose intake: studies in rodent models of self-administration

“…A characteristic of the concurrent PR/free chow paradigm used in experiment 1 is that animals, independently of their level of responding, tend to eat high amounts of free chow since they are food deprived . Major psychostimulants such as amphetamine and cocaine can suppress appetite (Vee et al, 1983;Sanghvi et al, 1975;White et al, 2010). However, in our PR/free reward choice studies caffeine did not have a suppressant effect on food or fluid intake.…”