The effects of 7-OH-DPAT, quinpirole and raclopride on licking for sucrose solutions in the non-deprived rat

Abstract

Pharmacological manipulations that alter dopamine (DA) at DA receptor subtypes produce reductions in feeding behaviour. What remains uncertain is the exact way in which these reductions in feeding are achieved as a consequence of differing drug actions at separate receptor subtypes. In this study our aim was to compare the anorectic effects of the preferential D3/D2 agonists 7-hydroxy-2-(di-n-propylamino)tetralin (7-OH-DPAT) and quinpirole and the non-selective D2/D3 antagonist raclopride on the microstructure of licking responses in non-deprived rats. In a 20-min test, trained adult, male hooded rats had access to one of three solutions: 1%, 3% or 10% sucrose. 7-OH-DPAT (0.1-1.0 mg/kg, i.p.), quinpirole (0.03-0.3 mg/kg, s.c.), raclopride (0.03-0.3 mg/kg, i.p.) or vehicle were injected 20 min prior to the start of the licking test. A lickometer recorded the timing of each lick, from which the microstructural parameters of bout frequency and bout duration were also computed. All compounds reduced the mean bout duration, while 7-OH-DPAT and raclopride also brought about a compensatory increase in bout number. Analysis of the licking rates over the test session showed that 7-OH-DPAT, quinpirole and raclopride decreased the initial rate, without affecting the rate of decline of licking. Changes in licking microstructure (i.e. initial rate of licking and mean bout duration) after the administration of 7-OH-DPAT, quinpirole and raclopride, are consistent with an action of these dopaminergic compounds to reduce palatability.

Involvement of Endogenous Enkephalins and β-Endorphin in Feeding and Diet-Induced Obesity

“…Nevertheless, licking bout length has been considered more immediately sensitive to hedonic impact, whereas the number of licking bouts across a session is generally considered to reflect motivation based on a long-run average of previous experience weighted only slightly toward recent events (D'Aquila, 2010; Davis and Smith, 1988;Frisina and Sclafani, 2002;Higgs and Cooper, 1998). However, some caution in this interpretation is called for in light of reports that dopaminergic antagonist effects on licking microstructure include decreases in bout duration (D'Aquila, 2010;Galistu et al, 2011;Genn et al, 2003;Liao and Ko, 1995;Schneider et al, 1990;Smith, 2004; for review see Dwyer, 2012), despite evidence that the mesolimbic dopamine system is a key mediator of motivated but not hedonic behavior (for review see Berridge and Robinson, 1998). Such effects on bout length have been interpreted in motivational terms, arguing that dopamine plays a role in the use of hedonic experience to extend motivation for consumption of palatable stimuli (D'Aquila, 2010).…”

Clozapine increases reward evaluation but not overall ingestive behaviour in rats licking for sucrose

“…In contrast, the number of bouts is sensitive to stimuli other than the direct contact with the reward, such as post-ingestive cues, and might represent a measure of behavioural activation or motivation (D'Aquila 2010; Higgs and Cooper 1998;Schneider et al 1990). In rats licking for a sucrose solution, dopamine D1-receptor antagonism reduces the bout number without affecting mean bout size (D'Aquila 2010; Liao and Ko 1995), while dopamine D2-like receptor antagonism produces on the within-session bout number time course, an effect resembling extinction in paradigms of instrumental responding for a reward (D'Aquila 2010), and reduces bout size (D'Aquila 2010; Genn et al 2003;Liao and Ko 1995;Schneider et al 1990), mimicking the effect of sucrose dilution (Schneider et al 1990). Consistent results were obtained studying the ingestion of NaCl solutions (Canu et al 2010).…”

“…This information might be of relevance for several reasons. Indeed, the relationship between taste, post-ingestive cues and the licking microstructural measures (Davis and Smith 1992;Geary and Smith 1985;Sclafani and Ackroff 2004;Sclafani and Nissenbaum 1987;Smith 2001Smith , 2004, as well as the sensitivity of these measures to treatment with antipsychotic drugs and dopamine antagonists (D'Aquila 2010; Genn et al 2003;Liao and Ko 1995;Schneider et al 1990), have been particularly well characterised when sucrose was used as a tastant. Moreover, sucrose was used as a reward in previous studies showing the ability of clozapine to increase reward efficacy in a progressive-ratio reinforcement schedule (Mobini et al 2000;Zhang et al 2005).…”

A low-cost solution to measure mouse licking in an electrophysiological setup with a standard analog-to-digital converter

“…Monitoring licking activity is also a very useful method for rating the dose-related behavioral effects of acute or chronic drug treatment (e.g. Genn et al, 2003;Hsiao and Spencer, 1983;Peachey et al, 1976).…”