Experimental model
 
 
- Male Wistar rats, 300-320 g, free moving and unstressed, were equipped  with an intraoral cannula and trained,
- Rats were trained until intraoral intake with sucrose was stable (about two weeks).
- Rats were tested after fasting and with lights off.
- Intraoral intake of sucrose was measured  30 min and 120 min after i.p. infusion of different solutions.