Influence of taste and food texture on the feeding responses induced by 8-OH-DPAT and gepirone

Abstract

Previously it has been shown that 5-hydroxy-tryptamine (5-HT)1A agonists such as 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) and gepirone increase food intake in free-feeding rats. These experiments were conducted to examine the possible influence of taste and textural factors on the feeding responses induced by these two drugs. Separate groups of non-water-deprived rats were given access to one of a variety of different solutions of saccharin (0.02, 0.04, 0.20 and 2.0% w/v) or water for 2 h each day. Rats were then treated with different doses of 8-OH-DPAT (10, 60 or 100 micrograms/kg) or gepirone (1 or 2.5 mg/kg) in a repeated measures design. Under saline injection an inverted-U shaped concentration-response curve was obtained, with the highest level of intake occurring in rats drinking from the 0.20% saccharin solution. The highest doses of 8-OH-DPAT and gepirone suppressed drinking of saccharin, particularly over the first 30 min of the test period, leading to a flattening of the concentration response curve. At 2 h post-injection 60 micrograms/kg 8-OH-DPAT enhanced the consumption of the 0.04% saccharin solution only. In a second experiment, 8-OH-DPAT or gepirone was administered to rats eating either standard pelleted chow or the same food presented in powdered form. Both drugs stimulated feeding. However, interactions with food type were found. At 60 and 100 micrograms/kg 8-OH-DPAT increased eating of both food types equally, but with 500 micrograms/kg rats are significantly more of the pelleted food.(ABSTRACT TRUNCATED AT 250 WORDS)