We investigated the effects of a total extract from Zanthoxylum piperitum f
ruit, of the volatile components of extract, and of a non-volatile fraction
containing the major alkylamides of Zanthoxylum (NVA) on food intake in ra
ts. In Experiment 1, three groups (A, B, C) of mildly food deprived rats we
re given one hour long feeding trials during which they were offered choice
s between an oat-bran wafer paired with vegetable oil and a wafer paired wi
th a Zanthoxylum preparation in vegetable oil. Trials were divided into thr
ee blocks of two tests each. During Blocks 1 and 3, two wafers coated with
vegetable oil were offered to establish baseline consumption. During Block
2, Group A was given choices between wafers coated with oil and wafers coat
ed with total extract. Group B was offered oil coated wafers and wafers coa
ted with the NVA fraction. Group C received two oil coated wafers. One was
served on top of a screened dish containing a sample of total extract. In t
his manner, the rats were exposed to volatile compounds emanating from the
extract but could not contact the extract. The second wafer was served on t
op of a screened sample of oil. Results: In Blocks 1 and 3 trials, the rats
fed indiscriminately from both wafers. During Block 2, total extract, the
NVA fraction and the volatile compounds from extract all significantly redu
ced food consumption. In Experiment 2, habituation to the NVA fraction and
to the volatile constituents of extract was examined in two additional grou
ps (D, E), using the methods described above. Baseline consumption was test
ed in Blocks 1 and 3 by offering two oil coated wafers. During Block 2, gro
up D was given 10 trials with oil coated and NVA-fraction coated wafers. Gr
oup E was given 10 trials with oil coated wafers paired with the volatile c
onstituents of total extract and with those of oil. Results: Both groups fa
iled to habituate to the Zanthoxylum stimuli. Wafers treated with the NVA f
raction and wafers paired with the volatile constituents of extract were av
oided throughout the 10 test days.