Figure 5.

Dose-response curves and time course of nociceptive responses to mechanical and heat stimuli after a single systemic treatment with nociceptin. A, B: Comparisons of the number of responses to mechanical stimulation on the abdomen skin 1 h after treatment with nociceptin (ip) for control and alcohol and high fat (AHF) fed rats. Dose-dependent responses were reduced to (A) low intensity (1 g) and (B) high intensity (6 g) mechanical stimulation of the abdomen; C: Nociceptin increased hindpaw mechanical withdrawal threshold in AHF fed rats; D: Hotplate response latencies of AHF fed animals improved with the highest dose of nociception. In control animals nociceptin did not alter mechanical and heat sensitivity. Vehicle treatments had no effect on mechanical or heat sensitivity of animals from either group; E-H: Mechanical and heat responses in animals treated with either a single systemic injection of nociceptin (200 nmol/kg in saline) or with the saline vehicle; E: Abdominal withdrawals in response to low intensity (1 g) mechanical stimulation decreased to control levels at the 1 and 4 h post injection timepoints of AHF fed rats. Mechanical hypersensivity of vehicle treated AHF diet fed rats did not improve; F: Responses of AHF fed rats to high intensity (6 g) abdominal mechanical stimulation were decreased to control values only 1 h after injection of nociception; G: Hindpaws mechanical withdrawal thresholds of AHF fed rats recovered to control values for up to 4 h post injection; H: Hotplate response latencies of AHF fed rats improved only at the 1 h time point after nociceptin treatment. ^aP < 0.05, AHF vs control.