Supranodose vagotomy eliminates anandamide-evoked cardiorespiratory depression in anaesthetized rats

Respiratory effects of an intravenous injection of anandamide were investigated in 19 urethane-chloralose anaesthetised and spontaneously breathing rats. In 10 neurally intact rats the effects of anandamide were checked to establish appropriate dose of the drug. In the second group, nine rats were challenged with anandamide while intact, following bilateral midcervical vagotomy and after subsequent supranodose vagotomy.Bolus injection of 1 mg kg−1 of anandamide into the right femoral vein pre- and post-midcervical vagotomy induced in all nine rats prompt apnoea of similar duration: 2.97 ± 0.5 and 3.2 ± 0.4 s, respectively. In post-apnoeic breaths tidal volume decreased below the control level by 25% (P < 0.01) prior to and by 43.4% (P < 0.001) after midcervical vagotomy.Supranodose vagotomy precluded the respiratory response to anandamide. Anandamide-induced decrease in mean arterial blood pressure in nerve-intact and vagotomised rats was abolished by supranodose vagotomy.Results indicate that the cardio-respiratory depression evoked by anandamide administered via the peripheral circulation requires intact supranodose vagi.