Abstract
Plasma concentrations of neuropeptide Y were determined by means of a specific radioimmunoassay in the conscious calf. Significantly higher concentrations were found in the adrenal venous effluent (102 +/- 34 pmol/l) compared to systemic arterial plasma (11 +/- 7 pmol/l). Stimulation of the splanchnic nerves at 40 Hz in bursts for 1 s at 10 s intervals resulted in a slow sustained rise in plasma neuropeptide Y in both adrenal (peak 1124 +/- 217 pmol/l and peripheral (peak 771 +/- 182 pmol/l) samples. Experiments performed in adrenalectomized calves produced a closely similar release of neuropeptide Y when the nerves were stimulated intermittently in the same pattern and under the same conditions. Stimulation of the splanchnic nerves at 4 Hz continuously resulted in a smaller response. Pre-treatment with hexamethonium completely abolished the rise in plasma neuropeptide Y concentrations.