Effects of route of administration of the muscarinic agonist slaframine on endocrine and metabolic responses in sheep

The effects of intramuscular (IM) and intravenous (IV) administration of saline (SAL) and slaframine (SLF; 150 μg/kg BW.75), a muscarinic agonist isolated from the fungus Rhizoctonia leguminicola, were investigated in four St. Croix yearling ewes (28 kg BW) fitted with jugular vein catheters in a 4 × 4 Latin Square design with a 2 × 2 factorial arrangement of treatments. The response criteria (and pre-dose means) were concentrations of plasma glucose (GLUC; 4.3 mM), nonesterified fatty acids (NEFA; .21 mM), insulin (INS; 17.8 μU/ml), and somatotropin (GH; 3.5 ng/ml) in samples collected from 0 to 360 min; treatment was administered following the 60 min sample. Sheep administered SAL IM or IV showed no changes (P\u3e. 10) in plasma metabolites or hormones. Compared with SAL administration, SLF resulted in increases in plasma GLUC (P\u3c.02), NEFA (P\u3c.03), INS (P\u3c.04), and GH (P\u3c.006), and the responses were more pronounced for IV than for IM administration (P\u3c.02). Plasma GH peaked 20 min earlier in IV vs IM SLF. In sheep, consideration should be given to the route of SLF administration since it influences the response of plasma metabolites and hormones