Mobilization of glucoregulatory hormones and glucose by hypothalamic locomotor centers

Recent studies suggest that, in addition to classical humoral metabolic feedback mechanisms, the mobilization of glucoregulatory hormones and glucose in exercise may be regulated by motor centers in the brain. We, therefore, studied the effect of electrically stimulating the posterior hypothalamic locomotor region (PHLR) for 10 min in decorticated (n = 6) and α-chloralose-anesthetized (n = 8) cats. Blood pressure and heart rate were measured, and blood samples were drawn for analysis of hormones and metabolites before, during, and after 10 min of PHLR stimulation. Feedback from contracting muscles were prevented by neuromuscular blockade in decorticated cats and by the anesthesia in anesthetized cats. In decorticated cats, PHLR stimulation elicited increases (2 P < 0.05) in glucose production (Δ54 ± 16 μmol·min^-1·kg^-1), plasma glucose (Δ2.2 ± 0.7 mmol/l), epinephrine (Δ4.9 ± 1.8 pmol/l), norepinephrine (Δ2.2 ± 0.9 pmol/l), glucagon (Δ16 ± 5 pmol/l), decreased (2 P < 0.05) in plasma insulin (Δ27 ± 7 pmol/l), and increases (2 P < 0.05) in blood pressure (Δ48 ± 9 mmHg) and heart rate (Δ26 ± 7 beats/min). In anesthetized cats, PHLR stimulation elicited increases (2 P < 0.05) in glucose production (Δ12 ± 4 μmol·min^-1·kg^-1), plasma glucose (Δ0.4 ± 0.1 mmol/l), blood pressure (Δ39 ± 7 mmHg), and heart rate (Δ28 ± 7 beats/min), whereas changes in catecholamine and insulin concentrations did not reach statistical significance. These results provide the first direct evidence for the view that hormonal and metabolic, as well as cardiovascular, exercise responses may be evoked in parallel with locomotion by activation of motor centers in the brain.