Cholinergic and adrenergic influences upon cat skeletal muscle performance induced by stimulation of the anterior hypothalamus.

The influence exerted by stimulation of the anterior hypothalamus (zone of cholinergic vasodilatation) on the performance of triceps surae during tetanic contraction has been investigated. Hypothalamic stimulation, if combined with indirect muscle stimulation, improves muscle performance, i.e. slows down the rate of decrease of contraction. The effect is abolished by atropine (0.5 mg/kg) and insensitive to propanolol (0.1 mg/kg). The cholinergic influence is only effective if hypothalamic stimulation coincides with the beginning of motor nerve stimulation. In some of our experiments stimulation of the same central structures elicited another influence on muscle performance, associated with the release of adrenaline into the blood. In this case, contrary to the cholinergic influence, the force of contraction increases only when hypothalamic stimulation does not start earlier than 100 s after the initiation of contraction (phase of slow decline of tension). The effect is insensitive to atropine (0.1 mg/kg) and abolished by propanolol (0.1 mg/kg).