Responses of hepatic glucose output to noxious mechanical stimulation of the skin in anaesthetised rats.

Responses of hepatic glucose output (HGO) to noxious mechanical stimulation of different skin areas were investigated in anaesthetised rats with central nervous system intact or acutely spinalized at the thoracic 1-2 (T1-T2) level by focusing on the involvement of the sympathetic and parasympathetic nerves in the responses of HGO. We measured HGO with a microdialysis probe implanted into the left lateral lobe of the liver. Pinching was applied to bilateral skin areas of the abdomen and hindlimb for 10 min. Atropine was injected in order to block the action of the parasympathetic nerves, whereas phentolamine and propranolol were injected in order to block the action of the sympathetic nerves. The HGO started to increase immediately after the cessation of pinching of the abdomen and the hindlimb, and lasted for 30 min. The increase of HGO was observed during stimulus period in animals pretreated with atropine, and totally abolished in animals pretreated with phentolamine and propranolol. The responses of HGO to abdominal pinching, but not to hindlimb pinching, remained after spinal cord transection at the T1-T2 level. The present results suggest that HGO is regulated as a reflex response via both sympathetic and parasympathetic nerves by noxious mechanical stimulation of the skin. Furthermore, it was shown that relative contribution of the spinal and supraspinal organization to the somato-HGO responses was dependent on the skin areas stimulated.