Somatic afferent regulation of plasma immunoreactive glucagon in anesthetized rats

Responses of dorsal spinal cord blood flow to innocuous cutaneous stimulation in anesthetized rats

In urethane-anesthetized, artificially-ventilated rats, alterations in dorsal spinal cord blood flow (SCBF) were measured with a laser Doppler flowmeter in response to innocuous mechanical cutaneous stimulation. SCBF recorded at the T12-L1 level increased with brushing of the ipsilateral, but not contralateral, upper back, lower back or proximal hindlimb. Brushing of the forepaw, proximal forelimb or hindpaw had no effect on T12-L1 SCBF. SCBF recorded at the L4-6 level increased with brushing of the ipsilateral, but not contralateral, proximal hindlimb and hindpaw. Brushing of the forepaw, proximal forelimb, upper back or lower back had no effect on SCBF at the L4-6 level. None of these brushing stimuli produced significant changes in systemic arterial blood pressure or heart rate. Pretreatment with phenoxybenzamine, an alpha adrenoceptor blocking agent, resulted in a small but statistically significant attenuation in the response of SCBF to brushing. However, pretreatment with propranolol, a beta adrenoceptor blocking agent, or atropine, a muscarinic cholinergic receptor blocking agent, produced no such effect. These results indicate that innocuous mechanical cutaneous input can produce a segmentally-organized increase in regional SCBF, which may be mediated in part, by alpha adrenergic receptors.

Massage-like stroking influences plasma levels of gastrointestinal hormones, including insulin, and increases weight gain in male rats

The aim of the present study was to investigate the effects of repeated massage-like stroking on plasma levels of some gastrointestinal hormones, insulin included, glucose and weight gain. For this purpose, male rats were exposed to stroking on the ventral side of the abdomen for 3 or 14 times. The treatments were given every second day. Control rats were picked up at the same time but received no stroking. Body weight was measured regularly. Rats were decapitated 10 min after the last treatment. Hormone levels were radioimmunoassayed and glucose was measured by spectrophotometry. In rats exposed to 3 sessions of massage-like stroking plasma levels of insulin (p<0.05) and somatostatin (p<0.01) were significantly decreased 10 min after the last treatment. After 14 treatments of massage-like stroking, decreased plasma levels of insulin (p<0.01) and gastrin (p<0.01) as well as increased glucose levels (p<0.01) were observed 10 min after the last treatment. In addition, weight gain was significantly increased (ANOVA p<0.0001) in rats exposed to 14 treatments. In conclusion, repeated massage-like stroking decreased plasma levels of gastrin, insulin and somatostatin, increased plasma levels of glucose and promoted weight gain. The effects were influenced by the number of treatments.

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.

Hepatic blood flow responses to mechanical stimulation of the skin in anaesthetised rats

The aim of the present study was to investigate how hepatic blood flow (HBF) changes in response to mechanical stimulation of different areas of the skin in anaesthetised rats, by focusing on involvement of the hepatic sympathetic nerves in and contribution of systemic circulatory changes to the HBF responses. HBF was measured at the surface of the left lateral lobe using the laser Doppler flowmetry. Both innocuous and noxious mechanical stimuli were applied to skin areas of the abdomen and hindlimb. Innocuous mechanical stimulation (brushing) of the abdomen and hindlimb did not significantly change HBF, while noxious mechanical stimulation (pinching) of the abdomen and hindlimb did. The responses to pinching were dependent on the sites stimulated. Pinching of the abdomen decreased, while pinching of the hindlimb increased the HBF. The decrease of HBF in response to abdominal pinching remained after the spinal cord was transected at T1-2 level, but the response was diminished after hepatic sympathetic nerves were severed. On the other hand, the increase of HBF in response to hindlimb pinching was dependent on the increase in blood pressure, and was not influenced by the severance of hepatic sympathetic nerves, and the responses to hindlimb pinching were almost absent after the spinal cord was transected. Based on these results, we suggest that noxious mechanical stimulation of the skin produces changes of HBF, either as a reflex response via activation of the hepatic sympathetic nerves or as a passive response to systemic circulatory changes, depending on the sites stimulated.