ABSTRACT
Objective To perform a comparative study on membrane electrical properties of visceral and somatic nociceptive neurons of anterior cin?gulate gyrus(ACG)in cats,so as to provide the experimental basis for elucidating the mechanism of differences in perceptual qualities between vis?ceral pain and somatic pain from the membrane electrical aspects. Methods A total of 77 adult cats,female or male,weighting 2.0 to 3.5 kg were selected for the study. According to the properties of the greater splanchnic nerve(GSN)or saphenous nerve(SN)evoked responses of neurons in ACG and effect of morphine on the evoked responses,visceral nociceptive neurons(VNNs)having the long latency(≥50 ms)GSN evoked re?sponses or somatic nociceptive neurons(SNNs)having the long latency(≥50 ms)SN evoked responses were detected. With a glass microelectrode in vivo,a series of polarizing current of different intensity from-5 nA to+5 nA with a 50 ms duration were injected to these neurons in ACG,and the membrane electrical responses of these neurons were recorded. Finally,the membrane electrical parameters of these neurons were calculated. Re?sults Totally 254 VNNs and 172 SNNs were recorded in ACG. GSN evoked response threshold of VNNs were higher than SN evoked response threshold of SNNs. Compared with SNNs,the membrane resistance,the membrane capacity and the time constant of VNNs were larger. Conclusion Our data proved that there are some differences in the membrane electrical properties between VNNs and SNNs in ACG,which might be the mem?brane electrical basis for differences in perceptual qualities between visceral pain and somatic pain.
ABSTRACT
Objective To investigate the effects of GR82334 caudal veins injection(iv)or intrathecal injection(ith)on the increase of dopamine (DA)content in rats anterior cingulate gyrus(ACG)induced by heavy current stimulation of saphenous nerve(SN). Methods Totally 42 male Wi-star rats were randomly divided into six groups,including control group,sham stimulation group,SN stimulation group,GR82334(ith)group,NS (ith)group,GR82334(iv)group,and NS(iv)group. At the end of the study,rats of different groups were sacrificed,then the right side ACG were collected and weighted. ACG samples were then homogenized with 0.1 mol/L perchloric acid solution. After spinning at 10 000 r/min(4℃)for 20 min,20μL of the supernatant were harvest from each sample. High performance liquid chromatography electrochemical detection was used to mea-sure DA content. Results Heavy current stimulation of SN caused obvious increase of the DA content in ACG. GR82334(iv or ith)antagonized the significant increase of DA content in ACG induced by the stimulating SN. However,GR82334(ith)did not completely antagonized the increase of DA content in ACG induced by electric stimulating SN. Conclusion The results indicated that there is connection between SN and the dopami-nergic nervous system in ACG,and SN afferent nociceptive signals can activate ACG dopaminergic neurons to release DA. Peripheral and central NK-1 receptors are involved in the process of significant increase of DA content in ACG induced by SN afferent signals. However,there are other central paths of SN information input to ACG to induce obvious increases of DA content,in which other neurotransmitters and receptors may be involved.