ABSTRACT
The aim of the present study is to explore the role of anterior cingulate gyrus (ACG) in bilateral cerebral cortex in visceral nociceptive sensation. Electrical stimulation of greater splanchnic nerve (GSN) was used as visceral nociceptive stimulus, and intracellular recording techniques in vivo was used to record and analyze the responses to stimuli and spontaneous electric activities of the neurons in the bilateral ACG. According to the responses to electrical stimulation of GSN, the neurons in the bilateral ACG were divided into GSN-stimulus-relative neurons (GSRNs) and GSN-stimulus-irrelative ones. According to the characteristics of the evoked responses to electrical stimulation of the GSN, GSRNs could be further classified into visceral nociceptive neurons (VNNs) and non-visceral nociceptive neurons (NVNNs). VNNs included specific visceral nociceptive neurons (SVNNs) and non-specific visceral nociceptive neurons (NSVNNs). The results showed that the percentage of GSRNs in the contralateral ACG (38.18%) was significantly higher than that in the ipsilateral ACG (29.49%, P<0.01), suggesting although GSN afferent fibers project to bilateral ACG, they mainly project to the contralateral ACG. Compared with ipsilateral ACG, contralateral ACG possessed lower proportion of SVNNs and higher proportion of NSVNNs (P<0.01). The absolute values of resting potentials (RP) of GSRNs, VNNs, NVNNs and SVNNs in ipsilateral ACG were less than those of corresponding neurons in contralateral ACG. However, there were no significant differences in the absolute values of RP of NSVNNs between ipsilateral and contralateral ACG. There were no significant differences in modes, frequencies and amplitudes of spontaneous electric activities of VNNs and NVNNs between ipsilateral and contralateral ACG. Additionally, the percentage of neurons having spontaneous electric activities from VNNs was significantly higher than that from NVNNs, which indicated that the excitability of VNNs was higher than that of the NVNNs in bilateral ACG. These results suggest that the patterns and degrees of the responses to nociceptive GSN-stimulation of the ipsilateral and contralateral ACG are different, thus providing new experimental data for the asymmetry of functions of the bilateral brain.
Subject(s)
Animals , Cats , Female , Male , Electric Stimulation , Evoked Potentials , Physiology , Gyrus Cinguli , Physiology , Nociceptors , Physiology , Viscera , Visceral PainABSTRACT
<p><b>AIM</b>To explore the cerebral cortex mechanism of visceral nociceptive sensation and its characteristics on the cell level, we investigated the membrane electrical properties of 176 stimulus-relative neurons of greater splanchnic nerve (GSN) in anterior cingulate gyrus (ACG) of 20 adult healthy cats.</p><p><b>METHODS</b>We used intracellular recording techniques of glass microelectrode and injected polarizing current into the neurons in ACG.</p><p><b>RESULTS</b>Among 176 neurons, 148 were visceral nociceptive neurons (VNNs) and 28 non-visceral nociceptive neurons (NVNNs). The membrane resistance (Rm), time constant (tau), membrane capacity (Cm), and the I-V curve of both VNNs and NVNNs in ACG were significantly different. The discharge frequency and amplitude of both VNNs and NVNNs produced by injecting depolarized current were different, too.</p><p><b>CONCLUSION</b>The results suggest that structure of cell membrane, volume of the soma, and other aspects of morphology between VNNs and NVNNs in ACG may have significant differences. The results also might provide progressively experimental evidence for specific theory of pain sensation.</p>