Effects of acupuncture at Sibai(ST 2) acupoint on neuronal discharge in rat nucleus tractus solitarius

BACKGROUND： Electrophysiology can prove the integration of afferent information from the stomach meridian of Foot-Yangming in the nucleus tractus solitarius （NTS） and objectively describe the specific association between meridian vessels and Zang Fu organs. OBJECTIVE： To investigate the effects of afferent information from acupuncture at Sibai （ST 2） acupoint on neuronal discharge in rat NTS. DESIGN, TIME AND SETFING： A randomized, controlled, animal experiment was performed at the Key Laboratory of Meridian-Vessels and Zang Fu Organs, Traditional Chinese Medicine University of Hunan, State Administration of Traditional Chinese Medicine, and Key Laboratory of Acupuncture, Moxibustion, and the Biological Information of Hunan Higher Education Institutes, between December 2005 and October 2008. MATERIALS： A total of 52 Sprague Dawley rats, of either gender, aged 4 months, were included in this study. Acupuncture needles of 0.32 mm （diameter） x 40 mm （length） were used. METHODS： An extracellular recording protocol was applied. The Sibai （ST 2） acupoint in the stomach meridian of Foot-Yangming was used as an acupuncture point （acupoint）. Simultaneously, Dicang （ST 4） and Neiting （ST 44） acupoints in the stomach meridian of Foot-Yangming, Quanliao （S118） acupoint in the small intestine meridian of Hand-Taiyang, and a non-acupoint lateral to Sibai （ST 2） acupoint, were selected as controls. The Sibai （ST 2） acupoint was stimulated for 30 seconds by hand acupuncture through twirling and rotating, to determine the neurons responding to body surface stimulation in the NTS. MAIN OUTCOME MEASURES： Frequency of responding NTS neurons after acupuncture at four acupoints including Sibai （ST 2）, Dicang （ST 4）, Neiting （ST 44） and Quanliao （SI 18） and one non-acupoint. RESULTS： The frequency of responding NTS neurons was significantly higher after acupuncture at Sibaithan at control sites including the Dicang （ST 4）, Neiting （ST 44） and Quanliao （S118） acupoints and at the non-acupoint （P 〈 0.01）. The frequency of responding NTS neurons at Dicang （ST 4） and Quanliao （SI 18） was significantly higher than at Quanliao （SI 18） and the non-acupoint （P 〈 0.05）. The rate of frequency change of responding NTS neurons for the Sibai （ST 2）, Dicang （ST 4）, Neiting （ST 44）, and Quanliao （S118） acupoints as well as the non-acupoint was （35.08±4.80） %, （28.25± 5.46） %, （27.57± 4.87） %, （20.02 ±4.23） %, and （18.55 ±2.49） % respectively. Simultaneously, significant differences existed between Sibai （ST 2） and the other acupoints （P 〈 0.05 or P〈 0.01）. CONCLUSION： Compared with the Dicang （ST 4） and Neiting （ST 44） acupoints in the stomach meridian of Foot-Yangming, Quanliao （SI 18） acupoint in the small intestine meridian of Hand-Taiyang, and the non-acupoint lateral to Sibai （ST 2） acupoint, the Sibai （ST 2） acupoint in the stomach meridian of Foot- Yangming is more closely related to the NTS. In the stomach meridian of Foot- Yangming, afferent information is different in distant and near Shu acupoints, indicating that each Shu acupoint has its own specificity.

Activation of hypothalamic gono-like neurons in female rats during estrus

In mammals, gonadal function is controlled by the activity of hypothalamic gonadotropin-releasing hormone neurons, which control the secretion of adenohypophyseal and gonadal hormones. However, there are a number of unanswered questions in relation to gonadal function. It is currently unknown how erotogenic stimulation of the genitals influences the subpopulation of hypothalamic medial preoptic area neurons, antidromically identified as projecting to the median eminence at different periods of the estrous cycle. Additionally, the distinctiveness of hypothalamic medial preoptic area neurons, with respect to methods of feedback control by exogenous hormones, is also unknown. In this study, spontaneous discharges from individual neurons encountered within the medial preoptic area, gono-like neurons, were recorded extracellularly using glass microelectrodes. To confirm the cellular and histochemical properties of the recording units, antidromic stimulation was performed using a side-by-side bipolar stimulating electrode placed into the median eminence, alongside microiontophoretic injections of the conventional tracer, horseradish peroxidase. In addition, further immunohistochemical analyses were performed. Results showed that elevated gono-neuron activity was accompanied by increased background activity and greater responses to erotogenic stimuli during estrus. Application of clitoral traction stimulation resulted in increased activation of the gono-like neurons. This neuronal activity was noticeably inhibited by β-estradiol administration. Immunohistochemical analyses revealed the presence of gonadotropin-releasing hormone-reactive protein in hypothalamic cells in which electrophysiological recordings were taken. Thus, medial preoptic area neurons represent the subset of hypothalamic gonadotropin-releasing hormone neurons described from brain slices in vitro, and might serve as a useful physiological model to form the basis of future in vivo studies.

Local neuronal circuits that may shape the discharge patterns of inferior collicular neurons

The discharge patterns of neurons in auditory centers encode information about sounds.However,few studies have focused on the synaptic mechanisms underlying the shaping of discharge patterns using intracellular recording techniques.Here,we investigated the discharge patterns of inferior collicular（IC）neurons using intracellular recordings to further elucidate the mechanisms underlying the shaping of discharge patterns.Under in vivo intracellular recording conditions,recordings were obtained from 66 IC neurons in 18 healthy adult mice（Mus musculus,Km）under free field-stimulation.Fiftyeight of these neurons fired bursts of action potentials（APs）to auditory stimuli and the remaining eight just generated local responses such as excitatory（n=4）or inhibitory（n=4）postsynaptic potentials.Based on the APs and subthreshold responses,the discharge patterns were classified into seven types：phasic（24/58,41.4%）,phasic burst（8/58,13.8%）,pauser（4/58,6.9%）,phasic-pauser（1/58,1.7%）,chopper（2/58,3.4%）,primary-like tonic（14/58,24.1%）and sound-induced inhibitory（5/58,8.6%）.We concluded that（1）IC neurons exhibit at least seven distinct discharge patterns;（2）inhibition participates in shaping the discharge pattern of most IC neurons and plays a role in sculpting the pattern,except for the primary-like tonic pattern which was not shapedby inhibition;and（3）local neural circuits are the likely structural basis that shapes the discharge patterns of IC neurons and can be formed either in the IC or in lower-level auditory structures.