Activating dopamine D2 receptors reduces brown adipose tissue thermogenesis induced by psychological stress and by activation of the lateral habenula

Emotional hyperthermia is the increase in body temperature that occurs as a response to an animal detecting a salient, survival-relevant stimulus. Brown adipose tissue (BAT) thermogenesis, controlled via its sympathetic innervation, contributes to this temperature increase. Here, we have used an intruder rat experimental model to determine whether quinpirole-mediated activation of dopamine D2 receptors attenuates emotional hyperthermia in conscious rats. In anesthetized rats, we determined whether systemic quinpirole reduces BAT nerve discharge induced by activation of the medullary raphé and the lateral habenula (LHb). We measured BAT and body temperature with chronically implanted thermistors in conscious, freely moving, individually housed, male rats (resident rats). Either vehicle or quinpirole was administered, intraperitoneally, to the resident rat 30 min before introduction of a caged intruder rat. Quinpirole, in a dose-dependent manner, reduced intruder-elicited increases in BAT and body temperature. Pre-treatment with the D2 antagonist spiperone, but not the selective D1 antagonist SCH-23390, prevented this quinpirole-elicited decrease. In anesthetized rats, quinpirole abolished BAT sympathetic nerve discharge elicited by bicuculline-mediated activation of the LHb, but not the medullary raphé. Thus, activation of dopamine D2 receptors reduces the BAT thermogenesis that contributes to emotional hyperthermia. We provide evidence that these dopamine D2 receptors are located in the thermogenic pathway between the LHb and the lower brainstem pre-sympathetic control centre in the medullary raphé.

Gentle Manual Acupuncture Could Better Regulate Gastric Motility and Vagal Afferent Nerve Discharge of Rats with Gastric Hypomotility

The variation of stimulus intensity of manual acupuncture (MA) may produce diverse acupuncture effects. However, the intensity-effect relationship and the underlying mechanism of MA are still elusive. In this study, the effects of MA regulation of gastric motility were investigated after lifting-thrusting MA treatment with four different frequencies (1 Hz, 2 Hz, 3 Hz, and 4 Hz) at ST36. The experiments were conducted on rats with gastric hypomotility caused by atropine. The results showed that the gastric motility amplitude decreased after atropine injection, while the treatment of four types of MA affected the gastric motility amplitude in varying degrees. Specifically, 2 Hz MA exhibited the most effective results, while 4 Hz MA had the least effect; the effects of 1 Hz MA and 3 Hz MA were between the effects induced with 2 Hz and 4 Hz. Furthermore, the response of gastric vagal afferent nerve discharge and gastric motility was examined after MA treatment with frequencies of 2 Hz and 4 Hz, respectively, on ST36 in order to elucidate the mechanism of MA regulation of gastric motility. The results showed that 2 Hz MA was able to increase the amplitude of gastric motility and discharge frequency of gastric vagal afferent nerves, while 4 Hz MA exhibited seldom effects. These findings suggest that gentle MA (2 Hz) has more stimulating effects than strong stimulation with MA (4 Hz) on gastric hypomotility. In addition, gastric motility regulated by MA was associated with vagal afferent nerve activation.

EA at PC6 Promotes Gastric Motility: Role of Brainstem Vagovagal Neurocircuits

Background. We aimed to assess whether electroacupuncture (EA) at PC6 affects gastric motility via the vagovagal reflex and if so whether brainstem vagovagal neurocircuits and related transmitters are involved. Methods. Gastric motility was measured in male Sprague-Dawley (SD) rats by placing a small manometric balloon in the gastric antrum. The rats were subjected to control, sham surgery, vagotomy, sympathectomy, and microinjection group, including artificial cerebrospinal fluid, gamma-aminobutyric acid (GABA), and glutamic acid (L-Glu). The effect of EA at PC6 on gastric motility was measured. Moreover, electrophysiological testing was used to measure the effect of EA at PC6 on the parasympathetic and sympathetic nerves. In addition, artificial cerebrospinal fluid, L-Glu, and GABA have been microinjected into the dorsal motor nucleus of the vagus (DMV) to measure the changes in gastric motility and parasympathetic nerve discharge induced by EA at PC6. Key Results. EA facilitated the gastric motility in control group. In the vagotomy group, gastric motility was not affected by EA at PC6. However, in the sympathectomy group, gastric motility was similar to control group. Acupuncture at PC6 increased parasympathetic nerve discharge but not sympathetic nerve discharge. Furthermore, the microinjection of L-Glu into the DMV increased gastric motility, although EA at PC6 showed no remarkable change in this group. The injection of GABA reduced gastric motility and parasympathetic nerve discharge, but EA at PC6 significantly increased gastric motility and the parasympathetic nerve discharge in this group. Conclusions and Inferences. EA at PC6—primarily by inhibiting GABA transmission to DMV—reduced the inhibition of efferent vagal motor fibers and thus promoted efferent vagus nerve activity and increased gastric motility.

Electroacupuncture Improved the Function of Myocardial Ischemia Involved in the Hippocampus-Paraventricular Nucleus-Sympathetic Nerve Pathway

We investigated the hippocampus-paraventricular nucleus- (PVN-) sympathetic nerve pathway in electroacupuncture (EA) at the heart meridian for the treatment of myocardial ischemia by observing PVN neuronal discharge, sympathetic nerve discharge, and hemodynamics parameters. Sprague Dawley (SD) rats were equally divided into four groups: Sham, Model, Model + EA, and Model + EA + Lesion. The model rat was established by ligating the left anterior descending branch of the coronary artery. Changes in the sympathetic nerve discharge and hemodynamic parameters were observed. The Model + EA exhibited a significantly lower discharge frequency of PVN neurons compared with the Model. The Model + EA + Lesion had a significantly higher discharge frequency compared with the Model + EA. The total discharge frequency of PVN neurons and interneurons were positively correlated with the sympathetic nerve discharge. The total discharge frequency of PVN neurons was positively correlated with heart rate (HR) and negatively correlated with mean arterial pressure (MAP) and rate pressure product (RPP). The discharge frequency of interneurons was positively correlated with HR and negatively correlated with MAP and RPP. The hippocampus-PVN-sympathetic nerve pathway is involved in electroacupuncture at the heart meridian and interneurons are the key neurons in PVNs.