Modulation of propofol on the effects of blood pressure and firing activity of related neurons in the medulla.

Many studies have demonstrated that the ventrolateral medulla (VLM) plays an important role in the maintenance of systemic arterial pressure (SAP) and vascular tone. The VLM is divided into rostral (RVLM) and caudal (CVLM) portions which play opposing roles in regulating cardiovascular functions. The purposes of this study are to explore the relationship of fibers projecting between the RVLM and CVLM, and to investigate the effect of propofol (PPF, 2 mg/kg), an anesthetic agent, on modulating their neuronal firing rate (NFR).

Sympathetic-correlated c-Fos expression in the neonatal rat spinal cord in vitro.

An isolated thoracic spinal cord of the neonatal rat in vitro spontaneously generates sympathetic nerve discharge (SND) at ~25 degrees C, but it fails in SND genesis at < or = 10 degrees C. Basal levels of the c-Fos expression in the spinal cords incubated at < or = 10 degrees C and ~25 degrees C were compared to determine the anatomical substrates that might participate in SND genesis. Cells that exhibited c-Fos immunoreactivity were virtually absent in the spinal cords incubated at < or = 10 degrees C.

Acute effects of the cannabinoid receptor agonist WIN55212-2 on dopamine release in rat: an in vivo electrochemical study.

The aim of this study was to investigate the effects of the cannabinoid receptor agonist, WIN55212-2, and the cannabinoid receptor antagonist, SR141716A, on dopamine (DA) release evoked by KC1 (120 mM) microinjected into the striatum. The cannabinoid agonist WIN55212-2 (1 and 5 mg/kg, i.p.

Inhibitory effects of propofol on neuron firing activities in the rostral ventrolateral medulla.

The effect of propofol on neuronal activity in the rostral ventrolateral medulla (RVLM) is not well established. Therefore, we performed extracellular recording on neurons of the RVLM to investigate neuronal activity before and after administration of intravenous propofol. The mean systemic arterial pressure (MSAP), heart rate and integrated neuronal firing rate (INFR) in the RVLM were continuously recorded in anesthetized cats before and after intravenous injection of 2 mg/kg propofol or supplemental injections of 1, 2 and 4 mg/kg propofol that were given respectively.

Serotonin modulates glutamate action in the medulla to regulate cardiovascular functions in cats.

We examined the effects of serotonin (5-HT) on cardiovascular responses and blood flows in the right common carotid artery (RCCA), superior mesenteric artery (SMA) and right femoral artery (RFA), stimulated by glutamate (Glu) in the dorsomedial medulla (DM), rostral ventrolateral medulla (RVLM) and caudal ventrolateral medulla (CVLM). Microinjection of Glu into the DM produced increases in systemic arterial pressure (SAP) and flows in the RCCA and RFA, and decrease in flow in the SMA. Microinjection of Glu into the RVLM produced increases in SAP and decreases in flows in the RCCA, SMA and RFA.

GABAB-receptor-mediated suppression of sympathetic outflow from the spinal cord of neonatal rats.

Using a splanchnic nerve-spinal cord preparation in vitro that could spontaneously generate sympathetic nerve discharge (SND), we investigated the roles of intraspinal GABA(B) receptors in the regulation of SND. Despite an age-dependent difference in sensitivity, bath applications of baclofen (Bac; GABA(B)-receptor agonist) consistently reduced SND in a concentration-dependent manner. The drug specificity of Bac in activation of GABA(B) receptors was verified by application of its antagonist saclofen (Sac) or CGP-46381 (CGP).

Effects of asphyxia on arterial blood pressure, formation of nitric oxide in medulla and blood parameters in the cat.

The rostral ventrolateral medulla (RVLM) plays an important role in the integration of cardiovascular functions. We examined the effect of asphyxia on cardiovascular responses, on sympathetic vertebral nerve activity (VNA) and nitric oxide (NO) formation in the RVLM, on hemodynamics, and on plasma concentrations of catecholamines, blood gas partial pressures and carbohydrate metabolites. Using 16 anesthetized cats we found that the systemic arterial pressure (SAP), VNA, NO formation and the release of plasma catecholamine components of norepinephrine and epinephrine were increased during asphyxia.

Dexamethasone has a central antiemetic mechanism in decerebrated cats.

Dexamethasone is an effective antiemetic drug, but its mechanism of action is unclear. We designed this study to investigate the direct antiemetic action of dexamethasone in the medulla of cats. By using an oscillographic vomiting model, decerebrated cats received microinjections of dexamethasone 100 nL (1 microg, n = 7; 0.

The nNos/cGMP mediation of the depressor response to NMDA receptor stimulation in the caudal ventrolateral medulla.

Using in vivo voltammetry to directly measure extracellular nitric oxide (NO) levels, our previous studies suggested that the neuronal NO synthase (nNOS) and cyclic guanosine monophosphate (cGMP) signal transducing systems are involved in the cardiovascular responses elicited by activation of N-methyl-D-aspartate (NMDA) receptors in the rostral ventrolateral medulla. In this study, we examined if the depressor responses elicited by activation of NMDA receptors in the caudal ventrolateral medulla (CVLM) also depend on the actions of nNOS and soluble guanylyl cyclase. In anesthetized cats, microinjection of NMDA into the CVLM produced hypotension and bradycardia associated with NO formation.

Nitric oxide release in the nucleus tractus solitarius during and after bilateral common carotid artery occlusion.

1. The purpose of the present study was to investigate the effect of bilateral common carotid artery occlusion (BCCAO) on cardiovascular responses and nitric oxide (NO) formation in the nucleus tractus solitarius (NTS). 2.

Propofol inhibits neuronal firing activities in the caudal ventrolateral medulla.

Background: Propofol is a potent intravenous anesthetic. The action of propofol on the medullary depressor area, the caudal ventrolateral medulla (CVLM), has not been well established. We therefore performed extracellular recordings to study the neuronal activity of the CVLM in cats before and after intravenous propofol administration, to investigate its influence on neuronal firings.

Involvement of N-methyl-D-aspartate receptors in post-hypoxic depression of the dorsomedial medulla in cats.

Pressor and sympathoexcitatory responses induced by microinjection of glutamate (Glu) into the dorsomedial medulla (DM) were depressed after hypoxia in anesthetized cats. This study was undertaken to investigate which Glu receptor subtypes would be involved in the post-hypoxic depression. Hypoxia was induced by inhalation of a 5% O(2) and 95% N(2) gas mixture.

Coexistence of neurons integrating urinary bladder activity and pelvic nerve activity in the same cardiovascular areas of the pontomedulla in cats.

The present study examines the coexistence of neurons in the same cardiovascular point of the pontomedulla that integrates urinary bladder (UB) motility, and pelvic nerve activity (PNA). Microinjection of monosodium L-glutamate (Glu) into the locus coeruleus (LC), the gigantocellular tegmental field (FTG), the rostral ventrolateral medulla (RVLM), and the dorsomedial medulla (DM) produced pressor responses, whereas injection into the lateral tegmental field (FTL), the nucleus of tractus solitarii (NTS), and the caudal ventrolateral medulla (CVLM) produced depressor responses. However, microinjection of Glu into the dorsomotor nucleus of the vagus (DMV) and the ambiguus nucleus (AN), where the vagus nerve originates, produced marked bradycardia.