Actions of the anaesthetic Saffan on rat sympathetic preganglionic neurones in vitro

Abstract

2ZD1 Whole-cell patch-clamp recordings were used to investigate the e ects of the anaesthetic Sa an on the electrophysiological properties of sympathetic preganglionic neurones (SPNs) in rat spinal cord slices. 2 Sa an (1 ± 54 mM) abolished or reduced the frequency of spontaneous action potential ®ring and abolished spontaneous, sub-threshold membrane potential oscillations. Sa an caused dose-dependent decreases in input resistance and depending upon the initial resting membrane potential, either a depolarization, a hyperpolarization or no change in membrane potential. 3 Responses to Sa an were blocked by the GABA A receptor antagonists bicuculline (5 ± 20 mM) and picrotoxin (20 mM), but not by the glycine receptor antagonist strychnine (20 mM) indicating that they were mediated by GABA A receptors. 4 Changes in the properties of SPN action potentials were also observed. In the presence of Sa an the amplitude and duration of the action potential after-hyperpolarization were reduced and larger depolarizations were required in order to evoke trains of action potentials. 5 To examine the e ects of Sa an on electrotonic coupling between SPNs, experiments were performed with the Na + channel blocker QX-314 in the intracellular solution and antidromic oscillations were evoked by ventral root stimulation. Sa an failed to abolish antidromic oscillations, but reduced their amplitude and duration. This indicates that the abolition of spontaneous membrane potential oscillations was not a direct e ect on the coupling between SPNs, but was a result of the abolition of spontaneous activity by Sa an. 6 The responses to Sa an occurred within the plasma concentration range of Sa an during anaesthesia, suggesting that the electrophysiological properties of SPNs may be altered during anaesthesia with Sa an. This would be expected to lead to changes in sympathetic tone and in the integration of sympathetic output.

Intracerebroventricular Administration of Melanin‐Concentrating Hormone Suppresses Pulsatile Luteinizing Hormone Release in the Female Rat

“…In the study by Gonzalez et al . ( 23), blood samples were taken from the tail vein in the animals anaesthetized with Saffan, which acts via γ ‐aminobutyric acid (GABA) receptor ( 36). Because the anaesthetic agent (Saffan), as well as pentobarbital, which also activates GABA receptors, has been suggested to affect LH secretion ( 37, 38), the anaesthetized animal model may not be optimal for study of brain mechanisms regulating gonadotropin secretion.…”

Mapping the cellular electrophysiology of rat sympathetic preganglionic neurones to their roles in cardiorespiratory reflex integration: a whole cell recording study in situ

“…The proportion of silent SPNs under basal conditions (6%) in the WHBP is considerably lower than that seen previously from high thoracic SPNs in vivo (45% in cat (Boczek-Funcke et al 1992), 53% in rat (Gilbey et al 1986), 29% in cat (Dembowsky et al 1986)) or in rat thoracolumbar spinal cord slices in vitro (51% (Pickering et al 1991), 77% (Spanswick & Logan, 1990b), 92% (Sah & McLachlan, 1995)). This may in part be a consequence of the intact excitatory synaptic drive in the WHBP combined with the lack of anaesthesia (known to suppress SPN activity (Logan et al 1996;Nolan et al 1997)) but may also partly reflect a loss of descending inhibitory control from supra-tentorial structures. Additionally, the lack of pulse wave in the WHBP means that there will be less phasic baroreflex inhibition, although the baroreceptor reflex is still active and not completely unloaded (Simms et al 2007).…”

The anti-malarial drug Mefloquine disrupts central autonomic and respiratory control in the working heart brainstem preparation of the rat

“…Electrophysiological studies have revealed that GJs participate in communication between SPNs [10,19]. Further, rhythmic activity recorded from the IML, the spinal nucleus containing SPNs, is reduced with the broad spectrum GJ blocker carbenoxolone (CBX) and can be abolished by MF [20].…”