thiopental and Reflex--Abnormal

Topics: Anesthesia; Barbiturates; Blood Circulation; Gastroesophageal Reflux; Humans; Hypotension; Intubation, Intratracheal; Neuromuscular Depolarizing Agents; Neuromuscular Nondepolarizing Agents; Reflex, Abnormal; Succinylcholine; Thiopental; Time Factors; Vomiting

Potentiation of GABA(A) receptor-mediated inhibitory neurotransmission contributes to the anesthetic action of thiopental. However, the inhibiting action of general anesthetic on excitatory neurotransmission also purportedly underlies its effects. The aim of the study was to elucidate the role of glutamate receptors (NMDA and AMPA receptors) in thiopental-induced anesthesia. Intracerebroventricular (i.c.v.) NMDA (50 ng) significantly increased the induction time of loss of righting reflex and decreased sleep time induced by intraperitoneal injection (i.p.) of thiopental (50 mg/kg). Furthermore, NMDA at 50 ng i.c.v. increased the 50% effective dose values for thiopental to produce loss of righting reflex and immobility in response to noxious tail clamp by 25% and 21% (p < 0.05), respectively. However, intrathecal (IT) administration of NMDA or both of i.c.v. or IT administration of AMPA did not show such antagonizing effects on thiopental action at subconvulsive dose. Finally, thiopental (25 mg/kg i.p.) inhibited convulsions induced by NMDA (0.4 microg i.c.v.) or bicuculline (0.6 microg i.c.v.). However, i.p. muscimol (1 mg/kg) blocked the convulsions induced by bicuculline, but not those induced by NMDA at 3 mg/kg. Similarly, i.p. MK-801 (0.1 mg/kg) antagonized NMDA-induced convulsions, but not bicuculline-induced convulsions at 0.3 mg/kg. Therefore, we suggest that the effects of the selective GABA(A) and NMDA receptors on convulsive behavior are special to their sites of action, and that the inhibitory action of thiopental on NMDA receptors is possibly not mediated by secondary effects of its GABA(A) receptors agonism. These results above indicate the involvement of NMDA receptors in thiopental-induced anesthesia in mice.

Topics: Analgesics; Anesthetics, Intravenous; Animals; Anticonvulsants; Behavior, Animal; Bicuculline; Dizocilpine Maleate; Female; GABA Agonists; GABA Antagonists; GABA-A Receptor Agonists; GABA-A Receptor Antagonists; Male; Mice; Movement; Muscimol; N-Methylaspartate; Pain Measurement; Receptors, AMPA; Receptors, N-Methyl-D-Aspartate; Reflex, Abnormal; Seizures; Thiopental

This study evaluated the anesthetic effects of thiopental sodium, ketamine, and ether with concurrent administration of melatonin. The loss of righting reflex was taken to assess the onset of anesthesia. Melatonin (20 mg/kg, p.o.) potentiated the anesthetic effects of thiopental sodium (20 mg/kg, i.v.) and ketamine (50 mg/kg, i.p.). Melatonin pretreatment caused rapid onset of anesthesia after ketamine and thiopental sodium administration while the duration of action of these agents was prolonged. Melatonin failed to alter anesthetic effects of ether (2 mg/kg by open method) in rats. This study suggests that melatonin modulate mechanisms involved in induction of thiopental sodium and ketamine anesthesia.

Topics: Adjuvants, Anesthesia; Anesthesia; Anesthetics, Combined; Anesthetics, Dissociative; Anesthetics, Inhalation; Animals; Ether; Female; Hypnotics and Sedatives; Ketamine; Male; Melatonin; Rats; Reflex, Abnormal; Thiopental

It has been suggested that some anesthetic agents could exert their hypnotic/anesthetic effects by selectively blocking receptors involved in the central excitatory neurotransmission mediated by glutamate. In the present study, we analyzed whether riluzole (54274 RP), a novel compound that inhibits both the release and some postsynaptic effects of glutamate in some brain structures, has anesthetic properties in rats. For this purpose, we investigated whether 1) riluzole administered intraperitoneally (ip) at doses ranging from 2.5 to 45 mg/kg induces loss of righting reflex (LRR); 2) riluzole (2.5 and 5 mg/kg) prolongs sleep-times induced by either ketamine (30 or 80 mg/kg ip) or thiopental (25 or 35 mg/kg ip); 3) a 5-mg/kg subanesthetic riluzole dose affects the minimum alveolar concentration of halothane (MACh). Onset of drug action was defined as the period of time from the ip injection to LRR. Sleep-time was considered the period of time from LRR to restoration of righting reflex. Riluzole at doses greater than 15 mg/kg was able to induce LRR (riluzole dose for which LRR was achieved in 50% of the rats [ED50 = 25.6 mg/kg]). A positive correlation was found between the dose of riluzole and sleep-time (r = 0.92, P less than 0.001). A 5-mg/kg (but not 2.5-mg/kg) riluzole dose significantly prolonged sleep-times induced by both ketamine (30 and 80 mg/kg) and thiopental (25 but not 35 mg/kg).(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Anesthetics; Animals; Dose-Response Relationship, Drug; Drug Interactions; Excitatory Amino Acid Antagonists; Glutamic Acid; Injections, Intraperitoneal; Ketamine; Male; Rats; Rats, Inbred Strains; Reflex, Abnormal; Riluzole; Sleep; Synaptic Transmission; Thiazoles; Thiopental

Topics: Action Potentials; Adolescent; Adult; Anesthesia, General; Apnea; Biopsy; Central Nervous System; Child; Creatine Kinase; Electromyography; Female; Fever; Follow-Up Studies; Heart Rate; Humans; Male; Middle Aged; Muscles; Nerve Degeneration; Reflex, Abnormal; Succinylcholine; Thiopental