Anticonvulsant actions of enflurane on epilepsy models in cats

The effects of enflurane on three epilepsy models were studied in cats. The models used were seizures in amygdaloid kindled cats and those induced by bicuculline and penicillin. The authors found that not only a subconvulsive (1.5%) but a convulsive (3.5%) dose of enflurane suppressed the seizures in all models. There was no sign of activation by enflurane of the epileptic focal activities in the dose range studied: the penicillin-induced cortical seizure was suppressed completely, and the threshold dose of bicuculline required to induce seizure in normal cats and the threshold current required to induce seizure in amygdaloid-kindled cats were both increased by both the subconvulsive and convulsive dose of enflurane. The pattern of suppression was, however, dissimilar in each model. It was dose dependent in the case of penicillin-induced seizure, while it was biphasic in several aspects in the seizures of bicuculline-induced and amygdaloid kindled models. For the subconvulsive dose the degrees of increase in the thresholds required to induce seizure in bicuculline-induced and amygdaloid-kindled models were both greater than those for the convulsive dose of enflurane. In spite of such a definite suppression of the excitability of focus, the propagation of amygdaloid after-discharge was facilitated by the convulsive dose. The intensity of convulsion induced by suprathreshold dose of bicuculline was depressed in a dose-related manner. The intensity of the convulsion in the amygdaloid-kindled model was also suppressed when it was estimated by visual inspection of behavior and the degree of activation of the brain electrical activities. The authors conclude that there is little, if any, exacerbation by enflurane of preexisting epileptic foci, the only exception possibly being the case of certain myoclonic type epilepsies such as progressive myoclonic epilepsy and photosensitive epilepsy. This anesthetic probably can be used with a considerable degree of safety for epileptic patients.

Osmium-impregnation patterns of the Golgi complex in the epididymal epithelial cells of castrated and testosterone-injected mice

After prolonged exposure of mouse epididymal epithelial cells to a solution of osmium tetroxide, reduced osmium compounds were detected in the Golgi cisternae and in the cytoplasm adjacent to the Golgi complex. Their appearance changed in time under certain conditions. Eight days after castration each cisterna of the regularly arranged Golgi lamellae fragmented into small vesicles, in which deposits of reduced osmium compound were in reduced amounts or completely absent, but no notable decrease of the fine reduced osmium particles in the cytoplasm adjacent to the Golgi complex occurred. The amount of deposit in the Golgi cisternae in castrated mice recovered to the normal level after the subcutaneous injection of testosterone for two weeks. On the other hand, the osmium particles observed in the cytoplasm adjacent to the Golgi complex during the recovery process of the lamellar structure increased in amount. This study showed that the reduced osmium compounds were of two kinds, and that the deposits contained in the Golgi cisternae were related to secretory products, and might be controlled by hormonal factors, but the fine reduced osmium particles that appeared in the cytoplasm adjacent to the Golgi complex might be regulated by other factors.

Selective bronchial suctioning in the adult using a curve-tipped catheter with a guide mark

Our results of previous and successive studies indicate that torque control of curve-tipped catheters is easily accomplished by placing a guide mark on the catheter. Thus, a guide mark was made on a curve-tipped 14 FG Portex suction catheter using a felt pen. The efficacy of selective bronchial suctioning using this catheter was studied in 50 patients. Directed suctioning of the left and right bronchial passages was performed in each patient 3 times and once, respectively, with the head in the midline position. The success rate of left bronchial suctioning was 92% (138/150 attempts) and success in right bronchial suctioning 98% (49/50 attempts). The curve-tipped catheter with a guide mark significantly improved the success rate of left bronchial entry over the previous rate from 50% to 92%.

Naloxone does not antagonize the anesthetic-induced depression of nociceptor-driven spinal cord response in spinal cats

The effects of several anaesthetics on spinal cord nociceptive neural mechanisms and their interactions with the opiate antagonist, naloxone, were studied in acute, spinal cord transected cats. Intra-arterial injection of bradykinin was used as the noxious test stimulus. Spontaneous activity and the neural response induced by bradykinin were recorded by the multi-unit activity technique in the lateral funiculus of the spinal cord. Naloxone, 0.1 or 2.0 mg/kg i.v. had little effect on the bradykinin-induced response, but enhanced the spontaneous firing of the lateral funiculus significantly. Fentanyl, 30 micrograms/kg i.v., depressed both the bradykinin-induced response and spontaneous firing. These effects of fentanyl were antagonized completely by naloxone, 0.1 mg/kg i.v. Nitrous oxide, thiamylal, halothane and ether depressed the bradykinin-induced response considerably, but it was not antagonized by naloxone, 0.1-2.0 mg/kg i.v. Enflurane had little effect on the bradykinin-induced response. The effects of these anesthetics on spontaneous firing were divergent: nitrous oxide enhanced it while other drugs depressed it, to various degrees. All these data suggest that the neural and/or neurochemical mechanisms of anesthetic-induced analgesia differ from mechanisms related to opioids.

Antianalgesic action of thiamylal sodium in cats

The effects of thiamylal on the nociceptor-driven neural activity in the spinal cord were studied in decerebrate, non-anesthetized cats. Noxious stimulation was induced by the injection of bradykinin into the femoral artery and the neutral response in the lateral funiculus was measured by the multi-unit activity technique. The effects of thiamylal on the bradykinin-induced response were compared before and after the spinal cord transection, above the recording site. Thiamylal, 5 mg/kg i.v., potentiated the response significantly before the cord transection and depressed it after the transection. These findings indicate that the antianalgesic action of thiamylal is induced at the spinal cord level: although this anesthetic agent does have a direct intraspinal depressant action, the multisynaptic neural network of the supraspinal pain inhibition system is more susceptible to the actions of anesthetics, and the depression of this descending system by thiamylal results in a release of spinal cord nociceptive neural mechanisms from the supraspinal control.

Nitrous oxide activates the supraspinal pain inhibition system

The effects th groups the changes in CO and SV were due mainly to a reduced demand of oxygen transport and expected changes in sympatho-adrenergic tone rather than to myocardial depression.

Pentobarbital-anesthetized and decerebrate cats reveal different neurological responses in anesthetic-induced analgesia

Cats were used to assess the significance of differences in animal preparations in the study of anesthetic-induced analgesia. Comparison was made between pentobarbital-anesthetized and decerebrate non-anesthetized cats. Bradykinin dissolved in normal saline was injected into the femoral artery as a noxious stimulus, and the neural response in the spinal cord lateral funiculus was recorded using the multi-unit activity technique. The magnitude of the neural response and the changes in spontaneous firing were compared before and after cervical cord transection at C1. Before the transection, the response was greater in anesthetized than in decerebrate cats. The cord transection potentiated the response in both preparations, but the degree of potentiation was greater in decerebrate than in anesthetized cats. These studies confirmed the presence of a descending pain inhibition system acting tonically on the nociceptive neural mechanisms in the spinal cord, and indicated the susceptibility of this system to pentobarbital. We conclude that pretreatment with pentobarbital induces pharmacologically a state of partial spinal cord transection and reduces the effects of drugs acting through supraspinal CNS structures.

Activation of the supraspinal pain inhibition system by ketamine hydrochloride

The neurophysiologic mechanism of ketamine-induced analgesia was studied in cats under conditions of electrolytic decerebration or pentobarbital anesthesia. Injection of bradykinin into the femoral artery served as the noxious stimulus and the neural response in the lateral funiculus of the spinal cord was recorded by the multi-unit activity technique. Ketamine depressed the bradykinin-induced response more markedly in decerebrate, non-anesthetized cats than in pentobarbital-anesthetized cats. The depressant action disappeared following cervical cord transection at C1, in both decerebrate non-anesthetized and pentobarbital-anesthetized cats. Thus the analgesic action of ketamine is probably exerted mainly through activation of the supraspinal pain inhibition system and a direct action on the spinal cord nociceptive neural mechanism, if any, is slight. The excitatory action of ketamine on the supraspinal pain inhibition system is susceptible to the depressant action of pentobarbital.