Administration Of Nembutal Research Articles

Occlusion of the semicircular canal using argon laser.

The effects of argon laser on the bony semicircular canals were studied in the guinea pig. After intraperitoneal administration of Nembutal, the bulla was opened in order to approach the lateral and posterior canals. The anterior canal was approached through the posterior fossa. The argon laser was applied through a probe which was connected to a device from HGM Medical Laser Systems. One of the three semicircular canals was irradiated one to several times by argon laser (1.0-1.5 W x 0.5 sec). Histopathologic examination of the temporal bones revealed that the semicircular duct shrank immediately after irradiation. The laser produced a charred area in the bony canal wall. The semicircular canals gradually became fibrotic and ossified and completely occluded within several weeks. Heat produced in the bony canal may be responsible for the morphologic changes. On delayed observation, the cochlea of the canal-irradiated animals showed no morphologic changes. Auditory brain stem responses were normal. Caloric stimulation using 5 ml/5 sec of ice water revealed no response in the lateral canal-irradiated animals.

Effect of Nembutal narcosis on dynamics of orientation tuning of cat visual cortex neurons

The dynamics of orientation tuning (OT) were investigated in acute experiments on immobilized locally anesthetized cats during response development in 40 neurons of the primary visual cortex before and after Nembutal injection. The range of OT scanning decreased in 53.8% of neurons after Nembutal administration (on the average, by 53.4±5.1°; P<0.001); the phenomenon disappeared completely in some neurons. After Nembutal anesthesia, scanning in 20.5% of units either increased or started up in cases of its absence. The scanning range remained constant in 25.6% of neurons. The mentioned changes in the scanning range were consistently more accentuated in cells for which the preferred orientation, as estimated by standard criteria, was shifted under narcosis than in cells invariant to general anesthesia. In the latter group, units with an unchanged scanning range occurred four times more often at all stages of the experiment as against the group of “unstable” neurons.

Estradiol-induced LH release in juvenile female rats: nembutal blocks both the decline and the exposure of nonavailable pituitary LHRH receptor sites.

We have previously shown that, as seen in the adult rat, pituitary LHRH receptor content declines during the hours encompassing the first preovulatory LH surge. This decrease in receptor number was prevented, however, when pituitary membranes were treated with MgCl2 to dissociate endogenously bound ligand(s). The present study investigates: whether the first proestrous reduction in available LHRH receptors can be reversed by subjecting the pituitary membranes to a less drastic, dilution-washing procedure previously reported to be highly effective in dissociating bound LHRH, and whether Nembutal blockade of the proestrous decline in LHRH receptors also prevents the dissociation-induced exposure of additional LHRH binding sites. A premature LH surge was induced by exposing juvenile female rats to proestrous-type levels of plasma estradiol (E2) via Silastic capsules. A decline in available LHRH receptors was found around the time of this steroid-induced LH surge. A marked increase in receptor number was, however, observed upon dilution-washing of the membranes. The increase in receptor number was not accompanied by any changes in receptor affinity (ka). Nembutal administration blocked both the LH surge and the decline in available LHRH receptors. Moreover, dilution-washing of pituitary membranes from Nembutal-treated rats failed to uncover additional LHRH binding sites. The results suggest that a significant portion of the proestrous decline in pituitary LHRH receptors is due to a reduced availability of the receptor to binding. Whether such a phenomenon is due to true occupancy by endogenous ligand(s) or to binding-dependent localization of the receptor within the cell membrane is unclear.(ABSTRACT TRUNCATED AT 250 WORDS)

Participation of the liver receptors in the regulation of ion composition osmolality and extracellular fluid volume.

Characteristics of 106 fibres dissected from liver afferent nerves were examined on 52 cats anaesthetized with intravenous nembutal administration. The afferent discharge of these fibres has been recorded during intraportal infusions of the different test solutions (75, 300, 450 mM sodium chloride; 8, 10.7 mM potassium chloride in normal saline; 300, 600 mM glucose and mannitol in normal saline and water). The results of the experiments showed that hepatic afferent fibres differ from each other in the following: spontaneous discharge rate, response to different stimuli, threshold, and the adaptation rate. Various receptor units responded specifically to a change either in the intraportal volume, or the osmolality, or both to NaCl and KCl concentration in the portal circulation. These data suggest an existence in the liver of highly specific receptor's populations: mechano(volume)-, osmo-, Na+-sensitive and K+-sensitive one. These receptors can serve as an informative link in the regulation of the water-salt homeostasis.

PLASMA OESTRADIOL AND DELAYED OVULATION AFTER ADMINISTRATION OF SODIUM PENTOBARBITONE TO PRO-OESTROUS 5 DAY CYCLIC RATS

Injection of sodium pentobarbitone (Nembutal) into rats between 12.00 and 13.00 h on the day of pro-oestrus was fully effective in blocking the expected ovulation. In 75% of the rats, ovulation of the present generation of large follicles occurred 24 h later (delayed ovulation). Injection of Nembutal between 12.00 and 13.00 h on the day of pro-oestrus and at the same time on the subsequent day was fully effective in blocking the ovulation twice: in only two rats out of 13 did ovulation of the present generation of follicles still occur. When unilateral ovariectomy was performed immediately after injection of a single dose of Nembutal into pro-oestrous rats, delayed ovulation was significantly inhibited. However, after inhibition of ovulation by either two injections of Nembutal or one injection and unilateral ovariectomy, delayed ovulation could be induced by treatment with a small dose of oestradiol benzoate during the Nembutal-induced anaesthesia. It thus seemed that delayed ovulation failed because of disruption of oestrogen production after administration of Nembutal. The concentration of oestradiol-17beta in the plasma of Nembutal-treated pro-oestrous rats decreased rapidly during the 24 h after treatment. It is concluded that this decrease in the concentration of oestradiol is due to the inherent ageing of preovulatory follicles manifesting itself when exposure to the ovulatory surge of LH is inhibited.

Evidence for the Dependence of Serum Luteinizing Hormone Surge on a Transient, Enhanced Secretion of Gonadotropin-Releasing Hormone from the Hypothalamus

Data that a substantial, transient release of gonadotropin-releasing hormone (GnRH) from the hypothalamus is a prerequisite for the serum luteinizing hormone (LH) surge are presented. Ovariectomized rats, in which daily afternoon LH peaks can be induced by estradiol benzoate (EB), were used as the experimental model. These rats present a homogenous, synchronized population having low hypothalamic stores of GnRH, thus facilitating detection of small physiological fluctuations in the levels of hypothalamic GnRH. Blockade, by Nembutal administration, of the serum LH surge on 2 consecutive afternoons results in elevated GnRH levels in the hypothalamus (1.79 ng in blocked rats vs 0.94 ng in controls). Abolition of LH secretion by administration of antiserum to GnRH, unlike the Nembutal blockade, does not affect GnRH levels. These results indicate that the afternoon LH surge is dependent on a transitory, enhanced release of GnRH from the hypothalamus, reflected by a depletion of GnRH stores.

Effects of sodium pentobarbitone on serum gonadotrophin levels and on the incorporation of 35S from methionine into protein in the brain and anterior pituitary during the oestrous cycle of the rat.

Ovulation was delayed for 24 h after the administration of sodium pentobarbitone (Nembutal, 35 mg/kg body weight) at 14.00 h, before the critical period on the afternoon of pro-oestrus. The expected preovulatory surge of serum LH at 18.00 h of pro-oestrus was also delayed until 21.00 h on the following day; however, increased levels (less than 12 ng/ml) were observed in 14 out of 23 animals (killed by decapitation) at 21.00 h on the day of Nembutal administration. The serum FSH rise observed on the morning of expected oestrus was extended after Nembutal treatment, and a further rise was noted 24 h later. Peak levels of incorporation of 35S from methionine into protein of the median eminence area (ME) and of the anterior pituitary (AP) which normally occur about the time of the preovulatory LH surge, were also delayed until 21.00 h on the day following Nembutal administration. Neither ovulation nor the preovulatory gonadotropin rises with their accompanying changes in incorporation in the ME and the AP, were altered by Nembutal administered after the pro-oestrous critical period. Thus Nembutal, while blocking ovulation, inhibits the circadian rhythm of incorporation of 35S from methionine in the brain as well as the peaks of incorporation in the median eminence and the anterior pituitary which accompany the normal preovulatory surges of gonadotrophin.

Periovulatory changes in ovarian prostaglandin formation and their hormonal control in the rat

The concentration of prostaglandins of the E-group (PGE) and F-group (PGF) and the activity of prostaglandin-synthetase in rat ovaries increased on the evening of the day of proestrus and reached a peak at 5.00 h on the following morning, i.e. about the time of ovulation. Enzyme activity and PG concentrations receded to basal levels by 10.00 h on the day of estrus. These changes were prevented when the proestrous gonadotropin surge was blocked by administration of nembutal, and could be restored by administration of either LH or of FSH freed of LH contamination. The spontaneous preovulatory rise in prostaglandin concentration was about 6-fold for PGF and 30-fold for PGE, compared with values observed during the remainder of the cycle, whereas the rise in prostaglandin synthetase activity was only about 1.7-fold. The LH effect on PG accumulation had a latency of 2–4 h, which argues for enzyme synthesis rather than activation of preformed enzyme as the mechanism responsible. The small magnitude of the change in enzymic activity suggests that LH may, in addition, augment the availability of PG precursors. The results are compatible with the concept that prostaglandins play a physiological role in the gonadotropin-induced process of follicular rupture.

Trace effects after polarization of single cortical units recorded extracellularly

After-effects arising after polarization of single units of the sensorimotor cortex of unanesthetized rabbits through the extracellular recording microelectrode were studied. In most neurons, after both excitatory and inhibitory currents, prolonged changes in activity were observed, consisting of an increase or decrease in discharge frequency compared with initial levels. With currents up to 20–30 sec in duration the mean duration of the after-effect is similar to the polarization time, while with prolonged (5–10 min) polarization it does not exceed 2–3 min. The after-effects are particularly well marked in neurons exhibiting significant changes in discharge frequency against the background of polarization, either as an increase (gradual activation or “escape from inhibition”) or as a decrease (adaptation or gradual inhibition). No significant changes in after-effects are found after administration of nembutal (30–40 mg/kg). The results are discussed in the light of data obtained by means of intracellular microelectrodes (28). It is suggested that after-effects following extracellular polarization, like those following intracellular, are due not to circulation of impulses in neuron networks, but to adaptive properties of the excitable membrane. The two types of effects after switching off an extracellular current in one direction are explained by assuming that such a current has a twofold action, depolarizing some parts of the membrane and hyperpolarizing others.

Effect of Nembutal on neuronal responses in the visual cortex

1. After administration of Nembutal (25–30 mg/kg) changes take place in the evoked potential and unit response of cortical neurons: amplitude of the primary surface-positive wave is increased, the slow surface-negative wave is shortened, and after 80–120 msec a new surface positive-negative wave appears, followed by another series of similar waves. In the unit response of certain neurons (types B1, B2 and M) the inhibitory pause is shortened by the appearance 80–120 msec after the flash of a new group of discharges, as a rule correlating well with the newly appearing surfacepositive and deep-negative wave. No distinct changes are seen in neurons with type D responses. 2. For the most common response in rabbits anesthetized with Nembutal the first activation phase has a shorter latent period and is of short duration. 3. The recovery cycle of cortical neuronal responses after administration of Nembutal is shortened. It is postulated that the inhibitory processes evidently responsible for the phase of subnormality in the recovery cycle of the responses after the first stimulus, are weakened.

Distinct spike discharges in the evoked cortical response of the light adapted cat

Following adaptation to white background illumination, photic stimulation produced several spike-like discharges situated between the primary and secondary complexes. With fixed stimulus intensity and serially augmented levels of light adaptation these discharges were found to increase in amplitude. The potentials may be divided into two groups: early and late spikes. The former were produced at higher levels of light adaptation, the latter at a low levels of adaptation. Bilateral, ipsilateral and contralateral stimulation and light adaptation studies indicated that the discharges occurred only when the stimulus and adapting light were presented to the same eye. The discharges were affected by Nembutal administration.

Effects of Barbiturates on EEG in Adult Chickens: Intraperitoneal Administration

A characteristic excited period accompanied by slow waves (6 to 12 cps.) with moderately high amplitude (200 μV.) was transiently found in the adult Japanese quail under early stage of intraperitoneal administration of moderately large dose (about 50 mg./kg.) of Nembutal (Ookawa and Kadono, 1967). This period was not conspicuous in the adult chicken anesthetized with intravenous injection of Nembutal (Ookawa and Gotoh, 1965). The experiments reported here conducted to examine the influence of intraperitoneal administration of Nembutal on adult chickens comparing with those observed in the Japanese quail.Ten adult White Leghorn chickens, 8 males and 2 females, were used. The recording technique and the site of implanted electrodes has been reported in detail in a previous publication (Ookawa and Gotoh, 1965), and will be summarized briefly here. The recording electrodes were made from the insect pins coated with enamel. The exposed tip of electrodes was about 0.5 mm… .

REFLEX POTENTIALS OF LUMBAR SYMPATHETIC TRUNK. WITH SCIATIC NERVE STIMULATION IN CATS

In order to analyse the reflex mechanisms of sympathetic nervous activities, reflex potentials were recorded from the lumbar sympathetic trunk of 56 chloralose anesthetized cats with single pulse stimulation of the contralateral sciatic nerve.1. Two kinds of reflex potentials were identified: the late reflex potential (LRP) with low threshold and long latency (80-120 msec), and the less marked early one (ERP) with higher threshold and shorter latency (25-50 sec).2. The LRP disappeared whereas the ERP was still observed following spinal transection at the Cl or Th8 level.3. Following brain stem transection made starting at the upper midbrain level downwards to the lowest level of the pons, the LRP as well as ERP showed no significant reduction of amplitude. However with transections of the medulla oblongata from its highest level to downwards, the LRP decreased gradually in amplitude until it disappeared completely at the lowest level of the medulla oblongata, although the ERP was still observed.4. Following administration of Nembutal of graded doses, the LRP diminished rapidly and disappeared before the ERP did.5. No clear cut result about the time of disappearance of the two reflex potentials was obtained in the case of asphyxiation owing to markedly increased random sympathetic discharges following asphyxiation.6. On the basis of these experimental results, it was suggested that the reflex center of the LRP is located in the medulla oblongata and that of the ERP is in the spinal cord.

Effects of brain-stem stimulation upon hippocampal electrical activity, somatomotor reflexes and autonomic functions

In order to understand better the functional significance of hippocampal electrical activity, an attempt has been made to relate its changes with those of somatomotor, sudomotor and vasomotor activities. Experiments were conducted with locally anesthetized cats under Flaxedil. The animals were bilaterally vagotomized in the study of blood pressure. Four types of hippocampal electrical responses to the stimulation of various subcortical brain structures were observed. 1. 1. “Synchronization” (produced by the stimulation of the medial preoptic area, the medial hypothalamic region and the dorsolateral part of the midbrain tegmentum) was associated with facilitation of the monosynaptic gastrocnemius and mono- as well as polysynaptic peroneal reflexes, elevation of blood pressure and facilitation of skin potentials. 2. 2. “Desynchronization A” (elicited by the stimulation of the amygdala and the lateral preoptic area) was associated with inhibition of the gastrocnemius and peroneal reflexes, and depression of blood pressure. The skin potentials could be facilitated with strong stimulation. 3. 3. “Desynchronization B” (elicited by the stimulation of the bulbar ventromedial reticular formation) was associated with inhibition of the gastrocnemius and peroneal reflexes, skin potentials and elevation of blood pressure. However, depression of the latter was obtained after Nembutal administration. 4. 4. “Intermediate response” (elicited by the stimulation of the posterolateral hypothalamic region and the preoptic area) was associated with facilitation of the peroneal reflexes and of the skin potential, and with inhibition of the gastrocnemius reflex. Blood pressure, elevated in the absence of anesthesia, was depressed after Nembutal administration. In view of these experimental results, it is suggested that the slow wave components of hippocampal electrical activity might have a close relationship with somatomotor and vasomotor activities.

EXPERIMENTAL STUDIES ON THE EFFECTS OF OVARIECTOMY AND HYPOPHYSECTOMY ON BLASTOCYST IMPLANTATION IN THE RAT.

ABSTRACT The effects of ovariectomy and hypophysectomy on the third and fourth day of pregnancy on blastocyst implantation have been studied. The day on which vaginal sperm was found was considered as day 0 of pregnancy. It was found that ovariectomy at the 1st h on day 4 of pregnancy did not interfere with implantation when progesterone substitution was given. The same operation performed at the 17th h on the third day almost completely prevented implantation. Hypophysectomy followed by luteotrophic hormone treatment at the 17th h on day 3, however, did not interfere with implantation whereas pituitary extirpation on the 13th h on day 3 prevented implantation in most cases. A single administration of nembutal, atropine and reserpine several hours prior to the time hypophysectomy would have interfered with implantation did not delay implantation by 24 hours. Some cases of incomplete implantation are described in which implantation sites of normal size occurred simultaneously with unimplanted blastocysts in the same uterus. These blastocysts implanted following the administration of oestradiol. The results are discussed in relation to current views on the hormonal regulation of blastocyst implantation.

Effect of nembutal on circulating and tissue blood volumes and hematocrits of intact and splenectomized mice.

The effect of Nembutal on the circulating and tissue blood volumes and hematocrits was calculated by means of independent determinations of plasma and red cell volumes. Nembutal produced an increase in circulating blood volume accompanied by a reduction in the venous hematocrit. The blood volumes of liver, kidney, spleen and intestine rose following the administration of Nembutal, while the hematocrits of liver, lung, intestine and muscle declined, and that of kidney rose. The administration of Nembutal to splenectomized mice produces similar changes. The relationship of these alterations to changes in periphero-vascular tone are discussed.

Alterations in tissue plasma volume with nembutal anesthesia.

Effect of Nembutal administration on tissue plasma volume was determined in mice. Following the administration of Nembutal the circulating plasma volume increases from 1.1 ml to 1.3 ml. The plasma volume of the liver, kidney, spleen, lung and intestine exhibit an increase of about 35, 80, 85, 15 and 40%, respectively. The plasma volume of the skin displays a reduction of about 15%, while that of muscle reveals no significant change. These alterations in tissue plasma volume were not the result of changes in the capillary permeability to or the rate of metabolism of the injected radioiodoalbumin tracer.

The Use of Nembutal Anesthesia in Milk Secretion Studies

Summary It was shown that goats maintained under nembutal anesthesia continue to secrete milk of normal composition at the normal rate. Comparisons between arterial and mammary venous blood samples drawn from goats anesthetized with nembutal showed that the uptake of milk precursors continues under these conditions. In view of these results it was pointed out that the adverse effects caused by excitement of the animal while drawing arterial and venous blood samples may be eliminated by the administration of nembutal.

Observations on Effect of Repeated Administration of Nembutal in Guinea Pigs

The nembutal, sodium-ethyl (1-methyl-butyl) barbiturate, was dissolved in water and injected intraperitoneally into guinea pigs to see whether they had a tolerance for the drug. The animals were divided into 2 groups: (1) those receiving the drug twice weekly and (2) those receiving it daily. The doses varied from 7.5 to 20 mg. per kilo body weight, but the dose for each pig remained constant. The minimum fatal dose (M.F.D.) was found to be 60 mg. per kilo. This amount killed 90% of the pigs. To study the effects of the drug, the periods of time required for the development of 3 phases in the hypnotic state were selected: (1) the time from the injection until the animal could not move forward after painful stimulation (pinching); (2) the time from the injection until the animal could move forward after painful stimulation, and (3) the time from the injection until the animal could walk with a steady gait. The onset of sleep followed the first of these phases. The weight of the animal greatly influenced the length of the hypnotic state, the heavier pig having the longer period of hypnosis, when the same size dose was given. There was, however, often considerable difference in the susceptibility of the individual animals which had approximately the same weight. Injections of 25% of the M.F.D. of the drug induced sleep in about 65% of the animals. If this amount is given semi-weekly, the hypnotic effect, as judged by the failure of the onset of sleep, is greatly reduced within 4 weeks. The length of period of hypnosis is also markedly shortened. Daily doses of 25% of the M.F.D. produce the same effects in a much shorter time. Pigs which had received 16.6 to 20.8% of the M.F.D. semi-weekly for 6 weeks showed a definite tolerance to 29.1 to 33.3% of the M.F.D. Pigs which had had several semi-weekly injections of 25% M.F.D., or several daily injections of as much as 25% to 33% of the M.F.D., and which had shown definite tolerance in both groups as measured by the duration of sleep and hypnosis, were not protected against a dose of 60 mg. (M.F.D.) per kilo.

A Reducing Substance in the Urine of Cats Under Nembutal Anesthesia

A series of 15 cats were given intraperitoneal injections of nembutal (sodium iso-amytal, penta-barbital), the average dose being 60 mg. per kilo. Urine samples were collected at intervals after the injection and later analyzed for reducing substances by Sumner's method. In certain instances the results thus obtained were checked by the use of Benedict's quantitative reagent. Simultaneously blood samples were taken and later analyzed for “blood sugar” by the Randle-Grigg modification of the Folin-Wu Micro Method. These observations were made in the course of experiments to determine the effect of stimulation of the tuber cinereum upon carbohydrate metabolism. Rather extensive surgical procedures under deep nembutal anesthesia were required in the experiments. The bladder was exposed and emptied and the urethra cannulated from one to 2 hours after the injection of nembutal. The first sample of urine was taken about an hour after the urethra was cannulated and from 2 to 3 hours after the administration of nembutal. This sample always showed the presence of an abnormal quantity of reducing substance, usually the maximum obtained during the experiment, the concentration decreasing progressively in subsequent samples. This maximum reduction where the lowest maximum was obtained, was equivalent to that produced by 240 mg. % of glucose. In the experiment where the largest maximum was found, the reducing substance was equivalent to that produced by 1575 mg. % of glucose. An average maximum value, equivalent to that produced by 1045 mg. % of glucose, was obtained. The amount of reducing substance in the urine was definitely related to the time interval following the injection of nembutal and not to the “blood sugar” concentration. Often in the later stages of the experiment the reducing substance would be decreasing in amount while the blood sugar was increasing.