Distinct Chambers Research Articles

The amygdala is essential for the expression of conditional hypoalgesia.

Two experiments were conducted to determine whether the amygdala is involved in the performance of hypoalgesia as a Pavlovian conditional response. Rats were trained by pairing a distinctive observation chamber with a series of 3 footshocks. Rats were returned to the chamber 24 hr later, and the time spent engaged in freezing behavior and stereotyped behavioral reactions to a subcutaneous injection of dilute formalin was recorded. Sham-operated subjects spent large amounts of time freezing and were hypoalgesic on the formalin test in relation to nonshocked controls. Small electrolytic lesions of the amygdala eliminated both defensive freezing behavior and hypoalgesia without altering baseline reactions to formalin. Larger lesions made with ibotenic acid produced a similar pattern of results implicating neurons intrinsic to the amygdala. These results indicate that the amygdala may represent a forebrain site critical for the activation of descending antinociceptive systems in response to certain classes of environmental stressors.

Caffeine-induced place and taste conditioning: Production of dose-dependent preference and aversion

Although caffeine may be the most widely used behaviorally active drug, few studies have examined its rewarding properties. In the present study, the designs of place-conditioning and taste-conditioning paradigms were combined in a single experiment to provide two independent measures of drug reward. During 3 preconditioning sessions, undrugged rats received access to 2 distinctive chambers connected by a small tunnel. During the 8-session conditioning phase, groups were given home cage access to either a sweet or salty solution, administered caffeine (0.3, 1.0, 3.0, 10.0, 30.0 mg/kg IP; 30.0 mg/kg SC), and confined to one of the chambers. On alternate sessions, rats were given home cage access to the remaining solution, injected with the vehicle, and confined to the opposite chamber. On test sessions 1 and 2, undrugged animals were given home cage access to one of the flavored solutions and water, and then allowed access to both conditioning chambers. On test session 3, rats were given access to both flavored solutions, injected with the drug used during conditioning, and again allowed access to both chambers. Caffeine (3.0 mg/kg) produced a significant place preference. The highest dose (30.0 mg/kg IP and SC) produced significant place and taste aversions. A control group given (+)-amphetamine illustrated a significant place preference and taste aversion as expected. Thus caffeine appeared to produce a dose-dependent biphasic effect; a lower dose was rewarding, whereas higher doses produced aversions to environmental stimuli associated with the drug.

Stephanospermum konopeonus (Langford) Comb. Nov.: A Medullosan Ovule from the Middle Pennsylvanian Mazon Creek Flora of Northeastern Illinois, U.S.A.

More than 150 permineralized ovules of Carpolithus konopeonus Langford, preserved in sideritic concretions, have been recovered from the Middle Pennsylvanian (Westphalian D) Mazon Creek flora of northeastern Illinois. Ovules were borne apically on slender branching structures. The sarcotesta is bilaterally symmetrical with a pair of distinct lateral wings and, at the apex of the ovule, forms a prominent funnel that leads to the micropyle. The sclerotesta is radially symmetrical with a prominent beak and collar at the apex. The nucellus is free from the integument except at the base and extends into the basal part of the micropylar tube. The apex of the nucellus forms a distinct pollen chamber. Ovule vasculature consists of six or more bundles in the sarcotesta and a continuous sheath of vascular tissue in the nucellus. Pollen preserved in the micropyle and pollen chamber is of the Monoletes-type The Mazon Creek material is assigned to a new species of Stephanospermum Brongniart as S. konopeonus (Langford)...

Cor triatriatum dexter: antemortem diagnosis in an adult by cross sectional echocardiography.

Cor triatriatum dexter is a rare cardiac abnormality in which the right atrium is subdivided into two distinct chambers. This anomaly is generally attributed to the persistence of the right sinus venosus valve and it is frequently associated with severe malformations of other right heart structures. The antemortem diagnosis of the membrane may be difficult and its presence is often only established at necropsy. In a woman of 56 with Ebstein's anomaly the echocardiographic features of cor triatriatum dexter were examined before and during cardiac catheterisation. These investigations showed the position of the membrane, that there was no gradient between the two atrial chambers, and that there were perforations in the centre of the membrane.

Pairing a place with lithium injection produces conditioning of a salivary response

Experimental rats were given pairings in which placement in a distinctive chamber was followed by an injection of lithium chloride; control rats received unpaired exposures. After two pairings, some of the experimental rats were observed to salivate in the chamber prior to the injection of lithium. The probability of this response increased with further training. No salivary responses were seen in control rats. This pattern of findings indicates that the pairings of a conditioned stimulus, the distinctive chamber, with an unconditioned effect produced by lithium resulted in Pavlovian conditioning of a salivary response. Since lithium was not observed to evoke salivary responding in the absence of conditioning, the conditioned salivary response was probably compensatory to the drug effect.

The Influence of a Taste Cue on an Environmental Aversion: Potentiation or Overshadowing

The present study assessed the influence of a taste cue on the establishment of an environmental aversion. Experimental animals were poisoned during confinement in a distinctive black chamber; control animals received nonillness experiences in the black compartment. In addition, half of the animals in the experimental conditions and half in the control conditions were exposed to a salient sucrose taste cue in the black compartment. The other halves were given water on the black side. All groups were further divided: half received sucrose; half, water in the white chamber. The results showed that experimental groups exhibited a strong aversion to the black compartment. This aversion was reflected in experimental groups in terms of both reduced intake during confinement to the black compartment in the conditioning phase and less time spent in the black chamber during testing than in the control groups. In addition, the presence of a salient sucrose taste cue in the black compartment during conditioning produced a stronger environmental aversion than did a nonsalient water taste cue presented in the same manner. These results indicate that the sucrose taste cue potentiated the development of an environmental aversion. However, potentiation only occurred when sucrose was on the black side and water was on the white side. Sucrose present in both the black and white chambers resulted in no potentiation of the environmental aversion.

Isolation versus grouped housing in rats: Differential effects of low doses of heroin in the place preference paradigm

Male Long Evans rats were reared from weaning (21–23 days) either in isolation or in groups of four for 40 days. Animals were then individually introduced to a testing apparatus consisting of two distinct chambers. A modified place preference paradigm was used consisting of 3 phases: (1) An habituation phase (4 days) during which rats were allowed free access to the entire test apparatus for 15 min. periods daily; (2) A conditioning phase (4 days) during which rats were confined to their non-preferred side for 15 minutes each day immediately following subcutaneous injection of 0, 20, 40 and 80 μg/kg of heroin HCl; (3) A test phase (1 day) during which rats were again allowed free access to the testing chamber following injection of vehicle. The difference in time spent on the conditioned side during habituation and test periods was determined. The group-reared rats showed similar effects for all doses of heroin whereas the same magnitude of drug effect was attained only at the highest dose used in the isolated rats. This differential sensitivity to heroin in the place preference paradigm is discussed in terms of the modification of behavioral effects of opiates by environmental influences.

Lithium chloride and avoidance of novel places.

Rats were exposed to a distinctive chamber (chamber A, part of a two-chamber apparatus), which was novel for half of the rats but familiar for the other half. Each rat was subsequently injected with lithium chloride or saline. In a test trial conducted 24 hr later, all rats were given a choice between chamber A and a second chamber (B), which was novel for all rats. The main result was that the group made familiar with chamber A and then given lithium showed a significant preference for that side or an avoidance of the novel side, a "spatial neophobia." A second experiment confirmed the spatial neophobia effect and demonstrated that it was not dependent on the particular conditioning procedure used in the first experiment. The spatial neophobia effect was related to similar effects in the taste aversion literature, and to the results of research on lithium-induced decreases in exploratory behavior.

Embryology of the ventricular septum. Separate origin of its components.

The formation of the ventricular septum was studied in human embryos ranging from 3.6 to 25 mm CR-length. Before septation, two distinct chambers are present which will contribute to the adult ventricles. They are called the bulbus and the ventricle. The circular constriction between these chambers is the bulboventricular fold. The anterior portion of the ventricular septum develops from this bulboventricular fold. Posteriorly, it fuses with a second septum, which is of purely ventricular origin. This is the inlet septum. Another portion of the bulboventricular fold persists as the trabecula septomarginalis. The trabecula septomarginalis divides the normal right ventricle into an inlet portion, stemming from the embryonic ventricle, and an outlet portion which derives from the bulbus.

Anatomy, histology and some aspects of histochemistry of the stomach in two primitive microchiroptera

The two openings of the stomach lie parallel to each other in both the species since the gastroduodenal junction is directed craniad. The fundic caecum ofTaphozous longimanus forms a distinct chamber due to the presence of shelves, one projecting from the dorsal side and the other from the ventral side. The cardiac glands ofTaphozous longimanus are unique and composed almost entirely of mucous secreting cells. These glands ofRhinopoma kinneari have very deep foveolae. Pepsinogen cells are abundant in the fundicregion of the stomach of both the species. There is no pepsinogen cell in the transitional zone and the pyloric glands contain mostly mucous secreting cells. The interstitial mucous cells of the cardiac glands and a part of the cranial half of the fundic caecum inRhinopoma kinneari contain acidic sulphated mucins. The histochemical characteristics of the gastric glands in the two bats have been described.

Post-Conditioning Devaluation of an Instrumental Reinforcer has no Effect on Extinction Performance

The extent to which a representation of the reinforcer controls an instrumental response can be assessed by studying the effect of post-conditioning changes in the reinforcer value. In the first experiment rats were trained to press a lever for sucrose pellets on a variable-interval (VI) schedule. The sucrose was subsequently devalued by pairing with Lithium Chloride (LiCl). This had no effect on lever pressing in extinction, although it profoundly reduced reacquisition responding and consumption. In Experiment II rats were trained to shuttle between the two distinctive chambers of a choice-box, in which lever pressing was reinforced in one chamber by sucrose and in the other chamber by food pellets programmed on independent VI schedules. A LiCl-induced taste-aversion was conditioned to the sucrose, and although this markedly affected reacquisition, extinction responding in the sucrose chamber and chamber preference were unaffected. These results indicate that instrumental performance can be independent of the current value of the reinforcer, and are discussed with reference to stimulus-response theory and second-order Pavlovian conditioning.

Suspected Sex Pheromone Glands in Three Economically Important Species of Dacus12

Recent work demonstrated the presence of a sex pheromone gland associated with the rectum of the male Queensland fruit fly, Dacus tryotni (Froggatt), which produced substances attractive to female files. Similar rectal gland complexes, which are described, also are present in at least 2 other species of male tephritids, the oriental fruit fly, D. dorsalis Hendel, and the olive fruit fly, D. oleae (Gmelin), which correspond closely in their anatomical and histological makeup to that described for D. tryoni . The gland consists of a reservoir occupying the right lateral posterior one-third of the rectal sac, and a small bulbular secretary sac opening into the reservoir at its base. Both structures are lined by folded layers of large epithelial cells. In a 3rd species, the melon fly, D. cucurbitae Coquillett, a rectal gland also is present, hut is situated ventro-laterally off of the rectal sac. It forms a distinct chamber connected to the rectal sac but remains separated from the lumen of this structure by bands of longitudinal and circular muscles. Internally, the epithelial lining consists of large epithelial cells greatly folded upon one another.

Riboflavin and mouse hepatic cell structure and function. II. Division of mitochondria during recovery from simple deficiency.

Mice which had been on a riboflavin-free diet for 6-8 wk were given daily intraperitoneal injections of riboflavin. The hepatic mitochondria, which in the deficient animals were greatly enlarged, were restored to normal dimensions within 3 days. Normalization of the mitochondrial population was brought about by division of the giant organelles. Dividing mitochondria were characterized by a membranous partition separating the inner compartment into two distinct chambers. Such organelles showed varying degrees of pinching at the level of the partition. The most common site of partition formation was at the base of a small mitochondrial bud. During the 1st day of recovery, dividing mitochondria were so common that they could be easily found in mitochondrial pellets. Injection of riboflavin into normally nourished mice also produced an apparent increase in the frequency of dividing mitochondria in the liver cells.