Learning that food is inedible in freely behaving Aplysia californica..

Freely behaving Aplysia californica can learn that food is inedible. Ss were given access to seaweed tied into canvas and attached to a force transducer. Ss repeatedly found the stimulus, attempted to ingest it, and failed. The force transducer provided an objective record of the number of attempts made by the animal to ingest the stimulus, the length of each attempt, and its intensity (i.e., peak force exerted). Within 2.5 hrs, Ss showed significant declines in these 3 measures of response to the stimulus. When exposed to the same stimulus the next day, animals showed more rapid declines in responsiveness, which indicate a retention of learning. Training appeared to be specific. Responses to the seaweed Laurencia of animals previously trained on the seaweed Ulva do not differ from the responses of naive animals to Laurencia. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Morphine effects on the cardiovascular system of awake, freely behaving rats

The effects of small, i.v. infusion of morphine on the heart rate was studied in unanesthetized rats. A dose-response study indicated that all values of morphine between 5 and 1000 mug/kg resulted in a transient bradycardia. In addition, morphine doses above 20 mug/kg induced cardiac irregularities including atrial fibrillation, atrioventricular block and temporary cardiac arrest. When morphine was delivered daily over a period of eight weeks, cardiac responding (first arrhythmias and then the bradycardia) became tolerant at a time when catatonia was still present. These results indicate that in an unanesthetized rat, profound cardiovascular effects are seen to very small, mug range, doses of morphine.     

Serotonin at the laterodorsal tegmental nucleus suppresses rapid-eye-movement sleep in freely behaving rats

Serotonin [5-hydroxytryptamine (5-HT)] is believed to play an important inhibitory role in the regulation of rapid-eye-movement (REM) sleep. 5-HT may exert this effect on neurons of the laterodorsal tegmental (LDT) nuclei that are implicated as important in the generation of REM sleep and phasic REM events such as ponto-geniculo-occipital (PGO) waves and respiratory variability. In rat brainstem in vitro, 5-HT hyperpolarizes and inhibits the bursting properties of LDT neurons assumed to be involved in generating REM sleep and PGO waves. This study tests the hypothesis that in vivo 5-HT at the LDT nuclei suppresses REM sleep and phasic REM events. Ten rats were implanted with bilateral cannulae aimed at the LDT and with electrodes for recording the electroencephalogram, neck electromyogram, PGO waves, and diaphragm electromyogram. During REM sleep, 5-HT (100 nl; 1-1.5 mM), saline, or sham microinjections were performed; repeated microinjections were separated by approximately 1 hr. After the first microinjection, REM sleep as a percent of the total sleep time was reduced with 5-HT (mean percent REM, 19.9 +/- 2.5% for 5-HT vs 26.8 +/- 2.4% for saline; p = 0.02). REM duration was reduced by 37% with 5-HT (p = 0.01), but REM episode frequency was changed less consistently (p = 0.21), suggesting that 5-HT mainly disrupted REM sleep maintenance. Per unit time of REM sleep, 5-HT had no effect on the amount or variability of REM PGO activity (p > 0.740) or on the mean or coefficient of variation of REM respiratory rate (p > 0.11). With subsequent microinjections, the effects of 5-HT on REM sleep were similar. A dose-dependent REM sleep suppression with 5-HT was observed in five rats tested. These data suggest that in vivo 5-HT at the LDT nuclei suppresses REM sleep expression. Although 5-HT did not disproportionately reduce the occurrence of phasic events within REM, total REM phasic activity was reduced because of less REM sleep after 5-HT.     

Effects of nicotine, pilocarpine, and tetrahydroaminoacridine on hippocampal theta waves in freely moving rabbits

Fifty-eight patients with anorectal malformations were closely followed up for postoperative anorectal function. Constipation was noted shortly after anorectoplasty in 10 of 28 low anomalies (35.7%) treated with limited sagittal anorectoplasty (LSARP), in 18 of 25 high or intermediate anomalies (72.0%) treated with posterior sagittal anorectoplasty (PSARP), but in none of 5 high or intermediate anomalies treated with Rehbein's mucosa-stripping endorectal pull-through and anterior sagittal perineal anorectoplasty (R-ASAP). The constipation resolved mostly within 1-2 years after repair under conservative management, but persisted beyond 2 years after repair in 3/25 children with LSARP and 10/25 with PSARP. Anal soiling was noted in 1/23 (4.3%) LSARP and 6/22 (27.3%) PSARP patients, but normal anorectal function was attained in 20/23 LSARP (86.9%) and 11/12 PSARP patients (50.0%) by the time of toilet training. Manometric studies disclosed that the resting rectal pressure (RRP) was lower and the anorectal pressure gradient (ARPG) higher in the constipated than the non-constipated children, while the RRP was higher and the ARPG lower in the soiled than the non-soiled patients. The ARPG after R-ASPA was close to that of non-constipated and in between that of the constipated and soiled patients. The rectoanal sphincter inhibitory reflex was not related to defecation status or surgical procedures, but showed a tendency toward positive conversion with time or after exclusion of esctatic terminal bowel in the severely constipated. It is concluded that anorectal function in patients with repaired imperforate anus seems to be more affected by the extent of endopelvic dissection than by preservation of the terminal bowel or sphincter muscles.     

Dissociation of associative and nonassociative concomitants of classical fear conditioning in the freely behaving rat.

In this article we describe three experiments aimed at determining why the conditioned stimulus/stimuli (CS) elicits similar increases in heart rate in groups given paired and random training. The first study demonstrates that regardless of the pseudoconditioning control procedure used (random, backwards, shock-alone, or naive), the same pattern of results is obtained: the increases in arterial pressure are greater in the paired than in each control group, but the heart rate rises to the same extent in all groups. The second study determined that the context in which the responses are tested (conditioning apparatus vs novel test chamber) does not affect the general pattern of results obtained. The third study demonstrates that the superficially similar increases in heart rate in conditioned and pseudoconditioned rats are achieved by different physiological mechanisms: coactivation of the sympathethic and parasympathetic nervous systems in conditioned rats and sympathetic excitation alone in pseudoconditioned rats. Thus, the heart is influenced by associative emotional processes, but heart rate is not, under these conditions, a particularly useful index of those influences. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Imaging of hippocampal and neocortical neural activity following intravenous cocaine administration in freely behaving cats

We examined spatial-temporal patterns of neural activity, as inferred from 700 nm light reflectance, from the dorsal hippocampus and surrounding neocortex in seven freely behaving cats following 1.5, 2.5, 3.5 and 5.0 mg/kg intravenous cocaine administration. Images were acquired using a new technique which gathered reflected light from cortical and subcortical structures. Cardiac and respiratory patterning, collected simultaneously with optical images, revealed increased rates and diminished variation after intravenous cocaine administration. Cocaine increased reflectance correlates of hippocampal neural activity in a dose-dependent fashion over a 120 min period, with a lengthening time-to-peak effect (22-76 min). The largest dose resulted in an initial decrease, followed by the greatest enhancement in neuronal activity. Correlates of neural activation in the neocortex displayed an inverse dose-response curve to that found in the hippocampus; the time-to-peak effect was shorter (6-43 min) and the maximal change was reduced. Regional patches and bands of activation occurred during the period of the cocaine response, and were more pronounced in the hippocampus than the neocortex. Procaine, administered in a similar dose, slightly increased neural activity for 10 min in both the hippocampus and neocortex, and elicited a small increase in respiration. Cocaine induces a pronounced enhancement of neural activation in the neocortex and dorsal hippocampus; the time course of activation in the hippocampus parallels an increased respiratory pattern and outlasts the neocortical response. We speculate that hippocampal activation may be related to the profound respiratory acceleration found in response to cocaine.     

Sex difference of electromyogram of masticatory muscles and mandibular movement during chewing of food

The aim of this study was to investigate whether there were sex differences in the electromyograms (EMG) of the masticatory muscles and in the mandibular movement of young adults when chewing food. Twenty subjects with normal dentitions were selected. The 11 test foods selected were all easily available in Japan. The results showed firstly that although there were no significant differences of chewing frequency between males and females, females chew food more slowly with less masticatory force and narrower mouth opening width than males; and secondly it appears that the chewing function in females is lower than in males.     

Effects of coca chewing on hormonal and metabolic responses during prolonged submaximal exercise

The effects of coca chewing on prolonged submaximal exercise responses were investigated in chronic coca chewers and compared with a group of nonchewers. At rest, coca chewing during a 1-h period was followed by a significant increase in blood glucose, free fatty acid, and norepinephrine concentrations and a significant reduction in insulin plasma level. During prolonged (1-h) submaximal (65-70% peak O2 uptake) exercise, chewers displayed a significantly greater adrenergic activation (as evidenced by a higher level of plasma epinephrine) and an increased use of fat (as evidenced by a lower respiratory exchange ratio). The gradual increase in oxygen uptake (O2 drift) commonly observed during prolonged exercise was blunted in coca chewers. This blunting in O2 drift is not related to coca-induced changes in ventilatory or lactate responses to exercise but could possible be related to an enhanced glucose utilization by chewers during the late phase of exercise. The present results provide experimental evidence of the physiological effects of coca chewing that could explain the better ability of coca users to sustain strenuous work for an extended period of time.     

Neuronal spike activity in the nucleus accumbens of behaving rats during ethanol self-administration

Many lines of evidence support the importance of the nucleus accumbens (NAC) for ethanol-reinforced behavior. The nature of the neuronal activity that occurs in this region during ethanol self-administration is not known. We recorded from ensembles of single-units primarily located within the shell of the NAC during operant responding for oral ethanol solutions by well-trained rats. Of 90 units recorded from seven sessions from seven rats, 41 (46%) did not exhibit significant changes in relation to the experimental events. Of the 49 units (54%) that did exhibit significant phasic changes, alterations in firing rate occurred in relation to the following experimental events: operant response (63%), tone stimulus (20%), and ethanol delivery (63%). In addition, changes in spike activity during the intervals between the three experimental events were noted in 33% of the units. Most units (55% of responsive units) responded to multiple experimental events. Thus different but overlapping populations of neurons in the NAC represent each event that occurs along the temporal dimension of a single trial performed to obtain ethanol reward. The data suggest that the NAC plays a crucial role in linking together conditioned and unconditioned internal and external stimuli with motor plans to allow for ethanol-seeking behavior to occur.     

Dual character of plastic changes in neurons of the dorsal hippocampus (field CA1) during extinction of the orienting response in freely moving rabbits

The activity of 63 neurones of the dorsal hippocampus field CA1 was studied in unrestrained rabbits in different behaviour and in the course of repetitive afferent stimulation. It has been found that changes in the mean frequency of spontaneous activity of most neurones (90%) correlate with the kind of the animal's behaviour. Replacement of calm alertness by an active state is primarily attended with enhanced mean frequency of firing. Two types of response dynamics to a repetitive stimulation were revealed: 1) successive decrease of reaction and 2) gradual augmentation and subsequent drop. As stimulation went on most of the neurones revealed a change in the nature of responses: diffuse phasic and tonic reactions were replaced by structured responses of a specific type. The data obtained are regarded as proof of the hippocampus involvement in the organization of integrated orienting behaviour.     

Sensitivity of the cough reflex in awake guinea pigs, rats and rabbits

BACKGROUND AND AIM: Medical literature provides heterogeneous author's opinions concerning the application of various laboratory animals to cough research. Therefore the cough response to chemical stimuli was compared in awake guinea-pigs, rats and rabbits. METHODS: 15 adult guinea-pigs (TRIK strain) of mean body weight 435 +/- 35 g, 28 adult rats (WISTAR strain) of mean body weight 400 +/- 30 g, and 18 rabbits of mean body weight 3.2 +/- 0.3 kg were used. Awake animals were inhaling the aerosols of both citric acid and capsaicin. Animals were placed in a bodyplethysmographic box and two procedures of chemical stimulation were used: 3-5 minutes lasting inhalation of overthreshold concentration of tussive agents, and the second procedure resided in an exposure to a dose-response study with doubled concentrations of citric acid. The cough was analysed on the basis of air-flow changes measured by pneumotachograph. The effect of mechanical stimulation of airway musosa was studied in 13 rats anaesthetised by urethane (1 g/kg b.w., i.p.). The cough was then analysed on the basis of changes in pleural pressure measured by electromanometer using pleural cannula. RESULTS: All awake guinea-pigs were coughing during the exposure to both citric acid and capsaicin, too. Citric acid was potent to elicit cough in 42.9% of awake rats and capsaicin only in 28.6% of them. 61.1% of rabbits expossed to citric acid were coughing. Capsaicin was ineffective to produce cough in rabbits. The highest intensity of cough was in guinea-pigs. Guinea-pigs were the species reacting most intensively to citric acid dose-response exposure. The intensity of cough was not correlated with the concentration of citric acid in awake rats and rabbits. Mechanically induced cough was present in 53.8% of exposed rats under light urethane anaesthesia. CONCLUSIONS: 1. Guinea-pigs are the most useful laboratory animal for experimental studies of chemically induced cough. 2. The sensitivity of cough reflex in awake guinea-pigs could be characterised by the relationship between the intensity of cough and the concentration of the tussive agent. 3. The mechanically induced cough could be elicited in half of the rats under light urethane anaesthesia. (Fig. 4, Tab. 1, Ref. 21.)     

Effect of food conditioned operant reflex acquisition on the glutamate receptor binding in the rat brain

Glutamate receptor binding in the striatum of fast-learning (FL) and dull (D) rats was significantly higher than in the control. In slow-learning (SL) rats, this parameter was lesser than in the FL or D animals and even lesser than in the control. In all the groups of trained rats, the glutamate receptor binding level was increased as compared with the control, whereas in the brain cortex it was decreased. The glutamate-dopaminergic interaction seems to be important as a basis of learning ability.     

Effects of experience on stimulus-produced reflex inhibition in the rat.

Notes that acoustic-startle behavior in the rat is inhibited by changes in the auditory and visual environment which immediately precede reflex elicitation. A series of 7 experiments was conducted with 165 male Holtzman albino rats which established that this effect was not present in the naive S unless the preliminary stimulus was a relatively intense noise burst. With visual stimuli and moderate auditory stimuli the requisite condition for the production of reflex inhibition was that the S should have experienced the eliciting stimulus. Exposures to the to-be-inhibitory stimulus or to a conjunction of this stimulus and the eliciting stimulus were not necessary. Once established, the inhibitory effect was not degraded by week-long rest periods nor by "unreinforced" exposures to the inhibitory stimulus. It is conjectured that the experiential effect may reflect some increase in a nonspecific state of alertness or arousal. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Early experience and the development of reflex mechanisms of behavior in rabbits and children

Studies have been made on the possibility of influence of some external stimuli on the development of the inborn reflexes which maturate in postnatal life (knee jerk and plantar reflexes in infants, cleaning reflexes in rabbits). It was shown that external stimuli experienced by the organism in early ontogenesis may affect the development of immature inborn elements of behaviour. Repetitive evoking of the developing reflex increases the rate of formation of its definitive pattern. Elaboration of the conditioned reflex on the basis of such developing inborn one, on the contrary, leads to retardation of the latter. Early handling and repetitive placing the animal into experimental camera affect the development of total cleaning behaviour of rabbits.     

Effects of ketamine on somatosympathetic reflex discharges in cats

Effects of ketamine on somatosympathetic reflex discharges induced from sympathetic trunk with electrical stimulation of superficial peroneal nerve were investigated in 51 cats under anesthesia with urethane and alpha chloralose. These reflex discharges through spinal cord and medulla oblongata consist of two components, A and C reflexes, which are derived from somatic myelinated and unmyelinated afferent fiber respectively. Amplitudes of both A and C reflex potentials were depressed significantly after intravenous injection of ketamine 10 mg.kg-1. The maximum depression was observed 5 min after administration. In decerebrated cats with surgical transection at the midbrain, both A and C reflexes were also depressed after administration of the same dosages, and the maximum level of the depression was more profound than that in brain intact cats. After intrathecal injection of ketamine 1 mg.kg-1 to the lumbar spinal region, a slight depression of C reflex was found, but, dosages of 10 mg.kg-1 significantly depressed both A and C reflexes to the similar levels as those in iv injection to brain intact cats. The maximum depression was observed 30 min after administration. The depressive effects on both reflexes of intravenous ketamine 10 mg.kg-1 were not antagonized by naloxone 0.06 mg.kg-1 in brain intact cats. These results suggest that the suppressive effects of ketamine on somatosympathetic reflexes are caused by direct inhibition of medulla oblongata and spinal cord, whereas supra-midbrain regions may be activated by ketamine, and the effect of ketamine is predominant on medulla oblongata in this situation rather than on the spinal cord.     

Influence of the Esmarch splint on chewing and tongue muscle activity during sleep

To clarify the functional mechanism of the Esmarch device in the treatment of sleep apnea, its effect on muscle activity during sleep was studied electromyographically with and without the appliance at the inferior head of the lateral pterygoid muscle, the genioglossal muscle, and the masseter muscle in 15 patients with sleep apnea syndrome. During the obstructive apnea the muscles showed significantly lower amplitudes than before the apnea. No significant decrease in the amplitude was observed during the central apnea, but, after the obstructive and central apnea, significantly higher amplitudes were seen than beforehand. The amplitudes rose after the placement of the appliance, and the amplitudes of the genioglossal and lateral pterygoid muscles during obstructive apnea increased significantly after the insertion of the appliance. The results suggest that the device can activate the masticatory and tongue muscle activity and indicate that the muscles activated with the appliance can prevent obstruction in the oropharynx. The Esmarch device not only helps avoid obstruction by mandibular protraction, but also affects function by activating the muscles.     

Effects of postural changes of the upper limb on reflex transmission in the lower limb. Cervicolumbar reflex interactions in man

The influence of passive changes in upper limb position on the excitability of three myotatic arc reflexes (soleus, quadriceps, and biceps femoris) of the lower limb has been explored on 42 volunteers. The results indicate that the excitability of the three myotatic arcs can be influenced at a distance by postural modifications of the upper limb. When the ipsilateral upper limb is forwards or the contralateral backwards, a facilitation of both soleus and quadriceps tendon reflexes is observed while the biceps femoris reflexes are reduced. This pattern of facilitation and inhibition is reversed when the ipsilateral upper limb is backwards or the contralateral forwards. The facilitations as well as inhibitions of proximal myotatic arc reflexes are quantitatively more marked than that of the soleus reflex. Facilitation and inhibition are not linearly related to the angle of the arm with the trunk. Effects begin at a considerable angle, become maximal at 45 degrees, and progressively disappear for greater values. It is suggested that the distinct pattern of facilitation and inhibition which is exerted in reciprocal fashion on extensor and flexor motor nuclei might depend on the long propriospinal neurones connecting cervical and lumbar enlargements.     

Effects of prenatal protein malnutrition on hippocampal long-term potentiation in freely moving rats

It has been demonstrated that prenatal protein malnutrition significantly affects hippocampal plasticity, as measured by long-term potentiation, throughout development. This paper focuses on the hippocampal dentate granule cell population response to two separate paradigms of tetanization of the medial perforant pathway in prenatally protein-malnourished and normally nourished adult male rats. The 100-pulse paradigm consisted of the application of ten 25-ms-duration bursts of 400 Hz stimulation with an interburst interval of 10 s. The 1000-pulse paradigm consisted of the application of five 500-ms bursts of 400 Hz stimulation with an interburst interval of 5 s. No between-group differences were obtained for input/output response measures prior to tetanization. No between-group, nor between-paradigm, differences were obtained in the degree of population EPSP slope enhancement. However, in response to both paradigms, prenatally malnourished animals showed significantly less enhancement of the population spike amplitude (PSA) measure than normally nourished animals. Normally nourished animals showed a significantly greater level of PSA enhancement in response to the 100-pulse paradigm than the 1000-pulse paradigm. Prenatally malnourished animals showed no significant differences in the degree of PSA enhancement between the two paradigms. Results indicate that short duration bursts (< or = 25 ms) are more effective in inducing maximal PSA enhancement in normally nourished rats than longer duration stimulus bursts. The apparent inability of prenatally malnourished rats to transfer enhanced cellular activation (population EPSP slope enhancement) into enhanced cellular discharge (PSA enhancement) suggests that a preferential enhancement of GABAergic inhibitory modulation of granule cell excitability may result from the prenatal dietary insult. Such potentiation of inhibitory activity would significantly lower the probability of granule cell population discharge, resulting in the significantly lower level of PSA enhancement obtained from these animals.