Relationship between photically evoked after-discharge occurrence and hippocampal EEG rhythms in restrained and unrestrained albino rats

The relationship between photically evoked after-discharge (PhAD) occurrence and dorsal hippocampal EEG patterns was examined in restrained and unrestrained albino rats during the presentation of 25 photic stimuli. Although the restrained and unrestrained conditions yielded significant differences in PhAD occurrence and type of hippocampal EEG pattern exhibited, it was determined that if the hippocampus displayed a rhythmical slow wave activity (RSA or theta) PhADs were not elicited. These hippocampal RSA periods were highly correlated with grid activity in the unrestrained condition. PhADs were elicited only during hippocampal EEG episodes that could be characterized as either large amplitude irregular slow waves or small amplitude irregular waves.     

Variations in deep body temperature in the young unrestrained pig over the 24 hour period

1. The temperature near the carotid artery has been measured in the unrestrained pig by means of radiotelemetry. When the animals were housed singly under constant conditions of temperature and lighting the temperature rhythm appeared to be related only to the time of feeding. A similar record was obtained from temperature measurements made in the hypothalamus.2. Over the range of ambient temperatures 10-30 degrees C the mean body temperature was 38.8 degrees C. No consistent variation occurred with ambient temperature, but on initial transfer from 10 to 30 degrees C ambient temperature the body temperature decreased, while on initial transfer from 30 to 10 degrees C it increased.3. When one pig was housed in a hut with a small outside yard a nychthemeral rhythm was sometimes superimposed on that imposed by feeding. When two pigs were kept in a paddock containing a hut the nychthemeral rhythm was more pronounced.4. It is concluded that in the pig there is very little innate circadian temperature rhythm and that the temperature variations seen are related chiefly to feeding and activity.     

Variations in sheep serum conglutinating complement activity and pathway involved in reactivity with sheep erythrocytes sensitized by rabbit antibody

Based on conglutination tests with the sheep E-rabbit A indicator system, three types of sheep sera were encountered. Type 1 sera failed to directly conglutinate or sensitize sheep E-rabbit A for conglutination by bovine conglutinin. Type 2 sera also failed to directly conglutinate sheep E-rabbit A but sensitized the indicator for conglutination by bovine conglutinin. Type 3 sera both directly conglutinated and sensitized sheep E-rabbit A for conglutination. Changes in serum type were induced in sheep by venepuncture (type 1 to type 2) or venepuncture and an intraperitoneal injection of yeast cells (type 2 to type 3). Direct conglutinating activity of type 3 sera was inhibited by heating serum at 50 degrees C for 30 min and was not restored by alternative activation pathway factor B. Chelation of Ca2+ in type 2 and 3 sera blocked sensitization of sheep E-rabbit A for conglutination by bovine conglutinin, indicating that the classical activation pathway was involved.     

Renal parameter estimates in unrestrained dogs

A mathematical formulation has been developed to describe the haemodynamic parameters of a conceptualised kidney model. The model was developed by considering regional pressure drops and regional storage capacities within the renal vasculature. Estimation of renal artery compliance; pre- and postglomerular resistance and glomerular filtration pressure is feasible by considering mean levels and time derivatives of abdominal aortic pressure and renal artery flow. If the level of flow is not greatly altered during an experimental sequence, it may also be feasible to estimate changes in glomerular filtration rate. Changes in the smooth muscle tone of the renal vessels induced by exogenous angiotensin amide, acetylcholine and by the anaesthetic agent halothane were estimated by use of the model. By employing totally implanted telemetry, the technique was applied on unrestrained dogs to measure renal resistive and compliant parameters while the dogs were being subjected to obedience training, to avoidance reaction and to unrestrained caging. An increase in vasoconstrictor tone in the renal artery and in the afferent arterioles in response to an increasing level of stimulation was demonstrated using this model.     

Measurement of blood pressure in unrestrained rats

A method that allows continuous recroding of blood pressure in rats and other small animals is described. Surgical, recording, calibration, and catheter construction techniques are explained. The techniques allow blood pressure recording from free-roving rats for relatively long periods of time but do not require complicated maintenance procedures to insure catheter patency.     

Flavor-nutrient learning in restrained and unrestrained eaters

After we consume a novel food an association can form between its sensory characteristics (e.g., taste properties) and the effect it has on the body (rewarding). Associations of this kind underpin much of our everyday dietary behavior because they mediate both the affective quality of food (flavor-preference learning) and the amount that we choose to consume (learning satiation). Notwithstanding this fact, very few studies have successfully demonstrated the process of dietary learning in human adults. In addition, based on evidence from related research, we explored whether learning is less likely to occur in individuals who have high scores on a measure of dietary restraint. Female participants (N = 44) consumed two differently flavored desserts. Each was presented three times on separate days. One was formulated with a high-energy content (1882 kJ) and the other with a low-energy content (226 kJ). After training, we found little evidence for learned satiation. However, we did observe flavor-preference learning. Specifically, participants acquired a greater liking and desire-to-eat the dessert flavor that was paired with a higher energy density during training. Further analysis revealed that this effect on liking is qualified by dietary restraint. As predicted, unrestrained eaters demonstrated greater differential responding to the two desserts than did restrained eaters. These data provide further evidence for flavor-nutrient learning in adults and they highlight a hitherto unexplored and potentially important difference between restrained and unrestrained eaters.     

Effect of p-chlorophenylalanine on thermoregulation in unrestrained rats

p-Chlorophenylalanine (PCPA), a serotonin depletor, was used to investigate thermoregulation of unrestrained unanesthetized rats exposed to warm (approximately 32 degrees C) and cold (approximately 3 degrees C) environments. PCPA (300 mg/kg, ip) was administered approximately 48-96 h prior to the experimental trials. After 60 min of warm exposure, PCPA-treated rats had a significantly smaller increase in mean tail temperature (3.05 degrees C) and a greater increase in mean core temperature (1.47 degrees C) than did the control rats (6.13 and 1.20 degrees C, respectively) as measured via chronically implanted thermistors. A noninvasive method, infrared photography, was also used to monitor skin temperatures following heat exposure. Changes were qualitatively similar to those seen with thermistors, although differences between control and PCPA-treated groups were not statistically significant. During cold exposure, thermistor measurements indicated that the decrease in mean core temperature of the PCPA-treated rats (0.62 degrees C) did significantly differ from that of the controls (1.11 degrees C), whereas tail temperatures did not. These data confirm other studies implicating serotonin in the thermoregulation of rats. In particular, these results show that in a warm environment, PCPA may alter, albeit subtly, peripheral vasodilation in unrestrained rats.     

Unsupervised whisker tracking in unrestrained behaving animals

Understanding how whisker-based tactile information is represented in the nervous system requires quantification of sensory input and observation of neural activity during whisking and whisker touch. Chronic electrophysiological methods have long been available to study neural responses in awake and behaving animals; however, methods to quantify the sensory input on whiskers have not yet been developed. Here we describe an unsupervised algorithm to track whisker movements in high-speed video recordings and to quantify the statistics of the tactile information on whiskers in freely behaving animals during haptic object exploration. The algorithm does not require human identification of whiskers, nor does it assume the shape, location, orientation, length of whiskers, or direction of the whisker movements. The algorithm performs well on temporary loss of whisker visibility and under low-light/low-contrast conditions even with inherent anisotropic noise and non-Gaussian variability in the signal. Using this algorithm, we define the speed [protraction (P), 1,081 +/- 322; retraction (R), 1,564 +/- 549 degrees /s], duration (P, 34 +/- 10; R, 24 +/- 8 ms), amplitude (P = R, 40 +/- 13 degrees ), and frequency (19 +/- 7 Hz) of active whisking in freely behaving mice. We furthermore quantify whisker deflection induced changes in whisking kinematics and calculate the statistics (i.e., speed, amplitude and duration) of whisker touch and finally show that whisker deprivation does not alter whisking kinematics during haptic exploration.     

Production of gastric ulcers in the unrestrained rat

A simple and effective procedure for inducing gastric lesions in the unrestrained rat is described. A significant feature of the present technique is that gastrointestinal lesions are observed following a relatively brief (6 hr) exposure to the shock-stress condition. Lesions are found to occur in the glandular portion of the stomach, and initial evidence implicates conflict as the ulcerogenic agent.     

The dark-discharge of the eye in the unrestrained cat

Summary The discharge of the ganglion cells of the retina of unrestrained cats in darkness (dark-discharge) has been recorded with large electrodes.Evidence is presented of sudden variations of the dark-discharge apparently spontaneous, as well of variations occurring concomitantly with the onset of the alert state of the animal.The research reported in this document has been sponsored by the Air Force Office of Scientific Research through the European Office of Aerospace Research, Oar, United States Air Force Grant AF Eoar 67-7 and by the Consiglio Nazionale delle Ricerche.     

Continuous measurement of cerebrospinal fluid pressure in unrestrained rats

A sensitive method for measuring intracranial pressure in unrestrained, unanesthetized rats has been developed. Two identically calibrated pressure transducers connected to fluid-filled polyethylene catheters were used to simultaneously monitor ventricular cerebrospinal fluid (CSF) pressure and head position. Artifacts due to changing head position were electronically subtracted from ventricular pressure, yielding a continuous dynamic record of “true” CSF pressure. A simple technique for precisely calibrating pressure transducers is also described. The mean CSF pressure obtained in 27 non-stressed freely-behaving adult rats was 64 ± 2 mm H₂O. Handling caused a prompt increase in intracranial pressure of approximately 80–120 mm H₂O. Moment-to-moment fluctuations in intracranial pressure closely reflect changes in central venous pressure. The techniques described are applicable to continuous measurement of CSF pressure in laboratory or clinical settings.     

Sleep-promoting effects of intraperitoneally administered uridine in unrestrained rats

An intraperitoneal injection of 0.1 nmol uridine in rats resulted in a transient excess slow-wave sleep if administered shortly before onset of the dark period. The sleep latency was remarkably shortened. A small dose (0.01 nmol) and larger doses (1, 10, 100 nmol) caused no effect. Uridine at a dose of 0.1 nmol was entirely ineffective if injected shortly before onset of the light period, while it resulted in transient excess paradoxical sleep if injected at an early phase of the light period. It is concluded that uridine, if timely administered through a systemic route, may pass the blood-brain barrier to modulate sleep in rats.     

Perception of complex signals by unrestrained cats

The ability of cats to discriminate modulation parameters of linearly amplitude and frequency-modulated signals was investigated under conditions of free behavior of the animals. The maximum variations of the amplitude and frequency of the modulated signals for which the probability of discrimination is equal to the threshold (0.75) are 1.6 dB and 150 Hz for a carrier frequency of 2.5 kHz. Replacement of one type of modulation by the other in those cases when stimuli with supraliminal values of the modulation parameters (15 dB and 1 kHz) leads to random selection during discrimination of these signals by the animals. In the case of an analogous replacement of the type of modulation for signals with threshold values of the modulation parameters, the probability of discrimination becomes significant (p>0.05).Translated from Fiziologicheskii Zhurnal SSSR imeni I. M. Sechenova, Vol. 75, No. 9, pp. 1194–1199, September, 1989.     

Bistable firing properties of soleus motor units in unrestrained rats

EMG recordings from single motor units in the soleus muscle were performed in alert unrestrained rats. A cuff electrode around the tibial nerve and subcutaneously placed electrodes in the foot permitted stimulation of afferent fibres. The movements of the rat and the simultaneous EMG activity were displayed together on a video monitor. Most motor units were tonically active for extended periods during quiet standing. During tonic discharge, maintained shifts between stable low (8-12 Hz; quartiles) and high (16-22.8 Hz) frequency ranges were initiated by short-lasting synaptic excitation of the motoneuron pool by stimulation of Ia afferents, or inhibition by stimulation of skin afferents. The shifts were not related to gross limb movements. This phenomenon is referred to as a bistable firing pattern. Bistable firing also occurred spontaneously during quiet standing. Typically the firing frequency shifted between a low (9-12.5 Hz) and a high (20-24.5 Hz) mode. During recordings of simultaneous activity in two units, spontaneous and stimulus-induced frequency jumps causing maintained changes in firing frequency were regularly seen to occur in one unit, while the frequency in the second unit was unchanged or only phasically influenced. These results demonstrate for the first time a bistable firing pattern during postural activity in the intact animal. The firing pattern closely resembles the bistable behaviour described in spinal motoneurons in reduced preparations, where it is due to the presence of a plateau potential. This suggests that the bistable firing is unexplained by plateau potentials also in the intact animal.     

Acid base status in unanesthetized,unrestrained guinea pigs

Acid-base status of arterial blood was measured in chronically cannulated, unanesthetized, unrestrained guinea pigs. Normal values were: pH=7.444±0.032,PaCO₂=35.7±4.4; HCO ₃ ^– =24.4±2.8; BE=+0.4±2.1 (n=69) andPaO₂=91.9±7.3 (n=25) (Values are mean±S.D.).Induction of light anesthesia with thiopentone caused a respiratory depression (decrease inPaO₂) accompanied by respiratory acidosis (increase inPaCO₂ and decrease in pH) and a development of slight metabolic acidosis (decrease in base excess and standard bicarbonate). Acid base parameters of guinea pigs are compared to those obtained from rats under identical experimental conditions.