Unrestrained Cats Research Articles

Microelectrode study of the medial geniculate body in unanesthetized free-moving cats.

The behaviour of single units in the medial geniculate nucleus of the unanaesthetized unrestrained cat has much in common with that of units in auditory cortex, in terms of response categories and their relative proportions. The antero-posterior axis of the nucleus exhibits a very weak tonotopicity similar to that found in cortex. As in cortex, units responding to frequency change are often completely direction specific. On the other hand a high proportion of tone responsive units do so with inhibition. An apparently unique feature is the existence of ‘W-units’ which exhibit wide-band inhibitory response curves with a central region of excitation.

Effects of some sympathomimetic drugs and their antagonists on afterdischarges elicited in chronically isolated slabs of cerebral cortex.

1. The role of sympathomimetic agents in the maintenance and termination of induced cortical epileptiform activity was studied in chronically neuronally isolated slabs of cerebral cortex in the suprasylvian gyrus of unanaesthetized, unrestrained cats.2. The administration of the sympathomimetic agents (+)-amphetamine, methamphetamine, tyramine, and ephedrine resulted in a highly significant decrease in the duration of epileptiform afterdischarge (EADs).3. The alpha-adrenoceptor blocking drugs phenoxybenzamine, phentolamine and tolazoline did not significantly alter the duration of EADs but prevented the decrease in duration of EADs produced by the sympathomimetic drugs.4. The effect of atropine and arecoline on the duration of EADs, previously described, were not modified by the alpha-adrenoceptor blocking drugs, but atropine prevented and reversed the inhibitory action of amphetamine.5. It is suggested that (1) in the chronically neuronally isolated cortical slab there is normally no spontaneous adrenergic activity, (2) a cortical, cholinergic inhibitory mechanism, previously described, is modulated by ascending adrenergic influences, (3) adrenergic cholinergic linkages might be arranged in the cortex in an alternating network, as proposed by Feldberg.

Inguinal subcutaneous temperature changes in cats sleeping at different environmental temperatures

In unrestrained cats carrying chronically implanted electrodes and transducers inguinal subcutaneous temperature was studied during sleep at different environmental temperatures. Statistical analysis of the data shows that the slopes of inguinal subcutaneous temperature are negatively and positively correlated with environmental temperature during slow-wave and fast-wave sleep respectively. No correlation is observed between the slope of inguinal subcutaneous temperature and the slope of hypothalamic temperature during fast-wave sleep. The slope of hypothalamic temperature during fast-wave sleep is primarily correlated with hypothalamic temperature itself. The evidence suggests that fast-wave sleep is characterized by a change from homoiothermic to poikilothermic regulation probably caused by an alteration in the hypothalamic control of homeostasis during this phase of sleep.

Somatosensory responses of bulboreticular units in awake cat: relation to escape-producing stimuli.

In awake, unrestrained cats, bulboreticular neurons respond after electrical stimulation of cutaneous nerve with increasing discharge as stimulus intensity is raised to levels eliciting escape behavior. These cells discharge most vigorously to noxious natural somatic stimuli and are not driven by other sensory modalities. Electrical stimulation through the recording microelectrode also elicits escape, which further suggests bulboreticular participation in pain sensory mechanisms.

Somato-sympathetic reflexes during natural sleep and wakefulness in unrestrained cats.

In unrestrained cats with, chronically implanted electrodes reflex discharges evoked by afferent sciatic nerve stimulation have been recorded from the cervical sympathetic nerve during wakefulness and during the two states of sleep.

Effects of diphenylhydantoin and cholinergic agents on the neuronally isolated cerebral cortex

Earlier results led us to postulate the involvement of a cortical muscarinic inhibitory mechanism in the control of after-discharge duration in experimental seizures. We have now studied the interactions between anti-epileptic agents (diphenylhydantoin, trimethadione and ethosuximide) and scopolamine and pilocarpine. The ability of anti-epileptic agents alone and in combination with cholinergic drugs to suppress prolonged epileptiform after-discharges was evaluated in chronically neuronally isolated slabs of cerebral cortex in the suprasylvian gyrus of unanesthetized, unrestrained cats. Diphenylhydantoin (DPH) decreased duration of after-discharges; trimethadione and ethosuximide did not. This effect was evident within 15 min after injection and was proportional to the dose. There was a mutual antagonism between DPH and scopolamine. No interactions were observed between cholinergic drugs and anti-petit mal agents. Our results suggest that: (1) the chronically isolated cortical slab may be a model for grand mal epilepsy; (2) the action of DPH upon after-discharges is evident within a few minutes of its injection; (3) the anti-convulsant action of DPH may be exerted through cholinergic muscarinic inhibitory sites.

Cat assay for the emetic action of digitalis and related glycosides (digitoxin, digoxin, lanatoside C, ouabain and calactin).

1. A titration assay with two end points is described for comparison of the emetic and lethal potencies of digitalis-like drugs.2. A drug was infused at constant rate to a conscious, unrestrained cat, through an indwelling venous cannula. At the moment of vomiting the cat was rapidly anaesthetized and infusion continued at the same rate until the moment of cardiac arrest.3. With very slow and very fast infusions, the emetic and lethal doses tended to rise. In the range between these extremes (which varied from drug to drug) they were independent of time.4. The observations could be accounted for by analogue computation, assuming that the drugs entered an initial pool and were distributed at finite rates to receptors in the CNS (vomiting centre) and heart.5. Half times of metabolic loss derived from this computation for digitoxin, digoxin and ouabain (17, 9.9 and 1.8 h, respectively) were in the same ratio as the threefold longer half times reported for these drugs in man.6. When measured with infusion rates in the time independent range, the ratio of lethal to emetic doses did not vary between the drugs studied. All caused vomiting at 40% of the lethal dose.7. From a review of the literature, the emetic and cardiotoxic actions of digitalis-like drugs appear inseparable and probably share a common biochemical mechanism.8. It is concluded that foreseeable improvements in digitalis-like drugs are small and would depend on the elimination of any local emetic effect on gut receptors which they may have.

Reflex responses in the sympathetic and vagal nerve evoked by reticular stimulation during sleep and wakefulness.

Evoked potentials in the efferent vagal and sympathetic nerves following reticular stimulation were studied during wakefulness and sleep in unrestrained cats with chronically implanted electrodes.

Responses of bulboreticular units to somatic stimuli eliciting escape behavior in the cat.

Units were recorded from the brainstem of awake, unrestrained cats trained to escape electrical stimulation of a cutaneous nerve; stimuli sufficient to elicit escape were associated with natural pain behavior. Of the 104 units histologically localized, 59, recorded from the bulboreticular area of nucleus gigantocellularis (NGC), show maximal or exclusive response to noxious stimuli (36 units) and/or to nerve stimuli eliciting escape (39 units). Increased inter-stimulus activity commonly precedes escape behavior and is the only stimulus-related response observed from some units not driven by nerve stimulation. However, the pooled data from 39 of 53 units tested with nerve stimulation shows that responsiveness (chi-square, Kolmogorov-Smirnov statistic, and average spikes/ stimulus) increases with stimulus strength, reaching maximum levels at escape-producing intensities. Responses of some units to non-somatic inputs can be altered by repetitive noxious stimulation.

Relation between hypothalamic heat production and intra-and extracranial circulatory factors

Summary o 1. Studies were carried out on unrestrained cats to determine the temperature and blood flow patterns in the preoptic region and posterior hypothalamus during paradoxical sleep, and compare them with extracranial changes. 2. A marked temperature rise and blood flow increase were maintained in the hypothalamus during paradoxical sleep. The temperature of the extracranial rete also rose in parallel, but the subcutaneous temperature of the face fell inversely, although these extracranial temperature changes were not a constant sign of paradoxical sleep. 3. A selective temperature rise in the brain without temperature change in the extracranial rete and facial subcutaneous tissue was elicited by strong stimulation of the narcotized cat, and conversely a selective temperature rise in the extracranial rete was elicited by strong stimulation of the intensely alert cat. In the brain, the temperature response in the preoptic region and hypothalamus were not strictly parallel and did not correlate with the blood temperature of the common carotid artery. These results suggest that brain temperature is not greatly modified by extracranial temperature during such brief experiments. 4. An influence of local blood flow on brain temperature was indicated by an inverse correlation between the hypothalamic blood flow increase and temperature drop in response to arousal, which occurred only in the intensely alert cat in which background neural activity is probably at maximum level. Under different conditions a blood flow increase with arousal accompanied a parallel temperature rise. Thus, the metabolic heat production due to increased neural activity can be assumed to be much higher than the circulatory heat loss. 5. It is concluded that the temperature rise during paradoxical sleep was also mainly determined by metabolic heat production, and that the blood flow increase resulted from release of metabolic products.

Hemodynamic patterns during desynchronized sleep in intact cats and in cats with sinoaortic deafferentation.

In unanesthetized, unrestrained cats, placed in a sound-attenuated cage, stroke volume and cardiac output were continuously monitored by an electromagnetic flow transducer chronically implanted around the ascending aorta, arterial pressure was measured by means of a femoral catheter connected to a strain-gauge transducer, and heart rate by a cardiotachograph. Total resistance was computed by dividing arterial pressure by cardiac output. Electroencephalograms, cervical electromyogram, and ocular movements were also monitored to obtain evidence of naturally occurring sleep. In animals with intact sinoaortic reflexes the fall in arterial pressure occurring during desynchronized sleep was associated with a small decrease in cardiac output and a relatively greater reduction in total resistance. After sinoaortic deafferentation, the conspicuously exaggerated fall in arterial pressure occurring during the same type of sleep was almost entirely due to a parallel exaggeration of the reduction in total resistance; changes in cardiac output were only slightly greater than before deafferentation. Only in the few episodes of desynchronized sleep in which extreme hypotension was accompanied by signs of cerebral anoxia, did cardiac output greatly decrease; in these cases, calculated resistance was found to increase. Both small and large changes in cardiac output were independent of heart innervation.

Homeostatic mechanisms in the hypothalamus

1. The homeostatic readjustments associated with neuronal activity were studied through an analysis of local blood flow, temperature and electrical activity (EEG) in the hypothalamus of unrestrained cats with permanently implanted probes. 2. Three characteristic types of correlations among the three parameters were distinguished during the arousal response. Type 1 consisted of an increase in blood flow and temperature coinciding with EEG arousal. Type 2 occurred with prolonged, very mild reticular stimulation. During maintained EEG activation, the temperature and blood flow increased but only after a long latency. Type 3 was characterized by an immediate, transient increase in blood flow. 3. Small volumes of hypothalamic tissue were gently heated without stimulation by passing a train of square waves. This temperature rise represents physical heat production. When the hypothalamus was heated with stimulation, the hypothalamic temperature rose in two distinct steps. The first step was similar to the temperature rise due to physical heat production, the second step, representing metabolic heat production. The second temperature step was markedly depressed by small doses of pentobarbital; however, no significant changes in the first temperature step were observed. 4. It is concluded that metabolic heat production rather than thermal clearance probably determines the physiological temperature rise and the sudden-decrease type of blood flow response represents a sympathetic cerebrovascular reaction, and the occurrence of the immediate (first type) or of the delayed (second type) of response pattern depends on the rapidity of accumulation of vasodilator substances and on the rate of metabolic heat production.

Effect of sleep and waking on flash evoked discharges of lateral geniculate units in unrestrained cats

Effect of sleep and waking on flash evoked discharges of lateral geniculate units in unrestrained cats

An electromyographic analysis of muscular activity in the hindlimb of the cat during unrestrained locomotion.

AbstractDuring walking in unrestrained cats the electromyographic activity in many hindlimb muscles has been correlated with the angular movement in the hip, knee and ankle joints. The activity is rather uniform in the extensors but individual in different functional groups of flexor muscles. Observations on the precise timing of the onset of the main extensor activity suggest that it is not a reflex effect produced by stimulation of receptors (from muscle or skin) in the limb. It is assumed that the basic activity is a centrally programmed alternating activation of extensors and flexors. A possible reflex regulation mainly from la afferents of this basic activity is discussed with special attention given to factors that may elucidate the difference in movement at the hip on one side and the knee and ankle on the other.

Evidence for a muscarinic inhibitory mechanism in the cerebral cortex

The development of spontaneous electrical activity and of prolonged epileptiform afterdischarges has been studied in chronically neuronally isolated slabs of cerebral cortex in the suprasylvian gyrus of unanesthetized, unrestrained cats. Sessions of electrical stimulation at twice-weekly intervals prevented the development of both the spontaneous activity and the prolonged epileptiform response. Isolated slabs in animals that were left unstimulated for a period of 1 month exhibited a bursting form of spontaneous activity and responded to electrical stimulation with afterdischarges lasting for up to 5 hours. The ability of cholinergic agents to alter the duration of epileptiform afterdischarges in the chromically isolated slabs was tested. The cholinergic drugs—pilocarpine, arecoline, eserine, and oxotremorine—all significantly decreased the duration of afterdischarge. The antimuscarinic drugs atropine and scopolamine antagonized the anticonvulsant effects of the muscarinic agents. Methylatropine, in doses which blocked all the visible peripheral effects of the muscarinic drugs, neither altered the duration of afterdischarge nor antagonized the central effects of the muscarinic drugs. Nicotine and the antinicotinic agents mecamylamine and dihydrobeta-erythroidine, had no effect on duration of afterdischarge. It is proposed that the common basis for convulsive activity in the cerebral cortex is a defect in some as yet undefined pathway which includes a muscarinic inhibitory site.

On the validity of scalp recordings of the auditory evoked potential

Simultaneous recording from scalp and cortical electrodes in unanesthetized and unrestrained cats revealed essentially no differences between the superficial and deep recordings of the auditory evoked responses. Human recordings taken under two conditions of muscular contraction contained no major differences from 30 to 300 msec after stimulus onset.

Evoked potentials, neuronal activity and stimulus intensity in the visual system

Gross and neuronal evoked responses, obtained by stimulation with brief flashes of light, were recorded from the lateral geniculate body and the visual cortex of unanesthetized, unrestrained cats. It has been found that in the geniculate as well as in the cortex, the probability of neuronal discharge is highest at the times which correspond to the steepest negative slopes and lowest at the times which correspond to the steepest positive slopes of the gross response. These relations remain unchanged as the magnitude of the gross response is increased by stimuli of higher intensities, or its configuration modified by downward displacement of the recording microelectrode.

Unit responses of the lateral geniculate body to light flashes in free moving unrestrained cats.

E stata eseguita la registrazione di singole unita della parte dorsale del corpo genicolato laterale, in gatti non anestetizzati liberi di muoversi. Si dimostra che nella maggiore parte dei casi, le risposte ad un lampo di luce espresse in «spikes»/sec sono minime nel sonno sincronizzato, aumentano nella veglia e sono massime nel sonno desincronizzato. Qualora le risposte vengano riferite all'attivita «spontanea» precedente il flash, il rapporto risposta-attivita spontanea e maggiore nella veglia rispetto agli altri stati.

Monosynaptic and polysynaptic reflex excitation of motoneurones to plantar muscles in the unrestrained cat

Monosynaptic and polysynaptic reflex excitation of motoneurones to plantar muscles in the unrestrained cat

Changes in orienting activity of cat induced by chronic hippocampal lesions

Changes in orienting activity induced by lesions of the hippocampus were studied in 15 unrestrained cats. The orienting reflex was elicited by repetitive stimuli either “indifferent” or familiar to the animal. Electrocoagulations were followed by changes in spontaneous behavior of the animal (docility, reduced spontaneous affective manifestations), and by changes of orienting behavior (somatic reactions of small amplitude accompanied by poor vegetative-affective manifestations). The magnitude of behavioral change was a function of extent of lesions. These changes were due to the postlesion alterations of the control function exerted by the hippocampus upon the general behavior.