Cruciate ligament reflexes.

The idea of muscular reflexes elicited from sensory nerves of the cruciate ligaments is more than 100 years old, but the existence of such reflexes has not been proven until the recent two decades. First in animal experiments, a muscular excitation could be elicited in the hamstrings when the anterior cruciate ligament (ACL) was pulled, and tension in the ligament caused activity of the gamma motor neurones of the muscles around the knee. Impulses from the sensory nerves in ACL were activated during motion of the knee, in particular overstretching and combined extension and rotation. In humans, proprioception in the knee is decreased after ACL rupture. By mechanical or electrical stimulation of the ACL, an excitation in the hamstrings muscles can be elicited. During muscular activity, stimulation of the ACL or PCL results in a clear inhibition of the ongoing activity, both during static isometric and isokinetic muscle work, and also during dynamic activity (gait). This inhibitory reflex subjectively resembled giving way. The latency of the reflex was short in animals (about 3 ms) and long in humans (60-120 ms), probably caused by differences in the experimental setup and between species. The long latency in humans makes it unlikely that it is a directly protective reflex. Instead it may be involved in the updating of motor programs. Further research may characterize the reflex in details and map its pathways. The existence of this reflex indicate that the cruciate ligaments have an afferent function, which influences knee dynamics.     

Dilatation and closing anal reflexes. Description and clinical significance of new reflexes: preliminary report.

The present communication describes new reflexes which are called 'dilatation and closing anal reflexes', and discusses their clinical significance. The study comprised 21 healthy volunteers and 15 incontinent patients (7 with partial fecal incontinence and 8 with urinary stress incontinence). The technique comprised the introduction into the rectal neck of a balloon-tipped catheter. The balloon was inflated with air in increments of 10 ml up to 50 ml, and the EMG response of the external and urethral sphincters to balloon inflation and deflation was recorded. A new device called 'switch inflation' apparatus was used to inflate the balloon simultaneously with switching of the EMG apparatus. Rapid rectal neck inflation and deflation evoked external anal and urethral sphincter contraction. Slow and gradual inflation or deflation did not initiate the response. The anesthetized external anal sphincter did not respond to the stimulus, while the saline-infiltrated sphincter responded. The latency of the reflexes was recorded. In fecal incontinent patients, the external anal sphincter, on rapid rectal neck inflation or deflation, showed lower EMG activity and longer latency than in normal volunteers; the external urethral sphincter responded as in normal volunteers. In urinary stress incontinent patients, the external anal sphincter responded normally for both rectal neck inflation and deflation. The external urethral sphincter showed lower EMG activity and prolonged latency than normal on rectal neck inflation; it did not respond to deflation. The dilatation and closing reflexes seem to play a role in fecal and urinary continence as well as in fecal sampling. Detectable changes in latency or amplitude of the evoked response indicate a defect in the reflex pathway.(ABSTRACT TRUNCATED AT 250 WORDS)     

ACE-inhibitors and defence reflexes of the airways.

The group of angiotensin-converting enzyme (ACE) inhibitors is one of the drugs of choice for the treatment of hypertension and congestive heart disease. However, it has been reported that in some of patients ACE-inhibitors induce hyperreactivity of the airways with occurrence of a persistent dry cough, dyspnoe and wheezing. We supposed that the mechanism of these hyperreactivity is connected to accumulation of bradykinin, tachykinins and other inflammatory mediators in the airways. Increased local concentration of inflammatory neuropeptides stimulates bronchial C fibres and rapidly adapting receptors and provoke the cough reflex. Inflammatory processes in the airways could be followed by contraction of airway smooth muscle. In this study, our aim was to measure the changes of the number and intensity of mechanical induced cough in cats, which were treated for days with enalapril (5 mg/kg b.w.). After 15 days of treatment the reactivity of the lung and tracheal smooth muscles to the bronchoconstrictor mediator histamine was estimated. As to our finding 15 days of administration of enalapril results in significant increase of cough parameters measured with a more significant sensitivity of the laryngopharyngeal part. In the experimental animals we observed increased reactivity of bronchial smooth muscle to histamine after 15 days of enalapril treatment. The reactivity of the lung smooth muscle to the histamine was not significantly changed. These results confirmed the increased cough sensitivity and increased bronchial reactivity after enalapril treatment. These experimental animal model may be useful for the investigation of the pharmacological minimization of respiratory adverse effect of ACE-inhibitors.     

Defensive reflexes of the respiratory tract in dogs.

Intrapleural pressure, the tracheal air flow and tidal volume were recorded simultaneously in pentobarbital-anaesthetized dogs and changes occurring in them during defensive reflexes elicited by mechanical stimulation of the mucosa of different parts of the respiratory tract were evaluated quantitatively. The results show that, in addition to coughing and sneezing provoked by inserting a nylon fibre into the tracheobronchial region, the larynx and the nose, further respiratory reflexes described in other mammals also appear in these animals. Mechanical stimulation of the epipharynx with a fine polyvinylchloride catheter, for instance, also produces in dogs an aspiration reflex characterized by sniff-like inspiratory efforts without subsequent active expiration. Touching the vocal folds, however, produces an expiration reflex consisting of expiratory efforts without preceding inspiratory effort. The character of all these reflexes is typical and closely resembles their character in cats. Stimulation of the various parts of the respiratory tract sometimes evokes an apnoeic reaction instead of typical respiratory defensive reflexes.     

Physiological studies on facial reflexes in the rat.

Experiments were performed on 36 male albino rats anaesthetized with pentobarbitone sodium and paralyzed with gallamine triethiodide. Recordings were made with single and multibarrel glass microelectrodes in the facial nucleus and monopolar silver wire electrodes on the lingual, facial, glossopharyngeal and hypoglossal nerves. The absolute refractory period for facial motoneurones is 2-3 ms, the relative refractory period has a duration of 26-34 ms and the range in axonal conduction velocities is from 15 to 45 m.sec-1. No evidence for afferent fibres in the muscle branches of the facial and hypoglassal nerves could be found. The lingual and glossopharyngeal nerves show reflex connexions with both the facial and hypoglassal nerves. The time courses of the potentiations and depressions of test facial antidromic field potentials following lingual and glossopharyngeal conditioning stimuli are given. Evoked synaptic activity and the distribution of field potentials in the facial mucleus following lingual and glossopharyngeal nerve stimulation are also described. The observed lingual and glossopharyngeal-facial reflexes are discussed with respect to blink reflexes.