Sensory interaction with central 'generators' during respiration in the dogfish.

The activity in sensory and motor nerves of the gills was recorded from selected branches of the vagus nerve in decerebrate dogfish, Scyliorhinus canicula. Vagal motoneuronal activity was observed at the start of the rapid pharyngeal contraction and was followed by sensory nerve activity which preceded the slow expansion phase. Rhythmical vagal motoneuronal activity was still present after all movements had been prevented by curare paralysis although the frequency of the rhythm was higher than in the ventilating fish.

Mechanoreceptor activity in the gills of the carp. II. Gill arch proprioceptors.

The presence of gill arch proprioceptors in the gills of a teleost, Cyprinus carpio L., is demonstrated and their firing characteristics are analysed. Spontaneous activity of gill arch proprioceptors was recorded from epibranchial ganglia.

Mechanoreceptor activity in the gills of the carp. I. Gill filament and gill raker mechanoreceptors.

Physiological properties of gill filament and gill raker mechanoreceptors in the gills of spontaneously breathing carp, Cyprinus carpio L., were analysed. Stroking stimuli applied to gill filaments elicited a phasic mechanoreceptive response, which was recorded from neurons in the epibranchial ganglia.

A hierarchy of neural control of mastication in the rat.

In rats anaesthetized with ketamine, rhythmic jaw-opening and jaw-closing movements were induced by palatal stimulation. The two masseter muscles (jaw-closing) and the four digastric muscles (jaw-opening) were fitted with electrodes, which could be used either for electrical stimulation or for recording electromyographic responses. Electrical stimulation of the masseters in the phase when the digastrics were the contracting muscles, caused responses in the digastrics.

The respiratory function of gill filament muscles in the carp.

The activity pattern of the adductor muscles of the gill filaments has been determined with E.M.G.

Gill arch movements and the function of the dorsal gill arch muscles in the carp.

The activity coordination of the dorsal gill arch muscles in a teleost, the carp, is described and the effect of their contraction in combination with the respiratory pump movements is analysed. Based on their origin and insertion the dorsal branchial arch muscles can be divided into three groups: the external branchial arch levators, connecting the branchial arches to the neurocranium, the internal branchial arch levators, connecting the pharyngobranchials to the neurocranium and the dorsal oblique muscles, interconnecting the branchial arches and pharyngobranchials. Functionally, however, there are only two categories with the following properties.

Peripheral influences on the central pattern-rhythm generator for tongue movements in the rat.

Rhythmic activity in the tongue and other oral muscles was evoked by mechanical stimulation of the hard palate in ketamine-anaesthetized rats. The relation between neural discharges of single hypoglossal motoneurones and activity in the masseter and anterior digastric muscle, and stimulus parameters was analysed. By varying the stimulus parameters, hypoglossal-motoneurone activity was modulated from phasic reflex activity into rhythmic activity.

Interaction of respiration with coughing, feeding, vision and oculomotor control in fish.

Data on the interaction between respiration, coughing, feeding, vision and oculomotor control in fish have been analyzed. A self-contained respiratory rhythm generator in the brainstem reticular formation is, at times, interrupted by a coughing generator, which is partly autorhythmic and partly under vagal afferent control. A number of cranial muscles are shared by the respiratory and masticatory systems.

Masseter, digastric and omohyoidal responses from weak mechanical oral stimuli in the chewing rat.

In rats anesthetized with ketamine, effects of jaw jerks (rise time 5 ms, strength 70 mN) applied in the open direction were studied both in the quiescent preparation and during rhythmic jaw-opening and jaw-closing movements (induced by mechanical stimulation of the palate). The left masseter, posterior and anterior digastric and omohyoid muscles were fitted with electrodes for recording electromyographic responses. In the quiescent state a jaw jerk causes responses in all recorded muscles.

Respiratory responses to stimulation of branchial vagus nerve ganglia of a teleost fish.

The effects of electrical stimulation of epibranchial vagus ganglia upon respiration of the carp were investigated. Single shocks evoked fast twitch responses in a number of respiratory muscles with latencies around 18 msec to the beginning and 30-35 msec to the peak of activity. Shocks given during abduction decreased the respiratory cycle duration by shortening abduction and accelerating adduction.

Tegmental neurons controlling medullary respiratory centre activity in the carp.

The dorsal mesencephalic tegmentum of the carp was explored for respiratory rhythmic neurons. The properties of two types of neurons which could be distinguished on the grounds of their firing pattern and their behaviour during paralysis and electrical stimulation were analysed. One group is involved in the control of a special type of respiration called bout-respiration and besides influences the frequency of the respiratory rhythm.

Identification of respiratory motor neurons in the carp and determination of their firing characteristics and interconnections.

Motor neurons of the respiratory muscles of the carp, located in the medulla oblongata, are identified with a signal averaging technique. Analysis of the firing characteristics of these neurons provides data on their activity patterns under different circumstances. The results show that, on the one hand, the number of spikes a motor neuron fires per respiratory cycle depends on the respiratory intensity, and can even be as low as one action potential per respiration.

Neural control and proprioceptive load matching in reflex respiratory movements of fishes.

A brief anatomical description of topographical arrangements of respiratory neurons in the fish respiratory medulla introduces a discussion centered on neural controls of reflex breathing movements during rhythmic and ram gill ventilation, especially the role of proprioception in "load matching." Paralysis experiments show that proprioceptive signals are processed in medullary respiratory areas of the brain. Some neurons depend completely on proprioceptive input for their activity, while others "mix" proprioceptive and rhythmic information.

Proprioceptive motor control in fish respiration.

The response of single respiratory neurones in the medulla oblongata of carp to short twitches of individual respiratory muscles were analysed. The muscle contractions were obtained through automatic electrical stimulation and could be consistently elicited in a predetermined phase relation to the ventilatory cycle. The results show that, apart from nerve cells which take part in long-term processing of proprioceptive information from several sources, neurones also exist which possess the properties of elements of a peripheral proprioceptive control loop such as tension receptor neurones, length or stretch receptor neurones and motor neurones.