Projections from the raphe nuclei to the phrenic motor nucleus in the cat.

The purpose of this study was to identify the projections from the brain to the phrenic motor nucleus in the cat by employing a retrogradely-transported fluorescent dye. Propidium iodide was iontophoresed into the phrenic motor nucleus which is located in the fourth, fifth and sixth segments of the cervical spinal cord. Retrogradely-labeled cell bodies were found in the brainstem within recognized respiratory areas.

Central gamma-aminobutyric acid involvement in blood pressure control.

The role of gamma-aminobutyric acid (GABA) in central nervous system (CNS) control of arterial blood pressure has been studied by testing the effects of drugs that either counteract or enhance CNS GABAergic mechanisms while monitoring the arterial pressure of normotensive and hypertensive animals. Drugs that antagonize the effects of GABA (either directly by blocking GABA-mediated responses or indirectly by inhibiting GABA synthesis) cause an increase in arterial pressure. This effect occurs in the forebrain and leads to an increase in sympathetic outflow to the vasculature, including the coronary vessels.

Medullary ventral surface GABA receptors affect respiratory and cardiovascular function.

We previously demonstrated that GABA and muscimol administered either into the cisterna magna or the fourth ventricle to chloralose-anesthetized cats cause respiratory depression, hypotension, and bradycardia. Injection of these substances into the lateral and third ventricles had no effect. In order to localize the site of action, muscimol and GABA were applied by Perspex rings to the ventral surface of the medulla.

Hindbrain GABA receptors influence parasympathetic outflow to the stomach.

Blockade of gamma-aminobutyric acid receptor function by direct microinjection of bicuculline into the nucleus ambiguous in cats produced a marked increase in gastric motility which was mediated by the vagus nerve. This effect was reversed by muscimol. These data indicate that the nucleus ambiguous may be an important brain site influencing gastric function and that the neurotransmitter controlling parasympathetic overflow from this nucleus to the stomach is gamma-aminobutyric acid.

Three versions of the additive theories of behavioral contrast.

The additive theories of behavioral contrast state that contrast will occur only when two types of responses interact during multiple schedules. Three more specific versions of the theories may be defined according to how they distinguish these two types of responses. A strong version physically distinguishes them.

Contrast and undermatching as a function of reinforcer duration and quality during multiple schedules.

Eight pigeons pecked keys under multiple variable-interval two-minute variable-interval two-minute schedules. In Experiment 1, the reinforcers were 2, 4, or 8 seconds access to a food magazine. In Experiments 2 and 3, the reinforcers were grains that had been determined to be most-, moderately-, or non-preferred.

Defining behavioral contrast for multiple schedules.

Two different definitions of behavioral contrast have been used for multiple schedules. One, interschedule, definition identifies contrast as changes in the rates of responding which occur when subjects move from one multiple schedule to another. The other, intraschedule, definition emphasizes changes in the rates of responding which occur relative to a baseline rate of responding.

An ultrastructural study of nerve terminal degeneration in muscle spindles of the tenuissimus muscle of the cat.

Muscle spindles in the tenuissimus muscle of the cat were studied between 12 and 168 h after cutting or freezing the nerve to this muscle. Degenerative changes in sensory and motor nerve terminals on intrafusal muscle fibres were observed using the electron microscope. Comparisons were made with spindles from unoperated or sham-operated cats.

Matching, contrast, and equalizing in the concurrent lever-press responding of rats.

Five rats pressed levers for food reinforces delivered by several concurrent variable-interval variable-interval schedules. The rate of reinforcement available for responding on one component schedule was held constant at 60 reinforcers per hour. The rate of reinforcement available for responding on the other schedule varied from 30 to 240 reinforcers per hour.

The internal auditory canal and sensori-neural hearing loss in homozygous sickle cell disease.

The dimensions of the internal auditory canal were compared in patients with SS disease and with or without abnormal audiograms to investigate the role of auditory nerve compression by expansion of the petrous, temporal bone in hearing loss. There was no correlation between abnormal audiograms and narrowing of the internal auditory canals and it was concluded that this mechanism was not responsible for the hearing loss in SS disease.