Physiology

DEXTER F. SPECK, Ph.D. Associate Professor Ph.D. Loyola University, 1981 Office: MS-515 Medical Center 0298 Tel: (859) 323-5383 E-mail: dfspeck@uky.edu Curriculum Vita (pdf)

We are investigating the mechanisms responsible for the neural generation of respiratory patterns. The respiratory control system serves as a useful model for discovering basic principles of rhythmic motor systems including the normal homeostatic responses to behavioral perturbations. Sleep, wakefulness, sneezing, coughing, vomiting, postural changes, etc. are all important behaviors that involve respiratory adaptations. Most of these perturbations involve afferent inputs that either initiate or modify the resultant motor program. Results from these experiments will further our understanding of these connections and are likely to help elucidate the basic mechanisms involved in modulation of the central respiratory pattern generator. This will aid in understanding central respiratory disorders such as sudden infant death or the sleep apnea syndromes.

Current experiments expand upon our previous findings concerning the nuclei and neurotransmitter receptor subtypes that are important in the processing of inspiratory-inhibitory reflexes elicited by stimulation of the superior laryngeal, intercostal, phrenic and vagus nerves and brainstem nuclei such as the dorsal, ventral and pontine respiratory groups. Stimulation of these inputs elicits an inspiratory termination and/or a transient attenuation of the motor output. These inhibitory reflexes are believed to represent distinct effects on the timing generation and pattern generation mechanisms.

These experiments involve techniques such as stimulation and/or recording of whole nerves, brainstem nuclei and individual neurons. Chemical, pharmacologic and electrolytic lesions are used to interrupt specific pathways. Extracellular recording of in vivo neurons permits close examination of the components of many reflexes. In addition, neuropharmacologic techniques (including systemic application and local microinjections of neurotransmitter receptor agonists and antagonists) are used to elucidate the specific synaptic connections between interneurons.

Recent Publications:

Richardson, D.R., Randall, D.C., and Speck, D.F. Cardiopulmonary System. Fence Creek Publishing, Madison, CT, 1998.

Karius, D.R. and Speck, D.F. Short-latency excitation of phrenic motor output by non-NMDA receptors. Brain Res. 682:235-238, 1995.

Ling, L., Karius, D.R., Speck, D.F. Role of NMDA (N-methyl-D-aspartate) receptors in the pontine pneumotaxic mechanism in the cat. J. Appl. Physiol. 76: 1138-1143, 1994.

Karius, D.R., Ling, L., Speck, D.F. Nucleus tractus solitarius and excitatory amino acids in afferent-evoked inspiratory termination. J. Appl. Physiol. 76:1293-1301, 1994.

Other Publications