Local circuit input to the medullary reticular formation from the rostral nucleus of the solitary tract

Am J Physiol Regul Integr Comp Physiol. 2008 Nov;295(5):R1391-408. doi: 10.1152/ajpregu.90457.2008. Epub 2008 Aug 20.

Abstract

The intermediate reticular formation (IRt) subjacent to the rostral (gustatory) nucleus of the solitary tract (rNST) receives projections from the rNST and appears essential to the expression of taste-elicited ingestion and rejection responses. We used whole cell patch-clamp recording and calcium imaging to characterize responses from an identified population of prehypoglossal neurons in the IRt to electrical stimulation of the rNST in a neonatal rat pup slice preparation. The calcium imaging studies indicated that IRt neurons could be activated by rNST stimulation and that many neurons were under tonic inhibition. Whole cell patch-clamp recording revealed mono- and polysynaptic projections from the rNST to identified prehypoglossal neurons. The projection was primarily excitatory and glutamatergic; however, there were some inhibitory GABAergic projections, and many neurons received excitatory and inhibitory inputs. There was also evidence of disinhibition. Overall, bath application of GABA(A) antagonists increased the amplitude of excitatory currents, and, in several neurons, stimulation of the rNST systematically decreased inhibitory currents. We have hypothesized that the transition from licks to gapes by natural stimuli, such as quinine monohydrochloride, could occur via such disinhibition. We present an updated dynamic model that summarizes the complex synaptic interface between the rNST and the IRt and demonstrates how inhibition could contribute to the transition from ingestion to rejection.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Algorithms
  • Animals
  • Calcium / metabolism
  • Electric Stimulation
  • Electromyography
  • Electrophysiology
  • Excitatory Amino Acid Antagonists / pharmacology
  • Female
  • Hypoglossal Nerve / drug effects
  • Hypoglossal Nerve / physiology
  • Image Processing, Computer-Assisted
  • Jaw / innervation
  • Jaw / physiology
  • Medulla Oblongata / drug effects
  • Medulla Oblongata / physiology*
  • Microinjections
  • Models, Neurological
  • Motor Neurons / drug effects
  • Motor Neurons / physiology
  • Muscle, Skeletal / drug effects
  • Muscle, Skeletal / innervation
  • Muscle, Skeletal / physiology
  • Nerve Net / drug effects
  • Nerve Net / physiology*
  • Neurons / drug effects
  • Neurons / physiology
  • Patch-Clamp Techniques
  • Pregnancy
  • Rats
  • Reticular Formation / drug effects
  • Reticular Formation / physiology*
  • Solitary Nucleus / drug effects
  • Solitary Nucleus / physiology*
  • Tongue / innervation
  • Tongue / physiology

Substances

  • Excitatory Amino Acid Antagonists
  • Calcium