Dopamine D1/5 receptor modulation of firing rate and bidirectional theta burst firing in medial septal/vertical limb of diagonal band neurons in vivo

Thomas E. Fitch, Robert N. Sahr, Brian J. Eastwood, Feng C. Zhou, Charles R. Yang

Research output: Contribution to journalArticle

37 Citations (Scopus)

Abstract

The medial septum/vertical limb of diagonal band complex (MS/vDB) consists of cholinergic, GABAergic, and glutamatergic neurons that project to the hippocampus and functionally regulate attention, memory, and cognitive processes. Using tyrosine hydroxlase (TH) immunocytochemistry and dark-field light microscopy, we found that the MS/vDB is innervated by a sparse network of TH-immunoreactive (putative catecholaminergic) terminals. MS/vDB neurons are known to fire in rhythmic theta burst frequency of 3-7 Hz to pace hippocampal theta rhythm. Extracellular single-unit recording in theta and non-theta firing MS/vDB neurons and antidromically identified MS/vDB-hippocampal neurons were made in urethan-anesthetized rats. Tail-pinch noxious stimuli and ventral tegmental area (VTA) stimulation (20 Hz) evoked spontaneous theta burst firing in MS/vDB neurons. Systemic D1/5 antagonists SCH23390 or SCH39166 (0.1 mg/kg iv) alone suppressed the spontaneous theta bursts, suggesting a tonic facilitatory endogenous dopamine D1 "tone" that modulates theta bursts in vivo. Activation of D1/5 receptor by dihydrexidine (10 mg/kg iv) led to an increase in mean firing rate in 60% of all theta and non-theta MS/vDB neurons with an increase in the number of theta bursts and spikes/burst in theta cells. In strong theta firing MS/vDB neurons, D1/5 receptor stimulation suppressed the occurrence of theta burst firing, whereas the overall increase in spontaneous mean firing rate remained. In low baseline theta MS/vDB neurons D1/5 receptor stimulation increases the occurrence of theta bursts along with a net increase in mean firing rate. Atropine injection consistently disrupts theta burst pattern and reduced the time spent in theta firing. Collectively, these data suggest that dopamine D1/5 stimulation enhances the mean firing rate of most MS/vDB neurons and also provides a state-dependent bidirectional modulation of theta burst occurrence. Some of these MS/vDB neurons may be cholinergic or GABAergic that may indirectly regulate theta rhythm in the hippocampus.

Original languageEnglish (US)
Pages (from-to)2808-2820
Number of pages13
JournalJournal of Neurophysiology
Volume95
Issue number5
DOIs
StatePublished - May 1 2006

Fingerprint

Dopamine D1 Receptors
Extremities
Neurons
Theta Rhythm
Cholinergic Agents
Tyrosine
Hippocampus
Dopamine
GABAergic Neurons
Ventral Tegmental Area
Urethane
Atropine
Tail
Microscopy
Immunohistochemistry

ASJC Scopus subject areas

  • Neuroscience(all)
  • Physiology

Cite this

Dopamine D1/5 receptor modulation of firing rate and bidirectional theta burst firing in medial septal/vertical limb of diagonal band neurons in vivo. / Fitch, Thomas E.; Sahr, Robert N.; Eastwood, Brian J.; Zhou, Feng C.; Yang, Charles R.

In: Journal of Neurophysiology, Vol. 95, No. 5, 01.05.2006, p. 2808-2820.

Research output: Contribution to journalArticle

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