ABSTRACT
AIM: To investigate the primary electrophysiological and pharmacological properties of the nucleus basalis magnocellularis (nbM) neurons. METHODS: Single unit extracellular recordings from the nbM neurons were obtained with glass micropipettes in urethane-anesthetized rats. RESULTS: Most nbM neurons responded to noxious but not innocuous mechanical, thermal, chemical, and electrical stimuli. The receptive fields were usually very large and bilateral. Electrical stimulation applied to the frontal cortex (FCX) either activated orthodromically or antidromically the nbM neurons. The FCX stimulation-induced excitatory response in the nbM neurons could be partly blocked by intracerebroventricular (icv) injection of atropine 2.5 mmol/L or tubocurarine 0.1 mmol/L. Icv injection of ach (1, 10, and 100 mmol/L) dose-dependently increased the spontaneous firing rate in most of the nbM neurons. Atropine (2.5, 25, and 250 mmol/L) or tubocurarine (0.1, 1, and 10 mmol/L) not only antagonized the ACh-induced excitation, but also inhibited the spontaneous firing of the nbM neurons. CONCLUSION: The nbM might be involved in nociception, although it was considered to play a critical role in cognitive function. Also, the nbM appears to be rich in cholinergic autoreceptors.
Subject(s)
Acetylcholine/pharmacology , Basal Nucleus of Meynert/physiology , Frontal Lobe/physiology , Receptors, Cholinergic/drug effects , Animals , Atropine/pharmacology , Basal Nucleus of Meynert/drug effects , Cholinergic Agents/pharmacology , Electric Stimulation , Evoked Potentials/drug effects , Male , Neurons/drug effects , Neurons/physiology , Rats , Rats, Sprague-Dawley , Tubocurarine/pharmacologyABSTRACT
The present study investigated the age-related alterations in responses of the nucleus basalis magnocellularis (nbM) neurons to frontal cortex (FCX) stimulation. Single unit extracellular recording from the nbM neurons were obtained with glass micropipettes in urethane-anesthetized rats. A total of 137 units were located within the nbM in the three age groups (young, 3 months; adult, 12 months; old, 24 months). FCX stimulation elicited responses in 91% of the 137 neurons. Most of them were excited. The frequency of occurrence of excitatory responses in the nbM neurons was decreased with aging. The thresholds and latencies of excitatory responses evoked by FCX stimulation were increased in old rats. The mean peak-firing rate of exciting phase was gradually reduced with aging. These findings indicate that there might be some functional changes in the nbM neurons with aging.
