Medullary inputs to nucleus accumbens neurons

Area of Science:

• Neuroscience
• Cardiovascular Physiology
• Autonomic Nervous System Research

Background:

• The nucleus accumbens (NA) plays a crucial role in reward and motivation.
• The nucleus of the solitary tract (NTS) and ventrolateral medulla (VLM) are key brainstem regions involved in autonomic and cardiovascular regulation.
• Understanding how these systems interact is vital for comprehending motivated behaviors and physiological control.

Purpose of the Study:

• To investigate the effects of stimulating the NTS and VLM on the activity of NA neurons.
• To examine the response of NA neurons to arterial baroreceptor activation.
• To determine if visceral and cardiovascular afferent inputs converge on NA neurons.

Main Methods:

• Extracellular single-unit recordings were performed in alpha-chloralose-anesthetized rats.
• Electrical or glutamate stimulation was used to activate the NTS and VLM.
• Arterial baroreceptors were activated by phenylephrine injection to induce hypertension.
• Cochleate chloride (CoCl2) injections were used to assess the independence of NTS and VLM pathways.

Main Results:

• Stimulation of the NTS excited 48% and inhibited 10% of NA units; VLM stimulation excited 24.7% and inhibited 7.2%.
• 22% of units responded to stimulation of both NTS and VLM, with simultaneous stimulation potentiating responses.
• Some units activated by NTS/VLM stimulation also showed increased firing during baroreceptor activation, and these were located in the NA shell.
• NTS or VLM stimulation effects on NA neurons were independent of the other pathway.

Conclusions:

• Afferent inputs from the NTS and VLM converge on NA neurons.
• Visceral and cardiovascular afferent signals likely influence the output of neurons in the shell region of the NA.
• These findings suggest a mechanism by which physiological states can modulate motivated behaviors.