Lactate inhibited sodium intake in dehydrated rats

Area of Science:

• Neuroscience
• Physiology
• Cell Biology

Background:

• Glial cells, particularly astrocytes, are implicated in regulating body fluid balance.
• Astrocytic Na_x channels and lactate production are activated by increased sodium levels.
• Lactate and hypertonic sodium solutions may influence central salt appetite pathways via GABAergic neurons.

Purpose of the Study:

• To investigate the role of lactate in regulating sodium and water intake during dehydration.
• To differentiate the effects of lactate on thirst versus sodium appetite mechanisms.

Main Methods:

• Rats underwent water deprivation (WD) followed by partial rehydration (WD-PR).
• Intracerebroventricular microinjections of l-lactate or α-cyano-4-hydroxycinnamic acid (α-CHCA, a lactate transporter inhibitor) were administered.
• Water and 0.3 M NaCl intake were measured over 2 hours.

Main Results:

• Central α-CHCA administration increased sodium preference in dehydrated rats.
• Central lactate administration enhanced water intake but decreased sodium intake in partially rehydrated rats.
• Inhibition of lactate transport did not alter water or sodium intake in partially rehydrated rats.

Conclusions:

• Lactate appears to be involved in inhibitory mechanisms that reduce sodium intake in dehydrated rats.
• These findings highlight lactate's complex role in the physiological responses to dehydration and fluid imbalance.