Muscarinic Mobilization of Choline in Rat Brain In Vivo as Shown by the Cerebral Arterio‐Venous Difference of Choline

Abstract

In anesthetized rats, the choline levels of cerebrospinal fluid and plasma obtained from blood collected from peripheral vessels (carotid artery, cardiac vessels) and from the transverse sinus were determined with a radioenzymatic assay. Cortical release of choline was studied using the "cup technique." The plasma choline level of the peripheral blood (11.5 mumol/L) was lower than that of the sinus blood. The resulting cerebral arterio-venous difference of choline was negative (3.2 mumol/L) and reflected the net release of choline from the whole brain. The plasma choline levels were not different irrespective of whether the rats were anesthetized with ether, urethane, or pentobarbital. However, the choline level of the cerebrospinal fluid, which normally was lower than the plasma choline levels, was increased by urethane anesthesia to a level between the arterial and venous plasma concentrations of the brain. In old rats (24 months), the choline level of the cerebrospinal fluid was significantly lowered, when compared with the results obtained with younger rats (2-4 months). In rats kept on a low-choline diet for 2 weeks, the plasma choline level of the peripheral blood was reduced to 51% of the control. The effect on the choline level of the sinus blood was smaller; the cerebral arterio-venous difference of choline was not reduced (it was even slightly enhanced). Likewise, the choline level of the cerebrospinal fluid and the cortical release of choline were not altered. Intraperitoneal administration of oxotremorine in pentobarbital-anesthetized rats kept on a low-choline diet increased the plasma levels of choline.(ABSTRACT TRUNCATED AT 250 WORDS)

Small Rises in Plasma Choline Reverse the Negative Arteriovenous Difference of Brain Choline

“…All animals were anesthetized with pentobarbitone (40-80 mg/kg i.p. ), and blood was withdrawn from a peripheral artery (a. femoralis) and from the transverse sinus which was exposed by trepanation of the skull fixed in a head holder (Brehm et al, 1987).…”

Role of Phospholipase D Activation in Nervous System Physiology and Pathophysiology

“…Several neurotransmitters could be involved in receptor-mediated choline mobilization, the most obvi- ous being ACh itself. Early investigations (Corradetti et al, 1983 ;Brehm et al, 1987) have shown that muscarinic agonists enhance the release of choline from bound stores into the extracellular fluid of the brain in vivo. From these studies, the hypothesis was proposed that ACh is capable of mobilizing from bound stores its own precursor, choline, in order to facilitate ACh resynthesis (L6ffelholz, 1987 ; Fig .…”

Decrease of Acetylcholine Release from Cortical Slices in Aged Rats: Investigations into Its Reversal by Phosphatidylserine

“…The main sources of Ch for ACh synthesis are represented by free Ch from the blood, Ch phospholipids, and extracellular hydrolysis of ACh released at the cholinergic synapses (TuZek, 1985). A decrease in Ch concentration in the cerebro-spinal fluid (Brehm et al, 1987) and of Ch transport through the blood-brain barrier (Mooradian, 1988) has been demonstrated in aging rats, suggesting reduced Ch availability. Acceleration of Ch phospholipid hydrolysis with free Ch formation in response to protein kinase C activation has been repeatedly demonstrated (Loeffelholz, 1989).…”