Increases in cerebral blood flow in rat hippocampus after medial septal injection of naloxone.

Abstract

Background and Purpose:In a previous study, we occasionally found that the rat given naloxone in the preoptic region develops behavioral seizures. In view of knowledge that the forebrain including the medial septal nucleus provides cholinergic projections to the hippocampal formation, the present study examined the effects of naloxone injected into the medial septal nucleus on the local blood flow in the hippocampus.Methods: A polyurethane-coated platinum electrode with a l-mm bare tip for measurement of blood flow and a guide cannula made of stainless steel tube for naloxone injection were implanted chronically into the brain. The cerebral blood flow was measured by the hydrogen clearance method in freely moving rats.Results: The injection of 50 fig naloxone caused a significant increase in hippocampal blood flow, with its peak at 20 minutes. Twenty micrograms naloxone caused a similar increase, but 10 ju.g caused only a slight increase that peaked at 30 minutes, suggesting a dose-response of naloxone effect. Hippocampal blood flow was not changed after the injection of saline into the medial septal nucleus and after the injection of naloxone into the caudate nucleus.Conclusions: Taken together with previous findings, the results suggest that endogenous opioids exert a decreasing effect on the local blood flow in the hippocampus, probably mediated by the magnocellular cholinergic neurons projecting to the hippocampus. (Stroke 1992;23:1325-1330 KEY WORDS • cerebral blood flow • hippocampus • rats • naloxone

Cholinergic Modulation of Glial Function During Aging and Chronic Neuroinflammation

“…In return, this hypoperfusion could lead to the death of even more cholinergic neurons as the cholinergic neurons are energy-deprived. In rats, cholinergic inputs from the BF are responsible for increasing cerebral blood flow in the hippocampus (Nishimura et al, 1992;Sato et al, 2004); this can be impaired by limited NO production via a decrease of neuronal NO-synthase catalytic activity (Hartlage-Rübsamen and Schliebs, 2001). In humans, it has been shown that greater blood flow into the hippocampus is correlated with a better performance in spatial memory in older adults (Heo et al, 2010) and a greater hippocampal vascular reserve might be a protective factor against cognitive loss (Perosa et al, 2020).…”

Effects of CRH and LHRH on Rat Septo-Hippocampal Neurons.

“…It has also been shown that among neurons located in the septum those projecting to the hippocampus have receptors for other substances such as monoamine [31,32], GABA [32][33][34][35], substance P [32] and opioid peptides [36,37]. All of these substances modified the activity of septo-hippocampal neurons.…”