The effects of median raphé electrical stimulation on serotonin release in the dorsal hippocampal formation of prenatally protein malnourished rats.
Our previous work had shown an enhanced inhibition in the hippocampal formation of prenatally protein malnourished rats. We have also found a diminishment in 5-hydroxytryptamine (5-HT) fibers in the hippocampal formation of malnourished rats as well as increased levels of 5-HT in the brain. The purpose of the present study was to determine 5-HT release in the dorsal hippocampal formation following electrical stimulation of the median raphé nucleus (MRN) in unanesthetized prenatally malnourished rats. Stimulation of this nucleus at 20 Hz in malnourished rats resulted in a significantly diminished release of 5-HT compared to well-nourished rats. The latter group showed a lesser, though still significant, decrease in 5-HT release following raphé stimulation. Basal release of 5-HT prior to stimulation was significantly higher in malnourished rats as compared to well-nourished controls. This may be the result of a decreased density of 5-HT neurons leading to a diminished control of release. Stimulation of the MRN in behaving malnourished animals may markedly affect the recurrent negative feedback collaterals onto somatodendritic 5-HT(1A) and 5-HT(1D) autoreceptors thus enhancing the inhibitory effects of stimulation of the median raphé on 5-HT release. Studies are underway to examine the sensitivity of both the somatodendritic and terminal 5-HT autoreceptors in malnourished animals, in order to understand possible mechanisms for our findings.
Mokler
D J
DJ
Department of Pharmacology, College of Osteopathic Medicine, University of New England, Biddeford, ME 04005, USA. dmokler@mailbox.une.edu
Bronzino
J D
JD
Galler
J R
JR
Morgane
P J
PJ
D000704:Analysis of Variance; D000818:Animals; D004558:Electric Stimulation; D005260:Female; D006624:Hippocampus / Q000378:metabolism*; D008297:Male; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects; D011502:Protein-Energy Malnutrition; D011903:Raphe Nuclei / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012701:Serotonin / Q000378:metabolism*
D012701:Serotonin