title: Subfornical organ connections with septal neurons projecting to the median eminence.
abstract: We have examined the effect of electrical stimulation in the subfornical organ (SFO) on the activity of neurons in the medial septum and diagonal band of Broca (MS-DBB) which project to the median eminence in the rat. Previous studies have suggested that septal neurons with such projections are luteinizing hormone releasing hormone neurons. Extracellular single-unit recordings were obtained from 69 neurons in the MS-DBB which were antidromically identified as projecting to the median eminence. Electrical stimulation (100-400 microA) in the SFO resulted in a relatively short-latency (22.8 +/- 0.8 ms), short-duration (9.2 +/- 0.8 ms) activation of 85% of 41 antidromically identified MS-DBB neurons tested. One neuron was inhibited by SFO stimulation, while the remaining 12% were unaffected. Stimulation in nearby regions, including the hippocampal commissure and paraventricular nucleus of the thalamus, failed to elicit a similar excitatory response from 19 identified MS-DBB neurons. These results identify a neuronal pathway between the SFO and septal neurons which project to the median eminence, supporting a possible role for the SFO in the control of luteinizing hormone releasing hormone release and hence gonadotropin secretion.
authors.affiliation: Department of Physiology, Queen's University, Kingston, Ont., Canada.
authors.forename: S D
authors.initials: SD
authors.lastname: Donevan
authors.forename: A V
authors.initials: AV
authors.lastname: Ferguson
mesh_terms: D000200:Action Potentials; D000818:Animals; D004558:Electric Stimulation; D005625:Frontal Lobe / Q000033:anatomy & histology; D008297:Male; D008473:Median Eminence / Q000033:anatomy & histology*; D009474:Neurons / Q000166:cytology* / Q000502:physiology; D009490:Neurosecretory Systems / Q000033:anatomy & histology*; D051381:Rats; D011919:Rats, Inbred Strains; D013356:Subfornical Organ / Q000033:anatomy & histology*