Summary
Twenty-three neurons in the region of the subfornical organ (SFO) were antidromically activated by electrical stimulation of the hypothalamic paraventricular nucleus (PVN) in male rats under urethane anesthesia. Microiontophoretically (MIPh) applied angiotensin II (AII) excited the activity of all units in the region of the SFO and the effect of AII was blocked by MIPh applied saralasin (Sar), an AII antagonist, but not by atropine (Atr), a muscarinic antagonist. In these units, 12 were also excited by MIPh applied acetylcholine (ACh) while 11 were not affected and the effect of ACh was attenuated by not only MIPh applied Atr, but also Sar, suggesting that not only neurons specific for AII, but also neurons sensitive to both AII and ACh project to the PVN in the region of the SFO. Intravenously administered AII excited the activity of both types of units in the region of the SFO. Microinjected AII or ACh into the region of the SFO excited the activity of putative vasopressin (VP)-secreting units in the PVN. These results suggest that neurons projecting to the PVN in the region of the SFO may act to enhance the activity of putative VP-secreting neurons in the PVN in response to circulating AII.
Similar content being viewed by others
References
Brimble MJ, Dyball REJ, Forsling ML (1978) Oxytocin release following osmotic activation of oxytocin neurones in the paraventricular and supraoptic nuclei. J Physiol (Lond) 278: 69–78
Broadwell RD, Brightman MW (1976) Entry of peroxidase into neurons of the central and peripheral neurons system from extracerebral and cerebral blood. J Comp Neurol 166: 257–284
Dellmann HD, Simpson JB (1979) The subfornical organ. Int Rev Cytol 58: 333–421
Eng R, Miselis RR (1981) Polydipsia and abolition of angiotensininduced drinking after transections of subfornical organ efferent projection in the rat. Brain Res 255: 200–206
Felix D, Akert K (1974) The effect of angiotensin II on neurones of the cat subfornical organ. Brain Res 76: 350–353
Ferguson AV, Day TA, Renaud LP (1984a) Subfornical organ efferents influence the excitability of neurohypophyseal and tuberoinfundibular paraventricular nucleus neurons in the rat. Neuroendocrinology 39: 423–428
Ferguson AV, Day TA, Renaud LP (1984b) Subfornical organ stimulation excites paraventricular neurons projecting to dorsal medulla. Am J Physiol 247: R1088-R1092
Ferguson AV, Renaud LP (1984) Hypothalamic paraventricular nucleus lesions decrease pressor responses to subfornical organ stimulation. Brain Res 305: 361–364
Hayward JN (1977) Functional and morphological aspects of hypothalamic neurons. Physiol Rev 57: 574–658
Iovino M, Steardo L (1984) Vasopressin release to central and peripheral angiotensin II in rats with lesions of the subfornical organ. Brain Res 322: 365–368
Ishibashi S, Nicolaidis S (1981) Hypertension induced by electrical stimulation of the subfornical organ (SFO). Brain Res Bull 6: 135–139
Knepel W, Nutto D, Meyer DK (1982) Effect of transection of subfornical organ efferent projections on vasopressin release induced by angiotensin or isoprenaline in the rat. Brain Res 248: 180–184
Lind RW, Johnson AK (1982) Subfornical organ-median preoptic connections and drinking and pressor responses to angiotensin II. J Neurosci 2: 1043–1051
Lind RW, Swanson LW, Ganten D (1984) Angiotensin II immunoreactivity in neural afferents and efferents of the subfornical organ of the rat. Brain Res 321: 209–215
Lind RW, Swanson LW, Ganten D (1985) Organization of angiotensin II immunoreactive cells and fibers in the rat central nervous system. Neuroendocrinology 40: 2–24
Lind RW, Van Hoesen GW, Johnson AK (1982) An HRP study of the connections of the subfornical organ of the rat. J Comp Neurol 210: 265–277
Mangiapane ML, Simpson JB (1980a) Subfornical organ: forebrain site of pressor and dipsogenic action of angiotensin II. Am J Physiol 239: R382-R389
Mangiapane ML, Simpson JB (1980b) Subfornical organ lesions reduce the pressor effect of systemic angiotensin II. Neuroendocrinology 31: 380–384
Mangiapane ML, Simpson JB (1983) Drinking and pressor responses after acetylcholine injection into subfornical organ. Am J Physiol 244: R508-R513
Mangiapane ML, Thracher TN, Keil LC, Simpson JB, Ganong WF (1982) Subfornical organ lesions impair the vasopressin (AVP) response to hyperosmolality or angiotensin II (AII). Fed Proc 41: 1105
Miselis RR (1981) The efferent projections of the subfornical organ of the rat: a circumventricular organ within a neural network subserving water balance. Brain Res 230: 1–23
Mitchell LD, Barron K, Brody MJ, Johnson AK (1982) Two possible actions for circulating angiotensin II in the control of vasopressin release. Peptides 3: 503–507
Paxinos G, Watson C (1982) The rat brain in stereotaxic coordinates. Academic Press, New York
Phillips MI, Felix D (1976) Specific angiotensin II receptive neurons in the cat subfornical organ. Brain Res 109: 531–540
Poulain DA, Wakerley JB (1982) Electrophysiology of hypothalamic magnocellular neurones secreting oxytocin and vasopressin. Neuroscience 7: 773–808
Sgro S, Ferguson AV, Renaud LP (1984) Subfornical organsupraoptic nucleus connections: an electrophysiologic study in the rat. Brain Res 303: 7–13
Silverman AJ, Hoffman DL, Zimmerman EA (1981) The descending afferent connections of the paraventricular nucleus of the hypothalamus (PVN). Brain Res Bull 6: 47–61
Simpson JB, Reed M, Keil LC, Thrasher TN, Ramsay DJ (1979) Forebrain analysis of vasopressin (AVP) secretion and water intake induced by angiotensin II (AII). Fed Proc 38: 982
Simpson JB, Routtenberg A (1972) The subfornical organ and carbachol-induced drinking. Brain Res 45: 135–152
Simpson JB, Routtenberg A (1974) Subfornical organ: acetylcholine application elicits drinking. Brain Res 79: 157–164
Simpson JB, Routtenberg A (1978) Subfornical organ: a dipsogenic site of action of angiotensin II. Science 201: 379–380
Summerlee AJS (1981) Extracellular recordings from oxytocin neurons during the expulsive phase of birth in unanaesthetized rat. J Physiol (Lond) 321: 1–9
Swanson LW, Sawchenko PE (1983) Hypothalamic integration: organization of the paraventricular and supraoptic nuclei. Ann Rev Neurosci 6: 269–324
Tanaka J, Kaba H, Saito H, Seto K (1985) Electrophysiological evidence that circulating angiotensin II sensitive neurons in the subfornical organ alter the activity of hypothalamic paraventricular neurohypophyseal neurons in the rat. Brain Res 342: 361–365
Thrasher TN, Simpson JB, Ramsey DJ (1982) Lesions of the subfornical organ blocked angiotensin-induced drinking in the dog. Neuroendocrinology 35: 68–72
Wakerley JB, Lincoln DW (1971) Phasic discharge of antidromically identified units in the paraventricular nucleus of the hypothalamus. Brain Res 25: 192–194
Wakerley JB, Poulain DA, Dyball REJ, Cross BA (1975) Activity of phasic neurosecretory cells during haemorrhage. Nature (Lond) 285: 82–84
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Tanaka, J., Kaba, H., Saito, H. et al. Efferent pathways from the region of the subfornical organ to hypothalamic paraventricular nucleus: an electrophysiological study in the rat. Exp Brain Res 62, 509–514 (1986). https://doi.org/10.1007/BF00236029
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00236029