Effects of Atrial Natriuretic Polypeptide and Angiotensin II on the Supraoptic Neurons in Vitro
Atrial natriuretic polypeptide (ANP) was isolated from atrial tissue and exhibits powerful natriuretic, diuretic and vasodilatory activities. Its sequence has been identified and ANP-immunoreactivity has been localized not only in the atria but also in plasma and within rat hypothalamus (Tanaka et al., 1984) with dense accumulations of immunocytochemical staining in regions of the brain that are important in the control of fluid balance and cardiovascular functions (Kawata et al., 1985). In particular, ANP-immunoreactivity has been located in the anterio-ventral region of the third ventricle (AV3V). The AV3V region and the supraoptic nuclei (SON) contain numerous ANP-binding sites and there may be a functional role for ANP in the control of vasopressin release. Peripheral or central administration of atrial natriuretic factor inhibits the release of arginine vasopressin (AVP) caused by dehydration, haemorrhage and changes in plasma osmolarity (Poole et al., 1987). It is possible that ANP might antagonise the effects of AVP, so the first set of experiments were designed to investigate whether or not ANP could influence directly the activity of neurosecretory cells in the SON. The experiments were carried out in trimmed hypothalamus slice preparations and data compared with the effects of ANP on neurons in the AV3V region (Okuya & Yamashita, 1987).
KeywordsFiring Rate Atrial Natriuretic Peptide Atrial Natriuretic Factor Neurosecretory Cell Supraoptic Nucleus
Unable to display preview. Download preview PDF.
- Abe, H. and Ogata, N., 1982, Ionic mechanism for the osmotically-induced depolarization in neurones of the guinea-pig supraoptic nucleus in vitro, J. Phvsiol., 327: 157.Google Scholar
- Ganten, D., Hutchinson, J.S. and Schelling, P., 1975, The intrinsic brain iso-reninangiotensin system in the rat its possible role in central mechanisms of blodd pressure regulation, Clin. Sci. Mol. Med., 48: 265s.Google Scholar
- Inenaga, K. and Yamashita, H., 1986, Excitation of neurones in the rat paraventricular nucleus in vitro by vasopressiq and oxytocin, J. Phvsiol., 370: 165.Google Scholar
- Kleinert, H.D., Maack, T., Atlas, S.A., Januszewicz, A., Sealey, J.E. and Laragh, J.H., 1984, Atrial natriuretic factor inhibits angiotensin-, norepinephrine-, and potassium-induced vascular contractility, Hypertension, 6:Suppl. 1, 1143.Google Scholar
- Nakamura, M., Katsuura, G., Nakao, K. and Imura, H., 1985, Antidipsogenic action of - human atrial natriuretic polypeptide administered intracerebroventricularly in rats, Neurosci. Lett., 58: 1.Google Scholar
- Okuya, S. and Yamashita, H., 1987, Effects of atrial natriuretic polypeptide on the rat hypothalamic neurones in vitro, J. Phvsiol., 717: 389.Google Scholar
- Phillips, M.I., 1978, Angiotensin in the brain, Neuroendocrinologv, 25:354.Google Scholar
- Tanaka, I., Misono, K.S. and Inagami, T., 1984, Atrial natriuretic factor in rat hypothalamus, atria and plasma: determination by specific radioimmunoassay, Biochem. Biophysical Res. Commun., 124: 663.Google Scholar
- Yamada, T., Nakao, K., Morii, N., Itoh, H., Shiono, S., Sakamoto, M. Sugawara, A., Saito, Y., Ohno, H., Kanai, A., Katsuura, G., Eigyo, M., Matsushita, A., and Imura, H., 1986, Central effect of atrial natriuretic polypeptide on angiotension II-stimulated vasopressin secretion in concious rats, European J. Pharmcol., 125: 453.Google Scholar
- Yamashita, H., Inenaga, K., Kawata, M. and Sano, Y., 1983, Phasically firing neurons in the supraoptic nucleus of the rat hypothalamus: immunocytochemical and electrophysiological studies, Neurosci. Lett., 37: 87.Google Scholar