pituitrin and anandamide

The neurohypophyseal hormones oxytocin (OT) and vasopressin (VP) are involved in behavioral, autonomic and neuroendocrine functions. Both peptides are synthesized in magnocellular neurons of paraventricular and supraoptic nuclei at hypothalamic level whose axons terminate in the neurohypophysis (NH), from where OT and VP are released into the systemic circulation. NH contains abundant nitric oxide (NO) synthase suggesting that NO plays a role in the release of these neuropeptides. The endocannabinoid system is present in magnocellular neurons of the hypothalamic neurohypophyseal system, and we have previously demonstrated that endocannabinoids modulate OT secretion at hypothalamic level. In the present work, we investigated the in vitro effect of the endocannabinoid anandamide (AEA) on OT and VP release from NH of untreated adult male rats and the involvement of NO in this action. Our results showed that AEA decreased OT and VP secretion from NH. AEA action was mediated by NO, since the inhibition of NO synthesis completely blocked this inhibitory effect. We found that cannabinoid receptor type 2 (CB2) and transient receptor potential cation channel subfamily V member 1 (TRPV1) are involved in the inhibitory effect of AEA because AM630 and capsazepine, CB2 and TRPV1 antagonists respectively, but not AM251, a CB1 antagonist, blocked AEA effect at neurohypophyseal level. These findings revealed an interaction between endocannabinoid, nitric oxide and oxytocin/vasopressin systems that could be involved in the modulation of homeostatic, behavioral and reproductive processes.

Topics: Animals; Arachidonic Acids; Endocannabinoids; Male; Nitric Oxide; Oxytocin; Pituitary Gland, Posterior; Polyunsaturated Alkamides; Rats; Rats, Sprague-Dawley; Receptors, Cannabinoid; Tissue Culture Techniques; Vasopressins

(1) The aim of the present study was to evaluate the effects of intracerebroventricular administration of anandamide (AEA), an inhibitor of fatty acid amide hydrolase activity (URB597) and a CB1 receptor (CB1 R) antagonist (AM251) on the homeostatic responses elicited by extracellular volume expansion (EVE) in male adult rats. (2) Pretreatment with AEA (100 ng/4 μL) significantly reduced the effect of hypertonic (H-) EVE on plasma concentrations of prolactin (PRL), oxytocin (OT) and corticosterone, but not vasopressin (AVP). Administration of URB597 (20 μg/5 μL) alone significantly reduced PRL, OT, AVP and corticosterone in the H-EVE group. Conversely, URB597 and AEA had no significant effect on basal hormone concentrations. Pretreatment with AM251 (200 ng/2 μL) potentiated OT but did not change AVP plasma levels in the H-EVE group. (3) Hypertonic EVE significantly increased AVP and OT mRNA expression in the supraoptic nucleus (SON), an effect that was blunted in AEA-pretreated rats. Pretreatment with AEA did not change the percentage of vasopressinergic or oxytocinergic neurons colocalizing c-Fos in the SON, but increased nitrate concentrations in the median eminence of animals subjected to H-EVE. (4) The present data suggest that: (i) vasopressinergic and oxytocinergic neurons may be differentially affected by AEA; (ii) activation of CB1 R may restrain the response of the neurohypophyseal system (NHS) to EVE; (iii) the hypothalamic-pituitary-adrenal axis, PRL and the NHS may still be sensitive to AEA after EVE, with these effects probably not dependent on AEA metabolism; and (iv) AEA and nitric oxide could interact in vivo as modulators to directly control stress-induced responses.

Topics: Amidohydrolases; Animals; Arachidonic Acids; Benzamides; Carbamates; Endocannabinoids; Gene Expression Regulation; Infusions, Intraventricular; Male; Median Eminence; Neuroprotective Agents; Nitrates; Oxytocin; Piperidines; Polyunsaturated Alkamides; Pyrazoles; Rats; Rats, Wistar; Receptor, Cannabinoid, CB1; RNA, Messenger; Saline Solution, Hypertonic; Vasopressins

The mechanisms by which cannabinoids alter coronary vascular tone and cardiac performance are controversial. We investigated the effects of various cannabinoids in spontaneously beating Langendorff-perfused rat hearts. Bolus injections of anandamide (0.1-1 micromol) caused no change in coronary flow (CF) or left ventricular systolic pressure (LVSP). In hearts preperfused with vasopressin to induce vasoconstrictor tone, anandamide or the selective CB1 receptor agonist ACEA (1-100 nmol) dose-dependently increased CF by up to 267% and LVSP by 20 mm Hg. The metabolically stable endocannabinoid derivatives, R-methanandamide and noladin ether, displayed similar effects. In contrast, Delta-THC (10-100 nmol), the major psychoactive ingredient of cannabis, strongly decreased CF and LVSP. The CB2 receptor agonist JWH-133 (10-100 nmol) elicited vasodilator and positive inotropic effects only at higher doses. The CB1 antagonists SR141716A and AM-251 as well as the potassium channel inhibitors tetraethylammonium and iberiotoxin blocked the anandamide-induced increases in CF and LVSP, whereas the CB2 antagonist SR144528 and the putative "CB3 antagonist" O-1918 did not have an inhibitory effect. Immunohistochemistry revealed the presence of cardiac CB1 but no CB2 receptors. Anandamide and 2-arachidonoylglycerol were detected in heart tissue. However, combined application of fatty acid amidohydrolase inhibitors and the transport inhibitor AM-404 to augment tissue levels of endocannabinoids was without effect on CF or LVSP. We conclude that in the rat isolated heart with reestablished vasoconstrictor tone, cannabinoids including anandamide elicit coronary vasodilation and a secondary increase in contractility via CB1 receptors and potassium channels.

Topics: Animals; Arachidonic Acids; Cannabinoid Receptor Modulators; Chromatography, Liquid; Coronary Vessels; Dose-Response Relationship, Drug; Endocannabinoids; Female; Glycerides; Heart; Immunochemistry; In Vitro Techniques; Mass Spectrometry; Muscle Tonus; Myocardial Contraction; Myocardium; Polyunsaturated Alkamides; Rats; Rats, Wistar; Receptor, Cannabinoid, CB1; Receptor, Cannabinoid, CB2; TRPV Cation Channels; Vasoconstrictor Agents; Vasodilation; Vasopressins