Streptozotocin-induced diabetes in rats modifies the role D , D and D dopamine receptors play in cardiac sympathetic inhibition.

Background: Diabetes mellitus is associated with abnormalities in peripheral/central catecholaminergic systems, including changes in catecholamine levels and receptor expression.

Objective: Since quinpirole-induced cardiac sympathetic inhibition is greater in diabetic than in normoglycemic rats, this study pharmacologically investigated the dopamine D -like receptor subtypes that mediate cardiac sympathetic inhibition in diabetic (streptozotocin [STZ]-pretreated) pithed rats.

Methods: Fifty male Wistar rats were pretreated with STZ, pithed and conditioned for spinal stimulation (C -T ) of the tachycardic sympathetic tone.

Prospective role of α-adrenoceptor subtypes in the modulation of cardioaccelerator sympathetic tone in an experimental model of diabetes.

Abnormalities in the cardiac sympathetic innervation and tone, as well as in the noradrenergic system are associated, among other peripheral complications, with diabetes mellitus. Furthermore, B-HT 933, an agonist at α-adrenoceptors, induces a greater cardiac sympathetic inhibition in diabetic rats than in normoglycaemic rats. Accordingly, this pharmacological study analysed the specific involvement of the α adrenoceptor subtypes mediating inhibition of the cardioaccelerator sympathetic tone (i.

Blockade of 5-HT receptors with sarpogrelate uncovers 5-HT receptors inhibiting the tachycardic sympathetic drive in pithed rats.

Our group has previously shown in pithed rats that the cardiac sympathetic drive, which produces tachycardic responses, is inhibited by 5-HT via the activation of prejunctional 5-HT receptors. Interestingly, when 5-HT receptors are chronically blocked with sarpogrelate, the additional role of cardiac sympatho-inhibitory 5-HT receptors is unmasked. Although 5-HT receptors mediate tachycardia in rats, and the chronic blockade of 5-HT receptors unmasked 5-HT receptors mediating cardiac vagal inhibition, the role of 5-HT receptors in the modulation of the cardiac sympathetic tone remains virtually unexplored.

Activation of Dopamine D Receptor Subtypes Inhibits the Neurogenic Systemic Vasodilation Induced by Stimulation of the Perivascular CGRPergic Discharge.

The sensory nervous system controls cardiovascular homeostasis via capsaicin-sensitive neurons that release calcitonin gene-related peptide (CGRP), which subsequently activates CGRP receptors. How this perivascular CGRPergic discharge is modulated, nevertheless, remains unclear. In pithed rats, systemic vasodilation induced by CGRPergic discharge stimulation results in diastolic blood pressure (BP) decrements that are inhibited by the dopamine D-like receptor agonist quinpirole.

Differential cardiac sympatho-inhibitory responses produced by the agonists B-HT 933, quinpirole and immepip in normoglycaemic and diabetic pithed rats.

This study compared the cardiac sympatho-inhibitory responses produced by agonists at α -adrenergic (B-HT 933), dopamine D -like (quinpirole) and histamine H /H (immepip) receptors between normoglycaemic and streptozotocin-pretreated (diabetic) pithed rats. Intravenous (i.v.

The role of α- and α-adrenoceptor subtypes in the vasopressor responses induced by dihydroergotamine in ritanserin-pretreated pithed rats.

Background: Dihydroergotamine (DHE) is an acute antimigraine agent that displays affinity for dopamine D-like receptors, serotonin 5-HT receptors and α/α-adrenoceptors. Since activation of vascular α/α-adrenoceptors results in systemic vasopressor responses, the purpose of this study was to investigate the specific role of α- and α-adrenoceptors mediating DHE-induced vasopressor responses using several antagonists for these receptors.

Methods: For this purpose, 135 male Wistar rats were pithed and divided into 35 control and 100 pretreated i.

Pharmacological evidence that histamine H3 receptors inhibit the vasodepressor responses by selective stimulation of the rat perivascular sensory CGRPergic outflow.

This study has investigated whether pharmacological activation of Gi/o coupled histamine H3/H4 receptors inhibits the rat vasodepressor sensory outflow. For this purpose, 100 male Wistar rats were pithed, artificially ventilated and pretreated (i.v.

Specific role of α2A - and α2B -, but not α2C -, adrenoceptor subtypes in the inhibition of the vasopressor sympathetic out-flow in diabetic pithed rats.

Several lines of evidence have shown an association of diabetes with a catecholamines' aberrant homeostasis involving a drastic change in the expression of adrenoceptors. This homeostatic alteration includes, among other things, atypical actions of α2 -adrenoceptor agonists within central and peripheral α2 -adrenoceptors (e.g.

Role of pre-junctional CB1, but not CB2 , TRPV1 or GPR55 receptors in anandamide-induced inhibition of the vasodepressor sensory CGRPergic outflow in pithed rats.

Stimulation of the perivascular sensory outflow in pithed rats produces vasodepressor responses mediated by CGRP release. Interestingly, endocannabinoids such as anandamide (which interacts with CB1 , CB2 , TRPV1 and GPR55 receptors) can regulate the activity of perivascular sensory nerves in dural blood vessels by modulating CGRP release. Yet, as no publication has reported whether this mechanism is operative in the healthy systemic vasculature, this study has specifically analysed the receptors mediating the potential inhibitory effects of the cannabinoid (CB) receptor agonists anandamide (non-selective), JWH-015 (CB2 ) and lysophosphatidylinositol (GPR55) on the rat vasodepressor sensory CGRPergic outflow (an index of systemic vasodilatation).

Analysis of anandamide- and lysophosphatidylinositol-induced inhibition of the vasopressor responses produced by sympathetic stimulation or noradrenaline in pithed rats.

The endocannabinoid system exhibits multiple functions in cardiovascular regulation mainly by cannabinoid (CB1 and CB2) receptors, vanilloid TRPV1 receptors and, probably, by the orphan G protein-coupled receptor 55 (GPR55). Hence, the role of these receptors was investigated in Wistar pithed rats on anandamide- and lysophosphatidylinositol (LPI)-induced inhibition of the vasopressor responses induced by preganglionic (T7-T9) stimulation of the vasopressor sympathetic outflow or i.v.

The role of pre-junctional D2 -like receptors mediating quinpirole-induced inhibition of the vasodepressor sensory CGRPergic out-flow in pithed rats.

Calcitonin gene-related peptide (CGRP) released from perivascular sensory nerves plays a role in the regulation of vascular tone. Indeed, electrical stimulation of the perivascular sensory out-flow in pithed rats produces vasodepressor responses, which are mainly mediated by CGRP release. This study investigated the potential role of dopamine D1 -like and D2 -like receptors in the inhibition of these vasodepressor responses.

Predominant role of the dopamine D3 receptor subtype for mediating the quinpirole-induced inhibition of the vasopressor sympathetic outflow in pithed rats.

We have recently reported that quinpirole (a D2-like receptor agonist) inhibits the vasopressor sympathetic outflow in pithed rats via sympatho-inhibitory D2-like receptors. Since D2-like receptors consist of D2, D3 and D4 receptor subtypes, this study investigated whether these subtypes are involved in the above quinpirole-induced sympatho-inhibition by using antagonists of these receptor subtypes. One hundred fifty-six male Wistar rats were pithed and prepared for preganglionic spinal (T7-T9) stimulation of the vasopressor sympathetic outflow.

Intrathecal dihydroergotamine inhibits capsaicin-induced vasodilatation in the canine external carotid circulation via GR127935- and rauwolscine-sensitive receptors.

It has been suggested that during a migraine attack trigeminal nerves release calcitonin gene-related peptide (CGRP), producing central nociception and vasodilatation of cranial arteries, including the extracranial branches of the external carotid artery. Since trigeminal inhibition may prevent this vasodilatation, the present study has investigated the effects of intrathecal dihydroergotamine on the external carotid vasodilatation to capsaicin, α-CGRP and acetylcholine. Anaesthetized vagosympathectomized dogs were prepared to measure blood pressure, heart rate and external carotid conductance.