Changes in nerve- and endothelium-mediated contractile tone of the corpus cavernosum in a mouse model of pre-mature ageing

The Acute Effects and Mechanism of Ketamine on Nicotine-Induced Neurogenic Relaxation of the Corpus Cavernosum in Mice

The present study aimed to investigate the acute effects and the mechanism of ketamine on nicotine-induced relaxation of the corpus cavernosum (CC) in mice. This study measured the intra-cavernosal pressure (ICP) of male C57BL/6 mice and the CC muscle activities using an organ bath wire myograph. Various drugs were used to investigate the mechanism of ketamine on nicotine-induced relaxation. Direct ketamine injection into the major pelvic ganglion (MPG) inhibited MPG-induced increases in ICP. D-serine/L-glutamate-induced relaxation of the CC was inhibited by MK-801 (N-methyl-D-aspartate (NMDA) receptor inhibitor), and nicotine-induced relaxation was enhanced by D-serine/L-glutamate. NMDA had no effect on CC relaxation. Nicotine-induced relaxation of the CC was suppressed by mecamylamine (a non-selective nicotinic acetylcholine receptor antagonist), lidocaine, guanethidine (an adrenergic neuronal blocker), N^w-nitro-L-arginine (a non-selective nitric oxide synthase inhibitor), MK-801, and ketamine. This relaxation was almost completely inhibited in CC strips pretreated with 6-hydroxydopamine (a neurotoxic synthetic organic compound). Ketamine inhibited cavernosal nerve neurotransmission via direct action on the ganglion and impaired nicotine-induced CC relaxation. The relaxation of the CC was dependent on the interaction of the sympathetic and parasympathetic nerves, which may be mediated by the NMDA receptor.

D-(+)-Galactose-induced aging: A novel experimental model of erectile dysfunction

Erectile dysfunction (ED) is defined as the inability to achieve and/or maintain penile erection sufficient for satisfactory sexual relations, and aging is one of the main risk factors involved. The D-(+)-Galactose aging model is a consolidated methodology for studies of cardiovascular aging; however, its potential for use with ED remain unexplored. The present study proposed to characterize a new experimental model for ED, using the D-(+)-Galactose aging model. For the experiments, the animals were randomly divided into three groups receiving: vehicle (CTL), D-galactose 150 mg/kg (DGAL), and D-(+)-galactose 150 mg/Kg + sildenafil 1.5 mg/Kg (DGAL+SD1.5) being administered daily for a period of eight weeks. All of the experimental protocols were previously approved by the Ethics Committee on the Use of Animals at the Federal University of Paraíba n° 9706070319. During the treatment, we analyzed physical, molecular, and physiological aspects related to the aging process and implicated in the development of ED. Our findings demonstrate for the first time that D-(+)-Galactose-induced aging represents a suitable experimental model for ED assessment. This was evidenced by an observed hyper-contractility in corpora cavernosa, significant endothelial dysfunction, increased ROS levels, an increase in cavernous tissue senescence, and the loss of essential penile erectile components.

Nitrergic perivascular innervation in health and diseases: Focus on vascular tone regulation

For a long time, the vascular tone was considered to be regulated exclusively by tonic innervation of vasoconstrictor adrenergic nerves. However, accumulating experimental evidence has revealed the existence of nerves mediating vasodilatation, including perivascular nitrergic nerves (PNN), in a wide variety of mammalian species. Functioning of nitrergic vasodilator nerves is evidenced in several territories, including cerebral, mesenteric, pulmonary, renal, penile, uterine and cutaneous arteries. Nitric oxide (NO) is the main neurogenic vasodilator in cerebral arteries and acts as a counter-regulatory mechanism for adrenergic vasoconstriction in other vascular territories. In the penis, NO relaxes the vascular and cavernous smooth muscles leading to penile erection. Furthermore, when interacting with other perivascular nerves, NO can act as a neuromodulator. PNN dysfunction is involved in the genesis and maintenance of vascular disorders associated with arterial and portal hypertension, diabetes, ageing, obesity, cirrhosis and hormonal changes. For example defective nitrergic function contributes to enhanced sympathetic neurotransmission, vasoconstriction and blood pressure in some animal models of hypertension. In diabetic animals and humans, dysfunctional nitrergic neurotransmission in the corpus cavernosum is associated with erectile dysfunction. However, in some vascular beds of hypertensive and diabetic animals, an increased PNN function has been described as a compensatory mechanism to the increased vascular resistance. The present review summarizes current understanding on the role of PNN in control of vascular tone, its alterations under different conditions and the associated mechanisms. The knowledge of these changes can serve to better understand the mechanisms involved in these disorders and help in planning new treatments.