Abstract
Reptiles are the first amniotes to develop an intromitent penis, however until now the mechanisms involved in the electrical field stimulation-induced contraction on corpora cavernosa isolated from Crotalus durissus terrificus were not investigated. Crotalus and rabbit corpora cavernosa were mounted in 10 mL organ baths for isometric tension recording. Electrical field stimulation (EFS)-induced contractions were performed in presence/absence of phentolamine (10 μM), guanethidine (30 μM), tetrodotoxin (1 μM and 1mM), A-803467 (10 μM), 3-iodo-L-Tyrosine (1 mM), salsolinol (3 μM) and a modified Krebs solution (equimolar substitution of NaCl by N-methyl–D-glucamine). Immuno-histochemistry for tyrosine hydroxylase was also performed. Electrical field stimulation (EFS; 8 Hz and 16 Hz) caused contractions in both Crotalus and rabbit corpora cavernosa. The contractions were abolished by previous incubation with either phentolamine or guanethidine. Tetrodotoxin (1 μM) also abolished the EFS-induced contractions of rabbit CC, but did not affect EFS-induced contractions of Crotalus CC. Addition of A-803467 (10 μM) did not change the EFS-induced contractions of Crotalus CC but abolished rabbit CC contractions. 3-iodo-L-Tyrosine and salsolinol had no effect on EFS-induced contractions of Crotalus CC and Rabbit CC. Replacement of NaCl by N- Methyl-D-glucamine (NMDG) abolished EFS-induced contractions of rabbit CC, but did not affect Crotalus CC. The presence of tyrosine hydroxylase was identified in endothelial cells only of Crotalus CC. Since the EFS-induced contractions of Crotalus CC is dependent on catecholamine release, insensitive to TTX, insensitive to A803467 and to NaCl replacement, it indicates that the source of cathecolamine is unlikely to be from adrenergic terminals. The finding that tyrosine hydroxylase is present in endothelial cells suggests that these cells can modulate Crotalus CC tone.
Highlights
Penile erection is a neurovascular event dependent on cavernosal smooth muscle relaxation and elevation of local flux of blood [1,2]
In Crotalus corpus cavernosum (CCC), the Electrical field stimulation (EFS)-induced relaxation is not affected by TTX [10], indicating the possible presence of a TTXinsensitive sodium channel
Similar results were obtained with another tyrosine hydroxylase inhibitor, 3-iodo-Ltyrosine (1 mM) in CCC (10.03 ± 2.62 mN; 11.49 ± 4.18 mN for 8 Hz and 15.26 ± 3.53 mN; 15.4 ± 6.6 mN for 16 Hz; n = 4) and in rabbit corpora cavernosa (RbCC) (1.63 ± 0.22 mN; 2.84 ± 0.55 mN for 8 Hz; 3.01 ± 0.44 mN; 5.26 ± 0.35 for 16 Hz; n = 3)
Summary
Penile erection is a neurovascular event dependent on cavernosal smooth muscle relaxation and elevation of local flux of blood [1,2]. The main physiological component involved in the detumescent state is the liberation of catecholamine by adrenergic nerves, inducing cavernosal muscle contraction. Nitric oxide (NO) is the major component responsible for initiating and maintaining the tumescent state, by promoting cavernosal smooth muscle relaxation [3,4,5]. Sodium voltage-gated channels (VGSC) are important ion channels involved in nerve depolarization [6]. Treatment with tetrodotoxin (TTX) or other inhibitors of VGSC abolishes the nitrergic relaxation induced by electrical field stimulation (EFS) in rabbit, monkey and human corpora cavernosa preparations [7,8,9]. In Crotalus corpus cavernosum (CCC), the EFS-induced relaxation is not affected by TTX [10], indicating the possible presence of a TTXinsensitive sodium channel. The purpose of this study was to characterize the transmural EFSinduced contractions in CCC
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