Exploring the role of neuropeptides and their effects on sperm function

Tomova, Ana-Maria (2016) Exploring the role of neuropeptides and their effects on sperm function. Masters by Research thesis (MSc), Manchester Metropolitan University.

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Abstract

Neuropeptides are small peptides that act as signalling molecules. These have a wide range of important roles in numerous physiological, metabolic and behaviour functions. For example, oxytocin and vasopressin have essential roles in salt balance, social behaviour, and stress regulation. The role of neuropeptides in reproduction is well documented: it has been demonstrated they are involved in sexual behaviour, maternal-infant bonding, pair-bonding, lactation, pregnancy, penile erection, ejaculation, uterus contraction, and sperm transfer. The receptors for neuropeptides are found throughout both the male and female reproductive tracts. Several neuropeptides are found in both seminal plasma and follicular fluid indicating some involvement directly in fertilisation. Neuropeptide levels are altered in mood disorders and these altered levels could potentially have implications in infertility. However, very little is currently known about the effects of neuropeptides on sperm function, this study explored this area further. Considering the overarching link that neuropeptides have between pair bonding, mental health and fertility it was hypothesised that any perturbations in their action may impede successful reproduction. This study investigated how neuropeptides could regulate sperm function. These data may lead to future therapies in assisted reproduction. Semen samples were produced by masturbation, separated from the seminal plasma and probed for neuropeptide receptors via immunocytochemistry. This is the first time, to knowledge, that vasopressin receptor 2 has been localised on human sperm. As no other receptors were localised this study focused on any effect vasopressin may have on sperm function by incubation with a vasopressin agonist and measuring any modulations in motility and PKA phosphorylation activity. No significant differences were found in motility or PKA phosphorylation activity in sperm treated with vasopressin agonist, further optimisation of the assays is required.