Abstract
We investigated the effects of sexual arousal induced by olfactory stimuli on the expression of neuromodulators, neurotransmitters and sexual steroid receptors in the suprachiasmatic nucleus (SCN, the circadian pacemaker of mammals) and other cerebral entities of Syrian hamsters (Mesocricetus auratus) compared to manual sleep deprivation and immobilization stress. The hamsters kept under a 12:12 hours (h) light:dark cycle were deprived of sleep by sexual stimulation, gentle manual handling or immobilization stress for 1 h at the beginning of the light phase and subsequently sacrificed at zeitgeber time 01:00, respectively; for comparison, hamsters were manually sleep deprived for 6 or 20 h or sacrificed after completing a full sleep phase. As demonstrated by immunohistochemistry, apart from various alterations after manual sleep deprivation, sexual stimulation caused down-regulation of arginine-vasopressin (AVP), vasointestinal peptide (VIP), serotonin (5-HT), substance P (SP), and met-enkephalin (ME) in the SCN. Somatostatin (SOM) was diminished in the medial periventricular nucleus (MPVN). In contrast, an increase in AVP was observed in the PVN, that of oxytocin (OXY) in the supraoptic nucleus (SON), of tyrosine-hydroxylase (TH) in the infundibular nucleus (IN), and dopamine beta-hydroxylase (DBH) in the A7 neuron population of the brain stem (A7), respectively. Testosterone in plasma was increased. The results indicate that sexual arousal extensively influences the neuropeptide systems of the SCN, suggesting an involvement of the SCN in reproductive behavior.
Highlights
IntroductionDifferent modulator and transmitter systems of various hypothalamic nuclei are involved in sexual control: arginine-vasopressin (AVP), dopamine, oxytocin (OXY), and substance P (SP) next to sexual steroids facilitate sexual behavior [1,2,3,4,5], whereas neuropeptide Y (NP Y), somatostatin (SOM), endogenous opioids such as met-enkephalin (ME), serotonin (5-HT = 5-hydroxy-tryptamin) and gamma-amino butyric acid (GABA) express inhibitory influences on sexual activity [6,7,8,9,10]
The observations during the pre-tests verified that the diurnal sleep phase started at the end of the dark period shortly before ZT 00:00
This main diurnal sleep phase continued for 4–6 h, obvious arousal reactions were not observed
Summary
Different modulator and transmitter systems of various hypothalamic nuclei are involved in sexual control: arginine-vasopressin (AVP), dopamine, oxytocin (OXY), and substance P (SP) next to sexual steroids facilitate sexual behavior [1,2,3,4,5], whereas neuropeptide Y (NP Y), somatostatin (SOM), endogenous opioids such as met-enkephalin (ME), serotonin (5-HT = 5-hydroxy-tryptamin) and gamma-amino butyric acid (GABA) express inhibitory influences on sexual activity [6,7,8,9,10] Most of these messengers are observed in the suprachiasmatic nuclei (SCN), which are located in the anterior hypothalamus.
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