Rhythmic Dependent Light Induction of Gonadotrophin‐Releasing Hormone‐I Expression and Activation of Dopaminergic Neurones within the Premammillary Nucleus of the Turkey Hypothalamus

Abstract

Our previous studies using turkey hens have demonstrated that c-fos mRNA (a marker of neuronal activation) is expressed in gonadotrophin-releasing hormone-I (GnRH-I), vasoactive intestinal peptide (VIP) and dopamine (DA) neurones following electrical stimulation in the preoptic area. DA has been shown to have both stimulatory and inhibitory effects on the GnRH-I/luteinising hormone (LH), follicle-stimulating hormone (FSH) and VIP/prolactin (PRL) systems. To identify the DA neurones that mediate the stimulatory influences of photoperiod on the reproductive system, we examined c-fos mRNA induction in DA, GnRH-I, and VIP neurones in the turkey hypothalamus using a dark-interruption experimental design. A 30-min light period was provided to short day (6L : 18D) photosensitive turkeys at times when birds were responsive to light (14 h after first light) and at times when birds were unresponsive to light (8 h and 20 h after first light). The only area where DA neurones were activated when the birds were provided with light was in the nucleus premammillaris (PMM). The number of activated DA neurones was significantly greater when light was provided at 14 h (during the photoinducible phase) than at 8 h or 20 h. At 14 h, there was also an increase in the number of GnRH-I neurones activated in the area of the nucleus commissura pallii (nCPa), as well as an up-regulation of GnRH-I mRNA expression. No expression of c-fos mRNA was observed in VIP neurones in the nucleus infundibularis or up-regulation of VIP mRNA expression in any of the experimental light treatments. These results are the first evidence to demonstrate a relationship between the dopaminergic system in the PMM and the GnRH-I system in the nCPa during the photoinduction of avian reproductive activity.

Dopamine and prolactin involvement in the maternal care of chicks in the native Thai hen (Gallus domesticus)

“…2 for a description of the abbreviations. (Bharati and Goodson, 2006), reproductive seasonality in turkeys (Thayananuphat et al, 2007), and maternal behaviors in native Thai chickens (Chaiyachet et al, 2013a,b;Prakobsaeng et al, 2011).…”

GABAergic Neurotransmission in the Premammillary Nucleus of the Turkey Hypothalamus Regulates Reproductive Seasonality and the Onset of Photorefractoriness

“…c-fos and GnRH-I cRNA probes were prepared as previously described [13]. c-fos and GnRH-I mRNA expressions and c-fos mRNA expression within GnRH-I-ir neurons were observed using ISH and double-labelled ISH/IHC techniques, respectively, as previously described [13].…”

“…Tissue preparation for single IHC, in situ hybridization (ISH), and double-labelled ISH/IHC was performed as previously described [13]. …”

“…The neuronal group in the PMM is photoreceptive since they express c-fos mRNA in response to a light pulse provided during the photosensitive phase together with the stimulation of gonadotrophin-releasing hormone-I (GnRH-I) neurons in the nucleus commissurae pallii (nCPA) [13]. Dopamine (DA) and the hormonal synchronizer of the circadian oscillators, melatonin (Mel), are colocalized within the PMM and exhibit a daily endogenous dual oscillation in DAergic/MELergic activities [14].…”

Genetic effects of polymorphisms in candidate genes and the QTL region on chicken age at first egg

“…Therefore, the GnRH-I and NPY genes were chosen as candidates for chicken AFE in this study. On the other hand, some workers reported that dopamine (DA) might be one of the putative neurotransmitters responsible for the activity of GnRH and had both stimulatory and inhibitory influences on gonadotropin release in birds [19-21]. Thus, one of its receptors, dopamine D2 receptor ( DRD2 ), could be a candidate gene for the control of AFE.…”