[Show abstract][Hide abstract] ABSTRACT: The structure and chemical composition of the accessory olfactory bulb (AOB) were examined in male and female goats. Sections were subjected to either Nissl staining, Klüver-Barrera staining, lectin histochemistry, or immunohistochemistry for nitric oxide synthase (NOS), neuropeptide Y (NPY), tyrosine hydroxylase (TH), dopamine beta-hydroxylase (DBH), and glutamic acid decarboxylase (GAD). The goat AOB was divided into four layers: the vomeronasal nerve layer (VNL), glomerular layer (GL), mitral/tufted (M/T) cell layer (MTL), and granule cell layer (GRL). Quantitative and morphometric analyses indicated that a single AOB contained 5,000-8,000 putative M/T cells with no sex differences, whereas the AOB was slightly larger in males. Of the 21 lectins examined, 7 specifically bound to the VNL and GL, and 1 bound not only to the VNL, but also to the MTL and GRL. In either of these cases, no heterogeneity of lectin staining was observed in the rostrocaudal direction. NOS-, TH-, DBH-, and GAD-immunoreactivity (ir) were observed in the MTL and GRL, whereas NPY-ir was present only in the GRL. In the GL, periglomerular cells with GAD-ir were found in abundance, and a subset of periglomerular cells containing TH-ir was also found. Double-labeling immunohistochemistry revealed that virtually all periglomerular cells containing TH-ir were colocalized with GAD-ir.
Full-text · Article · Mar 2007 · The Anatomical Record Advances in Integrative Anatomy and Evolutionary Biology
[Show abstract][Hide abstract] ABSTRACT: The present study aims to elucidate whether the central melanocortin receptors [melanocortin-3 and -4 receptors (MC3/4-R)] are involved in regulating GnRH pulse generator activity in female goats. The GnRH pulse generator activity was electrophysiologically assessed at the intervals of characteristic increases in multiple-unit activity (MUA volleys) in the mediobasal hypothalamus. In ovariectomized goats, all doses (0.02, 0.2 and 2 nmol) of MT II, an MC3/4-R agonist, injected into the lateral ventricle significantly shortened MUA volley intervals. The duration of the period during which MT II accelerated MUA volleys was positively correlated with the dose of MT II injected. The stimulatory effect of MT II on the GnRH pulse generator activity was attenuated in the presence of estrogen. Intracerebroventricular injection of SHU9119, an MC3/4-R antagonist, significantly prolonged MUA volley intervals at 1 nmol. MT II (0.2 nmol)-induced acceleration of MUA volleys was partially blocked by the antagonism of MC3/4-R with pre-administered SHU9119 (1 nmol). The present findings demonstrate that MC3/4-R are involved in maintaining GnRH pulse generator activity in goats.
No preview · Article · Sep 2005 · Neuroscience Letters
[Show abstract][Hide abstract] ABSTRACT: The time course of GnRH pulse generator activity and plasma concentrations of energy substrates and insulin were simultaneously observed in female goats during 4-day fasting and subsequent refeeding in the presence or absence of estrogen for a better understanding of the mechanism of energetic control of gonadotropin secretion in ruminants. The GnRH pulse generator activity was electrophysiologically assessed with the intervals of characteristic increases in multiple-unit activity (MUA volleys) in the mediobasal hypothalamus. In estradiol-treated ovariectomized (OVX+E2) goats, the MUA volley intervals increased as fasting progressed. Plasma concentrations of non-esterified fatty acid and ketone body increased, while those of acetic acid and insulin decreased during fasting. The MUA volley intervals and plasma concentrations of those metabolites and insulin were restored to pre-fasting levels after subsequent refeeding. In ovariectomized (OVX) goats, changes in plasma metabolites and insulin concentrations were similar to those in OVX+E2 goats, but the MUA volley intervals were not altered. The present results demonstrated that fasting suppressed GnRH pulse generator activity in an estrogen-dependent manner. Changes in plasma concentrations of energy substrates and insulin during fasting were associated with the GnRH pulse generator activity in the presence of estrogen, but not in the absence of the steroid in female goats.
Full-text · Article · Jan 2005 · Journal of Reproduction and Development
[Show abstract][Hide abstract] ABSTRACT: It has been shown in various species that the onset of puberty is closely associated with body growth and nutritional state rather than age. The present study was conducted to determine the timing of puberty and to clarify body growth and metabolic changes around the pubertal period in female Shiba goats. Blood samples were collected between 10 to 38 weeks of age from 12 female goats, and plasma concentrations of progesterone, metabolites (glucose, nonesterified fatty acid, ketone body and acetic acid) and metabolic hormones (insulin and insulin-like growth factor-I (IGF-I)) were analyzed. Physical parameters (body weight, withers height and body length) were also measured at the blood sampling. The week when plasma progesterone concentrations first exceeded 1.0 ng/ml was designated as the onset of puberty. The results showed that the average age of the onset of puberty was 27.0 +/- 0.9 (mean +/- SEM) weeks in female Shiba goats. When the goats reached puberty, the average values of body weight and goat body mass index ((body weight (kg)/withers height (cm)/body length (cm)) x 10(3)) were 12.2 +/- 0.5 kg and 5.7 +/- 0.2, respectively. No particular change associated with puberty was apparent for plasma concentrations of the metabolites examined. Plasma insulin concentrations were maintained at lower levels until the onset of puberty, and then they began to gradually increase. Plasma IGF-I concentrations began to gradually increase 1 to 4 weeks before the onset of puberty and this increase continued throughout the peripubertal period. These results imply that IGF-I acts as a peripheral nutritional signal to trigger the onset of puberty in Shiba goats.
Full-text · Article · May 2004 · Journal of Reproduction and Development