Embryonic Development of Avian Pineal Secretory Activity—A Lesson from the Goose Pineal Organs in Superfusion Culture

Abstract

The embryonic ontogeny of pineal secretory activity in birds has been investigated almost exclusively in chickens. This study aimed to characterize this process in domestic geese. The pineal organs of embryos aged 18–28 days were incubated in superfusion culture under different light conditions for 4–5 days and treated with norepinephrine (NE). Melatonin (MLT) was measured by radioimmunoassay and other indoles by HPLC with fluorescence detection. Additionally, pineal organs were collected from embryos at 14–28 days of age and used to measure catecholamines by HPLC with electrochemical detection. MLT secretion increased with embryo age, most intensively between the 22nd and 24th days of life. The daily changes in MLT secretion under the 12 L:12D cycle occurred on the first day of culture, starting from an embryonic age of 24 days. MLT secretion was controlled by the light-dark cycle in all age groups studied. However, exposure to light during the scotophase did not alter the secretion of MLT. The endogenous oscillator expressed its activity in regulating MLT secretion in the pineal organs of embryos aged 24 days and older but could not generate a rhythm after one cycle. The rhythm of 5-hydroxytryptophan release during the first day of culture was found in the pineal organs of all embryos, while the rhythmic release of N-acetylserotonin and 5-methoxyindole acetic acid started at the age of 24 days. The proportion of released indoles changed with embryo age. NE caused a decrease in MLT secretion and provoked an increase in serotonin release. Incubation of the pineal organs induced the development of MLT secretory machinery and its diurnal rhythmicity. The pineal content of catecholamines increased prominently at the end of embryonic development.

Embryonic development of the chick pineal gland throughout the incubation periods

“…studies have been conducted on chicken (Geng et al, 2022;Kumar & Meshram, 2020;Tainika & Bayraktar, 2022;Wang et al, 2021), quail (Moussa, 2019), goose (Hanuszewska-Dominiak et al, 2021), turkey (Martyniuk et al, 2022;Prusik, 2022) and gull (Przybylska-Gornowicz et al, 2012) regarding the avian pineal organ.…”

“…Moreover, it plays an important role in the regulation of many behavioural and physiological events, including migration (Przybylska‐Gornowicz et al., 2012). In recent years, many recent studies have been conducted on chicken (Geng et al., 2022; Kumar & Meshram, 2020; Tainika & Bayraktar, 2022; Wang et al., 2021), quail (Moussa, 2019), goose (Hanuszewska‐Dominiak et al., 2021), turkey (Martyniuk et al., 2022; Prusik, 2022) and gull (Przybylska‐Gornowicz et al., 2012) regarding the avian pineal organ.…”

“…In the studies, pinealocytes are reported to have small apical extensions (Boya & Calvo, 1980; Collin et al., 1986; Korf & Vigh‐Teichmann, 1984; Przybylska‐Gornowicz et al., 2012; Tabecka et al., 1999; Vigh & Vigh‐Teichmann, 1999). These cells, larger than neuroglial cells, are round or oval nuclei and pale stained cytoplasm (Cui, 2011; Gartner & Hiatt, 2017; Hanuszewska‐Dominiak et al., 2021; Kumar & Meshram, 2020; Martyniuk et al., 2022). Also, these cells are differentiated as follicular and parafollicular cells according to their contact with the follicular lumen (Boya & Calvo, 1980).…”

“…These cells are modified neurons with round or oval nuclei and pale stained cytoplasm containing melatonin‐filled granules. They transform from neuroendocrine photoreceptors to neuroendocrine cells (Cui, 2011; Gartner & Hiatt, 2017; Hanuszewska‐Dominiak et al., 2021; Kumar & Meshram, 2020; Martyniuk et al., 2022). Pinealocytes are differentiated as follicular and parafollicular cells according to their contact with the follicular lumen (Boya & Calvo, 1980).…”