Photoperiodically driven changes in Fos expression within the basal tuberal hypothalamus and median eminence of Japanese quail

The rapid photoperiodic response in Japanese quail is so precise that it allows neural analyses of how photoperiodic information is transduced into an endocrine response. After transfer from short [SD; 6L:18D (6:18 hr light/dark cycle)] to long (LD; 20L:4D) days, luteinizing hormone (LH) first rises 20 hr after dawn. Using Fos immunocytochemistry, we examined the basal tuberal hypothalamus (BtH) to determine the relationship between brain cell activation and the first endocrine changes. Two separate cell populations within the BtH expressed Fos-like immunoreactivity (FLI) by hour 18 of the first LD. Importantly, this activation occurred before the LH rise. Median eminence activation appeared within glial cells, whereas activated infundibular nucleus cells were neuronal, providing support to the view that gonadotropin-releasing hormone (GnRH) release can be controlled at the terminals by glia. The FLI induction parallels LH changes, suggesting that gene expression may be involved in events preceding photostimulation and is the earliest photoperiodically stimulated physiological change yet reported.Additional experiments provided further support for this hypothesis. First, photoperiodically induced activation is not a result peculiar to castrates because intact birds displayed similar results. Second, the critical length of 14 hr of light had to be exceeded to cause both BtH activation and a LH rise 30 hr from dawn. Finally, valuable evidence of the response specificity was provided by using a unique property of the quail photoperiodic clock in which exposure to 10L:26D, but not 10L:14D, causes photoinduction. The 36 hr paradigm increased both plasma LH and BtH activation.</jats:p

Distribution And Abundance Of Glucocorticoid And Mineralocorticoid Receptors Throughout The Brain Of The Great Tit (Parus Major)

The glucocorticoid stress response, regulated by the hypothalamic-pituitary-adrenal (HPA) axis, enables individuals to cope with stressors through transcriptional effects in cells expressing the appropriate receptors. The two receptors that bind glucocorticoids—the mineralocorticoid receptor (MR) and glucocorticoid receptor (GR)—are present in a variety of vertebrate tissues, but their expression in the brain is especially important. Neural receptor patterns have the potential to integrate multiple behavioral and physiological traits simultaneously, including self-regulation of glucocorticoid secretion through negative feedback processes. In the present work, we quantified the expression of GR and MR mRNA throughout the brain of a female great tit (Parus major), creating a distribution map encompassing 48 regions. This map, the first of its kind for P. major, demonstrated a widespread but not ubiquitous distribution of both receptor types. In the paraventricular nucleus of the hypothalamus (PVN) and the hippocampus (HP)—the two brain regions that we sampled from a total of 25 birds, we found high GR mRNA expression in the former and, unexpectedly, low MR mRNA in the latter. We examined the covariation of MR and GR levels in these two regions and found a strong, positive relationship between MR in the PVN and MR in the HP and a similar trend for GR across these two regions. This correlation supports the idea that hormone pleiotropy may constrain an individual’s behavioral and physiological phenotype. In the female song system, we found moderate GR in hyperstriatum ventrale, pars caudalis (HVC), and moderate MR in robust nucleus of the arcopallium (RA). Understanding intra- and interspecific patterns of glucocorticoid receptor expression can inform us about the behavioral processes (e.g. song learning) that may be sensitive to stress and stimulate future hypotheses concerning the relationships between receptor expression, circulating hormone concentrations and performance traits under selection, including behavior

Sex differences in 50 kHz call subtypes emitted during tickling-induced playful behaviour in rats.

‘Tickling’ induces positive affective states in laboratory rats as evidenced by the production of 50-kHz ultrasonic vocalisations (USVs), although this has mostly been investigated in males. Juvenile rats emit distinctive 50-kHz USV subtypes. Frequency-modulated (FM) 50-kHz USVs are thought to be associated with positive affect and flat 50-kHz USVs with social communication. FM and flat USVs are produced by both sexes during tickling, but it is unclear whether these calls are produced in relation to particular play-related behaviours, and whether USV subtypes are used in a sexually dimorphic manner during tickling. We tested the hypotheses that FM USVs are associated with tickle-induced play behaviours in a sex-specific way, and that flat USVs are associated with non-play activities. Rats were allocated to one of two treatment groups: tickling (tickled, n = 16/sex) or no hand contact (control, n = 16/sex). Play behaviours (hopping, darting and hand approaches) and FM and flat USVs emitted during the testing session were quantified for each rat, with the frequency of FM and flat USVs made in anticipation of, and during, each behaviour analysed. In females, play behaviours were associated with more flat USVs than in males (before and during; p < 0.001), irrespective of treatment. FM USVs were paired with hopping and darting (before and during; p < 0.001), and in anticipation of hand approaches (p < 0.001) in both tickled females and males compared to controls (both sexes) suggesting that FM USVs are linked with play behaviour. The higher call rate of flat USVs paired with play behaviour in females suggests that there may be sex differences in the role of flat USVs during play. This result is evidence of sex differences in tickle-induced behaviours and has implications for our understanding of the function of different USVs in juvenile female and male rats