Previous binding studies indicated that there is little to no specific prolactin binding in ovine fetal liver and adult ovary. Therefore, we sought to determine if ovine prolactin receptor (PRLR) mRNA is present in those tissues. Primers were designed from the bovine PRLR cDNA sequence for use in reverse transcriptase-polymerase chain reaction (RT-PCR). RT-PCR analysis of ovine fetal liver total cellular RNA (tcRNA) isolated from days 60, 90, 105, 120 and 135 of gestation, and luteal tcRNA isolated from days 3, 7, 10, 13 and 16 of the estrous cycle revealed that PRLR mRNA was present in these tissues. However, two RT-PCR products were generated from both tissues. The two RT-PCR products did not differ between the two tissue sources in sequence, and were designated oPRLR-1 and oPRLR-2. Ovine PRLR-1 is 513 bp in length and is 96.4% identical to the bovine cDNA. Ovine PRLR-2 is identical to oPRLR-1 until nucleotide (nt) 420 at which point a 39 bp insertion occurs. This insertion occurs between Homology Boxes 1 and 2 within the cytoplasmic domain of the receptor, resulting in an 11 amino acid divergent sequence, followed by two stop codons. Ribonuclease-protection assay revealed that oPRLR-1 mRNA is the most abundant in these tissues. Our data indicate that two forms of oPRLR mRNA are Present in fetal liver and adult ovary, and that one form (oPRLR-2) is predicted to encode a truncated PRLR.

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We explored the possibility that quantitative analysis of the relationship between sucrose concentration and sham intake differentiated how various treatments affected the intake of sweet solutions. Rats were sham fed sucrose solutions varying in concentration from 0.03125 to 1.5 M. Under different treatment conditions, intake concentration functions were generated that plotted amount sham fed against sucrose concentration. Sucrose concentration that yielded 50% maximal sham intake were calculated to indicate the position of the concentration-intake function on the x-axis. Quinine adulteration of sucrose solutions and injection of 0.5 mg/kg i.p. of the dopamine antagonist pimozide reduced sham intake and shifted the concentration-intake function to the right. Lithium chloride (60 mg/kg i.p.) injected 30 min before sham feeding, a reduction of food deprivation from 18 to 6 h before sham feeding, and 6 micrograms/kg cholecystokinin octapeptide reduced sham intake equivalent amounts but did not shift the concentration-intake functions along the x-axis. The data indicate that of several factors that reduce sham feeding, only some also shift the position of concentration-intake curves, and these curve shifts may identify intake changes mediated by alterations in the processing of the taste input.

Survival requires the selection of appropriate behaviour in response to threats, and dysregulated defensive reactions are associated with psychiatric illnesses such as posttraumatic stress and panic disorder.1 Threat-induced behaviour, including panic-like flight, is controlled by neuronal circuits in the central amygdala (CeA)2; however, the source of neuronal excitation to the CeA that contributes to these high-intensity defensive responses is unknown. Here we used a combination of neuroanatomical mapping, in-vivo calcium imaging, functional manipulations, and slice physiology to characterize a previously unknown projection from the dorsal peduncular (DP) prefrontal cortex to the CeA. DP-to-CeA neurons are glutamatergic and specifically target the medial CeA. Using a behavioural paradigm that elicits both freezing and flight, we found that CeA-projecting DP neurons are activated by high-intensity threats in a context-dependent manner. Functional manipulations revealed that the DP-to-CeA pathway is necessary for both avoidance behaviour and flight. Furthermore, we found that DP projections preferentially target distinct medial CeA neuronal populations linked to flight. These results are the first demonstration that the prefrontal cortex exerts direct, top-down control of the CeA and elucidate a non-canonical pathway regulating panic-like fear responses.

Social behavior is complex and fundamental, and its deficits are common pathological features for several psychiatric disorders including anxiety, depression, and posttraumatic stress disorder. Acute stress may have a negative impact on social behavior, and these effects can vary based on sex. The aim of this study was to explore the effect of acute footshock stress, using analogous parameters to those commonly used in fear conditioning assays, on the sociability of male and female C57BL/6J mice in a standard social approach test. Animals were divided into two main groups of footshock stress (22 male, 24 female) and context exposed control (23 male and 22 female). Each group had mice that were treated intraperitoneally with either the benzodiazepine—alprazolam (control: 10 male, 10 female; stress: 11 male, 11 female), or vehicle (control: 13 male, 12 female; stress: 11 male, 13 female). In all groups, neuronal activation during social approach was assessed using immunohistochemistry against the immediate early gene product cFos. Although footshock stress did not significantly alter sociability or latency to approach a social stimulus, it did increase defensive tail-rattling behavior specifically in males (p = 0.0022). This stress-induced increase in tail-rattling was alleviated by alprazolam (p = 0.03), yet alprazolam had no effect on female tail-rattling behavior in the stress group. Alprazolam lowered cFos expression in the medial prefrontal cortex (p = 0.001 infralimbic area, p = 0.02 prelimbic area), and social approach induced sex-dependent differences in cFos activation in the ventromedial intercalated cell clusters (p = 0.04). Social approach following stress-induced cFos expression was positively correlated with latency to approach and negatively correlated with sociability in the prelimbic area and multiple amygdala subregions (all p < 0.05). Collectively, our results suggest that acute footshock stress induces sex-dependent alterations in defensiveness and differential patterns of cFos activation during social approach.