TABLE 1.
Principal physiological changes of the HCRT system and functions during lactation.
| Animal | References | |
| Pre-pro-HCRT mRNA levels | ||
| Increase on PPD 1 compared to PPD 14 and pregnancy | Rat | Wang et al., 2003 |
| No differences on PPD 10 compared to diestrus | Rat | Brogan et al., 2000 |
| No differences on PPD 11–12 compared to postpartum non-lactating animals | Rat | Sun et al., 2003 |
| Decrease on PPD 14 compared to proestrus | Rat | Garcia et al., 2003 |
| Number of HCRT immunoreactive neurons | ||
| No differences between lactating on PPD 8 and virgin | Mice | España et al., 2004 |
| No differences on PPD 1, 14, and pregnancy | Rat | Wang et al., 2003 |
| Increase on PPD 12 compared to virgin females in anterior levels | Prairie vole | Donlin et al., 2014 |
| Increase in the number and mean staining intensity neurons on PPD 11–12 compared to non-lactating postpartum rats | Rat | Sun et al., 2003 |
| Increase in an anterior subpopulation on PPD 15 compared to proestrus and diestrus, and decrease between PPD 15 and PPD 21 | Rat | Diniz et al., 2018 |
| HCRT neuronal activity (Fos) | ||
| Increase on PPD 8 compared to virgin | Mice | España et al., 2004 |
| Increase in the central dorsomedial subpopulation on PPD 15 compared to proestrus and diestrus, and decrease between PPD 15 and PPD 21 | Rat | Diniz et al., 2018 |
| HCRT levels | ||
| No differences in hypothalamic HCRT-1 or HCRT-2 levels on PPD14 compared to virgin | Rat | Cai et al., 2001 |
| Negative correlation between HCRT-1 levels in the mPOA and the frequency of contact with pups | Rat | Grieb et al., 2018 |
| HCRT receptors mRNA expression in the hypothalamus | ||
| Increase in HCRT-R1 on PPD1 compared to PPD14 and pregnant. No changes in HCRT-R2 | Rat | Wang et al., 2003 |
| HCRT effects on maternal behavior and lactation (microinjections) | ||
| HCRT-1 i.c.v at intermediate doses increases pup-licking and grooming, while high doses reduce pup retrieval, nursing, and nesting behavior | Mice | D’Anna and Gammie, 2006 |
| HCRT-1 into the mPOA increases licking and retrieval, whereas HCRT-R1 antagonist reduces active maternal behavior and promotes nursing | Rat | Rivas et al., 2016 |
| DORA into the mPOA increases nursing and milk ejections | Rat | Rivas et al., 2021 |
| HCRT effects on postpartum wakefulness and sleep (microinjections) | ||
| HCRT-1 into the mPOA promotes wakefulness and reduces NREM and REM sleep | Rat | Rivas et al., 2021 |
| DORA into the mPOA increases NREM and REM sleep time | Rat | Rivas et al., 2021 |
| HCRT effects on prolactin secretion | ||
| HCRT-1 stimulates prolactin release from lactotroph cells in in vitro pituitary explants from lactating animals | Sheep | Molik et al., 2008 |
| Feeding (mRNA levels) | ||
| No changes in pre-pro-HCRT after 48 or 72 h of fasting on PPD 14 | Rat | Garcia et al., 2003 |
| Increase in HCRT-2 after 48 h of food restriction on PPD 14 | Rat | Cai et al., 2001 |
PPD, postpartum day; mPOA, medial preoptic area; i.c.v, intracerebroventricular.