Effects of septal-forebrain lesions on maternal aggression and maternal care

Septal-forebrain lesions significantly increased the defensive reactions of lactating Long-Evans rats (n = 13) relative to nonlesioned control females. The lesions greatly enhanced defensive behaviors on a number of standard tests (e.g., responsiveness to humans and anesthetized conspecifics) while abolishing aggression toward intruding male conspecifics. The lesions also produced a striking disruption in maternal behavior as evidenced by absence of nest building, reduced litter weights, failure to retrieve, lick, or nurse pups, and increased cannibalization. While these results cannot be interpreted as indicating that maternal aggression is equivalent to offense, they are congruent with such a view. Certainly they are not supportive of a view that maternal aggression is primarily defensive. The lesion-induced abolition of maternal attack may have resulted from an inhibition of offensive tendencies by heightened defensiveness and/or reduced pup stimulation. There was no evidence that the lesion-induced impairment in maternal behavior resulted from a failure to sequence the individual behavioral acts comprising maternal behavior. Rather, all features of maternal care seemed to be greatly attenuated.

Effects of hypothalamic knife cuts and experience on maternal behavior in the rat

Recent investigations suggest that the disruption of placentophagia, pup-directed maternal behavior, and nestbuilding seen after lesions of the medial preoptic area (MPO) or the lateral hypothalamus may be due to the interruption at different points of a single longitudinal neural system mediating these behaviors. To test this, we compared the effects of knife cuts on the lateral border of the MPO, and of the posterior medial forebrain bundle (MFB), with asymmetrical cuts combining a unilateral MPO cut with a contralateral MFB cut. We observed placentophagia, nestbuilding, and pup-directed maternal behaviors at, and after, parturition in both primiparous and biparous rats. In primiparae, MPO cuts (a) disrupted placentophagia, (b) delayed the onset of crouching and pup-licking, and (c) eliminated retrieval and nestbuilding. MFB cuts (a) disrupted placentophagia, (b) delayed the onset of maternal behavior, and (c) eliminated nestbuilding. Asymmetrical cuts (a) disrupted placentophagia, and (b) delayed the onset of maternal behavior. In biparous rats, MPO cuts eliminated nestbuilding and retrieval. MFB cuts (a) disrupted placentophagia, and (b) eliminated nestbuilding. Asymmetrical cuts (a) delayed nestbuilding. These results suggest the involvement of a longitudinal neural system in the production of immediate pup-directed maternal behavior, placentophagia, and nestbuilding in parturient primiparae, but which is not critical for the eventual display of maternal behavior and nestbuilding in maternally naive rats, nor for the immediate onset of placentophagia and maternal behavior in maternally experienced rats.

Photoperiod time measurement for activity, torpor, molt and reproduction in mice

Resonance light:dark cycles (LD 6:18, 6:30, 6:42, or 6:54) were used to establish that a circadian rhythm of light sensitivity is involved in the thermoregulatory and reproductive responses to a short day photoperiod in the mouse, Peromyscus leucopus. A fifth group was maintained on the long day photoperiod of LD 16:8. After 19 weeks animals presented with LD 6:18 or 6:42 exhibited short day photoperiod responses: gonadal regression, incidence of spontaneous daily torpor and molt to the winter pelage. In contrast animals responded to LD 6:30 and 6:54 as long day photoperiods: maintenance of gonadal system, no incidence of spontaneous daily torpor, and summer pelage. In a second study a T-experiment was conducted to determine that more than one circadian system may regulate these multiple photoperiodic effects. Mice were exposed to 1 of 8 LD cycles for 15 weeks (1:22.00, 1:22.25, 1:22.50, 1:23.00, 1:23.50, 1:23.75, 9:15, or 16:8), Entrained wheel-running activity occurred under all LD regimes. Mice on LD 1:22.50, 1:23.00, and 1:23.50, however, exhibited activity patterns similar to mice on LD 9:15, and they exhibited gonadal regression. Mice on LD 1:22.00, 1:22.25, and 1:23.75 exhibited activity patterns similar to LD 16:8 animals, and most of these animals remained reproductively competent. There was also a close association between occurrence of reproductive regression and daily torpor. In contrast, molt to the winter pelt occurred under all non-24-hr LD cycles. This dysynchrony in response suggests that at least 2 circadian systems are involved in photoperiodic time measurement in P. leucopus.

Intrauterine position modulates maternal behaviors in female mice

Intrauterine position (IUP), the proximity of a fetus relative to same and opposite sex fetuses, is a reliable predictor of the direction and intensity of social and regulatory behaviors in adult male and female mice. In the present experiment, female Rockland-Swiss (R-S) mice who had resided in utero between two females (OM) and females who had resided between two males (2M) were compared with respect to five indices of maternal behavior: Spontaneous parental responses exhibited toward neonates; nestbuilding during pregnancy; aggression during pregnancy; aggression during lactation; and reproductive/lactation performance. There was no significant difference between 0M and 2M females in their spontaneous parental responses toward neonates or their level of nestbuilding behavior during pregnancy. However, when tested for aggression during pregnancy and lactation, 2M females exhibited aggression on a greater number of test days during pregnancy than did 0M females. Also, during pregnancy and lactation, 2M females displayed more lunges and attacks toward adult male intruders than 0M females. Although 0M females tended to have larger litters than 2M females, the animals did not differ with respect to any other measure of reproductive/lactation performance. Intrauterine position, therefore, modulates some aspects of maternal behavior but apparently not others.

Effects of unusually early visual stimulation on the development of homing behavior in the rat pup

Two studies examined the theory that early limitations on sensory functioning contribute to the organization of a structure for perceptual development and intersensory functioning. Rat pups' eyelids were surgically opened on Day 7, following which the development of homing to their nest site was investigated, with each animal alone in its living cage. Control pups increased homing until Day 14, and then decreased. Experimental pups showed no such decline, with the highest rate of homing evident on the last day of testing. The importance of visual cues for this altered development of homing was examined. Visual cues for the home were reduced by removing all shavings during testing, while leaving an odorous substrate in place. Under these conditions, both groups showed the characteristic increase and decline in homing, suggesting that premature eyelid opening results in a modification of the distribution of attention to visual and olfactory characteristics of the nest.

Maturation of olfactory exploration in golden hamsters

Following placement into a test cage filled with pine shavings, a litter of 7-8 golden hamster pups (aged 3-18 days postnatal: P3-18) initially displays a period of locomotion which ends reliably in huddling. The latency to establish a huddle (i.e., the duration of locomotion) is significantly longer in the presence of novel odors (fresh or lemon shavings) than more familiar odors (slightly soiled fresh or lemon shavings) but only in pups aged P12 or older. Pups aged P9 or younger do not locomote differentially in the presence of novel or familiar odors. This age difference represents the emergence of olfactory exploration in hamsters between P9 and P12. Exploration of novel odors interferes with initial attempts to establish a single huddle site by a litter, but does not preclude the ultimate aggregation of all pups at a single site as guided by conspecific odors and possibly thermotactile cues as well. Such shifts in the control of behavior by non-nest and nest-related, conspecific stimuli correspond well with the first occurrence of nest exits at P11-12 (e.g., Dieterlen, 1959) coupled with the persistent return of hamster pups to the maternal nest for as long as it is maintained (Rowell, 1961).

The effects of paraventricular hypothalamic lesions on maternal behavior in rats

The present study was undertaken to determine whether the disruptive effects of knife cuts which sever the lateral connections of the medial preoptic area (MPOA) on maternal behavior are mediated by interfering with the output of the paraventricular hypothalamic nucleus (PVN). Postpartum rats received one of the following: Knife cuts severing the lateral connections of the MPOA; knife cuts severing the lateral connections of the PVN; radiofrequency lesions of the PVN; sham lesions or knife cuts. Only females that received knife cuts severing the lateral connections of the MPOA showed severe deficits in maternal behavior. These results indicate that the influence of the MPOA on maternal behavior is not mediated by the output of the PVN. Since the PVN is the major source of oxytocin input to other brain regions, these results also suggest that oxytocinergic neural pathways are not critical for postpartum maternal behavior. Another important finding was that females with MPOA knife cuts that did not retrieve their young were capable of hoarding candy, suggesting that the retrieval deficit was not the result of a general oral motor deficit.

Olfaction and behavioral modification in domestic chicks (Gallus domesticus)

Olfactory responsiveness in the female domestic chick was examined in a series of experiments. Individually-housed chicks preferred the familiar soiled substrate from their own home box to that soiled by a strange conspecific and to clean wood litter when placed in an otherwise novel Y maze. An artificial odorant present during the development of group-reared chicks subsequently proved attractive in an otherwise novel and potentially frightening situation. Chicks reared with one of two aromatic oils subsequently discriminated between them and preferred the familiar oil when both were present in the test box. The preferences are likely acquired because naive, one-day-old chicks reacted similarly to wood litter treated with either water or oil. Presence of a familiar rearing odor also reduced fear of a novel open field. In contrast to controls, chicks whose nostrils were blocked prior to rearing with an aromatic oil showed no subsequent preference for this odorant. The present results suggest that domestic chicks can regulate their behavior in response to olfactory cues though trigeminal chemoreception may also be involved.

Effect of feed and water deprivation or force-feeding on plasma prolactin concentration in turkey hens

Plasma concentrations of prolactin (Prl), glucose, corticosterone, and D(-)-3-hydroxybutyrate (DBHB) were compared in nonlaying, nonincubating turkey hens subjected to feed and/or water deprivation. Neither Prl nor corticosterone concentrations were significantly (P greater than 0.05) altered by any of the treatments, whereas fasting significantly (P less than 0.05) reduced the concentration of glucose and increased the concentration of DBHB. Plasma levels of Prl in incubating hens were significantly (P less than 0.05) reduced by nest deprivation either in the absence of feed and water or when the hens were force-fed the normal intake for a laying hen. After 48 h of nest deprivation, the hens resumed nesting within 5 min of being returned to the pen although the plasma levels of Prl were low. Neither nest attentiveness nor the concentration of Prl were affected by force-feeding the hens while they were incubating eggs. The concentration of glucose increased in response to force-feeding or nest deprivation, whereas the concentration of corticosterone was increased only by force-feeding. These results suggest that Prl may not be involved in the striking changes in both intermediary and water metabolism which occur during incubation in the turkey hen. Furthermore, since incubation behavior can occur in the presence of low concentrations of Prl, elevated levels of Prl during broodiness appear to be maintained by a stimulus associated with the nest itself or some other aspect(s) of the environment.

Neonatal frontal lesions in hamsters impair species-typical behaviors and reduce brain weight and neocortical thickness

Syrian golden hamsters with removals of the medial or ventral subfields of the frontal cortex at 4 days of age were compared behaviorally and neuroanatomically with hamsters with similar removals in adulthood. The behavioral results showed that hamsters with neonatal lesions show little sparing of species-typical behaviors such as hoarding and nest building. Study of the development of animals with early lesions showed that although as young juveniles the operated hamsters did not appear to be different from their littermate controls, as they developed they failed to improve in their performance as their littermates did. As adults these early operates were thus severely impaired relative to their littermates. Nonetheless, under certain environmental conditions it was possible to show that the animals were capable of performing the behaviors nearly as proficiently as normal animals. Thus, in order to thoroughly assess the extent of behavioral sparing following early neonatal lesions, it is necessary to test animals under widely varying stimulus conditions. Finally, when the brains of neonatally operated hamsters were compared with those of animals operated on in adulthood, there were striking differences; although the area of cavity appeared smaller in the neonatal operates, their brains weighed less and the remaining neocortex was thinner.

Aspects of the neuroendocrine control of ovulation and broodiness in the domestic hen

The neuroendocrine control of ovulation and broodiness in the domestic hen involves complex interactions between hypothalamic neuropeptides, neurotransmitters, and ovarian steroids which regulate the secretion of luteinizing hormone (LH) and prolactin. Nuclear progesterone receptor is localized in many neurons throughout the hypothalamus but is absent from LHRH neurons. Hence, the positive feedback action of progesterone on LH release is not mediated by a genomic mechanism within the LHRH neuron. Precursors of 5-hydroxytryptamine (5HT) and dopamine (DA) inhibit the preovulatory release of LH, while the turnover rates of these neurotransmitters in the anterior hypothalamus decrease when preovulatory levels of LH are at their highest. Further, a population of receptors for 5HT which occurs in the anterior hypothalamus in laying birds is absent in nonlaying, incubating hens. Taken together, these observations suggest that the preovulatory surge of LH is mediated by a transitory decrease in the inhibitory action of 5HT and possibly DA, on the secretion of LHRH. Neurons containing 5HT may play a role in the regulation of prolactin release and, more specifically, in the control of broodiness. Drugs which enhance the function of 5HT neurons stimulate prolactin release while increased prolactin secretion in incubating hens is associated with an increase in the turnover of 5HT in the anterior hypothalamus. No receptors for 5HT were demonstrable in the anterior pituitary gland, showing that the prolactin-releasing activity of 5HT must be mediated by a prolactin-releasing factor (PRF). A candidate for a physiological PRF is vasoactive intestinal polypeptide (VIP).(ABSTRACT TRUNCATED AT 250 WORDS)

Hormonal correlates of polyandry in the spotted sandpiper, Actitis macularia

Plasma samples from naturally breeding populations of spotted sandpipers, Actitis macularia, were analyzed by radioimmunoassay for circulating levels of immunoreactive luteinizing hormone (irLH), and four steroid hormones. Plasma levels of irLH, corticosterone (C), and estradiol-17 beta (E) did not differ between males and females. Males had curiously high levels of E (0.64 pg/ml in nonnesting males; 0.35 pg/ml in nesting males) which are similar to those of nonlaying females (0.23 pg/ml). Testosterone (T) and dihydrotestosterone (DHT) were higher in nonnesting males (0.95 ng/ml for T; 0.20 ng/ml for DHT) than in females (0.18 ng/ml for T; 0.12 ng/ml for DHT) or nesting males (0.17 ng/ml for T; 0.09 ng/ml for DHT). These data do not support earlier suggestions that in polyandrous mating systems, females have higher circulating levels of androgens than males.

Normal and experimentally induced changes in hormonal hemolymph titers during parental behavior of the earwig Labidura riparia

The reproductive cycle of Labidura riparia includes two distinct phases of behavior: a feeding and sexual phase followed by a parental and fasting phase. These phases correspond to two contrasting physiological phases (vitellogenesis, followed by ovarian inactivity). These correlations have been verified by correlating radioimmunoassay (RIA) measurements of the levels of circulating juvenile hormones (JH) and ecdysteroids with ovarian state during the first reproductive cycle. Similar studies were also made after experimentally suppressing parental activity (care of eggs) either by depriving females of their eggs or by force-feeding during the egg-care phase. Taking eggs away without feeding caused the disappearance of parental behavior and a short lived period of vitellogenesis. Likewise, feeding in the presence of eggs resulted in vitellogenesis and disappearance of egg-care behavior. Thus, it appears that in order for the parental phase to develop normally it is necessary to preserve the proper external conditions (the presence of eggs) and physiological conditions (fasting).

Prolactin and parenting in the pigeon family

The relationship between plasma prolactin and: crop growth; incubation; brooding; and feeding young in Columbiformes is reviewed. There is a good parallel between changes in crop growth and plasma prolactin fluctuations during the breeding cycle. Prolactin does not play a role in the initiation of incubation, though it can maintain the response. Toward the end of breeding, a decline in prolactin precedes the decline in incubation (of infertile eggs) or brooding (of young), while exogenously administered prolactin can prolong the response. There is no evidence of a necessary relationship between prolactin secretion and parental feeding of young, as this behavior can precede and outlast the secretion of the hormone during breeding.

The effects of modifying incubation on prolactin secretion in free-living pied flycatchers

Plasma prolactin concentrations in female pied flycatchers are high during incubation, but fall from 156 +/- 27 to 67 +/- 6 ng/ml (P less than 0.01) between 2 and 4 days after the young hatch. The timing of the fall in prolactin could be determined by factors associated with the hatching of the eggs and growth of the offspring; alternatively, prolactin may remain high for a fixed period (16 days) after the onset of incubation. To distinguish between these possibilities, eggs were exchanged between nest boxes to ensure incubation periods of either 10, 14, or 19 days by different females. The results showed that the period of high prolactin secretion was shortened by 2-4 days where the eggs hatched early, but, conversely, was not lengthened in those females with extended incubation periods, the levels actually falling in these birds before the eggs hatched. There was, however, a secondary rise in prolactin 3 days after hatching, when the level of 114 +/- 11 ng/ml 22 days after the onset of incubation was much higher than that (30 +/- 4 ng/ml) at a comparable stage in the control females. Thus, high prolactin secretion cannot be maintained for longer than 16-17 days in incubating birds, but newly hatched, naked young can stimulate prolactin release in female flycatchers over a flexible period.

Investigation of a common physiological mechanism underlying progesterone-induced and maternal nesting in mice, Mus musculus

These experiments addressed the possibility that genetic differences in plasma progesterone levels underlie genetic differences observed in maternal nesting (nest building by pregnant mice). Because this hypothesis requires that different circulating levels of progesterone result in a corresponding elevation of nesting, groups of outbred females were treated with varying doses of progesterone, and their nesting was measured. The relation between progesterone dose and nesting was not linear; rather, there appeared to be a threshold dose above which all groups responded similarly. Next, the progesterone levels of four inbred strains and lines selectively bred for differences in nonpregnant (thermoregulatory) nesting were measured directly by radioimmunoassay. The rank order of the inbred strains' and selected lines' progesterone levels did not correspond to the rank order of their nesting. Thus, genetically based differences in maternal nesting are not due to differences in circulating progesterone levels. Other results are presented which suggest a thermo-regulatory mechanism underlying progesterone-mediated maternal nesting which may involve genetic differences in thermal set point.

Parental fanning behavior and prolactin cell activity in the male three-spined stickleback Gasterosteus aculeatus L

During the period that sexually mature male three-spined sticklebacks display parental fanning behavior, the rate of synthesis and release of the prolactin cells in the hypophysis, as estimated with quantitative electron microscopy, is enhanced considerably. This finding points to involvement of endogenous prolactin in the regulation of parental fanning behavior in this species.

Mice: progesterone and the regulation of strain differences in pregnancy-induced nest building

Pregnant DBA/2J females built significantly larger and more completely enclosed nests than did pregnant C57BL/6J mice. This strain difference was restricted to the last half of gestation and was not observed during either the virgin state or lactation. Genotype-based differences in pregnancy-induced nest building were not related to circulating levels of progesterone (P), core temperature, or body weight. Exposure to supplemented P during pregnancy elevated nest building exhibited by pregnant C57BL females but did not induce DBA-like levels of the behavior. Also, virgin DBA females built larger nests in response to P than did C57BL females. These findings suggest that differences in the sensitivity of central neural tissue to steroid hormones may account for genotypically determined variation in patterns of pregnancy-induced nest building.

Effect of pinealectomy on broodiness of turkey hens

Large White breeder hens with a history of broody behavior were recycled into a second reproductive cycle following pinealectomy. Pinealectomy did not alter the performance of broody hens with respect to time to first egg, duration of egg production, eggs per hen, number and duration of egg sequences, number and duration of pauses, time to onset of broody nesting behavior, or persistency of nesting. It was concluded that the pineal gland does not play an essential role in the onset or maintenance of broodiness in turkey hens.

Timing of incubation bouts by ring doves (Streptopelia risoria)

Ring dove parents share in incubation and brooding such that the male sits for a block of time toward the middle of the day and the female sits the rest of the time. In order to evaluate the role of the sexes in determining nest exchange, approaches to the nest, the timing of incubation behavior, and the topography of interactions at the nest site were continuously monitored. Most nest exchanges (87%) were initiated by the nonsitting mate. There was less variability associated with the onset of sitting by the female than by the male. The male entered the nest area repeatedly from the time of lights-on until nest exchange several hours later. In contrast, the female rarely entered the nest area when the male was sitting, and when she did approach, nest exchange usually ensued. When the male's entrances to the nest area were prevented until the usual time of nest exchange, the timing of the subsequent sitting bout and nest exchange was not altered, which indicates that male visits are not a necessary prerequisite for nest exchange. Each pair developed a cooperative interaction as incubation progressed. When mates were exchanged among physiologically synchronized pairs, a serious disruption of sitting resulted. It is concluded that behavioral synchrony between the mates in the form of each pair's bond is as necessary as physiological synchrony in maintaining intermate cooperation in parental behavior of ring doves.

Temporal analysis of REM sleep after nest-building behavior in nulliparous albino rat

EEG recording was performed, during nest-building behavior (NBB), from the hippocampus and sensorimotor cortex of nulliparous albino rats with simultaneous recordings of EMGs of neck-muscle and eye movements. The duration of NBB varied with a period of 4-5 days. However, the relative durations of behavioral transitions in NBB, i.e., nest-building, grooming, and sleeping, were regular in both long lasting and early terminated NBB. REM sleep was identified, in every instance, immediately after NBB. The latency of REM sleep was significantly tied to the termination of NBB without regard to the duration of NBB. Differences in the duration of NBB, however, affected REM-propensity: the longer the NBB was, the shorter the latency of REM sleep tended to be. NBB might accelerate the induction of the physiological condition responsible for REM sleep generation.

Serum prolactin levels and crop-sac development in ring doves during a breeding cycle

Using a turkey prolactin radioimmunoassay, the serum prolactin levels of male and female ring doves (Streptopelia risoria) during the breeding cycle were measured and their circulating prolactin levels were compared to crop-sac weight on a within-bird basis. During the early phase of the incubation period, crop weight showed a delayed response to prolactin stimulation and there was no correlation; during the midincubation period when prolactin and crop-sac weight were increasing, there was a strong positive correlation; around hatching, when prolactin was at its peak, there was no correlation. There were again strong positive correlations at later samples, when squabs were developing and both prolactin and crop-sac weight were declining. Thus, it appears that the correlation between the circulating prolactin level and crop-sac development depends on the stage of the breeding cycle. While males and females showed similar pattern of circulating prolactin during the period of incubation and parental care, only females consistently showed a postovulatory rise of prolactin. These results were discussed in the context of the role of prolactin in the breeding cycle.

Metabolic cost of incubation in the Laysan albatross and Bonin petrel

1. Oxygen consumption and carbon dioxide production were measured in resting and incubating Laysan albatrosses and Bonin petrels on Midway Atoll in the north central Pacific Ocean. 2. Incubation metabolism within the thermal neutral zone is less than or equal to resting metabolism in the albatross and petrel. 3. The respiratory quotients (0.64-0.72) during the long fasts indicate fat metabolism. 4. The estimated fractional water content of the albatross and petrel do not change during incubation fasts because water loss is balanced by metabolic water production.

Influence of pinealectomy and photoperiod on courtship and nest-building in male doves

Sham-operated male doves displayed greater nesting activity under long days (16L:8D) than under short days (8L:16D). This difference was abolished by pinealectomy--the activity of long-day pinealectomized birds dropped to a level comparable to that seen on short days. Removal of the pineal had no effect under the short photoperiod. These results are not due to changes in peripheral androgen production as castrated, testosterone-implanted males also exhibited higher levels of nest-building on long days if sham-operated, but not if they were pinealectomized. Neither treatment had a significant effect on courtship or copulatory behavior. It is suggested that the pineal mediates the stimulatory effect of long photoperiods on hormonally-induced nest-building in doves.

Nest-building behavior in two cerebellar mutant mice: staggerer and weaver

Nest-building behavior was studied in two separate (different genes) but phenotypically similar autosomal recessive neurological (cerebellar) mutants, staggerer and weaver, as well as their wild-type siblings. None of the test animals or their parents had previous experience with the nesting materials used in these experiments. All of the mice, with the exception of the staggerer mutant, exhibited the nest-building behavior. This observation, coupled with other phenotypes expressed in this mutant, suggest the mutation may more generally affect neuroendocrine development and/or regulation rather than be restricted to cerebellar development.

Sagittal knife cuts in the near and far lateral preoptic area-hypothalamus disrupt maternal behaviour in female hamsters

Parasagittal knife cuts with a varied mediolateral position were placed along the medial preoptic-medial anterior hypothalamic continuum (MPOA-MAH) in female hamsters. Near lateral (NL) knife cuts severed mediolateral connections between the MPOA-MAH and the medial forebrain bundle (MFB) while far lateral cuts (FL) were placed more laterally, sparing MPOA-MAH connections with the MFB. Across the knife cut condition, hamsters were either allowed to construct and maintain a food hoard or allowed to feed ad lib but not permitted to hoard. Animals were then tested for maternal behaviours. Both NL and FL cuts disrupted pup-directed behaviours in virgin maternal tests. NL, but not FL cuts severely disrupted nest building. These same animals were then mated and tested for maternal behaviour with their own young. There were no differences among the experimental groups in various maternal behaviours during these tests. Throughout lactation, however, the majority of NL and FL hamsters not permitted to hoard progressively cannibalized their entire litters. NL and FL counterparts with the hoarding opportunity, on the other hand, cannibalized fewer pups and reared healthy, moderate-sized litters that were smaller than those of surgical controls. That FL cuts were just as effective as NL cuts in disrupting pup-directed behaviour suggests that the mediolateral connections of the MPOA-MAH, other than with the MFB, are important for these behaviours.

The role of nest-building activity of gonadotrophin secretions and the reproductive success of ring doves (Streptopelia risoria)

This study was undertaken to investigate the intricate relations between prelaying nest-building activity and preovulatory hormonal changes, and the effects of these events on breeding success. Pairs of ring doves were allowed to go through a complete breeding cycle under four conditions of nest-building opportunity. Nest were self-made, pre-made, pre-made and covered, or removed daily to generate various levels of building activity. Behavioral and hormonal changes were observed throughout the cycle. Blood levels of gonadotrophins were monitored by daily measurements with the method or radioimmunoassay. A depression of follicle-stimulating hormone (FSH) typically was associated with every preovulatory surge of luteinizing hormone (LH); an LH surge not accompanied by a FSH dip was not followed by ovulation. Moreover, the FSH depression was significantly correlated with the level of nest-building activity. These findings led to the proposal that nest-building activity stimulated preovulatory FSH change and, hence, ovulation. The constructed nest in turn appeared to promote incubation behavior. These results are discussed in the context of breeding success.

Delayed deficits in behavior after transection of the olfactory tracts in hamsters

This study compared the effects of transection of the lateral olfactory tracts (LOT) and the accessory olfactory tracts (AOT) in male hamsters on nest building, food piling, and sexual behavior. Autoradiographic tracing of amino acids injected into the olfactory bulbs allowed accurate determination of the location and extent of the transections. Animals with complete bilateral transection of the projections to the amygdaloid targets of the accessory olfactory bulbs and to the main olfactory targets posterior to the olfactory tubercle showed no sexual behavior postoperatively; they did not exhibit extensive genital investigation and did not mount females. In contrast, most of the animals with partial sparing of accessory olfactory bulb efferents to the amygdala did exhibit investigatory and copulatory behaviors postoperatively, although half of the animals with this partial sparing developed delayed deficits in these sexual behaviors. Almost all animals without detectable main olfactory bulb efferents to posterior targets showed delayed deficits in nest building and food piling. This was true whether or not there was partial sparing of accessory olfactory bulb efferents to the amygdala. The animals with LOT transections typically built nests and piled food during the first postoperative week, but stopped building nests and piling food by the fourth postoperative week. Cold stress enhanced these two behaviors in control animals but did not obviate the deficits in experimental animals. Caudally placed transections, which spared a larger portion of the main olfactory projections than rostally placed transections, did not spare more behavior. In fact, the caudally placed transections produced shorter delays in the appearance of deficits in nest building and food piling. These results indicate that the accessory olfactory bulb efferents to the amygdala are more important for sexual behavior than for nest building and food piling in male hamsters. Nest building and food piling are not directly dependent on normal ongoing or sensory evoked activity in the main or accessory olfactory bulb efferents which project through the LOT and AOT. The deficits in nest building and food piling may represent a deterioration in the ability of the animals to organize their living space. The observed delays in the appearance of deficits in behavior may also reflect slow degenerative processes or humoral changes associated with loss of input from the main olfactory bulbs to posterior olfactory target areas, and possibly with interruptions of projections to targets of the accessory olfactory system.

Home-orienting behavior in rat pups: the effect of 2 and 3 generations of rehabilitation following intergenerational malnutrition

In an earlier study in this laboratory, we examined home-orienting ability in rats with histories of intergenerational malnutrition that were rehabilitated postnatally with an adequate protein diet (Galler, 1979). Despite increased size and activity, 1st-generation rehabilitated pups showed no improvement in homing ability when compared to malnourished pups. In the current study, offspring of rats with intergenerational malnutrition were rehabilitated for 2 additional generations and tested for homing ability from postnatal Day 4 through Day 12. The pups rehabilitated for 2 and 3 generations did not perform as well as control pups, even though growth and activity returned to normal levels. Furthermore, the rehabilitated pups failed to demonstrate any preference for the nest on all days of testing; in contrast, control pups favored the nest quadrant by Day 8 of life. No significant improvement was evident on any measure from the 2nd to the 3rd generation of rehabilitation.

The possible role of prolactin in the regulation of nesting behaviour and the secretion of luteinizing hormone in broody bantams

The time spent each day on the nest and the rate of formation of the brood patch before the onset of incubation were measured in bantams (Gallus domesticus) and related to changes in the concentrations of plasma LH and prolactin. The hens spent progressively more time on the nest in the 5 days before the onset of incubation so that by the first day of incubation they were spending more than 90% of their time in this way. The concentration of plasma prolactin increased while that of LH fell on successive days before the onset of incubation: the increase in plasma prolactin preceded the fall in plasma LH by 2 days. The formation of the brood patch closely followed the increase in the concentration of plasma prolactin. In four out of five bantams the increase in nesting behavior was preceded by an increase in the secretion of prolactin. An injection of chicken prolactin antiserum into bantams incubating eggs resulted in a significant (P less than 0.05) increase in the plasma concentration of LH. The observations suggest that, in the bantam, the onset of incubation is initiated by an increase in the secretion of prolactin which also suppresses the secretion of LH.

Maternal behavior following rehabilitation of rats with intergenerational malnutrition. 1. Persistent changes in lactation-related behaviors

Female rats rehabilitated for one or two generations on an adequate level of dietary protein following a history of intergenerational malnutrition were studied during the postnatal suckling period. No recovery occurred after two generations of dietary rehabilitation for most measures of maternal behavior including active nursing, passive nursing, pup-oriented behavior, time spent in the nest or time spent in contact with the young. In contrast, nest quality improved to normal levels after rehabilitation. In addition, growth of pups born to females rehabilitated for one generation was similar to growth of control pups, and in the case of mothers rehabilitated for two generations, growth of offspring exceeded that of the control pups. These results demonstrate variable sensitivity of different maternal behaviors to rehabilitation following a history of intergenerational malnutrition, with lack of normalization of a considerable number of maternal behaviors. Consequently, some of these abnormalities in maternal behavior may result in persistent abnormalities in the behavior of offspring over several generations.

Maternal behavior following rehabilitation of rats with intergenerational malnutrition. 2. Contribution of mothers and pups to deficits in lactation-related behaviors

In a companion paper, we reported the persistence of an increase in active nursing and nursing-related behaviors in rats that were rehabilitated following prolonged intergenerational malnutrition. The rehabilitated litters contained females and pups fed an adequate diet for up to three generations after a history of malnutrition. In the current study, a 2 X 2 cross-over design was used during the lactation period in which rehabilitated mothers suckled rehabilitated pups or well-nourished control pups, and control mothers similarly suckled rehabilitated or control pups. We found that maternal factors were dominant in determining the amount of active nursing, and that pup factors modified the maternal influence on other lactation-related behaviors.

Genetic correlation between two types of nesting in Mus musculus: direct and indirect selection

The genetic correlation between maternal nesting (weight of cotton used in the nest built on the day of parturition) and thermoregulatory nesting (total weight of individual nests built on four consecutive days) was estimated from the correlated response of the former to selection for the latter. The best estimate was rA = 0.58 +/- 0.32, indicating a substantial amount of common genetic influence. Indirect selection seems to have produced a greater response in maternal nesting than could have been achieved by direct selection.

Sensory influences on homing of stunted rat pups

The effects of 2 methods of restricting food intake--large-litter rearing and rotation between lactating and nonlactating females--on sensory factors involved in homing to the nest by rat pups were examined. Homing was observed in the unaltered home cage, when olfactory cues were altered and when visual cues were altered. Stunted animals homed less in the unaltered cage than did well-nourished controls as a result of a maturational delay. Prior to eye opening, stunted animals showed greater disruption of homing when olfactory cues were altered and after eye opening they showed greater disruption when visual cues were altered. These effects could reflect decreased sensitivity, an inability to use alternate cues, or behavioral disruption by novel stimulation. Nonnutritional factors were also found to affect homing as the 2 well-nourished groups differed in their behaviors. These differences appeared to be due to animals reared in small litters maturing more slowly than animals rotated between females.

Response to divergent selection for nesting behavior in Mus musculus

Replicated bidirectional selection (with control lines) for nest-building behavior in Mus musculus, where nesting scores consisted of the total weight of cotton pulled through the cage lid during four days of testing, yielded an eight-fold difference between high and low lines after 15 generations of selection. The overall realized heritability pooled across lines and replicates was 0.18 +/- 0.02 (0.15 +/- 0.03 for high nesting scores and 0.23 +/- 0.04 for low nesting scores), or 0.28 +/- 0.05 when adjusted for within-family selection. Across the 15 generations and the entire experiment, average body weight and number of infertile matings increased, while average litter size decreased, although these changes were not consistent across lines. Inbreeding could account for average decreases in the fertility traits, but there was also a correlated response to selection, since both high lines showed increased litter size and decreased infertile matings.

Effects of small medial preoptic area lesions on maternal behavior: retrieving and nest building in the rat

Previous studies in rats have demonstrated that large lesions in the medial preoptic area (MPOA) disrupt all aspects of maternal behavior. In the present study, small bilateral electrolyte lesions in the MPOA of lactating females abolished nest building and retrieving components of maternal behavior while crouching and nursing were unaffected. Animals which failed to show retrieval and nest building behaviors tended to have a greater area of lesion within the more dorsal part of the MPOA. Although the dorsal MPOA may play a role in the maintenance of the active components of maternal behavior, i.e. nest building and retrieving, another critical factor in determining which components of maternal behavior are disrupted may be the size of the lesion. As one increases the area of damaged tissue there is also an accompanying increase in the components of maternal behavior which are disrupted. No correlation was found between damage to the Sexually Dimorphic Nucleus of the preoptic area and retrieving and nest building.

Hoarding behavior of AKR, C57BL/6 mice and their F1 in their home living space: an automatic recording technique

Earlier genetic analysis of food hoarding behavior in mice used test situations in which animals were allowed to hoard food only during short time periods. This paper describes a technique to measure food hoarding over long time periods. Small discs of standard food are equipped with a steel clip and each passage of a mouse bringing such a food disc from the food search enclosure to the nest is detected by an electromagnetic sounding lead connected to a pen recorder. Preliminary results show that female mice begin to hoard earlier than males; one of the two reciprocal F1 has a shorter latency to hoard than the other one. Results also show differences between two parental inbred strains and their reciprocal F1 for the light-dark distribution of hoarding.

Acute elevation of the heat load of mother rats curtails maternal nest bouts

Elevation of the rate of rise of ventral, core, or preoptic area temperature in mother rats while they were nesting with their offspring curtailed nest-bout durating. In addition, the naturally occurring curtailment of nest bouts that occurs in mothers caring for large pups was found to be accompanied by an elevated rate at which maternal temperature rose over the course of a nest bout. These data are consistent with the suggestion that nest-bout duration is thermally limited.