Medial preoptic area and maternal behavior in the female rat.

Reports results of 3 experiments with a total of 92 postpartum lactating female Wistar rats. Medial preoptic area lesions severely disrupted maternal behavior, whereas lesions of the stria terminalis and medial cortico-hypothalamic tract knife cuts were without effect. Parasagittal knife cuts that severed the mediolateral connections of the preoptic-anterior hypothalamic continuum also severely disrupted maternal behavior. The lesions and knife cuts which disrupted maternal behavior had no effect on female sexual behavior. It is concluded that the medial preoptic area and its lateral connections are essential for the normal display of maternal behavior in postpartum lactating female rats. Evidence also indicates that independent neural mechanisms for the control of maternal behavior and sexual behavior exist within the hypothalamus of female rats. (46 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of lesions in the basolateral amygdala on fluid intake in the rat.

Conducted 6 experiments with 33 rats with bilateral lesions in the lateral amygdaloid region and 22 intact controls. Drinking response to hypertonic saline, a cellular thirst stimulus, and to isoproterenol, probably an extracellular thirst stimulus, was normal in lesioned Ss. The overnight water intake of the lesioned Ss was a little higher than normal. However, the lesioned Ss showed a major impairment in learning to avoid ingesting a poisonous solution of LiCl when they were thirsty and an increased preference of 25% sucrose in a 2-bottle sucrose-water test. It is concluded that the basolateral region of the amygdala is involved in the effects of previous experience on drinking and not primarily in the cellular or extracellular controls of drinking. (25 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of sequential preoptic and mammillary lesions on male rat sexual behavior.

Observed the sexual behavior of 52 male Sprague-Dawley rats prior to and following bilateral medial preoptic, unilateral medial preoptic, bilateral posterior preoptic, bilateral mammillary, and sham lesions. Bilateral medial preoptic lesions and mammillary lesions were made either simultaneously or sequentially within the same Ss in separate groups. Mammillary lesions had no effect on sexual behavior. Complete destruction of the medial preoptic area made prior to, simultaneous with, and following mammillary lesions completely abolished mating behavior. Partial destruction of the medial preoptic area increased mount and intromission latencies and slightly increased ejaculation latency. Results suggest that since there was no change in the postejaculatory-refractory interval, the medial preoptic area mediates sexual arousal but apparently is not involved in a copulatory-ejaculatory mechanism. (32 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sensorimotor syndrome produced by lesions of the amygdala and lateral hypothalamus.

Experimented with 7 male Long-Evans hooded rats. Small unilateral lesions of the amygdala, lateral hypothalamus, or nearby structures resulted in an inability to orient and localize, by an appropriate movement of the head, stimuli in the contralateral visual and somatosensory fields. This is neither a primary sensory nor motor deficit. Conditioning experiments revealed that the linkage between contralateral sensory and motor fields has been disrupted, possibly reflecting damage to fibers which connect sensory and motor areas within a hemisphere. This sensorimotor syndrome can account for the placidity and decreased aggressive, social, and feeding behaviors commonly observed following lesions of these areas. (15 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Medial preoptic area oxytocin and female sexual receptivity.

Intracerebroventricular (icv) administration of the nonapeptide oxytocin (OXT) increases sexual receptivity in female rats. The medial preoptic area (MPOA) appeared to be the most sensitive brain area to the facilitative effects of OXT. Bilateral infusions of 100 ng of OXT into the MPOA significantly elevated lordosis quotients in overiectomized (OVX), estrogen-treated rats. This dose of OXT was ineffective when infused icv or into the ventromedial hypothalamus, mesencephalic central gray, or ventral tegmental area. A 500-ng dose of OXT significantly elevated lordosis responding when infused icv, corresponding with our previous findings. Mounting by males significantly increased immunoreactive levels of OXT and decreased the number of OXT immunostaining cells in the MPOA of sexually receptive rats pretreated with estrogen and progesterone. The MPOA is a primary site of the OXT facilitation of sexual receptivity where OXT may be released during mating. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Temperature regulation and salivation following preoptic lesions in the rat.

Investigated whether the preoptic's thermoregulatory deficit might be a reflection of a general salivary deficit. 3 experiments were conducted with adult female Sherman albino rats. Results show that Ss with preoptic lesions quickly become hyperthermic under extreme heat stress. They do not salivate in response to heat as intact Ss do and thus cannot employ this animal's most effective means of evaporative heat loss, saliva spreading. However, if salivation is pharmacologically stimulated, lesioned Ss are able to resist hyperthermia by spreading the saliva. Further, given access to a lever which they can press in order to obtain exogenous coolant from a shower bath, Ss with lesions press more frequently with the higher, more stressful, ambient temperatures than with the more moderate ones, hence maintaining normothermia. Data suggest that rats with preoptic lesions do not lack the capacity for thermoregulation, but only an essential physiological tool, saliva. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of sexually dimorphic medical preoptic area of the hypothalamus in the sexual behaviour of male and female rats

The human placental alkaline phosphatase (PLAP) gene was analysed for its utility as a histochemically detectable reporter gene in transgenic mice. A reporter gene was made by linking the PLAP structural gene to an enhancer-promoter element from the human beta-actin gene. This gene was inserted into the mouse genome by transfection of embryonic stem cells, and by microinjection of fertilized eggs. Histochemical staining showed that the transgene was uniformly expressed in four of four stable ES cell lines, and in all ten tissues examined from adult animals from five lines of transgenic mice. Non-transgenic cells did not stain. These results suggest that the human PLAP gene will be of utility in studies requiring phenotypic marking of cells in tissues of mice.     

Self-stimulation of preoptic and lateral hypothalamus during behavioral thermoregulation in the albino rat.

Explored self-stimulating behavior in 5 male albino rats under ambient temperatures of 2, 12, 25, and 35.C while radiant-heat reinforcement was concurrently available. Preoptic self-stimulation was accompanied by hypothermia even at neutral temperatures, and in the cold, preoptic self-stimulation behavior was maintained alternating with the use of the heat-lamp lever. Conversely, self-stimulation of the lateral hypothalamus produced hyperthermia at neutral temperatures. In the cold, lateral hypothalamic self-stimulation was suppressed, although maintained sufficiently to preserve normal body temperatures without use of the heat lamp. High-temperature stress suppressed both preoptic and lateral hypothalamic self-stimulation. The interpretation suggests that electrical stimulation of the preoptic area signals a pseudowarmth state which results in activation of heat-loss mechanisms. (15 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of neurochemical lesions of the preoptic area on male sexual behavior in the Japanese quail

Two experiments were carried out during which the noradrenergic neurotoxin, 5-amino-2,4-dihydroxy-alpha-methylphenylethylamine (5-ADMP) was applied to the brain of quail in order to evaluate the role of the noradrenergic system in the control of male copulatory behavior. In the first experiment, the ICV injection of 5-ADMP slightly enhanced the sexual behavior observed in testosterone (T)-treated castrated male quail. This brings additional support to the notion that norepinephrine tonically inhibits male copulatory behavior in quail. In the second experiment, 5-ADMP implanted directly into the preoptic area disrupted the restoration by T of copulatory behavior in castrated quail and, at the same time, produced a brain lesion that partly destroyed the sexually dimorphic medial preoptic nucleus, a previously established site of T action on behavior. These lesions produced by a high (presumably too high) concentration of neurotoxin provided an independent confirmation of effects previously observed after electrolytic lesions. Correlation analyses also confirmed that the medial part of the POM just rostral to the anterior commissure is more closely associated with copulatory behavior and may, therefore, represent a key center for steroid action on this behavior.     

Dopamine release in the medial preoptic area of female rats in response to hormonal manipulation and sexual activity.

Dopamine (DA) is responsive to hormonal manipulations and has been implicated in the regulation of female rat sexual behavior. In the present studies, extracellular DA levels were assessed in the medial preoptic area (MPOA) of ovariectomized female rats in response to exogenous ovarian hormones and during sexual activity. In female rats primed with a low dose of estradiol benzoate (2 μg), but not with a higher dose (20 μg), a 500-μg progesterone injection increased extracellular DA and facilitated copulatory behavior. Extracellular DA levels in the MPOA were further augmented during sexual interactions with a male rat in a nonpacing copulatory chamber by either perineal or vaginal stimulation. However, in a pacing chamber, DA efflux did not increase, although the metabolites rose significantly during copulation. Together, these findings suggest that extracellular DA in the MPOA responds to the hormonal state of the female rat and may contribute to her expression of sexual behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of basolateral amygdala lesions on taste aversions produced by lactose and lithium chloride in the rat.

In Exp I, 24 intact male Lister rats were given either lactose or sucrose solutions. Although on 1st exposure they readily consumed lactose, its ingestion produced a conditioned taste avoidance (CTA) that was partly extinguished by repeated sucrose exposure after lactose conditioning. In Exp II, 8 Ss with large bilateral electrolytic lesions of the basolateral amygdala and 10 with either sham or no operations were given 2 pairings of saline with LiCl injections (upper gastrointestinal tract discomfort) and, in a separate condition, access to high levels of lactose (lower gastrointestinal tract discomfort). CTAs were measured both by 2-bottle tests and by video recordings of orofacial and somatic responses. The lesions attenuated LiCl-induced but not lactose-induced CTA, results demonstrating that a CTA can occur without the basolateral amygdala. Findings suggest that aversions based on distaste can be distinguished from avoidances based on danger, not only in terms of orofacial responses but also in terms of their neuroanatomical substrate. (31 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Medial preoptic area and onset of maternal behavior in the rat.

Three experiments examined whether the medial preoptic area (MPOA) is involved in the onset of maternal behavior in the rat. Exp I, with 54 female Charles River CD rats, investigated whether estradiol benzoate (EB) acts on the MPOA to facilitate the onset of maternal behavior in 16-day pregnant, hysterectomized, and ovariectomized Ss. When given EB implants in the MPOA, these Ss had significantly shorter latencies for the onset of maternal behavior than those implanted with cholesterol in the MPOA or with EB in the ventromedial hypothalamus, in mammillary bodies, or under the skin. Exp II, with 62 Ss, showed that estrogen-induced prolactin release was not involved in this facilitation. Exp III, with 35 Ss, showed that MPOA lesions disrupted the onset of maternal behavior induced by pup stimulation in virgin females. (11/2 p ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of reinforcement omission on rats with lesions in the amygdala.

Trained 12 male Wistar rats with bilateral lesions in the amygdala to barpress on an FI schedule of reinforcement. During test trials, when reinforcement was occasionally omitted, response rates of 12 controls increased in the subsequent interval, whereas lesioned Ss showed no significant change. In Exp II Ss received fixed-ratio reinforcement on 1 lever, which was followed by a time-out period and fixed-ratio reinforcement on a 2nd lever. Results indicate that after reinforcement was withheld Ss with damage in the amygdala did not increase responding in the subsequent time-out period, whereas controls showed significantly higher rates. Differential latencies to initiation of response after nonreinforcement were also found. The deficits following brain damage are attributed to a reduction in nonreinforcement-induced frustration. (20 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of cerebellar lesions on activity, social interactions, and other motivated behaviors in the rat.

In a total of 36 male rats, lesions of the cerebellar fastigial nucleus, but not lateral nuclear lesions or cerebellar cortical lesions, resulted in significant reductions in activity, open-field exploratory behavior, and social interactions. These deficits showed no recovery over a 4-wk testing period and were not related to the motor effects of the lesions. Other motivated behaviors (e.g., eating, grooming, gnawing, and pain responsiveness) were minimally affected. Results suggest the existence of 2 separate fastigial output pathways to neurobehavioral substrates: (a) the direct fastigio-bulbar pathway, which mediates the eating, grooming, and gnawing behaviors elicited by fastigial stimulation, and (b) the ascending fastigial projection to limbic structures, which may mediate fastigial influences on activity and social interaction. (43 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Distribution and regulation of aromatase activity in the ram hypothalamus and amygdala

The role of nucleoside transport in ischemia-reperfusion injury and arrhythmias has been well documented in various animal models using selective blockers. However, clinical application of nucleoside transport inhibitors remains to be demonstrated in humans. It is not known whether human heart has nucleoside transport similar to that of animals. The aim of this study is to pharmacologically identify the presence of nucleoside transport binding sites in the human myocardium compared to animals. Myocardial tissue was obtained from guinea pig left and right ventricle, canine left ventricle, human intraoperative right atrium and human cadaveric right atrium and right and left ventricles. Myocardial preparations were obtained from tissue samples after homogenized and a differential centrifugation. Equilibrium binding assays were performed using [3H]-p-nitrobenzylthioinosine (NBMPR) at room temperature in the presence or absence of non-radioactive NBMPR or other nucleoside transport blockers such as p-nitrobenzylthioguanosine dipyridamole, lidoflazine, papaverin, adenosine and doxorubcine. From saturation curves and inhibition kinetics, we determined the relative maximal binding (Bmax) and dissociation constant (Kd) of [3H]-NBMPR binding of human myocardial preparations. Results demonstrated that the fresh human myocardial preparations have a specific binding site for NBMPR with a Bmax of 283+/-32 fmol/mg protein and Kd of 0.56+/-0.12 nM. These values are lower than those obtained from guinea pigs (Bmax = 1440+/-187 fmol/mg protein and Kd = 0.21+/-0.03 nM) and canine atrium (Bmax 594+/-73 fmol/mg protein, and Kd = 1.12+/-0.22 nM). Displacement kinetics studies revealed the relative potencies (of certain unrelated drugs as follow: p-nitrobenzylthioguanosine > dipyridamole > lidoflazine > pavaverine > Diltazam > adenosine > doxyrubicin. It is concluded that human myocardium contains an active nucleoside transport site which may play a crucial role in post-ischemic reperfusion-mediated injury in a wide spectrum of ischemic syndromes.     

Effects of amygdala central nucleus lesions on blocking and unblocking.

The effects of lesions of the amygdala central nucleus (CN) on blocking and unblocking of appetitive Pavlovian conditioning were examined in 2 experiments with rats. In both lesioned and unlesioned rats, prior pairing of one CS with a food unconditioned stimulus/stimuli (UCS) blocked the acquisition of conditioning to a 2nd CS when a compound of both stimuli was paired with that same UCS. If the value of the UCS was increased or decreased when the 2nd CS was added, unlesioned rats acquired substantial conditioning to the 2nd cue (unblocking). Unblocking occurred in lesioned rats only when the UCS value was increased. In both lesioned and unlesioned rats, unblocking was prevented if the compound cue was paired with the original UCS prior to the change in UCS value. These data suggest that the CN is involved in increasing attention to signals for significant events but not in tuning out redundant cues. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Levels of serum steroids, aromatase activity, and estrogen receptors in preoptic area, hypothalamus, and amygdala of B6D2F1 male house mice that differ in the display of copulatory behavior after castration

Most male B6D2F1 hybrid house mice continue to copulate after castration (continuers), whereas others do not (noncontinuers). Copulation in continuers appears estrogen dependent. Serum testosterone (T), 17 beta-estradiol (E2), and dihydrotestosterone (DHT), as well as aromatase activity (AA) and estrogen receptor (ER) levels in preoptic area (POA), hypothalamus (HYP), and amygdala (AM) were measured to determine if continuers and noncontinuers differ in estrogen physiology. In general, continuers and noncontinuers did not differ in serum steroid levels, AA, or ER levels. Castration reduced AA in the POA, HYP, and AM. Castration did not affect nuclear ER levels in the POA and HYP but reduced nuclear ER in AM. The data demonstrate that castrated B6D2F1 male mice continue to be under the influence of circulating nongonadal E2 that is important for copulation.     

Some observations on the preference deficits produced by lateral preoptic lesions in the rat.

Conducted 4 experiments with a total of 20 female albino Sherman rats which show that, following water deprivation, Ss with lateral preoptic (LPO) damage lost the normal preference for glucose solutions. Food deprivation reinstated the preference. This dependency was specific to sweet-tasting fluids, and the deficit persisted even when thirst was alleviated prior to the preference test. Such Ss would drink sweet solutions in response to intravascular fluid depletion, but they were deficient in response to sweet solutions under nondeprived conditions. This last finding in particular suggests that hunger and palatibility, as determinants of the response to sweet solutions, may be dissociated by LPO damage. (18 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)