The medial preoptic area, necessary for adult maternal behavior in rats, is only partially established as a component of the neural circuit that supports maternal behavior in juvenile rats.

To determine whether the neurons of the medial preoptic area (MPOA) are necessary for pup-induced maternal behavior (MB) in juvenile and adult rats, subjects received bilateral injections of the neurotoxin N-methyl-{d}-aspartic acid into the MPOA. Controls were intact or were sham treated by surgical placement of the syringe barrel. The rats were then induced into MB by constant pup exposure. Starting at 27 (juvenile) or 60 (adult) days of age, rats were tested for MB for 12 consecutive days. After histological analysis, rats were categorized as having either large or small lesions of the MPOA. In juveniles, large lesions of the MPOA blocked retrieval and impaired nest-building, but crouching behavior was unaffected; small lesions had no effect on MB. In contrast, in adults, large or small lesions severely impaired all components of MB. The results suggest that in juvenile rats, the role of the MPOA neurons in MB is only partially established, whereas by 60 days of age, the unsubstitutable role of the MPOA in the neural circuit that mediates MB is fully established. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dopamine D? receptor stimulation of the nucleus accumbens or the medial preoptic area promotes the onset of maternal behavior in pregnancy-terminated rats.

There is good evidence that interference with the mesolimbic dopamine (DA) system results in impaired maternal responding in postpartum female rats. However, whether activation of the mesolimbic DA system is capable of promoting maternal behavior has not been investigated. This study examined whether increasing DA activity in various brain regions of pregnancy-terminated, naive female rats would stimulate the onset of maternal behavior. Experiments 1 and 2 examined the effects of microinjection of various doses (0, 0.2, or 0.5 μg/0.5 μl/side) of a D? DA receptor agonist, SKF 38393, or a D? DA receptor agonist, quinpirole, into the nucleus accumbens (NA) on latency to show full maternal behavior, and Experiment 3 determined the effects of SKF 38393 injection into a control site. Finally, because the medial preoptic area (MPOA) is also important for maternal behavior, receives DA input, and expresses DA receptors, the authors examined whether microinjection of SKF 38393 into MPOA was capable of stimulating the onset of maternal behavior. Results indicated that microinjection of SKF 38393 into either the NA or the MPOA facilitates maternal responding in pregnancy-terminated rats. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Opioids and sexual behavior of male rats: Involvement of the medial preoptic area.

Local infusion of β-endorphin (β-END) into the medial preoptic area (MPOA) dose-dependently impaired the gating of the copulatory response and the execution of the sexual performance of sexually experienced, intact male rats. Local naloxone treatment prevented the impairment of the sexual response by β-END, but failed to facilitate unimpaired copulation. Local infusion into the MPOA of equimolar doses of α-endorphin, dynorphin-A-(1-17) or met-enkephalin were less effective than β-END. It is suggested that endogenous opioid systems in the MPOA are normally quiescent, and increased activity may be related to disrupted or inhibited male sexual behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effects of D1 or D2 dopamine receptor antagonism in the medial preoptic area, ventral pallidum, or nucleus accumbens on the maternal retrieval response and other aspects of maternal behavior in rats.

The medial preoptic area (MPOA), ventral pallidum (VP), and nucleus accumbens (NA) receive dopaminergic afferents and are involved in maternal behavior. Experiments investigated whether dopamine (DA) receptor antagonism in NA disrupts maternal behavior, determined the type of DA receptor involved, and investigated the involvement of drug spread to VP or MPOA. Injection of SCH 23390 (D1 DA receptor antagonist) into NA of postpartum rats disrupted retrieving at dosage levels that were ineffective when injected into MPOA or VP. Motor impairment was not the cause of the deficit. Injection of eticlopride (D2 DA receptor antagonist) into NA or VP was without effect. Results emphasize the importance of DA action on D1 receptors in NA for retrieval behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sexual reinforcement is blocked by infusion of naloxone into the medial preoptic area.

Determined whether infusions of naloxone into specific brain sites can block sexual reinforcement as evaluated with the conditioned place preference procedure. Methylnaloxonium (5 μg/cannula) was infused bilaterally either into the medial preoptic area (MPOA) or into the nucleus accumbens (NAC) of sexually experienced male rats. The MPOA was chosen because it is important for sexual behavior, and several opioid peptides have been shown to modify sexual behavior when infused there. The NAC appears to be a critical structure for drug-induced reward. Methylnaloxonium blocked place preference produced by ejaculation after infusion into the MPOA without affecting sexual behavior. Infusion of the antagonist into the NAC did not reduce the reinforcing properties of ejaculation. Data suggest that the MPOA may be a site where sexual reward is produced. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

In utero cocaine, discriminative avoidance learning with low-salient stimuli and learning-related neuronal activity in rabbits (Oryctolagus cuniculus).

Daily injections of cocaine administered to pregnant rabbits (Oryctolagus cuniculus) throughout gestation were associated with neural and behavioral changes during development and in adulthood, including altered neuron structure and function in areas receiving dopaminergic projections and retarded Pavlovian eyeblink conditioning with low-salient conditional stimuli. Studies of discriminative avoidance learning have shown changes in learning-related cingulothalamic neuronal activity, but no behavioral learning impairment in cocaine-exposed offspring. Here, low-salient stimuli were used during discriminative avoidance conditioning. Impairments early in behavioral acquisition were found, as well as alterations of anterior cingulate and medial prefrontal cortical, medial dorsal thalamic, and amygdalar neuronal response profiles and learning-related neuronal activity. These results elucidate the neural processes, impaired by prenatal cocaine, that support conditioning with low-salient stimuli. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Serotonin impairs copulation and attenuates ejaculation-induced glutamate activity in the medial preoptic area.

The medial preoptic area (MPOA) is critical for male sexual behavior. Glutamate is released in the MPOA of male rats during copulation, and increasing glutamate levels by reverse dialysis of glutamate uptake inhibitors facilitates mating. Conversely, increased release of serotonin (5-HT) inhibits sexual behavior. In both rats and men, selective serotonin reuptake inhibitors (SSRIs) impair erection, ejaculation, and libido. Here we reverse-dialyzed 5-HT through concentric microdialysis probes in the MPOA of male rats; concurrently we collected 2-min samples for analysis of glutamate and measured sexual behavior. Sexual activity, and especially ejaculation, increased levels of glutamate in the MPOA. However, reverse dialysis of 5-HT into the MPOA impaired ejaculatory ability and attenuated glutamate release. Implications of these results for impairment of sexual behavior that results from administration of SSRIs are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hyperostosis in meningiomas: MR findings in patients with recurrent meningioma of the sphenoid wings

The median and dorsal (MR and DR) raphe nuclei are the origin of serotonin (5-HT)-containing neurons that innervate the forebrain. Neurons originating in the medial and lateral habenula provide an extensive afferent input to the midbrain that could serve as a negative feedback circuit. The present study was undertaken to establish whether intact habenula nuclei are required to observe the depressant effects of cocaine on the neural activity of 5-HT somata in the DR. To this end, the spontaneous activity of DR 5-HT neurons was assessed in male rats that had previously received bilateral radiofrequency lesions of the habenula complex either 1-4 h (short term) or 7 days (long term) prior to extracellular recordings of single 5-HT neurons of the DR. In rats with short-term lesions, the inhibitory response to cocaine was significantly attenuated. The mean dose to inhibit activity by 50% (ID50) was increased from 0.68 mg/kg in controls to 2.5 mg/kg in lesioned rats. Short-term habenula lesions also significantly decreased the numbers (but not the firing rates) of 5-HT neurons encountered in the DR. In contrast, the dose-response to cocaine as well as the numbers and firing rates of 5-HT neurons found in rats with long-term habenula lesions did not differ from controls. These results suggest that the inhibitory effects of cocaine on DR 5-HT neuronal activity depend in part on the ability of cocaine to affect habenula control of raphe 5-HT function.     

The effects of olfactory and somatosensory desensitization on Fos-like immunoreactivity in the brains of pup-exposed postpartum rats.

Fos-like immunoreactivity (fos-lir) was examined in sites within the "maternal circuit" in postpartum female rats that received various sensory desensitizations and were exposed to pups for 1 or 2 hr. Neither olfactory bulbectomy nor thelectomy (nipple removal) significantly reduced the fos-lir in the anterior medial preoptic area (MPOA), although reductions following bulbectomy in medial amygdala did occur. Peripherally induced hyposmia by ZnSo? reduced fos-lir in the olfactory structures (olfactory bulbs, piriform cortex, and olfactory tubercle), in medial and cortical nuclei of the amygdala, but not in anterior MPOA. Application of the topical anesthetic Emla to the ventrum only reduced fos-lir in the somatosensory cortex. Combined olfactory and ventral desensitizations produced marginal reductions in posterior MPOA. It is suggested that the MPOA is primarily involved as part of the effector system in the expression of the behavior. In contrast, the amygdala is involved in processing sensory cues received from pups during dam-litter interactions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Mating activates NMDA receptors in the medial preoptic area of male rats.

Studies have emphasized the role of the medial preoptic area (MPOA) as an important site for the regulation of male sexual behavior. Indeed, ablations of the MPOA impair sexual behavior, whereas stimulation of the MPOA enhances behavior. Furthermore, neural activity in the MPOA increases with mating. The current study tested the hypothesis that activation of N-methyl-D-aspartate (NMDA) receptors occurs in MPOA neurons and is essential for the expression of male sexual behavior in rats. Results indicate that nearly all MPOA neurons that expressed Fos following mating also contained the NR1 subunit of NMDA receptors. Furthermore, mating increased phosphorylation, thus activation, of NR1 in the MPOA. Additionally, blocking NMDA receptors significantly decreased mating-induced Fos expression and mating-induced phosphorylation of NMDA receptors and impaired male sexual behavior. These results provide evidence that mating activates NMDA receptors in the MPOA and that this activation is important for the expression of male sexual behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Wake-Promoting Actions of Medial Basal Forebrain β? Receptor Stimulation.

The locus coeruleus-noradrenergic system exerts an activating influence on forebrain neuronal and behavioral activity states, in part, through the actions of noradrenergic β receptors located within the medial septal (MS) and medial preoptic (MPOA) areas. The current study examined the extent to which β? receptors located within these medial basal forebrain regions modulate behavioral state. In this study, the sleep-wake effects of microinfusion of the β? agonist, clenbuterol, into the MS and MPOA were examined. Clenbuterol infusion into both MS and MPOA elicited a dose-dependent increase in time spent awake. These observations indicate that medial basal forebrain β? receptors participate in the noradrenergic-dependent modulation of behavioral state. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Inhibition of nitric oxide synthase within the medial preoptic area impairs pup retrieval in lactating rats.

Central suppression of nitric oxide (NO) production by administering 250 μg of Nitrow-L-Argenine Methyl Ether (L-NAME), an inhibitor of NO synthase, into the 3rd ventricle disrupts both pup retrieval and maternal aggression in postpartum rats. In these studies, the authors examined the ability of varying doses of L-NAME to produce these effects on maternal behavior. Doses of L-NAME that were shown to be ineffective when injected into the 3rd ventricle were administered bilaterally into the medial preoptic area (MPOA) of rats on Day 4 postpartum. To assess the specificity of L-NAME's effect within the MPOA, the authors bilaterally injected Nitrow-D-Argenine Methyl Ether (D-NAME), an inactive isomer of L-NAME, into the MPOA. When administered intracerebroventricularly, the 2 highest doses of L-NAME used, 250 μg and 200 μg, disrupted retrieval behavior and maternal aggression. Bilateral injections of L-NAME into the MPOA at doses of 20 μg and 40 μg/side also disrupted pup retrieval, and D-NAME injections into the MPOA had no effect on the maternal behaviors measured. All rats in these experiments showed normal maternal behavior 24 hr after drug administration. These results suggest that NO acts within the MPOA to facilitate retrieval behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A Nitric Oxide Synthesis Inhibitor in the Medial Preoptic Area Inhibits Copulation and Stimulus Sensitization in Male Rats.

Dopamine in the medial preoptic area (MPOA) facilitates copulation in male rats, and nitric oxide (NO) regulates basal and female-stimulated MPOA dopamine release. Microinjection of L-nitro-arginine methyl ester (L-NAME, an NO synthesis inhibitor) into the MPOA blocked copulation in naive rats and impaired copulation in sexually experienced males. In other naive rats, L-NAME or saline was microinjected into the MPOA before each of 7 daily exposures to a receptive female placed over their cage. In a drug-free test on Day 8, copulation by L-NAME-treated rats was similar to that of unexposed controls and was impaired relative to saline-treated males. Therefore, NO in the MPOA is important for copulation and stimulus sensitization in male rats. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

N-methyl-D-aspartate receptor-dependent plasticity within a distributed corticostriatal network mediates appetitive instrumental learning.

The effect of microinfusion of the N-methyl-{d}-aspartate (NMDA) antagonist 2-amino-5-phosphonopentanoic acid (AP-5) into the amygdala, medial prefrontal cortex, and dorsal and ventral subiculum on acquisition of a lever-pressing task for food in rats was examined. Serial transmission between the basolateral amygdala and nucleus accumbens core was also examined in an asymmetric infusion design. AP-5 administered bilaterally into either the amygdala or medial prefrontal cortex markedly impaired learning, whereas administration into the dorsal or ventral subiculum had no effect. Unilateral infusion of AP-5 into either the nucleus accumbens core or amygdala was also sufficient to impair learning. These data provide novel evidence for NMDA receptor-dependent plasticity within corticostriatal networks in the acquisition of appetitive instrumental learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Additive wake-promoting actions of medial basal forebrain noradrenergic α1- and β-receptor stimulation.

The locus coeruleus-noradrenergic system exerts an activating influence on forebrain neuronal and behavioral activity states, in part through the actions of noradrenergic β-receptors in the medial septal (MS) and medial preoptic (MPOA) areas. MPOA α1-receptors exert similar wake-promoting actions. The current study examines the influence of α1-receptors located within MS on sleep-wake state. In addition, the extent to which α1- and β-receptors located within MS and MPOA interact in the modulation of behavioral state was investigated by examining the effects of individual or combined infusion of α1- and β-agonists into these regions. Results show that al-receptors located within MS exert wake-promoting actions. Within both MS and MPOA, additive wake-promoting actions were observed with α1- and β-receptor stimulation, the sum of which contributes to the overall arousal state of the animal. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dopamine D1 and D2 Receptor Antagonism in the Preoptic Area Produces Different Effects on Maternal Behavior in Lactating Rats.

The preoptic area (POA) is critical for maternal behavior in rats but little is known about what neurotransmitters released here influence maternal responding. POA infusion of 10 μg (but not 2 μg) of the dopamine D1 receptor antagonist SCH-23390 greatly impaired retrieval and licking of pups but not other maternal or nonmaternal behaviors in lactating rats. In contrast, POA infusion of 10 μg (but not 2 μg) of the D2 receptor antagonist raclopride facilitated nursing but did not affect oral maternal behaviors. SCH-23390 in the medial hypothalamus tended to impair licking but not retrieval. Raclopride in the medial hypothalamus had no effects. Therefore, D1 and D2 receptor activity, particularly in the POA, is important for regulating different maternal behaviors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Oxytocin activates the postpartum onset of rat maternal behavior in the ventral tegmental and medial preoptic areas.

Oxytocin binding (Bmax) was found to be higher in the ventral tegmental area (VTA) and the medial preoptic area (MPOA) at midparturition compared with Pregnancy Days 15–27 or Postpartum Days 5–7 in rat dams. Pup retrieval and assuming a nursing posture over pups were blocked in parturient dams by infusions of an oxytocin antagonist into the VTA or MPOA and by infusions of a vasopressin (V?) antagonist into the MPOA. These results implicate oxytocin in the VTA and MPOA and vasopressin in the MPOA, as well as a parturition-associated rise in oxytocin binding in these sites in the postpartum activation of maternal behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

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)     

Drug seeking under a second-order schedule of reinforcement depends on dopamine D? receptors in the basolateral amygdala.

Drug seeking under the control of drug-associated stimuli and its reinstatement after extinction can be decreased by systemic administration of dopamine D? receptor antagonists. It is demonstrated that responding by rats on the active lever for cocaine under a 2nd-order schedule of reinforcement, under which responding is maintained by response-contingent cocaine-paired conditioned reinforcers, is markedly attenuated by infusion of the dopamine D? receptor antagonist SB-277011-A into the amygdala (2 and 4 μg/0.3 μl). By contrast, infusions of SB-277011-A into the shell subregion of the nucleus accumbens and also into the dorsal striatum were without effect. These results show that the control over drug seeking by conditioned reinforcers depends on D? receptor-dependent dopamine transmission in the amygdala. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Central administration of cocaine produces age-dependent effects on behavior in the fetal rat.

Rat fetuses were exposed to cocaine, lidocaine, or saline on Gestational Day 20 or 21 to provide information about cocaine effects on behavior during prenatal development. Cocaine was administered into the cisterna magna of individual fetal subjects to restrict effects to the CNS. Behavioral effects of cocaine were compared with lidocaine to help distinguish the effects of cocaine on monoamine systems in the brain from its properties as a local anesthetic. Cocaine promoted 3–5 fold increases in fetal motor activity in the absence of explicit sensory stimulation, in contrast to the slight suppressive effects of lidocaine. Cocaine and lidocaine also reduced coordinated behavioral responses to an artificial nipple. The behavioral effects of cocaine administered into the CNS of fetal subjects suggest specific mechanisms of action on developing neural and behavioral systems in the late prenatal period. (PsycINFO Database Record (c) 2010 APA, all rights reserved)