Receptor Densities In Brain Regions Research Articles

Hormones and visual attention to sexual stimuli in older men: an exploratory investigation

Background Testosterone is associated with sexual desire and performance in men, but little is known about cognitive mechanisms underlying this relationship. Even less is known about the influence of estradiol, despite its production from testosterone, and high receptor density in brain regions related to male sexual behavior. Method We used eye-tracking to compare men’s visual attention to images of fully clothed (i.e. neutral) and minimally clothed (i.e. sexy) models in three groups: androgen-deprived (n = 6) and not androgen-deprived with prostate cancer (n = 11), and healthy controls (n = 7). We also assessed effects of serum testosterone, estradiol, and sex hormone-binding globulin levels. Results We found no group effect for fixations to sexy compared to neutral images, and no influence of testosterone on either total fixations, or proportion of fixations to sexy images. In contrast, we found that sex hormone binding globulin positively predicted total fixations, and estradiol positively predicted proportion of total fixations on sexy images--regardless of androgen treatment status. Conclusion Our results suggest that visual attention to sexual stimuli in men may be significantly affected by hormones. This has potential implications for clinical populations that experience sexual side effects, such as prostate cancer patients on androgen deprivation therapy.

Dietary Galacto-Oligosaccharides and Resistant Starch Protect Against Altered CB1 and 5-HT1A and 2A Receptor Densities in Rat Brain: Implications for Preventing Cognitive and Appetite Dysfunction During a High-Fat Diet.

A high-fat, but low-fiber, diet is associated with obesity and cognitive dysfunction, while dietary fiber supplementation can improve cognition. This study examines whether dietary fibers, galacto-oligosaccharides (GOS) and resistant starch (RS), could prevent high-fat (HF)-diet-induced alterations in neurotransmitter receptor densities in brain regions associated with cognition and appetite. Rats are fed a HF diet, HF diet with GOS, HF diet with RS, or a low-fat (LF, control) diet for 4 weeks. Cannabinoid CB1 (CB1R) and 5HT1A (5HT1A R) and 5-HT2A (5HT2A R) receptor binding densities are examined. In the hippocampus and hypothalamus, a HF diet significantly increases CB1R binding, while HF+GOS and HF+RS diets prevented this increase. HF diet also increases hippocampal and hypothalamic 5-HT1A R binding, while HF+GOS and HF+RS prevented the alterations. Increased 5-HT2A binding is prevented by HF+GOS and HF+RS in the medial mammillary nucleus. These results demonstrate that increased CB1R, 5-HT1A R and 5-HT2A R induced by a HF diet can be prevented by GOS and RS supplementation in brain regions involved in cognition and appetite. Therefore, increased fiber intake may have beneficial effects on improving learning and memory, as well as reducing excessive appetite, during the chronic consumption of a HF (standard Western) diet.

Seasonal and individual variation in singing behavior correlates with alpha 2-noradrenergic receptor density in brain regions implicated in song, sexual, and social behavior

In seasonally breeding male songbirds, both the function of song and the stimuli that elicit singing behavior change seasonally. The catecholamine norepinephrine (NE) modulates attention and arousal across behavioral states, yet the role of NE in seasonally-appropriate vocal communication has not been well-studied. The present study explored the possibility that seasonal changes in alpha 2-noradrenergic receptors (α 2-R) within song control regions and brain regions implicated in sexual arousal and social behavior contribute to seasonal changes in song behavior in male European starlings ( Sturnus vulgaris). We quantified singing behavior in aviary housed males under spring breeding season conditions and fall conditions. α 2-R were identified with the selective ligand [ 3H]RX821002 using autoradiographic methods. The densities of α 2-R in song control regions (HVC and the robust nucleus of the arcopallium [RA]) and the lateral septum (LS) were lower in Spring Condition males. α 2-R densities in the caudal portion of the medial preoptic nucleus (POM) related negatively to singing behavior. Testosterone concentrations were highest in Spring Condition males and correlated with α 2-R in LS and POM. Results link persistent seasonal alterations in the structure or function of male song to seasonal changes in NE α 2-Rs in HVC, RA, and LS. Individual differences in α 2-R in the POM may in part explain individual differences in song production irrespective of the context in which a male is singing, perhaps through NE modification of male sexual arousal.

Risperidone Treatment Increases CB1 Receptor Binding in Rat Brain

Background/Aims: Body weight gain is a common side effect of treatment with antipsychotics, but the mechanisms underlying this weight gain are unknown. Several factors may be involved in antipsychotic-induced body weight gain including the cannabinoid receptor 1 (CB₁), the serotonin receptor 2C, the ghrelin receptor, neuropeptide Y, adiponectin and proopiomelanocortin. We investigated whether the expression of these factors was affected in rats chronically treated with the antipsychotic risperidone. Methods: Male Sprague-Dawley rats were treated with risperidone (1.0 mg/kg/day) or vehicle (20% hydroxypropyl β-cyclodextrin) for 28 days. Expression of the aforementioned factors were examined together with plasma prolactin and ghrelin levels. Results: No difference in body weight gained during treatment was observed between risperidone and vehicle treated rats, but plasma risperidone levels positively correlated with visceral fat mass. Risperidone treatment increased CB₁ receptor binding in the arcuate nucleus (40%), hippocampus (25–30%) and amygdala (35%) without concurrent alterations in the CB₁ receptor mRNA. Risperidone treatment increased adiponectin mRNA. Conclusion: The present study showed that risperidone treatment altered CB₁ receptor binding in the rat brain. Risperidone-induced adiposity and metabolic dysfunction in the clinic may be explained by increased CB₁ receptor density in brain regions involved in appetite and regulation of metabolic function.

Pentylenetetrazole-induced seizures affect binding site densities for GABA, glutamate and adenosine receptors in the rat brain

Pentylenetetrazole (PTZ) is a convulsant used to model epileptic seizures in rats. In the PTZ-model, altered heat shock protein 27 (HSP-27) expression highlights seizure-affected astrocytes, which play an important role in glutamate and GABA metabolism. This raises the question whether impaired neurotransmitter metabolism leads to an imbalance in neurotransmitter receptor expression. Consequently, we investigated the effects of seizures on the densities of seven different neurotransmitter receptors in rats which were repeatedly treated with PTZ (40 mg/kg) over a period of 14 days. Quantitative in vitro receptor autoradiography was used to measure the regional binding site densities of the glutamate α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA), kainate and N-methyl-d-aspartate (NMDA) receptors, the adenosine receptor type 1 (A1), which is part of the system controlling glutamate release, and the γ-aminobutyric acid (GABA) receptors GABAA and GABAB as well as the GABAA-associated benzodiazepine (BZ) binding sites in each rat. Our results demonstrate altered receptor densities in brain regions of PTZ-treated animals, including the HSP-27 expressing foci (i.e. amygdala, piriform and entorhinal cortex, dentate gyrus). A general decrease of kainate receptor densities was observed together with an increase of NMDA binding sites in the hippocampus, the somatosensory, piriform and the entorhinal cortices. Furthermore, A1 binding sites were decreased in the amygdala and hippocampal CA1 region (CA1), while BZ binding sites were increased in the dentate gyrus and CA1. Our data demonstrate the impact of PTZ induced seizures on the densities of kainate, NMDA, A1 and BZ binding sites in epileptic brain. These changes are not restricted to regions showing glial impairment. Thus, an altered balance between different excitatory (NMDA) and modulatory receptors (A1, BZ binding sites, kainate) shows a much wider regional distribution than that of glial HSP-27 expression, indicating that receptor changes are not following the glial stress responses, but may precede the HSP-27 expression.

D1-like dopamine receptor density in nuclei involved in social behavior correlates with song in a context-dependent fashion in male European starlings

Research in songbirds shows that singing behavior is regulated by both brain areas involved in vocal behavior as well as those involved in social behavior. Interestingly, the precise role of these regions in song can vary as a function of the social, environmental and breeding context. To date, little is known about the neurotransmitters underlying such context-dependent regulation of song. Dopamine (DA) modulates highly motivated, goal-directed behaviors (including sexually motivated song) and emerging data implicate DA in the context-dependent regulation of singing behavior. This study was performed to begin to examine whether differences in DA receptors may underlie, in part, context-dependent differences in song production. We used autoradiographic procedures to label D1-like and D2-like DA receptors to examine the relationship between DA receptor density and singing behavior in multiple contexts in male European starlings ( Sturnus vulgaris). Within a breeding context (when testosterone (T) was high), D1-like receptor density in the medial preoptic nucleus (POM) and midbrain central gray (GCt) negatively correlated with song used to attract a female. Additionally in this context, D1-like receptor density in POM, GCt, medial bed nucleus of the stria terminalis (BSTm), and lateral septum (LS) negatively correlated with song likely used to defend a nest box. In contrast, in a non-breeding context (when T was low), D1-like receptor density in POM and LS positively correlated with song used to maintain social flocks. No relationships were identified between song in any context and D2-like receptor densities. Differences in the brain regions and directional relationships between D1-like receptor binding and song suggest that dopaminergic systems play a region and context-specific role in song. These data also suggest that individual variation in singing behavior may, in part, be explained by individual differences in D1-like receptor density in brain regions implicated in social behavior.

Autoradiographic evidence that prenatal morphine exposure sex-dependently alters μ-opioid receptor densities in brain regions that are involved in the control of drug abuse and other motivated behaviors

The present study examined the effects of prenatal morphine exposure on μ-opioid receptor density in young adult male and female rats to assess the long-term alterations in several brain areas including the nucleus accumbens (NAc), bed nucleus of stria terminalis (BNST), and the basolateral (BLA), lateral (LA), central (CeA), and posteromedial cortical (PMCoA) amygdaloid nuclei. These brain areas are involved in motivating and rewarding behaviors of opiates and other drugs of abuse. The reinforcing actions of opiates appear to be μ-opioid receptor dependent. The results demonstrate that in male rats, prenatal morphine exposure significantly increases the density of μ-opioid receptors in the NAc and PMCoA. In contrast, the same prenatal morphine exposure reduces the density of μ-opioid receptors in the BLA, while increasing it in the CeA and without effects in the LA or BNST. In female rats, prenatal morphine exposure has no effects on the density of μ-opioid receptors in the above six brain areas, but the density of these receptors is dependent on the presence or absence of ovarian hormones. Thus, the present study demonstrates that mid- to late gestational morphine exposure induces long-term, sex-specific alterations in the density of μ-opioid receptors in the NAc and amygdala. Moreover, this prenatal morphine exposure also eliminates sex differences in the density of μ-opioid receptors in the NAc, CeA, and PMCoA but not in the BLA, LA, and BNST.

Behavioral contingencies determine changes in drug‐induced neurotransmitter turnover

AbstractEvidence from several research areas suggests that response‐dependent and independent presentation of environmental events have different neurobiological consequences. Investigations of neurotransmitter turnover rates and cholinergic muscarinic receptor densities in brain regions of rats receiving contingent and noncontingent intravenous morphineresulted in the identification of two neuronal networks that are involved in response dependent morphine presentation. These circuits are concordant with brain regions showing increased glucose utilization in animals receiving response‐dependent electrical stimulation of either the substantia nigra or ventral tegmental area. These data indicate substantial differences between contingent and noncontingent presentation of environmental events and suggest that neurobiological investigations of reinforcement that use response independent delivery of a putative reinforcer must be interpreted with some caution.