Role of adrenal medulla in development of sexual dimorphism in inflammation

Topical coapplication of hyaluronan with transdermal drug delivery enhancers attenuates inflammatory and neuropathic pain

ABSTRACT

We have previously shown that intradermal injection of high-molecular-weight hyaluronan (500-1200 kDa) produces localized antihyperalgesia in preclinical models of inflammatory and neuropathic pain. In the present experiments, we studied the therapeutic effect of topical hyaluronan, when combined with each of 3 transdermal drug delivery enhancers (dimethyl sulfoxide [DMSO], protamine or terpene), in preclinical models of inflammatory and neuropathic pain. Topical application of 500 to 1200 kDa hyaluronan (the molecular weight range used in our previous studies employing intradermal administration), dissolved in 75% DMSO in saline, markedly reduced prostaglandin E 2 (PGE 2 ) hyperalgesia, in male and female rats. Although topical 500- to 1200-kDa hyaluronan in DMSO vehicle dose dependently, also markedly, attenuated oxaliplatin chemotherapy-and paclitaxel chemotherapy-induced painful peripheral neuropathy (CIPN) in male rats, it lacked efficacy in female rats. However, following ovariectomy or intrathecal administration of an oligodeoxynucleotide antisense to G-protein-coupled estrogen receptor (GPR30) mRNA, CIPN in female rats was now attenuated by topical hyaluronan. Although topical coadministration of 150 to 300, 300 to 500, or 1500 to 1750 kDa hyaluronan with DMSO also attenuated CIPN, a slightly lower-molecular-weight hyaluronan (70-120 kDa) did not. The topical administration of a combination of hyaluronan with 2 other transdermal drug delivery enhancers, protamine and terpene, also attenuated CIPN hyperalgesia, an effect that was more prolonged than with DMSO vehicle. Repeated administration of topical hyaluronan prolonged the duration of antihyperalgesia. Our results support the use of topical hyaluronan, combined with chemically diverse nontoxic skin penetration enhancers, to induce marked antihyperalgesia in preclinical models of inflammatory and neuropathic pain.

Second messengers mediating high-molecular-weight hyaluronan-induced antihyperalgesia in rats with chemotherapy-induced peripheral neuropathy

ABSTRACT

High-molecular-weight hyaluronan (HMWH) is an agonist at cluster of differentiation (CD)44, the cognate hyaluronan receptor, on nociceptors, where it acts to induce antihyperalgesia in preclinical models of inflammatory and neuropathic pain. In the present experiments, we studied the CD44 second messengers that mediate HMWH-induced attenuation of pain associated with oxaliplatin and paclitaxel chemotherapy-induced peripheral neuropathy (CIPN). While HMWH attenuated CIPN only in male rats, after ovariectomy or intrathecal administration of an oligodeoxynucleotide (ODN) antisense to G protein-coupled estrogen receptor (GPR30) mRNA, female rats were also sensitive to HMWH. Intrathecal administration of an ODN antisense to CD44 mRNA markedly attenuated HMWH-induced antihyperalgesia in male rats with CIPN induced by oxaliplatin or paclitaxel. Intradermal administration of inhibitors of CD44 second messengers, RhoA (member of the Rho family of GTPases), phospholipase C, and phosphatidylinositol (PI) 3-kinase gamma (PI3Kγ), attenuated HMWH-induced antihyperalgesia as does intrathecal administration of an ODN antisense to PI3Kγ. Our results demonstrated that HMWH induced antihyperalgesia in CIPN, mediated by its action at CD44 and downstream signaling by RhoA, phospholipase C, and PI3Kγ.

Sexually Dimorphic Role of Toll-like Receptor 4 (TLR4) in High Molecular Weight Hyaluronan (HMWH)-induced Anti-hyperalgesia

High molecular weight hyaluronan (HMWH), a prominent component of the extracellular matrix binds to and signals via multiple receptors, including cluster of differentiation 44 (CD44) and toll-like receptor 4 (TLR4). We tested the hypothesis that, in the setting of inflammation, HMWH acts at TLR4 to attenuate hyperalgesia. We found that the attenuation of prostaglandin E2 (PGE2)-induced hyperalgesia by HMWH was attenuated by a TLR4 antagonist (NBP2-26245), but only in male and ovariectomized female rats. In this study we sought to evaluated the role of the TLR4 signaling pathway in anti-hyperalgesia induced by HMWH in male rats. Decreasing expression of TLR4 in nociceptors, by intrathecal administration of an oligodeoxynucleotide (ODN) antisense to TLR4 mRNA, also attenuated HMWH-induced anti-hyperalgesia, in male and ovariectomized female rats. Estrogen replacement in ovariectomized females reconstituted the gonad-intact phenotype. The administration of an inhibitor of myeloid differentiation factor 88 (MyD88), a TLR4 second messenger, attenuated HMWH-induced anti-hyperalgesia, while an inhibitor of the MyD88-independent TLR4 signaling pathway did not. Since it has previously been shown that HMWH-induced anti-hyperalgesia is also mediated, in part by CD44 we evaluated the effect of the combination of ODN antisense to TLR4 and CD44 mRNA. This treatment completely reversed HMWH-induced anti-hyperalgesia in male rats. Our results demonstrate a sex hormone-dependent, sexually dimorphic involvement of TLR4 in HMWH-induced anti-hyperalgesia, that is MyD88 dependent. PERSPECTIVE: The role of TLR4 in anti-hyperalgesia induced by HMWH is a sexually dimorphic, TLR4 dependent inhibition of inflammatory hyperalgesia that provides a novel molecular target for the treatment of inflammatory pain.

Sexual dimorphism in the nociceptive effects of hyaluronan

ABSTRACT

Intradermal administration of low-molecular-weight hyaluronan (LMWH) in the hind paw induced dose-dependent (0.1, 1, or 10 µg) mechanical hyperalgesia of similar magnitude in male and female rats. However, the duration of LMWH hyperalgesia was greater in females. This sexual dimorphism was eliminated by bilateral ovariectomy and by intrathecal administration of an oligodeoxynucleotide (ODN) antisense to the G-protein-coupled estrogen receptor (GPR30) mRNA in females, indicating estrogen dependence. To assess the receptors at which LMWH acts to induce hyperalgesia, LMWH was administered to groups of male and female rats that had been pretreated with ODN antisense (or mismatch) to the mRNA for 1 of 3 hyaluronan receptors, cluster of differentiation 44 (CD44), toll-like receptor 4, or receptor for hyaluronan-mediated motility (RHAMM). Although LMWH-induced hyperalgesia was attenuated in both male and female rats pretreated with ODN antisense for CD44 and toll-like receptor 4 mRNA, RHAMM antisense pretreatment only attenuated LMWH-induced hyperalgesia in males. Oligodeoxynucleotide antisense for RHAMM, however, attenuated LMWH-induced hyperalgesia in female rats treated with ODN antisense to GPR30, as well as in ovariectomized females. Low-molecular-weight hyaluronan-induced hyperalgesia was significantly attenuated by pretreatment with high-molecular-weight hyaluronan (HMWH) in male, but not in female rats. After gonadectomy or treatment with ODN antisense to GPR30 expression in females, HMWH produced similar attenuation of LMWH-induced hyperalgesia to that seen in males. These experiments identify nociceptors at which LMWH acts to produce mechanical hyperalgesia, establishes estrogen dependence in the role of RHAMM in female rats, and establishes estrogen dependence in the inhibition of LMWH-induced hyperalgesia by HMWH.

Inhibitory effects of progesterone differ in dendritic cells from female and male rodents

BACKGROUND

Steroid hormones, such as progesterone, are known to have immunomodulatory effects. Our research group previously reported direct effects of progesterone on dendritic cells (DCs) from female rodents. Primarily affecting mature DC function, progesterone effects included inhibition of proinflammatory cytokine secretion, downregulation of cell surface marker (major histocompatibility complex class II, CD80) expression, and decreased T-cell proliferative capacity, and were likely mediated through progesterone receptor (PR) because the PR antagonist RU486 reversed these effects.

OBJECTIVE

The goal of this study was to assess differences in response to progesterone by DCs from female and male rodents.

METHODS

Using real-time reverse-transcriptase polymerase chain reaction, transcriptional expression of steroid hormone receptors was measured in immature bone marrow-derived DCs (BMDCs) from male and female rats. Expression of steroid hormone receptor protein was also assessed in these cells using flow cytometry and fluorescence microscopy. To evaluate functional differences between BMDCs from female and male rats in response to the steroid hormone progesterone, levels of secreted cytokines were measured using enzyme-linked immunosorbent assay.

RESULTS

Higher numbers of immature BMDCs from males expressed glucocorticoid receptor (GR) and androgen receptor (AR) proteins compared with females (males vs females, mean [SD]: GR = 68.75 [7.27] vs 43.61 [13.97], P = NS; AR = 75.99 [15.38] vs 8.25 [1.88], P = 0.002), whereas higher numbers of immature BMDCs from females expressed PR protein compared with males (females vs males: PR = 74.19 [12.11] vs 14.14 [4.55], P = 0.043). These differences were not found at the level of transcription (females vs males: GR = 0.088 vs 0.073, P = NS; AR = 0.076 vs 0.069, P = NS; PR = 0.075 vs 0.065, P = NS). Compared with those from females, mature BMDCs from males produced higher quantities of cytokines (tumor necrosis factor-alpha [TNF-alpha], interleukin [IL]-1beta, IL-10) (females vs males: TNF-alpha = 920.0 [79.25] vs 1100.61 [107.97], P = NS; IL-1beta = 146.60 [38.04] vs 191.10 [10.47], P = NS; IL-10 = 167.25 [4.50] vs 206.15 [23.48], P = NS). Conversely, BMDCs from females were more sensitive to progesterone, as indicated by a more dramatic reduction in proinflammatory cytokine secretion (females vs males, highest concentration of progesterone: TNF-alpha = 268.94 [28.59] vs 589.91 [100.98], P = 0.04; IL-1beta = 119.50 [10.32] vs 154.35 [6.22], P = NS).

CONCLUSIONS

These findings suggest that progesterone effects on DCs in rodents may be more pronounced in females than in males, and this is likely due to differences in PR protein expression. Our observations may help elucidate disparities in the incidence and severity of autoimmune disorders between females and males, and the role specific steroid hormones play in regulating immune responses.

beta(2)-Adrenergic receptor-dependent sexual dimorphism for murine leukocyte migration

In wild-type FVB mice, leukocyte recruitment to lipopolysaccharide was sexually dimorphic, with a greater number of leukocytes recruited in females. In male beta(2)-adrenergic receptor knock out mice (bred on a congenic FVB background) the number of leukocytes recruited was increased approximately 4-fold, while in females there was no change, eliminating sexual dimorphism in leukocyte migration. While there were significantly fewer recruited CD62L(+) and CD11a(+) leukocytes in wild-type males, only in male beta-adrenergic receptor knock out mice was there an increase in the number of recruited CD11a(+) leukocytes, again eliminating sexual dimorphism. Thus, leukocyte migration and CD11a(+) adhesion molecule expression in male, but not in female, leukocytes is beta-adrenergic receptor-dependent. Our findings provide support for a role of beta(2)-adrenergic receptor mechanisms in the inflammatory response, and suggest that beta(2)-adrenergic receptor on male leukocytes contributes to sexual dimorphism in the effect of stress on inflammatory diseases.

Sexual dimorphism of ornithine decarboxylase in the mouse adrenal: influence of polyamine deprivation on catecholamine and corticoid levels

Adrenal sexual dimorphism is thought to be important in explaining sex-related differences regarding prevalent diseases and the responses to stress and drugs. We report here that in CD1 mice there is marked sexual dimorphism affecting not only gland size and corticoid hormone secretion but also adrenal ornithine decarboxylase (ODC), polyamine, and catecholamine levels in which testosterone appears to be a major determinant. Our results show that adrenal weight, ODC activity, and corticosterone and aldosterone secretion were higher in female than in male mice and that orchidectomy brought these male parameters closer to the values found in females. mRNA levels of steroidogenic proteins SF-1, Dax-1, steroid 21-hydroxylase, and aldosterone synthase appeared to be slightly higher in female than in male adrenals. Immunocytochemical analysis of adrenal ODC revealed that immunoreactivity was higher in females than in males and was located mainly in the cortical cells, and especially in zona glomerulosa, whereas no sex differences in ODC mRNA levels were observed. These results suggest that sex-associated differences in the expression of ODC in the mouse adrenal gland appear to be related mainly to posttranscriptional mechanisms. Combination treatment of mice with alpha-difluoromethylornithine (a suicide inhibitor of ODC) and a polyamine-deficient diet produced a marked decrease in adrenal polyamine and catecholamine levels and a significant reduction in plasma corticosterone and aldosterone concentrations that were not associated with a decrease in the mRNA levels of steroidogenic proteins. All of these data suggest a relevant role for testosterone, ODC, and polyamines in the mouse adrenal function.

Sexual dimorphism in innate immune responses to infectious organisms

Gender has long been known to be a contributory factor in the incidence and progression of disorders associated with immune system dysregulation. More recently, evidence has accumulated that gender may also play an important role in infectious disease susceptibility. In general, females generate more robust and potentially protective humoral and cell-mediated immune responses following antigenic challenge than their male counterparts. In contrast, males have frequently been observed to mount more aggressive and damaging inflammatory immune responses to microbial stimuli. In this article we review the evidence for sexual dimorphism in innate immune responses to infectious organisms and describe our recent studies that may provide a mechanism underlying gender-based differences in conditions such as bacterial sepsis.

Neurogenic inflammation and arthritis

Inflammation and inflammatory diseases are sexually dimorphic, but the underlying causes for this observed sexual dimorphism are poorly understood. We discuss neural-immune mechanisms that underlie sexual dimorphism in three critical aspects of the inflammatory process-plasma extravasation, neutrophil function, and inflammatory hyperalgesia. Plasma extravasation and accumulation/activation of leukocytes into tissues are critical components in inflammation and are required for several other aspects of the inflammatory response. Pain (hyperalgesia) also markedly influences the magnitude of other components of the inflammatory response and induces a feedback control of plasma extravasation and neutrophil function. More important, this feedback control itself is powerfully modulated by vagal afferent activity and both the function of the primary afferent nociceptor and the modulation of inflammatory hyperalgesia by vagal afferent activity are highly sexually dimorphic.

Estrogen regulates adrenal medullary function producing sexual dimorphism in nociceptive threshold and beta-adrenergic receptor-mediated hyperalgesia in the rat

Epinephrine produces sexually dimorphic beta(2)-adrenergic receptor-mediated mechanical hyperalgesia, with male rats exhibiting greater hyperalgesia. Because female rats have higher plasma epinephrine levels, and beta-adrenergic receptor sensitivity is affected by chronic exposure to agonists, we tested the hypothesis that this sexual dimorphism is due to epinephrine-induced desensitization of beta(2)-adrenergic receptors. Following gonadectomy, epinephrine hyperalgesia, as measured by the Randall-Selitto paw-withdrawal test, was unchanged in male rats while in females it was increased. Prepubertal male and female rats do not demonstrate sexual dimorphism in either plasma epinephrine level or epinephrine-induced hyperalgesia. Adrenal medullectomy and adrenal denervation both significantly enhanced epinephrine hyperalgesia, but only in females. In contrast, the sexually dimorphic hyperalgesia induced by prostaglandin E(2), another agent that acts directly to sensitize primary afferent nociceptors, was not enhanced by adrenal medullectomy or denervation. Chronic administration of epinephrine in male rats, to produce plasma levels similar to those of gonad-intact females, significantly attenuated epinephrine-induced hyperalgesia, making it similar to that in females. These results strongly support the suggestion that estrogen regulates plasma epinephrine in female rats and differential sensitivity to beta(2)-adrenergic agonists accounts for the sexual dimorphism in epinephrine-induced hyperalgesia. Unexpectedly, regulation of adrenal medullary function by estrogen was also found to modulate baseline nociceptive threshold such that females had a lower nociceptive threshold.

Sympathoadrenal-dependent sexually dimorphic effect of nonhabituating stress on in vivo neutrophil recruitment in the rat

Since stress both activates the sympathoadrenal axis and profoundly affects inflammation and inflammatory diseases, many of which are sexually dimorphic, we tested whether the effect of stress on neutrophil recruitment, a primary component of the acute inflammatory response, is sexually dimorphic. The effect of intermittent sound (over 4 days), a nonhabituating stress, on lipopolysaccharide (LPS)-induced recruitment of neutrophils was evaluated in vivo in the rat air pouch model. At 24 h following the last stress exposure, LPS-induced neutrophil recruitment was enhanced in male rats, but not in females. When gonadectomized prepubertally and tested as adults, stress significantly inhibited the magnitude of LPS-induced neutrophil recruitment in males, while it still had no effect in gonadectomized females. In males, following adrenal denervation, the increase in LPS-induced neutrophil recruitment produced by stress was prevented. Since these data suggest that the effect of stress is dependent on the sympathoadrenal axis, we tested the hypothesis that catecholamines mediate the stress effects. In male rats, the effect of stress on LPS-induced neutrophil recruitment was significantly attenuated by continuous administration of the beta-adrenergic receptor antagonist, propranolol (4 mg kg(-1) day(-1)), during sound stress exposure, and administration of isoproterenol (10 nmoles, i.v.) significantly increased neutrophil recruitment in males, an effect that was qualitatively and quantitatively similar to the effect of stress. Propranolol significantly increased neutrophil recruitment in nonstressed female rats, but did not significantly affect neutrophil recruitment in stressed females. These findings indicate a marked male sex hormone-dependent sexual dimorphism in the sympathoadrenal-dependent effect of stress on neutrophil migration, a primary component of the inflammatory response, and suggest that the sympathoadrenal axis contributes to this effect via release of epinephrine.

The organizational and activational effects of sex hormones on tactile and thermal hypersensitivity following lumbar nerve root injury in male and female rats

Considerable evidence exists for sex differences in human pain sensitivity. Women typically report a higher incidence of various painful conditions and report that the conditions are more painful when compared to men. In the present study, we sought to determine whether sex differences in pain sensitivity are observed using a lumbar radiculopathy model of low back pain in the rat and whether removal or alteration of gonadal hormones at specific timepoints can modulate these sex differences. Pubertal and adult male and female Sprague-Dawley rats were castrated 2 or 6 weeks prior to L5 nerve root injury to determine the activational hormonal effects. In a separate study, neonatal male and female Sprague-Dawley rats were either castrated or injected with testosterone, respectively, on postnatal day one to determine the organizational effects of gonadal hormones on L5 nerve root injury-induced behavioral hypersensitivity. Our results demonstrate that there was a statistically significant sex difference in the magnitude of mechanical allodynia and thermal hyperalgesia following experimentally induced radiculopathy in the rat: females demonstrated decreased thresholds to tactile and thermal stimuli as compared to males. Furthermore, the enhanced female hypersensitivity was reversed in pubertal and adult animals ovariectomized 6 weeks, but not 2 weeks prior to L5 nerve root injury. Our results demonstrate that the activational effects of gonadal hormones mediate the enhanced female tactile and thermal hypersensitivity following L5 nerve root injury. These results suggest that manipulation of gonadal hormones may be a potential source for novel therapies for chronic pain in women.

Sexual dimorphism in the effect of nonhabituating stress on neurogenic plasma extravasation

The sympathoadrenal axis contributes to the sexual dimorphism of the inflammatory response. As stress both activates the sympathoadrenal axis and profoundly affects inflammation and inflammatory disease, we evaluated whether stress exerts a sexually dimorphic effect on a major component of the inflammatory response, plasma extravasation. We evaluated the effect of a nonhabituating stress, repeated intermittent sound (30 min/day for 4 days), on neurogenic synovial plasma extravasation, induced by bradykinin in the rat knee joint. Sound stress profoundly inhibited bradykinin-induced plasma extravasation in male rats, but profoundly enhanced it in female rats. These effects took 24 h to fully develop after the last exposure to stress. In gonadectomized males, bradykinin-induced plasma extravasation was lower than intact males, and sound stress now enhanced it, i.e. gonadectomized males were phenotypically like intact females. In gonadectomized females, bradykinin-induced plasma extravasation was greater than in intact adult females, and sound stress still enhanced it. Adrenal enucleation significantly attenuated the effect of sound stress on bradykinin-induced plasma extravasation in both male and female rats. We tested the hypothesis that these effects of sound stress were due to sustained enhanced plasma levels of stress hormones. Corticosterone and epinephrine, only when administered in combination, over five days, produced a qualitatively similar effect as sound stress, i.e. bradykinin-induced plasma extravasation was significantly decreased in males and increased in females. These findings suggest that a combined effect of the hypothalamic-pituitary adrenal and sympathoadrenal stress axes are responsible for the marked sexual dimorphism in the effect of stress on the inflammatory response.

Fasting is a physiological stimulus of vagus-mediated enhancement of nociception in the female rat

The vagus nerve modulates nociception by a mechanism dependent upon gonadal hormones and the adrenal medulla. In the present study we tested the hypothesis that this modulation is dynamically controlled by physiological stimulation of structures innervated by the subdiaphragmatic vagus. Specifically, food deprivation (fasting) was employed to increase activity in the subdiaphragmatic vagus, and the experiments were performed mainly in female rats because our previous observations suggested that baseline activity in the pathway is lower in females than in males. Consistent with the hypothesis, after a 48-h fast, female rats exhibited increased nociceptive behavior in the formalin test. In contrast, fasting had no effect on formalin-evoked nociceptive behavior in male rats. The fasting-induced effect on nociception appears to be mediated by the vagus nerve since it is prevented by subdiaphragmatic vagotomy. Also similar to the previously characterized vagus-mediated modulation, the effect of fasting in the female is blocked by gonadectomy or adrenal medullectomy, and hormone replacement with 17beta-estradiol in gonadectomized female rats restored the effect of fasting. Decreased glucose metabolism apparently does not play a significant role in the effect of fasting on nociception, since the effect was unchanged when 5% glucose was provided in the drinking water throughout the fasting period. On the other hand, increasing the bulk content of the stomach (without providing nutrients) by infusion of petrolatum significantly attenuated the effect of fasting during the interphase period of the formalin response, suggesting that decreased gut distention, and possibly motility, are important in fasting-induced enhancement of nociception. These results indicate that fasting is a physiological activator of the vagus-mediated pain modulation pathway. This suggests the possibility that, especially in females, natural periodic changes in gut distention and motility may control an ongoing vagus-mediated adjustment in the organism's nociceptive sensitivity.

Vagal modulation of bradykinin-induced mechanical hyperalgesia in the female rat

In male rats, activity in subdiaphragmatic vagal afferents modulates nociception via an adrenal medulla-dependent mechanism. Because both the vagus and adrenal medullae are sexually dimorphic, we evaluated vagotomy-induced changes in mechanical nociceptive threshold and inflammatory hyperalgesia in female rats and compared them to those previously reported in male rats. We have found that (1) mechanical nociceptive threshold is lower in female rats than in male rats, perhaps because of tonic release of adrenal medullary factors in female rats; (2) mechanical nociceptive threshold in female rats is influenced to a lesser degree by activity in the subdiaphragmatic vagus; (3) vagotomy-induced enhancement of bradykinin hyperalgesia is greater in female rats; (4) in female rats, in contrast to male rats, celiac plus celiac accessory branch vagotomy failed to fully account for the enhancement of bradykinin hyperalgesia in complete subdiaphragmatic vagotomy; and (5) in female rats, in contrast to male rats, adrenal medullectomy plus subdiaphragmatic vagotomy only partially (approximately 30%) reversed the effect of vagotomy on bradykinin hyperalgesia. These findings demonstrate sexual dimorphism in the modulation of both mechanical nociceptive threshold and bradykinin-induced hyperalgesia by activity in subdiaphragmatic vagal afferents as well as the adrenal medulla.

Pain in the brain: are hormones to blame?

Pain is a multi-dimensional process involving the physical, emotional and perceptual integration of noxious information. The physical component is relayed via the spinal cord to several brain areas to initiate the detection of pain. The emotional aspect is encoded by the limbic system and encapsulates the relationship between pain and mood. Within the limbic system, the hypothalamus undertakes a diversity of separate and interrelated functions. Dysfunction of the hypothalamo-pituitary-adrenal axis has been implicated in a variety of chronic pain conditions and might also be associated with increased risk of developing mood disorders. Experimental and clinical evidence also exists to implicate the effects of other hormonal modulators in the manifestation of chronic pain. Specific targeting of hormonal cascade and effector mechanisms could provide an alternative strategy for the treatment of various chronic pain conditions.

Endogenous opiates and behavior: 2001

This paper is the twenty-fourth installment of the annual review of research concerning the opiate system. It summarizes papers published during 2001 that studied the behavioral effects of the opiate peptides and antagonists. The particular topics covered this year include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology(Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration and thermoregulation (Section 16); and immunological responses (Section 17).