The TRPM8 channel forms a complex with the 5-HT(1B) receptor and phospholipase D that amplifies its reversal of pain hypersensitivity.

Effective relief from chronic hypersensitive pain states remains an unmet need. Here we report the discovery that the TRPM8 ion channel, co-operating with the 5-HT(1B) receptor (5-HT(1B)R) in a subset of sensory afferents, exerts an influence at the spinal cord level to suppress central hypersensitivity in pain processing throughout the central nervous system. Using cell line models, ex vivo rat neural tissue and in vivo pain models, we assessed functional Ca(2+) fluorometric responses, protein:protein interactions, immuno-localisation and reflex pain behaviours, with pharmacological and molecular interventions.

Attenuated PLD1 association and signalling at the H452Y polymorphic form of the 5-HT(2A) receptor.

The 5-HT2A receptor (5-HT2AR) is implicated in psychotropic changes within the central nervous system (CNS). A number of polymorphisms have been reported in the 5-HT2AR gene; one of these results in a non-synonymous change, H452Y, in the carboxy-terminal tail of the receptor protein. The minor allele (9% occurrence) has been statistically associated with CNS dysfunction such as impaired memory processing and resistance to neuroleptic treatment in schizophrenic patients.

5-HT2A receptor signalling through phospholipase D1 associated with its C-terminal tail.

The 5-HT2AR (5-hydroxytryptamine-2A receptor) is a GPCR (G-protein-coupled receptor) that is implicated in the actions of hallucinogens and represents a major target of atypical antipsychotic agents. In addition to its classical signalling though PLC (phospholipase C), the receptor can activate several other pathways, including ARF (ADP-ribosylation factor)-dependent activation of PLD (phospholipase D), which appears to be achieved through a mechanism independent of heterotrimeric G-proteins. In the present study we show that wild-type and inactive constructs of PLD1 (but not PLD2) respectively facilitate and inhibit ARF-dependent PLD signalling by the 5-HT2AR.

The SH3 domain of postsynaptic density 95 mediates inflammatory pain through phosphatidylinositol-3-kinase recruitment.

Sensitization to inflammatory pain is a pathological form of neuronal plasticity that is poorly understood and treated. Here we examine the role of the SH3 domain of postsynaptic density 95 (PSD95) by using mice that carry a single amino-acid substitution in the polyproline-binding site. Testing multiple forms of plasticity we found sensitization to inflammation was specifically attenuated.

Raloxifene blocks estradiol induction of the serotonin transporter and 5-hydroxytryptamine2A receptor in female rat brain.

Sex steroids have potent effects on mood, mental state and cognition. Our previous findings and those of others suggest that these effects may be due at least in part to estradiol actions on central serotonergic mechanisms. Specifically, estradiol-17beta in its acute positive feedback mode for gonadotropin release in the female rat induces expression of the genes for the 5-hydroxytryptamine(2A) receptor (5-HT(2A)R) and the serotonin transporter (SERT) in the dorsal raphe nucleus (DRN).

Analgesia mediated by the TRPM8 cold receptor in chronic neuropathic pain.

Background: Chronic established pain, especially that following nerve injury, is difficult to treat and represents a largely unmet therapeutic need. New insights are urgently required, and we reasoned that endogenous processes such as cooling-induced analgesia may point the way to novel strategies for intervention. Molecular receptors for cooling have been identified in sensory nerves, and we demonstrate here how activation of one of these, TRPM8, produces profound, mechanistically novel analgesia in chronic pain states.

Activation of p38 and p42/44 MAP kinase in neuropathic pain: involvement of VPAC2 and NK2 receptors and mediation by spinal glia.

Activation of intracellular signaling pathways involving p38 and p42/44 MAP kinases may contribute importantly to synaptic plasticity underlying spinal neuronal sensitization. Inhibitors of p38 or p42/44 pathways moderately attenuated responses of dorsal horn neurons evoked by mustard oil but not brush and alleviated the behavioral reflex sensitization seen following nerve injury. Activation of p38 and p42/44 MAP kinases in spinal cord ipsilateral to constriction injury was reduced by antagonists of NMDA, VPAC2 and NK2 (but not related) receptors, the glial inhibitor propentofylline and inhibitors of TNF-alpha.

NMDA receptor antagonist treatment at the time of nerve injury prevents injury-induced changes in spinal NR1 and NR2B subunit expression and increases the sensitivity of residual pain behaviours to subsequently administered NMDA receptor antagonists.

Spinal NMDA receptors (NMDA R) are important in neuropathic sensitisation and acute administration of antagonists can provide temporary attenuation of sensitisation. If establishment of the chronic pain state could be prevented by brief administration of such agents at or around the time of nerve injury (pre-emptive analgesia) it might be possible to avoid many of the unacceptable side effects associated with repeated administration of these or other antagonists. Several reports describe aspects of effective pre-emptive analgesia from NMDA R antagonists in animal models of neuropathic pain.

A role of the ubiquitin-proteasome system in neuropathic pain.

Neuropathic pain (characterized by hyperalgesia and allodynia to mechanical and thermal stimuli) causes cellular changes in spinal dorsal horn neurons, some of which parallel those in synaptic plasticity associated with learning. Ubiquitin C-terminal hydrolase (UCH) appears to play a key role in long-term facilitation in Aplysia. The cooperation of UCH with the proteolytic enzyme complex known as the proteasome is required for the degradation of a number of signaling molecules within the cell that may remove normal restraints on synaptic plasticity.

Androgen actions on central serotonin neurotransmission: relevance for mood, mental state and memory.

Sex steroids exert potent effects on mood and mental state in the human. Our previous experimental findings in female rats suggest that these effects may be mediated, in part, by the action of estrogen on the 5-hydroxytryptamine2A receptor (5-HT(2A)R) and serotonin transporter (SERT) in brain. Here we review our recent findings on the effect of acute (approximately 32 h) testosterone manipulation on central 5-HT(2A)R and SERT in male rats.

Effects of tamoxifen on serotonin transporter and 5-hydroxytryptamine(2A) receptor binding sites and mRNA levels in the brain of ovariectomized rats with or without acute estradiol replacement.

Estradiol-17beta (E(2)), in its positive feedback mode for gonadotropin release in the female rat, induces expression of the genes for the 5-hydroxytryptamine(2A) receptor (5-HT(2A)R) and the serotonin transporter (SERT) in the dorsal raphe nucleus (DRN) with a concomitant increase in the densities of 5-HT(2A)R and the SERT in rat forebrain. The forebrain regions affected are those which, in humans, are concerned with the control of mood, mental state, cognition and emotion. Here we have used the mixed estradiol agonist/antagonist, tamoxifen, to determine whether this action of estradiol is mediated by cytoplasmic estradiol receptors.

Ca2+/calcineurin-inhibited adenylyl cyclase, highly abundant in forebrain regions, is important for learning and memory.

Activation of cAMP synthesis by intracellular Ca2+ is thought to be the main mode of cAMP generation in the brain. Accordingly, the Ca2+-activated adenylyl cyclases I and VIII are expressed prominently in forebrain neurons. The present study shows that the novel adenylyl cyclase type IX is inhibited by Ca2+ and that this effect is blocked selectively by inhibitors of calcineurin such as FK506 and cyclosporin A.

Sex steroid control of mood, mental state and memory.

1. Sex steroid hormones exert profound effects on mood and mental state. Thus, in women, oestrogen is thought to protect against depression and delay the onset of schizophrenia and Alzheimer's disease.

Estrogen control of central neurotransmission: effect on mood, mental state, and memory.

1. Estrogen exerts profound effects on mood, mental state and memory by acting on both "classical" monoamine and neuropeptide transmitter mechanisms in brain. Here we review an example of each type of action.

An alpha 1 adrenergic mechanism mediates estradiol stimulation of LHRH mRNA synthesis and estradiol inhibition of POMC mRNA synthesis in the hypothalamus of the prepubertal female rat.

We showed previously that the surge of luteinizing hormone-releasing hormone (LHRH) induced by estradiol-17 beta (E2) in the female rat can be blocked by an alpha 1 adrenergic antagonist. The aim of the present study was to determine whether this was due to a direct action of E2 on noradrenergic projections to LHRH neurons or whether it also involved other systems such as the arcuate pro-opiomelanocortin (POMC) neurons which are thought to inhibit LHRH biosynthesis and release. The experimental preparation was the prepubertal female rat in which an LHRH surge is induced by pregnant mare serum gonadotropin.

Inhibition by NK2 but not NK1 antagonists of carrageenan-induced preprodynorphin mRNA expression in rat dorsal horn lamina I neurons.

Previous evidence indicated that NK2 rather than NK1 receptors play a central role in mediating the electrophysiological responses of dorsal horn neurons to brief cutaneous stimuli such as noxious heat (but not noxious pinch) and moderately sustained stimuli such as mustard oil, topically applied over 10-20 min. The present experiments were designed to investigate, by in situ hybridisation histochemistry, a delayed genomic response in dorsal horn neurons (the expression of preprodynorphin mRNA induced by intraplantar carrageenan injection) and explore the role of NK1 and NK2 receptors in mediating this response. In anaesthetised rats with bilateral intraplantar injections of carrageenan, neurokinin receptor antagonists were administered unilaterally by prolonged ionophoresis into the superficial dorsal horn.

Testosterone Induces an All-or-None, Exponential Increase in Arginine Vasopressin mRNA in the Bed Nucleus of Stria Terminalis of the Hypogonadal Mouse.

The bed nucleus of the stria terminalis (BNST) in rodents contains arginine vasopressin (AVP) neurons which project to the lateral septum (LS) and habenula (LH) and are thought to be important for social recognition or memory. In previous studies we demonstrated that AVP immunoreactivity in the LS and LH is absent in the hypogonadal (hpg) mouse and that AVP immunoreactivity in the LH and LS of this mutant can be induced by testosterone. The aim of the present study was to determine whether this action of testosterone was due to the induction of AVP gene expression in BNST neurons and if so the time taken for testosterone to exert its effect.

Oestrogen positive feedback reduces arcuate proopiomelanocortin messenger ribonucleic Acid.

Oestradiol-17ß, in its positive feedback mode, as well as stimulating the release of luteinizing hormone-releasing hormone. (LHRH), also stimulates LHRH mRNA synthesis in medial preoptic neurons. Our aim was to determine whether the action of oestradiol might be mediated in part by inhibiting arcuate proopiomelanocortin (POMC) neurons which terminate on LHRH neurons.

Relative density of 5-hydroxytryptamine receptor subtype mRNAs in female rat neuroendocrine brain determined by in situ hybridization histochemistry.

The relative distribution and density of three 5-hydroxytryptamine (5-HT) receptor subtype mRNAs in female rat brain were investigated by in situ hybridization histochemistry using (36)S-labeled riboprobes. Special attention was focused on the hypothalamus and other parts of the brain involved in neuroendocrine control. Perikarya of the diagonal band of Broca (DBB), medial septum (MS), medial preoptic area (MPOA), and ventromedial hypothalamic nucleus (VMH) contained high concentrations of 5-HT(2) receptor mRNA, only moderate amounts of 5-HT(1A) receptor mRNA, and variable amounts of 5-HTP(1c) receptor mRNA.

Steroid control of central neuronal interactions and function.

Steroids have potent actions on the brain which can be categorized as; (i) fast (approximately ms-s), (ii) intermediate (h-days), (iii) long-term reversible (days-weeks) and (iv) long-term irreversible. Here attention is focussed on the intermediate and long-term reversible effects of steroids with emphasis on glucocorticoids and oestrogen. Glucocorticoid negative feedback is generally classified as fast, delayed and long-term.

Oestrogen positive feedback stimulates the synthesis of LHRH mRNA in neurones of the rostral diencephalon of the rat.

Our aim was to determine whether oestrogen administered to ovariectomized rats in a manner which stimulates the release of LHRH also stimulates the synthesis of LHRH mRNA. Adult female Wistar rats were ovariectomized under halothane anaesthesia between 09.00 and 11.

cDNA sequence of human beta-preprotachykinin, the common precursor to substance P and neurokinin A.

The nucleotide sequence of cDNA encoding the human substance P precursor, beta-preprotachykinin (beta-PPT), has been determined. The source of mRNA was a human laryngeal carcinoid tumour that contained a high concentration of immunoreactive substance P. The human beta-PPT polypeptide is 129 amino acids long and contains regions encoding substance P and neurokinin A, each flanked by basic amino acid residues.

ADP and arachidonic acid induced platelet aggregation in schizophrenia and atypical psychoses.

Platelet aggregatory responses to adenosine diphosphate (ADP) and arachidonic acid were examined in 6 drug-free schizophrenics, 5 other drug-free psychotics, 8 'acute-on-chronic' schizophrenics (on long-term neuroleptic therapy) and 38 healthy controls. Platelet aggregation and disaggregation following ADP was significantly lower in 'acute-on-chronic' schizophrenics (on drugs) compared with healthy controls, and disaggregation following 1 microM ADP was significantly less in drug-free schizophrenics. The difference between maximum aggregation induced by ADP and that induced by arachidonic acid was significantly greater in schizophrenics (both on drugs and drug-free) than in controls.