Activation of mesolimbic dopaminergic neurons following central administration of histamine is mediated by H1 receptors

The effect of intracerebroventricular administration of histamine on the activity of mesolimbic and nigrostriatal dopaminergic (DA) neurons was determined in male rats. The activity of these neurons was estimated by measuring: (1) the accumulation of 3,4-dihydroxyphenylalanine (DOPA) after administration of a decarboxylase inhibitor, and (2) the concentration of 3,4-dihydroxyphenylacetic acid (DOPAC) in the nucleus accumbens and striatum, which contain the terminals of these neurons. Central administration of histamine increased both DOPA accumulation and DOPAC concentrations in the nucleus accumbens, but was without effect in the striatum. The increase in DOPAC concentrations in the nucleus accumbens occurred within 10 min and was sustained for at least 120 min. The H1 antagonist mepyramine blocked whereas the H2 antagonist zolantidine did not affect histamine-induced increases in DOPAC concentrations in the nucleus accumbens. Neither mepyramine nor zolantidine affected basal DOPAC concentrations in the nucleus accumbens. These results indicate that central administration of histamine stimulates mesolimbic DA neurons through an action at the H1 receptor, but has no effect upon the activity of nigrostriatal DA neurons.

Differential effects of the D2 receptor agonist quinelorane on the secretion of prolactin and alpha-melanocyte-stimulating hormone

The purpose of the present study was to determine the effects of quinelorane, a selective D2 receptor agonist, on concentrations of prolactin and alpha-melanocyte-stimulating hormone (alpha-MSH) in plasma of male rats. Quinelorane decreased plasma concentrations of prolactin but not of alpha-MSH, whereas, the D2 receptor antagonist raclopride increased plasma concentrations of both hormones. Quinelorane reversed the effects of raclopride on circulating levels of prolactin, but not alpha-MSH. The results of this study suggest that secretion of hormones from melanotrophs and lactotrophs is regulated by different subtypes of D2 receptors.

Sexual differences in the stimulatory effects of bombesin on tuberoinfundibular dopaminergic neurons

The purpose of this study was to (1) examine the effects of central administration of bombesin on the activity of tuberoinfundibular dopaminergic (DA) neurons in male and female rats, and (2) determine if sexual differences in the responsiveness of these neurons to bombesin were due to the presence of prolactin or gonadal steroids. The activity of tuberoinfundibular DA neurons was estimated by measuring the concentrations of the dopamine metabolite 3,4-dihydroxyphenylacetic acid (DOPAC) in terminals of these neurons in the median eminence. The effects of bombesin on the secretion of prolactin and alpha-melanocyte stimulating hormone (alpha MSH), and the activities of nigrostriatal, mesolimbic, and periventricular-hypophysial DA neurons were also determined in gonadally intact male and female rats. Central administration of bombesin (10 ng/rat; i.c.v.) decreased prolactin secretion in gonadally intact male and female rats, but only in males was this associated with an increase in the activity of tuberoinfundibular DA neurons. In contrast, bombesin increased the activity of periventricular-hypophysial DA neurons terminating in the intermediate lobe of both male and female rats, and this was associated with a decrease in alpha MSH secretion in both sexes. Bombesin had no effect on the activities of nigrostriatal, mesolimbic, or periventricular-hypophysial DA neurons terminating in the neural lobe in either sex. The loss of endogenous gonadal hormones following ovariectomy rendered tuberoinfundibular DA neurons responsive to the stimulatory effects of bombesin, whereas immunoneutralization of endogenous prolactin following administration of prolactin antiserum had no effect on the inability of bombesin to alter the activity of these neurons in female rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Remoxipride and raclopride differentially alter the activity of incertohypothalamic dopaminergic neurons

The effects of two dopaminergic (DA) antagonists, raclopride (S-(-)-3,5-dichloro-N-[(1-ethyl-2-pyrrolidinyl)methyl]-2-hydroxy- 6-methoxybenzamide(+)-tartrate) and remoxipride (S(-)-3-bromo-N-[(1-ethyl-2-pyrrolidinyl)methyl]-2, 6-dimethoxybenzamide hydrochloride monohydrate), were compared on the DA receptor-mediated regulation of incertohypothalamic and nigrostriatal DA neurons. Both drugs produced dose- and time-related increases in concentrations of 3,4-dihydroxyphenylacetic acid (DOPAC) in the striatum, which contains the terminals of the nigrostriatal DA neurons. On the other hand, raclopride but not remoxipride increased concentrations of DOPAC in the medial zona incerta and dorsomedial hypothalamic nucleus, regions that contains cell bodies and terminals, respectively, of incertohypothalamic DA neurons. These results suggest that raclopride blocks a population of DA receptors that regulates the activity of incertohypothalamic DA neurons, whereas remoxipride does not.

Comparison of the effects of remoxipride and raclopride on nigrostriatal and mesolimbic dopaminergic neuronal activity and on the secretion of prolactin and alpha-melanocyte-stimulating hormone

Raclopride and remoxipride, which are reported to be selective dopamine-D2 antagonists, are currently under clinical investigation as antipsychotic drugs. The present study compared the relative abilities of these two drugs to alter the activity of nigrostriatal and mesolimbic dopaminergic neurons, and plasma levels of hormones originating from the anterior and intermediate lobes of the pituitary in male rats. Although raclopride was consistently more potent than remoxipride, both drugs produced dose- and time-related increases in concentrations of 3,4-dihydroxyphenylacetic acid in the striatum and nucleus accumbens, which contain terminals of nigrostriatal and mesolimbic dopaminergic neurons, respectively. Both drugs also caused significant dose- and time-related increases in plasma levels of prolactin, but only raclopride increased plasma levels of alpha-melanocyte-stimulating hormone (alpha-MSH). These results suggest that although raclopride and remoxipride are both classified as D2 receptor antagonists they can be distinguished from one another by their relative ability to block the inhibitory dopaminergic control of alpha-MSH from melanotrophs in the intermediate lobe of the rat pituitary.

Characterization of opioid receptor-mediated regulation of incertohypothalamic dopamine neurons: lack of evidence for a role of 5-hydroxytryptaminergic neurons in mediating the stimulatory effects of morphine

The purpose of the present study was to characterize opioid receptor-mediated regulation of incertohypothalamic dopaminergic (DA) neurons in the rat brain by examining the acute effects of selective mu or kappa opioid receptor agonists and antagonists on concentrations of 3,4-dihydroxyphenylacetic acid (DOPAC) in the medial zona incerta (MZI) and the dorsomedial hypothalamic nucleus (DMN) which contain cell bodies and terminals, respectively, of these neurons. Morphine caused a dose- and time-related increase in concentrations of DOPAC in MZI and DMN; this stimulatory effect was blocked by the mu opioid receptor antagonist naltrexone. In contrast, activation or blockade of kappa opioid receptors following administration of U-50,488 or nor-binaltorphimine, respectively, had no effect on DOPAC concentrations in either the MZI or DMN. The basal activity of incertohypothalamic DA neurons and their response to morphine was similar in male and female rats. Morphine also increased the concentrations of 5-hydroxyindoleacetic acid in MZI and DMN, indicating that morphine increases the activity of 5-hydroxytryptamine (5HT) neurons projecting to these regions. This might suggest that morphine-induced activation of incertohypothalamic DA neurons is mediated by 5HT neurons; but 5,7-dihydroxytryptamine-induced lesions of 5HT neurons did not alter the ability of morphine to increase DOPAC concentrations in MZI and DMN. These results indicate that the stimulatory effects of mu opioid receptor activation on incertohypothalamic DA neurons is not dependent upon the presence of 5HT neurons.

Effects of immunoneutralization of dynorphin1–17 and dynorphin1–18 on the activity of central dopaminergic neurons in the male rat

The effects of administration of antibodies against dynorphin1-17 (DYN1-17-AB) and dynorphin1-8 (DYN1-8-AB) were examined on the activity of dopaminergic (DA) neurons comprising the nigrostriatal, mesolimbic, tuberoinfundibular and periventricular-hypophysial systems in the male rat brain. DA neuronal activity was estimated by measuring the concentration of the dopamine metabolite 3,4-dihydroxyphenylacetic acid (DOPAC) in brain (striatum, nucleus accumbens, median eminence) and pituitary regions (intermediate lobe) containing terminals of these neurons. The intracerebroventricular administration of either DYN1-17-AB or DYN1-8-AB produced a time-related increase in the activity of tuberoinfundibular and periventricular-hypophysial DA neurons, but failed to alter the activity of nigrostriatal or mesolimbic DA neurons. The ability of both DYN1-17-AB and DYN1-8-AB to enhance the activity of tuberoinfundibular and periventricular-hypophysial DA neurons was reversed by the kappa opioid agonist U-50,488. These results indicate that DYN1-17-AB and DYN1-8-AB, presumably by binding endogenous dynorphins, remove a tonic inhibitory action of these opioid peptides on tuberoinfundibular and periventricular-hypophysial DA neurons.

Evidence that hypothalamic periventricular dopamine neurons innervate the intermediate lobe of the rat pituitary

The purpose of the present study was to provide neurochemical and endocrinological evidence that dopamine (DA) neurons terminating in the intermediate lobe of the rat pituitary originate in the periventricular nucleus of the hypothalamus. One week following surgical separation of the periventricular nucleus from the mediobasal hypothalamus, DA and 3,4-dihydroxyphenyl-acetic acid (DOPAC) concentrations in the intermediate lobe were reduced by 50%, and this was accompanied by an increase in plasma alpha-melanocyte-stimulating hormone (alpha-MSH) concentrations. In contrast, this procedure had no effect on concentrations of prolactin in the plasma, or DA or DOPAC in the median eminence, the region of the mediobasal hypothalamus containing terminals of tuberoinfundibular DA neurons. Electrical stimulation of the periventricular nucleus increased the ratio of DOPAC/DA in the intermediate lobe and reduced the concentrations of alpha-MSH in the plasma, whereas in these same animals the DOPAC/DA ratio in the median eminence and concentrations of prolactin in the plasma were unaltered. These results indicate that approximately 50% of all the DA neurons terminating in the intermediate lobe of the rat pituitary originate in or project through the periventricular nucleus of the hypothalamus, and that these DA neurons regulate the secretion of alpha-MSH from intermediate lobe melanotrophs.

Sexual differences in kappa opioid receptor-mediated regulation of tuberoinfundibular dopaminergic neurons

The purpose of the present study was to examine the acute effects of kappa opioid receptor blockade or activation on the activity of tuberoinfundibular dopaminergic (TIDA) neurons in gonadally-intact or castrated male and female rats. In the absence of drug treatment, the basal activity of TIDA neurons (accumulation of 3,4-dihydroxyphenylalanine, DOPA, in the median eminence after administration of a decarboxylase inhibitor) in male rats was approximately one third of that in diestrous females. In male rats, blockade of kappa opioid receptors following administration of the kappa antagonist norbinaltorphimine (NOR-BNI) increased the activity of TIDA neurons suggesting that these neurons are tonically inhibited by endogenous kappa opioids. By contrast, NOR-BNI had no effect on TIDA neuronal activity in gonadally-intact diestrous female rats, but increased the activity of these neurons in ovariectomized female rats. These results suggest that ovarian hormones block the inhibitory effects of endogenous kappa opioids on the activity of TIDA neurons. Activation of kappa opioid receptors following administration of the kappa agonist U-50,488 caused a dose-related decrease in TIDA neuronal activity in diestrous female rats. U-50,488 had no effect on TIDA neuronal activity in gonadally-intact male rats, but decreased the activity of these neurons in orchidectomized male rats. Taken together, these results reveal a sexual difference in the responsiveness of TIDA neurons to kappa opioid receptor agonists and antagonists, and suggest that gonadal steroid-induced gender differences in the basal activity of TIDA neurons may be due, in part, to differences in tonic inhibitory regulation of these neurons by endogenous kappa opioids.

Evidence that prolactin mediates the stimulatory effects of estrogen on tuberoinfundibular dopamine neurons in female rats

The effects of ovariectomy and estrogen on prolactin secretion and/or the activity of tuberoinfundibular dopamine (TIDA) neurons were examined by either concurrently measuring concentrations of prolactin in plasma and 3,4-dihydroxyphenylacetic acid (DOPAC) in the median eminence of female rats or by determining the rate of DA synthesis (accumulation of 3,4-dihydroxyphenylalanine (DOPA) after the administration of a decarboxylase inhibitor) in the median eminence. For comparison, concentrations of alpha-melanocyte-stimulating hormone (alpha MSH) in plasma and DOPAC in the intermediate lobe of the pituitary (an index of the activity of tuberohypophysial DA neurons) were also determined. Ovariectomy produced a time-dependent decrease in the accumulation of DOPA and the concentrations of DOPAC in the median eminence and prolactin in plasma with maximal effects occurring by 7 days. Estrogen administration to ovariectomized rats increased plasma prolactin and median eminence DOPAC concentrations to levels comparable to those in diestrous controls. In contrast, neither ovariectomy nor estrogen replacement altered the concentrations of alpha MSH in plasma or DOPAC in the intermediate lobe. Administration of the DA agonist bromocriptine blocked the ability of estrogen to increase plasma prolactin and median eminence DOPAC concentrations. Also, administration of antiserum to rat prolactin blocked the stimulatory action of estrogen on median eminence DOPAC concentrations. Taken together, these results indicate that the stimulatory effect of estrogen on the activity of TIDA neurons is mediated by prolactin.

Evidence that histamine-stimulated prolactin secretion is not mediated by an inhibition of tuberoinfundibular dopaminergic neurons

The effects of histamine on prolactin secretion and the activity of tuberoinfundibular dopaminergic (DA) neurons were examined in male rats. Tuberoinfundibular DA neuronal activity was estimated in situ by measuring the metabolism [concentration of 3,4-dihydroxyphenylacetic acid (DOPAC)] and synthesis [accumulation of 3,4-dihydroxyphenylalanine (DOPA) after administration of a decarboxylase inhibitor] of dopamine in the median eminence. Intracerebroventricular (icv) injection of histamine produced a dose- and time-dependent increase in plasma prolactin levels but had no effect on DOPA accumulation or DOPAC concentrations in the median eminence. These results indicate that the stimulation of prolactin secretion following icv histamine is not mediated by an inhibition of tuberoinfundibular DA neurons.

Sexual differences in the activity of periventricular-hypophysial dopaminergic neurons in rats

The activities of periventricular-hypophysial dopaminergic (DA) neurons were compared in male and female rats by measuring dopamine synthesis (accumulation of 3,4-dihydroxyphenylalanine [DOPA] after inhibition of L-aromatic amino acid decarboxylase) and metabolism (concentrations of 3,4-dihydroxyphenylacetic acid [DOPAC]) in terminals of these neurons in the intermediate lobe of the pituitary. For comparison, the synthesis and metabolism of dopamine in the neural lobe of the pituitary and median eminence were also determined. The concentrations of DOPAC and accumulation of DOPA were higher in females than in males in both the intermediate lobe and median eminence, revealing a sexual difference in the basal activity of periventricular-hypophysial and tuberoinfundibular DA neurons. In contrast, there were no differences between male and female rats in activity of DA neurons terminating in the neural lobe. One week following gonadectomy, DOPA accumulation in the median eminence was decreased in females and increased in males, but remained unchanged in the intermediate lobe. These results indicate that sexual differences in the activity of periventricular-hypophysial DA neurons terminating in the intermediate lobe are not dependent upon the presence of circulating gonadal steroids, and in this respect, these neurons differ from tuberoinfundibular DA neurons.

Differential regulation of dopaminergic neurons in the mammalian brain: a brief review

The mammalian brain contains anatomically distinct dopaminergic neuronal systems that subserve a variety of functions which include maintaining postural reflexes, modulating basic psychic processes, and controlling the secretion of hormones from the pituitary. In turn, these various dopaminergic neuronal systems are regulated by different mechanisms that are appropriate for the functions that they control. This is illustrated by comparing the responses to endocrinological and pharmacological manipulations of the nigrostriatal dopaminergic neuronal system that is involved with sensorimotor integration and the tuberoinfundibular dopaminergic neuronal system that tonically inhibits the release of prolactin.

Neurotensin-induced activation of hypothalamic dopaminergic neurons is accompanied by a decrease in pituitary secretion of prolactin and alpha-melanocyte-stimulating hormone

The effects of neurotensin on the activity of hypothalamic tuberoinfundibular and periventricular-hypophysial dopaminergic (DA) neurons, and on the secretion of pituitary hormones that are tonically regulated by these neurons (i.e. prolactin and alpha-melanocyte-stimulating hormone [alpha MSH], respectively) were examined in estrogen-primed ovariectomized rats. The activity of tuberoinfundibular and periventricular-hypophysial DA neurons was estimated by measuring concentrations of the dopamine metabolite 3,4-dihydroxyphenylacetic acid (DOPAC) in the terminals of these neurons in the median eminence and intermediate lobe of the posterior pituitary, respectively. Intracerebroventricular administration of neurotensin caused a dose- and time-related increase in DOPAC concentrations in both the median eminence and intermediate lobe, and a concurrent decrease in plasma levels of prolactin and alpha MSH. These results suggest that neurotensin-induced inhibition of secretion of prolactin and alpha MSH from the pituitary may be due to the stimulatory action of this neuropeptide on the release of dopamine from tuberoinfundibular and periventricular-hypophysial neurons.

Activation of tuberoinfundibular and tuberohypophysial dopamine neurons following intracerebroventricular administration of bombesin

The effect of bombesin on the activity of dopamine (DA) neurons comprising the nigrostriatal, mesolimbic, tuberoinfundibular and tuberohypophysial systems in the male rat was determined by measuring: (1) the accumulation of 3,4-dihydroxyphenylalanine (DOPA) after administration of a decarboxylase inhibitor, and (2) the concentration of the DA metabolite 3,4-dihydroxyphenylacetic acid (DOPAC) in brain (striatum, nucleus accumbens, median eminence) and pituitary regions (intermediate and neural lobes) containing terminals of these neurons. Intracerebroventricular (i.c.v.) injection of bombesin caused a dose- and time-related increase in the activity of DA neurons projecting to the median eminence and intermediate lobe of the pituitary, and a corresponding decrease in the concentrations of prolactin and alpha-melanocyte-stimulating hormone (alpha MSH) in the plasma. In contrast, doses of bombesin up to 10 ng i.c.v. failed to alter the activity of DA neurons terminating in the striatum, nucleus accumbens or neural lobe of the pituitary gland. Equimolar doses of bombesin and gastrin-releasing peptide (GRP), a bombesin-like peptide, increased the concentrations of DOPAC in the median eminence and intermediate lobe of the pituitary, suggesting that GRP-preferring receptors may be responsible for the stimulatory effects of bombesin on DA neuronal activity in these regions. The results of these studies suggest that bombesin increases the activity of tuberoinfundibular and tuberohypophysial DA neurons projecting to the median eminence and intermediate lobe of the pituitary, respectively, and thereby inhibits the secretion of prolactin and alpha MSH.

3-Methoxy-4-hydroxyphenylethyleneglycol concentrations in discrete hypothalamic nuclei reflect the activity of noradrenergic neurons

An analytical technique is described which permits the quantitation of picogram concentrations of 3-methoxy-4-hydroxyphenylethylene-glycol (MHPG) in acid hydrolyzed extracts of microdissected regions of the rat brain, and this procedure is used to determine if alterations in the activity of noradrenergic neurons are reflected by changes in the concentrations of MHPG in the paraventricular nucleus (PVN) and supraoptic nucleus (SON) of the rat hypothalamus. MHPG was not detected in non-hydrolyzed samples of either the PVN or SON, but following acid hydrolysis (heating of samples at 94 degrees C for 5 min in 0.16 M perchloric acid) MHPG was detected in both of these regions. These results indicate that MHPG exists primarily as a conjugate in the PVN and SON. Neurotoxin-induced lesions of the ventral noradrenergic bundle decreased norepinephrine (NE) and MHPG concentrations in the PVN and SON, demonstrating that tissue levels of MHPG in these brain regions are dependent upon the presence of noradrenergic neurons. Electrical stimulation of the locus coeruleus increased MHPG concentrations in the PVN, but not in the SON, whereas electrical stimulation of the medial forebrain bundle increased MHPG concentrations in both of these regions. The alpha 2-adrenergic receptor antagonist idazoxan increased, while the alpha 2-adrenergic receptor agonist clonidine decreased MHPG concentrations in both the PVN and SON, but neither idazoxan nor clonidine altered NE concentrations in these regions. Immobilization of rats in the supine position increased MHPG concentrations in the PVN and SON, and this was accompanied by a decrease in NE concentrations in the SON.(ABSTRACT TRUNCATED AT 250 WORDS)

Contribution of noradrenergic neurons to 3,4-dihydroxyphenylacetic acid concentrations in the regions of the rat brain containing incertohypothalamic dopaminergic neurons

The purpose of this study was to determine the source of 3,4-dihydroxyphenylacetic acid (DOPAC) in medial zona incerta (MZI) and dorsomedial nucleus (DMN), with the overall aim of ascertaining whether alterations in the concentration of this dopamine (DA) metabolite reflect the activity of incertohypothalamic dopaminergic neurons. In both the MZI and DMN, the concentration of norepinephrine (NE) exceeds that of DA, reflecting a higher density of noradrenergic vs. dopaminergic neurons in these brain regions. The ratio of DOPAC to DA was greater than the ratio of 3-methoxy-4-hydroxyphenylethyleneglycol (MHPG) to NE indicating that the activity of dopaminergic neurons in the MZI and DMN is greater than that of noradrenergic neurons. Destruction of noradrenergic neuronal axons in the ventral bundle following bilateral injections of the neurotoxin 5-amino-2,4-dihydroxy-alpha-methylphenylethylamine (5-ADMP) decreased NE concentrations in the MZI and DMN, but had no effect on the concentrations of DA or DOPAC, revealing that under basal conditions noradrenergic neurons contribute little to DOPAC concentrations in these brain regions. The DA receptor antagonist haloperidol increased, while the DA receptor agonist apomorphine decreased DOPAC concentrations in the MZI and DMN, indicating that alterations in the activity of incertohypothalamic dopaminergic neurons are accompanied by corresponding changes in the concentration of this DA metabolite. On the other hand, activation of noradrenergic neurons following administration of the alpha 2-adrenergic receptor antagonist idazoxan increased DOPAC concentrations in both the MZI and DMN in intact, but not in ventral bundle-lesioned rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of testosterone in the regulation of tuberoinfundibular dopaminergic neurons in the male rat

The effects of testosterone on the tuberoinfundibular dopamine (DA) neuronal activity was examined by determining the rate of DA synthesis-accumulation of 3,4-dihydroxyphenylalanine (DOPA) after administration of a decarboxylase inhibitor and the concentration of a DA metabolite,--3,4-dihydroxyphenylacetic acid (DOPAC)--in the median eminence in the male rat. Within 1 week after orchidectomy, there was an increase in the accumulation of DOPA and the concentration of DOPAC in the median eminence, but there was no change in the concentration of DA. Conversely, 1 day after testosterone administration to orchidectomized rats, the elevated DOPAC concentrations in the median eminence returned to levels comparable to those in gonadally intact rats. Neither orchidectomy nor testosterone replacement had any effect on plasma prolactin concentrations, but inhibition of prolactin secretion following administration of the DA agonist bromocriptine blocked the increase in DOPA accumulation in the median eminence of orchidectomized rats; this latter effect was reversed by intracerebroventricular administration of prolactin. On the other hand, intracerebroventricular injection of prolactin caused a similar increase in the accumulation of DOPA in the median eminence of gonadally intact, orchidectomized, and testosterone-treated orchidectomized rats. Immobilization stress decreased the accumulation of DOPA and the concentration of DOPAC in the median eminence of orchidectomized rats, but had no effect in intact or testosterone-treated orchidectomized rats. These results indicate that testosterone inhibits the basal activity of tuberoinfundibular DA neurons and blocks the inhibitory effects of physical restraint on these neurons, but does not alter the ability of these neurons to respond to delayed activation by prolactin.

Noradrenergic innervation to the VMN or MPN is not necessary for lordosis

The purpose of the present study was to determine the importance of noradrenergic neurons terminating in the ventromedial nucleus (VMN) and medial preoptic nucleus (MPN) of the hypothalamus for lordosis behavior in ovariectomized, estrogen/progesterone-treated female rats. Seven days following bilateral injections of the noradrenergic neurotoxin 5-amino-2,4-dihydroxy-alpha-methylphenylethylamine (5-ADMP) into the ventral noradrenergic bundle (VNAB), norepinephrine (NE) concentrations (ng/mg protein) were reduced to 30-35% of control in the VMN and MPN. 5-ADMP-induced lesions of the VNAB also reduced lordosis quotients in these animals, and this effect was reversed by intracerebral ventricular administration of the alpha 1-adrenergic receptor agonist phenylephrine. These results indicate that neurotoxin-induced disruption of noradrenergic neurons in the VNAB is associated with a deficit in sexual receptivity in female rats. To determine if the reduction in sexual receptivity following 5-ADMP-induced lesions of the VNAB resulted from loss of noradrenergic neuronal projections specifically to the VMN or MPN, lordosis quotients were determined in ovariectomized, estrogen/progesterone-treated rats in which noradrenergic terminals in these hypothalamic nuclei were selectively lesioned. Injection of 5-ADMP directly into either the VMN or MPN reduced NE concentrations to 17% of control in these hypothalamic nuclei, but failed to alter lordosis. Furthermore, injection of phenylephrine into either the VMN or MPN of VNAB-lesioned rats failed to reinstate lordosis to the levels comparable to sham-lesioned controls. Taken together, these results indicate that noradrenergic neurons terminating in either the VMN or MPN are not essential for gonadal steroid induction of sexual receptivity in ovariectomized female rats.

The contributing role of condylar resorption to skeletal relapse following mandibular advancement surgery: report of five cases

The contribution of condylar resorption to relapse following mandibular advancement surgery has not been fully evaluated, yet may contribute substantially to postoperative occlusal and skeletal changes too often considered simply as "relapse." Five cases showing a typical relapse pattern are presented, illustrating the role of condylar resorption. Preoperative factors that may contribute to the development of condylar resorption (age, sex, high preoperative mandibular plane angle, and the presence of preoperative temporomandibular joint disease), as well as intraoperative and postoperative factors, are discussed. A target group is defined in which special considerations should be made with regard to preoperative and postoperative management.

Temperature effects on serum prolactin concentrations and activity of dopaminergic neurons in the infundibulum/pituitary stalk of calves

The effects of ambient temperature on serum concentrations of prolactin and neurochemical estimates of activity of dopaminergic neurons projecting to the infundibulum/pituitary stalk were investigated in Holstein bull calves. Accumulation of 3,4-dihydroxyphenylalanine (DOPA) in the infundibulum/pituitary stalk after intravenous injection of a decarboxylase inhibitor was used to estimate activity of these dopaminergic neurons. Increasing ambient temperature from 21 to 33 degrees C for 22 hr increased serum concentrations of prolactin and decreased activity of the dopaminergic neurons. Conversely, reducing ambient temperature from 22 degrees C to 11 degrees C decreased serum concentrations of prolactin and increased activity of these dopaminergic neurons. It is suggested that alterations in activity of dopaminergic neurons terminating in the infundibulum/pituitary stalk of bull calves may mediate acute temperature-induced changes in secretion of prolactin.

Effects of photoperiod on lactotrophs and on dopaminergic and 5-hydroxytryptaminergic neurones in bull calves

This study was conducted to determine whether photoperiod-induced changes in serum concentrations of prolactin in cattle were associated with changes in activity of dopamine or 5-hydroxytryptamine (5-HT) neurones in the infundibulum/pituitary stalk and the secretion rate and number of lactotrophs in the anterior pituitary gland. Sixteen prepubertal bull calves (approximately 8 weeks of age) were divided into two groups. One group of eight was maintained on a photoperiod of 8 h light: 16 h darkness (8L:16D) and the other group was exposed to 16L:8D for 4 weeks. At this time calves were injected with a decarboxylase inhibitor (m-hydroxybenzylhydrazine dihydrochloride, NSD 1015) which blocks the conversion of dihydroxyphenylalanine (DOPA) to dopamine and of 5-hydroxytryptophan (5-HTP) to 5-HT. Calves were killed with pentobarbital 15 min later. Accumulations of DOPA and 5-HTP in selected brain regions were used as indices of activity of dopamine and 5-HT neurones respectively. Secretory rate and number of prolactin-secreting lactotrophs were determined by reverse haemolytic plaque assay. Relative to calves exposed to 8L:16D, exposure to 16L:8D increased serum concentrations of prolactin by eightfold, anterior pituitary gland weight by 23%, release of prolactin from pituitary explants by 57% and the area of the plaque for prolactin-secreting lactotrophs by 70%. There was no difference in the rates of accumulation of DOPA and 5-HTP in the infundibulum/pituitary stalk of animals exposed to 4 weeks of 16L:8D or 8L:16D.(ABSTRACT TRUNCATED AT 250 WORDS)

Kappa opioid receptor-mediated regulation of dopaminergic neurons in the rat brain

The effect of the kappa opioid receptor agonist U-50,488 [trans-3,4-dichloro-N-methyl-N-[2-pyrrolindinyl)-cyclohexyl]-benze ne- acetamide] was examined on the activity of dopamine (DA) neurons comprising the nigrostriatal, mesolimbic, tuberoinfundibular and tuberohypophysial systems in the male rat brain under basal and stimulated conditions. DA neuronal activity was estimated by measuring: 1) the accumulation of 3,4-dihydroxyphenylalanine after administration of a decarboxylase inhibitor and 2) the concentration of the DA metabolite 3,4-dihydroxyphenyla-cetic acid in brain (striatum, nucleus accumbens and median eminence) and pituitary regions (intermediate lobe and neural lobe) containing terminals of these neurons. Under basal (non-stimulated) conditions, U-50,488 produced a dose- and time-related decrease in the activity of tuberohypophysial DA neurons, but failed to alter the activity of nigrostriatal, mesolimbic or tuberoinfundibular DA neurons. The ability of U-50,488 to inhibit the basal activity of tuberohypophysial DA neurons was blocked by pretreatment with the kappa opioid antagonist nor-binaltorphimine. The activity of nigrostriatal, mesolimbic and intermediate lobe tuberohypophysial DA neurons was increased by haloperidol, whereas the activity of tuberoinfundibular DA neurons was increased by prolactin. U-50,488 decreased the activity of nigrostriatal, mesolimbic and tuberohypophysial DA neurons in haloperidol-treated rats, and decreased the activity of tuberoinfundibular DA neurons in prolactin-treated rats. These results indicate that activation of kappa opioid receptors inhibits all DA neuronal systems in the brain, but that this effect on nigrostriatal, mesolimbic and tuberoinfundibular DA neurons is evident only after these neurons have been activated.

Activation of tuberohypophysial dopamine neurons following intracerebroventricular administration of the selective kappa opioid receptor antagonist NOR-binaltorphimine

The effect of the kappa opioid receptor antagonist nor-binaltorphimine (NOR-BNI) was examined on the activity of dopamine (DA) neurons comprising the nigrostriatal, mesolimbic, and tuberohypophysial systems in the male rat. DA neuronal activity was estimated by measuring: (1) the concentration of the DA metabolite 3,4-dihydroxyphenylacetic acid and, (2) the accumulation of 3,4-dihydroxyphenylalanine after administration of a decarboxylase inhibitor in brain (striatum, nucleus accumbens) and pituitary regions (intermediate lobe, neural lobe) containing terminals of these neurons. The intracerebroventricular administration of NOR-BNI produced a dose- and time-related increase in the activity of tuberohypophysial DA neurons, but failed to alter the activity of nigrostriatal or mesolimbic DA neurons. The ability of NOR-BNI to enhance the activity of tuberohypophysial DA neurons was blocked by the kappa opioid agonist U-50,488. These results indicate that NOR-BNI, acting on kappa opioid receptors, activates tuberohypophysial DA neurons projecting to the neural and intermediate lobes of the pituitary.

Recurrent neuroleptic malignant syndrome associated with inv dup(15) and mental retardation

Neuroleptic malignant syndrome (NMS) is an uncommon but serious adverse reaction to neuroleptic drugs. Clinically, it resembles malignant hyperthermia, a pharmacogenetic disorder of anesthesiology. Inv dup(15) is a rare but underrecognized cause of mental retardation among institutionalized patients. NMS and inv dup(15) have not been previously reported together. Their association should encourage clinicians to search for genetic markers for NMS.

Stress-induced secretion of alpha-melanocyte-stimulating hormone is accompanied by a decrease in the activity of tuberohypophysial dopaminergic neurons

The purpose of the present study was to examine the acute effects of stress on the secretion of alpha-melanocyte-stimulating hormone (alpha MSH) and the activity of tuberohypophysial dopamine (DA) neurons in female and male rats. The activity of tuberohypophysial DA neurons was estimated by measuring the accumulation of 3,4-dihydroxyphenylalanine (DOPA) following administration of the decarboxylase inhibitor NSD 1015, and the concentrations of the DA metabolite 3,4-dihydroxyphenylacetic acid (DOPAC) in the intermediate and neural lobes of the posterior pituitary. The combination of brief (2 min) ether exposure followed by 30 min of supine restraint (immobilization in the supine position) decreased the rate of DOPA accumulation in the intermediate, but not in the neural lobe of both female and male rats. Similarly, brief ether exposure followed by 10, 20 or 30 min of supine restraint increased plasma alpha MSH concentrations and decreased DOPAC concentrations in the intermediate lobe of female and male rats. In the absence of ether, tube restraint (confinement in a cylindrical acrylic tube) increased alpha MSH secretion and decreased intermediate lobe DOPAC concentrations, whereas ether in the absence of physical restraint had no effect. These results suggest that the stress-induced activation of alpha MSH secretion in both female and male rats may be due, in part, to a decrease in the activity of tuberohypophysial DA neurons in the intermediate lobe of the posterior pituitary.

Zonal model of an adaptive mirror

An approximate model of an adaptive optic element is presented which works well for components having many actuators. This zonal model is used to gain insight into the general behavior of systems that correct for high spatial frequency errors. The model is derived from the method of least squares, and considers the nonshift invariant properties of adaptive mirrors. It may be implemented with Fourier transform techniques and is, therefore, easy to program. The relationship between the zonal model and the simpler bandpass filter model of Harvey and Callahan is discussed.

Atrial natriuretic peptide-induced suppression of basal and dehydration-induced vasopressin secretion is not mediated by hypothalamic tuberohypophysial or tuberoinfundibular dopaminergic neurons

The purpose of this study was to examine the effects of atrial natriuretic peptide (ANP) on the secretion of vasopressin and the activities of hypothalamic tuberohypophysial and tuberoinfundibular dopaminergic neurons in normal and dehydrated male rats. Neuronal activity was estimated by measuring the concentrations of 3,4-dihydroxyphenylacetic acid (DOPAC) and dopamine (DA) in brain and posterior pituitary regions containing terminals of tuberohypophysial (neural lobe; intermediate lobe) and tuberoinfundibular (median eminence) DA neurons. Intracerebroventricular (icv) administration of 20 micrograms ANP decreased basal arginine vasopressin concentrations in the plasma, but had no effect on the concentrations of DOPAC or DA in any region examined. Water deprivation caused a time-dependent increase in plasma arginine vasopressin concentrations, with maximal levels measured 2 days after removal of water bottles. Water deprivation had no effect on DOPAC concentrations in the neural lobe, intermediate lobe or median eminence, but increased DA concentrations in the neural lobe. ANP (20 micrograms/rat; icv) decreased arginine vasopressin concentrations in the plasma of water-deprived rats without altering DOPAC or DA concentrations in the neural lobe, intermediate lobe or median eminence. These results indicate that ANP-induced suppression of basal and dehydration-induced vasopressin secretion is not mediated by tuberohypophysial or tuberoinfundibular DA neurons.

Kappa-opioid-receptor-mediated regulation of alpha-melanocyte-stimulating hormone secretion and tuberohypophyseal dopaminergic neuronal activity

The effects of the kappa-opioid receptor agonist trans-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)cyclohexyl]-benzene- acetamide methanesulfonate hydrate (U-50488) were examined on alpha-melanocyte-stimulating hormone (alpha-MSH) secretion and the activity of tuberohypophysial dopamine (DA) neurons in the male rat. Tuberohypophysial DA neuronal activity was estimated by measuring: (1) the rate of DA synthesis [accumulation of 3,4-dihydroxyphenylalanine (DOPA) following inhibition of aromatic L-amino acid decarboxylase], and (2) DA metabolism [concentrations of 3,4-dihydroxyphenylacetic acid (DOPAC)] in the intermediate lobe of the pituitary. U-50488 produced a dose- and time-dependent increase in plasma concentrations of alpha-MSH which was accompanied by a decrease in the accumulation of DOPA and in the intermediate lobe. The effects of U-50488 were blocked by pretreatment with the DA agonist apomorphine but not by the beta-adrenergic antagonist propranolol. The effects of U-50488 on plasma alpha-MSH concentrations and intermediate-lobe DOPA accumulation were blocked by pretreatment with the selective kappa-opioid receptor antagonist nor-binaltorphimine. These results indicate that U-50488, by acting on kappa-opioid receptors, inhibits the activity of intermediate-lobe tuberohypophysial DA neurons, and through this action increases the secretion of alpha-MSH from melanotrophs.

Dopaminergic and beta-adrenergic receptor control of alpha-melanocyte-stimulating hormone secretion during stress

The relative roles of dopaminergic and beta-adrenergic receptors in mediating the stress-induced increase in the secretion of alpha-melanocyte-stimulating hormone (alpha-MSH) from the intermediate lobe of the pituitary were determined in the male rat. Thirty minutes of physical immobilization (restraint stress) increased the circulating concentrations of alpha-MSH and decreased the 3,4-dihydroxyphenylacetic acid/dopamine (DOPAC/DA) ratio in the intermediate lobe of the pituitary, reflecting a decrease in the tuberohypophysial dopaminergic neuronal activity. Pretreatment with the beta-adrenergic antagonist propranolol reduced the stress-induced increase in the circulating levels of alpha-MSH, but had no effect on the basal plasma concentrations of this hormone or the stress-induced decrease in DOPAC/DA in the intermediate lobe. If the dopaminergic tone during stress was maintained by administration of the DA agonist apomorphine, the stress-induced increase in alpha-MSH secretion was prevented. In nonstressed animals the administration of the beta 2-adrenergic agonist metaproterenol increased the plasma levels of alpha-MSH, and the effect of this drug was augmented if the inhibitory dopaminergic tone on alpha-MSH secretion was blocked by the administration of the DA antagonist haloperidol. Severing neurons in the retrochiasmatic region of the hypothalamus blocked the stress-induced decrease in DOPAC/DA in the intermediate lobe and attenuated the stress-induced increase in plasma concentrations of alpha-MSH. Taken together, these results indicate that a decrease in tuberohypophysial dopaminergic neuronal inhibitory tone and an increase in beta-adrenergic stimulation are both necessary for the full expression of the stress-induced increase in secretion of alpha-MSH from melanotrophs in the intermediate lobe of the rat pituitary.

Comparison of the effects of ether and restraint stress on the activity of tuberoinfundibular dopaminergic neurons in female and male rats

The purpose of the present study was to characterize the acute inhibitory effects of restraint stress on the activity of tuberoinfundibular dopamine (DA) neurons as estimated by measuring concentrations of 3,4-dihydroxyphenylacetic acid (DOPAC) in the median eminence. The time course of the effects of two types of physical restraint (immobilization in the supine position or confinement in an acrylic cylindrical tube) was determined in unanesthetized and diethylether (ether)-exposed female and male rats. The combination of brief (2 min) exposure to ether followed by 10 and 20 min of supine restraint increased concentrations of prolactin in plasma and decreased DOPAC concentrations in median eminence of both female and male rats. Thirty minutes of supine restraint decreased DOPAC concentrations in the median eminence of female rats that were not exposed to ether, and brief exposure to ether enhanced this effect. By contrast, 30 min of supine restraint failed to alter DOPAC concentrations in the median eminence in either unanesthetized or ether-exposed male rats. Tube restraint in the absence of ether failed to alter DOPAC concentrations in the median eminence of either female or male rats; but in female rats preexposed to ether, 30 min of tube restraint decreased DOPAC concentrations in the median eminence. On the other hand, in the absence of physical restraint, 2 min ether exposure caused a transient increase in prolactin secretion and a concurrent decrease of DOPAC concentrations in median eminence of both female and male rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Rotationally symmetric construction optics for a waveguide focusing grating

Waveguide grating couplers have been under study as a method of focusing laser diode radiation on the surface of an optical data storage device. In this letter, we describe a simple method of holographically constructing a waveguide grating coupler at visible wavelengths which may be used with collimated infrared laser radiation to form high numerical aperture, diffraction limited beams. The design method includes the necessary compensation aberrations to offset the effects of differences between construction and end-use wavelengths.

Activation of tuberoinfundibular but not tuberohypophysial dopaminergic neurons following intracerebroventricular administration of alpha-melanocyte-stimulating hormone

The effect of alpha-melanocyte-stimulating hormone (alpha MSH) on the activity of different central dopaminergic neurons in the male rat was determined by measuring the concentration of 3,4-dihydroxyphenylacetic acid (DOPAC) and the accumulation of 3,4-dihydroxyphenylalanine (DOPA) following the administration of a decarboxylase inhibitor in brain regions that contain terminals of nigrostriatal (striatum), mesolimbic (nucleus accumbens), tuberoinfundibular (median eminence) and tuberohypophysial (neural and intermediate lobe of the pituitary) dopaminergic neurons. Intracerebroventricular (i.c.v.) administration of alpha MSH caused a prompt (within 30 min) increase in the concentration of DOPAC and the accumulation of DOPA in the median eminence, but was without effect in the other brain regions. The alpha MSH-induced increase in tuberoinfundibular dopaminergic neuronal activity was temporally related to a decrease in circulating concentrations of prolactin. Twelve hours after the i.c.v. administration of prolactin DOPA accumulation increased in the median eminence but not in the neural or intermediate lobes of the pituitary. DOPA accumulation was not altered in any brain region 12 h after the i.c.v. administration of alpha MSH. These results suggest that alpha MSH acts acutely to selectively activate tuberoinfundibular dopaminergic neurons and thereby cause the secretion of prolactin from the anterior pituitary to decrease.

Prolactin regulation of dopaminergic neurons in the infundibulum pituitary stalk of bull calves

The effects of elevated circulating concentrations of prolactin were examined on neurochemical estimates of activity of dopaminergic neurons in the infundibulum/pituitary stalk of Holstein bull calves (8-10 weeks of age). Activity of these neurons was estimated by measuring the accumulation of dihydroxyphenylalanine, the immediate precursor of dopamine, 15 min after an intravenous injection of the aromatic L-amino acid decarboxylase inhibitor, 3-hydroxybenzylhydrazine. Subcutaneous injections of the dopamine antagonist haloperidol every 6 hr for 1 day increased serum concentrations of prolactin and accumulation of dihydroxyphenylalanine in the infundibulum/stalk. Intravenous infusions of prolactin for 1 or 9 days increased accumulation of dihydroxyphenylalanine in the infundibulum/stalk, indicating that these neurons remain responsive to elevated prolactin for at least 9 days. It is concluded that elevated concentrations of prolactin in blood stimulate dopaminergic neurons in the infundibulum/pituitary stalk of bull calves. We speculate that these neurons may be analogous to the tuberoinfundibular dopaminergic neurons that regulate prolactin in rats.

3,4-Dihydroxyphenylacetic acid concentrations in the intermediate lobe and neural lobe of the posterior pituitary gland as an index of tuberohypophysial dopaminergic neuronal activity

Tuberohypophysial dopamine (DA) neurons terminate in the intermediate and neural lobes of the posterior pituitary. The objective of this study was to determine if concentrations of 3,4-dihydroxyphenylacetic acid (DOPAC), a major metabolite of DA in these regions, reflect the activity of tuberohypophysial DA neurons. The concentrations of DOPAC and DA in the intermediate lobe were approximately twice those in the neural lobe, so that the ratios of DOPAC/DA were similar between lobes. The administration of a monoamine oxidase inhibitor pargyline produced a rapid decline (by 5 min) of DOPAC concentrations in both the intermediate and neural lobes. The administration of nomifensine, an inhibitor of DA uptake at the nerve terminal, produced a modest 33% decline in DOPAC concentrations in the intermediate lobe, but was without effect in the neural lobe. Activation of tuberohypophysial DA neurons by electrical stimulation of the pituitary stalk increased both the rate of DA synthesis (accumulation of dihydroxyphenylalanine (DOPA) after administration of the decarboxylase inhibitor NSD 1015) and the concentrations of DOPAC in the intermediate and neural lobes. Administration of the DA antagonist haloperidol increased, and the DA agonist apomorphine decreased both the rate of DOPA accumulation and DOPAC concentrations in the intermediate lobe but not the neural lobe. The results of the present study demonstrate that: (1) elimination of DOPAC from the intermediate lobe and neural lobe is rapid and alterations in DOPAC concentrations reflect dynamic changes in metabolism of DA; (2) DA which is released and recaptured is a minor contributor to DOPAC concentrations; and (3) alterations in the activity of tuberohypophysial DA neurons are accompanied by corresponding changes in DOPAC concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)

Alterations in concentrations of dihydroxyphenylacetic acid in the median eminence of rats euthanatized with pentobarbital

Concentrations of dopamine (DA) and one of its major metabolites, dihydroxyphenylacetic acid (DOPAC), were determined in selected brain regions of rats that were euthanatized either by decapitation or by intravenous injections of pentobarbital or Fatal Plus, a commercial preparation that contains pentobarbital. When compared with values in decapitated brains, pentobarbital increased the concentration of DOPAC in the median eminence, which contains terminals of tuberoinfundibular dopaminergic (TIDA) neurons. Fifteen minutes of restraint reduced the concentration of DOPAC in the median eminence of rats killed by decapitation or by injections of pentobarbital, indicating that pentobarbital does not mask restraint-induced decrease in TIDA neuronal activity. In contrast, none of the manipulations altered DA or DOPAC concentrations in the striatum, which contains terminals of nigrostriatal dopaminergic neurons. Thus, changes in the concentrations of DOPAC in the median eminence (an index of TIDA neuronal activity) induced by stress can be detected in rats euthanatized by either decapitation or an injection of pentobarbital.

Autoradiographic identification of prolactin binding sites in rat median eminence

Binding sites for prolactin were localized and quantified in the female rat brain by in vitro autoradiographic analysis with iodine-125-labeled ovine prolactin. Following incubation, labeled prolactin bound preferentially to the median eminence and choroid plexus of the lateral and third ventricles. The addition of excess unlabeled ovine prolactin blocked binding of the labeled hormone in the choroid plexus, and attenuated prolactin binding in the median eminence. These results provide evidence for median eminence. These results provide evidence for prolactin-specific recognition sites in the median eminence, a region intimately involved in the hypothalamic regulation of prolactin secretion.

A sex difference in the stimulatory afferent regulation of tuberoinfundibular dopaminergic neuronal activity

The involvement of afferent neuronal systems in the maintenance of basal and prolactin-stimulated tuberoinfundibular dopaminergic (TIDA) neuronal activity was examined in female and male rats. The synthesis and turnover of dopamine (DA) was measured in the median eminence, the terminal region of the TIDA neurons, to estimate the activity of these neurons. Complete and retrochiasmatic deafferentations of the mediobasal hypothalamus were made 7 days prior to experimentation to either completely isolate the TIDA neurons from the rest of the brain or to interrupt neuronal connections from rostral brain regions to the TIDA neurons, respectively. Both complete and retrochiasmatic deafferentations decreased the basal rate of DA synthesis and turnover in the median eminence of female, but not of male rats. These results suggest that neuronal afferents originating rostral to the mediobasal hypothalamus stimulate TIDA neurons in the female but not in the male rat. Intracerebroventricular administration of rat prolactin increased DA synthesis in the median eminence of both sham and retrochiasmatic deafferentiated female and male rats showing that the stimulatory action of prolactin is not blocked by retrochiasmatic deafferentation. Ovariectomy reduced the rate of DA synthesis in the median eminence but retrochiasmatic deafferentation did not cause a further decrease in ovariectomized rats. These results suggest that retrochiasmatic deafferentation and ovariectomy may remove a stimulatory input to the TIDA neurons which is mediated through a common afferent neuronal pathway. These afferent influences do not appear to be operational in the adult male rat since retrochiasmatic deafferentation did not reverse the castration-induced increase in the rate of DA synthesis in the median eminence of male rats.

In vitro insertion of leader peptidase into Escherichia coli membrane vesicles

Leader peptidase is an integral protein of the Escherichia coli cytoplasmic membrane whose topology is known. We have taken advantage of this knowledge and available mutants of this enzyme to develop a genetic test for a cell-free protein translocation reaction. We report that leader peptidase inserted into inverted plasma membrane vesicles in its correct transmembrane orientation. We have examined the in vitro membrane assembly characteristics of a variety of leader peptidase mutants and found that domains required for insertion in vivo are also necessary for insertion in vitro. These data demonstrate the physiological validity of the in vitro insertion reaction and strengthen the use of this in vitro protein translocation reaction for the dissection of this complex sorting pathway.

A method to detect rabbit neutrophil phagocytosis of Pasteurella multocida

A method was developed to detect neutrophil phagocytosis of bacteria by determining whether neutrophil-associated bacteria were intra- or extracellular. Neutrophils were treated with 8-(N,N-diethylamino)-octyl-3,4,5-trimethoxybenzoate hydrochloride to inhibit degranulation and, consequently, killing of bacteria. Treated neutrophils and opsonized Pasteurella multocida were combined. Following phagocytosis, the suspensions were centrifuged and the pellets were washed to remove non-cell-associated bacteria. The pellets were resuspended and heparin was added to prevent further phagocytosis. Samples were removed, and the number of viable bacteria was determined by a dilution and plate count technique. Streptomycin, an antibiotic that is poorly taken up by neutrophils, was added to kill extracellular bacteria, and the suspensions were incubated for 20 minutes at 37 C, and samples were removed again and bacterial numbers were determined. Percentage killing of bacteria by streptomycin was calculated. Phagocytosed bacteria were protected from the bactericidal action of streptomycin.

Effects of alterations in the activity of tuberohypophysial dopaminergic neurons on the secretion of alpha-melanocyte stimulating hormone

Administration of gamma-butyrolactone (GBL), an anesthetic which reduces dopaminergic neuronal activity, decreased the concentration of the dopamine (DA) metabolite 3,4-dihydroxyphenylacetic acid (DOPAC) in the intermediate lobe of the pituitary gland, and increased alpha-melanocyte stimulating hormone (alpha MSH) concentrations in the serum of male rats. Bilateral electrical stimulation of the rostral arcuate nucleus, which contains perikarya of tuberohypophysial DA neurons, increased DOPAC concentrations in the intermediate lobe and decreased alpha MSH concentrations in the serum of GBL-anesthetized rats. Administration of the DA antagonist haloperidol prevented the decline in serum alpha MSH levels following arcuate nucleus stimulation, but had no effect on serum alpha MSH concentrations in sham-stimulated GBL-treated rats. These results indicate that GBL-induced decreases or stimulation-induced increases in the activity of tuberohypophysial DA neurons are accompanied by corresponding changes in the metabolism of DA in the intermediate lobe of the rat pituitary gland, and by reciprocal changes in the secretion of alpha MSH.

The anterior hypothalamus provides stimulatory input to tuberoinfundibular dopamine neurons which is not mediated by prolactin

Complete or retrochiasmatic deafferentations of the mediobasal hypothalamus were made in female rats 7 days prior to experimentation in order to determine the role played by putative afferent neuronal connections (1) in maintaining the basal neuronal activity of tuberoinfundibular dopaminergic (TIDA) neurons, and (2) in the stimulatory actions of prolactin on these neurons. The neuronal activity of TIDA neurons was estimated by measuring the rates of synthesis, turnover or metabolism of dopamine (DA) in the terminals of these neurons in the median eminence. Complete deafferentation of the mediobasal hypothalamus reduced the basal rate of DA synthesis, and retrochiasmatic deafferentation decreased the rates of synthesis, turnover and metabolism of DA in the median eminence. A knife cut 1 mm rostral to the retrochiasmatic cut failed to alter basal TIDA neuronal activity. These results suggest that afferent neuronal inputs originating in or coursing through the caudal portion of the anterior hypothalamus mediate a tonic stimulatory influence on TIDA neurons in the female rat. Intracerebroventricular administration of rat prolactin or systemic administration of haloperidol (which increases circulating levels of prolactin) increased DA synthesis in the median eminence of both sham-operated rats and retrochiasmatic-deafferentated rats. Thus, the stimulatory action of prolactin was not blocked by retrochiasmatic deafferentation. In addition, elimination of the basal stimulatory action of endogenous prolactin by pretreating animals with bromocriptine reduced the rate of DA synthesis in the median eminence of both sham- and retrochiasmatic-deafferentated rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Neuroleptics and neuroendocrine function

Neuroleptics have been developed primarily to treat psychoses, but they have become invaluable research tools. Because of their selective action on DA receptors, neuroleptics are commonly employed to study the function and regulation of DA neurotransmission. The relationship between the antipsychotic efficacy and the DA receptor affinity of the various neuroleptic drugs has lead to the development of new DA antagonists in hopes of discovering novel antipsychotic agents. This approach has produced interesting new compounds selective for the DA receptor subtypes. The use of DA receptor antagonism as a measure of the potential antipsychotic efficacy of a compound will undoubtedly change as the mechanisms behind the antipsychotic actions of neuroleptics become better understood. Although endocrine side effects of neuroleptic administration are undesired in the clinic, they have provided insight into the neuroendocrine regulation of pituitary hormones. Through the use of neuroleptics, DA neurons in the hypothalamus have been shown to play a role in the regulation of prolactin, GH, and TSH secretion. The ability of DA to act at the pituitary and thereby inhibit the secretion of these three hormones suggests that other regulatory factors must provide the specificity needed for the differential secretion of the individual hormones during varying physiological states. Future research will certainly explore the interactions of DA and these regulatory factors at the pituitary. The role of DA in neuroendocrine regulation is not limited to the pituitary. The presence of DA neurons within the hypothalamus offers the possibility of DA regulation of hypothalamic neurosecretory activity.

Effect of electrical stimulation of the ventromedial nucleus and the dorsomedial nucleus on the activity of tuberoinfundibular dopaminergic neurons

Perikarya and terminals of tuberoinfundibular dopaminergic (TIDA) neurons are located in the arcuate nucleus (ARN) and in the median eminence (ME), respectively. Dopamine (DA) released from TIDA terminals in the ME inhibits prolactin secretion from the anterior pituitary. Anatomical studies have described the sources of afferents to ARN and ME, but not to TIDA neurons per se. The ventromedial nucleus (VMN) and the dorsomedial nucleus (DMN) of the hypothalamus project to ARN and ME and have a role in prolactin regulation. In the present study, VMN and DMN were investigated as possible sources of TIDA afferents. Alterations in the activity of TIDA neurons were estimated by measuring plasma concentrations of prolactin and the rates of DA synthesis (3,4-dihydroxyphenylalanine - DOPA - accumulation after administration of the decarboxylase inhibitor NSD 1015) and metabolism (concentrations of the DA metabolite 3,4-dihydroxyphenylacetic acid - DOPAC) in the ME following electrical stimulation of ARN, VMN, and DMN in ovariectomized female rats. Thirty minutes of bilateral stimulation of ARN or DMN increased DOPA accumulation in the ME; stimulation of the VMN had no effect. 5-Hydroxytryptamine synthesis in the ME was unaffected by stimulation of any region. Plasma prolactin levels declined during DMN stimulation, varying with the frequency and duration of the electrical stimulus. DA metabolism within TIDA neurons increased with DMN stimulation, as evidenced by increased DOPAC concentrations in the ME. In females whose basal TIDA activity has been increased by haloperidol treatment or decreased by bromocriptine treatment, DMN stimulation was still able to increase DOPA accumulation in the ME. The present data suggest the presence of stimulatory TIDA afferents originating from or passing through the DMN.

Electrical stimulation of the arcuate nucleus increases the metabolism of dopamine in terminals of tuberoinfundibular neurons in the median eminence

The purpose of the present study was to examine the effects of procedures that alter impulse flow in tuberoinfundibular dopamine (DA) neurons on the metabolism of DA in the median eminence and on the secretion of prolactin from the anterior pituitary. Twenty min following the administration of gamma-butyrolactone (GBL, 1000 mg/kg, i.p.) there was a marked decrease in 3,4-dihydroxyphenylacetic acid (DOPAC) concentrations in the median eminence and an increase in prolactin concentrations in the serum, indicating that a decrease in activity of tuberoinfundibular DA neurons is accompanied by a decrease in DA metabolism in the median eminence and a loss of tonic inhibition of pituitary prolactin secretion. Activation of tuberoinfundibular DA neurons by bilateral stimulation of the arcuate nucleus in GBL-treated rats produced a rapid increase in median eminence DOPAC concentrations and a time-dependent decrease in serum prolactin concentrations. Nomifensine (25 mg/kg, i.p., 30 min), a DA uptake inhibitor, had no effect on median eminence DOPAC concentrations in sham- or arcuate nucleus-stimulated rats, indicating that regardless of the level of activity of tuberoinfundibular neurons, very little DA is recaptured and metabolized in terminals of these neurons in the median eminence. Taken together these results reveal that alterations in impulse flow in tuberoinfundibular DA neurons are accompanied by corresponding changes in the metabolism of DA in the median eminence.

The 20-Hz signals of finback whales (Balaenoptera physalus)

The 20-Hz signals of finback whales (Balaenoptera physalus) were analyzed from more than 25 years of recordings at a variety of geographic locations on near-surface hydrophones close to whales and on deep hydrophone systems. These signals were composed of 1-s pulses of sinusoidal waveform with downward sweeping frequency from approximately 23 to 18 Hz at variable source levels up to 186 dB (re: 1 microPa at 1 m), usually with slightly lower levels for the pulses at the beginning and end of sequences. These "20-Hz" pulses were produced in signal bouts (separated by more than 2 h) lasting as long as 32.5 h. Bouts were composed of regularly repeated pulses at intervals of 7-26 s (typically), either at one nominal pulse rate or at two alternating (doublet) pulse intervals. Signal bouts were interrupted by rests of 1-20 min at roughly 15-min intervals and by irregular gaps lasting between 20 and 120 min. The distribution of these signals throughout the year and their temporal sequence were analyzed from the continuous drum records of the Bermuda SOFAR Station. Signal bouts occurred during winter, sometimes beginning in September and ending in May. The sound sequences were never exactly replicated. Direct association of the bouts with the reproductive season for this species points to the 20-Hz signals as possible reproductive displays by finback whales.

Effect of electrical stimulation of the arcuate nucleus on neurochemical estimates of tuberoinfundibular and tuberohypophysial dopaminergic neuronal activities

The activity of nigrostriatal dopaminergic neurons has been estimated biochemically by measuring the rates of dopamine (DA) synthesis (accumulation of dihydroxyphenylalanine (DOPA) after NSD 1015) and turnover (decline of DA concentrations after alpha-methyltyrosine) in the striatum. It has been assumed that the activities of tuberoinfundibular dopaminergic (TIDA) and tuberohypophysial dopaminergic (THDA) neurons can also be estimated by making the same measurements in the terminals of these neurons in the median eminence and the posterior pituitary, respectively. In the present study, this assumption was tested directly by measuring the rates of DA synthesis and turnover in the median eminence and posterior pituitary following electrical stimulation of TIDS and THDA cell bodies in the arcuate nucleus. Electrical stimulation of the arcuate nucleus increased the rate of DOPA accumulation and the alpha-methyltyrosine-induced decline of DA concentrations in the median eminence and in the neural and intermediate lobes of the posterior pituitary. gamma-Butyrolactone (GBL), an anesthetic that selectively inhibits DA impulse flow, reduced the rates of DA synthesis and turnover in the median eminence. GBL also increased prolactin secretion which is tonically inhibited by DA released from TIDA neurons. Serum prolactin levels were significantly decreased by arcuate nucleus stimulation in GBL-anesthetized rats. These results indicate that the rates of DA synthesis and turnover within the median eminence and posterior pituitary reflect the activities of TIDA and THDA neurons, respectively.

The metabolism of dopamine in the median eminence reflects the activity of tuberoinfundibular neurons

The purpose of the present study was to characterize the metabolism of dopamine (DA) in tuberoinfundibular (TI) neurons terminating in the median eminence and to examine the effects of procedures that alter the synthesis and turnover of DA in these neurons on the concentrations of dihydroxyphenylacetic acid (DOPAC) in the median eminence. The DA uptake inhibitor nomifensine (25 mg/kg, i.p.; 30 min) failed to alter median eminence DOPAC concentrations indicating that very little released DA is recaptured and metabolized by TIDA neurons. Within 5 min following the administration of the monoamine oxidase inhibitor pargyline (50 mg/kg, i.v.) median eminence DOPAC concentrations declined to 15% of control demonstrating that this metabolite has a high turnover rate and is rapidly removed from the median eminence. Median eminence DOPAC concentrations in diestrous female rats, whose TIDA neuronal activity is higher than in the male, were two-fold greater than in male rats. Prolactin (10 micrograms/rat, i.c.v.; 12 h), which increases TIDA neuronal activity, produced a corresponding increase in median eminence DOPAC concentrations in male rats. Restraint stress (30 min), which decreases TIDA neuronal activity, produced a corresponding decrease in median eminence DOPAC concentrations in diestrous female rats. The results from the present study suggest that DOPAC concentrations in the median eminence can be used as an index of TIDA neuronal activity.

Determination of the source of 5-hydroxytryptaminergic neuronal projections to the neural and intermediate lobes of the rat pituitary gland through the use of electrical stimulation and lesioning experiments

5-Hydroxytryptamine (5-HT)-containing axons and terminals have been visualized in the neural and intermediate lobes of the rat pituitary gland, but the origin of these fibers remains in question. This study was designed to determine if 5-HT cell bodies in the brainstem or in the dorsomedial nucleus of the hypothalamus project to either of these pituitary lobes. Since lesions and electrical stimulation of 5-HT cell bodies decrease and increase, respectively, the rate of 5-HT synthesis in regions innervated by these cells, these techniques were employed. The in vivo rate of 5-HT synthesis was determined by quantifying the rate of accumulation of the 5-HT precursor, 5-hydroxytryptophan (5-HTP), in the neural and intermediate lobes of the pituitary gland 30 min after the administration of a decarboxylase inhibitor (NSD 1015, 100 mg/kg, i.p.). The application of 30 min of stimulating current (monophasic cathodal pulses of 1 ms duration and 0.3 mA current delivered at a frequency of 10 Hz) to electrodes implanted in the dorsal and median raphe nuclei increased the rate of 5-HT synthesis in both the neural and intermediate lobes of the pituitary gland. 5,7-Dihydroxytryptamine lesions of these nuclei altered neither 5-HTP accumulation nor 5-HT concentrations in the neural and intermediate lobes, but similar lesions of the nuclei raphe pontis and raphe magnus decreased both the concentration of 5-HT and the accumulation of 5-HTP in these pituitary regions.(ABSTRACT TRUNCATED AT 250 WORDS)