Single Dose Of Reserpine Research Articles

Antidepressant-like effects of barley (Hordeum vulgare) in a mouse model of reserpine-induced depression

Background: Depression is a mental disorder characterized by low mood and loss of pleasure or interest in usual activities and often results in cognitive dysfunction such as impairment of learning and memory. For most of the synthetic antidepressants, severe defects such as narrow spectrum, adverse reactions, high drug price, and easy recurrence exist. Barley is one of the richest sources of antioxidants; therefore, we examined whether barley has an effect on depression, learning, and memory in a mouse model of reserpine-induced depression. Methods: Mice were individually acclimated for 1 week and then treated with barley (200 mg/kg, p. o.) or/and fluoxetine (20 mg/kg, i. p.) for 4 weeks prior to reserpine treatment. Mice were then injected with a single dose of reserpine (2 mg/kg, i. p.) or vehicle (20 mg/kg, i. p.) and assessed for mouse behaviors 1 h prior to tests. Mouse behavior was examined in the forced swimming test, tail suspension test, hole-board test, novel place/object recognition, social interaction test, spontaneous locomotor movement (SLMA), and stereotype movement following completion of the treatment protocol. Results: There was a significant antidepressant-like effect in the forced swimming test among the barley group than in the reserpine-treated group, and these decreases were significantly attenuated to a similar extent by treatment with fluoxetine. The effect of barley on the mean duration of immobility time was significantly attenuated in comparison with the reserpine group (P

The Influences of Reserpine and Imipramine on the 5-HT2 Receptor Binding Site and Its Coupled Second Messenger in Rat Cerebral Cortex

An investigation on the molecular mechanism of depression state, less attention was focused on changes at the intracellular messenger level. In this study the effects of reserpine, a monoamine depletor, and imipramine, an antidepressant, on serotonin-2 (5-HT2) receptor binding and its second messenger system of rat cerebral cortex were studied. The level of inositol 4-monophosphate (IP1) accumulation elicited by 100 microM 5-HT via activation of the 5-HT2 receptor on cerebral cortical slices at twelve hours after a single dose of reserpine (2 mg/kg, i.p.) was significantly higher in treated rats, when compared to that of saline-treated rats; this significant level lasted for at least four days. The level of IP1 accumulation in rat cerebral cortical slices elicited by 100 microM serotonin was higher in the group pretreated with reserpine (0.25 mg/kg/day) sub-chronically for seven days than the group pretreated with normal saline. In the receptor binding study, the maximum binding (B(max)) of 5-HT2 receptor binding was increased, when compared to the corresponding controls; whereas, the dissociation equilibrium constant (K(d)) value of the 5-HT2 receptor was found unchanged in the reserpine treated group. Increases in the sensitivity of phosphoinositol (PI) turnover coupled with the 5-HT2 receptor were also found in the long-term (21 days) low dose (0.1 mg/kg/day) administration of reserpine. However, a long-term administration of imipramine (10 mg/kg/day) reduced the function of the PI turnover coupled with the 5-HT2 receptor. Results obtained from the combined use of reserpine and imipramine demonstrated that this combination was able to antagonize the super-sensitivity of the second messenger responses in 5-HT2 receptor induced by long-term treatment with reserpine. Long-term treatment with reserpine but not imipramine also caused an increase in the B(max) of the 5-HT2 receptor. This up-regulation of the 5-HT2 receptor by reserpine could be antagonized by imipramine, if a combined treatment was employed. However, this combination of imipramine with an additional phospholipid liposome did not enhance or decrease the imipramine's effect on the 5-HT2 receptor, or on its coupled second messenger level. In summary, reserpine induced up-regulation of the postsynaptic monoamine receptor and its coupled second messenger responses (such as IP1 formation). Imipramine was capable of antagonizing these same events in a depression animal model with reserpine. This study demonstrated the dynamic changes and adaptability of the receptor system, followed by changes in PI turnover. The results provide an explanation at the molecular level for the bases of depression and the role of antidepressant drugs effects on those pathological linking elements.

Early Changes in Neuropeptide mRNA Expression in the Striatum Following Reserpine Treatment

Chronic dopamine depletion produces neurochemical changes within the striatum as well as enhanced behavioral and metabolic responses to dopamine agonists. Changes in striatal neuropeptides have been consistently described, including increased expression of preproenkephalin mRNA and decreased expression of preprotachykinin and prodynorphin mRNA. Acute dopamine depletion following treatment with reserpine also produces enhanced behavioral and metabolic responses to agonist treatment which develop rapidly. In the present study, we used in situ hybridization histochemistry to investigate whether acute neurochemical changes occur following reserpine treatment. We evaluated neuropeptide mRNA expression in the striatum and nucleus accumbens at several time points from 6 to 120 h following single doses of reserpine and AMPT. The aim of these studies was to determine if changes in neuropeptide mRNA expression occur following acute dopamine depletion and whether such changes are specific to the striatum. Changes in striatal neuropeptide mRNA expression developed rapidly. Preproenkephalin mRNA expression by striatopallidal neurons was unchanged at 48 h, but increased by 44% at 120 h. Preprotachykinin mRNA expression in striatonigral neurons was increased at 6 h and then fell, with a maximal decrease of 45% at 48 h and partial recovery by 120 h. Prodynorphin mRNA expression was unchanged. Expression of preproenkephalin and preprotachykinin mRNA was also examined in subregions of the striatum and the nucleus accumbens. Expression of preproenkephalin mRNA was uniform in the striatum and higher in the core than the shell of the nucleus accumbens. Preprotachykinin mRNA expression in the striatum was higher in the lateral quadrants and was higher in the shell than in the core of the nucleus accumbens. The changes in neuropeptide mRNA following treatment with reserpine were only found in the striatum. These data provide further evidence for early alterations in neuronal function in the striatum following acute dopamine depletion and suggest that neuropeptide expression by striatonigral neurons may be more rapidly regulated in response to changes in dopamine levels.

Effect of reserpine on behavioural responses to agonists at 5-HT 1A, 5-HT 1B, 5-HT 2A, and 5-HT 2C receptor subtypes

Rats were given a single dose of reserpine (5 mg/kg s.c.) and behavioural responses to agonists at 5-HT receptor subtypes compared with those of control animals 21 days later. The following effects of activating postsynaptic 5-HT 1A receptors by the agonist 8-hydroxy-2-(di- n-propylamino) tetralin (8-OH-DPAT) were significantly increased: tail-flick, reciprocal forepaw treading, flat body posture. The hyperphagic effect of activating presynaptic 5-HT 1A receptors by 8-OH-DPAT tended to increase and hypothermia on activating postsynaptic 5-HT 1A sites tended to decrease. The hyperlocomotor effect of activating 5-HT 1A sites also tended to decrease possibly as a result of a dependence of this response on the known depletion of catecholamines by reserpine. Head shakes on activating 5-HT 2A receptors by 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI) and two effects of activating 5-HT 2C receptors by 1-(3-chlorophenyl) piperazine (mCPP) were significantly increased (hypophagia, anxiety) and a third effect, hypolocomotion tended to increase but hypophagia on activating postsynaptic 5-HT 1B receptors by CP-94, 253 was significantly attenuated. The results are discussed with particular reference to altered 5-HT function in depression.

Effect of reserpine-induced depletion of synaptic dopamine on [11C]raclopride binding to D2-dopamine receptors in the monkey brain.

Positron emission tomography was used to examine the in vivo binding of [11C]raclopride to D2-dopamine (DA) receptors in the striatum of two Cynomolgus monkeys after a single dose of reserpine (1 mg/kg, i.v.). A Scatchard procedure was repeated five times to follow D2 receptor density and apparent affinity for 7 weeks after reserpine. Reserpine-induced depletion of DA lead to a marked increase in [11C]raclopride binding, which was still detectable 20 days after treatment. Scatchard analyses indicated that the measured increase in [11C]raclopride binding reflected an increase in receptor affinity but no evident change in receptor density (Bmax). Thus, the increase in [11C]raclopride binding after reserpine should correspond to a reduced competition with endogenous DA for binding to D2 receptors. The results were used to estimate the DA-induced D2 occupancy to be about 40% at physiological conditions.

Expression and regulation of rat 6-pyruvoyl tetrahydropterin synthase mRNA

6-Pyruvoyl tetrahydropterin synthase catalyzes the second step in the biosynthesis of tetrahydrobiopterin. In the present study, the reverse transcription-polymerase chain reaction technique was used to clone a portion of 6-pyruvoyl tetrahydropterin synthase cDNA from rat pineal gland RNA. The sequence of this cDNA was found to be essentially identical to that previously reported for the rat liver. 6-Pyruvoyl tetrahydropterin synthase mRNA levels in various rat tissues, including the brain, were then analyzed by Northern blot and nuclease protection assay. A single 1.35 kb transcript of 6-pyruvoyl tetrahydropterin synthase mRNA was detected by Northern blot analysis in the rat adrenal gland, brain-stem, and liver. Quantitation by nuclease protection assay demonstrated that 6-pyruvoyl tetrahydropterin synthase mRNA was most abundant in the adrenal gland, kidney, and pineal gland (19.5–25.5 amol/μg RNA). Relatively homogeneous levels of 6-pyruvoyl tetrahydropterin synthase mRNA were found in various brain regions including the cerebellum, substantia nigra and locus coeruleus (4.12–12 amol/μg RNA). In the adrenal gland, 6-pyruvoyl tetrahydropterin synthase and tyrosine hydroxylase mRNAs were elevated between 3 and 4-fold 24 h after a single dose of reserpine (10 mg/kg), a treatment known to increase tetrahydrobiopterin levels in this tissue. This result suggests that although 6-pyruvoyl tetrahydropterin synthase is not believed to be rate-limiting in the tetrahydrobiopterin biosynthetic pathway, control of gene expression for this enzyme may play an essential role in regulating the synthesis of this important cofactor.

Induction of aneuploidy in Chinese hamster oocytes following in vivo treatments with trimethoxybenzoic compounds and their analogues

Many inhibitors of tubulin polymerization have a trimethoxybenzene ring in their molecules. Such trimethoxybenzoic compounds and their analogues may therefore have a potency to induce meiotic nondisjunction of oocytes. In this study, a single dose of reserpine (0.5 μg/g body weight), podophyllotoxin (20.0 μg/g b.w.), trimethoxybenzoic acid (500.0 μg/g b.w.) or vinblastine sulfate (3.0 μg/g b.w.) was injected intraperitoneally to mature female Chinese hamsters at the onset of the first meiotic spindle formation of oocytes. Within 6 h after spontaneous ovulation, MII oocytes were collected from the oviducts for morphological examination and cytogenetic analysis. The incidence of morphologically abnormal oocytes with unusually large first polar body or bodies increased significantly after the treatment with reserpine ( 18 202 ; 8.9%), podophyllotoxin ( 28 172 ; 16.3%) and vinblastine sulfate ( 63 197 ; 32.0%), as compared with the control ( 3 214 ; 1.4%). Chromosome analysis of oocytes revealed that podophyllotoxin and vinblastine sulfate were effective in inducing aneuploidy ( 62 154 ; 40.3% and 128 156 ; 82.1% vs. 3 198 ; 1.5% of the control) by inhibiting the formation of spindle microtubules at the first meiosis. Aneuploids were found more frequently in morphologically abnormal oocytes than in normal oocytes. No aneugenic activity of reserpine and trimethoxybenzoic acid was observed. These results indicate that trimethoxybenzoic compounds do not necessarily exhibit aneugenic activity.

Neural control of dopamine β-hydroxylase in vivo: acute and chronic effects

Reserpine treatment was used to examine whether short- and long-term neural stimulation regulates rat adrenal medullary dopamine β-hydroxylase (DBH, EC 1.14.17.1) through transcriptional activation and to examine the extent of coordinate control of DBH and phenylethanolamine N-methyltransferase (PNMT, EC 2.1.1.28). A single dose of reserpine (10 mg/kg i.p.) elevates DBH mRNA 1.5-fold by 6 h post-injection. Chronic treatment (10 mg/kg i.p., 4 alternate day injections) continues the rise in DBH mRNA, with a peak of 3.4-fold control values after 2 doses of reserpine and a plateau at this level thereafter. Even though DBH mRNA is elevated 6 h after a single injection of reserpine, DBH activity does not change in parallel. A 1.3-fold rise in activity occurs at 24 h post-injection. In contrast, chronic reserpine treatment concommitantly increases DBH activity and mRNA. As observed for DBH mRNA, enzyme activity peaks and plateaus after 2 injections on alternate days. However, the rise in enzymatic activity is less than the rise in mRNA (2.4-fold versus 3.4-fold). Ribosomal loading experiments demonstrate that the DBH mRNA pool is fully utilized for protein synthesis with an apparent decrease in the number of ribosomes loaded per molecule of mRNA. Western analysis and thermal denaturation studies indicate that an altered form of DBH may be expressed. With a single dose of reserpine, the enzyme shows a decline in specific activity while repeated treatment leads to an enzyme with higher specific activity. In both cases, the protein appears to be more stable. Reserpine treatment also markedly elevates adrenal glucocorticoids. A 1.5-fold increment in glucocorticoid receptor mRNA accompanies the corticosteroid rise, with the receptor mRNA peaking at 6 h and remaining at this level thereafter. The up-regulation of glucocorticoid receptor mRNA expression, together with the presence of a putative glucocorticoid response element in the 5′ flanking region of the DBH gene, suggests that neural and hormonal regulatory mechanisms may work in concert to control DBH gene transcription. Finally, by comparison to PNMT, activation of DBH appears to require sustained stimulation of the neural axis, since acute changes in mRNA lead to only minor changes in enzyme expression. Similar to PNMT, continuous neural stimulation increases both DBH mRNA and enzymatic activity. However, the discordance in the magnitude of these indices suggests that other regulatory controls may be important in setting the ultimate limits on DBH expression, glucocorticoids perhaps being one such influence.

Effects of reserpine on the content and uptake of dopamine and noradrenaline in rabbit arteries.

1. Change with time of the content and uptake of dopamine (DA) and noradrenaline (NA) in the renal, superior mesenteric and femoral arteries and abdominal aorta of rabbit after reserpine administration was examined. Endogenous DA and NA were measured by high performance liquid chromatography coupled with electrochemical detector. 2. A single dose of reserpine (3 mg/kg, i.p.) maximally depleted the endogenous DA and NA contents in the four blood vessels 24 h after the administration; the ratios of reductions were 70-90% and approximately 90% of the normal levels, respectively. The DA contents in all four vessels recovered to the normal level within 4 days after reserpine. However, NA content did not recover to the normal levels within 30 days after reserpine except in the mesenteric artery. 3. The activity of dopamine beta-hydroxylase (DBH) significantly increased in all four blood vessels 1 h after reserpine. Although the DBH activity returned to the normal level after 3 days in the mesenteric artery, it returned within 24 h in the other three vessels. 4. [3H]-Dopamine and [3H]-NA uptake were almost completely depressed 1 h after reserpine. The [3H]-NA uptake in four vessels recovered to the normal level 2-14 days after reserpine, and [3H]-DA uptake recovered after 30-45 days. Thus, the endogenous DA content in blood vessels was completely restored although DA uptake and NA content were still affected. 5. These results suggested that the recovery of stored DA after reserpine was faster than that of stored NA and the recovery of DA uptake after reserpine was slower than NA uptake.(ABSTRACT TRUNCATED AT 250 WORDS)

Neural regulation of phenyethanolamine N-methyltransferase in vivo: transcriptional and translational changes

The hypothesis that neural regulation of rat adrenal medullary phenylethanolamine N-methyltransferase (PNMT, EC 2.1.1.28) occurs through transcriptional control is examined by following temporal changes in PNMT mRNA expression using paradigms of acute and chronic reserpine treatment. Concommitant changes in PNMT activity and protein were also measured to determine if reserpine induced changes depend solely on gene activation. Further, changes in adrenal corticosterone were measured to examine whether mRNA and enzyme responses might be mediated via reserpine induced changes in ACTH, and hence, corticosterone. Steady-state levels of PNMT mRNA peaked at ∼ 8-fold normal by 6 h after a single reserpine injection (10 mg/kg i.p.), and then declined to control values. With continued treatment, a second, slower rise occurred after three alternate day injections (∼ 3-fold basal levels). Enzyme activity and protein rose simultaneously but were attenuated in magnitude and time course by comparison to message. With both acute and chronic treatment, activity increased 2.0-fold, peaking at 12 h after a single dose of reserpine and again after four doses of the drug. Protein, as measured by immunotitration, was elevated 1.2-and 1.4-fold, respectively. Adrenal corticosterone rose ∼ 8-fold at 6 h, declined slightly at 12 h, rose again, and remained elevated thereafter. Comparison of the time courses for the various indices demonstrated that the early parallel bursts in PNMT mRNA and corticosterone are consistent with an increase in transcriptional activity. However, subsequent discordant expression in these two indices and concomittant magnitudinal differences in enzyme activity and protein suggest that other regulatory controls may limit the transcriptional activation of PNMT and the expression of active PNMT enzyme. Moreover, these latter controls appear to determine the ultimate limitation on PNMT expression and hence, adrenergic function.

Rapid development of dopaminergic supersensitivity in reserpine-treated rats demonstrated with 14C-2-deoxyglucose autoradiography

Dopaminergic denervation supersensitivity has been implicated in the pathogenesis of levodopa-induced dyskinesias, the most common and limiting side effect in the drug treatment of Parkinson's disease, yet the mechanisms that mediate altered drug sensitivity remain poorly understood. In animals models, one key component of denervation supersensitivity is the enhanced efficacy of selective D1 agonists to stimulate locomotion. In rats with chronic dopamine depletion induced by 6-hydroxydopamine nigral lesion, the increased ability of D1 agonists to stimulate regional cerebral glucose utilization (RCGU) in the substantia nigra pars reticulata (SNr) has provided a metabolic correlate to the heightened motor response. In this study, we used the stimulation of RCGU in the SNr as a sensitive in vivo assay of D1 agonist effect to examine the time course of development of supersensitivity in rats following acute dopamine depletion with single doses of reserpine (5.0 mg/kg, i.p.) and alpha-methyl-p-tyrosine (AMPT; 100 mg/kg, i.p.). The stimulatory effect of the D1 agonist SKF 38393 (30 mg/kg) on RCGU in the SNr was first enhanced 6 hr after reserpine/AMPT injection and was maximally enhanced at 12-24 hr (relative 2-deoxyglucose uptake increased 32-51%; P less than 0.05). The response to SKF 38393 returned to control values 5 d after reserpine/AMPT injection. The single reserpine/AMPT injections depleted striatal dopamine to 1-2% of control values from 3-48 hr postinjection, whereas D1 and D2 dopamine receptor densities were unchanged at 24 hr.(ABSTRACT TRUNCATED AT 250 WORDS)

Colocalization of neurotransmitters analyzed by in situ hybridization

In situ hybridization and Northern blot analysis has been used to analyse in some detail the localization and regulation of the messenger molecules adrenaline, noradrenaline and neuropeptide tyrosine (NPY) within cells of the sympathetic nervous system and the adrenal medulla. In the rat adrenal gland, a novel NPY containing population of ganglion cells was found. Synthetic oligonucleotide probes complementary to mRNA coding for the catecholamine synthesizing enzymes phenylethanolamine N-methyltransferase (PNMT), tyrosine hydroxylase (TH) and NPY were used to analyse the regulation of these genes following administration of the catecholamine depleting drug reserpine. Twenty-four hours after a single dose of reserpine, a differential regulation of PNMT, TH and NPY was found. Thus, a dramatic decrease in PNMT mRNA was observed in the adrenal medulla. In contrast, mRNA for both TH and NPY exhibited an increase. Different regulatory mechanisms may thus operate for these three compounds coexisting in chromaffin cells of the adrenal medulla. The regulation of enzymes and peptides was also studied in human sympathetic ganglia. After brief electrical preganglionic stimulation of thoracic ganglia in humans, in situ hybridization was performed with synthetic oligonucleotide probes complementary to TH, dopamine β-hydroxylase (DBH) and NPY mRNA respectively. A several fold increase in all three mRNAs was found in the principal ganglion cells. The results point to a very rapid regulation of genes involved in signal transmission in the sympathetic nervous system of humans. The results also suggest a novel way to define neuronal projections by visualizing increases in mRNA levels following electrical stimulation.

Increase in galanin and neuropeptide Y mRNA in locus coeruleus following acute reserpine treatment

Galanin and neuropeptide Y are known to coexist with noradrenaline in neurons of the locus coeruleus. Furthermore, reserpine depletes noradrenaline from, and increases the synthesis and activity of the catecholamine- synthesizing enzyme tyrosine hydroxylase in, this nucleus. We have found by in situ hybridization of specific 35S-labelled oligonucleotide probes that a single dose of reserpine (10 mg/kg) induced a significant (70–145%) and long-lasting (up to at least 3 days) increase in the amount of galanin and neuropeptide Y mRNA in the locus coeruleus (along with the characteristic increase in tyrosine hydroxylase mRNA). These results suggest a similar reserpine-sensitive mechanism of galanin, neuropeptide Y and tyrosine hydroxylase gene regulation.

Effects of reserpine on phenylethanolamine N-methyltransferase mRNA levels in rat adrenal gland: Role of steroids

Reserpine treatment has been shown to cause a long-lasting decrease in phenylethanolamine N-methyltransferase mRNA levels and a simultaneous increase in tyrosine hydroxylase and neuropeptide tyrosine mRNA levels in chromaffin cells of rat adrenal medulla. In this study, in situ hybridization histochemistry was used to further investigate factors involved in the differential regulation of the catecholamine synthesizing enzymes and the coexisting peptide neuropeptide tyrosine. Pretreatment with the synthetic glucocorticoid analogue dexamethasone followed by the administration of a single dose of reserpine completely reversed the decrease in phenylethanolamine N-methyltransferase mRNA seen after reserpine treatment alone, but had no effect on the reserpine-induced increase in tyrosine hydroxylase mRNA. Dexamethasone alone did not change phenylethanolamine N-methyltransferase or tyrosine hydroxylase mRNA levels in the adrenal medulla. When reserpine-treated rats were given adrenocorticotropic hormone a partial reversal of the decrease in phenylethanolamine N-methyltransferase mRNA was seen. Furthermore, the reserpine-induced increase in neuropeptide tyrosine mRNA levels was markedly reduced when animals were pretreated with dexamethasone, whereas dexamethasone alone had no effect on neuropeptide tyrosine mRNA levels. The drop in phenylethanolamine N-methyltransferase mRNA levels after reserpine treatment was not due to a depression of the pituitary adrenal axis, since proopiomelanocortin mRNA levels in the anterior pituitary increased and plasma corticosterone levels were stable following reserpine treatment. A possible local regulation within the adrenal gland that may involve the glucocorticoid receptor and/or other factors is discussed.

Enhancement by a single dose of reserpine (plus alpha methyl-p-tyrosine) of the central stimulatory effects evoked by dopamine D-1 and D-2 agonists in the mouse

With the advent of selective dopamine D-1 and D-2 agonists such as SKF38393 (2,3,4,5-tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine HCl) and quinpirole (LY171555, trans-4,4a,5,6,7,8a,9-octahydro-5-propyl-2H-pyrazolo [3,4-g]quinoline), it has become possible to examine the functional role of the two dopamine receptor subtypes as well as their interrelationship. In the present study, we pretreated mice with the granule-depleting agent reserpine (5 mg/kg sc) and tested the mice from 4 h to 10 days later. In all the studies, each mouse also received an injection of the dopamine synthesis inhibitor alpha methyl-p-tyrosine (200 mg/kg ip) 1 h before agonist challenge. Where the reserpine was given 2 or more days before testing, a second dose of reserpine was given 4 h before agonist challenge. While producing no significant locomotor stimulation 4 h after reserpine, SKF38393 produced a dose-dependent increase in coordinated locomotion 24 h and 3 days after the reserpine. Likewise, quinpirole itself produced no significant alteration in activity at 4 h, but significantly increased activity at 24 h and 3 days. The new selective D-1 agonist CY208-243 ((-)-4,6,6a,7,8,12b-hexahydro-7-methyl-indolo [4,3-ab] phenanthridine), unlike SKF38393, produced some increase in activity 4 h after reserpine, but much greater activity was seen 1 and 3 days after reserpine. The enhancement with SKF38393, CY208-243 and quinpirole was most marked 3 days after the reserpine. The behavioural stimulation produced by the mixed D1/D2 agonist apomorphine was also greater 3 days after reserpine pretreatment than after 4 h.(ABSTRACT TRUNCATED AT 250 WORDS)

Further studies on the neurochemical mechanisms mediating differences in ethanol sensitivity in LS and SS mice.

Long-sleep (LS) and short-sleep (SS) lines of mice were selectively bred for differences in CNS sensitivity to ethanol with LS mice exhibiting much greater sensitivity to hypnotic doses of ethanol (4.0-4.5 g/kg) than SS mice. The influence of peripheral and central catecholamine neuronal systems on ethanol sensitivity (sleep time) in LS and SS mice was examined following administration of reserpine, alpha-methyl-p-tyrosine and 6-hydroxydopamine. Ten days after a single dose of reserpine, tyrosine hydroxylase activity was increased in the brain and adrenal gland of LS mice but only in the brain of SS mice relative to untreated mice. Brain catecholamine levels in the reserpine-treated mice were 25-50% lower in both LS and SS mice compared to levels in untreated mice. These changes were associated with a 41% reduction in LS sleep time, but a 90% increase in SS sleep time. SS mice were also more susceptible to the lethal effects of reserpine. The increased mortality of SS mice may relate to a greater degree of reserpine-induced hypothermia and a slower rate of recovery of brain catecholamine levels. Neonatal LS and SS mice treated with 6-hydroxydopamine exhibited increased levels of catecholamines in the locus ceruleus, decreased levels in the cerebellum and unchanged levels in the hypothalamus at 60 days of age. These changes were associated with a modest decrease (10%) in LS sleep time and a marked increase (200%) in SS sleep time. alpha-Methyl-p-tyrosine decreased brain catecholamine levels of both lines by 30-50% while LS sleep times were unchanged and SS sleep times were increased by 45%.(ABSTRACT TRUNCATED AT 250 WORDS)

Long lasting supersensitivity to 5-HT mediated behaviour following monoamine depletion in the rat brain.

The effects of the depletion of 5-hydroxytryptamine (5-HT) in the rat brain upon the 5-HT behavioural syndrome (ejaculatory response, abduction of hind-limbs, forepaw treading, and Straub tail) induced by 5-methoxy-N,N-dimethyltryptamine (1 mg/kg intraperitoneally) were investigated. The 5-HT depletion was produced by p-chlorophenylalanine (PCPA 2 X 200 mg/kg intraperitoneally) or by reserpine (5 mg/kg subcutaneously). It resulted in rapidly developing and long-lasting supersensitivity of the behavioural responses which were enhanced between 2 and 14 days after the PCPA injections and between 1 and 42 days after a single dose of reserpine. The depletion of catecholamines by alpha-methyltyrosine (250 + 125 mg/kg intraperitoneally) had no effect. These results underline the usefulness of the 5-HT mediated behavioural models for studies of changes in 5-HT receptor activity.

Developmental status of sympathetic innervation in relation to calcium accumulation by submandibular gland following reserpine, surgical sympathectomy or cyclocytidine.

Sympathectomy (Sx) of the submandibular gland was induced at various postnatal ages by ip administration of a single dose of reserpine or by unilateral excision of a superior cervical ganglion. If animals were 12 days old or less at the time of drug administration, [Ca] of the submandibular gland was not measurably increased 24 hr later; if rats were 14 days of age or older, [Ca] of the gland 24 hr after reserpine injection was nearly double that of untreated controls. Two days after surgical Sx, [Ca] of the denervated submandibular gland was unchanged from that of the innervated member of a pair if animals were less than 14 days of age at the time of denervation; [Ca] was twice that of glands of control rats if animals were older than 14 days of age when the denervation was performed. The anti-tumor agent, cyclocytidine (CC), given daily for 3 days in an ip dose of 500 mg/kg, also caused a two- to threefold increase in [Ca] of the submandibular gland when rats were more than 12 days of age at the time of the initial injection of the drug, but in rats younger than this age, CC caused no change in the [Ca] of the submandibular gland. Present data show that there are age-related differences in the ability of the submandibular gland to accumulate calcium following sympathetic denervation or treatment with a norepinephrine-releasing drug. These differences may be attributed either to incomplete development of calcium transport mechanisms, or incomplete development of the sympathetic innervation before 14 days of age.

Differences in the ability of reserpine and chlorpromazine to block ovulation throughout the estrous cycle of the rat

Abstract Rats with a 4‐day estrous cycle were given a single dose of reserpine (62.5, 125, 500, 1000 or 2000 μg/kg body wt) or chlorpromazine (1, 2.5 or 5 mg/kg body wt) at 13.00 h on the days of estrus, diestrus 1, diestrus 2 or proestrus and were autopsied on the next expected day of estrus. The doses of reserpine (in μg/kg body wt) necessary to block ovulation during the cycle were 500 at estrus, 62.5 at diestrus 1, 500 at diestrus 2 and 2000 at proestrus, and for chlorpromazine (in μg/kg body wt) 2.5 on diestrus 1 and diestrus 2 and 1 in proestrus. On estrus, at 13.00 h, chlorpromazine was ineffective to block ovulation. A single dose of reserpine (125 μg/kg) or chlorpromazine (2.5 mg/kg) was given at estrus, diestrus 1 or diestrus 2 at 09.00, 13.00, 17.00 or 21.00 h, autopsy again being performed on the next expected day of estrus. The ability of reserpine to block ovulation begins at 17.00 on estrus, reaches its maximum throughout diestrus 1 and disappears at diestrus 2. Chlorpromazine ability to block ovulation appeared to have a circadian rhythm on diestrus 1 and diestrus 2, with a maximum at 13.00 and a minimum at 21.00 h, and no effect on estrus. Hormone replacement (human chorionic gonadotrophin) on diestrus 1, diestrus 2 and proestrus re‐established ovulation in rats whose ovulation was blocked by reserpine on diestrus 1 (125 μg/kg) and had no effect when the replacement was done only on diestrus 1 or diestrus 2. Rats blocked with chlorpromazine (1 mg/kg) on proestrus ovulated 24 hrs after the next expected day of estrus. The weight of the ovaries diminished in almost all rats treated with chlorpromazine, while the effects of reserpine depend on the dose used and the day of the cycle considered. Results obtained in these experiments suggest that the dopaminergic system susceptible to blocking by chlorpromazine, stimulates gonadotrophin control secretion on diestrus 1, diestrus 2 and proestrus. On diestrus 1 and diestrus 2, a circadian rhythm control system linked to dopaminergic system might exist. Blockade induced by reserpine might be related to changes observed in the hypothalamus content of norepinephrine throughout the estrus cycle, and also to the blockade on ovarian innervation exerted by reserpine.

Depletion and recovery of neuronal monoamine storage in rats of different ages treated with reserpine

The effect of reserpine on dopamine, noradrenaline, adrenaline and serotonin concentrations in different brain regions, and the recovery of normal levels of these monoamines after such treatment were studied in rats aged 5, 15 and 27 months. In a preliminary experiment we found that distribution of the drug was not altered in the aged rats. Then we observed that a single dose of reserpine (5 mg/kg IP) had a similar depleting effect on all the brain monoamines, in all the brain regions considered in all three age groups. The curves expressing recovery of monoamine storage in all the nerve terminals, several days after treatment, were superimposable. These results suggest that in the rat, age does not influence the effect of reserpine on the storage mechanism of brain monoamines. Moreover, as restoration of this mechanism depends on the synthesis of new vesicles, the similarity in the rates of recovery in adult, old and very old rats indicated indirectly that synthesis of these neuronal organelles is not affected by aging.