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Aminergic involvement in the control of luteinizing hormone secretion in the domestic fowl
GENERAL
AND
COMPARATIVE
Aminergic
ENDOCRINOLOGY
Involvement in the Control of Luteinizing Secretion in the Domestic Fowl
FRANCES C. BUONOMO,
Departmentof
45, 162- 166 (1981)
Physiology
JAMSHID
RABII,
and the Bureau of Biological Jersey, New Brunswick,
AND
COLIN
Research, Rutgers-The New Jersey 08903
G.
Hormone SCANES
State
University
of New
Accepted January 6, 1981 Neuropharmacologic agents have been used, in vivo, to investigate the possible involvement of the biogenic amines in the hypothalamic control of luteinizing hormone (LH) secretion in the domestic fowl. Inhibitors of norepinephrine (NE)/dopamine (DA) synthesis (for DA/NE a-methyl-p-tyrosine, cr-mpt; for NE diethyldithiocarbamic acid, DDC) and granule reuptake of catecholamines (reserpine) and the cr-adrenergic antagonist (phenoxybenzamine) induced reductions in the circulating concentrations of LH. The administration of p-chlorophenylalanine (an inhibitor of 5hydroxytryptamine (5HT) synthesis) and methysergide (a 5HT antagonist) also depressed plasma levels of LH. Neither /I-adrenergic (propran0101) nor cholinergic (atropine) blockers affected circulating LH levels. These data suggest the involvement of a catecholamine (probably acting via a-adrenergic receptors), together with some serotoninergic components in the hypothalamic control of LH in the chicken.
The involvement of putative neurotransmitters in the hypothalamic control of adenohypophyseal hormone release in mammals has been the subject of intense investigation (reviewed, e.g., Weiner and Ganong, 1978). There is strong evidence that the hypothalamic release of luteinizing hormone releasing hormone (LHRH), and hence LH is provoked by catecholamine(s), probably norepinephrine acting via areceptors (Weiner and Ganong, 1978). This is based on the intraventricular injection of neurotransmitters (Sawyer, 1952; Sawyer et al., 1974; Sawyer, 1979) and upon pharmacological studies using biogenic amine synthesis blockers (Drouva and Gallo, 1976; Kalra and McCann, 1974; Kalra et al., 1972) and agonists and antagonists to neurotransmitters (Sawyer and Radford, 1978; Weick, 1977). In addition, there is evidence for serotonin (5HT) having both positive and negative influences on the hypothalamic control of LH secretion (Gallo and Moberg, 1977; Kamberi et al., 1970; Porter et al., 1971/1972). In birds, there is some evidence for catecholamines having effects on reproductive
function (El Halawani and Burke, 1975; El Halawani et al., 1978), and circulating concentrations of LH (Follett et al., 1977; Davies and Follett, 1974). The present study was designed to provide comprehensive information on the possible role of the biogenic amines in LH secretion in the male domestic fowl. MATERIALS
Animals. Male domestic fowl (White Leghorn) of two ages (young: 6 week old, and adult), were used in these studies. All the birds were maintained on a long daylength (young 16L: 8D; adult 14L: IOD) with free access to food (a commercial diet) and water. Young birds were housed in group cages, whereas the adults were kept in individual cages. Blood samples were taken either by venipuncture from the brachial vein (adult birds), or by decapitation (6-week-old birds). Following centrifugation, plasma was stored at -20” prior to assay. Drugs. The following drugs were employed in this investigation: a-methyl-p-tyrosine methylester (cY-mpt) (Sigma; in saline: 250 mg/kg), diethyldithiocarbamic acid (DDC) (Sigma; in saline: 400 mg/kg), pimozide (McNeil Laboratories: in 2% tartaric acid; 2.5 mg/kg), phenoxybenzamine (Smith, Kline and French; in acid saline; 20 mg/kg), propranolol (Ayerst Laboratories, in saline, 2 mg/kg), atropine sulfate (Sigma; in saline: 10 mg/kg), p-chloropr-enylalanine methyl ester (pCPA)
162 00166480/81/100162-05$01.00/O Copyright All rights
@ 1981 by Academic Press, Inc. of reproduction in any form reserved.
AND METHODS
AMINES
AND
LH
IN THE
(Sigma; in acid saline: 250 mg/kg), methysergide (Sandoz Pharmaceuticals; in 20% ethanolic saline: 2.5 mgkg). All drugs were administered via the intraperitoneal route. Radioimmunoassay. The concentration of LH in the plasma samples was determined by homologous radioimmunoassay (RIA) (Follett et al., 1972). Samples were assayed in duplicate at each of, at least, two concentrations. All samples from a single experiment were assayed in a single RIA to eliminate interassay variance. Statistics. Differences between treatment groups and their respective control were determined by Student’s t test. Differences between pre- and posttreatment plasma LH concentrations were estimated by the paired t test.
reserpine (catecholamine granule reuptake inhibitor) depressed the circulating LH concentrations by 64.8% in adults and 55.3% in young chicks (Table 2). Receptor antagonists exerted variable effects on the circulating LH concentrations. In all cases, phenoxybenzamine (cw-adrenergic antagonist) administration was accompanied by a reduction in the plasma level of LH (Tables 2 and 3). In adult birds, this effect was also observed 30 min following injection (phenoxybenzamine 13.4 ? (n = 7) SEM 2.8, vehicle control 19.9 + (7) 1.1 @ml; P < 0.05). Neither propranolol (p-adrenergic antagonist), nor atropine (cholinergic antagonist) significantly affected circulating LH concentrations (Tables 2 and 3). Pimozide (dopaminergic antagonist) did not affect circulating LH levels 1 hr following administration, but did depress LH levels 2 hours after treatment in adult (Tables 2 and 3). Methysergide (serotonergic antagonist) administration depressed plasma LH concentrations in both young and adult chickens (Tables 2 and 3). These decreases, at 1 hr following methysergide injection, were 15.8% and 40.9% in, respectively, adult and young chickens. It may be noted that the plasma concentrations of LH were observed to be decreased 2 hr following the vehicle for phenoxybenzamine (Table 3). Similarly low
RESULTS
Data on the effects of drugs, which interfere with neurotransmitter synthesis on the circulating concentration of LH, are summarized in Tables 1, 2, and 3. The administration of inhibitors of amine synthesis (cw-mpt for DA/NE; DDC for NE; pCPA for 5HT) was followed in all cases by significant reductions in the plasma LH concentration (Tables 1 and 2). The maximal observed decreases in the LH levels were 48.7% in adults and 30.8% in young chicks with cY-mpt, 24.1% in adults and 62.3% in chicks with DDC and 51.8% in adults and 40.2% in chicks with pCPA. It may be noted that the effects of cu-mpt and DDC were observed in l-2 hr while those of pCPA were seen at 1 and 2 days. Similarly TABLE EFFECTS
OF AMINERGIC
Diethyldithiocarbamic Vehicle cY-Methyl-p-tyrosine Vehicle
p-Chlorophenylalanine Vehicle
1
SYNTHESIS BLOCKERS ON CIRCULATING IN ADULT MALE DOMESTIC FOWL
Treatment
163
FOWL
CONCENTRATIONS
OF
LH
Plasma LH (@ml F SEM (N) following treatment
acid
26.8 34.7 8.1 15.8
Time after treatment (hr) (1) (2) 25.8 + 2.8(8)* + 1.8(8)* + 3.5(8) 34.0 + 2.0(8) + 2.0(6)** & 2.2(6)
Time after treatment (days) (1) (2) 5.4 + 1.1(8)** 4.0 A 1.0(9)** 15.6 * 3.8(8) 15.8 & 3.2(7)
Note. Different from respective vehicle injected control. * P < 0.05; ** P < 0.01 by Student’s t test.
164
BUONOMO,
RABII,
AND
TABLE
2
SCANES
CUMULATIVE DATAON THE EFFECTOF NEUROTRANSMITTER SYNTHESIS AND CATECHOLAMINE GRANULE REUPTAKE INHIBITORSAND ANTAGONISTS ON THE PLASMA LH CONCENTRATION IN 6-WEEK-OLD AND ADULT MALE CHICKENS Treatment (Aminergic synthesis blockers) p-Chlorophenylalanine Vehicle a-Methyl-p-tyrosine Vehicle Diethyldithiocarbamic Vehicle
acid
+ SEM (N)
Adult male
48 48 1 1 1 1
8.2 + 1.0(26)*** 17.0 + 2.4(19) 8.1 + 2.0(6)** 15.8 rt 2.2(6) 26.8 z!z 1.8(8)* 34.7 k 3.5(8)
7.6 12.7 4.5 6.5 2.6 6.9
5.5 AI 0.7(5)* 15.6 k 3.4(5)
5.4 + 8.2 + 6.7 f. 15.0 +
19.2 24.7 13.7 20.4 31.9 35.8 16.8 19.5
4.6 5.8 2.2 3.4 8.9 8.0 3.9 6.6 7.3 8.0
(Catecholamine Granule Reuptake inhibitor) Reserpine 4 Vehicle 4 Reset-pine 24 Vehicle 24 (Antagonists) Pimozide Vehicle Phenoxybenzamine Vehicle Propranolol Vehicle Methysergide Vehicle Atropine Vehicle Note.
Plasma LH &ml
Time thr)
-
+ k 2 + k k + +
-
3.0(8) 5.9(6) 1.1(7)* 2.1(7) 4.4(8) 5.0(8) 3.5(6) 3.2(6)
Young male + f k f + +
0.7(22)** 1.4(24) 0.4(24)** 0.8(26) 0.2(16)** 1.2(14) 0.5(16)* 0.9(16) 0.6(8)** 2.6(6)
+ 1.4(19) 2 0.8(17) + 0.3(12)* + 0.4(11) + 1.4(18) + 1.2(19) I!I 0.4(21)** + 0.6(20) ?I 0.7 (19) + 1.2(18)
Different from respective vehicle injected control. * P < 0.05; ** P < 0.01; *** P < 0.001 by Student’s
t test.
circulating levels of LH were observed in 6-week old chicks treated with the vehicle for the phenoxybenzamine injections (Table 2). This vehicle was acidified saline. This may affect plasma LH concentrations in a nonspecific manner, possibly acting as a stress. DISCUSSION
The present data provide evidence for catecholamine involvement in the control (presumably hypothalamic) of LH secretion in the male domestic fowl. Depletion of brain NE/DA, induced by either inhibiting synthesis or granular reuptake, reduced plasma LH concentrations. It may be concluded that NE is the major neurotransmitter involved, working via an cu-adrenergic receptor mechanism. This is based on
the ability of a NE synthesis blocker (DDC) and an cr-adrenergic antagonist (phenoxybenzamine) to reduce circulating LH concentrations. This is similar to the proposed ar-adrenergic role for NE in the hypothalamic control of LH in mammals (reviewed Weiner and Ganong , 1978). The LH surge in the rat can be inhibited by catecholamine depletion (Drouva and Gallo, 1976; Kalra and McCann, 1974), and by a-adrenergic blockade (Gnodde and Schuiling, 1976), and can be provoked by amine precursors and cx-adrenergic agonists, overcoming the inhibition by NE synthesis blockers (Kalra et al., 1972; Kalra and McCann, 1973; Kalra and McCann, 1974). Data from the present study are in agreement with some observations made in
AMINES
TABLE EFFECT
OF ANTAGONISTS
165
AND LH IN THE FOWL 3
TO NEUROTRANSMITTERS ON CIRCULATING IN ADULT MALE DOMESTIC FOWL
CONCENTRATIONS
OF
LH
Plasma LH r&ml + SEM (N) following treatment Treatment Pimozide Vehicle Phenoxybenzamine Vehicle Propanolol Vehicle Methysergide Vehicle
Time in hours
(0) 22.6 25.7 24.1 25.3 32.3 32.2 25.2 19.0
+ 2.5(8) k 2.4(6) + 3.0(7) k 2.1(7) + 3.2(8) I!Z5.0(8) * 4.8(7) k 3.3(6)
(1) 19.2 24.7 13.7 20.4 31.9 35.8 16.8 19.5
+ 2 * 2 + 2 k k
(2)
3.0(8) 5.9(6) 1.1(7)$,* 2.1(7) 4.4(8) 5.0(8) 3.5(6)$ 3.2(6)
15.6 24.2 12.1 14.1 34.6 27.0 15.8 18.0
+ + + + + k f. +
1.8(8)* 4.3(6) 1.8(7)$ 1.8(7)t 4.4(8) 2.5(8) 1.3(7)t 2.8(6)
Note. Different from pretreatment. t P < 0.05; $ P < 0.01 - paired t test. Different from vehicle injected control. * P < 0.05 by Student’s t test.
the female bird. For instance, a-adrenergic antagonists inhibit ovulation in the hen (Ferrando and Nalbandov, 1969; Kao and Nalbandov, 1972). Furthermore, reserpine administration has been reported to depress circulating LH concentration in adult female chickens, as well as in adult males and castrated males (Sharp, 1975). In the Japanese quail, the photoperiodically induced increase in LH can be ablated by resex-pine pretreatment (Follett et al., 1977), while that of testis weight is blocked by a-mpt (El Halawani et al., 1978). The present study also provides some evidence of serotonin exerting a positive role in the control of LH secretion in the domestic fowl. An inhibition of 5HT synthesis (by pCPA) or receptor blockade (by methysergide) was accompanied by low plasma LH levels. This is in contrast to the inhibitory role of 5HT in photostimulated gonadal growth in birds. El Halawani and his colleagues (1978) determined that if 5HT synthesis was inhibited in Japanese quail by pCPA administration, photoperiodically induced testicular growth was enhanced. Conversely if 5HT synthesis is enhanced following 5-hydroxytryptophan injection, photoperiodically induced testicular growth was reduced. These effects were presum-
ably mediated secretion.
by changes in gonadotropin
ACKNOWLEDGMENT These studies were supported by the New Jersey State Experimental Station and Rutgers University Bureau of Biological Research.
REFERENCES Davies, D. T., and Follett, B. K. (1974). The effect of intraventricular lidministration of 6 hydroxydopamine on photo-induced testicular growth in the Japanese quail. J. Endocrinol. 60,277-283. Drouva, S., and Gallo, R. V. (1976). Catecholamine involvement of enisodic LH release in adult ovariectomized rat;. Endocrinology 99, 65 I - 658. El Halawani, M. E., and Burke, W. H. (1975). Role of catecholamines in photoperiodically-induced gonadal development in Coturnix quail. Biol. Reprod. 13, 603-609. El Halawani, M. E., Burke, W. H., and Ogren, L. A. (1978). Effects of drugs that modify brain monoamine concentration on photoperiodicallyinduced testicular growth in Coturnix quail. Biol. Reprod. 18, 198-203. Ferrando, G., and Nalbandov, A. (1969). Direct effect on the ovary of the adrenergic blocking drug, Dibenzyline. Endocrinology 85, 38-42. Follett, B. K., Davies, D. T., and Gledhill, G. (1977). Photoperiodic control of reproduction in Japanese quail: Changes in gonadotropin secretion on the first day of induction and their pharmacological blockade. J. Endocrinol. 74, 449-460. Follett, B. K., Scanes, C. G., and Cunningham, F. J.
BUONOMO,
166
RAW,
(1972). A radioimmunoassay for avian luteinizing hormone. J. Endocrinol. 52, 359-378. Gallo, R. V., and Moberg, G. P. (1977). Serotonin mediated inhibition of episodic luteinizing hormone release during electrical stimulation of the arcuate nucleus in ovariectomized rats. Endocrinology
100, 945- 954.
Gnodde, H.P., and Schiuling, G. A. (1976). Involvement of catecholaminergic and cholinergic mechanisms in the pulsatile release of LH in the longterm ovariectomized rat. Neuroendocrinology 20, 212-223. Jackson, G. L. (1977). Effect of adrenergic blocking drugs on the secretion of luteinizing hormone in the ovariectomized ewe. Biol. Reprod. 16, 543-548. Kalra, P. S., Kalra, S. P., Krulich, L., Fawcett, C. P., and McCann, S. M. (1972). Involvement of norepinephrine in the transmission of the stimulatory influence of progesterone on gonadotropin release. Endocrinology 90, 1168- 1176. Kalra, S. P., and McCann, S. M. (1973). Effect of drugs modifying catecholamine synthesis on LH release induced by preoptic stimulation in the rat. Endocrinology
93, 356-
362.
Kalra, S. P., and McCann, S. M. (1974). Effects of drugs modifying catecholamine synthesis on plasma LH and ovulation in the rat. Neuroendocrinology
15, 79- 91.
Kamberi, I. A., Mical, R. S., and Porter, J. C. (1970). Effect of anterior pituitary perfusion and intraventricular injection of catecholamines and indolamines on LH release. Endocrinology 87, 1-12. Kao, L. W. L., and Nalbandov, A. (1972). The effect
AND
SCANES
of antiadrenergic
drugs on ovulation in hens. En1349. Porter, J. C., Mica& R. S., and Cramer, 0. M. (1971/ 1972). Effect of serotonin and other indoles on the release of luteinizing hormone follicle stimulating hormone and prolactin. Gynecol. Invest. 2, 13-22. Sawyer, C. H. (1952). Stimulation of ovulation in the rabbit by the intraventricular injection of epinephtine or norepinephrine. Anat. Record 112, 358. Sawyer, C. H. (1979). The Seventh Stevenson Lecture: Brain amines and pituitary gonadotropin secretion. Canad. J. Physiol. Pharmacol. 57, 667-680. Sawyer, C. H., Hillard, J., Kanematus, S., Scaramuzzi, R., and Blake, C. A. (1974). Effects of intraventricular infusions of norepinephrine and dopamine on LH release and ovulation in the rabbit. Neuroendocrinology 15, 328-337. Sawyer, C. H., and Radford, H. M. (1978). Effects of intraventricular injections of norepinephrine on brain-pituitary-ovarian function in the rabbit. docrinology
Brain
Res.
90, 1343-
146, 83-93.
Sharp, P. J. (1975). The effect of reserpine on plasma LH concentrations in intact and gonadectomised domestic fowl. Brit. Poult. Sci. 16, 79-82. Weick, R. F. (1978). Acute effects of adrenergic receptor blocking drugs and neuroleptic agents on pulsatile discharges of LH in ovariectomized rats. Neuroendocrinology 26, 108- 117. Weiner, R. I., and Ganong, W. F. (1978). Role of brain monoamines and histamine in regulation of anterior pituitary secretion. Physiol. Rev. 58, 905-959.
AND
COMPARATIVE
Aminergic
ENDOCRINOLOGY
Involvement in the Control of Luteinizing Secretion in the Domestic Fowl
FRANCES C. BUONOMO,
Departmentof
45, 162- 166 (1981)
Physiology
JAMSHID
RABII,
and the Bureau of Biological Jersey, New Brunswick,
AND
COLIN
Research, Rutgers-The New Jersey 08903
G.
Hormone SCANES
State
University
of New
Accepted January 6, 1981 Neuropharmacologic agents have been used, in vivo, to investigate the possible involvement of the biogenic amines in the hypothalamic control of luteinizing hormone (LH) secretion in the domestic fowl. Inhibitors of norepinephrine (NE)/dopamine (DA) synthesis (for DA/NE a-methyl-p-tyrosine, cr-mpt; for NE diethyldithiocarbamic acid, DDC) and granule reuptake of catecholamines (reserpine) and the cr-adrenergic antagonist (phenoxybenzamine) induced reductions in the circulating concentrations of LH. The administration of p-chlorophenylalanine (an inhibitor of 5hydroxytryptamine (5HT) synthesis) and methysergide (a 5HT antagonist) also depressed plasma levels of LH. Neither /I-adrenergic (propran0101) nor cholinergic (atropine) blockers affected circulating LH levels. These data suggest the involvement of a catecholamine (probably acting via a-adrenergic receptors), together with some serotoninergic components in the hypothalamic control of LH in the chicken.
The involvement of putative neurotransmitters in the hypothalamic control of adenohypophyseal hormone release in mammals has been the subject of intense investigation (reviewed, e.g., Weiner and Ganong, 1978). There is strong evidence that the hypothalamic release of luteinizing hormone releasing hormone (LHRH), and hence LH is provoked by catecholamine(s), probably norepinephrine acting via areceptors (Weiner and Ganong, 1978). This is based on the intraventricular injection of neurotransmitters (Sawyer, 1952; Sawyer et al., 1974; Sawyer, 1979) and upon pharmacological studies using biogenic amine synthesis blockers (Drouva and Gallo, 1976; Kalra and McCann, 1974; Kalra et al., 1972) and agonists and antagonists to neurotransmitters (Sawyer and Radford, 1978; Weick, 1977). In addition, there is evidence for serotonin (5HT) having both positive and negative influences on the hypothalamic control of LH secretion (Gallo and Moberg, 1977; Kamberi et al., 1970; Porter et al., 1971/1972). In birds, there is some evidence for catecholamines having effects on reproductive
function (El Halawani and Burke, 1975; El Halawani et al., 1978), and circulating concentrations of LH (Follett et al., 1977; Davies and Follett, 1974). The present study was designed to provide comprehensive information on the possible role of the biogenic amines in LH secretion in the male domestic fowl. MATERIALS
Animals. Male domestic fowl (White Leghorn) of two ages (young: 6 week old, and adult), were used in these studies. All the birds were maintained on a long daylength (young 16L: 8D; adult 14L: IOD) with free access to food (a commercial diet) and water. Young birds were housed in group cages, whereas the adults were kept in individual cages. Blood samples were taken either by venipuncture from the brachial vein (adult birds), or by decapitation (6-week-old birds). Following centrifugation, plasma was stored at -20” prior to assay. Drugs. The following drugs were employed in this investigation: a-methyl-p-tyrosine methylester (cY-mpt) (Sigma; in saline: 250 mg/kg), diethyldithiocarbamic acid (DDC) (Sigma; in saline: 400 mg/kg), pimozide (McNeil Laboratories: in 2% tartaric acid; 2.5 mg/kg), phenoxybenzamine (Smith, Kline and French; in acid saline; 20 mg/kg), propranolol (Ayerst Laboratories, in saline, 2 mg/kg), atropine sulfate (Sigma; in saline: 10 mg/kg), p-chloropr-enylalanine methyl ester (pCPA)
162 00166480/81/100162-05$01.00/O Copyright All rights
@ 1981 by Academic Press, Inc. of reproduction in any form reserved.
AND METHODS
AMINES
AND
LH
IN THE
(Sigma; in acid saline: 250 mg/kg), methysergide (Sandoz Pharmaceuticals; in 20% ethanolic saline: 2.5 mgkg). All drugs were administered via the intraperitoneal route. Radioimmunoassay. The concentration of LH in the plasma samples was determined by homologous radioimmunoassay (RIA) (Follett et al., 1972). Samples were assayed in duplicate at each of, at least, two concentrations. All samples from a single experiment were assayed in a single RIA to eliminate interassay variance. Statistics. Differences between treatment groups and their respective control were determined by Student’s t test. Differences between pre- and posttreatment plasma LH concentrations were estimated by the paired t test.
reserpine (catecholamine granule reuptake inhibitor) depressed the circulating LH concentrations by 64.8% in adults and 55.3% in young chicks (Table 2). Receptor antagonists exerted variable effects on the circulating LH concentrations. In all cases, phenoxybenzamine (cw-adrenergic antagonist) administration was accompanied by a reduction in the plasma level of LH (Tables 2 and 3). In adult birds, this effect was also observed 30 min following injection (phenoxybenzamine 13.4 ? (n = 7) SEM 2.8, vehicle control 19.9 + (7) 1.1 @ml; P < 0.05). Neither propranolol (p-adrenergic antagonist), nor atropine (cholinergic antagonist) significantly affected circulating LH concentrations (Tables 2 and 3). Pimozide (dopaminergic antagonist) did not affect circulating LH levels 1 hr following administration, but did depress LH levels 2 hours after treatment in adult (Tables 2 and 3). Methysergide (serotonergic antagonist) administration depressed plasma LH concentrations in both young and adult chickens (Tables 2 and 3). These decreases, at 1 hr following methysergide injection, were 15.8% and 40.9% in, respectively, adult and young chickens. It may be noted that the plasma concentrations of LH were observed to be decreased 2 hr following the vehicle for phenoxybenzamine (Table 3). Similarly low
RESULTS
Data on the effects of drugs, which interfere with neurotransmitter synthesis on the circulating concentration of LH, are summarized in Tables 1, 2, and 3. The administration of inhibitors of amine synthesis (cw-mpt for DA/NE; DDC for NE; pCPA for 5HT) was followed in all cases by significant reductions in the plasma LH concentration (Tables 1 and 2). The maximal observed decreases in the LH levels were 48.7% in adults and 30.8% in young chicks with cY-mpt, 24.1% in adults and 62.3% in chicks with DDC and 51.8% in adults and 40.2% in chicks with pCPA. It may be noted that the effects of cu-mpt and DDC were observed in l-2 hr while those of pCPA were seen at 1 and 2 days. Similarly TABLE EFFECTS
OF AMINERGIC
Diethyldithiocarbamic Vehicle cY-Methyl-p-tyrosine Vehicle
p-Chlorophenylalanine Vehicle
1
SYNTHESIS BLOCKERS ON CIRCULATING IN ADULT MALE DOMESTIC FOWL
Treatment
163
FOWL
CONCENTRATIONS
OF
LH
Plasma LH (@ml F SEM (N) following treatment
acid
26.8 34.7 8.1 15.8
Time after treatment (hr) (1) (2) 25.8 + 2.8(8)* + 1.8(8)* + 3.5(8) 34.0 + 2.0(8) + 2.0(6)** & 2.2(6)
Time after treatment (days) (1) (2) 5.4 + 1.1(8)** 4.0 A 1.0(9)** 15.6 * 3.8(8) 15.8 & 3.2(7)
Note. Different from respective vehicle injected control. * P < 0.05; ** P < 0.01 by Student’s t test.
164
BUONOMO,
RABII,
AND
TABLE
2
SCANES
CUMULATIVE DATAON THE EFFECTOF NEUROTRANSMITTER SYNTHESIS AND CATECHOLAMINE GRANULE REUPTAKE INHIBITORSAND ANTAGONISTS ON THE PLASMA LH CONCENTRATION IN 6-WEEK-OLD AND ADULT MALE CHICKENS Treatment (Aminergic synthesis blockers) p-Chlorophenylalanine Vehicle a-Methyl-p-tyrosine Vehicle Diethyldithiocarbamic Vehicle
acid
+ SEM (N)
Adult male
48 48 1 1 1 1
8.2 + 1.0(26)*** 17.0 + 2.4(19) 8.1 + 2.0(6)** 15.8 rt 2.2(6) 26.8 z!z 1.8(8)* 34.7 k 3.5(8)
7.6 12.7 4.5 6.5 2.6 6.9
5.5 AI 0.7(5)* 15.6 k 3.4(5)
5.4 + 8.2 + 6.7 f. 15.0 +
19.2 24.7 13.7 20.4 31.9 35.8 16.8 19.5
4.6 5.8 2.2 3.4 8.9 8.0 3.9 6.6 7.3 8.0
(Catecholamine Granule Reuptake inhibitor) Reserpine 4 Vehicle 4 Reset-pine 24 Vehicle 24 (Antagonists) Pimozide Vehicle Phenoxybenzamine Vehicle Propranolol Vehicle Methysergide Vehicle Atropine Vehicle Note.
Plasma LH &ml
Time thr)
-
+ k 2 + k k + +
-
3.0(8) 5.9(6) 1.1(7)* 2.1(7) 4.4(8) 5.0(8) 3.5(6) 3.2(6)
Young male + f k f + +
0.7(22)** 1.4(24) 0.4(24)** 0.8(26) 0.2(16)** 1.2(14) 0.5(16)* 0.9(16) 0.6(8)** 2.6(6)
+ 1.4(19) 2 0.8(17) + 0.3(12)* + 0.4(11) + 1.4(18) + 1.2(19) I!I 0.4(21)** + 0.6(20) ?I 0.7 (19) + 1.2(18)
Different from respective vehicle injected control. * P < 0.05; ** P < 0.01; *** P < 0.001 by Student’s
t test.
circulating levels of LH were observed in 6-week old chicks treated with the vehicle for the phenoxybenzamine injections (Table 2). This vehicle was acidified saline. This may affect plasma LH concentrations in a nonspecific manner, possibly acting as a stress. DISCUSSION
The present data provide evidence for catecholamine involvement in the control (presumably hypothalamic) of LH secretion in the male domestic fowl. Depletion of brain NE/DA, induced by either inhibiting synthesis or granular reuptake, reduced plasma LH concentrations. It may be concluded that NE is the major neurotransmitter involved, working via an cu-adrenergic receptor mechanism. This is based on
the ability of a NE synthesis blocker (DDC) and an cr-adrenergic antagonist (phenoxybenzamine) to reduce circulating LH concentrations. This is similar to the proposed ar-adrenergic role for NE in the hypothalamic control of LH in mammals (reviewed Weiner and Ganong , 1978). The LH surge in the rat can be inhibited by catecholamine depletion (Drouva and Gallo, 1976; Kalra and McCann, 1974), and by a-adrenergic blockade (Gnodde and Schuiling, 1976), and can be provoked by amine precursors and cx-adrenergic agonists, overcoming the inhibition by NE synthesis blockers (Kalra et al., 1972; Kalra and McCann, 1973; Kalra and McCann, 1974). Data from the present study are in agreement with some observations made in
AMINES
TABLE EFFECT
OF ANTAGONISTS
165
AND LH IN THE FOWL 3
TO NEUROTRANSMITTERS ON CIRCULATING IN ADULT MALE DOMESTIC FOWL
CONCENTRATIONS
OF
LH
Plasma LH r&ml + SEM (N) following treatment Treatment Pimozide Vehicle Phenoxybenzamine Vehicle Propanolol Vehicle Methysergide Vehicle
Time in hours
(0) 22.6 25.7 24.1 25.3 32.3 32.2 25.2 19.0
+ 2.5(8) k 2.4(6) + 3.0(7) k 2.1(7) + 3.2(8) I!Z5.0(8) * 4.8(7) k 3.3(6)
(1) 19.2 24.7 13.7 20.4 31.9 35.8 16.8 19.5
+ 2 * 2 + 2 k k
(2)
3.0(8) 5.9(6) 1.1(7)$,* 2.1(7) 4.4(8) 5.0(8) 3.5(6)$ 3.2(6)
15.6 24.2 12.1 14.1 34.6 27.0 15.8 18.0
+ + + + + k f. +
1.8(8)* 4.3(6) 1.8(7)$ 1.8(7)t 4.4(8) 2.5(8) 1.3(7)t 2.8(6)
Note. Different from pretreatment. t P < 0.05; $ P < 0.01 - paired t test. Different from vehicle injected control. * P < 0.05 by Student’s t test.
the female bird. For instance, a-adrenergic antagonists inhibit ovulation in the hen (Ferrando and Nalbandov, 1969; Kao and Nalbandov, 1972). Furthermore, reserpine administration has been reported to depress circulating LH concentration in adult female chickens, as well as in adult males and castrated males (Sharp, 1975). In the Japanese quail, the photoperiodically induced increase in LH can be ablated by resex-pine pretreatment (Follett et al., 1977), while that of testis weight is blocked by a-mpt (El Halawani et al., 1978). The present study also provides some evidence of serotonin exerting a positive role in the control of LH secretion in the domestic fowl. An inhibition of 5HT synthesis (by pCPA) or receptor blockade (by methysergide) was accompanied by low plasma LH levels. This is in contrast to the inhibitory role of 5HT in photostimulated gonadal growth in birds. El Halawani and his colleagues (1978) determined that if 5HT synthesis was inhibited in Japanese quail by pCPA administration, photoperiodically induced testicular growth was enhanced. Conversely if 5HT synthesis is enhanced following 5-hydroxytryptophan injection, photoperiodically induced testicular growth was reduced. These effects were presum-
ably mediated secretion.
by changes in gonadotropin
ACKNOWLEDGMENT These studies were supported by the New Jersey State Experimental Station and Rutgers University Bureau of Biological Research.
REFERENCES Davies, D. T., and Follett, B. K. (1974). The effect of intraventricular lidministration of 6 hydroxydopamine on photo-induced testicular growth in the Japanese quail. J. Endocrinol. 60,277-283. Drouva, S., and Gallo, R. V. (1976). Catecholamine involvement of enisodic LH release in adult ovariectomized rat;. Endocrinology 99, 65 I - 658. El Halawani, M. E., and Burke, W. H. (1975). Role of catecholamines in photoperiodically-induced gonadal development in Coturnix quail. Biol. Reprod. 13, 603-609. El Halawani, M. E., Burke, W. H., and Ogren, L. A. (1978). Effects of drugs that modify brain monoamine concentration on photoperiodicallyinduced testicular growth in Coturnix quail. Biol. Reprod. 18, 198-203. Ferrando, G., and Nalbandov, A. (1969). Direct effect on the ovary of the adrenergic blocking drug, Dibenzyline. Endocrinology 85, 38-42. Follett, B. K., Davies, D. T., and Gledhill, G. (1977). Photoperiodic control of reproduction in Japanese quail: Changes in gonadotropin secretion on the first day of induction and their pharmacological blockade. J. Endocrinol. 74, 449-460. Follett, B. K., Scanes, C. G., and Cunningham, F. J.
BUONOMO,
166
RAW,
(1972). A radioimmunoassay for avian luteinizing hormone. J. Endocrinol. 52, 359-378. Gallo, R. V., and Moberg, G. P. (1977). Serotonin mediated inhibition of episodic luteinizing hormone release during electrical stimulation of the arcuate nucleus in ovariectomized rats. Endocrinology
100, 945- 954.
Gnodde, H.P., and Schiuling, G. A. (1976). Involvement of catecholaminergic and cholinergic mechanisms in the pulsatile release of LH in the longterm ovariectomized rat. Neuroendocrinology 20, 212-223. Jackson, G. L. (1977). Effect of adrenergic blocking drugs on the secretion of luteinizing hormone in the ovariectomized ewe. Biol. Reprod. 16, 543-548. Kalra, P. S., Kalra, S. P., Krulich, L., Fawcett, C. P., and McCann, S. M. (1972). Involvement of norepinephrine in the transmission of the stimulatory influence of progesterone on gonadotropin release. Endocrinology 90, 1168- 1176. Kalra, S. P., and McCann, S. M. (1973). Effect of drugs modifying catecholamine synthesis on LH release induced by preoptic stimulation in the rat. Endocrinology
93, 356-
362.
Kalra, S. P., and McCann, S. M. (1974). Effects of drugs modifying catecholamine synthesis on plasma LH and ovulation in the rat. Neuroendocrinology
15, 79- 91.
Kamberi, I. A., Mical, R. S., and Porter, J. C. (1970). Effect of anterior pituitary perfusion and intraventricular injection of catecholamines and indolamines on LH release. Endocrinology 87, 1-12. Kao, L. W. L., and Nalbandov, A. (1972). The effect
AND
SCANES
of antiadrenergic
drugs on ovulation in hens. En1349. Porter, J. C., Mica& R. S., and Cramer, 0. M. (1971/ 1972). Effect of serotonin and other indoles on the release of luteinizing hormone follicle stimulating hormone and prolactin. Gynecol. Invest. 2, 13-22. Sawyer, C. H. (1952). Stimulation of ovulation in the rabbit by the intraventricular injection of epinephtine or norepinephrine. Anat. Record 112, 358. Sawyer, C. H. (1979). The Seventh Stevenson Lecture: Brain amines and pituitary gonadotropin secretion. Canad. J. Physiol. Pharmacol. 57, 667-680. Sawyer, C. H., Hillard, J., Kanematus, S., Scaramuzzi, R., and Blake, C. A. (1974). Effects of intraventricular infusions of norepinephrine and dopamine on LH release and ovulation in the rabbit. Neuroendocrinology 15, 328-337. Sawyer, C. H., and Radford, H. M. (1978). Effects of intraventricular injections of norepinephrine on brain-pituitary-ovarian function in the rabbit. docrinology
Brain
Res.
90, 1343-
146, 83-93.
Sharp, P. J. (1975). The effect of reserpine on plasma LH concentrations in intact and gonadectomised domestic fowl. Brit. Poult. Sci. 16, 79-82. Weick, R. F. (1978). Acute effects of adrenergic receptor blocking drugs and neuroleptic agents on pulsatile discharges of LH in ovariectomized rats. Neuroendocrinology 26, 108- 117. Weiner, R. I., and Ganong, W. F. (1978). Role of brain monoamines and histamine in regulation of anterior pituitary secretion. Physiol. Rev. 58, 905-959.