- Email: [email protected]
The effect of cholinergic blockade on the growth hormone response to galanin in humans
The Effect of Cholinergic V.K.K.
Chatterjee,
Blockade on the Growth Hormone Response to Galanin in Humans
J.A. Ball, T.M.E.
Davis, C. Proby, J.M.
Burrin, and S.R. Bloom
The effect of cholinergic blockade with pirenrepine or atropine on growth hormone (GH) release after galanin administration was investigated in five normal male subjects. The mean peak GH response to an infusion of galanin (4.0 pmol/kg/min for 40 minutes) was significantly reduced from 17.2 mU/L to 2.9 mU/L (P < DO1 1with prior administration of pirenzepine (30 mg IV). When galanin was infused at a higher dose (80 pmollkglmin), this suppression of release by pirenzepine was partially overcome, with GH rising to a mean peak response of 8.0 mU/L (P < .05). Repeated administration of atropine (two bolus doses of 0.6 mg IV) also failed to abolish the GH response to this higher dose of galanin in two subjects. It has been proposed that cholinergic pathways control GH release via somatostatin, and this study suggests that galanin may also act by modulating hypothalamic somatostatinergic tone either directly or by facilitating cholinergic transmission. B 1988 by Grune & Stratton,
Inc.
G from porcine intestine.’
ALANIN is a 29-amino-acid neuropeptide first isolated Galanin immunoreactivity has been demonstrated subsequently in other species including human.? and shown to be widely distributed in other tissues such as the pancreas3 and the central nervous system.4 In the mammalian central nervous system, high concentrations of galanin have been found in the median eminence and hypothalamus, and specific galanin receptor sites have been identified and characterized there, supporting a role for galanin in the control of hypothalamic function.’ Galanin infusions in humans produce a significant rise in serum growth hormone (GH) and delay the clearance of an intravenous (IV) glucose load.6 Coadministration of galanin with a maximal stimulatory dose of growth hormone releasing hormone (GHRH) enhances the ensuing GH response more than threefold in a synergistic, rather than additive, manner.’ It therefore seems unlikely that galanin acts only through the release of endogenous GHRH. Thus, endogenous hypothalamic galanin may be an important factor in the regulation of GH release in humans, although the mechanism remains to be elucidated. There is considerable evidence that the cholinergic system plays a modulatory role in the secretion of GH, and anticholinergic agents such as atropine and pirenzepine are known to block the GH response to various provocative stimuli including GHRH,’ L-dopa, apomorphine, arginine, clonidine, and exercise.9Z’0There is extensive overlap of galaninlike immunoreactivity and choline acetyltransferaselike immunoreactivity in septal cell bodies and hippocampal fibers in the rat,” suggesting an involvement of galanin in cholinergic neurotransmission. More recently, galanin has been shown to inhibit acetylcholine release in the ventral hippocampus of the rat.12 We have, therefore, investigated the interaction of galanin with two cholinergic antagonists, atropine and pirenzepine, on GH release in normal humans. MATERIALS
(2) A bolus injection of pirenzepine (Boots, Nottingham, UK) 30 mg IV at -5 minutes followed by an infusion of galanin at 40 pmol/ kg/min from 0 to 40 minutes (Gal 40 + Pir). (3) A bolus injection of pirenzepine 30 mg IV at -5 minutes followed by an infusion of galanin at a higher dose of 80 pmol/kg/min from 0 to 40 minutes (Gal 80 + Pir). Two of the subjects, selected at random, had a further test as follows: A bolus dose of atropine 0.6 mg IV at - 5 minutes followed by an infusion of galanin at 80 pmol/kg/min at 0 minute. A second IV bolus of atropine 0.6 mg was administered at + 15 minutes, and the galanin infusion was discontinued at 40 minutes. On each occasion subjects were recumbent throughout, with indwelling cannulae inserted into an antecubital vein in each arm, one for sampling and bolus injections, the other for continuous infusion. Sterile endotoxin-free synthetic porcine galanin (Institut Armand Frappier, Lava], Quebec), was reconstituted in 1.5 mL of the subject’s own heparinized plasma containing 5,000 U aprotinin dissolved in normal saline (150 mmoI/L) and administered as a constant infusion via a syringe pump. Blood samples were taken for GH assay at ten-minute intervals from -20 to 70 minutes. Serum GH was measured with a specific double-antibody radioimmunoassay by an automated system (Kemtek, Burgess Hill, Sussex, UK), using the World Health Organization International Reference preparation of GH (66/217 350 mU = 175 fig) as standard.” The within-assay and between-assay coefficients of variation were 6.0% and 8.0%, respectively, and the detection limit was 1 mu/L. The GH secretory responses are expressed as mean * SEM absolute values (mu/L). Statistical analysis of the data was carried out by one- or two-way ANOVA.
RESULTS
The galanin infusion was well tolerated by all subjects, and apart from a transient metallic taste in the mouth, no other effects were observed. Treatment with pirenzepine induced the expected anticholinergic side effects including a dry mouth and impairment of visual accommodation for a few
AND METHODS
Five healthy men, aged 24 to 31 years and of normal body weight (47 to 75 kg) were studied after giving prior informed consent. The study was approved by the Ethical Committee of the Royal Postgraduate Medical School. Each volunteer underwent three tests, in random order, on separate occasions, at 8 AM after an overnight ten-hour fast. The tests were as follows: (I) An IV infusion of galanin at a dose of 40 pmol/kg/min from 0 to 40 minutes (Gal 40). Metabolism, Vol 37, No 11 (November). 1988: pp 1089-1091
From the Deportment of Medicine, Hommersmith Hospital. London. Address reprint requests to S.R. Bloom, MD, Department of Medicine, Hammersmith Hospital, Du Cane Rd. London WI2 OHS, United Kingdom. o 1988 by Grune & Stratton, Inc. 0026-0495/88/371 l-001 6%03.00/O 1089
CHAll-ERJEE
1090
ET AL
12io3 82
6-
5 42-
.
-20
, 0
-
I
20
.
I
*
40
I
60
-
1 80
01 -40
.
1
-20
.
I
0
x
I
20
r
I
40
-
I
60
B
L 80
Time (mins)
Time (mins) Serum GH response to a 40-minute galanin infusion 40 Fig 1. pmol/kg/min with (+I or without (ml pirenzapina (Pir) pretraatmant (30 mg IV at -5 minutes). and to galanin SO pmol/kg/min and Pir (0). lP < .05. l*P < .Ol, and l ** P < .OOl, compared with Gal 40 + Pir.
hours. The side effects seen with atropine administration were similar but of longer duration. Figure 1 summarizes the GH response to infusions of galanin with or without pretreatment with pirenzepine. A 40 pmol/kg/min galanin infusion induced a significant and uniform rise in serum GH in all subjects starting at 30 minutes and reaching a peak of 17.2 t 1.2 mU/L at 50 minutes. Pretreatment with pirenzepine abolished this response almost completely with a maximal GH response of 2.9 + 1.1 mU/L at 50 minutes (P< .OOl v Gal 40 alone). When galanin was infused at the higher dose of 80 pmol/kg/min, this blockade of galanin-induced GH release by pirenzepine was overcome, and the GH response to galanin was partially restored with a peak value of 8.0 + 1.6 mU/L at 50 minutes (P c .OSv Gal 40 + Pir). This peak value was still significantly lower (P < .OS) than the GH response seen with galanin infusion alone at 40 pmol/ kg/min. In two subjects, pretreatment with atropine also failed to abolish the GH response to galanin infusion at 80 pmol/ kg/min, with a significant rise from 1.8 mU/L at 0 minute to a peak of 12.8 mU/L at 40 minutes in one subject and from 2.9 mU/L at 0 minute to 9.4 mU/L at 50 minutes in the other subject (P < .05 v GH values at 0 minute). Individual data from this study are shown in Fig 2. DISCUSSION
The production of GH from the pituitary is controlled by the stimulatory action of hypothalamic GHRH on the one hand, and the inhibitory influence of somatostatin (SRIF) on the other. Previous studies have shown that galanin enhances the GH response to a supramaximal dose of GHRH,’ and it therefore seems unlikely that galanin acts only through the release of endogenous GHRH. In vitro, galanin has been reported to have no direct effect on GH release from rat pituitary cells, although intracerebroventricular administra-
GH responses in two subjects to an infusion of galanin Fig 2. (SO pmol/kg/min) with 0.6 mg of atropina (Atr) IV at -5 minutes and + 15 minutes. l P c; .05 Y GH value at 0 minute.
tion evokes GH secretionI These findings suggest the possibility that galanin may act indirectly on the somatotroph. Thus, one hypothesis is that it may lower endogenous somatostatinergic tone by inhibiting the secretion of SRIF presynaptically, as it does dopamine in the median eminence” or acetylcholine in the hippocampus,12 and thus elicit GH release by allowing the unopposed action of GHRH. Anticholinergic drugs abolish the GH response to exogenous GHRH,’ suggesting that cholinergic pathways do not modulate GH secretion via hypothalamic release of GHRH. In vitro experiments in rats have shown that muscarinic blockade has no effect on GHRH-induced GH release from pituitary cells.16 Depletion of hypothalamic SRIF by anterolateral deafferentation or a 40% to 60% reduction in SRIF levels caused by cysteamine treatment reverses the ability of atropine to block GHRH-induced GH release.17 Thus, it is hypothesized that acetylcholine may act by inhibiting hypothalamic SRIF release. In the present study, cholinergic blockade with pirenzepine is able to abolish the GH response to an infusion of galanin at low dose. However, higher doses of galanin are able to partially overcome this blockade. The GH response to a high-dose infusion of galanin is also not abolished by repeated administration of atropine. It is interesting that the GH response to insulin-induced hypoglycemia is also only partially blocked by cholinergic blockade,18 so it is tempting to speculate that endogenous hypothalamic galanin could be involved in this effect. A possible mechanism to account for these findings is that galanin and acetylcholine both act to decrease the tonic inhibition of GH release by hypothalamic SRIF. Alternatively, galanin may act to facilitate cholinergic transmission. Previous studies have shown that increased cholinergic tone induced by pyridostigmine increases basal plasma GH levels and potentiates the GH response to GHRH.‘9*20 Studies involving coadministration of galanin with pyridostigmine may thus help to resolve the role of galanin in modulation of cholinergic tone.
MODULATION
OF GH RESPONSE TO GALANIN
The use of galanin to enhance somatotroph responsiveness to GHRH, particularly in the context of growth failure or to overcome feedback inhibition, as has been shown with pyridostigmine,‘9~20 may lead to a useful diagnostic or therapeutic role for this peptide, particularly as it does not have the side
effects associated with drugs that facilitate cholinergic transmission.
ACKNOWLEDGMENT
wish to thank Dr J.P. Dickinson of Sanofi and D.P. Adamson of Boots for the supply of reagents. We
REFERENCES
Tatemoto K, Rokaeus A, Jornvall H, et al: Galanin: A novel biologically active peptide from porcine intestine. FEBS Lett 164:124-128, 1983 2. Bauer FE, Adrian TE, Christofides ND, et al: Distribution and molecular heterogeneity of galanin in human, pig, guinea pig and rat gastrointestinal tracts. Gastroenterology 91:877-883, 1986 3. Dunning BE, Ahren B, Veith RC, et al: Galanin: A novel pancreatic neuropeptide. Am J Physiol251:14:E127-E133, 1986 4. Melander T, Hokfelt T, Rokaeus A: Distribution of galaninlike immunoreactivity in the rat central nervous system. J Comp Neural 248:475-5 17, 1984 5. Servin AL, Amiranoff B, Rouyer-Fessard C, et al: Identification and molecular characterisation of gatanin receptor sites in rat brain. Biochem Biophys Res Commun 144:298-306, 1987 6. Bauer FE. Ginsberg L, Venetikou M, et al: Growth hormone release in man by galanin, a novel hypothalamic peptide. Lancet 2:192-195, 1986 7. Davis TME, Burrin JM, Bloom SR: Growth hormone release by GHRH in man is threefold enhanced by galanin. J Clin Endocrinol Metab65:1248-1252, 1987 8. Massara F, Ghigo E, Goffi S, et al: Blockade of hp-GRF 40 induced GH release in normal men by a cholinergic muscarinic antagonist. J Clin Endocrinol Metab 59: 1025- 1026, 1984 9. Casanueva FF. Villanueva L, Cabranes JA, et al: Cholinergic 1.
1091
mediation of GH secretion elicited by arginine, clonidine and physical exercise. J Clin Endocrinol Metab 59:526-530, 1984 10. Delitala G, Maioli M, Pacificio A, et al: Cholinergic receptor control mechanisms for L-Dopa, apomorphine and clonidine induced GH secretion in man. J Clin Endocrinol Metab 57: 1145-1149, 1983 1 I. Melander T, Staines WA, Rokaeus A: Galanin-like immunoreactivity in hippocampal afferents in the rat, with special reference to cholinergic and noradrenergic inputs. Neuroscience 19:223240, 1986 12. Fisone G, Chun F, Consolo S, et al: Galanin inhibits acetylcholine release in the ventral hippocampus of the rat: Histochemical, autoradiographic in vivo and in vitro studies, Proc Nat1 Acad Sci USA 84:7339-7343, 1987 13. Burrin JM, Yeo TH, Roddis MJ, et al: DHSS Scientific and Technical Publications. London, Department of Health and Social Security, 1985 14. Ottlecz A, Samson WK, McCann SM: Galanin: Evidence for a hypothalamic site of action to release growth hormone. Peptides 7:51-53, 1986 15. Nordstrom 0, Melander T, Hokfelt T, et al: Evidence for an inhibitory effect of the peptide galanin on dopamine release from the rat median eminence. Neurosci Lett 73:21-26, 1987 16. Casanueva FF, Villanueva L. Dieguez C, et al: Atropine blockade of GHRH induced GH secretion in man is not exerted at pituitary level. J Clin Endocrinol Metab 62: 186- 191, 1986 17. Locatelli V, Torsello A, Redaelli M, et al: Cholinergic agonist and antagonist drugs modulate the GH response to GHRH in the rat: Evidence for mediation by SRIF. J Endocrinol 111:271-278, 1986 18. Evans PJ, Dieguez C, Foord S, et al: The effects of cholinergic blockade on the growth hormone and prolactin response to insulin hypoglycaemia. Clin Endocrinol22:733-737, 1985 19. Massara F, Ghigo E, Molinatti P, et al: Potentiation of cholinergic tone by pyridostigmine bromide reinstates and potentiates the GH responsiveness to intermittent administration of GHRH in man. Acta Endocrinol (Copenh) 113:12-16, 1986 20. Ghigo E, Mazza E, lmperiale E. et al: Enhancement of cholinergic tone by pyridostigmine promotes both basal and GHRH induced GH secretion in children of short stature. J Clin Endocrinol Metab 65:452-456, 1987
Chatterjee,
Blockade on the Growth Hormone Response to Galanin in Humans
J.A. Ball, T.M.E.
Davis, C. Proby, J.M.
Burrin, and S.R. Bloom
The effect of cholinergic blockade with pirenrepine or atropine on growth hormone (GH) release after galanin administration was investigated in five normal male subjects. The mean peak GH response to an infusion of galanin (4.0 pmol/kg/min for 40 minutes) was significantly reduced from 17.2 mU/L to 2.9 mU/L (P < DO1 1with prior administration of pirenzepine (30 mg IV). When galanin was infused at a higher dose (80 pmollkglmin), this suppression of release by pirenzepine was partially overcome, with GH rising to a mean peak response of 8.0 mU/L (P < .05). Repeated administration of atropine (two bolus doses of 0.6 mg IV) also failed to abolish the GH response to this higher dose of galanin in two subjects. It has been proposed that cholinergic pathways control GH release via somatostatin, and this study suggests that galanin may also act by modulating hypothalamic somatostatinergic tone either directly or by facilitating cholinergic transmission. B 1988 by Grune & Stratton,
Inc.
G from porcine intestine.’
ALANIN is a 29-amino-acid neuropeptide first isolated Galanin immunoreactivity has been demonstrated subsequently in other species including human.? and shown to be widely distributed in other tissues such as the pancreas3 and the central nervous system.4 In the mammalian central nervous system, high concentrations of galanin have been found in the median eminence and hypothalamus, and specific galanin receptor sites have been identified and characterized there, supporting a role for galanin in the control of hypothalamic function.’ Galanin infusions in humans produce a significant rise in serum growth hormone (GH) and delay the clearance of an intravenous (IV) glucose load.6 Coadministration of galanin with a maximal stimulatory dose of growth hormone releasing hormone (GHRH) enhances the ensuing GH response more than threefold in a synergistic, rather than additive, manner.’ It therefore seems unlikely that galanin acts only through the release of endogenous GHRH. Thus, endogenous hypothalamic galanin may be an important factor in the regulation of GH release in humans, although the mechanism remains to be elucidated. There is considerable evidence that the cholinergic system plays a modulatory role in the secretion of GH, and anticholinergic agents such as atropine and pirenzepine are known to block the GH response to various provocative stimuli including GHRH,’ L-dopa, apomorphine, arginine, clonidine, and exercise.9Z’0There is extensive overlap of galaninlike immunoreactivity and choline acetyltransferaselike immunoreactivity in septal cell bodies and hippocampal fibers in the rat,” suggesting an involvement of galanin in cholinergic neurotransmission. More recently, galanin has been shown to inhibit acetylcholine release in the ventral hippocampus of the rat.12 We have, therefore, investigated the interaction of galanin with two cholinergic antagonists, atropine and pirenzepine, on GH release in normal humans. MATERIALS
(2) A bolus injection of pirenzepine (Boots, Nottingham, UK) 30 mg IV at -5 minutes followed by an infusion of galanin at 40 pmol/ kg/min from 0 to 40 minutes (Gal 40 + Pir). (3) A bolus injection of pirenzepine 30 mg IV at -5 minutes followed by an infusion of galanin at a higher dose of 80 pmol/kg/min from 0 to 40 minutes (Gal 80 + Pir). Two of the subjects, selected at random, had a further test as follows: A bolus dose of atropine 0.6 mg IV at - 5 minutes followed by an infusion of galanin at 80 pmol/kg/min at 0 minute. A second IV bolus of atropine 0.6 mg was administered at + 15 minutes, and the galanin infusion was discontinued at 40 minutes. On each occasion subjects were recumbent throughout, with indwelling cannulae inserted into an antecubital vein in each arm, one for sampling and bolus injections, the other for continuous infusion. Sterile endotoxin-free synthetic porcine galanin (Institut Armand Frappier, Lava], Quebec), was reconstituted in 1.5 mL of the subject’s own heparinized plasma containing 5,000 U aprotinin dissolved in normal saline (150 mmoI/L) and administered as a constant infusion via a syringe pump. Blood samples were taken for GH assay at ten-minute intervals from -20 to 70 minutes. Serum GH was measured with a specific double-antibody radioimmunoassay by an automated system (Kemtek, Burgess Hill, Sussex, UK), using the World Health Organization International Reference preparation of GH (66/217 350 mU = 175 fig) as standard.” The within-assay and between-assay coefficients of variation were 6.0% and 8.0%, respectively, and the detection limit was 1 mu/L. The GH secretory responses are expressed as mean * SEM absolute values (mu/L). Statistical analysis of the data was carried out by one- or two-way ANOVA.
RESULTS
The galanin infusion was well tolerated by all subjects, and apart from a transient metallic taste in the mouth, no other effects were observed. Treatment with pirenzepine induced the expected anticholinergic side effects including a dry mouth and impairment of visual accommodation for a few
AND METHODS
Five healthy men, aged 24 to 31 years and of normal body weight (47 to 75 kg) were studied after giving prior informed consent. The study was approved by the Ethical Committee of the Royal Postgraduate Medical School. Each volunteer underwent three tests, in random order, on separate occasions, at 8 AM after an overnight ten-hour fast. The tests were as follows: (I) An IV infusion of galanin at a dose of 40 pmol/kg/min from 0 to 40 minutes (Gal 40). Metabolism, Vol 37, No 11 (November). 1988: pp 1089-1091
From the Deportment of Medicine, Hommersmith Hospital. London. Address reprint requests to S.R. Bloom, MD, Department of Medicine, Hammersmith Hospital, Du Cane Rd. London WI2 OHS, United Kingdom. o 1988 by Grune & Stratton, Inc. 0026-0495/88/371 l-001 6%03.00/O 1089
CHAll-ERJEE
1090
ET AL
12io3 82
6-
5 42-
.
-20
, 0
-
I
20
.
I
*
40
I
60
-
1 80
01 -40
.
1
-20
.
I
0
x
I
20
r
I
40
-
I
60
B
L 80
Time (mins)
Time (mins) Serum GH response to a 40-minute galanin infusion 40 Fig 1. pmol/kg/min with (+I or without (ml pirenzapina (Pir) pretraatmant (30 mg IV at -5 minutes). and to galanin SO pmol/kg/min and Pir (0). lP < .05. l*P < .Ol, and l ** P < .OOl, compared with Gal 40 + Pir.
hours. The side effects seen with atropine administration were similar but of longer duration. Figure 1 summarizes the GH response to infusions of galanin with or without pretreatment with pirenzepine. A 40 pmol/kg/min galanin infusion induced a significant and uniform rise in serum GH in all subjects starting at 30 minutes and reaching a peak of 17.2 t 1.2 mU/L at 50 minutes. Pretreatment with pirenzepine abolished this response almost completely with a maximal GH response of 2.9 + 1.1 mU/L at 50 minutes (P< .OOl v Gal 40 alone). When galanin was infused at the higher dose of 80 pmol/kg/min, this blockade of galanin-induced GH release by pirenzepine was overcome, and the GH response to galanin was partially restored with a peak value of 8.0 + 1.6 mU/L at 50 minutes (P c .OSv Gal 40 + Pir). This peak value was still significantly lower (P < .OS) than the GH response seen with galanin infusion alone at 40 pmol/ kg/min. In two subjects, pretreatment with atropine also failed to abolish the GH response to galanin infusion at 80 pmol/ kg/min, with a significant rise from 1.8 mU/L at 0 minute to a peak of 12.8 mU/L at 40 minutes in one subject and from 2.9 mU/L at 0 minute to 9.4 mU/L at 50 minutes in the other subject (P < .05 v GH values at 0 minute). Individual data from this study are shown in Fig 2. DISCUSSION
The production of GH from the pituitary is controlled by the stimulatory action of hypothalamic GHRH on the one hand, and the inhibitory influence of somatostatin (SRIF) on the other. Previous studies have shown that galanin enhances the GH response to a supramaximal dose of GHRH,’ and it therefore seems unlikely that galanin acts only through the release of endogenous GHRH. In vitro, galanin has been reported to have no direct effect on GH release from rat pituitary cells, although intracerebroventricular administra-
GH responses in two subjects to an infusion of galanin Fig 2. (SO pmol/kg/min) with 0.6 mg of atropina (Atr) IV at -5 minutes and + 15 minutes. l P c; .05 Y GH value at 0 minute.
tion evokes GH secretionI These findings suggest the possibility that galanin may act indirectly on the somatotroph. Thus, one hypothesis is that it may lower endogenous somatostatinergic tone by inhibiting the secretion of SRIF presynaptically, as it does dopamine in the median eminence” or acetylcholine in the hippocampus,12 and thus elicit GH release by allowing the unopposed action of GHRH. Anticholinergic drugs abolish the GH response to exogenous GHRH,’ suggesting that cholinergic pathways do not modulate GH secretion via hypothalamic release of GHRH. In vitro experiments in rats have shown that muscarinic blockade has no effect on GHRH-induced GH release from pituitary cells.16 Depletion of hypothalamic SRIF by anterolateral deafferentation or a 40% to 60% reduction in SRIF levels caused by cysteamine treatment reverses the ability of atropine to block GHRH-induced GH release.17 Thus, it is hypothesized that acetylcholine may act by inhibiting hypothalamic SRIF release. In the present study, cholinergic blockade with pirenzepine is able to abolish the GH response to an infusion of galanin at low dose. However, higher doses of galanin are able to partially overcome this blockade. The GH response to a high-dose infusion of galanin is also not abolished by repeated administration of atropine. It is interesting that the GH response to insulin-induced hypoglycemia is also only partially blocked by cholinergic blockade,18 so it is tempting to speculate that endogenous hypothalamic galanin could be involved in this effect. A possible mechanism to account for these findings is that galanin and acetylcholine both act to decrease the tonic inhibition of GH release by hypothalamic SRIF. Alternatively, galanin may act to facilitate cholinergic transmission. Previous studies have shown that increased cholinergic tone induced by pyridostigmine increases basal plasma GH levels and potentiates the GH response to GHRH.‘9*20 Studies involving coadministration of galanin with pyridostigmine may thus help to resolve the role of galanin in modulation of cholinergic tone.
MODULATION
OF GH RESPONSE TO GALANIN
The use of galanin to enhance somatotroph responsiveness to GHRH, particularly in the context of growth failure or to overcome feedback inhibition, as has been shown with pyridostigmine,‘9~20 may lead to a useful diagnostic or therapeutic role for this peptide, particularly as it does not have the side
effects associated with drugs that facilitate cholinergic transmission.
ACKNOWLEDGMENT
wish to thank Dr J.P. Dickinson of Sanofi and D.P. Adamson of Boots for the supply of reagents. We
REFERENCES
Tatemoto K, Rokaeus A, Jornvall H, et al: Galanin: A novel biologically active peptide from porcine intestine. FEBS Lett 164:124-128, 1983 2. Bauer FE, Adrian TE, Christofides ND, et al: Distribution and molecular heterogeneity of galanin in human, pig, guinea pig and rat gastrointestinal tracts. Gastroenterology 91:877-883, 1986 3. Dunning BE, Ahren B, Veith RC, et al: Galanin: A novel pancreatic neuropeptide. Am J Physiol251:14:E127-E133, 1986 4. Melander T, Hokfelt T, Rokaeus A: Distribution of galaninlike immunoreactivity in the rat central nervous system. J Comp Neural 248:475-5 17, 1984 5. Servin AL, Amiranoff B, Rouyer-Fessard C, et al: Identification and molecular characterisation of gatanin receptor sites in rat brain. Biochem Biophys Res Commun 144:298-306, 1987 6. Bauer FE. Ginsberg L, Venetikou M, et al: Growth hormone release in man by galanin, a novel hypothalamic peptide. Lancet 2:192-195, 1986 7. Davis TME, Burrin JM, Bloom SR: Growth hormone release by GHRH in man is threefold enhanced by galanin. J Clin Endocrinol Metab65:1248-1252, 1987 8. Massara F, Ghigo E, Goffi S, et al: Blockade of hp-GRF 40 induced GH release in normal men by a cholinergic muscarinic antagonist. J Clin Endocrinol Metab 59: 1025- 1026, 1984 9. Casanueva FF. Villanueva L, Cabranes JA, et al: Cholinergic 1.
1091
mediation of GH secretion elicited by arginine, clonidine and physical exercise. J Clin Endocrinol Metab 59:526-530, 1984 10. Delitala G, Maioli M, Pacificio A, et al: Cholinergic receptor control mechanisms for L-Dopa, apomorphine and clonidine induced GH secretion in man. J Clin Endocrinol Metab 57: 1145-1149, 1983 1 I. Melander T, Staines WA, Rokaeus A: Galanin-like immunoreactivity in hippocampal afferents in the rat, with special reference to cholinergic and noradrenergic inputs. Neuroscience 19:223240, 1986 12. Fisone G, Chun F, Consolo S, et al: Galanin inhibits acetylcholine release in the ventral hippocampus of the rat: Histochemical, autoradiographic in vivo and in vitro studies, Proc Nat1 Acad Sci USA 84:7339-7343, 1987 13. Burrin JM, Yeo TH, Roddis MJ, et al: DHSS Scientific and Technical Publications. London, Department of Health and Social Security, 1985 14. Ottlecz A, Samson WK, McCann SM: Galanin: Evidence for a hypothalamic site of action to release growth hormone. Peptides 7:51-53, 1986 15. Nordstrom 0, Melander T, Hokfelt T, et al: Evidence for an inhibitory effect of the peptide galanin on dopamine release from the rat median eminence. Neurosci Lett 73:21-26, 1987 16. Casanueva FF, Villanueva L. Dieguez C, et al: Atropine blockade of GHRH induced GH secretion in man is not exerted at pituitary level. J Clin Endocrinol Metab 62: 186- 191, 1986 17. Locatelli V, Torsello A, Redaelli M, et al: Cholinergic agonist and antagonist drugs modulate the GH response to GHRH in the rat: Evidence for mediation by SRIF. J Endocrinol 111:271-278, 1986 18. Evans PJ, Dieguez C, Foord S, et al: The effects of cholinergic blockade on the growth hormone and prolactin response to insulin hypoglycaemia. Clin Endocrinol22:733-737, 1985 19. Massara F, Ghigo E, Molinatti P, et al: Potentiation of cholinergic tone by pyridostigmine bromide reinstates and potentiates the GH responsiveness to intermittent administration of GHRH in man. Acta Endocrinol (Copenh) 113:12-16, 1986 20. Ghigo E, Mazza E, lmperiale E. et al: Enhancement of cholinergic tone by pyridostigmine promotes both basal and GHRH induced GH secretion in children of short stature. J Clin Endocrinol Metab 65:452-456, 1987