- Email: [email protected]
Systematic and intraventricular prolactin induces excessive grooming
European Journal of Pharmacology, 65 ( 1 9 8 0 ) 4 5 7 - - 4 5 8
457
© E l s e v i e r / N o r t h - H o l l a n d B i o m e d i c a l Press
Rapid communication SYSTEMIC AND INTRAVENTRICULAR PROLACTIN INDUCES EXCESSIVE GROOMING
FILIPPO D R A G O , PIER LUIGI CANONICO, R O C C O BITETTI and U M B E R T O SCAPAGNINI
Department of Pharmacology, University of Catania Medical School, Catania, Italy Received 4 July 1980, accepted 8 July 1980
Morphine and peptides related to ACTH, MSH and LPH are known to induce excessive grooming in the rat when administered intraventricularly (Wiegant et al., 1977b). Moreover, striatal dopamine seems to be involved in ACTH-induced excessive grooming since haloperidol inhibits this effect when injected either systemically or in the neostriatum (Wiegant et al., 1977a). Prolactin (PRL), which is known to influence several types of behavior after systemic administration (Nicoll, 1974), may stimulate dopaminergic turnover in some brain areas, including the nigrostriatal system (Perkins and Westfall, 1978). For these reasons, the possible capacity of PRL to stimulate the display of grooming behavior in the rat was studied either during endogenously induced hyperprolactinaemia or after intraventricular injection of the hormone. Male rats of Wistar strain, weighing 180200 g, were used. Seven days prior to the experimental session, a number of rats received a pituitary homograft under the kidney capsule, whereas the control group received a smooth muscle graft following the same procedure. Another group of animals had a plastic cannula implanted into the brain ventricular system (foramen interventriculare, KSnig and Klippel, A6360). Grooming behavior was analysed as described by Wiegant et al. (1977b), using a 15th sec sampling technique, making possible a maximum score of 200 per 50 min observation session. Grafted animals were killed at the end of the experimental session and the plasma PRL
levels were measured with a RIA kit supplied by NIAMDD. The results are expressed in terms of ng/ml of plasma. The data, depicted in table 1, show that endogenous hyperprolactinaemia due to a pituitary homograft induced excessive grooming, and that this response was suppressed by systemic administration of haloperidol (0.5 mg/kg). The intraventricular injection of PRL (10/~g//~l/rat, 30 min prior to observation session) also induced excessive grooming which was inhibited by the systemic administration of haloperidol.
TABLE 1 P R L - i n d u c e d excessive g r o o m i n g a n d its i n h i b i t i o n b y systemic administration of haloperidol. Experimental conditions
Systemic treatment
Pituitary homograft I Pituitary homograft 2 S m o o t h m u s c l e graft 3 S m o o t h m u s c l e graft 4 I. v e n t r . P R L I. v e n t r . P R L I. ventr, saline I. v e n t r , saline
Saline Haloperidol Saline Haloperidol Saline Haloperidol Saline Haloperidol
7 7 7 7
n
Grooming score s
7 6 5 5 7 7 6 5
89 18 15 10 104 21 24 14
-+ 5 6 + 3 + 2 + 2 + 9 6 -+ 1 -+ 6 + 4
1 Plasma P R L level: 60 + 7 n g / m l . 2 Plasma P R L level: 89 -+ 8 n g / m l . 3 Plasma P R L level: 20 + 2 ng/ml. 4 Plasma P R L level: 48 + 7 n g / m l . s D a t a for g r o o m i n g score are m e a n s + S.E. 5 S i g n i f i c a n t l y h i g h e r t h a n c o n t r o l g r o u p ( P < 0.01 S t u d e n t ' s t-test). 7 0.5 mg/kg.
458
It is known that opiate-induced grooming behavior is dependent on an intact catecholaminergic central system, and that the dopaminergic terminals of the nucleus caudatus are indispensable for this effect (see: Cools et al., 1974). Moreover, the dopaminergic system projecting from the substantia nigra into the neostriatum is involved in ACTH-induced excessive grooming (Wiegant et al., 1977a). It is well established that PRL enhances dopamine turnover in the striatum through presynaptic modulation (Perkins and Westfall, 1978). It is reasonable, therefore, that the mechanism of PRL-induced excessive grooming should involve the dopaminergic system projecting into the neostriatum, namely the nigrostriatal system.
Acknowledgement The authors wish to thank S. Maugeri for technical assistance.
References Cools, A.R., H.J. Janssen and C.L.E. Broekkamp, 1974, The differential role of the caudate nucleus in the initiation and maintenance of morphineinduced behavior in rats, Arch. Int. Pharmacodyn. 210,163. Nicoll, C.S., 1974, Physiological actions of prolactin, in: Handbook of Physiology, Section 7: Endocrinology, Vol. IV, (American Physiological Society, Washington) p. 253. Perkins, N.A. and T.C. Westfall, 1978, The effect of prolactin on dopamine release from rat striatum and medial basal hypothalamus, Neurosci. 3, 59. Wiegant, V.M., A.R. Cools and W.H. Gispen, 1977a, ACTH-induced escessive grooming involves brain dopamine, European J. Pharmacol. 41,343. Wiegant, V.M., W.H. Gispen, L. Terenius and D. de Wied, 1977b, ACTH-like peptides and morphine: interaction at the level of the CNS, Psychoneuroend. 2, 63.
457
© E l s e v i e r / N o r t h - H o l l a n d B i o m e d i c a l Press
Rapid communication SYSTEMIC AND INTRAVENTRICULAR PROLACTIN INDUCES EXCESSIVE GROOMING
FILIPPO D R A G O , PIER LUIGI CANONICO, R O C C O BITETTI and U M B E R T O SCAPAGNINI
Department of Pharmacology, University of Catania Medical School, Catania, Italy Received 4 July 1980, accepted 8 July 1980
Morphine and peptides related to ACTH, MSH and LPH are known to induce excessive grooming in the rat when administered intraventricularly (Wiegant et al., 1977b). Moreover, striatal dopamine seems to be involved in ACTH-induced excessive grooming since haloperidol inhibits this effect when injected either systemically or in the neostriatum (Wiegant et al., 1977a). Prolactin (PRL), which is known to influence several types of behavior after systemic administration (Nicoll, 1974), may stimulate dopaminergic turnover in some brain areas, including the nigrostriatal system (Perkins and Westfall, 1978). For these reasons, the possible capacity of PRL to stimulate the display of grooming behavior in the rat was studied either during endogenously induced hyperprolactinaemia or after intraventricular injection of the hormone. Male rats of Wistar strain, weighing 180200 g, were used. Seven days prior to the experimental session, a number of rats received a pituitary homograft under the kidney capsule, whereas the control group received a smooth muscle graft following the same procedure. Another group of animals had a plastic cannula implanted into the brain ventricular system (foramen interventriculare, KSnig and Klippel, A6360). Grooming behavior was analysed as described by Wiegant et al. (1977b), using a 15th sec sampling technique, making possible a maximum score of 200 per 50 min observation session. Grafted animals were killed at the end of the experimental session and the plasma PRL
levels were measured with a RIA kit supplied by NIAMDD. The results are expressed in terms of ng/ml of plasma. The data, depicted in table 1, show that endogenous hyperprolactinaemia due to a pituitary homograft induced excessive grooming, and that this response was suppressed by systemic administration of haloperidol (0.5 mg/kg). The intraventricular injection of PRL (10/~g//~l/rat, 30 min prior to observation session) also induced excessive grooming which was inhibited by the systemic administration of haloperidol.
TABLE 1 P R L - i n d u c e d excessive g r o o m i n g a n d its i n h i b i t i o n b y systemic administration of haloperidol. Experimental conditions
Systemic treatment
Pituitary homograft I Pituitary homograft 2 S m o o t h m u s c l e graft 3 S m o o t h m u s c l e graft 4 I. v e n t r . P R L I. v e n t r . P R L I. ventr, saline I. v e n t r , saline
Saline Haloperidol Saline Haloperidol Saline Haloperidol Saline Haloperidol
7 7 7 7
n
Grooming score s
7 6 5 5 7 7 6 5
89 18 15 10 104 21 24 14
-+ 5 6 + 3 + 2 + 2 + 9 6 -+ 1 -+ 6 + 4
1 Plasma P R L level: 60 + 7 n g / m l . 2 Plasma P R L level: 89 -+ 8 n g / m l . 3 Plasma P R L level: 20 + 2 ng/ml. 4 Plasma P R L level: 48 + 7 n g / m l . s D a t a for g r o o m i n g score are m e a n s + S.E. 5 S i g n i f i c a n t l y h i g h e r t h a n c o n t r o l g r o u p ( P < 0.01 S t u d e n t ' s t-test). 7 0.5 mg/kg.
458
It is known that opiate-induced grooming behavior is dependent on an intact catecholaminergic central system, and that the dopaminergic terminals of the nucleus caudatus are indispensable for this effect (see: Cools et al., 1974). Moreover, the dopaminergic system projecting from the substantia nigra into the neostriatum is involved in ACTH-induced excessive grooming (Wiegant et al., 1977a). It is well established that PRL enhances dopamine turnover in the striatum through presynaptic modulation (Perkins and Westfall, 1978). It is reasonable, therefore, that the mechanism of PRL-induced excessive grooming should involve the dopaminergic system projecting into the neostriatum, namely the nigrostriatal system.
Acknowledgement The authors wish to thank S. Maugeri for technical assistance.
References Cools, A.R., H.J. Janssen and C.L.E. Broekkamp, 1974, The differential role of the caudate nucleus in the initiation and maintenance of morphineinduced behavior in rats, Arch. Int. Pharmacodyn. 210,163. Nicoll, C.S., 1974, Physiological actions of prolactin, in: Handbook of Physiology, Section 7: Endocrinology, Vol. IV, (American Physiological Society, Washington) p. 253. Perkins, N.A. and T.C. Westfall, 1978, The effect of prolactin on dopamine release from rat striatum and medial basal hypothalamus, Neurosci. 3, 59. Wiegant, V.M., A.R. Cools and W.H. Gispen, 1977a, ACTH-induced escessive grooming involves brain dopamine, European J. Pharmacol. 41,343. Wiegant, V.M., W.H. Gispen, L. Terenius and D. de Wied, 1977b, ACTH-like peptides and morphine: interaction at the level of the CNS, Psychoneuroend. 2, 63.