Breeding Physiology

Brain Neuropeptides in Regulation of Growth and Reproduction in Pigs

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Abstract

Br ain h orm on es exq uisitely r egu late the secr etion of ho rm ones s ecreted by th e p ituitary g lan d that affect gr owth, metabolism , and repr odu ction . Ox ytocin w as on e o f the firs t neur oen docrine hor mo nes is olated and ch aracterized in 1 955 . Cu rr ently, 5 0 neur opeptide ho rmo nes r ang in g f rom mo no amines to p oly peptides w ith > 5,000 mo lecular weigh t have been is olated and characterized . We fo cus on o ur recen t stud ies co ncern ing h orm ones aff ectin g g row th in yo un g p igs an d tho se th at reg ulate repr odu ction . Som atic gro wth in vertebr ates is tho ug ht to be depen dent on pituitar y gro wth ho rm one (G H) ; w ith ou t p itu itary GH p rod uctio n o r p er iph eral action, po stnatal gr owth is sev erely stunted . For exam ple, a deficiency in G H p ro ductio n or GH recep tor ( GHR) g en e h as been demon strated to stunt g row th. You ng pigs req uire GH pr od uction and secretio n f ro m the pituitar y gland fo r co ntinu ed gr owth ( nitro gen r etention ); hy po phy secto my ar rests gr ow th. G H rep lacem ent th er apy in hy po phy secto mized pigs cau ses s ign if icant gr owth b ut at less er rate than in sham o perated co ntr ols . GH is s ecr eted into th e per iph er al blo od in an pu ls atile pattern in yo ung p igs an d th is ep iso dic G H s ecretion w anes w ith m atu rity. Hy po phy seal stalk tr an sectio n elimin ates pu ls atile GH secretion but b asal GH s ecr etion in th es e anim als allo ws co ntinu ed gro wth at a less er rate than s een in con tro ls. Episod ic GH secr etion was ob liter ated by hyp othalamic deaf fer entation in y oun g p ig s. In tr avenou s injectio n o f the br ain p eptide, GH- releasin g ho rm one (G HRH), stim ulates p eak release of G H s ecr etion in hy po phy seal stalk- tr ans ected pigs similar to th at in sh am- op er ated con tro ls. Our recent exp er iments indicate that in tr avenou s injectio n o f a G H-s ecr etago gue caus es im med iate peak GH release, and co ad min istratio n o f GHRH and th e G H- secr etagog ue au gments G H r eleas e. I ntr acerebro ven tr icu lar in jection of th e G H- secretag ogu e cau ses a do se- dep en den t in cr eas e in GH release, wh er eas central ad minis tration of so matos tatin (S RIH ) sup press es peak GH release ind uced by th e GH- secretag ogu e. Neur opeptide Y and galanin caus e mo dest GH release co mpared w ith th e GH- secretag ogu e. Lu teinizin g hor mon e releas in g h orm on e ( LHRH) is a hy po thalam ic decapep tid e pro duced by a placode of LHRH neur ons th at is cr ucial fo r go nadotrop in (LH and fo llicle stim ulatin g hor mon e, FS H) release by th e p ituitary g lan d in th e pig . Neur osu rgical interv ention s as des cr ibed abo ve ob liter ate LHRH release th us in ter ferin g w ith epis od ic LH an d FS H secretio n r equ ir ed for continu ed repro du ctive fu nction in male an d f em ale pigs .

Keywords: ASL R1668

How to Cite:

Anderson, L. L., (2000) “Brain Neuropeptides in Regulation of Growth and Reproduction in Pigs”, Iowa State University Animal Industry Report 1(1).